JP2000105382A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent display failure due to AC afterimages and to obtain a high quality image display. SOLUTION: In this liquid crystal display device, transparent substrates are disposed facing each other through a liquid crystal, and an alignment film is formed with a protective film adhered on the surface of the transparent substrate facing to the liquid crystal. The add amt. of the coupling agent which added adhesion property to the alignment film is controlled to <=2% of the solid concn. The degree of AC afterimages is preferably controlled <=8%. The coupling agent used is an org. silicon compd. containing at least either polymer or oligomer in which at least one molecular end is an org. functional group such as amino groups, vinyl groups, methacryloxy groups, epoxy groups and mercapto groups or hydrolyzable alkxoy groups or acetoxy groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to an improvement in an alignment film.

[0002]

2. Description of the Related Art A liquid crystal display device has a structure in which a pair of transparent substrates disposed opposite to each other via a liquid crystal are used as an envelope, and a large number of pixels are formed in a direction in which the liquid crystal spreads.

Each of these pixels is provided with, for example, a pixel electrode on one of the transparent substrates and an opposing electrode separated from the pixel electrode. Some devices control the light transmittance of the liquid crystal.

A so-called lateral electric field method is known in which a display having a so-called wide viewing angle can be achieved by controlling the amount of light transmission by causing the liquid crystal molecules to be twisted by the electric field. Are known.

In this case, in order to determine the initial alignment of liquid crystal molecules, for example, an alignment film is formed on a protective film formed by covering the electrodes and the like, and the liquid crystal comes into direct contact with the alignment film. I have.

The details of the liquid crystal display device are described in, for example, Japanese Patent Publication No. Sho 63-21907, US Pat. No. 4,345,249, and European Patent Application No. 91/10936.
JP-A-6-222397 and JP-A-6-1608
No. 78 publication.

[0007]

However, the liquid crystal display device having the above-described structure can be subjected to a normal AC drive at a high temperature of, for example, 55.degree. Was observed, and it was found that this resulted in poor display.

Here, the AC drive is a system in which an AC voltage is used for a counter electrode and a video signal (voltage) is supplied to a pixel electrode with reference to the voltage of the counter electrode, in order to avoid polarization of liquid crystal molecules. It is a technique of.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid crystal display device capable of avoiding occurrence of an afterimage visually observed and thereby achieving high quality image display. Is to do.

[0010]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, in a liquid crystal display device in which an alignment film is formed by adhering a protective film to a surface of a transparent substrate opposed to each other via a liquid crystal on the liquid crystal side, the adhesion of the alignment film is imparted. The addition amount of the coupling agent is 2% or less with respect to the solid content concentration.

The liquid crystal display device has such a configuration for the following reason.

[0013] A coupling agent is added to the alignment film in order to improve the adhesion to a protective film (formed by covering the electrode) for bonding the alignment film.

However, it is sufficient if the coupling agent can secure the adhesiveness with the protective film, and the minimum amount of the coupling agent has not been considered at present.

For this reason, it was confirmed that a rather large amount of coupling agent was contained in the alignment film, and this caused the occurrence of an afterimage visually.

That is, the excess coupling agent is raised on the surface of the alignment film in contact with the liquid crystal, and the raised coupling agent causes hysteresis in the behavior of the molecules of the liquid crystal.

For this reason, the amount of the coupling agent contained in the alignment film is suppressed, thereby preventing the coupling agent from adversely affecting the behavior of the liquid crystal molecules.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal display device according to the present invention will be described below with reference to the drawings.

[Equivalent Circuit of Apparatus] FIG. 1 is a circuit diagram, which is drawn corresponding to an actual geometric arrangement.

In FIG. 1, there is a so-called active matrix type liquid crystal display panel 100 first. Note that the liquid crystal display panel 100 shows only one transparent substrate 1A in the figure, and the transparent substrate and the other transparent substrate via a liquid crystal constitute an envelope of the liquid crystal display panel 100.

The liquid crystal display panel 100 has a display section constituted by a set of a plurality of pixels arranged in a matrix.
The transmission light from a backlight unit (not shown) disposed at the back of the 00 is independently modulated and controlled.

