DESCRIPTION
Title of Invention: CONTROL DEVICE, DISPLAY DEVICE, AND
METHOD OF CONTROLLING DISPLAY DEVICE
Technical Field
[00011
The present invention relates to a technique for
rewriting an image to a desired display state through
several voltage applications.
Background Art
[ 0 0 0 2 ]
In a display device such as an electrophoretic
display device, there is a device that performs one
rewrite using a plurality of frames. Such a rewriting is
performed when a display element requires a relatively
lcng time for a change of display state (that is, a
gradation! or the like. When such a rewriting is
performed, if one rewriting is not finished (that is, if
the time for multiple frames has not elapsed), the
display element cannot start the next rewriting.
PTL 1 discloses a technique for rewriting an image
for each partial region by a pipeline processi.ng in a
display device such as an electrophoretic display device.
This permits the rewriting to start in a region where the
rewriting is not performed without relying on the
rewriting of other regions. Thus, in some cases, it is
possible to reduce the time required for the rewriting as
compared to the case of rewriting the whole image.
Citation List
Patent Literature
[0004]
PTL 1: JP-A-2009-251615
Summary of Invention
Technical Problem
[00051
In the case of the technique described in PTL 1, in
order to rewrite a plurality of regions in parallel, it
is necessary to have as many pipelines as there are
regions. In other words, in the technique described in
PLT 1, the number of regions capable of being rewritten
in parallel is limited by the number of pipelines.
Furthermore, in the technique described in PLT 1,
when a region, where a rewriting target exists, overlaps
with another region, if the rewriting of the region where
the rewriting target exists is not finished, it is
difficult to start the rewriting of another region.
One of objects of the invention is to increase the
regions where a rewriting operation can start, without
relying on the previous rewriting operation, in a display
device that rewrites an image through several voltage
applications.
Solution to Problem
[0006]
The invention provides a control device that
controls the driving of a display device which changes
display states of a plurality of pixels from a first
display state to a second display state by a rewriting
operation of applying a driving voltage several times,
the control device including a decision portion that
decides whether or not the rewriting operation is
performed for each pixel; and a control portion that
applies the driving voltage several times in a pattern,
in which the driving voltages of each time are determined
depending on the first display state and the second
display state, to the pixel decided when performing the
rewriting operation by the decision portion and starts
the rewriting operation, wherein, in a case where a
previous rewriting operation is not performed on the
pixel decided when performing the rewriting operation by
the decision portion, the control portion starts the
rewriting operation, and in a case where the previous
rewriting operation is performed on the pixel, the
control portion starts the next rewriting operation after
the previous rewriting operation is finished.
According to the control device, it is possible to
control the starting of the rewriting operation of any
pixel without relying on the rewriting operation state of
another pixel.
[00071
In a preferable aspect, in the control device, the
number of applications of the driving voltage in one
rewriting operation differs depending on at least one of
the first display state and the second display state.
According to this aspect, it is possible to rapidly
finish the previous rewriting operation and rapidly start
the next rewriting operation.
[ 0 0 0 8 ]
In another preferable aspect, the control device
includes a first recording portion that records data for
specifying the number of applications of the driving
voltage in the one rewriting operation for each pixel,
and the control portion decides whether or not the
previous rewriting operation is performed, depending on
whether or not the number specified by the data recorded
by the first recording portion reaches a scheduled
number.
According to this aspect, it is possible to start
the next rewriting operation from the pixel to which the
driving voltage is applied by a required number.
[0009]
In Still another preferable aspect, when the
previous rewriting operation is performed on the pixel
for which it is decided that the rewriting operation is
to be performed, the decision portion performs the
decision again after the previous rewriting operation is
finished, and, when it is decided that the rewriting
operation is not performed by the repeated decision by
the decision portion, the control portion does not
perform the rewriting operation.
According to this aspect, it is possible to omit an
unnecessary rewriting operation so as not to be
performed
[0010]
In yet another preferable aspect, the control device
includes an acquisition portion that reads and acquires
an image data from a first storage region which stores
the image data showing display states to be displayed on
each pixel by the plurality of pixels'; and a second
recording portion that records a scheduled data, which
shows a scheduled display state to be displayed on each
pixel when the rewriting operation is finished, by each
pixel, the decision portion decides the pixel, in which
the display state shown by the image data acquired by the
acquisition portion is not consistent with the display
state shown by the scheduled data, as a pixel in which
the rewriting operation is performed.
According to this aspect, it is possible to easily
specify the pixel in which the rewriting operation is
performed.
[OOll]
In still yet another preferable aspect, the second
recording portion rewrites the scheduled data for the
pixel in which the rewriting operation is started by the
control portion so that the image data becomes new
scheduled data.
According to this aspect, the pixel, for which the
rewriting operation does not need to be performed after
the rewriting operation is finished, can be prevented
from being decided as a pixel for which the rewriting
operation is performed.
[00121
The invention also provides a display device that
includes the control device, and a display portion which
has a plurality of pixels and performs the rewriting
operation depending on the control by the control device.
According to the display device, it is possible to
start the next rewriting operation from the pixel to
which the driving voltage is applied the required number
of times, and improve the exterior display speed for a
user.
[0013]
In a preferable aspect, in the display device, the
pixels include a display element having a memory
property.
According to this aspect, it is possible to suppress
the electric power that is required for the maintenance
of the display state of the pixel in which the rewriting
operation does not need to be performed.
[00141
The invention further provides a control method by a
section that controls the driving of a display device
which changes the display states of a plurality of pixels
from a first display state to a second display state by a
rewriting operation of applying a driving voltage several
times, the method including a decision step of deciding
whether or not the rewriting operation is performed for
each pixel, and a controlling step of applying a driving
voltage is applied several times in a pattern, in which
the driving voltages of each time are determined
depending on the first display state and the second
display state, to the pixel decided when performing the
rewriting operation in the decision and starting the
rewriting operation, wherein, in the controlling step, in
a case where a previous rewriting operation is not
performed on the pixel decided when performing the
rewriting operation in the decision, the rewriting
operation is started, and in a case where the previous
rewriting operation is performed on the pixel, the next
rewriting operation is started after the previous
rewriting operation is finished.
