1. A liquid crystal display device comprising a black mask formed on one of a pair of substrates at least one of which is transparent, a group of electrodes formed on at least one of said pair of substrates, a liquid crystal layer comprising a liquid crystal composition substance having a dielectric anisotropy and held between said pair of substrates, an orientation control film formed between said liquid crrystal layer and one of said substrates for orienting liquid crystal molecules of said liquid crystal composition substance in a predetermined direction, a polarizing means laminated on at least one of said pair of substrates, and a drive means for applying a drive voltage to said group of electrodes, wherein said group of electrodes has a structure that the electrodes are so arranged as to generate an electric field having a component predominantly in parallel with the interface between said orientation control film and said liquid crystal layer, said liquid crystal composition substance has a resistivity of not smaller than 10N Ω.cm, and said black mask has a resistivity of not smaller than 10M Ω.cm, wherein N and M are integers satisfying the relationships N > 9 and M > 6.

2. A liquid crystal display device comprising a black mask formed on one of a pair of substrates at least one of which is transparent, a group of electrodes formed on at least one of said pair of substrates, a liquid crystal layer comprising a liquid crystal composition substance having a dielectric anisotropy and held between said pair of substrates, an orientation control film formed between said liquid crrystal layer and one of said substrates for orienting liquid crystal molecules of said liquid crystal composition substance in a predetermined direction, a polarizing means laminated on at least one of said pair of substrates, and a drive means for applying a drive voltage to said group of electrodes, wherein said group of electrodes has a structure that the electrodes are so arranged as to generate an electric field having a component predominantly in parallel with the interface between said orientation control film and said liquid crystal layer, said liquid crystal composition substance has a resistivity of not smaller than 10N Ω.cm, and said black mask has a resistivity of not smaller than 10M Ω.cm, wherein N and M are integers satisfying the relationships N > 13 and M > 7.

3. A liquid crystal display device according to claim 1 or 2, wherein metal oxide particles are contained in said black mask.

4. A liquid crystal display device according to claim 3, wherein said metal oxide particles are parrticles of at least one of cobalt oxide, chromium oxide, manganese oxide and nickel oxide.

5. A liquid crystal display device according to claim 3, wherein either or both of an organic pigment and a graphite powder in addition to said metal oxide particles are contained in said black mask.

6. A liquid crystal display device according to claim 4, wherein said cobalt oxide particles are chiefly tricobalt tetroxide particles. 7 . A liquid crystal display device according to claim 4, wherein any one of chromium oxide, manganese oxide and nickel oxide is contained in addition to said cobalt oxide.

8. A liquid crystal display device according to claim 1 or 2, wherein the base material of said black mask is made of a polyimide resin.

9. A liquid crystal display device according to claim 8, wherein the composition of said polyimide resin material contains a component that is cured by light and a component that is cured by heat, and the optical density of said black mask increases as said resin material is cured by heat.

10. A liquid crystal display device according to claim 8 or 9, wherein said black mask is composed of a polyimide resin material which contains at least one or more kinds of black coloring agents and other coloring agents different from said black coloring agents.

11. A liquid crystal display device according to claim 8 or 9, wherein said black mask is composed of a polyimide resin material in which are mixed metal oxide particles as a black coloring agent. The light-shielding ability of the black mask is practically satisfactory, and the disturbance of the electric field pattern is eliminated, achieving display of high quality picture without color nonuniformity. A liquid crystal display device comprising a black mask formed on one of a pair of substrates at least one of which is transparent, a group of electrodes formed on at least one of the pair of substrates, a liquid crystal layer comprising a liquid crystal composition substance having a dielectric anisotropy and held between the pair of substrates, an orientation control film formed between the liquid crrystal layer and one of the substrates for orienting liquid crystal molecules of the liquid crystal composition substance in a predetermined direction, a polarizing means laminated on at least one of the pair of substrates, and a drive means for applying a drive voltage to the group of electrodes, wherein the group of electrodes has a structure that the electrodes are so arranged as to generate an electric field having a component predominantly in parallel with the interface between the orientation control film and the liquid crystal layer, the liquid crystal composition substance has a resistivity of not smaller than 10N Ω.cm, and the black mask has a resistivity of not smaller than 10M Ω.cm, wherein N and M are integers satisfying the relationships N > 9 and M > 6.

Title of the Invention:
Liquid crystal display device with wide viewing
angle characteristics comprising high resistivity
black matrix
Background of the Invention: '
Field of the Invention;
The present invention relates to a liquid crystal
display device and, particularly, to an active matrix
liquid crystal display device of a high picture quality
with wide viewing angle characteristics comprising high
resistivity black matrix and with excellent
light-shielding ability.
Description of the Prior Art;
Display devices using a liquid crystal display
device having reduced thickness and reduced weight and
consuming decreased amounts of electric power have in
recent years been widely used for personal computers,
word processors and other information equipment.
Basically, the liquid crystal display device has
a matrix made up of a number of electrodes arranged
horizontally and vertically and a liquid crystal layer
interposed between the horizontal electrodes and the
vertical electrodes, and pixels are formed at the
portions where two electrodes intersect each other to

display a two-dimensional picture.
The liquid crystal display devices of this kind
can be divided into those of a so-called passive matrix
system which selects a predetermined pixel at a timing
of a pulse applied to horizontal and vertical
electrodes, and those of a so-called active matrix
system in which a nonlinear element such as transistor
or the like is provided in each pixel and a
predetermined nonlinear element is selected.
In a liquid crystal display device of the active
matrix system, non-linear elements (switching elements)
are provided at positions corresponding to a plurality
of pixel electrodes arranged in the form of a matrix.
Theoretically, the liquid crystal in each pixel is
driven at all times (duty ratio of 1.0). Compared with
the so-called passive matrix system employing a
time-division multiplex driving system, therefore, the
active matrix system exhibits a good contrast and has
been establishing a technique that is indispensable
particularly in the color liquid crystal display
devices. Thin-film transistors (TFTs) are
representative examples of the switching elements.
In a conventional thin-film transistor liquid
crystal display element, transparent electrodes are so
formed as to face each other on the interface of two