The light modulation in each pixel employs a method called a lateral electric field method, and its structure will be described in detail later. The electric field to be generated is parallel to the transparent substrate.

Such a liquid crystal display panel 100 is known to be capable of recognizing a clear image even when observed from a large angle field of view with respect to its display surface, and to be excellent in a so-called wide angle field of view.

That is, one of the transparent substrates 1A extends on the liquid crystal side surface in the x direction (row direction) and extends in the y direction (column direction).
Are formed in parallel with each other.

In this case, in FIG. 2, a scanning signal line 2, a reference signal line 4 relatively separated from the scanning signal line 2 from above the transparent substrate 1A, and a scanning signal close to the reference signal line 4 are shown. Line 2, reference signal lines 4, which are relatively spaced apart from the scanning signal line 2, and so on.

A video signal line 3 which is insulated from the scanning signal line 2 and the counter voltage signal line 4 and extends in the y direction and is arranged in the x direction is formed.

Here, a unit pixel is formed in a rectangular region having a relatively large area surrounded by the scanning signal line 2, the reference signal line 4, and the video signal line 3, and these unit pixels are formed. Are arranged in a matrix to form a display surface.

Each pixel has a thin film transistor T driven by the supply of a scanning signal (voltage) from the scanning signal line 2.
An FT and a pixel electrode 18 to which a video signal (voltage) from the video signal line 3 is applied by driving the thin film transistor TFT are provided. The detailed configuration of this pixel will be described later.

The liquid crystal display panel 100 is provided with a vertical scanning circuit 5 and a video signal driving circuit 6 as external circuits, and the vertical scanning circuit 5 sequentially supplies a scanning signal to each of the scanning signal lines 2. The video signal is supplied from the video signal drive circuit 6 to the video signal line 3 in accordance with the timing.

The vertical scanning circuit 5 and the video signal driving circuit 6 are adapted to receive image information from, for example, a CPU via a controller 8, and each of the counter voltage signal lines 4 has a reference voltage. A reference voltage signal is supplied from the voltage signal source 9.

[Configuration of Pixel] FIG. 2 is a plan view showing an embodiment of the unit pixel (corresponding to a region surrounded by a dashed line in FIG. 1). FIG. 3 is a cross-sectional view taken along the line III-III in FIG.

In FIG. 2, on the main surface of the transparent substrate 1A,
An opposing voltage signal line 4 extending in the x direction, and a scanning signal line 2 formed relatively parallel to and in parallel with the opposing voltage signal line 4 in the (-) y direction.

Here, three opposing electrodes 14 are integrally formed on the opposing voltage signal line 4. That is, two of the opposing electrodes 14 are in the y-direction side of a pixel region formed by a pair of video signal lines 3 to be described later, that is, in the (+) y direction in proximity to the respective video signal lines 3. It is formed to extend to the vicinity of the scanning signal line 2, and the other one is formed between them.

The transparent substrate 1A on which the scanning signal line 2, the counter voltage signal line 4, and the counter electrode 14 are formed.
An insulating film 15 (see FIG. 3) made of, for example, a silicon nitride film is formed on the surface of the semiconductor device so as to cover the scanning signal lines 2 and the like. This insulating film 15 is a thin film transistor TFT as an interlayer insulating film at an intersection with the scanning signal line 2 and the counter voltage signal line 4 for a video signal line 3 described later.
Is formed as a gate insulating film for the formation region of the storage capacitor C.
The stg formation region functions as a dielectric film.

First, the semiconductor layer 16 is formed on the surface of the insulating film 15 in the region where the thin film transistor TFT is formed.
Are formed. The semiconductor layer 16 is made of, for example, amorphous Si, and is formed on the scanning signal line 2 so as to overlap a portion close to the video signal line 3. As a result, a part of the scanning signal line 2 is
Is also configured as a gate electrode.

On the surface of the insulating film 15 thus formed, as shown in FIG. 2, the video signal lines 3 extending in the y direction and juxtaposed in the x direction are formed. .