According to the control method, it is possible to
start the next rewriting operation from the pixel to
which the driving voltage is applied by a required
number, and improve an exterior display speed of a user.
Brief Description of Drawings
[Fig. 11 Fig. 1 is a block diagram that shows a main
configuration of a display device.
[Fig. 21 Fig. 2 is a diagram that shows a wave form
table stored in a ROM.
[Fig. 31 Fig. 3 is a schematic diagram that shows a
gradation variation realized by a wave form table.
[Fig. 41 Fig. 4 is a diagram that shows a circuit
configuration of a display portion.
[Fig. 51 Fig. 5 is a diagram that shows an
equivalent circuit of a pixel.
[Fig. 61 Fig. 6 is a partial cross-sectional view
that shows a configuration of a display panel.
[Fig. 71 Fig. 7 is a functional block diagram that
shows a functional configuration of a controller.
[Fig. 81 Fig. 8 is a flow chart that shows the
processing to be executed by a controller.
[Fig. 91 Fig. 9 is a flow chart that shows a
preparation processing.
[Fig. 101 Fig. 10 shows diagrams that show
electronic equipment to which the display device
according to the invention is applied.
Description of Embodiments
[0016]
Fig. 1 is a block diagram that shows a main
configuration of a display device which is an embodiment
of the invention. As shown in Fig. 1, a display device
100 includes a CPU (Central Processing Unit) 110, a
display portion 120, a controller 130, a ROM (Read Only
Memory) 140, and a RAM (Random Access Memory) 150.
Furthermore, the RAM 150 includes VMM (Video RAM) 151.
Additionally, although it is not shown in the drawings,
the display device 100 may include a section (a so-called
memory card or the like) that stores image data or a
section (a key, a touch screen or the like) that receives
an operation of a user, and may include a section (an
interface) that acquires the data from such sections.
[0017]
The CPU 110 is a section to control the operation of
the display device 100. The CPU 110 performs the reading
or the writing of the data by executing the program
stored in advance. The CPU 110 has a function of
sequentially writing the image data on the VRAM 151.
Here, the image data is data of a screen unit that shows
the display states of each pixel. The image data shows
the display state to be displayed on each pixel, but is
sometimes not necessarily consistent with the actual
display state.
[0018]
The display portion 120 is a section to display the
image by the plurality of pixels. In the present
embodiment, the display portion 120 is a display section
of an electrophoretic type, and uses an electrophoretic
element in the display element. Herein, the
electrophoretic element refers to a display element that
has a memory property (a storage property) . Furthermore,
the memory property refers to a property that tries to
keep the display state even if the voltage is not applied
when a predetermined display state is generated by the
application of the voltage, and is also referred to as
bistability. The display state of the electrophoretic
element includes two certain kinds of display states and
a display state of a half tone. Two kinds of display
states typically means combinations having a relatively
large difference of reflectivity of light. However, as
long as the combination is one in which the color is
visually or mechanically distinguishable, the combination
is not particularly limited. In the present embodiment,
the display state of the maximum reflectivity is called
\'white1', and the display state of the minimum
reflectivity is called "black" . Thus, the display state
of the halftone is gray. Furthermore, in the present
embodiment, the state, in which the image is not yet
written such as immediately after putting the power
source, is white.
[00191
The controller 130 is a section to control the
driving of the display portion 120. The controller 130
corresponds to an example of the control device according
to the invention. The controller 130 causes the display
portion 120 to perform an operation (hereinafter,
referred to as "rewriting operation") of applying a
predetermined driving voltage to a display element using
the data stored in the RON 140 or the RAM 150. The
rewriting operation of the present embodiment is
performed by applying a plurality of driving voltages.
That is, a first rewriting operation is performed by
several applications of the voltage. In addition, the
number or the pattern of applying the driving voltage
differs depending on the display states of the pixel to
be targeted.
[0020]
The ROM 140 or the RAM 150 is a section that stores
the data. The ROM 140 stores a plurality of wave form
tables that shows the pattern of the driving voltage to
be applied. Herein, the wave form refers to a temporal
change of the gradation of the pixel, but is not limited
to an undulating one such as a wave. In addition, the
ROM 140 may be a storage section that is not read-only
but is rewritable, such as EEPROM (Electronically
Erasable and Programmable ROM) and can be substituted for
a storage unit (RAM or the like) other than ROM.
[00211
Fig. 2 is a diagram that shows a wave form table
stored in the ROM 140. The wave form table of the
present embodiment is a data group in which an index
corresponds to the driving voltage value. The index is
data for specifying the number (hereinafter, referred to
as "number of applications") of applications of the
driving voltage during one rewriting operation, and is
also the data for specifying the driving voltage of each
time during the rewriting operation in the wave form
table. The index of the present embodiment is a number
by which the number of applications at that time is
reduced from the total number of the required
applications for the one rewriting operation specified by
the wave form table. In addition, the number of
applications required for the one rewriting operation
differs depending on at least one of the gradation of the
pixel before the rewriting and the gradation of the pixel
after the rewriting. Furthermore, the driving voltage
value is data that shows the driving voltage. The
driving voltage values of the present embodiment are
three kinds of Vb, Vw, and Vn. The driving voltage value
Vb is a voltage value in which the display state of the
pixel becomes closer to black, and the driving voltage
value Vw is a voltage value in which the display state of
the pixel becomes closer to white. Furthermore, the
driving voltage value Vn is a voltage value in which a
potential difference is not generated in the pixel. In
addition, the number of applications required for the one
rewriting operation is the same as the number of frames
required for the one rewriting operation.
[0022]
The wave form table shown in Fig. 2 is a case where
the number of gradations is four. Herein, the gradation
value of the pixel is indicated by a value in which the
reflection density of the pixel is normalized, black is
indicated by 0%, and white is indicated by 100%. Thus,
the pixel having the gradation value of 33% is gray (dark
gray) of gray near black, and the pixel having the
gradation value of 67% is gray (light gray) of gray near
white. Four gradations are realized by the wave form
table of Fig. 2 (black, dark gray, light gray, and
white)
[00231
For example, a wave form table T1 shown in Fig. 2
shifts the gradation of the pixel from the state of 0% to
the state of 33%) applies the driving voltage value Vw to
the first and second rewriting operations, and applies
the driving voltage value Vn to the third rewriting
operation to finish the rewriting operation.