substrates to drive the liquid crystal layer.
That is, there has been employed a display system
as represented by a so-called twisted nematic display
system in which the direction of the electric field
applied to the liquid crystals is almost perpendicular
to the interface of the substrates owing to the
employment of the above-mentioned electrode structure.
As a system in which the direction of an electric
field applied to the liquid crystals is almost in
parallel with the interface of the substrates,
furthermore, there has been proposed a system
(so-called an inplane electric field system) employing
a pair of comb-toothed electrodes formed on the surface
of at least one of the substrates for driving the
liquid crystal layer as disclosed in, for example,
Japanese Patent Publication No. 21907/1988 and Japanese
Patent Laid-Open No. 36058/1995. The method of setting
comb-toothed electrodes and the method of its
fabrication have been proposed already by the present
applicant in Japanese Patent Application No.
105862/1995.
In such an electrode structure, the major axes of
molecules of the liquid crystal layer (hereinafter also
referred to simply as liquid crystal molecules) are
substantially in parallel with the surfaces of the

substrates, and the liquid crystal molecules are
suppressed from being erected in a direction
perpendicular to the substrates. Therefore, the
brightness changes little even when the viewing angle
is changed; i.e., the so-called viewing angle
dependence does not almost exist, and wide viewing
angle characteristics are accomplished compared with
those of the vertical electric field system.
In a conventional black mask interposed among the
colored layers of various colors and constituting the
substrate (color-filter substrate) of a color filter,
furthermore, a pattern of thin film of metal chromium
or low-reflection metal chromium has been formed. Or,
a pattern of a thin layer of a photosensitive resin has
been formed, dispersing a black coloring agent, or
black carbon powder (chiefly graphite) therein, and
adding various pigments thereto.
The colored layers of the color-filter substrate
usually have a structure in which a protective layer
PSV2 is formed on the colored layers FIL(R), FIL(G),
FIL(B) of which the pattern regions are separated like
a mosaic or vertical stripes for each of the pixels or
colors.
When the colored layers are fabricated by using
pigment-dispersed resin materials in the color filter

used for the active matrix-type liquid crystal display
devices, furthermore, the protective layer PSV2 is not
often employed.
Fig. 13 is a schematic sectional view
illustrating the constitution of a pixel that
constitutes an inplane electric field-type liquid
crystal display device and illustrating the turn-on
operation, wherein reference numeral 1 denotes a TFT
substrate, 1' denotes a color-filter substrate, 2
denotes a common electrode, 6 denotes an insulating
film, 11 denotes pixel electrodes, 12 denotes a
protective film, 17 denotes a black mask, and 18
denotes a color filter.
In Fig. 13, a liquid crystal layer is held
between the TFT substrate 1 and the color filter
substrate 1'. On the surfaces of the protective film
12 and of the color filter 18 are formed orientation
films for establishing the initial orientation of
liquid crystal molecules of the liquid crystal layer.
Moreover, though not shown in FIG. 13, polarizer plates
are installed on the outer surface sides of the TFT
substrate 1 and the color filter substrate 1'.
In the above mentioned inplane electric field
liquid crystal display device, the pixel electrodes 11
and the common electrode 2 are formed on one substrate

(TFT substrate 1), and on the other substrate
(color-filter substrate 1') is formed a color filter 18
that constitutes a color of a pixel demarcated by the
black mask 17.
The black mask 17 demarcating the color filter
prevents the reflection of external light and enhances
the contrast by absorbing light from the neighboring
pixels.
Summary of the Invention:
In a conventional vertical electric field liquid
crystal display device having a common electrode formed
on the side of the color-filter substrate, the black
mask constituting the color-filter substrate is
required to have a high light absorption factor and a
low light reflection factor. However, no consideration
concerning the resistivity of the black mask has been
taken.
That is, in the above-mentioned black mask using
a resin material, a large amount of graphite is added
particularly to improve the absorption factor.
Therefore, the resistivity decreases with an increase
in the amount of graphite added. When metal chromium
is used for the black mask, furthermore, the light-
shielding ability is improved greatly and the

resistivity becomes very small.
In the inplane electric field-type liquid crystal
display device in which the black mask has a small
resistivity, however, the lines of electric force from
the pixel electrodes 11 are attracted by the black mask
17 having a small resistivity, as shown in Fig. 13,
when a voltage is applied between the pixel electrodes
11 and the common electrode 2 to turn the pixel on, and
the pattern of electric field is disturbed and tilted
with respect to the interface of the substrates. As a
result, the horizontal component of the lines of
electric force is weakened, and a desired light
transmission factor is not obtained. Alternatively,
so-called domains occur at positions of the pixel
electrodes 11 and the common electrode 2. Accordingly,
the contrast is degraded, color display becomes
nonuniform, and a good picture quality is not obtained.
Figs. 14A and 14B are schematic diagrams
illustrating a pixel in an inplane electric field
liquid crystal display device having two comb-toothed
common electrodes arranged in a pixel. Fig. 14A is a
plan view and Fig. 14B is a sectional view cut along
the line A-A' in Fig. 14A. A color filter is formed on
a portion surrounded by the black mask 17, and various
films are formed thereon and on the common electrodes 2

and on the pixel electrodes 11, which, however, are not
shown here.
In Figs. 14A and 14B, a pixel is formed in an
open region surrounded by the black mask, a pixel
electrode 11 and a common electrode 2 are arranged in
this region, and a liquid crystal layer is held between
the TFT substrate 1 and the color filter substrate 1'.
The black mask has a resistivity of not larger than 104
Ω.cm.
By a signal voltage applied for turn on, an
electric field is generated between the common
electrode 2 and the neighboring pixel electrode 11.
This electric field acts strongly upon the liquid
crystal molecules depending upon the magnitude of the
applied signal voltage, whereby the orientation of
liquid crystal molecules rotates and light passes from
the TFT substrate 1 to the color-filter substrate 1' at
an increased transmission factor.
Fig. 15 is a diagram illustrating the
transmission factor that varies depending upon the
position in the gap between the common electrode 2 and
the pixel electrode 11 shown in Fig. 14A, wherein a
spot a denotes a position away from the black mask 17
and a spot b denotes a position close to the black mask
17.

