> >
DESCRIPTION
Title of invention: CONTROLLER OF ELECTRO-OPTICAL DEVICE,
CONTROL METHOD OF ELECTRO-OPTICAL DEVICE, ELECTRO-OPTICAL
DEVICE, AND ELECTRONIC APPARATUS
Technical Field
[0001]
The present invention relates to a controller of an
electro-optical device, a control method of an
electro-optical device, an electro-optical device, and an
electronic apparatus.
Background Art
[0002]
An electrophoretic display device using microcapsules
is an example of a display device which displays an image.
In an active matrix type display device, a driving circuit
for driving a microcapsule is provided at each of the
intersections of a plurality of row electrodes extending in
a row direction and a plurality of column electrodes extending
in a column direction. When a voltage is applied to the row
electrode and the column electrode, a potential difference
is generated between an electrode provided in the driving
circuit and an electrode facing the electrode in the driving
2
1 K
t »
» »
circuit with a microcapsule interposed therebetween. When
the potential difference is generated between the electrodes
facing each other with a microcapsule interposed therebetween,
white and black particles in the microcapsule move according
to the electric field caused by the potential difference.
Since the distribution of white and black particles in each
microcapsule changes, the optical reflection property
changes to display an image.
[0003]
Meanwhile, in the electrophoretic display device, image
rewriting when changing a display by the active matrix method
may be performed over a plurality of frames. However, if the
rewriting starts on the full screen when performing the image
rewriting over a plurality of frames, new writing cannot be
performed until the writing ends. Accordingly, when adding
or removing an image, the next writing starts after the end
of the image writing. Since this takes time, there is a
problem in terms of operability.
In order to solve such a problem, a method of performing
the writing by performing pipeline processing in units of a
partial region has been proposed (refer to PTL 1) . According
to the method disclosed in PTL 1, an image is written in two
partial regions on the screen, which do not overlap each other,
at different timings. Accordingly, even if the writing of
a partial region where writing has started first is not
3
1 "•
> »
completed, the writing of the other partial region where
writing starts later can be started. As a result, it is
| possible to improve the display speed compared with that when
this method is not adopted.
Citation List
Patent Literature
[0004]
PTL 1: JP-A-2009-251615
Summary of Invention
Technical Problem
[0005]
In the method disclosed in PTL 1, however, if the partial
regions overlap each other partly, the writing of the partial
region where writing starts later should wait until the
writing of the partial region where writing has started first
ends. For this reason, it takes time until the display is
completed.
[0006]
The invention has - been made in view of the above
described circumstances, and one of the objects of the
invention is to improve the perceived display speed of an
electro-optical device which needs to perform voltage
application multiple times in order to change the gradation
4
i
» *
• >
of a pixel.
Solution to Problem
[0007]
In order to achieve the above object, a controller of
an electro-optical device according to the invention is an
electro-optical device which includes a display unit with a
plurality of pixels and in which a writing operation of
i
changing the pixel from first gradation to second gradation
and a writing operation of changing the pixel from the second
gradation to the first gradation are performed by an operation
of applying a voltage to the pixel multiple times. The
controller of an electro-optical device includes: a
number-of-times difference calculating section that
calculates a difference between the number of times of
application of a first voltage, which is applied to change
the pixel to the first gradation, and the number of times of
application of a second voltage, which is applied to change
the pixel to the second gradation; and a voltage control
section that applies the first voltage or the second voltage
to the pixel until the difference becomes a predetermined
value when the difference regarding the pixel is not the
predetermined value at a predetermined timing and that, when
changing a gradation of the pixel, starts a new operation of
applying a voltage to the pixel multiple times even in the
5
middle of the writing operation.
According to the invention, it is possible to improve
the perceived display speed of an electro-optical device
which needs to perform voltage application multiple times in
order to change the gradation of a pixel. |
[0008] !
In the controller described above, when the pixel has
the first gradation and the difference regarding the pixel
is not the predetermined value after the writing operation
ends, the voltage control section may apply the first voltage
to the pixel until the difference becomes the predetermined
value.
According to this configuration, when there is a
difference between the number of times of application of the
first voltage and the number of times of application of the
second voltage after the writing operation ends, the first
voltage is applied until the difference of the number of times
of application becomes a predetermined value. In this case,
since the difference between the number of times of
application of the first voltage and the number of times of
application of the second voltage does not become large,
deterioration of the pixel can be suppressed.
[0009]
In the controller described above, when the pixel has
the second gradation and the difference regarding the pixel
6
J *
» •
is not the predetermined value after the writing operation
ends, the voltage control section may apply the second voltage
to the pixel until the difference becomes the predetermined
i value.
i
According to this configuration, when there is a
difference between the number of times of application of the
first voltage and the number of times of application of the
second voltage after the writing operation ends, the second
voltage is applied until the difference of the number of times
of application becomes a predetermined value. In this case,
since the difference between the number of times of
application of the first voltage and the number of times of
application of the second voltage does not become large,
deterioration of the pixel can be suppressed.
[0010]
In the controller described above, when an absolute
value of the difference is equal to or larger than a threshold
value when a writing operation of setting the pixel to the
first gradation starts in the middle of a writing operation
of setting the pixel to the second gradation, the voltage
control section may apply the second voltage until the
difference becomes the predetermined value and then start
application of the first voltage.
According to this configuration, a new writing
operation is started after the difference between the number
7
I »
of times of application of the first voltage and the number
of times of application of the second voltage is set to the
predetermined value. Therefore, even if the new writing
operation is performed, the difference between the number of
times of application of the first voltage and the number of
times of application of the second voltage does not become
large. As a result, deterioration of the pixel can be
suppressed.
[0011]
In the controller described above, when an absolute
value of the difference is equal to or larger than a threshold
value when a writing operation of setting the pixel to the
second gradation starts in the middle of a writing operation
of setting the pixel to the first gradation, the voltage
control section may apply the first voltage until the
difference becomes the predetermined value and then start
application of the second voltage.
According to this configuration, a new writing
operation is started after the difference between the number
of times of application of the first voltage and the number
of times of application of the second voltage is set to the
predetermined value. Therefore, even if the new writing
operation is performed, the difference between the number of
times of application of the first voltage and the number of
times of application of the second voltage does not become
8
t *•
> *
large. As a result, deterioration of the pixel can be
suppressed.
[0012]
The controller described above may further include an
application number-of-times determining section that, when
changing the gradation of the pixel, determines the number
of times of application on the basis of the gradation of the
pixel before the change, the gradation of the pixel after the
change, and a table in which the number of times of application
of a voltage for gradation change from the gradation before
the change to the gradation after the change matches the
gradation before the change and the gradation after the
change.
According to this configuration, since the appropriate
number of times of voltage application is set on the basis
of the gradation of the pixel before gradation change and the
gradation of the pixel after gradation change, it is possible
to increase the pixel rewriting speed compared with a
configuration in which the number of times of voltage
application is made to be fixed.
[0013]
In the controller described above, the number of times
of application of the first voltage applied to change the
pixel to the first gradation may be different from the number
of times of application of the second voltage applied to
9
* *
change the pixel to the second gradation.
According to this configuration, compared with a
configuration in which the number of times of voltage
application is the same in the case of changing the pixel to
the first gradation and the case of changing the pixel to the
second gradation, the speed of change to either one of the
gradations can be increased.
[0014]
In addition, in order to achieve the above object, a
control method of an electro-optical device according to the
invention is a control method of an electro-optical device
which includes a display unit with a plurality of pixels and
in which a writing operation of changing the pixel from first
gradation to second gradation and a writing operation of
changing the pixel from the second gradation to the first
gradation are performed by an operation of applying a voltage
to the pixel multiple times. The control method of an
electro-optical device includes: a step of calculating a
difference between the number of times of application of a
first voltage, which is applied to change the pixel to the
first gradation, and the number of times of application of
a second voltage, which is applied to change the pixel to the
second gradation; and a step of applying the first voltage
or the second voltage to the pixel until the difference
becomes a predetermined value when the difference regarding
10
the pixel is not the predetermined value at a predetermined
timing and starting a new operation of applying a voltage to
the pixel multiple times even in the middle of the writing
operation when changing a gradation of the pixel.
According to the invention, it is possible to improve
the perceived display speed of an electro-optical device
which needs to perform voltage application multiple times in
order to change the gradation of a pixel.
[0015]
In order to achieve the above object, a controller of
an electro-optical device according to the invention is an
electro-optical device which includes a display unit with a
plurality of pixels and in which a writing operation of
changing the pixel from first gradation to second gradation
and a writing operation of changing the pixel from the second
gradation to the first gradation are performed by an operation
of applying a voltage to the pixel multiple times, the
electro-optical device comprising: a number-of-times
difference calculating section that calculates a difference
between the number of times of application of a first voltage,
which is applied to change the pixel to the first gradation,
and the number of times of application of a second voltage,
which is applied to change the pixel to the second gradation;
and a voltage control section that applies the first voltage
or the second voltage to the pixel until the difference
11
becomes a predetermined value when the difference regarding
the pixel is not the predetermined value at a predetermined
timing and that, when changing a gradation of the pixel,
starts a new operation of applying a voltage to the pixel
multiple times even in the middle of the writing operation.
According to the invention, it is possible to improve
the perceived display speed of an electro-optical device
which needs to perform voltage application multiple times in
order to change the gradation of a pixel.
[0016]
The invention may be concepted as an electronic
apparatus including the electro-optical device described
above, as well as the electro-optical device.
Brief Description of Drawings
[0017]
[Fig. 1] Fig. 1 is a view showing the hardware configuration
of a display device 1000 and an electro-optical device 1.
[Fig. 2] Fig. 2 is a view showing the cross section of a
display area 100.
[Fig. 3] Fig. 3 is a view showing an equivalent circuit of
a pixel 100.
[Fig. 4] Fig. 4 shows views for explaining the configuration
of a storage region.
[Fig. 5] Fig. 5 is a block diagram showing the configuration
12
i *
of a function realized by a controller 5.
dp
[Fig. 6] Fig. 6 is a view showing the minimum number of times
of voltage application required to change the gradation.
[Fig. 7] Fig. 7 is a flow chart showing the flow of processing
performed by a controller 5 in the first embodiment.
[Fig. 8] Fig. 8 is a flow chart showing the flow of processing
performed by the controller 5 in the first embodiment.
[Fig. 9] Fig. 9 is a flow chart showing the flow of processing
performed by the controller 5 in the first embodiment.
[Fig. 10] Fig. 10 is a flow chart showing the flow of
processing performed by the controller 5 in the first
embodiment.
[Fig. 11] Fig. 11 is a view for explaining an operation in
the first embodiment.
[Fig. 12] Fig. 12 is a view for explaining an operation in
the first embodiment.
[Fig. 13] Fig. 13 is a view for explaining an operation in
the first embodiment.
[Fig. 14] Fig. 14 is a flow chart showing the flow of
processing performed by a controller 5 in a second embodiment.