The video signal line 3 is integrally provided with a drain electrode 3A formed so as to extend to a part of the surface of the semiconductor layer 16 of the thin film transistor TFT.

Further, a pixel electrode 18 is formed on the surface of the insulating film 15 in the pixel region. This pixel electrode 1
8 is formed so as to run between the opposed electrodes 14. That is, one end of the pixel electrode 18 also serves as the source electrode 18A of the thin film transistor TFT, extends in the x direction along the counter voltage signal line 4 in parallel, and passes between the respective counter electrodes 18 from this extending portion ( -) It is formed so as to extend in the y direction.

In this case, the pixel electrode 18 has a portion superimposed on the counter voltage signal line 4, and forms a storage capacitor Cstg including the insulating film 15 as a dielectric film between the pixel electrode 18 and the counter voltage signal line 4. are doing. The storage capacitor Cstg has an effect of storing video information in the pixel electrode 18 for a long time when, for example, the thin film transistor TFT is turned off.

The surface of the semiconductor layer 16 corresponding to the interface between the drain electrode 3A and the source electrode 18A of the above-described thin film transistor TFT is doped with phosphorus (P) to form a high concentration layer. Ohmic contact at the electrode is achieved. In this case, the high concentration layer is formed on the entire surface of the semiconductor layer 16,
After each of the electrodes is formed, the above structure can be obtained by etching the high-concentration layer other than the electrode formation region using the electrodes as a mask.

Then, as described above, the thin film transistor TF
T, video signal line 3, pixel electrode 18, storage capacitor Cstg,
A protective film 19 (see FIG. 3) made of, for example, a silicon nitride film is formed on the upper surface of the insulating film 15 on which the antireflection film 10 is formed, and an alignment film 20 is formed on the upper surface of the protective film 19. , Transparent substrate 1 of liquid crystal display panel 100
A. The alignment film 2 of the transparent substrate 1A
A polarizing plate is formed on the surface opposite to 0.

Further, a light-shielding film is formed at a portion corresponding to a boundary portion of each pixel region on a surface on the liquid crystal side of another transparent substrate which is disposed to face the transparent substrate 1A via the liquid crystal. The light-shielding film has a function of preventing the thin film transistor TFT from being directly irradiated with light and a function of improving display contrast.

Further, a color filter is formed so as to cover the opening of the light-shielding film. The color filter has a color different from that of the pixel region adjacent in the x direction and has a boundary on the light-shielding film. It has become. Further, a flat film made of a resin film or the like is formed on the surface on which the color filters are formed, and an alignment film is formed on the surface of the flat film. A polarizing plate is formed on the surface of the transparent substrate opposite to the alignment film.

[Relationship Between Alignment Film and Polarizing Plate] Here, the relationship between the alignment film 20 formed on the transparent substrate 1A and the polarizing plate and the relationship between the alignment film formed on the other transparent substrate and the polarizing plate is shown. 4 will be described.

With respect to the direction E of the electric field applied between the display electrode 18 and the reference electrode 14, the angle of the rubbing direction 19 of the alignment film 20 and the alignment film of another transparent substrate is f.
LC. Further, the angle of the polarization transmission axis direction 20 of the polarizing plate on the transparent substrate 1A side is fP. The polarization transmission axis of the polarizing plate on the other transparent substrate side is orthogonal to fP. Also, fLC = fP. As a liquid crystal, the dielectric anisotropy Δε is positive and its value is 7.3 (1 kHz).
z), the refractive index anisotropy Δn is 0.073 (589 nm, 2
0 ° C.).

The relationship between each alignment film and each polarizing plate and the like having such a relationship is what is called a normally black mode. By generating an electric field E parallel to the transparent substrate 1A in the liquid crystal, Light is transmitted through the liquid crystal. However, in this embodiment, the present invention is not limited to such a normally black mode, and it goes without saying that a normally white mode in which light transmitted through the liquid crystal layer LC when no electric field is applied may be the maximum. Absent.