As shown, the transmission factor increases with
an increase in the signal voltage applied between the
common electrode 2 and the pixel electrode 11. As
shown in Fig. 14A, however, since the spot b is located
close to the black mask 17, the electric field pattern
is formed at a sharp angle with respect to the surface
of the substrate. Accordingly, in a change in the
transmission factor with an increase in the voltage,
the rise is behind that of the spot a. In Fig. 15, the
voltage of the spot b must be increased by about one
volt with respect to the spot a to obtain the same
transmission factor.
When the same voltage is applied, therefore, the
transmission factor differs between the central portion
and the peripheral portion in a pixel, and the color
becomes nonuniform.
The object of the present invention is to provide
a liquid crystal display device of a so-called inplane
electric field device having an improved light-
shielding ability, suppressing disturbance of the
pattern of electric field, and displaying a picture of
high quality without nonuniformity in color.
In order to accomplish the above-mentioned
object, means 1 is characterized in that, a liquid
crystal display device comprises a black mask formed on

one of a pair of substrates at least one of which is
transparent, a group of electrodes formed on at least
one of the pair of substrates, a liquid crystal layer
comprising a liquid crystal composition substance
having a dielectric anisotropy and held between the
pair of substrates, an orientation control film formed
between the liquid crystal layer and one of the
substrates for orienting the liquid crystal molecules
of the liquid crystal composition substance in a
predetermined direction, a polarizing means laminated
on at least one of the pair of substrates, and a drive
means for applying a drive voltage to the group of
electrodes, wherein the group of electrodes has a
structure that the electrodes are so arranged as to
generate an electric field having a component
predominantly in parallel with the interface between
the orientation control film and the liquid crystal
layer, said liquid crystal composition substance has a
resistivity of not smaller than 10N Ω.cm, and said
black mask has a resistivity of not smaller than 10M
Ω.cm, wherein N and M are integers satisfying the
relationships N > 9 and M > 6.
Means 2 is characterized in that a liquid crystal
display device comprises a black mask formed on one of
a pair of substrates at least one of which is

transparent, a group of electrodes formed on at least
one of the pair of substrates, a liquid crystal layer
comprising a liquid crystal composition substance
having a dielectric anisotropy and held between the
pair of substrates, an orientation control film formed
between the liquid crystal layer and one of the
substrates for orienting the liquid crystal molecules
of the liquid crystal composition substance in a
predetermined direction, a polarizing means laminated
on at least one of the pair of substrates, and a drive
means for applying a drive voltage to the group of
electrodes, wherein the group of electrodes has a
structure that the electrodes are so arranged as to
generate an electric field having a component
predominantly in parallel with the interface between
the orientation control film and the liquid crystal
layer, said liquid crystal composition substance has a
resistivity of not smaller than 10N Ω.cm, and said
black mask has a resistivity of not smaller than 10M
Ω.cm, wherein N and M are integers satisfying the
relationships N > 13 and M > 7.
Means 3, according to means 1 or 2, is
characterized in that metal oxide particles are
contained in the black mask.
Means 4, according to means 3, is characterized

in that metal oxide particles are particles of at least
one of cobalt oxide, chromium oxide, manganese oxide
and nickel oxid.
Means 5, according to means 3, is characterized
in that either or both of an organic pigment and a
graphite powder are contained in the black mask in
addition to the meatl oxide particles.
Means 6, according to means 4, is characterized
in that the cobalt oxide particles are chiefly
tricobalt tetroxide particles.
Means 7, according to means 4, is characterized
in that any one of chromium oxide, manganese oxide and
nickel oxide is contained in addition to the cobalt
oxide.
Means 8, according to means 1 or 2, is
characterized in that the black mask contains the
polyimide resin as a base material.
Means 9, according to means 8, is characterized
in that the base material of the black mask is a resin
material having a polyimide group, the composition of
the resin material contains a component that is cured
by light and a component that is cured by heat, and the
optical density increases as the resin material is
cured by heat.
Means 10, according to means 8 or 9, is

characterized in that the black mask is composed of a
polyimide resin material which contains at least one or
more kinds of black coloring agents and other coloring
agents different from the black coloring agents.
Furthermore, means 11, according to means 8 or 9,
is characterized in that the black mask is composed of
a polyimide resin material in which metal oxide
particles are mixed as a black coloring agent.
In the constitution of the above-mentioned means
1, the black matrix formed on one of the pair of
substrates shuts off the entry of light from the
neighboring pixels that are turned on, contributing to
increasing the contrast of a display image.
The group of electrodes formed on one or both of
the pair of substrates comprise a common electrode and
a pixel electrode, and forms an electric field pattern
between the two electrodes when the pixel is turned on
to rotate the orientation of liquid crystal molecules
of a liquid crystal composition substance that
constitutes the liquid crystal layer, so that the light
transmission factor changes. The orientation control
film (orientation film) works to orient the liquid
crystal molecule of the liquid crystal composition
substance in a predetermined direction when no electric
field is applied.

The polarizing means is laminated on at least one
of the pair of substrates, and permits the passage of
light that is polarized in a specific direction before
entering into the liquid crystal layer or after having
passed through the liquid crystal layer.
The drive means applies a drive voltage to the
group of electrodes to turn a predetermined pixel on to
display an image.
The group of electrodes has a structure that the
electrodes are so arranged as to generate an electric
field having a componet predominantly in parallel with
the interface between the orientation control layer and
the liquid crystal layer. When the electric field is
generated between the common electrode and the pixel
electrode constituting the group of electrodes, the
liquid crystal molecules are rotated in a plane
substantially in parallel with the interface.
The liquid crystal composition substance has a
resistivity of not smaller than 10N Ω.cm and the black
mask has a resistivity of not smaller than 10M Ω.cm
(where N and M are integers) satisfying the
relationships N > 9 and M > 6, thereby to effectively
generate an electric field component in parallel with
the substrates.
Accordingly, the liquid crystal molecules rotate

in a plane substantially in parallel with the
interface, making it possible to suppress the
occurrence of so-called domains and the rise of the
drive voltage.
In the constitution of means 2, furthermore, the
liquid crystal composition substance has a resistivity
of not smaller than 10N Ω.cm and the black mask has a
resistivity of not smaller than 10M Ω.cm (where N and M
are integers) satisfying relationships N > 13 and M >
7, thereby to more effectively generate an electric
field component in parallel with the substrates than
that of means 1.
Accordingly, the liquid crystal molecules rotate
in a plane substantially in parallel with the
interface, making it possible to further suppress the
occurrence of so-called domains and the rise of the
drive voltage.
In the constitution of means 3, furthermore,
metal oxide particles are contained in the black mask
formed on one of the pair of substrates at least one of
which is transparent. Therefore, the black mask
exhibits an increased resistivity yet maintaining an
optical density, and the electric field component is
more effectively generated between the electrodes in a
plane nearly in parallel with the above-mentioned