Hereinafter, the gradation value of the initial state of
the pixel is referred to as the "initial value" and the
gradation value immediately after the rewriting operation
is referred to as the "objective value". For example,
the wave form table T1 is a wave form table in which the
initial value of the grada~ion value is 0%. and the
objective value is 33%. The respective wave form tables
car. be made to correspond to the initial value and the
objective value in advance, respectively.
LO0241
In additior., the number of applications (that is.
the maximum value of the index) required for the one
rewriting operation is not limited to that shown. For
example, the wave form table of the case of using the
display element of a relatively gradual gradat i on change
may be one in which the number of applications 1s
incr+ased so that the one rewriting operat-ion takes even
more time. Furthermore. by increasing the number of
applications required for the one rewriting operation,
the number of gradations can also be increased.
[00251
Fig. 3 is a schematic diagram that shows a gradation
change realized by a voltage application according Lo the
wave form table. In addition, in Flg. 3, for convenience
of explanatlon, the number of applications per rewriting
operation is 21. and the gradation change is linearly
shown. However, the actual gradation change differs
depending on the responsi~reness or the like of the
display element to the application voltage, and in some
cases, a part or all of them is curved. Furrhermore, the
time required for the cha.nge of the gradation from black
to white is not necessarily the same as the time required
for the change from white to black. If the wave f0r.m
table is used, various wave forms can be realized without
being limited to that shown.
[0026]
The example shown in Fig. 3 is an example of the
wave form of the gradation change when the gradation
value of the pixel is changed to 67% (light gray) in a
case where the gradation valce before the rewriting
operation is 33% (dark gray) . In. this case, the
controller 130 applies the voltage so that the gradation
of the pixel temporarily beccjmes black, then applies the
voltage so a s . to make the gradation become white, and
applies the voltage so as to inake the gradation become
dark again, thereby realizing the gradation called light
gray. In addition, if the time per frame (hereinafter,
ref erred to as "frame period" j is sufficiently short,
such a gradation change 1,s hardly perceived by the eyes
of a user.
[0027]
The display element such as an electrophoretic
element can form a desired display stat.= by applying a
certain dj.rectisri cf voltage for a certain time.
However, when cne voltage is only applied In one
direction, the reproducibility of the gradation is
insufficient depending on the property of the display
element, and a desired display state cannot be formed,
or, in some cases, a so-called afterimage is displayed.
The controller 130 permits the value of the driving
voltage or the direction thereof for each frame period to
be switched over by the use of the wave form table, which
makes it possible to realize the wave forms of various
shapes and reduce the afterimage or improve the
reproducibility of the gradation. Furthermore, by
suitably setting the wave form table, it is possible to
prevent the voltage applied to the display element from
being biased to one direction of the positi-ve and
negative directions.
[0028]
The RAM 150 stores the scheduled data, a table ID
and the remaining number. The scheduled data is data
that shows a scheduled display state to be displayed on
each pixel when the rewriting operation is finished. The
scheduled data is data that can be rewritten in the pixel
unit. That is, a scheduled data of any pixel is in a
rewritable state if the rewriting operation is not
performed on the pixel. The table ID is data for
specifying the wave form table that is used in the
rewriting operations of each pixel. The ta.ble ID can be
allocated to each of the wave f o r m tables in advance.
The remaining number is a numbe:r by which the number of
applications of that time is reduced from the total
number of applications required for the one rewriting
operation specified by the wave form table shown by the
table ID, and is stored for each pixel. The remaining
number of the present embodiment is the same as the value
in which "1" is reduced from the index of the driving
voltage value finally read from the wave form table,
which is specified by the table ID, by the controller
130. If the remaining number is "0" , it means that the
rewriting operati-on of the corresponding pixel is
finished (or the rewriting operation does not need to be
performed) .
[00291
The VRAM 151 functions as a frame buffer, and
sequentially stores the image data supplied from the CPU
110. The image data can be collectively rewritten in a
screen u n i t , that is, a unit of all the plurality of
pixels that is a target of the driving, unlike1.y the
scheduled data. The VRAM 151 is a memory region where
both of the CPU 110 and the controller 130 can be
accessed. More specifically, the VRAM 1151 is a memory
region whert! the CPU 110 can write t.o and the controller ..
130 can read from. In addition, VRAM 151 may be a part
of the memory region of the RAM 150, but may be a memory
section physically separated from the RAM 150. The VPAM
151 corresponds to an example of the first memory region
according to the present embodiment.
[0030]
Fig. 4 is a diagram that shows a circuit
configuration of the display portion 120. As shown in
Fig. 4, the display portion 120 includes a scanning line
driving circuit 121, a data line driving circuit 122, and
a display panel 123. The controller 130 controls the
driving of the display portion 120 by controlling the
scanning line driving circuit 121 and the data line
driving circuit 122. The control by the controller 130
includes the control of the driving timing of the pixel
[0031]
The scanning line driving circuit 121 selects
scanning lines Y1, Y2, ..., Ym, and supplies the selected
one scanning line with the scanning signal. The data
line driving circuit 122 supplies data lines XI, X2, ..., Xn
with a data slgnal. The data signal is a signal that
becomes any one of three types of electric potentials of
115 V, -15V. and 0 V (that is, the same electric
potential as a common electric potential Vcom) to the
common electric potential Vcom. The electric potential
corresponds to the drivi.ng vcltage value of the wave form
table, +15 V corresponds to Vb, -15.d corresponds to Vw,
and 0 V corresponds to Vn, respectively. In addition,
the number of scanning lines and data lines, that is, the
values of m and n are not particularly limited.
[0032]
The display panel 123 has a plurality of pixels 30
that is arranged in a matrix shape so as to correspond to
the intersection of the data lines X1 to Xn and the
scanning lines Y1 to Ym. The plurality of pixels 30 is
electrically connected to a common electric potential
line 124, and the common electric potential Vcom is
applied from a feeder circuit (not shown). In addition,
although it is described such that the data lines X1 to
Xn are perpendicular to the scanning lines Yl to Ym in
the drawings, the arrangements of the pixels 30 need not
necessarily to be perpendicular to each other.