[Fig. 15] Fig. 15 is a flow chart showing the flow of
processing performed by the controller 5 in the second
embodiment.
[Fig. 16] Fig. 16 is a flow chart showing the flow of
processing performed by the controller 5 in the second
13
embodiment.
[Fig. 17] Fig. 17 is a view for explaining an operation in
the second embodiment.
[Fig. 18] Fig. 18 is a view for explaining an operation in
the second embodiment.
[Fig. 19] Fig. 19 is a view for explaining an operation in
the second embodiment.
[Fig. 20] Fig. 20 is a view for explaining an operation in
the second embodiment.
[Fig. 21] Fig. 21 is a view showing the appearance of an
electronic book reader 2000.
[Fig. 22] Fig. 22 is a flow chart showing the flow of
processing performed by a controller 5 in a modification
example.
[Fig. 23] Fig. 23 is a flow chart showing the flow of
processing performed by the controller 5 in the modification
example.
[Fig. 24] Fig. 24 is a flow chart showing the flow of
processing performed by the controller 5 in the modification
example.
[Fig. 25] Fig. 25 is a flow chart showing the flow of
processing performed by the controller in the modification
example.
Description of Embodiments
14
« »
[0018]
[First embodiment]
(Configuration of a first embodiment)
Fig. 1 is a block diagram showing the hardware
configuration of a display device 1000 according to an
embodiment of the invention. The display device 1000 is a
device which displays an image, and includes an
electrophoretic electro-optical device 1, a control unit 2,
a VRAM (Video Random Access Memory) 3, and a RAM 4 which is
an example of a storage unit. In addition, the
electro-optical device 1 includes a display unit 10 and a
controller 5.
[0019]
The control unit 2 is a microcomputer including a CPU
(Central Processing Unit), a ROM (Read Only Memory), a RAM,
and the like, and controls each unit of the display device
1000. In addition, the control unit 2 accesses the VRAM 3
to writes the image data, which shows an image displayed on
a display area 100, into the VRAM 3.
The controller 5 supplies various signals for
displaying an image in the display area 100 of the display
unit 10 to a scanning line driving circuit 130 and a data line
driving circuit 140 of the display unit 10. The controller
5 is equivalent to a control unit of the electro-optical
device 1. In addition, all of the control unit 2 and the
15
controller 5 may be defined as a controller of the
electro-optical device 1. Alternatively, all of the control
unit 2, the controller 5, the VRAM 3, and the RAM 4 may be
defined as a controller of the electro-optical device 1.
[0020]
The VRAM 3 is memory which stores the image data written
by the control unit 2. The VRAM 3 has a storage region (buffer)
for each of pixels 110 arrayed in m rows x n columns, which
will be described later. The image data includes pixel data
showing the gradation of each pixel 110. The pixel data
showing the gradation of one pixel 110 is stored in one storage
region, which corresponds to the pixel 110, in the VRAM 3.
The pixel data written in the VRAM 3 is read by the controller
5.
The RAM 4 stores various kinds of data used in order to
display an image on the display area 100. A remaining
number-of-times storage region B, a gradation value storage
region C, a number-of-times difference storage region D, and
a planned image storage region E are provided in the RAM 4.
Details of each storage region will be described later.
[0021]
In the display area 100, a plurality of scanning lines
112 are provided along the row (X) direction in Fig. 1, and
a plurality of data lines 114 are provided along the column
(Y) direction so as to be electrically insulated from the
16
t •
J A
scanning lines 112. In addition, the pixel 110 is provided
corresponding to the intersection between each scanning line
112 and each data line 114. Assuming for the sake of
j convenience that the number of rows of the scanning lines 112
is "m" and the number of columns of the data lines 114 is "n",
the pixels 110 are arrayed in a matrix (m rows x n columns)
to form the display area 100.
[0022]
Fig. 2 is a view showing the cross section of the display
area 100. The display area 100 is largely divided as shown
in Fig. 2, and is formed by a first substrate 101, an
electrophoretic layer 102, and a second substrate 103. The
first substrate 101 is a substrate in which a circuit layer
is formed on an insulating and flexible substrate 101a. In
the present embodiment, the substrate 101a is formed of
polycarbonate. In addition, a resin material which is light,
flexible, has elasticity and is insulative may also be used
for the substrate 101a without being limited to polycarbonate.
In addition, the substrate 101a may be formed of glass which
does not have flexibility. An adhesive layer 101b is provided
on the surface of the substrate 101a, and a circuit layer 101c
is laminated on the surface of the adhesive layer 101b.
The circuit layer 101c has a plurality of scanning lines
112 arrayed in the row direction and a plurality of data lines
114 arrayed in the column direction. In addition, the circuit
17
t *
layer 101c has a pixel electrode lOld corresponding to each
of the intersections between the scanning lines 112 and the
data lines 114.
[0023]
The electrophoretic layer 102 is formed by a binder 102b
and a plurality of microcapsules 102a fixed by the binder 102b,
and is formed on the pixel electrodes lOld. In addition, an
adhesive layer formed by an adhesive may be provided between
the microcapsules 102a and the pixel electrodes lOld.
[0024]
The binder 102b is not particularly limited as long as
it has a good affinity with the microcapsules 102a, excellent
adhesiveness to electrodes, and insulation properties. A
dispersion medium and electrophoretic particles are
contained in the microcapsule 102a. As materials which form
the microcapsules 102a, it is preferable to use flexible
materials, such as gum Arabic and gelatin based compounds and
urethane based compounds.
[0025]
As a dispersion medium, the following materials may be
used: water; alcohol solvents (for example, methanol, ethanol,
isopropanol, butanol, octanol and methyl cellosolve); esters
(for example, ethyl acetate and butyl acetate); ketones (for
example, acetone, methyl ethyl ketone, and methyl isobutyl 1
ketone); aliphatic hydrocarbons (for example, pentane,
18
< *
hexane, and octane); alicyclic hydrocarbons (for example,
cyclohexane and methylcyclohexane) ; aromatic hydrocarbons
(for example, benzene, toluene, and benzenes having a
long-chain alkyl group (xylene, hexyl benzene, heptyl benzene,
octyl benzene, nonyl benzene, decyl benzene, undecyl benzene,
dodecyl benzene, tridecyl benzene, and tetradecyl benzene));
halogenated hydrocarbons (for example, methylene chloride,
chloroform, carbon tetrachloride, and 1,2-dichloroethane);
and carboxylates. In addition, other various kinds of oils
may be used as the dispersion medium. In addition, a single
or a mixture of the above materials may be used as a dispersion
medium, or surfactant or the like may be further mixed with
a dispersion medium.
[0026]
Electrophoretic particles are particles (polymer or
colloid) which move in a dispersion medium by the electric
field. In the present embodiment, white electrophoretic
particles and black electrophoretic particles are contained
in the microcapsule 102a. The black electrophoretic particle
is a particle formed of a black pigment, such as aniline black
or carbon black, for example. In the present embodiment, the
black electrophoretic particle is positively charged. The
white electrophoretic particle is a particle formed of a white
pigment, such as a titanium dioxide or an aluminum oxide, for
example. In the present embodiment, the white
19
. »
• >
electrophoretic particle is negatively charged.
[0027]
The second substrate 103 includes a film 103a and a
transparent common electrode layer 103b (second electrode)
formed on the bottom surface of the film 103a. The film 103a
serves to seal and protect the electrophoretic layer 102, and
is a polyethylene terephthalate film, for example. The film
103a is transparent and has an insulation property. The
common electrode layer 103b is formed of a transparent
conductive film, such as an indium tin oxide film (ITO film) ,
for example.
[0028]
Fig. 3 is a view showing an equivalent circuit of the
pixel 110. Moreover, in the present embodiment, in order to
distinguish the scanning lines 112, the scanning lines 112
shown in Fig. 1 may be called scanning lines on first, second,
third, ..., (m-l)-th, and m-th rows in order from the top.
Similarly, in order to distinguish the data lines 114, the
data lines 114 shown in Fig. 1 may be called data lines on
first, second, third, ..., (n-l)-th, and n-th rows in order from
the left.
Fig. 3 shows an equivalent circuit of the pixel 110
corresponding to the intersection between the scanning line
112 on the i-th row and the data line 114 on the j-th column.
Since the pixels 110 corresponding to the intersections
20
« *
• •
between other data lines 114 and other scanning lines 112 also
have the same configuration shown in the drawing, an
equivalent circuit of the pixel 110 corresponding to the
j intersection between the data line 114 on the i-th row and
the scanning line 112 on the j-th column will be
representatively described, and explanation regarding
equivalent circuits of other pixels 110 will be omitted.
[0029]
As shown in Fig. 3, each pixel 110 has an n channel type
thin film transistor (hereinafter, abbreviated as a "TFT")
110a, a display element 110b, and an auxiliary capacitor 110c.
In the pixel 110, a gate electrode of the TFT 110a is connected
to the scanning line 112 on the i-th row, a source electrode
of the TFT 110a is connected to the data line 114 on the j-th
column, and a drain electrode of the TFT 110a is connected
to a pixel electrode lOld, which is one end of the display
element 110b, and one end of the auxiliary capacitor 110c.
The auxiliary capacitor 110c has a configuration in which a
dielectric layer is interposed between a pair of electrodes
formed in the circuit layer 101c. The electrode of the other
end of the auxiliary capacitor 110c has a voltage common to
all pixels. The pixel electrode lOld faces the common
electrode layer 103b, and the electrophoretic layer 102 is
interposed between the pixel electrode lOld and the common
electrode layer 103b. Accordingly, when seen in the
21
I
i
I
I
> !
< • |
I
l
i
equivalent circuit, the display element 110b is a capacitor
in which the electrophoretic layer 102 is interposed between
the pixel electrode lOld and the common electrode layer 103b.
In addition, the display element 110b holds (stores) a voltage
between both the electrodes and performs display according
to the direction of an electric field caused by the held
voltage. Moreover, in the present embodiment, a common
voltage Vcom is applied to the electrode of the other end of
the auxiliary capacitor 110c of each pixel 110 and the common
electrode layer 103b by an external circuit (not shown).
[0030]
Referring back to Fig. 1, the scanning line driving
circuit 130 is connected to each scanning line 112 of the
display area 100. Under the control of the controller 5, the
scanning line driving circuit 130 selects the scanning lines
112 in order of first, second, ..., m-th rows, and supplies a
high-level (High) signal to the selected scanning line 112
and supplies a low-level (Low) signal to the other scanning
lines 112 which are not selected.
The data line driving circuit 140 is connected to each
data line 114 in the display area, and supplies a data signal
to the data line 114 on each column according to the display
content of the pixels 110 on one row which are connected to
the selected scanning line 112.
[0031]
22
* »
A period until the selection of the scanning line 112
on the m-th row ends after the scanning line driving circuit
130 selects the scanning line 112 on the first row
(hereinafter, referred to as a "frame period" or simply
referred to as a "frame") , each scanning line 112 is selected
once, and a data signal is supplied to each pixel 110 once
in one frame.