<< Alignment Film >> As the alignment film 20 (the same applies to other alignment films on the transparent substrate side), for example, 2,2-bis [4- (p-aminophenoquine) phenylpropane] and pyromellitic acid A polyimide alignment film made of dihydrate is used. Its thickness is, for example, 50 nm.

Further, γ-aminopropyltrimethoxysilane, which is a silane coupling agent, is added in an amount of 0.8% based on the solid content of the alignment film varnish. The silane coupling agent will be described later in detail.

Materials other than the above-mentioned materials of the alignment film include the following.

That is, phenylenediamine, diphenylenediamine, triphenylenediamine, and the amine to be copolymerized with the tetracarboxylic dihydrate are used.

[0051]

(Equation 1)

(In the formula 1, X is a direct bond, —O—, —CH
_{2 -, - SO 2 -,} - CO -, - CO 2 -, - CONH-
Or a compound represented by the following general formula:

[0053]

(Equation 2)

Compounds having a structure represented by the formula (X is a direct bond in the formula 1), for example, bis (aminophenoquine) diphenyl compound and the like.

Specifically, p-phenylenediamine, m
-Phenylenediamine, 4,4'-diaminoterphenyl, 4,4'-diaminodiphenylsulfone, 3,3 '
-Diaminodiphenyl sulfone, 4,4'-diaminodiphenylbenzoate, 4,4'-diaminodiphenylmethane, 2,2 '-(4,4'-diaminodiphenyl)
Propane, 4,4'-bis (p-aminophenoxy) diphenylsulfone, 4,4'-bis (m-aminophenoxy) diphenylsulfone, 4,4'-bis (p-aminophenoxy) diphenylether, 4,4 ' -Bis (P-aminophenoxy) diphenyl ketone, 4,4 '
-Bis (P-aminophenoxy) diphenylmethane,
2,2 '-[4,4'-bis (p-aminophenoxy)
Diphenyl] propane also has the formula

[0056]

(Equation 3)

4,4'-diamino-3-carbamoyldiphenyl ether represented by the following formula, and a diaminosiloxane compound represented by the following formula:

[0058]

(Equation 4)

Examples of the diamine containing no halogen group which can be copolymerized with the above include, for example, 4,4
4'-diaminodiphenylether-3-carbonamide, 3-3'diaminodiphenylsulfone, 3-3'dimethyl-4-4'diaminodiphenylether, 1,6
-Diaminohexane, 2-2'-bis [4- (4-aminophenoxy) diphenyl] propane, 2-2'-bis [4- (4-aminophenoxy) phenyl] methane, 2
-2'-bis [4- (4-aminophenoxy) phenyl] sulfone, 2-2'-bis [4- (4-aminophenoxy) phenyl] ketone, 2-2'-bis [4- (4
-Aminophenoxy) phenyl] biphenyl, 2-2 '
-Bis [4- (4-aminophenoxy) phenyl] cyclohexane, 2-2'-bis [4- (4-aminophenoxy) phenyl] methylcyclohexane, bis [4-
(4-aminobenzoyloxy) benzoic acid] propane,
Bis [4- (4-aminobenzoyloxy) benzoic acid]
Cyclohexane, bis [4- (4-aminobenzoyloxy) benzoic acid] methylcyclohexane, bis [4-
(4-aminomethylbenzoyloxy) benzoic acid] propane, bis (4-aminobenzoyloxy) propane,
Bis (4-aminobenzoyloxy) methane, bis [2
-(4-aminophenoxy) phenyl] methane, bis [2- (4-aminophenoxy) -3,5-dimethylphenyl] methane, bis [2- (4-aminophenoxy)
-3,4,5-trimethylphenyl] methane, bis [2
-(4-aminophenoxy) -3,5,6-trimethylphenyl] methane, bis [2- (4-aminophenoxy) -3,5-diethylphenyl] methane, bis [2-
(4-aminophenoxy) -5-n-propylphenyl] methane, bis [2- (4-aminophenoxy) -5
-Isopropylphenyl] methane, bis [2- (4-aminophenoxy) -5-methyl-3-isopropylphenyl] methane, bis [2- (4-aminophenoxy)-
5-n-butylphenyl] methane, bis [2- (4-aminophenoxy) -5-isobutylphenyl] methane,
Bis [2- (4-aminophenoxy) -3-methyl-5
-T-butylphenyl] methane, bis [2- (4-aminophenoxy) -5-cyclohexylphenyl] methane, bis [2- (4-aminophenoxy) -3-methyl-5-cyclohexylphenyl] methane, bis [ 2-
(4-aminophenoxy) -5-methyl-3-cyclohexylphenyl] methane, bis [2- (4-aminophenoxy) -5-phenylphenyl] methane, bis [2-
(4-aminophenoxy) -3-methyl-5-phenylphenyl] methane, 1,1-bis [2- (4-aminophenoxy) -5-methylphenyl] methane, 1,1-bis [2- (4 -Aminophenoxy) -5-dimethylphenyl] ethane, 1,1-bis [2- (4-aminophenoxy) -5-methylphenyl] propane, 1,1-bis [2- (4-aminophenoxy) -3 , 5-Dimethylphenyl] propane, 2,2-bis [2- (4-aminophenoxy) phenyl] propane, 2,2-bis [2-
(4-aminophenoxy) -3,5-dimethylphenyl] propane, 1,1-bis [2- (4-aminophenoxy) -5-methylphenyl] butane, 2,2-bis [2- (4-amino) Phenoxy) -3,5-dimethylphenyl] butane, 1,1-bis [2- (4-aminophenoxy) -5-methylphenyl] -3-methylpropane, 1,1-bis [2- (4-amino) Phenoxy)-
3,5-dimethylphenyl] cyclohexane, 1,1-
Examples thereof include, but are not limited to, diamines such as bis [2- (4-aminophenoxy) -5-methylphenyl] -3--3-5-trimethylcyclohexane, and diaminosiloxane.