interface.
Accordingly, the liquid crystal molecules rotate
in a plane nearly in parallel with the interface,
making it possible to suppress the occurrence of
so-called domains and the rise in the drive voltage,
and enabling the light transmission factor to be
improved.
In the constitution of means 4, furthermore, the
black mask contains cobalt oxide particles, chromium
oxide particles, manganese oxide particles or nickel
oxide particles so as to possess an increased optical
density and an increased resistivity. Therefore, the
electric field component is generated more effectively
between the electrodes in a plane in parallel with the
above-mentioned interface.
Accordingly, the liquid crystal molecules rotate
in a plane nearly in parallel with the interface,
making it possible to suppress the occurrence of
so-called domains and the rise of the drive voltage,
and enabling the light transmission factor to be
improved.
In the constitution of means 5, the black mask
contains either or both of an organic pigment and a
graphite powder in addition to the metal oxide
particles so as to possess an increased resistivity and

to absorb light more efficiently. Accordingly, the
liquid crystal molecules rotate in a plane nearly in
parallel with the interface, making it possible to
suppress the occurrence of so-called domains and the
rise of the drive voltage, and enabling the light
transmission factor to be improved.
In the constitution of means 6, tricobalt
tetroxide is chiefly used as the cobalt oxide particles
so that the black mask maintains the resistivity and
the absorbancy.
In the constitution of means 7, any one of
chromium oxide, manganese oxide or nickel oxide is
contained in addition to the cobalt oxide, so that the
black mask maintains the resistivity and the light
absorption factor.
In means 8 to 10, use is made of a polyimide
photosensitive resin, and a feature that the optical
density increases in the step of curing the resin by
light and heat is utilized in order to obtain a black
mask of nearly a black color having a high insulating
property.
That is, in the constitution of means 8, the
black mask is comprised of a material which contains a
polyimide resin as the base material and has a high
resistivity. Therefore, the insulating property is

prevented from decreasing, and the electric field
component for rotating the liquid crystal molecules is
effectively generated in parallel with the interface.
In the constitution of means 9, the black mask is
made of a resin material having a polyimide group and
containing a component that is cured by light and a
component that is cured by heat. Therefore, there is
formed a black mask that is colored in black upon the
curing by heat, and exhibits a great light-shielding
ability.
In the constitution of means 10, the black mask
is made of the polyimide resin material that contains
at least one or more kinds of black coloring agents and
other coloring agents than the above-mentioned black
coloring agents. Therefore, the black mask exhibits a
great light-shielding ability.
In the constitution of means 11, the black mask
is made of the polyimide resin material in which is
mixed metal oxide particles as a black coloring agent.
Therefore, the black mask exhibits a high resistivity
and a great light-shielding ability.
The above-mentioned polyimide-type photosensitive
resin has in the molecule skeleton thereof a functional
group that absorbs visible rays but does not contain
carbon or graphite which has been conventionally

contained. It is therefore possible to set a low
transmission factor without lowering the resistivity.
The foregoing and other objects, advantages,
manner of operation and novel features of the present
invention will be understood from the following
detailed description when read in connection with the
accompanying drawings.
Brief Description of the Drawings:
Figs. 1A to 1D are schematic diagrams of a pixel
for explaining the operation of an inplane electric
field-type liquid crystal display device;
Figs. 2A to 2C are diagrams illustrating a
structure of a TFT substrate constituting an embodiment
of an inplane electric field liquid crystal display
device;
Fig. 3 is a diagram illustrating example 1 or 2
of the structure of a color-filter substrate in the
inplane electric field liquid crystal display device;
Fig. 4 is a schematic diagram of an electric
field pattern in a pixel in cross section constituting
the embodiment 1 or 2 of the inplane electric field
liquid crystal display device;
Fig. 5 is a diagram illustrating a rise of the
drive voltage relative to the resistivity of the black

mask of when the resistivity of the liquid crystal
layer of the inplane electric field liquid crystal
display device is changed;
Fig. 6 is a diagram illustrating a change in the
resistivity of the black mask relative to the ,content
of carbon therein and a change in the optical density
of when the film thickness is 1 μm, in the embodiment 1
of the present invention;
Fig. 7 is a sectional view illustrating an
essential portion of the color-filter substrate used in
the embodiment 3 of the inplane electric field color
liquid crystal display device;
Fig. 8 is a diagram schematically illustrating
the steps of forming the black mask shown in Fig. 7;
Fig. 9 is a diagram illustrating the steps of
fabricating the color-filter substrate shown in Fig. 7;
Fig. 10 is a diagram showing the connection of an
equivalent circuit of a display matrix unit and the
peripheral circuits in a liquid crystal display device;
Fig. 11 is an exploded perspective view
illustrating an example of the constitution of the
liquid crystal display device according to the present
invention;
Fig. 12 is a diagram showing the appearance of a
personal computer for explaining an information

processing device in which a liquid crystal display-
device of the present invention is mounted;
Fig. 13 is a sectional view for schematically
illustrating the constitution of a pixel constituting
an inplane electric field liquid crystal display device
and for illustrating the turn-on operation;
Figs. 14A and 14B are schematic diagrams of a
pixel in an inplane electric field liquid crystal
display device in which two comb-toothed common
electrodes are arranged in a pixel; and
Fig. 15 is a diagram illustrating a change in the
transmission factor depending upon the position in the
gap between the pixel electrode and the common
electrode shown in Figs. 14A and 14B.
Description of the Preferred Embodiments:
Embodiments of the present invention will now be
described in detail with reference to the drawings.
Figs. 1A to 1D are schematic diagrams of a pixel
for explaining the operation of a liquid crystal
display device to which the present invention is
applied. Fig. 1A is a sectional view of when no
voltage is applied, Fig. 1B is a sectional view of when
a voltage is applied, Fig. 1C is a plan view of when no
voltage is applied, and Fig. 1D is a plan view of when