When the scanning line 112 changes to the high level,
the TFT 110a whose gate is connected to the scanning line 112
is turned on and accordingly, the pixel electrode lOld is
connected to the data line 114. If a data signal is supplied
to the data line 114 when the scanning line 112 is at a high
level and, the data signal is applied to the pixel electrode
lOld through the TFT 110a which is in the ON state. When the
scanning line 112 changes to the low level, the TFT 110a is
turned off. However, the voltage applied to the pixel
electrode lOld by the data signal is accumulated in the
auxiliary capacitor 110c, and electrophoretic particles move
according to the potential difference (voltage) between the
electric potential of the pixel electrode lOld and the
electric potential of the common electrode layer 103b.
[0032]
For example, when the voltage of the pixel electrode
lOld is +15 V (second voltage) with the voltage Vcom of the
common electrode layer 103b as a reference, white
23
i i
• »
© electrophoretic particles negatively charged move toward the
pixel electrode lOld and black electrophoretic particles
positively charged move toward the common electrode layer
103b. As a result, the pixel 110 is displayed in black. In
addition, when the voltage of the pixel electrode lOld is -15
V (first voltage) with the voltage Vcom of the common
electrode layer 103b as a reference, black electrophoretic
particles positively charged move toward the pixel electrode
lOld and white electrophoretic particles negatively charged
move toward the common electrode layer 103b. As a result,
the pixel 110 is displayed in white. In addition, the voltage
of the pixel electrode lOld is not limited to the
above-described voltage, and may be a voltage other than +15
V or -15 V as long as it is a positive or negative voltage
with the voltage Vcom of the common electrode layer 103b as
a reference.
[0033]
In the present embodiment, when changing the display
state of each pixel 110 from white (low gradation) as first
gradation to black (high gradation) as second gradation or
from black to white, the display state is changed by a writing
operation, which is to supply a data signal to the pixel 110
over a plurality of frames, instead of changing the display
state by supplying a data signal to the pixel 110 in only one
frame. This is because, when changing the display state from
24
i I
•
white to black, black electrophoretic particles do not move
to the display side completely even if the potential
difference is given to the electrophoretic particles in only
one frame and accordingly, the display state does not become
a full black display state. This is the same for white
electrophoretic particles when changing the display state
from black to white. Therefore, for example, a data signal
for displaying the black on the pixel 110 is supplied to the
pixel 110 over a plurality of frames when changing the display
state of the pixel 110 from white to black, and a data signal
for displaying the white on the pixel is supplied to the pixel
110 over a plurality of frame when changing the display state
of the pixel 110 from black to white.
[0034]
Moreover, in the present embodiment, the pixel
electrode lOld of a certain pixel 110 in one frame may be set
as a positive electrode with a higher electric potential than
the common electrode layer 103b, and the pixel electrode lOld
of another pixel 110 in the same frame may be set as a negative
electrode with a lower electric potential than the common
electrode layer 103b. That is, driving capable of selecting
both electrodes of positive and negative electrodes with
respect to the common electrode layer 103b in one frame
(hereinafter, referred to as bipolar driving) is performed.
More specifically, in one frame, the pixel electrode lOld of
25
. *
the pixel 110 which changes the gradation to the high
gradation side (second gradation side) is set as a positive
electrode, and the pixel electrode lOld of the pixel 110 which
changes the gradation to the low gradation side (first
gradation side) is set as a negative electrode. In addition,
when black electrophoretic particles are negatively charged
and white electrophoretic particles are positively charged,
the pixel electrode lOld of the pixel 110 which changes the
gradation to the high gradation side (second gradation side)
may be set as a negative electrode, and the pixel electrode
lOld of the pixel 110 which changes the gradation to the low
gradation side (first gradation side) may be set as a positive
electrode.
[0035]
Next, the remaining number-of-times storage region B,
the gradation value storage region C, the number-of-times
difference storage region D, and the planned image storage
region E will be described. Fig 4 shows views showing some
pixels 110 in the display area 100 and storage regions
corresponding to the pixels 110. The storage region includes
storage regions corresponds to each of the pixels 110 arrayed
in m rows x n columns.
Fig. 4 (a) is a view showing the arrangement of the pixels
110. A pixel P(i,j) expresses one pixel 110 located on the
i-th row and the j-th column. The subscript i indicates the
26
row number of the pixel 110 arrayed in a matrix, and the
subscript j indicates the column number.
Fig. 4(b) is a view showing a buffer, which corresponds
i to each pixel shown in Fig. 4 (a) , in the VRAM 3. For example,
I
a buffer A(i, j ) is a storage region corresponding to the pixel
P(i,j) . The pixel data indicating the gradation of the pixel
P(i,j) is stored in the buffer A(i, j ) . In addition, the pixel
data with a value "0" is written when displaying a pixel in
black, and the pixel data with a value "5" is written when
displaying a pixel in white.
Fig. 4(c) is a view showing a storage region, which
corresponds to each pixel shown in Fig. 4 (a) , in the remaining
number-of-times storage region B. For example, a remaining
number-of-times storage region B(i,j) is a storage region
corresponding to the pixel P(i,j). The value indicating the
remaining number of times of application when applying a
voltage to the pixel P(i,j) multiple times is stored in the
remaining number-of-times storage region B(i,j).
Fig. 4(d) is a view showing a storage region, which
corresponds to each pixel shown in Fig. 4 (a) , in the gradation
value storage region C. For example, a gradation value
storage region C(i,j) is a storage region corresponding to
the pixel P(i,j). The value indicating the gradation of the
pixel P(i,j), which has changed due to voltage application,
is stored in the gradation value storage region C(i,j).
| 27
• •
*
•
Fig. 4 (e) is a view showing a storage region, which
corresponds to each pixel shown in Fig. 4 (a) , in the
number-of-times difference storage region D. For example,
the number-of-times difference storage region D(i,j) is a
storage region corresponding to the pixel P(i,j). The value
indicating the difference between the number of times of
application of the positive voltage to the pixel P(i,j) and
the number of times of application of the negative voltage
to the pixel P(i,j) is stored in the number-of-times
difference storage region D(i,j).
Fig. 4(f) is a view showing a storage region, which
corresponds to each pixel shown in Fig. 4(a), in the planned
image storage region E. For example, a planned image storage
region E(i,j) is a storage region corresponding to the pixel
P(i,j). The pixel data of each pixel of an image to be
displayed in the display area 100 is stored in the planned
image storage region E(i,j).
[0036]
Next, the configuration of the controller 5 will be
described. Fig. 5 is a block diagram showing functions
realized in the controller 5. In the controller 5, a
number-of-times difference calculating section 501, a
voltage control section 502, and an application
number-of-times determining section 503 are realized. In
addition, each of the blocks may be realized by hardware, or
28
•
may be realized by providing a CPU in the controller 5 and
executing a program by the CPU.
The number-of-times difference calculating section 501
is a block which calculates the number-of-times difference
for each pixel. The number-of-times difference calculating
section 501 increments the value of the number-of-times
difference storage region D(i,j) when the second voltage is
applied to the pixel electrode lOld of the pixel P(i,j)
corresponding to the number-of-times difference storage
region D(i, j) and decrements the value of the number-of-times
difference storage region D(i,j) when the first voltage is
applied to the pixel electrode lOld of the pixel P(i,j)
corresponding to the number-of-times difference storage
region D(i, j) , and calculates a difference between the number
of times of application of the first voltage and the number
of times of application of the second voltage. The
number-of-times difference calculating section 501 writes
the difference between the number of times of application of
the first voltage and the number of times of application of
the second voltage in the number-of-times difference storage
region D(i,j).
[0037]
When the value of the number-of-times difference
storage region D(i,j) is not a predetermined value at the
timing when the value of the remaining number-of-times
29
|
* »
storage region B(i,j) of the voltage control section 502 is
0, the voltage control section 502 controls the scanning line
driving circuit 130 and the data line driving circuit 140
until the value of the number-of-times difference storage
region D(i,j) becomes the predetermined value to apply the j
first or second voltage to the pixel electrode lOld. In
addition, when the value of the number-of-times difference
storage region D(i,j) is not a predetermined value at the
timing when the value of the buffer A(i,j) and the value of
the planned image storage region E(i,j) are different, the
voltage control section 502 controls the scanning line
driving circuit 130 and the data line driving circuit 140
until the value of the number-of-times difference storage
j
region D(i,j) becomes the predetermined value to apply the
first or second voltage to the pixel electrode lOld. In
addition, the voltage control section 502 controls the
scanning line driving circuit 130 and the data line driving
circuit 140 on the basis of the value of the planned image
storage region E(i,j) and the value of the remaining
number-of-times storage region B(i,j) to apply the first or
second voltage to the pixel electrode lOld. In addition, when
changing the gradation of a pixel before a voltage is applied
to the pixel multiple times, the voltage control section 502
starts a new operation of applying the voltage to the pixel
multiple times even in the middle of the writing operation.
30
» *
* »
[0038]
The application number-of-times determining section
503 is a block which determines the number of times of
application of the first or second voltage for changing the
gradation of the pixel P(i,j) on the basis of the value of
the gradation value storage region C(i,j), the value of the
buffer A(i,j), and a table shown in Fig. 6 which will be
described later. The application number-of-times
determining section 503 writes the determined number of times
of application in the remaining number-of-times storage
region B(i,j).
[0039]
Moreover, in the present embodiment, the minimum number
of times of voltage application (the number of frames)
required to change the display state from white to black is
different from the minimum number of times of voltage
application (the number of frames) required to change the
display state from black to white. Fig. 6 is a view showing
the minimum number of times of voltage application required
to change the gradation. The controller 5 stores the table
shown in Fig. 6. In the present embodiment, the gradation
of the pixel 110 changes in six levels of 0 to 5, and the
density increases as the gradation value decreases. The
gradation value of 0 is defined as black, and the gradation
value of 5 is defined as white.
| 31
|
« *
Referring to Fig. 6, in the present embodiment, when a
voltage of -15 V with the voltage Vcom of the common electrode
layer 103b as a reference is applied five times to the pixel
electrode lOld from the state where the gradation value is
0 (state where the pixel is black), the gradation value
becomes 5 (pixel becomes white). On the other hand, when a
voltage of +15 V with the voltage Vcom of the common electrode
layer 103b as a reference is applied three times to the pixel
electrode lOld from the state where the gradation value is
5 (state where the pixel is white), the gradation value
becomes 0 (pixel becomes black).
! [0040]
i
Image rewriting can be quickly performed if a voltage
is applied by the minimum number of times required to change
the gradation. However, since the number of times of voltage
application when changing the display state of a pixel from
black to white is different from that when changing the
display state of a pixel from white to black, a difference
between the number of times of application of a positive
voltage with the common electrode layer 103b as a reference
and the number of times of application of a negative voltage
with the common electrode layer 103b as a reference occurs.