On the other hand, compounds of an acid component having a long-chain alkylene group and other copolymerizable compounds include, for example, octylsuccinic dianhydride, dodecylsuccinic dianhydride,
Octylmalonic dianhydride, decamethylene bis trimellitate dianhydride, decamethylene bis trimellitate dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] octyltetracarboxylic dianhydride Anhydride, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) phenyl] tridecanetetracarboxylic dianhydride, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl ] Tridecanetetracarboxylic dianhydride, stearic acid, stearic acid chloride, pyromellitic dianhydride, methyl pyromellitic dianhydride,
3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, dimethylene trimellitate dianhydride, 3,
3 ', 4,4'-biscyclohexanetetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylmethanetetracarboxylic dianhydride Anhydride, 3, 3 ', 4, 4'
-Diphenyl ether tetracarboxylic dianhydride, 3,
3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylpropanetetracarboxylic dianhydride Compound, 2,2-bis [4- (3,
4-dicarboxyphenoxy) phenyl] propanetetracarboxylic dianhydride, 2,2-bis [4- (3,4-
Dicarboxyphenoxy) phenyl] hexafluoropropanetetracarboxylic dianhydride, 2,2-bis [4-
(3,4-dicarboxybenzoyloxy) phenyl]
Propanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, bicyclo (2,2,2)
Octa-7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic acid And dianhydrides.

The orientation film is formed not only by the printing method but also by the printing method.
It can be easily formed by a wet method such as a spin coating method or a bar coating method. However, when the film is formed by a printing method in the same manner as a normal alignment film, patterning or the like after the film is formed becomes unnecessary, and productivity can be improved.

<< Silane Coupling Agent >> The silane coupling agent is preferably added at least 0.05% or more with respect to the solid concentration in order to secure the adhesiveness.

The silane coupling agent has the following general formula in addition to the above-mentioned materials.

[0064]

## EQU5 ## A structure represented by R-Si-X ₃ can be applied.

Here, R represents an organic functional group such as an amino group, a vinyl group, a methacryloxy group, an epoxy group or a mercapto group, and X is a hydrolyzable group such as an alkoxy group or an acetoxy group.