[0@33]
Fig. 5 is a diagram that shows an equivalent circuit
of the pixels 30. As shown in Fig. 5, the pixel 30
incl~des a transistor 31, a retention volume 32, a pixel
electrode 33, an electrophoretic layer 34, and a counter
electrode 35. The transistor 31 is an element that
functions as a switching element, and is, for example, an
N iype t h l n film transistor. The transistor 31 is
configured so that a gat.^ 2lectrode is electrically
connected to a scanning lj-lle yi !i= 1 to m) , a source
electrode is electrically connected to a data line Xj (j=
1 to n), and a drain electrode is electrically connected
to the retention volume 32 and the pixel electrode 33,
respectively The transistor 31 supplies the retention
volume 32 and the pixel electrode 33 with data signal
at the timing depending on the scanning signal.
[0034]
The retention volume 32 has a pair of electrodes
that face each other via a dielectric film, of which one
electrode is electrically connected to the transistor 31,
and the other electrode is electrically connected to a
ground. The retention volume 32 is connected to the
electrophoretic layer 34 in parallel and can keep the
data signal supplied from the transistor 31 for a certain
period of time.
[0035]
The pixel electrode 33 is an electrode corresponding
to each pixel 30, and the counter electrode 35 is an
electrode that is commonly provided in each pixel 30.
The electric potential of the counter electrode 35 is
connected to the common electric potential 1ir.e 124 and
is kept in the common el..zc;ric potential Vcom.
Meamwhile, the electri pote~tial of the pixel electrode
33 is changed depending on the data slgnal. The
electrophoretic layer 34 is a layer having a plurality of
micro capsules enclosed with electrophoretic particles,
and changes the state depending on the electric potential
difference (that is, the driving voltage) between the
pixel electrode 33 and the counter electrode 35.
[0036]
Fig. 6 is a partial cross-sectional view that shows
a configuration of the display panel 123. As shown in
Fig. 6, the display panel 123 includes a counter
substrate 41, the counter electrode 35, the
electrophoretic layer 34, an adhesion layer 42, the pixel
electrode 33, and the element substrate 43. That is, the
display panel 123 has a configuration in which the
electrophoretic layer 34 is interposed by a pair of
substrates (the counter substrate 41 and the element
substrate 43) . In addition, the display panel 123
constitutes the substrate or the like by a material
having flexibility such as plastic, and may be bent to
some extent, but may use a glass substrate.
[00371
The counter substrate 41 is a transparent substrate
that has a counter electrode 35 provided on one surface.
The counter electrode 35 is a transparent conductive film
formed of lndium tin oxide (ITO) or the like. A user can
perceive the color of the electrophoretic layer 34, that
is, the display state by sighting the display panel 123
from the counter substrate 41 side (an upper part of the
drawing) .
[0038]
The electrophoretic layer 34 includes a plurality of
micro capsules 341 and a binder 342. The micro capsules
341 are spherical capsules enclosed with coloring
particles (also called electrophoretic particles, in the
present embodiment, white particles and black particles)
and a dispersion medium selected depending on the display
states, and is an example of the electrophoretic element.
The coloring particles are enclosed in the micro capsule
341 in a charged state, and are able to move in the
capsule depending on the electric field generated by the
driving voltage. In the present embodiment, the black
particle having a positive electric charge and the white
particle having a negative electric charge are used as
the electrophoretic particles. Of course, it is also
possible to use the black particle having the negative
electric charge and the white particle having the
positive electric charge. The binder 342 is formed of
resin or the like and holds the micro capsule 341 so as
not to be moved. The adhesion layer 42 is a layer for
bonding the electrophoretic layer 34 to the element
substrate 43 side
I00391
The pixel electrode 33 is an electrode that is
provided in a matrix shape in response to the
intersection of the scanning line Yj and the data line
Xi, and the position thereof corresponds to the
arrangement of the pixel 30. The element substrate 43 is
a substrate on which a circuit element constituting the
pixel 30 is mounted in addition to the pixel electrode
33. Although it is not shown, the element substrate 43
has the transistor 31, the retention volume 32, the
scanning line Yj, the data line Xi or the like mounted
thereon.
[0040]
The hardware configuration of the display device 100
is as stated above. Under this configuration, the CPU
110 controls the overall operation of the display device
100. Furthermore, the controller 130 accesses the ROM
140, the KAM 150, and the VRAM 151 depending on the
operation of the CPU 110 to perform the writing (that is,
the recording) and the reading (that is, the acquisition)
of the data, and rewrites the image to be displayed on
the display portion 120. In addition, the writing of the
image data by the CPU 110 to the VRAM 151 is performed
independently from the operation by the controller- 130.
Thus, the CPU 110 is able to rewrite the image data of
the VRAM 151 regardless of the operation conditions of
the controller 130.
[00411
Fig. 7 is a functional block diagram that shows a
functional configuration of the controller 130. The
controller 130 is functionally classified into a
rewriting decision portion 131, a driving control portion
132, a recording portion 133, and an acquisition portion
134 shown in Fig. 7. Furthermore, the driving control
portion 132 has a function equivalent to an operation
decision portion 135.
[0042]
The rewriting decision portion 131 decides whether
or not the rewriting operation is performed. The
rewriting decision portion 131 executes the decision for
each pixel. The controller 130 allows the rewriting
operation to be independently performed for each pixel by
deciding whether or not the rewriting operation is
performed for each pixel. That is, the controller 130
can perform the rewriting operation of any pixel by the
decision without relying on the rewriting operation of
another pixel. The rewriting decision portion 131 is
equivalent to an example of the decision portion
according tc the invention
i00431
The driving control portion 132 controls the
scanning line driving circuit 121 and t.he data line
driving circuit 122, and generates the scanning signal
and the data signal at a predetermined timing, thereby
controlling the starting and the finishing of the
rewriting operation. The driving control portion 132
controls the scanning line driving circuit 121 and the
data line driving circuit 122 so as to perform the
rewriting operation on the pixel decided when the
rewriting operation is performed by the rewriting
decision portion 131. The driving control portion 132
applies the driving voltage to each pixel in a
predetermined pattern by the use of the wave form table
that is specified based on the table ID recorded on the
RAM 150. The driving control portion 132 is equivalent
to an example of the control portion according to the
invention.