a voltage is applied. The voltage referred to here is
a selection voltage applied between the common
electrode and the pixel electrode.
In Figs. 1A and 1B, reference numerals 1 and 1'
denote transparent glass substrates (hereinafter also
referred to simply as substrates), 2 denotes a common
electrode, 6 denotes an insulating film, 10 denotes a
signal wiring, 11 denotes a pixel electrode, 12 denotes
a protective film, 13 and 13' denote polarizer plates,
14 and 14' denote axes of polarization of the polarizer
plates, 15 denotes the orientation of liquid crystal
molecules, 16 denotes the direction of an electric
field, 17 denotes a black mask (BM), 18 denotes a color
filter, 19 denotes a protective film (flattening film),
20 and 20' denote orientation films, and reference
numeral 21 denotes liquid crystal molecules (chiefly
rod-like liquid crystal molecules).
The liquid crystal display device comprises the
polarizer plate 13', black mask 17 for shielding light,
color filter 18, protective film 19 and orientation
film 20' that are formed on one substrate (color-filter
substrate 1') of two transparent glass substrates 1 and
1'. On the other substrate (TFT substrate) 1 via the
liquid crystal 21 are formed the polarizer plate 13,
orientation film 20, signal electrode 10, pixel

electrode 11, common electrode 2, wirings and thin-film
transistor (TFT). Figs. 1A and 1B do not illustrate
wirings or thin-film transistors.
Referring to Figs. 1A and 1C, the liquid crystal
molecules 21 are oriented homogeniously by the
orientation films 20, 20' in the direction 15 of
orientation which is nearly in parallel with the planes
of the substrates 1, 1'. In this state, the direction
of initial orientation of liquid crystal molecules 21
is nearly in agreement with the axis 14 of polarization
of the polarizer plate 13, and the axis 14' of
polarization of the upper polarizer plate 13' is
perpendicular thereto and the pixel is in a non-display
(turned-off) state.
Referring next to Figs. 1B and 1D, the voltage is
applied between the common electrode 2 and the pixel
electrode 11 formed on the substrate 1 to form an
electric field (the direction 16 of electric field) in
a direction nearly in parallel with the interface of
the substrates 1, 1'. Then, the liquid crystal
molecules 21 are oriented and rotated in a plane nearly
in parallel with the interface of the substrates 1, 1' .
Accordingly, the pixel is placed in a display
(turned-on) state. A large number of pixels are
arranged to constitute a display device.

Figs. 2A to 2C are diagrams illustrating the
structure of a TFT substrate which constitutes a liquid
crystal display device of an embodiment of the present
invention, wherein Fig. 2A is a plan view, Fig. 2B is a
sectional view taken along the line A-A' of Fig. 2A,
and Fig. 2C is a sectional view taken along the line
B-B' of Fig. 2A.
In Figs. 2A to 2C, the same reference numerals as
those of Figs. 1A to 1D denote the same portions,
reference numeral 3 denotes a common wiring, 4 denotes
a scanning electrode, 5 denotes a scanning wiring, 6
denotes an insulating film, 7 denotes a semiconductor
layer, 8 denotes a thin-film transistor portion (TFT
portion), 10 denotes a signal wiring, 11 denotes pixel
electrodes, and 12 denotes a protective film.
The scanning electrode 4, scanning wiring 5,
common electrodes 2 and common wiring 3 are provided in
the same layer and are made of the same material. The
semiconductor layer 7 is formed via the thin layer and
the insulating film 6, and the signal wiring 10 and the
pixel electrode 11 are formed in the same layer using
the same material.
Part of the pixel electrode 11 is so arranged as
to overlap with the common wiring 3 in a direction
perpendicular to the surface of the substrate via the

insulating film 6, creating a capacitance to hold a
signal voltage that is applied between the pixel
electrode 11 and the common electrode 2.
Fig. 3 is a diagram illustrating an example of
the structure of the color-filter substrate
constituting the liquid crystal display device
according of the embodiment 1 of the present invention,
wherein the same reference numerals as those of Figs.
1A to 1D denote the same portions.
As shown in Fig. 3, the color filter substrate
has a plurality of color filters (R G. B) demarcated by
the black mask 17 on one surface of the transparent
substrate 1', and further has the protective film
(smoothing layer) 19 and the orientation film 20'
" formed thereon. The polarizer plate 13' is deposited
on the other surface of the transparent substrate 1'.
When the liquid crystal layer has a resistivity
of not smaller than 10N Ω.cm, the black mask 17
demarcating a plurality of color filters R, G and B
must have a resistivity of not smaller than 10M Ω.cm,
satisfying the relationships N > 9 and M > 6, where N
and M are integers.
When the liquid crystal layer and the black mask
have such resistivities, the electric field pattern
formed by the selection voltage applied between the

common electrode and the pixel electrode has an
effectively increased component nearly in parallelwith
the interface between the liquid crystal layer and the
orientation film, and makes it possible to suppress the
rise of the drive voltage. Furthermore, occurrence of
domains is greatly decreased, and high-contrast display
is obtained.
Fig. 4 is a sectional view schematically
illustrating an electric field pattern of a pixel that
constitutes the liquid crystal display device of the
embodiment 1 according to the present invention,
wherein the lines of electric force generated between
the common electrode 2 and the pixel electrodes 11 are
not affected by the black mask 17, the electric field
pattern is nearly in parallel with the interface
between the liquid crystal layer and the orientation
film, occurrence of domains is greatly decreased at the
positions of the pixel electrodes 11 and at the
position of the common electrodes 2, the transmission
factor is enhanced in the open region of the pixel, and
a high-contrast display is obtained.
The same effects are produced even when the
liquid crystal layer has a resistivity of not smaller
than 10N Ω.cm and the black mask has a resistivity of
not smaller than 10M Ω.cm (N and M are integers),

satisfying the relationships N > 13 and M > 7.
In embodiment 1, the material of the black mask
is blended with a mixture of an organic pigment and
carbon; i.e., the amount of carbon is adjusted so that
the above-mentioned desired resistivity is obtained.
Fig. 5 is a diagram illustrating the drive
voltage relative to the resistivity of the black mask
of when the resistivities of the liquid crystal layer
and of the black mask of the aforementioned embodiment
1 are changed.
In Fig. 5, assuming that the allowable value of
drive voltage increase relative to the allowable value
of transmissivity change, which s hould be less than
one gray scale level, is not larger than 0.1 volt, the
resistivity of the black mask must be higher than 3 x
106 Ω.cm when the liquid crystal has a resistivity of
109 fi-cm, and the resistivity of the black mask must be
higher than 5 x 107 Ω.cm when the liquid crystal has a
resistivity of 1013 Ω.cm.
From these facts, the aforementioned effects are
obtained by determining the values M and N satisfying
the relationships N > 9 and M > 6 or N > 13 and M > 7.
When the black mask contains carbon, the
resistivity decreases with an increase in the amount of
carbon that is contained and increases with a decrease