This may deteriorate a microcapsule quickly. In the present
embodiment, therefore, a large difference does not occur
between the number of times of application of a positive
I 32
j
I
i
* »
voltage with the voltage Vcom of the common electrode layer
103b as a reference and the number of times of application
of a negative voltage with the voltage Vcom of the common
electrode layer 103b as a reference. Hereinafter, the
operation will be described.
[0041]
(First operation example of the first embodiment)
Next, an operation of the present embodiment will be
described. Figs. 7 to 10 are flow charts showing the flow
of processing performed by the controller 5. In addition,
Fig. 11 is a view showing the content of each storage region
changing with time. Fig. 11 shows the content of a buffer
A(l,l), a remaining number-of-times storage region B(l,l),
a gradation value storage region C(l,l), a number-of-times
difference storage region D(l,l), and a planned image storage
region E (1,1) corresponding to one pixel P (1,1) . In addition,
the content of each storage region is a value after a frame
period ends. In addition, Fig. 11 also shows the polarity
of a voltage, which is applied to the pixel electrode lOld
in one frame period, with respect to the common electrode
layer 103b.
[0042]
First, in the first frame shown in Fig. 11, the buffer
A(l,l) is 5, the gradation value storage region C(l,l) is 5,
and the remaining number-of-times storage region B(l,l) and
\ 33
the number-of-times difference storage region D(l,l) are 0.
Here, until the third frame starts, the voltage applied to
the pixel electrode lOld is the same as the voltage Vcom, and
the value of each storage region does not change.
[0043]
Then, when the content of the VRAM 3 is rewritten before
the start of the third frame, the controller 5 performs the
processing shown in Fig. 7 before the start of the frame period.
Specifically, the controller 5 rewrites the content of the
remaining number-of-times storage region B and the planned
j
image storage region E according to the content of each
storage region.
First, the controller 5 initializes variables i and j
to set them to 1 (steps SA1 and SA2). Then, the controller
5 determines whether or not the value of the buffer A(i,j)
is the same as the value of the planned image storage region
E(i,j). When the value of the buffer A(i,j) is the same as
the value of the planned image storage region E(i,j) (YES in
step SA3), the controller 5 proceeds to step SA9.
On the other hand, when the value of the buffer A(i,j)
is different from the value of the planned image storage
region E(i,j) (NO in step SA3), the controller 5 determines
whether or not the remaining number-of-times storage region
B(i,j) is 0. When the remaining number-of-times storage
region B(i,j) is 0 (YES in step SA4), the controller 5 writes
j
I 34
*
* *
^^ the remaining number of times of application in the remaining
number-of-times storage region B(i,j) on the basis of the
buffer A(i, j ) , the gradation value storage region C(i,j) , and
the table shown in Fig. 6 (step SA5). After the end of step
SA5, the controller 5 overwrites the value of the planned
image storage region E(i,j) with the value of the buffer
A(i,j) .
[0044]
In addition, when the value of the remaining
number-of-times storage region B(i,j) is not 0 (NO in step
SA4), the controller 5 determines whether or not the value
of the buffer A (i, j ) is 5 (white) . When the value of the buffer
A(i,j) is not 5 (NO in step SA7), the controller 5 proceeds
to step SA5. On the other hand, when the value of the buffer
A(i,j) is 5 (YES in step SA7), the controller 5 determines
whether or not the value of the number-of-times difference
storage region D(i,j) is equal to or smaller than a threshold
value (in the present embodiment, -4) set in advance (in other
words, when the value of the buffer A(i,j) is 5 (YES in step
SA7), the controller 5 determines whether or not the absolute
value of the value of the number-of-times difference storage
region D(i, j) is larger by 4 or more than the threshold value
set in advance) . When the value of the number-of-times
difference storage region D(i,j) is not equal to or smaller
than the threshold value (NO in step SA8), the controller 5
i
| 35
* *
proceeds to step SA5. In addition, when the value of the
number-of-times difference storage region D(i,j) is equal to
or smaller than the threshold value (YES in step SA8), the
controller 5 proceeds to step SA9.
[0045]
In step SA9f the controller 5 determines whether or not
the value of the variable j is n. When the value of the
variable j is not n, the controller 5 increments the variable
j and proceeds to step SA3. In addition, when the value of
the variable j is n, the controller 5 determines whether or
not the value of the variable i is m in step SA10. When the
value of the variable i is not m, the controller 5 increments
the variable i and proceeds to step SA2. In addition, when
the value of the variable i is m, the controller 5 ends the
processing shown in Fig. 7.
[0046]
For example, when the buffer A(l,l) is rewritten from
5 to 0 before the start of the third frame and the value of
the buffer A(l,l) is different from the value (5) of the
planned image storage region E(l,l) before the start of the
third frame (NO in step SA3), the controller 5 determines
whether or not the remaining number-of-times storage region
B(l,l) is 0. When the remaining number-of-times storage
region B(l,l) is 0 at the time before the start of the third
frame as shown in Fig. 11 (YES in step SA4), the controller
j 36
5 writes the number of times of voltage application, which
is required to change the gradation of the pixel P(l,l) from
5 to 0, in the remaining number-of-times storage region B (1,1)
(step SA5). Referring to Fig. 6, the number of times of
voltage application required to change the gradation of a
pixel from 5 which is a value of the gradation value storage
region C(i,j) to 0 which is a value of the buffer A(i,j) is
3. Accordingly, the controller 5 writes 3 in the remaining
number-of-times storage region B(l,l). In addition, the
controller 5 overwrites the value of the planned image storage
region E(i,j) with 0 which is a value of the buffer A(i,j)
(step SA6).
[0047]
The controller 5 drives the scanning line driving
circuit 130 and the data line driving circuit 140 in a frame
period after the processing shown in Fig. 7 ends. The
controller 5 performs processing shown in Figs. 8 to 10 when
driving the data line driving circuit. First, the controller
5 initializes the variables i and j to set them to 1 (steps
SB1 and SB2). Then, the controller 5 determines whether or
not the value of the buffer A(i,j) is 0. When the value of
the buffer A(i,j) is 0 (black) (YES in step SB3) , the
controller 5 performs processing shown to Fig. 9 in step SB4 .
First, the controller 5 determines whether or not the
value of the remaining number-of-times storage region B(i,j)
I
I 37
•
!
« »
•
4 *
is 0. When the value of the remaining number-of-times storage
• . ..
region B(i,;j) is not 0 (NO in step SCI), the controller 5
decrements the value of the remaining number-of-times storage
region B(i,j) (step SC2). In addition, the controller 5 sets
the data line 114 on the j-th column to +15 V with the voltage
Vcom as a reference (step SC3) and then increments the value
of the number-of-times difference storage region D(i,j) (step
SC4) . Then, the controller 5 updates the value of the
gradation value storage region C(i,j) (step SC5), and
proceeds to step SC6.
[0048]
In addition, when the value of the remaining
number-of-times storage region B(i,j) is 0 (YES in step SCI),
the controller 5 determines whether or not the value of the
number-of-times difference storage region D(i,j) is smaller
than 5. When the value of the number-of-times difference
storage region D(i,j) is smaller than 5 (YES in step SC6),
the controller 5 proceeds to step SC3. When the value of the
number-of-times difference storage region D(i,j) is equal to
or larger than the threshold value (here, 5) set in advance
(NO in step SC6), the controller 5 sets the data line 114 on
the j-th column to 0 V with the voltage Vcom as a reference
(step SC7), and proceeds to step SB6.
[0049]
Referring back to Fig. 8, when the value of the buffer
38
» »
« *
A(i,j) is 5 (white) (NO in step SB3) , the controller 5 performs
processing shown in Fig. 10. The controller 5 determines
whether or not the value of the buffer A(i,j) is the same as
the value of the planned image storage region E(i,j). When
the value of the buffer A(i,j) is different from the value
of the planned image storage region E(i,j) (NO in step SD1) ,
the controller 5 sets the data line 114 on the j-th column
to +15 V with the voltage Vcom as a reference (step SD2) and
then increments the value of the number-of-times difference
storage region D(i,j) (step SD3). Then, the controller 5
updates the value of the gradation value storage region C (i, j )
(step SD4). Then, when the value of the number-of-times
difference storage region D(i,j) is 5 (YES in step SD5), the
controller 5 overwrites the value of the planned image storage
region E(i, j) with the value of the buffer A(i, j) (step SD6) .
After the end of step SD6, the controller 5 proceeds to step
SB6. In addition, when the value of the number-of-times
difference storage region D(i,j) is not 5 (NO in step SD5),
the controller 5 proceeds to step SB6.
[0050]
In addition, when YES is determined in step SD1, the
controller 5 determines whether or not the value of the
remaining number-of-times storage region B(i,j) is 0. When
the value of the remaining number-of-times storage region
B(i,j) is 0 (YES in step SD7), the controller 5 sets the data
I 39
* *
line 114 on the j-th column to 0 V with the voltage Vcom as
a reference (step SD12), and proceeds to step SB6.
[0051]
In addition, when NO is determined in step SD7, the
controller 5 decrements the value of the remaining
number-of-times storage region B(i,j) (step SD8). Then, the
controller 5 sets the data line 114 on the j-th column to -15
V with the voltage Vcom as a reference (step SD9) , and
decrements the value of the number-of-times difference
storage region D(i,j) (step SD10). Then, the controller 5
updates the value of the gradation value storage region C (i, j )
(step SD11). After the end of step SD11, the controller 5
proceeds to step SB6.
[0052]
Referring back to Fig. 8, the controller 5 determines
whether or not the value of the variable j is n in step SB6.
When the value of the variable j is not n, the controller 5
increments the variable j and proceeds to step SB3. In
addition, when the value of the variable j is n, the controller
5 drives a scanning line on the i-th row (step SB7) . Then,
the controller 5 determines whether or not the value of the
variable i is m in step SB8. When the value of the variable
i is not m, the controller 5 increments the variable i and
proceeds to step SB2. In addition, when the value of the
variable i is m, the controller 5 ends the processing shown
40
*
in Fig. 8.
[0053]
For example, at the start of the third frame, the value
of the buffer A (1,1) is 0 (YES in step SB3) and the value of
the remaining number-of-times storage region B(l,l) is 3 (NO
in step SCI). Accordingly, the controller 5 decrements the
value of the remaining number-of-times storage region B(l,l)
to set it to 2 (step SC2). After setting the data line 114
on the first column to +15 V with the voltage Vcom as a
reference (step SC3), the controller 5 increments the value
of the number-of-times difference storage region D(l,l) to
set it to 1 (step SC4).
Then, the controller 5 updates the value of the
gradation value storage region C (1,1) (step SC5) . In addition,
when a voltage of +15 V with the voltage Vcom as a reference
is applied to the pixel electrode lOld, the actual variation
in the gradation value of a pixel caused by one voltage
application is 2. Therefore, when the third frame ends, the
gradation value of the gradation value storage region C(l,l)
becomes 3. Then, when the scanning line 112 on the first row
is driven (step SB7) , a voltage of +15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld of the
pixel on the first row and the first column, such that black
electrophoretic particles move toward the common electrode
layer 103b.