<< Measurement Conditions and Method for Liquid Crystal Display Panel >>
The presence or absence of an afterimage due to the pure AC driving of the liquid crystal display panel described above can be directly determined by measuring whether or not a change in BV characteristics (luminance-voltage characteristics) occurs during the pure AC driving. Become.

The change here means the initial luminance in the halftone when the luminance is measured in the same manner as the luminance-voltage characteristic after the white display is performed so that the luminance becomes the maximum display in the normal driving and the luminance is maintained for 30 minutes. B and the change in luminance B after holding for 30 minutes.

That is, when a change occurs in the BV characteristics, the BV characteristics after the display are different in the two regions where different displays are performed, and the BV characteristics are different even when the same voltage is input.
Since there is a difference in -V characteristics, a luminance difference occurs between the two regions, and this is observed as an afterimage.

FIG. 5 is a block diagram of a measurement system for evaluating the fluctuation of the BV characteristic, wherein 21 is a thermostat, 22 is an observation window (glass window), 23 is a digital multimeter, and 24 is a digital multimeter.
Is a measurement controller, 25 is a sample (liquid crystal display panel), 26 is a backlight, 27 is a common voltage power supply, 28 is a signal voltage source, and 29 is a gate voltage power supply.

The liquid crystal display panel 25 was measured together with the backlight 26 after the temperature was stabilized for 4 hours or more. The liquid crystal panel 25 is driven by a pure AC drive (AC drive) with a DC component of 0 by a common voltage of 0V.

The gate signal line of the liquid crystal display panel 25 is DC
Driving was performed, and +16 V was supplied. The common voltage was a constant value of 0V. The output from the luminance system was input as a luminance value to the measurement controller 24 by a digital multimeter.

Then, according to the following procedures (1) to (3), the fluctuation of the BV curve before and after the AC driving was measured.

(1) The luminance Bb (Vsig) is measured sequentially while increasing the signal voltage Vsig from 0V.

(2) Driving is performed for 30 minutes at the signal voltage Vmax at which the luminance becomes maximum.

(3) Measure the luminance Ba (Vsig) sequentially while lowering the signal voltage Vsig from Vmax to 0V.

As a result, the luminance fluctuation value ΔB (Vsig) before and after the pure AC driving is represented by ΔB (Vsig) (%) = [Ba (Vsig) −Bb (Vsig)] / Bb (Vsig) (1) Obtainable.

The measurement was performed at 55 ° C.

<< Measurement Result 1 >> As a result of the above measurement conditions and method, it was confirmed that good display characteristics were obtained when ΔB (Vsig) was 8% or less.

It was also confirmed that when the amount of the silane coupling agent added was 2% or less based on the solid content, the afterimage was 8% or less. In this case, the value of AC afterimage of 8% or less is a value based on the measurement error of 0.3%.

It has been confirmed that, when the coatability of the substrate is improved by a method such as UV / ozone irradiation during the formation of the alignment film, the alignment film can be more easily formed uniformly over the entire surface, and the coverage of the electrode is further improved. .

The cracks become larger when the passivation film is thin to some extent, and the coatability in the cracks is determined by UV.
It has also been confirmed that the coverage by the alignment film is further improved because the method can be easily improved by a method such as irradiation with ozone.

<< Measurement Results 2 to 13 >> In the following measurements, a liquid crystal display panel was prepared in which the type and amount of the silane coupling agent added to the alignment film were changed, and the same measurement conditions and methods as described above were used. The measurement result was obtained.

The results of these measurements (AC afterimages) are shown in FIG.

As can be seen from FIG. 6, the amount of the coupling agent added is 2 to the solid content concentration of the alignment film varnish.
% Or less, AC afterimages do not occur in any of the high temperature and operating temperature regions, and good display quality can be ensured.

Comparative Examples 1 to 3 FIG. 7 shows the same measurement conditions and method as described above, with the amount of the coupling agent added being 2% or more based on the solid content concentration of the alignment film varnish. Is the data obtained from the measurement results.