[GO441
The operation decision portion 135 decides whether
or not the rewriting operation is performed in advance
for the pixel decided when the rewriting operation is
performed by the rewriting decision portion 131. Herein,
the rewriting operation performed in advance is different
from the rewrj.ting opsrarion decided upon being performed
by the rewriting decision port1.011 131, and refers to a
rewriting operation in which the decision was made before
the rewriting operation. Hereinafter, such a rewriting
operation is referred to as "a previous rewriting
operation (relative to the rewriting operation decided
upon being performed by the rewriting decision portion
131". In short, the operation decision portion 135 is a
section that decides whether or not the pixel decided
when performing the rewriting operation by the rewriting
decision portion 131 is in the state while the previous
rewriting operation is executed.
[0045]
The driving control portion 132 controls each pixel
decided when performing the rewriting operation by the
rewriting decision portion 131 so as to start the
rewriting operation when the previous rewriting operation
is not performed and so as to start the next rewriting
operation after the previous rewriting operation is
finished when the previous rewriting operation is
performed. The driving control portion 132 is able to
delay the next rewriting operation that is performed by
performing such a control on the pixel in which the
previous rewriting operation is not finished.
Furthermore, the driving control portion 132 allows the
delay to be performed in the pixel unit, whereby there is
EO need to wait for ths rewriting oper2cj,g~ be
performed on any pixel deperaent on the operation sfate
of another. pixel (for example, ad-jacorlt pixels) .
[ 0 0 4 6 ]
The recording portion 133 records the data on the
RAM 150 depending on the progress of the rewriting
operation. The recording portion 133 records the
scheduled data, the table ID and the remaining number on
the RAM 150. The recording portion 133 records new
scheduled data by rewriting the scheduled data to the
data corresponding to the pixel among the image data
stored in the VRAM 151 whenever the rewriting operation
of each pixel is started. Furthermore, the recording
portion 133 records the table ID of the wave form table
that is applied to each pixel when the rewriting
operation is started. In addition, the recording portion
133 records the remaining numbers of each pixel when the
rewriting operation of each pixel is started, and reduces
the remaining number "one by one" (decrement! whenever
the driving voltage is applied.
[OD471
The acquisition portion 134 acquires the data from
the ROM 140, the RRM 150, and the VRAM 151 depending on
the progress of the rewriting nperation. The acquisition
portion 134 acquires the drsving vol t,age value of the
wave form table to be applied to the rewriting operation
from the ROM 140, and acquires the image data from the
VRAM 151. Furthermore, the acquisition portion 134
acquires the scheduled data, the table ID, and the
remaining number from the RAM 150 as necessary.
[0048]
Fig. 8 is a flow chart that shows the processing to
be executed by the controller 130 having such a
configuration. As shown in Fig. 8, the controller 130
decides whether or not the image data of the VRAM 151 is
rewritten by the CPU 110 (step Sal). For example, the
decision is realized by the direct reference of the VRAM
151 by the controller 130. The controller 130 decides
that the image data is rewritten when the image data
stored in the VRAM 151 is different from the image data
acquired previously (or when the image data is initially
acquired such as immediately after the inputting of the
power source) . In addition, the controller 130 may
acquire the image data from the VRAM 151 every time
without performing the decision of step Sal.
100491
When it is decided that the image data is rewritten,
the controller 130 acquires new image data from the VRAM
151 (step Sa2) . Moreover, the controller 130 reads the
scheduled data from the RAM 150, and decides whether or
not there is a pixel, which is not consistent with the
scheduled data, in the acquired image data (step sa3).
That is, the controller 130 decides whether or not the
gradation values of each pixel are consistent with the
image data and the scheduled data. The fact that the
gradation values of the image data are entirely
consistent with the gradation values of the scheduled
data indicates that there is no need to perform a new
rewriting operation (however, if there is a rewriting
operation during execution, the rewriting operation
itself is performed). Thus, it is considered that the
decision of step Sa3 corresponds to the decision whether
or not there is a need to perform a new rewriting
operation. For example, the decision can be realized by
a logical computation that acquires an exclusive logical
sum of the gradation values of the corresponding pixels
of the image data and the scheduled data. In addition,
the controller 130 skips (omits) the processing of the
steps Sa2 and Sa3 when it is decided that the image data
is not rewritten.
[00501
When there is a pixel in which the gradation value
of the image data is not consistent with the gradation
value of the scheduled data, the controller 130 executes
the processing for rewriting tne pixel. Meanwhile, when
the gradation values of the image data are entirely
consistent with gradation values of the scheduled data,
the controller 130 executes the processing after the step
Sal without perf orming the rewriting operation. In this
case, until the new image data is written on the VRAM
151, the controller 130 does not perform the rewriting
operation, but repeatedly executes the processing of the
steps Sal to Sa3
[00511
The processing after step Sa4 is to select the
scanning line of the driving target (that is. the
rewriting target) in a predetermined order (an ascending
order of i of Yi-) and drive the pixel of the driving
target in a predetermined order (an ascending order of j
of Xj ) . Herein, the scanning line (or the pixel) of the
driving target may be all or a part of the scanning line
(or the pixel). That is, the controller 130 is able to
partially drive only a part of pixels of the display
portion 120 but not all the pixels thereof.
[0052]
The processing of the step Sa4 is a loop processing
that sequentially selects the scanning line of the
driving target. Hereln, the controller 130 repeats the
loop processing until the scanning lines of the driving
target are entire1.y selected one by one. That is, the
finish condition of the loop processing is that the
unselected scanning line of the driving target
disappears. Furthermore, the processing of the step Sa5
is a loop processing that is executed on each pixel on
the scanning line selected in the step Sa4. That is, the
controller 130 repeats the processing after step Sa6
while sequentially changing the pixels of the processing
target. In addition, in the following, the pixel of the
processing target is referred to as "a pixel for
attention".