41
• *
[0054]
I Then, in the fourth and fifth frames, the controller 5
performs the same processing as in the third frame. Then,
in the sixth frame, the operation of the controller 5 is as
follows.
First, since the value of the buffer A(l,l) is 0 (YES
in step SB3) and the value of the remaining number-of-times
storage region B(l,l) is 0 (YES in step SCI), the controller
5 determines the value of the number-of-times difference
storage region D(l,l). In this case, since the value of the
number-of-times difference storage region D(l,l) is 3 which
is less than 5 (YES in step SC6), the controller 5 sets the
data line 114 on the first row to +15 V with the voltage Vcom
as a reference (step SC3), and then increments the value of
the number-of-times difference storage region D(l,l) to set
it to 4 (step SC4) . Then, the controller 5 updates the value
of the gradation value storage region C(l,l) (step SC5). In
addition, when the value of the gradation value storage region
C(l,l) is 0, the controller 5 holds the value 0 as it is.
[0055]
In the seventh frame, the controller 5 performs the same
processing as in the sixth frame. Then, in the eighth frame,
the operation of the controller 5 is as follows.
First, since the value of the buffer A(l,l) is 0 (YES
in step SB3) and the value of the remaining number-of-times
42
»
a *
storage region B(l,l) is 0 (YES in step SCI), the controller
5 determines the value of the number-of-times difference
storage region D(l,l). In this case, since the value of the
number-of-times difference storage region D(l,l) is 5 (NO in
step SC6) , the controller 5 sets the data line 114 on the first
column to 0 V with the voltage Vcom as a reference (step SC7) .
[0056]
Next, when the buffer A (1,1) is rewritten from 0 (black)
to 5 (white) before the start of the tenth frame, the operation
of the controller 5 is as follows.
Since the value of the buffer A (1,1) is different from
the value (0) of the planned image storage region E(l,l)
before the start of the tenth frame (NO in step SA3), the
controller 5 determines whether or not the remaining
number-of-times storage region B(l,l) is 0. When the
remaining number-of-times storage region B(l,l) is 0 at the
time before the start of the tenth frame (when the ninth frame
ends) as shown in Fig. 11 (YES in step SA4), the controller
5 writes the number of times of voltage application, which
is required to change the gradation of the pixel P(l,l) from
5 to 0, in the remaining number-of-times storage region B (1,1)
(step SA5). Referring to Fig. 6, since the number of times
of voltage application required to change the gradation of
a pixel from 5 to 0 is 3, the controller 5 writes 3 in the
remaining number-of-times storage region B(l,l). Then, the
43
»
controller 5 overwrites the value of the planned image storage
region E(i,j) with 5 which is a value of the buffer A(i,j)
(step SA6).
[0057]
Then, in a subsequent frame period, the controller 5
determines whether or not the value of the buffer A(i,j) is
0. When the value of the buffer A(i,j) is 5 (white) (NO in
step SB3), the controller 5 performs processing shown to Fig.
10.
First, since the value of the buffer A (i, j ) and the value
of the planned image storage region E(i,j) are the same (YES
in step SD1) and the value of the remaining number-of-times
storage region B (i, j ) is not 0 (NO in step SD7) , the controller
5 decrements the value of the remaining number-of-times
storage region B(l,l) to set it to 4 (step SD8). Then, the
controller 5 sets the data line 114 on the first column to
-15 V with the voltage Vcom as a reference (step SD9), and
then decrements the value of the number-of-times difference
storage region D(l,l) to set it to 4 (step SD10) . Then, the
controller 5 updates the value of the gradation value storage
region C(l,l) (step SD11). In addition, when a voltage of
-15 V with the voltage Vcom as a reference is applied to the
pixel electrode lOld, the actual variation in the gradation
value of a pixel caused by one voltage application is 1.
Therefore, when the tenth frame ends, the gradation value of
44
the gradation value storage region C(l,l) becomes 4. Then,
when the scanning line 112 on the first row is driven (step
SB7) , a voltage of -15 V with the voltage .Vcom as a reference
is applied to the pixel electrode lOld of the pixel on the
first row and the first column, such that white
electrophoretic particles move toward the common electrode
layer 103b.
[0058]
Then, the controller 5 applies a voltage to the pixel
electrode lOld in each frame period until the value of the
remaining number-of-times storage region B(l,l) becomes 0.
When the content of the remaining number-of-times storage
region B(l,l) becomes 0 at the start of the fifteenth frame,
the controller 5 applies the same voltage as the voltage Vcom
to the pixel electrode lOld in the fifteenth frame.
[0059]
(Second operation example of the first embodiment)
Next, an operation when the content of the VRAM 3 is
changed before the value of the remaining number-of-times
storage region becomes 0 will be described with reference to
Fig. 12. Fig. 12 is also a view showing the content of each
storage region changing with time. Fig. 12 shows the content
of the buffer A(1,1), the remaining number-of-times storage
region B(1,1), the gradation value storage region C(1,1), and
the number-of-times difference storage region D(l,l)
45
1
m
corresponding to one pixel P(l,l). In addition, since the
operation in first to fourth frames in Fig. 12 is the same
as the operation in the first to fourth frames in Fig. 11,
explanation thereof will be omitted.
[0060]
Before the value of the remaining number-of-times
storage region B(l,l) regarding the pixel P(l,l) becomes 0,
the controller 5 determines NO in step SA3 and determines NO
in step SA4 if 5 (white) is written in the buffer A(1,1) as
the gradation value of the pixel 110 before the fifth frame.
In addition, since the value of the buffer A(l,l) is 5 (YES
in step SA7) and the value of the number-of-times difference
storage region D(l,l) is 2, the controller 5 writes 4 in the
remaining number-of-times storage region B(l,l) in step SA5,
and writes 5 in the planned image storage region E(l,l) in
step SA6.
[0061]
Then, in the fifth to eighth frames, the controller 5
sets the voltage of the pixel electrode lOld of the pixel
P(l,l) to -15 V with the voltage Vcom as a reference. When
the value of the remaining number-of-times storage region
B(l,l) becomes 0 (ninth and tenth frames), the controller 5
sets the voltage of the pixel electrode lOld of the pixel
P(l,l) to the same voltage as the voltage Vcom.
[0062]
46
»
ft •
Then, when 0 (black) is written in the buffer A (1,1) as
the gradation value of the pixel 110 before the eleventh frame,
the controller 5 sets the voltage of the pixel electrode lOld
of the pixel P(l,l) to +15 V with the voltage Vcom as a
reference until the value of the number-of-times difference
storage region D(l,l) becomes 5, in the same manner as in the
frames from the third frames shown in Fig. 11. Then, when
5 (white) is written in the buffer A(l,l) as the gradation
value of the pixel 110 before the twentieth frame, the
controller 5 sets the voltage of the pixel electrode lOld of
the pixel P(l,l) to -15 V with the voltage Vcom as a reference
until the value of the remaining number-of-times storage
region B(l,l) becomes 0, in the same manner as in the frames
from the tenth frames shown in Fig. 11.
[0063]
(Third operation example of the first embodiment)
Next, a case where the operation of changing the content
of the buffer A(l,l) is repeated before the value of the
remaining number-of-times storage region B(l,l) becomes 0
will be described with reference to Fig. 13. Fig. 13 is also
a view showing the content of each storage region changing
with time. Fig. 13 shows the content of the buffer A(l,l),
the remaining number-of-times storage region B(l,l), the
gradation value storage region C(l,l), and the
number-of-times difference storage region D(l,l)
47
• *
corresponding to one pixel P(l,l). In addition, since the
operation in first to twelfth frames in Fig. 13 is the same
as the operation in the first to twelfth frames in Fig. 12,
explanation thereof will be omitted.
[0064]
When 5 (white) is written in the buffer A(l,l) as the
gradation value of the pixel 110 before the thirteenth frame,
the controller 5 performs the same operation as in the fifth
to eighth frames. Then, when 0 (black) is written in the
buffer A(1,1) as the gradation value of the pixel 110 before
the nineteenth frame and 5 (white) is written in the buffer
A(l,l) as the gradation value of the pixel 110 before the
twenty-first frame, the controller 5 performs the same
operation as in the third to eighth frames for the nineteenth
to twenty-fourth frames. In addition, when 0 (black) is
written in the buffer A(1,1) as the gradation value of the
pixel 110 before the twenty-seventh frame, the controller 5
performs the same operation as in the third and fourth frames
i
for the twenty-seventh and twenty-eighth frames.
[0065]
Then, when 5 (white) is written in the buffer A (1,1) as
the gradation value of the pixel 110 before the twenty-ninth
frame, the controller 5 determines NO in step SA3 and
determines NO in step SA4. In addition, since the value of
the buffer A(l,l) is 5 (YES in step SA7), the controller 5
48
determines the value of the number-of-times difference
storage region D(l,l). In this case, since the value of the
number-of-times difference storage region D(l,l) is -4, the
controller 5 determines YES in step SA8 and does not update
the content of the planned image storage region E(l,l).
[0066]
Then, in a subsequent frame period, the controller 5
performs processing in step SB5 since the value of the buffer
A(l,l) is 5. First, since the value of the buffer A(l,l) is
different from the value of the planned image storage region
E(l,l) (NO in step SD1), the controller 5 sets the data line
114 on the first column to +15 V with the voltage Vcom as a
reference (step SD2) and then increments the value of the
number-of-times difference storage region D(l,l) to set it
to -3. In addition, the controller 5 updates the value of
the gradation value storage region C(l,l) to 0. Then, the
controller 5 determines whether or not the value of the
number-of-times difference storage region D(l,l) is 5. In
this case, since the value of the number-of-times difference
storage region D(l,l) is -3, the controller 5 determines NO
in step SD5 and the value of the planned image storage region
E(l,l) is held as 0 as it is.
Then, when the scanning line 112 on the first row is
driven (step SB7), a voltage of +15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld of the
i
49
4 »
pixel on the first row and the first column, such that black
electrophoretic particles move toward the common electrode
layer 103b even though the value of the buffer A(1,1) is 5
indicating the white as the gradation of a pixel.
[0067]
In the thirtieth to thirty-sixth frames, the controller
5 performs the same operation as in the twenty-ninth frame
for the pixel P(l,l) . In the thirty-seventh frame, the value
of the buffer A(l, 1) is different from the value of the planned
image storage region E(l,l) (NO in step SDl). Accordingly,
the controller 5 sets the data line 114 on the first column
to +15 V with the voltage Vcom as a reference (step SD2) and
then increments the value of the number-of-times difference
storage region D(l,l) to set it to 5. Then, since the value
of the number-of-times difference storage region D(l,l) is
5 (NO in step SD5), the controller 5 overwrites the value of
the planned image storage region E (1,1) with 5 which is a value
of the buffer A(l,l), and writes the value in the remaining
number-of-times storage region B(l,l) on the basis of the
buffer A (1,1) , the gradation value storage region C (1,1) , and
the table shown in Fig. 6.