in the amount of carbon. An increase in the amount of
carbon results in an increase in the optical density
(hereinafter referred to as OD value). However, since
carbon is electrically conductive, it decreases the
resistivity.
That is, the amount of carbon must be so set as
to satisfy the above-mentioned mutually conflicting
requirements.
Fig. 6 is a diagram illustrating a relationship
between the resistivity change of the black mask
depending upon the amount of carbon and the OD value of
the black mask of when the film thickness is 1 μm
wherein curve a represents the resistivity of the black
mask, and curve b represents the OD value.
In Fig. 6, the abscissa represents the amount of
carbon (relative value) in the black mask, the ordinate
of the left side represents the resistivity (Ω.cm) of
the black mask and the ordinate of the right side
represents the OD value of when the film thickness is 1
μm.
From the relationship between the resistivity
that varies depending upon the amount of carbon and the
optical density (OD value) shown in Fig. 6, it is
understood that the resistivity of the black mask
becomes not smaller than 106 Ω.cm when the relative

amount of carbon is about 50, and the OD value can be
determined to be more than 1.6 which is practically-
satisfactory.
As described earlier, the material of the black
mask contains a mixture of organic pigment and carbon,
and the mixing ratio of carbon is adjusted to ,
accomplish the resistivity that lies within the
above-mentioned range. The present invention, however,
is in no way limited thereto only but a desired
resistivity can be accomplished by using other
light-absorbing materials.
That is, in another embodiment 2 as shown in Fig.
3, the black mask 17 demarcating a plurality of color
filters R, G, B can be formed by a known lithographic
method by using a resist that contains particles of a
tricobalt tetroxide (CO304) as particles of cobalt
oxide.
It is further possible to use a resist that
contains tricobalt tetroxide and either or both of an
organic pigment and carbon (chiefly graphite).
It is further possible to use a resist containing
any one of chromium oxide, manganese oxide and nickel
oxide.
The mixing ratio of the components of the resist
is so adjusted that the black mask 17 has a resistivity

of not smaller than 106 Ω.cm.
Since the metal oxide particles such as cobalt
oxide particles are contained in the black mask, the
light absorption factor can be further increased,
maintaining a large resistivity of the black mask.
Then, the liquid crystal molecules rotate in a plane
nearly in parallel with the interface, making it
possible to suppress the occurrence of so-called
domains and the rise of the drive voltage and enabling
the light transmission factor to be enhanced.
Fig. 7 is a sectional view illustrating an
essential portion of the color-filter substrate used in
a further embodiment 3.
The color filters of Fig. 7 have the black mask
BM made of a polyimide-type resin and formed on the
glass substrate SUB2; i.e., color filters (pixels)
FIL(R), FIL(G) and FIL(B) demarcated by the black mask
BM are provided.
Fig. 8 is a diagram schematically illustrating
the steps of forming the black mask shown in Fig. 7,
wherein PBM denotes a polyimide photosensitive resin
film, MSIC denotes a photomask for exposing the black
mask, hv denotes ultraviolet rays, and BM' denotes a
black mask pattern.
The above-mentioned polyimide photosensitive

resin is, for example, a photosensitive polyimide resin
Ddp-1120(s)(trade name) manufactured by Nitto Denko
Corp.
In Fig. 8, a glass substrate SUB2 that serves as
a color-filter substrate is prepared (step A), and a
polyimide photosensitive resin film PBM is uniformly
applied onto the glass substrate SUB2 by a spin-coating
method (step B).
The polyimide photosensitive resin film PBM is
prebaked at about 70°C for about 15 minutes and is
dried.
Next, ultraviolet rays hv are applied via a
photomask MSK having openings corresponding to the
pattern of arrangement of black masks (step C). Here,
the energy for the exposure is about 500 mJ/cm2. Due
to the exposure, the portions irradiated with
ultraviolet rays undergo the crosslinking reaction and
the resin is cured.
After the exposure, the polyimide photosensitive
resin film PBM is heat-treated in an oven at 180°C for
10 minutes or on a hot plate 180°C for two minutes.
Due to the heat-treatment, the density of the polyimide
photosensitive resin film PBM increases and the film
PBM exhibits increased light-shielding ability.
After the heat-treatment, the polyimide

photosensitive resin film PBM is developed with a
developing solution to remove the portions that are not
irradiated with ultraviolet rays, whereby a black mask
pattern BM' made of the polyimide resin is formed (step
D).
Finally, the black mask pattern BM' is cured at
350°C to 400°C for about one hour to form the black
mask BM (step E).
The processing conditions in the above-mentioned
steps are merely examples and can be changed depending
upon the thickness of the film that is applied and the
blackness that is required.
The polyimide resin film is blackened by being
cured by heat in the step of heat-treatment after the
exposure to light. The principle of blackening has
been disclosed in Omote Toshihiko, Hayashi Shunnichi,
Fujii Hirobumi, "Polymer Preprints, Japan", Vol. 41,
No. 7, 1992, pp. 2836-2838.
As described earlier, the material constituting
the black mask is the polyimide resin not containing
electrically conductive material. Therefore, the black
matrix exhibits a large resistance.
Then, the pixels (RGB) are formed. As required,
furthermore, a flattening film or a protective layer is
formed thereon to obtain a color-filter substrate.

In the inplane electric field liquid crystal
element described earlier, the opposing electrodes are
not required on the side of the color-filter substrate.
Next, a process for forming color filters of
various colors on the color-filter substrate having a
black mask formed by the above-mentioned processing
will be described below.
Fig. 9 is a diagram illustrating the steps of
producing the color-filter substrate used for the color
liquid crystal display device according to the
embodiment 3.
First, the black matrix is formed on the glass
substrate, using the process explained with reference
to Fig. 8.
The pattern" of the black mask serves as a
reference of the whole dimensional precision and for
forming the color filters (pixels).
The thickness of the black mask is determined
depending upon the optical properties thereof, i.e.,
depending upon the light-shielding ability. In the
embodiment 3, the thickness of the black mask is about
1.0 to about 1.5 μm.
A red pigment-dispersed resin material is applied
by spin-coating or the like method onto the substrate
on which the black mask has been formed, and is exposed

to ultraviolet rays via an exposure mask having an
opening corresponding to the red filter. The material
is developed to leave the exposed portions, cured and
dried by postbaking to form a red filter FIL(R).
Next, a green pigment-dispersed resin material is
applied by spin-coating or the like method, and is
exposed to ultraviolet rays via an exposure mask having
an opening corresponding to the green filter. The
material is developed to leave the exposed portions,
cured and dried by postbaking to form a green filter
FIL(G).
Similarly, a blue pigment-dispersed resin
material is applied by spin-coating or the like method,
and is exposed to ultraviolet rays via an exposure mask
having an opening corresponding to the blue filter.
The material is developed to leave the exposed
portions, cured and dried by postbaking to form a blue
filter FIL(B).
Through these steps, color filters of three
colors demarcated by the black mask BM are formed.
According to the embodiment 3, the black mask
formed among the pixels exhibit a high light absorption
factor, making it possible to provide a color liquid
crystal display device having an excellent contrast and
a high reliability.