[ 0 0 5 3 ]
In step Sa6, the controller 130 decides whether or
not the remaining number recorded on the 150 in
regard to the pixel for attention is greater than "0".
The decision is equivalent to the decision whether or not
the rewriting operation is performed on the pixel for
attention. The remaining number is always greater than
"0" if the rewriting operation is being performed.
Meanwhile, since, if the remaining number is "0" , the
rewriting operation is finished, the state, in which the
remaining number is 'O", corresponds to the state in
which the rewriting operation started previously is
finished (or the state in which the rewriting operation
is not performed even once) . Thus, when a new rewriting
operation is started, the value of the remaining number
is "0".
[0054]
When the remaining number is "O", that is, when a
new rewriting operation can be started, the controller
130 decides whether or not the gradation values of the
pixel for attention are coincident with the image data of
the V W 151 and the scheduled data of the RAM 150 (step
Sa7) . The decision is different from the decision of the
step Sa3 in that the comparison of the image data with
the scheduled data does not use a plurality of pixels as
a unit (that is, a screen unit) but uses individual
pixels as a unit. When the gradation values are
consistent with each other, the controller 130 does not
perform the rewriting operation on the pixel for
attention. Meanwhile, when the gradation values are not
consistent with each other, the controller 130 executes
the processing (hereinafter, referred to as "a
preparation processing") for starting the rewriting
operation (step Sa8) .
[0055]
Fig. 9 is a flow chart that shows a preparaticn
processing. The preparation processing is a processing
that is executed once before starting the rewriting
operation hut is not executed while the rewriting
operation is executed (that is, when the remaining number
is not "0") . In other words, the preparation processing
is a processing to record the data required for the
execution of the rewriting operation.
LO0561
In the preparation processing, the controller 130
firstly specifies the wave form table that is used for
the pixel for attention (step Sbl). The controller 130
is able to specify the wave form table by referring to
the image data stored in the VRAM 151 and the scheduled
data stored in the RAM 150. Specifically, the wave form
table, in which the gradation value of the scheduled data
of the pixel for attention is set to an initial value and
the gradation value of the image data is set to an
objective value, is a wave form table used for the pixel
for attention. Otherwise, when the writing is not
performed on the pixel for attention even once, the
initial value of the gradation value is 100% (that is,
white)
[0 0571
When the wave form table is specified in this
manner, the controller 130 specifies the table ID of the
specified wave form table and records the table ID on the
KAM ?.5C (step Sb2). In addition, the contr~ller 130
stores the table il? corresponding to any pixel arid the
table ID ~~"esponding to another pixel in a
distinguishable manner. Next, the control.ler 130 records
the maximum value of the index of the specified wave form
table on the RAM 150, and sets the same as the remaining
number (step Sb3). In addition, the controller 130
rewrites the scheduled data of the pixel for attention by
the image data of the pixel for attention (step Sb4) .
That is, the controller 130 records (overwrites) the
scheduled data of the pixel for attention so that the
image data becomes the new scheduled data. The
processing of step Sb4 is also a processing for making
the scheduled data usable as the initial value of the
gradation value when the next rewriting operation is
performed.
[0058]
In addition, the execution order of each step of the
preparation processing can be changed. For example, the
processing of step Sb2 and the processing of step Sb3 may
reverse the order of execution. Furthermore, the
processing of step Sb4 may be executed before the
processing of step Sbl. However, the processing of steps
Sb2 and Sb3 cannot be executed before the wave form table
is specified.
[0059]
When the preparation processing is finished, the
controller 130 acquires the driving voltage value used in
the driving of the pixel for attention (step Sa9) . The
controller 130 specifies the necessary wave form table
and the index by reading the +able ID and the remaining
number recorded in the preparation processing , and
acquires the driving voltage value corresponding to the
specified index. Moreover, the controller 1 3 0 instructs
the display portion 120 to drive the pixel for attention
by the acquired driving voltage value (step S a l l ) . After
that, the controller 130 decrements the remaining number
stored in the RAM 150 (step S a 1 2 ) and finishes the
processing for the pixel for attention.
[ O O ~ O I
The first application of the driving voltage in the
rewriting operation is performed as mentioned above.
Meanwhile, the application of the driving voltage after
the second time in the same rewriting operation is
perf ormed as below. In addition, deciding the
application of the driving voltage to be after the second
time is a case where it is decided that the remaining
number is greaten than "0" in step Sa6.
[ 0 0 6 1 ]
In step Sa6, when the remaining number is decided to
be greater than " O " , the controller 1 3 0 acquires the
driving voltage value used fcr the driving of +:he pixel
for attention by the same trick as the ca.se of step Sa3
(step SalO). For example, when the second driving
voltage value is acquired in any rswriting operation, the
controller 130 can acquire the corresponding driving
voltage value by reading the table ID recorded for the
preparation processing and the remaining number
decremented from the initial remaining number by one
time. After that, the controller 130 instructs the
display portion 120 to drive the pixel for attention by
the acquired driving voltage value (step Sall) ,
decrements the remaining number stored in the RAM 150
again (step Sa12), and finishes the processing.
[0062]
In addition, when the driving voltage is repeatedly
applied to the pixel for attention (that is, the
remaining number is decremented) and the number of
applications reaches a scheduled number (that is, when
the remaining number is "On), in the decision of step Sa6
to be performed after that, "YES" is decided. Thus, the
controller 130 decides the difference between the image
data and the scheduled data of the pixel for attention
again (step Sa7). At this time, if the image data of the
VRAM 151 is not rewritten from when the rewriting
operation is started, the decisinn of step Sa7 is "NO".
The reason is that the scheduled data is rewritten to the
lmage data in step Sb4 in the preparation processing.
Meanwhile, when the image data of the VRAM 151 is
rewritten from when the rewriting operation is started,
the decision of step Sa7 is "YES". In this case, the
controller 130 is able to execute the preparation
processing again and start a new writing operation.
lo0631
As mentioned above, according to the display device
100 of the present embodiment, it is decided whether or
not the rewriting operation is performed for each pixel,
and the starting and the finishing of the rewriting
operation can be controlled in the pixel unit. Thus, it
is possible to start the rewriting operation without
being affected by the operation state of another pixel.