[0068]
In the thirty-eighth frame, the controller 5 performs
processing in step SB5 since the value of the buffer A(1,1)
is 5. Since the value of the buffer A(l,l) and the value of
50
a
the planned image storage region E(l,l) are the same and the
value of the remaining number-of-times storage region B(l,l)
is not 0, the controller 5 performs processing in steps SD8
to SD11. That is, a voltage of -15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld of the
pixel on the first row and the first column.
Then, until the forty-second frame, the controller 5
applies a voltage of -15 V with the voltage Vcom as a reference
to the pixel electrode lOld of the pixel P(l,l).
[0069]
If a voltage of -15 V with the voltage Vcom as a reference
is applied to the pixel electrode lOld of the pixel P(l,l)
from the twenty-ninth frame by rewriting the buffer A(1,1),
the absolute value of the value of the number-of-times
difference storage region D(l,l) increases further. That is,
in the pixel P(l,l), a large difference occurs between the
number of times of application of a positive voltage with the
common electrode layer 103b as a reference and the number of
times of application of a negative voltage with the common
electrode layer 103b as a reference. As a result, the pixel
110 quickly deteriorates.
In contrast, in the present embodiment, the voltage
applied to the pixel electrode lOld is controlled even if the
content of the buffer storage region is rewritten, in the same
manner as in the above-described operation from the
51
N twenty-ninth frame. Accordingly, a large difference does not
occur between the number of times of application of a positive
voltage with the common electrode layer 103b as a reference
and the number of times of application of a negative voltage
with the common electrode layer 103b as a reference. As a
result, it is possible to suppress deterioration of the pixel
110.
[0070]
[Second embodiment]
Next, a second embodiment of the invention will be
described. A display device according to the second
embodiment has the same hardware configuration as in the first
embodiment. The display device according to the second
embodiment is different from the display device according to
the first embodiment in that the gradation value storage
region C is not provided, and processing of the controller
5 is also different between the display device according to
the second embodiment and the display device according to the
first embodiment. The following explanation will be given
focusing on this different point.
[0071]
Figs. 14 to 16 are flow charts showing the flow of
processing performed by the controller 5. Fig. 14 is a view
showing the flow of processing performed by the controller
5 when the content of the VRAM 3 is rewritten. The processing
52
< »
shown in Fig. 14 is different from the processing in the first
embodiment shown in Fig. 7 in that step SA11 is included. When
the value of the buffer A(i,j) is different from the value
of the planned image storage region E(i,j), the value of the
remaining number-of-times storage region B(i, j) is not 0, and
the value of the buffer A(i,j) is 0, the controller 5
determines whether or not the value of the number-of'-times
difference storage region D(i,j) is equal to or larger than
4 in step SAIL When the value of the number-of-times
difference storage region D(i,j) is smaller than the
threshold value (here, 4) set in advance in step SA11, the
controller 5 proceeds to step SA5. On the other hand, when
the value of the number-of-times difference storage region
D(i,j) is equal to or larger than 4 in step SA11, the
controller 5 proceeds to step SA9.
[0072]
In addition, the processing shown in Fig. 8 is performed
as processing when driving the data line driving circuit 140.
In the present embodiment, however, the content in step SB4
is different from the content in step SB5. Fig. 15 is a flow
chart showing the flow of processing in step SB4 (subroutine
1) in the present embodiment.
The controller 5 determines whether or not the value of
the buffer A (i, j ) is the same as the value of the planned image
storage region E(i,j). When the value of the buffer A(i,j)
53
is different from the value of the planned image storage
region E (i, j ) (NO in step SEl) , the controller 5 sets the data
line 114 on the j-th column to -15 V with the voltage Vcom
as a reference (step SE2) and then decrements the value of
the number-of-times difference storage region D(i,j) (step
SE3) . Then, when the value of the number-of-times difference
storage region D(i,j) is 0 (YES in step SE4), the controller
5 overwrites the value of the planned image storage region
E(i, j) with the value of the buffer A(i, j) (step SE5) . After
the end of step SE5, the controller 5 proceeds to step SB6.
In addition, when the value of the number-of-times difference
storage region D (i, j ) is not 0 (NO in step SE4) , the controller
5 proceeds to step SB6.
[0073]
In addition, when YES is determined in step SEl, the
controller 5 determines whether or not the value of the
remaining number-of-times storage region B(i,j) is 0. When
the value of the remaining number-of-times storage region
B(i,j) is 0 (YES in step SE6), the controller 5 determines
whether or not the value of the number-of-times difference
storage region D(i,j) is smaller than 5. When the value of
I the number-of-times difference storage region D(i,j) is
smaller than 5 (YES in step SE10), the controller 5 proceeds
to step SE7. On the other hand, when the value of the
i
number-of-times difference storage region D(i,j) is not
54
I I
»
smaller than 5 (NO in step SE10), the controller 5 sets the
data line 114 on the j-th column to 0 V with the voltage Vcom
as a reference (step SE11), and proceeds to step SB6.
[0074]
In addition, when NO is determined in step SE6, the
controller 5 decrements the value of the remaining
number-of-times storage region B(i,j) (step SE7). Then, the
controller 5 sets the data line 114 on the j-th column to +15
V with the voltage Vcom as a reference (step SE8), and
decrements the value of the number-of-times difference
storage region D(i,j) (step SE9). After the end of step SE9,
the controller 5 proceeds to step SB6.
[0075]
Fig. 16 is a flow chart showing the flow of processing
in step SB5 (subroutine 2) in the present embodiment. The
processing shown in Fig. 10 is the same processing as in the
first embodiment except that the processing in steps SD4 and
SD11 is not included and steps SD13 and SD14 are included.
In addition, the processing in step SD14 is the same
processing as in step SD12 in the first embodiment. When the
value of the number-of-times difference storage region D(i, j)
is larger than 0 in step SD13 (YES in step SD13) , the
controller 5 proceeds to step SD8. On the other hand, when
the value of the number-of-times difference storage region
D(i,j) is equal to or smaller than 0 (NO in step SD13), the
55
controller 5 sets the data line 114 on the j-th column to 0
V with the voltage Vcom as a reference (step SE11), and
proceeds to step SB6.
[0076]
(First operation example of the second embodiment)
Next, an operation of the second embodiment will be
described. Fig. 17 is a view showing the content of each
storage region changing with time. Fig. 17 shows the content
of a buffer A(l,l), a remaining number-of-times storage
region B(l,l), a number-of-times difference storage region
D(l,l), and a planned image storage region E(l,l)
corresponding to one pixel P(l,l). In addition, the content
of each storage region is a value after a frame period ends.
In addition, Fig. 17 also shows the polarity of a voltage,
which is applied to the pixel electrode lOld in one frame
period, with respect to the common electrode layer 103b.
[0077]
First, when the buffer A(l,l) is rewritten from 5 to 0
before the start of the third frame, the controller 5 performs
the processing shown in Fig. 14 before the start of the frame
period. Here, when the pixel P(l,l) is focused, the
controller 5 writes 5 in the remaining number-of-times
storage region B(l,l) in step SA5, and writes 0 in the planned
image storage region E(l,l). Thus, the present embodiment
is different from the first embodiment in that 5 is written
56
without using the table shown in Fig. 6.
[0078]
In the third to seventh frames, the controller 5 applies
a voltage of +15 V with the voltage Vcom as a reference to
the pixel electrode lOld of the pixel P(l, 1) , and decrements
the value of the remaining number-of-times storage region
B(l,l) and increments the value of the number-of-times
difference storage region D(l,l).
In the eighth and ninth frames, the value of the buffer
A(l,l) and the value of the planned image storage region
E(l,l) are the same and the value of the remaining
number-of-times storage region B(1,1) is 0. Accordingly, the
controller 5 sets the voltage of the pixel electrode lOld of
the pixel P(l,l) to be the same as the voltage Vcom.
When the buffer A (1,1) is rewritten from 5 to 0 before
the start of the tenth frame, the controller 5 writes 5 in
the remaining number-of-times storage region B(l,l) in step
SA5, and writes 5 in the planned image storage region E(l,l).
i
In the tenth to fourteenth frames, the controller 5 applies
a voltage of -15 V with the voltage Vcom as a reference to
the pixel electrode lOld of the pixel P(l,l), and decrements
the value of the remaining number-of-times storage region
B(l,l) and decrements the value of the number-of-times
difference storage region D(l,l).
[0079]
57
(Second operation example of the second embodiment)
Next, an operation when the content of the VRAM 3 is
changed before the value of the remaining number-of-times
storage region becomes 0 will be described with reference to
Fig. 18. Fig. 18 is also a view showing the content of each
storage region corresponding to the pixel P (1,1) . In addition,
since the operation in first to fourth frames in Fig. 18 is
the same as the operation in the first to fourth frames in
Fig. 18, explanation thereof will be omitted.
When the buffer A(1,1) is rewritten from 0 to 5 before
the start of the fifth frame, the controller 5 performs the
processing shown in Fig. 14 before the start of the frame
period. Here, when the pixel P(l,l) is focused, the
controller 5 writes 5 in the remaining number-of-times
storage region B(l,l) in step SA5, and writes 5 in the planned
image storage region E(l,l).
[0080]
Before the value of the remaining number-of-times
storage region B(l,l) regarding the pixel P(l,l) becomes 0,
the controller 5 determines NO in step SA3 and determines NO
in step SA4 if 5 (white) is written in the buffer A(l,l) as
the gradation value of the pixel 110 before the fifth frame.
In addition, since the value of the buffer A(1,1) is 5 (YES
in step SA7) and the value of the number-of-times difference
storage region D(l,l) is 2, the controller 5 writes 5 in the
58
remaining number-of-times storage region B(l,l) in step SA5,
and writes 5 in the planned image storage region E(l,l) in
step SA6.
[0081]
Then, in the fifth to ninth frames, the controller 5 sets
the voltage of the pixel electrode lOld of the pixel P(l,l)
to -15 V with the voltage Vcom as a reference. When the value
of the remaining number-of-times storage region B(l,l)
becomes 0 (tenth frame), the controller 5 sets the voltage
of the pixel electrode lOld of the pixel P(l,l) to the same
voltage as the voltage Vcom.
[0082]
Then, when 0 (black) is written in the buffer A(l,l) as
the gradation value of the pixel 110 before the eleventh frame,
the controller 5 sets the voltage of the pixel electrode lOld
of the pixel P(l,l) to +15 V with the voltage Vcom as a
reference until the value of the remaining number-of-times
storage region B(i,j) becomes 0. Then, the controller 5 sets
the voltage of the pixel electrode lOld of the pixel P(l,l)
to +15 V with the voltage Vcom as a reference until the value
of the number-of-times difference storage region D(i,j)
becomes 5. Then, when 5 (white) is written in the buffer
A(l,l) as the gradation value of the pixel 110 before the
twentieth frame, the controller 5 sets the voltage of the
pixel electrode lOld of the pixel P(l,l) to -15 V with the
59
voltage Vcom as a reference until the value of the remaining
number-of-times storage region B(l,l) becomes 0, in the same
manner as in the frames from the tenth frame shown in Fig.