In this embodiment, when the black mask has a
resistivity of not smaller than 107 Ω.cm, a coloring
agent may be added to the color-filter material to
control the transmission factor.
The coloring agents to be added to the resin-type
black mask material may be graphite, carbon, red, green
and blue pigments,or metal oxide particles.
Among the above-mentioned coloring agents,
pigments have little electrical conductivity.
Therefore, addition of the pigments makes it possible
to compensate for low absorption factor among the
spectral characteristics of the polyimide-type resin.
An increase in the amount of graphite or carbon
to increase the light-shielding ability results in an
increase in the electric conductivity. Therefore,
limitation is imposed on the amount of their addition.
The amount of addition, however, also varies
depending upon the resistance of the resin that is
used, the resistance of the material that is added, and
the size (particle diameter).
In particular, graphite and carbon have high
light-shielding ability and are preferable for
increasing the OD (optical density) value.
As the black coloring agent, furthermore, use is
made of metal oxide particles such as of-the

aforementioned cobalt oxide, chromium oxide, manganese
oxide or nickel oxide, thereby to form a black mask
that exhibits a high light absorption factor, a light-
shielding ability and a high resistivity.
According to the embodiment 3 as described above,
the color-filter substrate is fabricated by using the
polyimide photosensitive resin to provide a color
liquid crystal surface having a high contrast.
A more specific constitution of the present
invention will be described.
Fig. 10 is a diagram illustrating the connection
of an equivalent circuit of a display matrix unit in
the liquid crystal display device of the present
invention and the peripheral circuits.
In Fig. 10, symbol AR denotes a matrix array in
which a plurality of pixels are two-dimensionally
arranged, X denotes drain lines DL, and subscripts G,
B, R denote pixels of green blue and red colors.
Symbol DTM denotes drain terminals, GTM denotes
gate terminals, Y denotes gate lines GL, and subscripts
1, 2, 3, , end are in the order of the scanning
timings. The gate lines Y (subscripts are omitted) are
connected to a gate driver unit V.
The drain lines X (subscripts are omitted) are
connected to a drain driver unit H arranged along one

of the long sides of the display panel, and terminals
are led out from one side only of the liquid crystal
display panel like the gate lines Y.
SUP includes a power supply unit for obtaining
stabilized voltages as basic gray-scale levels whose
voltages are generated by dividing the voltage of a
voltage supply, and a converter for converting
information for the CRT (cathode-ray tube) from a host
(host arithmetic unit) into information for the TFT
liquid crystal display device.
Fig. 11 is an exploded perspective view
illustrating the constitution of the liquid crystal
display device according to the present invention,
i.e., specifically illustrating the structure of the
liquid crystal display device (hereinafter referred to
as module in which the liquid crystal display panel,
circuit board, backlight and other constituent members
are combined as a unitary structure: MDL).
In Fig. 11, symbol SHD denotes a shielded case
(also referred to as a metal frame) made of a metal
plate, WD denotes a display window, INS1 to INS3 denote
insulating sheets, PCB1 to PCB3 denote circuit boards
(PCB1 is a circuit board on the drain side or a circuit
board for drain driver, PCB2 is a circuit board on the
gate side, PCB3 is an interface circuit board), JN1 to

JN3 denote joiners for electrically connecting the
circuit boards PCB1 to PCB3 together, TCP1 and TCP2
denote tape carrier packages, PNL denotes a liquid
crystal display panel, GC denotes a rubber cushion, ILS
denotes a light-shielding spacer, PRS denotes a prism
sheet, SPS denotes a diffusion sheet, GLB denotes a
light-guide plate, RFS denotes a reflection sheet, MCA
denotes a lower case (molded frame) formed by one-piece
molding, MO denotes an opening of the MCA, LP denotes a
fluorescent lamp, LPC denotes a lamp cable, GB denotes
a rubber bush for supporting the fluorescent lamp LP,
BAT denotes a double-sided adhesive tape, and BL
denotes a backlight comprising a fluorescent lamp , a
light-guide plate and so on. Each part is stacked
maintaining a relationship as shown thereby to assemble
the liquid crystal display module MDL.
The liquid crystal display module MDL has two
kinds of accommodating/holding members, i.e., a lower
case MCA and a shielded case SHD. The metallic
shielded case SHD accommodating and holding the
insulating sheets INS1 to INS3, the circuit boards PCB1
to PCB3, and the liquid crystal display panel PNL is
joined to the lower case MCA holding the backlight BL
made up of the fluorescent lamp LP, the light-guide
plate GLB, the prism sheet PRS and so on.

On the circuit board PCB1 for drain driver is
mounted an integrated circuit chip for driving the
pixels of the liquid crystal display panel PNL, and on
the interface circuit board PCB3 are mounted an
integrated circuit chip for receiving video signals
from the external host and for receiving control
signals such as timing signals, and a timing converter
TCON for generating clock signals by processing timing
signals.
The clock signals generated by the timing
converter are fed to the integrated circuit chip
mounted on the circuit board PCBl for drain driver via
a clock signal line CLL laid on the interface circuit
board PCB3 and on the circuit board PCBl for drain
driver.
The interface circuit board PCB3 and the circuit
board PCBl for drain driver are multilayer wiring
boards, and the clock signal line CLL is formed as an
inner-layer wiring in the interface circuit board PCB3
and in the circuit board PCBl for drain driver.
The circuit board PCBl on the drain side for
driving TFTs, the circuit board PCB2 on the gate side
and the interface circuit board PCB3 are connected to
the liquid crystal display panel PNL by tape carrier
packages TCP1, TCP2, and the circuit boards are