Accordingly, the display device 100 is able to increase a
region where the rewriting operation can be started
without relying on the rewriting operation being executed
(that is, the previous rewriting operation) , as compared
to a case where the rewriting is performed for each
partial region (constituted by a plurality of pixels).
[0064]
Furthermore. according to the display device 100.
even when the image data of the VRAM 151 is rewritten
during the rewriting operation, the rewriting of the
image data does not affect the rewriting operation until
the remaini~g number is "0" . That is, the controller 130
is operated regardless of the rewriting of the image data
of the VRAM 151 until the rewriting operation of the
pixel for attention is finished, and decides whether or
not the next rewriting operation is performed after the
rewriting operation is finished. By doing this, when the
rewriting of the image data is performed several times
during the rewriting operation, it is possible that the
rewriting of the pixels for attention at the mid-point
(other than the final one) may not be reflected on the
actual display, and it is expected that the pixels for
attention will more quickly enter a desired display
state. The effect is more remarkable as the number of
applications per rewriting operation is increased.
Similarly, for example, when an objective value of the
pixel for attention due to any rewriting operation is
consistent with an objective value of the pixel after
several rewriting of the image data, it is also possible
to omit a rewriting operation after the rewriting
operation so as not to be performed.
[0065]
In addition, the display device 100 has a
characteristic that does not need to perform the
management or the like of the rewriting operation for
each pixel when viewed from the side operating the CPU
110 and may simply write the image data to be displayed
on the VRAM 151. By such a characteristic, a developer
of an application to be operated by the CPU 110 is able
to produce an application that does not need to consider
the display state or the rewriting operation state of
each pixel.
100661
[Modified Example]
The invention can also be implemented in various
forms described below. In addition, the modified example
or the application example described below may be
suitably combined with each other as necessary.
(Modified Example 1)
The data showing the pattern of the driving voltage
is not limited to a so-called table type. The data
showing the pattern of the driving voltage may be, for
example, described using the concept of the pointer or
the arrangement in the programming. Furthermore, the
data showing the pattern cf the drlving voltage need not
be one in which the driving voltage value and the
remaining number correspond to each other in a one-to-one'
relationship. For example, the data corresponding to the
wave form table T1 of Fig. 2 may describe the driving
voltage value and the number to be applied, for example,
after applying the driving voltage value "Vw" "once", the
driving voltage value "Vn" is a.pplied "once" .
[ 0 0 6 8 ]
(Modified Example 2)
The data for specifying the pattern of the driving
voltage need not be an ID for identifying the pattern.
For example, in the aforementioned embodiment, if the
pattern of the driving voltage is uniquely specified by
the combiriation of the initial value and the objective
value of the gradation, the controller 130 may record the
initial values of the gradations of each pixel instead of
the table ID in the preparation processing. By doing so,
it is possible to specify the required wave form table by
the recorded initial value and the scheduled data (that
is, the objective value).
[ 0 0 6 9 ]
In addition, the wave form table can also be shared
between the different initial values or objective values
of the gradation. For example, the substantial contents
of the wave form tables T2 and T6 shown in Fig. 2 are
identical to each other. When the wave form table can be
shared, it is possible to reduce the storage reglon
required for the storage of the wake form table.
[0070]
(Modified Example 3)
The pattern of the driving voltage of any rewriting
operation can be determined in view of other factors as
well as the initial value and the objective value of the
gradation of the pixel. For example, when the
responsiveness of the display element differs depending
on the temperature and the display element includes a
sensor that detects the temperature, the pattern of the
driving voltage may be determined by the initial value,
the objective value, and the temperature of the gradation
of the pixel.
Alternatively, when the pattern of the driving
voltage in a certain rewriting operation to a certain
pixel is determined, it is also possible to consider the
initial value (or the pattern of the driving voltage) of
the gradation in the previous rewriting operation
relative to the rewriting operation.
[0071]
(Modified Example 4)
In the invention, the number of applications in one
rewriting operation may be variable depending on the
icitial value or the objective value of the gradation (or
both of them), but may be constant regardless of the
gradation. When the number of applications in the one
rewriting operation is constant, the controller 130 may
perform a fixed number of voltage applications on the
pixel of the rewriting target without performing the
recording of the remaining number (step Sb3) or the like.
(Modified Example 5)
The number of gradations realizable in the invention
is not particularly limited. For example, if the number
of applications in the one rewriting operation is
increased, it is possible to realize the number of
gradations greater than that of the aforementioned
embodiment (four gradations). Furthermore, the invention
can also be applied to the display of two gradations that
do not include a halftone.
[00731
(Modified Example 6)
In the aforementioned embodiments, the data
corresponding to the remaining number may be data that
can specify the number of applications of the driving
voltage to the one rewriting operation For example, the
controller 130 may record the occasional number of
applications on the RAM 150 instead of the remaining
number. In this case, the controller 130 is able to
obtain the remaining number by performing the computation
of reducing the number of applications recorded on the
RAM 150 from the total number of the number of
applications required for the one rewriting operation.
At this time, the controller 130 may perform the
increment (an addition of the number of applications)
instead of the decrement in step Sa12.
[00741
(Modified Example 7)
The configuration of the display panel 123 is not
limited to that shown in Fig. 6. For example, the
electrophoresis layer is not limited to the configuration
including a plurality of micro capsules, but may be a
configuration in which the dispersion medium and the
electrophoresis particle are included in the space
divided by a partition. Furthermore, in the
aforementioned embodiments, a case is assumed where the
black and white display is implemented using the black
and white two types of electrophoresis particles, one of
them having the positive electric charge and the other
having the negative electric charge, as the
electrophoresis element. However, the invention can be
applied to a display using a concentration change of two
directions such as red and white or blue and black by
means of a difference in concentration.
Furthermore, the display element according to the
invention is not limited to the electrophoresis element.
As the display element according to the invention, a
display element may be used which uses, for example, a
cholesteric liquid crystal, an electrochromic substance,
an electronic powder fluid or the like.
[0075]
(Modified ~xample 8)
The aforementioned embodiment is an example in which
the display by the display device 100 is realized by the
cooperation of the CPU 110 and the controller 130.