17.
[0083]
(Third operation example of the second embodiment)
Next, a case where the operation of changing the content
of the buffer A(l,l) is repeated before the value of the
remaining number-of-times storage region B(l,l) becomes 0
will be described with reference to Fig. 19. Fig. 19 is also
a view showing the content of each storage region
corresponding to the pixel P(l,l). In addition, since the
operation in first to twelfth frames in Fig. 19 is the same
as the operation in the first to twelfth frames in Fig. 18,
explanation thereof will be omitted.
[0084]
When 5 (white) is written in the buffer A(1,1) as the
gradation value of the pixel 110 before the thirteenth frame,
the controller 5 performs the same operation as in the fifth
to ninth frame for frames from the thirteenth frame. In
addition, when 0 (black) is written in the buffer A(1,1) as
the gradation value of the pixel 110 before the nineteenth
frame, the controller 5 performs the same operation as in the
third and fourth frames for the nineteenth and twentieth
frames.
60
t *
[0085]
Then, when 5 (white) is written in the buffer A(l,l) as
the gradation value of the pixel 110 before the twenty-first
frame, the controller 5 determines NO in step SA3 and
determines NO in step SA4. In addition, since the value of
the buffer A(1,1) is 5 (YES in step SA7), the controller 5
determines the value of the number-of-times difference
storage region D(l,l). In this case, since the value of the
number-of-times difference storage region D(l,l) is -4, the
controller 5 determines YES in step SA8 and does not update
the content of the planned image storage region E(l,l).
[0086]
Then, in a subsequent frame period, the controller 5
performs processing in step SB5 since the value of the buffer
A(i,j) is 5. First, since the value of the buffer A(l,l) is
different from the value of the planned image storage region
E(l,l) (NO in step SD1), the controller 5 sets the data line
114 on the first column to +15 V with the voltage Vcom as a
reference (step SD2) and then increments the value of the
J number-of-times difference storage region D(l,l) to set it
i
to -3. Then, the controller 5 determines whether or not the
value of the number-of-times difference storage region D(l,l)
is 5. In this case, since the value of the number-of-times
difference storage region D(l,l) is -3, the controller 5
determines NO in step SD5 and the value of the planned image
61
*
storage region E(l,l) is held as 0 as it is.
Then, when the scanning line 112 on the first row is
driven (step SB7), a voltage of +15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld of the
pixel on the first row and the first column, such that black
electrophoretic particles move toward the common electrode
layer 103b even though the value of the buffer A(1,1) is 5
indicating the white as the gradation of a pixel.
[0087]
In the twenty-second to twenty-eighth frames, the
controller 5 performs the same operation as in the
twenty-first frame for the pixel P(l,l). In the twenty-ninth
frame, the value of the buffer A(l,l) is different from the
value of the planned image storage region E(l,l) (NO in step
SD1). Accordingly, the controller 5 sets the data line 114
on the first column to +15 V with the voltage Vcom as a
reference (step SD2) and then increments the value of the
number-of-times difference storage region D(l,l) to set it
to 5. Then, since the value of the number-of-times difference
storage region D(l,l) is 5 (NO in step SD5), the controller
| 5 overwrites the value of the planned image storage region
E(l,l) with 5 which is a value of the buffer A (1,1) , and writes
5 in the remaining number-of-times storage region B(l,l).
[0088]
In the thirtieth frame, the controller 5 performs
I
| 62
!
*
processing in step SB5 since the value of the buffer A(l,l)
is 5. Since the value of the buffer (1,1) and the value of
the planned image storage region E(l,l) are the same and the
value of the remaining number-of-times storage region B(l,l)
is not 0, the controller 5 performs processing in steps SD8
to SD10. That is, a voltage of -15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld of the
pixel on the first row and the first column. Then, until the
thirty-fourth frame, the controller 5 applies a voltage of
-15 V with the voltage Vcom as a reference to the pixel
electrode lOld of the pixel P(l,l).
[0089]
(Fourth operation example of the second embodiment)
Next, a case where the operation of changing the content
of the buffer A(1,1) is repeated before the value of the
remaining number-of-times storage region B(l,l) becomes 0
will be described with reference to Fig. 20. Fig. 20 is also
a view showing the content of each storage region
corresponding to the pixel P(l,l).
[0090]
First, in the first frame shown in Fig. 20, the buffer
A(l,l) is 0, the gradation value storage region C(l,l) is 0,
and the remaining number-of-times storage region B(l,l) and
the number-of-times difference storage region D(l,l) are 5.
Here, until the third frame starts, the voltage applied to
63
»
• *
the pixel electrode lOld is the same as the voltage Vcom, and
the value of each storage region does not change.
[0091]
Then, when the buffer A(l,l) is rewritten from 0 to 5
before the start of the third frame and the value of the buffer
A(l,l) is different from the value (0) of the planned image
storage region E(l,l) before the start of the third frame (NO
in step SA3), the controller 5 determines whether or not the
remaining number-of-times storage region B(l,l) is 0. When
the remaining number-of-times storage region B(l,l) is 0 at
the time before the start of the third frame as shown in Fig.
j
20 (YES in step SA4) , the controller 5 writes 5, as the number
of times of voltage application required to change the
gradation of the pixel P(l,l) from 0 to 5, in the remaining
number-of-times storage region B(l,l) (step SA5) . Then, the
controller 5 overwrites the value of the planned image storage
region E(i,j) with 5 which is a value of the buffer A(i,j)
(step SA6).
[0092]
In a subsequent frame period, the controller 5 drives
the scanning line driving circuit 130 and the data line
driving circuit 140. Since the value of the buffer A(1,1)
is 5 (NO in step SB3), the value of the buffer A(l,l) is the
same as the value of the planned image storage region E(l,l)
(YES in step SD1), and the value of the remaining
64
number-of-times storage region B(l,l) is 5 (NO in step SD7),
the controller 5 decrements the value of the remaining
number-of-times storage region B(l,l) to set it to 4 (step
SD8). The controller 5 sets the data line 114 on the first
column to -15 V with the voltage Vcom as a reference (step
SD9), and then decrements the value of the number-of-times
difference storage region D(l,l) to set it to 4 (step SD10).
[0093]
Before the value of the remaining number-of-times
storage region B(l,l) regarding the pixel P(l,l) becomes 0,
the controller 5 determines NO in step SA3 and determines NO
in step SA4 if 0 (black) is written in the buffer A(l,l) as
the gradation value of the pixel 110 before the fifth frame.
In addition, since the value of the buffer A(1,1) is 0 (NO
in step SA7) and the value of the number-of-times difference
storage region D(l,l) is 3, the controller 5 writes 5 in the
remaining number-of-times storage region B(l,l) in step SA5,
and writes 0 in the planned image storage region E(l,l) in
step SA6.
[0094]
Then, in the fifth to ninth frames, the controller 5 sets
the voltage of the pixel electrode lOld of the pixel P(l,l)
to +15 V with the voltage Vcom as a reference. When the value
of the remaining number-of-times storage region B(l,l)
becomes 0, the controller 5 sets the voltage of the pixel
I
65
»
electrode 10Id of the pixel P(l,l) to the same voltage as the
voltage Vcom.
[0095]
Then, when 5 (white) is written in the buffer A (1,1) as
the gradation value of the pixel 110 before the eleventh frame,
the controller 5 sets the voltage of the pixel electrode lOld
of the pixel P(l,l) to -15 V with the voltage Vcom as a
reference in the eleventh and twelfth frames, in the same
manner as in the third and fourth frames.
Then, when 0 (black) is written in the buffer A (1,1) as
i
the gradation value of the pixel 110 before the thirteenth
frame, the controller 5 determines NO in step SA3 and
determines NO in step SA4. In addition, since the value of
the buffer A(l,l) is 0 (NO in step SA7), the controller 5
determines the value of the number-of-times difference
storage region D(l,l). In this case, since the value of the
number-of-times difference storage region D(l,l) is 7, the
controller 5 determines YES in step SA11 and does not update
the content of the planned image storage region E(l,l).
[0096]
Then, in a subsequent frame period, the controller 5
performs processing in step SB4 since the value of the buffer
A(i,j) is 0. First, since the value of the buffer A(i,j) is
different from the value of the planned image storage region
E(i,j) (NO in step SE1), the controller 5 sets the data line
66
i
t
114 on the first column to -15 V with the voltage Vcom as a
reference (step SE2) and then decrements the value of the
number-of-times difference storage region D(l,l) to set it
to 6. Then, the controller 5 determines whether or not the
value of the number-of-times difference storage region D(l,l)
is 0. In this case, since the value of the number-of-times
difference storage region D(l,l) is 6, the controller 5
determines NO in step SE4 and the value of the planned image
storage region E(l,l) is held as 5 as it is.
Then, when the scanning line 112 on the first row is
driven (step SB7), a voltage of -15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld of the
pixel on the first row and the first column, such that white
electrophoretic particles move toward the common electrode
layer 103b even though the value of the buffer A(1,1) is 0
indicating the black as the gradation of a pixel.
[0097]
Then, until the nineteenth frame in which the value of
the number-of-times difference storage region D(i,j) becomes
0, a voltage of -15 V with the voltage Vcom as a reference
is applied to the pixel P(l,l). In the nineteenth frame, the
controller 5 determines YES in step SE4, and writes 5 in the
remaining number-of-times storage region B(i,j), and
overwrites the value of the planned image storage region
E(i,j) with the value of the buffer A(i,j).
! 67
In the twentieth frame, the controller 5 performs
processing in step SB4 since the value of the buffer A(l,l)
is 0. Since the value of the buffer(1,1) and the value of
the planned image storage region E(l,l) are the same and the
value of the remaining number-of-times storage region B(l,l)
is not 0, the controller 5 performs processing in steps SE7
to SE9. That is, a voltage of +15 V with the voltage Vcom
as a reference is applied to the pixel electrode lOld on the
first row and the first column. Then, until the twenty-fourth
frame, the controller 5 applies a voltage of +15 V with the
voltage Vcom as a reference to the pixel electrode lOld of
the pixel P(l,1).
[0098]
•
Thus, even if an operation for rewriting to white is
repeated while a pixel is being rewritten in black, the
v voltage applied to the pixel electrode lOld is controlled.
Accordingly, a large difference does not occur between the
number of times of application of a positive voltage with the
common electrode layer 103b as a reference and the number of
times of application of a negative voltage with the common
electrode layer 103b as a reference. As a result, it is
possible to suppress deterioration of the pixel 110.
[0099]
[Electronic apparatus]
Next, an example of an electronic apparatus to which the
[ 68
I
t
electro-optical device 1 according to the embodiment is
applied will be described. Fig. 21 is a view showing the
appearance of an electronic book reader using the
electro-optical device 1. An electronic book reader 2000
includes a plate shaped frame 2001, buttons 9A to 9F, the
electro-optical device 1 according to the above-described
embodiment, the control unit 2, the VRAM 3, and the RAM 4.