connected together by joiners JN1, JN2 and JN3.
The liquid crystal display panel PNL is an
inplane electric field liquid crystal display device of
the present invention, and the black mask formed on the
color-filter substrate has a large resistivity so that
an electric field pattern is formed between a pixel
electrode and a common electrode almost in parallel
with the interface of the liquid crystal layer.
Fig. 12 is a diagram showing the appearance of a
personal computer for explaining an information
processing device having a liquid crystal display
device of the present invention, wherein IV denotes an
inverter power supply for driving a fluorescent lamp
and CPU denotes a central processing unit on the host
side.
As shown in Fig. 12, the personal computer
equiped with the liquid crystal display device of the
present invention has the circuit board for drain
driver (circuit board for horizontal driver: circuit
board on the drain side) PCB1 disposed at only the
upper portion of the screen, leaving a margin in space
on the lower side (keyboard side) of the display unit.
Therefore, the space (hinge space) required to install
hinges for coupling the keyboard unit and the display
unit together can be small. This makes it possible to

decrease the outer size of the display unit and, hence,
to reduce the size of the personal computer as a whole.
According to the present invention as described
above, the electric field created by the signal voltage
in the so-called inplane electric field liquid crystal
display device does hardly interfere with the black
mask. Therefore, the electric field pattern formed by
the selection voltage applied between the common
electrode and the pixel electrodes is nearly in
parallel with the interface between the liquid crystal
layer and the orientation film, making it possible to
suppress the rise of the drive voltage. Since the
electric field pattern is not disturbed, the domains do
not occur, and the liquid crystal display device has a
high picture quality without nonuniformity in color.
The present invention is not limited to the
liquid crystal display device of the TFT-type only but
can be applied to the liquid crystal display devices of
any other type inclusive of the active matrix type and
the so-called simple matrix type.
In this embodiment, furthermore, the black mask
is formed on one substrate side, and a group of
electrodes are formed on the other substrate to
generate an electric field nearly in parallel with the
substrates. They, however, may be formed on the same

substrate in compliance with the present invention, as
a matter of course.

WE CLAIM
CLAIMS:
1. A liquid crystal display device comprising a
black mask formed on one of a pair of substrates at
least one of which is transparent, a group of
electrodes formed on at least one of said pair of
substrates, a liquid crystal layer comprising a liquid
crystal composition substance having a dielectric
anisotropy and held between said pair of substrates, an
orientation control film formed between said liquid
crrystal layer and one of said substrates for orienting
liquid crystal molecules of said liquid crystal
composition substance in a predetermined direction, a
polarizing means laminated on at least one of said pair
of substrates, and a drive means for applying a drive
voltage to said group of electrodes, wherein said group
of electrodes has a structure that the electrodes are
so arranged as to generate an electric field having a
component predominantly in parallel with the interface
between said orientation control film and said liquid
crystal layer, said liquid crystal composition
substance has a resistivity of not smaller than 10N
Ω.cm, and said black mask has a resistivity of not
smaller than 10M Ω.cm, wherein N and M are integers
satisfying the relationships N > 9 and M > 6.

2. A liquid crystal display device comprising a
black mask formed on one of a pair of substrates at
least one of which is transparent, a group of
electrodes formed on at least one of said pair of
substrates, a liquid crystal layer comprising a liquid
crystal composition substance having a dielectric
anisotropy and held between said pair of substrates,
an orientation control film formed between said liquid
crrystal layer and one of said substrates for orienting
liquid crystal molecules of said liquid crystal
composition substance in a predetermined direction, a
polarizing means laminated on at least one of said pair
of substrates, and a drive means for applying a drive
voltage to said group of electrodes, wherein said group
of electrodes has a structure that the electrodes are
so arranged as to generate an electric field having a
component predominantly in parallel with the interface
between said orientation control film and said liquid
crystal layer, said liquid crystal composition
substance has a resistivity of not smaller than 10N
Ω.cm, and said black mask has a resistivity of not
smaller than 10M Ω.cm, wherein N and M are integers
satisfying the relationships N > 13 and M > 7.
3. A liquid crystal display device according to

claim 1 or 2, wherein metal oxide particles are
contained in said black mask.
4. A liquid crystal display device according to
claim 3, wherein said metal oxide particles are
parrticles of at least one of cobalt oxide, chromium
oxide, manganese oxide and nickel oxide.
5. A liquid crystal display device according to
claim 3, wherein either or both of an organic pigment
and a graphite powder in addition to said metal oxide
particles are contained in said black mask.
6. A liquid crystal display device according to
claim 4, wherein said cobalt oxide particles are
chiefly tricobalt tetroxide particles.
7 . A liquid crystal display device according to
claim 4, wherein any one of chromium oxide, manganese
oxide and nickel oxide is contained in addition to said
cobalt oxide.
8. A liquid crystal display device according to
claim 1 or 2, wherein the base material of said black
mask is made of a polyimide resin.

9. A liquid crystal display device according to
claim 8, wherein the composition of said polyimide
resin material contains a component that is cured by
light and a component that is cured by heat, and the
optical density of said black mask increases as said
resin material is cured by heat.
10. A liquid crystal display device according to
claim 8 or 9, wherein said black mask is composed of a
polyimide resin material which contains at least one or
more kinds of black coloring agents and other coloring
agents different from said black coloring agents.
11. A liquid crystal display device according to
claim 8 or 9, wherein said black mask is composed of a
polyimide resin material in which are mixed metal oxide
particles as a black coloring agent.

The light-shielding ability of the black mask is
practically satisfactory, and the disturbance of the
electric field pattern is eliminated, achieving display
of high quality picture without color nonuniformity.
A liquid crystal display device comprising a
black mask formed on one of a pair of substrates at
least one of which is transparent, a group of
electrodes formed on at least one of the pair of
substrates, a liquid crystal layer comprising a liquid
crystal composition substance having a dielectric
anisotropy and held between the pair of substrates, an
orientation control film formed between the liquid
crrystal layer and one of the substrates for orienting
liquid crystal molecules of the liquid crystal
composition substance in a predetermined direction, a
polarizing means laminated on at least one of the pair
of substrates, and a drive means for applying a drive
voltage to the group of electrodes, wherein the group
of electrodes has a structure that the electrodes are
so arranged as to generate an electric field having a
component predominantly in parallel with the interface
between the orientation control film and the liquid
crystal layer, the liquid crystal composition substance
has a resistivity of not smaller than 10N Ω.cm, and the

black mask has a resistivity of not smaller than 10M
Ω.cm, wherein N and M are integers satisfying the
relationships N > 9 and M > 6.