As can be seen from FIG. 7, the AC afterimage is 12% or more, and it is confirmed that the afterimage remains.

In the above embodiment, a so-called in-plane switching type liquid crystal display device has been described. But,
It goes without saying that the present invention can be applied to a vertical electric field type liquid crystal display device.

Here, the vertical electric field type liquid crystal display device is
A pixel electrode and a counter electrode are respectively provided in a pixel region on the liquid crystal side of a transparent substrate which is disposed to face each other with a liquid crystal therebetween. Of a structure that controls the light transmittance of the light.

[0089]

As described above, according to the liquid crystal display device of the present invention, it is possible to avoid the occurrence of an afterimage visually observed, and to obtain a high quality image display.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a plan view showing one embodiment of a pixel of the liquid crystal display device according to the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is an explanatory diagram showing a relationship between an alignment film and a polarizing plate of the liquid crystal display device according to the present invention.

FIG. 5 is a configuration diagram of a measuring device for evaluating the effect of the liquid crystal display device according to the present invention.

FIG. 6 is an experimental measurement showing the effect of the liquid crystal display device according to the present invention.

FIG. 7 shows experimental measurement values of a conventional liquid crystal display device.

[Explanation of symbols]

1A: transparent substrate, 13: insulating film, 14: counter electrode, 18: pixel electrode, 19: protective film, 20: alignment film.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 20, 1998 (1998.11.
20)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction contents]

FIG. 5 is a block diagram of a measuring system for evaluating the fluctuation of the BV characteristic, wherein 21 is a thermostat, 22 is an observation window (glass window), and 23 is a digital multimeter .
Luminance meter , 24 is a measurement controller, 25 is a sample (liquid crystal display panel), 26 is a backlight, 27 is a common voltage power supply,
28 is a signal voltage source, and 29 is a gate voltage power source.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tetsuya Nishio 3300 Hayano, Mobara-shi, Chiba Pref.Electronic Device Division, Hitachi, Ltd. (72) Inventor Shigeru Matsuyama 3300-Hayano, Mobara-shi, Chiba Pref. Department F-term (reference) 2H090 HB17Y HD11 4J035 BA02 CA062 CA112 CA132 CA142 CA19K CA19U CA191 CA192 CA262 EA01 GA06 GB05 LA05 LB20 4J043 PA02 PA04 PC065 PC066 QB15 QB26 QB31 RA35 SA06 SA15 SA43 SA04 SA46 SA22 TA2 UA2 TA2 UA2 TA2 UA121 UA122 UA131 UA132 UA141 UA151 UA152 UA262 UA652 UA662 UA672 UA761 UA762 UA772 UB011 UB012 UB021 UB022 UB062 UB122 UB131 UB132 UB141 UB151 VA152 UB111 VA1 UB1 UB1 UB1

Claims (6)

[Claims] 1. A liquid crystal display device comprising an alignment film adhered to a protective film on a liquid crystal side surface of a transparent substrate disposed to face each other via a liquid crystal, wherein the alignment film is provided with adhesiveness. A liquid crystal display device wherein the amount of the coupling agent added is 2% or less based on the solid content concentration. 2. The liquid crystal display device according to claim 1, wherein the amount of the coupling agent added is 0.05% or more based on the solid content concentration. 3. The liquid crystal display device according to claim 1, wherein an AC afterimage is 8% or less. 4. The liquid crystal display device according to claim 3, wherein the value of the AC afterimage of 8% or less is a value based on the measurement error of 0.3%. 5. The coupling agent according to claim 1, wherein at least one of the polymer and the oligomer has an organic functional group such as an amino group, a vinyl group, a methacryloxy group, an epoxy group, a mercapto group or a hydrolyzable alkoxy group and an atoxoxy group. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is an organic silicon compound containing at least one of them. 6. A pixel region of one of the transparent substrates includes a pixel electrode and a counter electrode separated from the pixel electrode, and a liquid crystal between the electrodes is generated by an electric field generated between the electrodes. The liquid crystal display device according to any one of claims 1 to 5, wherein the light transmittance is controlled.