In the electronic book reader 2000, the display area 100 is
exposed. In the electronic book reader 2000, the content of
i
electronic book is displayed in the display area 100, and the
page of the electronic book is turned over by operating the
buttons 9A to 9F.
In addition to this, examples of an electronic apparatus
to which the electro-optical device 1 according to the
embodiment described above can be applied may include a
timepiece, electronic paper, an electronic diary, a
calculator, a mobile phone, and the like.
[0100]
[Modification examples]
While the embodiments of the invention have been
described, the invention is not limited to the above
embodiments and various modifications may also be made. For
example, the invention may also be performed by modifying the
above-described embodiments as follows. In addition, the
above-described embodiments and the following modification
69
* *
• «
examples may be combined.
[0101]
In the invention, the number of times of voltage
application when rewriting a pixel may be changed according
to the temperature around the pixel 110. For example, the
number of times of voltage application may be reduced when
the temperature is high, and the number of times of voltage
application may be increased when the temperature is low. In
addition, when the number of times of voltage application when
rewriting a pixel is changed according to the temperature,
the value used in determination processing of steps SA8, SC6, j
i
and SD5 and the like in the first embodiment may be changed
according to the temperature. In addition, when the number
of times of voltage application when rewriting a pixel is
changed according to the temperature, the value used in
determination processing of steps SA8, SAll, SE4, and SD5 and
the like in the second embodiment may be changed according
to the temperature.
[0102]
In the invention, a case where the number of times of
voltage application from white to black is larger than the
number of times of voltage application from black to white
(for example, the number of times of voltage application from
black to white is 3, and the number of times of voltage
application from white to black is 5) may occur depending on
70
i
. *
the material of electrophoretic particles.
In this case, in the first embodiment, processing shown
in Figs. 22 to 25 is performed instead of the processing shown
in Figs. 7 to 10.
In processing shown in Fig. 22, the process proceeds to
step SA5 if the value of the buffer A(i,j) is 5 (white) in
step SA7A, and the process proceeds to step SA8A if the value
is 0 (black). Then, in step SA8A, the process proceeds to
step SA9 if the value of the number-of-times difference
storage region D(i,j) is equal to or larger than 4, and the
process proceeds to step SA5 if the value of the
number-of-times difference storage region D(i,j) is smaller
than 4.
In addition, in processing shown in Fig. 23, the process
proceeds to step SB4A if the value of the buffer A(i,j) is
5 (white) in step SB3A, and the process proceeds to step SB5A
if the value is 0 (black). In addition, processing shown in
Fig. 24 is performed in step SB4A, and processing shown in
Fig. 25 is performed in step SB5A.
Moreover, in the processing shown in Fig. 24, the data
line on the j-th column is set to -15 V with the voltage Vcom
as a reference in step SC3A, and the value of the
number-of-times difference storage region D(i,j) is
decremented in step SC4A. Then, in the processing shown in
Fig. 24, it is determined whether or not the value of the
i
71
i
4 »
number-of-times difference storage region D(i,j) is larger
than 0 in step SC6A. The process proceeds to step SC3A if
the value of the number-of-times difference storage region
D(i,j) is larger than 0, and the processing shown in Fig. 24
is ended if the value of the number-of-times difference
storage region D(i,j) is equal to or smaller than 0.
Moreover, in the processing shown in Fig. 25, the data
line on the j-th column is set to -15 V with the voltage Vcom
as a reference i*n step SD2A, and the value of the
number-of-times difference storage region D(i,j) is
decremented in step SD3A. If the value of the number-of-times
difference storage region D(i,j) is 0 in step SD5A, the
process proceeds to step SD6. If the value is 5, the
i
i
processing shown in Fig. 25 is ended. Moreover, in the
processing shown in Fig. 25, the data line on the j-th column
is set to +15 V with the voltage Vcom as a reference in step
SD9A, and the value of the number-of-times difference storage
region D(i,j) is incremented in step SD10A.
According to this configuration, even if an operation
for rewriting to black is repeated while a pixel is being
rewritten in white, the voltage applied to the pixel electrode
lOld is controlled. Accordingly, a large difference does not
occur between the number of times of application of a positive
voltage with the common electrode layer 103b as a reference
and the number of times of application of a negative voltage
i 72
* *
with the common electrode layer 103b as a reference. As a
result, it is possible to suppress deterioration of the pixel
110.
[0103]
In the embodiment described above, the electro-optical
device including the electrophoretic layer 102 has been
described as an example. However, the invention is not
limited to this. Any electro-optical device may be used as
long as the writing for changing the display state of a pixel
from the first display state to the second display state is
performed by a writing operation in which a voltage is applied
j
multiple times. For example, it is also possible to use an
electro-optical device using the electronic liquid powder.
Reference Signs List
[0104]
1: ELECTRO-OPTICAL DEVICE, 2: CONTROL UNIT, 3: VRAM, 4: RAM,
5: CONTROLLER, 9A to 9F: BUTTONS, 10: DISPLAY UNIT, 100:
DISPLAY AREA, 101: FIRST SUBSTRATE, 101a: SUBSTRATE, 101b:
ADHESIVE LAYER, 101c: CIRCUIT LAYER, lOld: PIXEL ELECTRODE,
102: ELECTROPHORETIC LAYER, 102a: MICROCAPSULE, 102b: BINDER,
103: SECOND SUBSTRATE, 103a: FILM, 103b: COMMON ELECTRODE
LAYER, 110: PIXEL, 110a: TFT, 110b: DISPLAY ELEMENT, 110c:
AUXILIARY CAPACITOR, 112: SCANNING LINE, 114: DATA LINE, 501:
NUMBER-OF-TIMES DIFFERENCE CALCULATING SECTION, 502: VOLTAGE
I
I
i 73
4 *
CONTROL SECTION, 503: APPLICATION NUMBER-OF-TIMES
DETERMINING SECTION, 2000: ELECTRONIC BOOK READER, 2001:
FRAME, A(i,j): BUFFER, B, B(i,j): REMAINING NUMBER-OF-TIMES
STORAGE REGION, C, C(i,j): GRADATION VALUE STORAGE REGION,
D, D(i,j): NUMBER-OF-TIMES DIFFERENCE STORAGE REGION, E,
E(i,j): PLANNED IMAGE STORAGE REGION
I
I 74

• •
a *
CLAIMS
" [Claim 1]
A controller of an electro-optical device which
includes a display unit with a plurality of pixels and in which
a writing operation of changing the pixel from first gradation
to second gradation and a writing operation of changing the
pixel from the second gradation to the first gradation are
performed by an operation of applying a voltage to the pixel
multiple times, the controller comprising:
a number-of-times difference calculating section that
calculates a difference between the number of times of
application of a first voltage, which is applied to change
the pixel to the first gradation, and the number of times of
application of a second voltage, which is applied to change
the pixel to the second gradation; and
a voltage control section that applies the first voltage
or the second voltage to the pixel until the difference
becomes a predetermined value when the difference regarding
the pixel is not the predetermined value at a predetermined
timing and that, when changing a gradation of the pixel,
starts a new operation of applying a voltage to the pixel
multiple times even in the middle of the writing operation.
[Claim 2]
The controller of an electro-optical device according
to Claim 1,
! 75
• »
wherein when the pixel has the first gradation and the
difference regarding the pixel is not the predetermined value
after the writing operation ends, the voltage control section
applies the first voltage to the pixel until the difference
becomes the predetermined value.
[Claim 3]
The controller of an electro-optical device according
to Claim 1 or 2,
wherein when the pixel has the second gradation and the
difference regarding the pixel is not the predetermined value
after the writing operation ends, the voltage control section
applies the second voltage to the pixel until the difference
becomes the predetermined value.
[Claim 4]
The controller of an electro-optical device according
to any one of Claims 1 to 3,
wherein when an absolute value of the difference is
equal to or larger than a threshold value when a writing
operation of setting the pixel to the first gradation starts
in the middle of a writing operation of setting the pixel to
the second gradation, the voltage control section applies the
second voltage until the difference becomes the predetermined
value and then starts application of the first voltage.
[Claim 5]
The controller of an electro-optical device according
i
| 76
j
l
i
« *
*
to any one of Claims 1 to 4,
wherein when an absolute value of the difference is
equal to or larger than a threshold value when a writing
operation of setting the pixel to the second gradation starts
in the middle of a writing operation of setting the pixel to
the first gradation, the voltage control section applies the
first voltage until the difference becomes the predetermined
value and then starts application of the second voltage.
[Claim 6]
The controller of an electro-optical device according
to any one of Claims 1 to 5, further comprising:
an application number-of-times determining section
that, when changing the gradation of the pixel, determines
the number of times of application on the basis of the
gradation of the pixel before the change, the gradation of
the pixel after the change, and a table in which the number
of times of application of a voltage for gradation change from
the gradation before the change to the gradation after the
change matches the gradation before the change and the
gradation after the change.
[Claim 7]
The controller of an electro-optical device according
to any one of Claims 1 to 6,
wherein the number of times of application of the first
voltage applied to change the pixel to the first gradation
I
i
| 77
4 »
is different from the number of times of application of the
second voltage applied to change the pixel to the second
gradation.
[Claim 8]
A control method of an electro-optical device which
includes a display unit with a plurality of pixels and in which
a writing operation of changing the pixel from first gradation
to second gradation and a writing operation of changing the
pixel from the second gradation to the first gradation are
performed by an operation of applying a voltage to the pixel
multiple times, the control method comprising:
a step of calculating a difference between the number
i
of times of application of a first voltage, which is applied
to change the pixel to the first gradation, and the number
of times of application of a second voltage, which is applied
to change the pixel to the second gradation; and
a step of applying the first voltage or the second
voltage to the pixel until the difference becomes a
predetermined value when the difference regarding the pixel
is not the predetermined value at a predetermined timing and
starting a new operation of applying a voltage to the pixel
multiple times even in the middle of the writing operation
when changing a gradation of the pixel.
[Claim 9]
An electro-optical device which includes a display unit
|
! 78
!.
* »
^^ with a plurality of pixels and in which a writing operation
of changing the pixel from first gradation to second gradation
and a writing operation of changing the pixel from the second
gradation to the first gradation are performed by an operation
of applying a voltage to the pixel multiple times, the
electro-optical device comprising:
a number-of-times difference calculating section that
calculates a difference between the number of times of
application of a first voltage, which is applied to change
the pixel to the first gradation, and the number of times of
application of a second voltage, which is applied to change
the pixel to the second gradation; and
a voltage control section that applies the first voltage
or the second voltage to the pixel until the difference
becomes a predetermined value when the difference regarding
the pixel is not the predetermined value at a predetermined
timing and that, when changing a gradation of the pixel,
starts a new operation of applying a voltage to the pixel
multiple times even in the middle of the writing operation.
[Claim 10]
An electronic apparatus comprising the electro-optical
device according to Claim 9.