However, the invention may also be realized by a single
component (for example, a CPU simple substance) without
relying on the cooperation. In this case, the invention
can also be provided as a program for realizing the
control device according to the invention in a computer
such as a CPU, or a recording medium that records such a
program.
[0076]
[Application ~xamplel
The invention can be applied to various types of
electrorlic equipment including the display device. The
invention is especially suitable for the utilization in
the electronic equipment ( for example, portable
electronic equipment, small electronic equipment or the
like) that requires a low consumption electric power if
the display element having the memory property is used.
Furthermore, the invention is especially suitable even
for the application that frequently uses the partial
rewriting of the screen.
[00771
Fig. 10 show diagrams that show electronic equipment
to which the display device according to the invention is
applied. Fig. 10(a) is a diagram that shows an exterior
of a reader for reading a document such as a so-called
electronic book. In Fig. 10 (a) , a reader 1100 includes a
case 1101, an operation portion 1102 that receives the
operation of a user, and a display portion 1103 to which
the invention is applied. In addition, it is also
possible to make the reader 1100 a so-called flexible
display by being formed of a material that can bend or
curve the case 1101 and the display portion 1103.
[00781
Furthermore, the reader 1100 is able to receive the
operation of a user in the display portion 1103 by
providing a touch screen in the display portion 1103. In
the case of such a configuration, the reader 1100 is also
able to display handwriting letters or lines by driving
the pixel corresponding to the region receiving the
operation by the touch screen to change the gradation.
[0079]
Fig. 10 (b) is a diagram that shows an exterior of a
mobile phone. In Fig. 10(b), a mobile phone 1200
includes a case 1201, an operation portion 1202 such as a
key pad, and a display portion 1203 to which the
invention is applied. In addition, when the mobile phone
1200 has a plurality of display regions, the display
device according to the invention may be applied to one
(for example, a sub display) , and another display device
may be applied to the other (for example, a main
display) .
[0080]
In addition, the present invention can also be
applied to a personal computer, a PDA (Personal Digital
Assistant), a radio communication terminal such as a
smart phone, an electronic dictionary, a digital type
clock or the like
Reference Sign List
[0081]
100 . . . display device, 110 . . . CPU. 120 . . . display
portion. 130 . . . controller. 131 . . . rewriting decision
portion. 132 . . . driving control portion. 133 . . .
recording portion, 134 . . . acquisition portion. 135 . . .
operation decision portion, 140 . . . ROM, 150 . . . RAM. 151
. . . VRAM, TI TO T12 . . . wave form table. 30 . . . pixel,
1100 . . . reader, 1200 . . . mobile phone

CLAIMS
[Claim 1]
A control device that controls the driving of a
display device which changes display states of a
plurality of pixels from a first display state to a
second display state by a rewriting operation of applying
a driving voltage several times, the control device
comprising:
a decision portion that decides whether or not the
rewriting operation is performed for each pixel; and
a control portion that applies the driving voltage
several times in a pattern, in which the driving voltages
of each time are determined depending on the first
display state and the second display state, to the pixel
decided when performing the rewriting operation by the
decision portion and starts the rewriting operation,
wherein, in a case where a previous rewriting
operation is not performed on the pixel decided when
performing the rewriting operation by the decision
portion, the control portion starts the rewriting
operation, and in a case where the previous rewriting
operation is performed on the pixel, the control portion
starts the next rewriting operation after the previous
rewriting operation is finished.
50
< » »
[Claim 2]
The control device according to Claim 1,
wherein the number of applications of the driving
voltage in one rewriting operation differs depending on
at least one of the first display state and the second
display state.
[Claim 3]
The control device according to Claim 1 or 2,
further comprising:
a first recording portion that records data for
specifying the number of applications of the driving
voltage in the one rewriting operation for each pixel,
wherein the control portion decides whether or not
the previous rewriting operation is performed, depending
on whether or not the number specified by the data
recorded by the first recording portion reaches a
scheduled number.
[Claim 4]
The control device according to any of Claims 1 to
3,
wherein, when the previous rewriting operation is
performed on the pixel for which it is decided that the
51
rewriting operation is to be performed, the decision
portion performs the decision again after the previous
rewriting operation is finished, and
when it is decided that the rewriting operation is
not performed by the repeated decision by the decision
portion, the control portion does not perform the
rewriting operation.
[Claim 5]
The control device according to any of Claims 1 to
4, further comprising:
an acquisition portion that reads and acquires an
image data from a first storage region which stores the
image data showing display states to be displayed on each
pixel by the plurality of pixels; and
a second recording portion that records a scheduled
data, which shows a scheduled display state to be
displayed on each pixel when the rewriting operation is
finished, by each pixel, wherein the decision portion
decides the pixel, in which the display state shown by
the image data acquired by the acquisition portion is not
consistent with the display state shown by the scheduled
data, as a pixel in which the rewriting operation is
performed.
52
* •
[Claim 6]
The control device according to Claim 5,
wherein the second recording portion rewrites the
scheduled data for the pixel in which the rewriting
operation is started by the control portion so that the
image data becomes new scheduled data.
[Claim 7]
A display device comprising:
the control device according to any of Claims 1 to
6 ; and
a display portion that has a plurality of pixels and
performs the rewriting operation depending on the control
by the control device.
[Claim '8]
The display device according to Claim 7,
wherein the pixels include a display element having
a memory property.
[Claim 9]
A control method by a section that controls the
driving of a display device which changes display states
of a p l u r a l i t y of pixels from a f i r s t display state to a
second display s t a t e by a rewriting operation of applying
53
i • >
a driving voltage several times, the method comprising:
a decision step of deciding whether or not the
rewriting operation is performed for each pixel; and
a controlling step of applying the driving voltage
is applied several times in a pattern, in which the
driving voltages of each time are determined depending on
the first display state and the second display state, to
the pixel decided when performing the rewriting operation
in the decision and starting the rewriting operation,
wherein, in the controlling step, in a case where a
previous rewriting operation is not performed on the
pixel decided when performing the rewriting operation in
the decision, the rewriting operation is started, and in
a case where the previous rewiring operation is performed
on the pixel, the next rewriting operation is started
after the previous rewriting operation is finished.