JP2002040436A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that, although a polyimide alignment film having high elasticity is effective to decrease afterimages or image perssistence, the film surface of the above polyimide alignment film having high elasticity is generally extremely brittle and rubbing flaws or rubbing chips are caused in a rubbing process, which causes failure in the initial alignment of the liquid crystal or deterioration in the display performance such as the black level or the contrast due to the alignment failure. SOLUTION: The polyimide alignment film used is synthesized by using diamine having one or two cyclic structures and tetracarboxylic acid having one or two cyclic structures, wherein at least either the diamine or tetracarboxylic acid has one or more alkyl groups bonded to the cyclic structure. The obtained polyimide alignment film has high elasticity as well as rubbing durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an active matrix type liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device is constructed by arranging two glass substrates at a predetermined interval and injecting liquid crystal into a gap. A polymer thin film called an alignment film is disposed between the glass substrate and the liquid crystal layer, and an alignment process is performed to align the liquid crystal molecules. The display is performed by changing the alignment direction by applying an electric field to the arranged liquid crystal molecules, thereby changing the optical characteristics of the liquid crystal layer.

A conventional active drive type liquid crystal display device is:
An electrode is provided on each of a pair of substrates sandwiching the liquid crystal, and an alignment film subjected to an alignment treatment is formed thereon, and a direction of an electric field applied to the liquid crystal aligned substantially parallel to the substrate is substantially perpendicular to the substrate surface. And is represented by the TN mode in which display is performed by utilizing the optical rotation of liquid crystal. In this TN system, a narrow viewing angle is a major problem.

On the other hand, by using a comb-shaped electrode, the generated electric field has a component substantially parallel to the substrate surface, and the liquid crystal molecules are rotated in a plane substantially parallel to the substrate surface to reduce the birefringence of the liquid crystal. The IPS system for displaying by using is disclosed in JP-B-63-21
No. 907, US Pat. No. 4,345,249, and the like. In this method, since light is switched by rotating liquid crystal molecules in a plane, there is no inversion of gradation and color tone depending on the angle at which the screen is viewed (viewing angle).
The viewing angle is wider than the system. Further, this method has advantages such as low load capacity. I having such excellent viewing angle characteristics
The PS method is expected as a new liquid crystal display device replacing the conventional TN method, and is an important technology for large-screen liquid crystal panels and liquid crystal televisions in the future.

[0005] However, an IP having such excellent viewing angle characteristics is required.
The S method has not only an advantage but also a problem of deteriorating the liquid crystal display performance. Among them, a particularly important problem is a problem of display defects such as afterimages and image printing. The afterimage / image burn-in phenomenon is a phenomenon in which when the same image is displayed for a long time and then another image is displayed, the previously displayed image is displayed at the same time, deteriorating the performance as a liquid crystal display device. This is one of the factors that cause it. In a system such as an IPS system in which liquid crystal molecules are rotated in a plane substantially parallel to the substrate and light is switched to display an image, which is different from an afterimage generated due to residual charges observed in the conventional TN system. An afterimage phenomenon also occurs. The afterimage / image printing phenomenon which does not depend on the accumulated charge peculiar to the IPS system is disclosed in
As shown in Japanese Patent No. 406, it is considered that this is caused by the elastic deformation of the surface of the alignment film that regulates the initial alignment direction of the liquid crystal molecules due to the rotational torque generated by the in-plane torsional deformation of the liquid crystal molecules by the application of an electric field. ing. In fact, IP
A detailed examination of the liquid crystal alignment direction in the afterimage / image sticking region in the S-mode liquid crystal display device reveals that only those regions rotate by a certain angle in the driving direction as compared with the liquid crystal initial alignment direction (rubbing direction). You can see that there is. Afterimages and image sticking occur due to the disorder of the liquid crystal alignment, which causes a decrease in black level and a decrease in contrast.

As means for reducing image sticking and image sticking, which is considered to be mainly caused by the elastic deformation of the alignment film surface, Japanese Patent Application Laid-Open No. H10-319406 discloses the use of an alignment film having a large surface elastic modulus. Proposed. By using an alignment film having a high surface elastic modulus, elastic deformation of the alignment film surface can be reduced, and as a result, the afterimage and image sticking phenomena can be reduced.

Further, in the conventional IPS mode liquid crystal display device, since a comb-shaped metal material (for example, chromium) is used as an electrode for applying an electric field to the liquid crystal, light from the electrode portion is not transmitted. There is also a problem that the aperture ratio is low and the transmittance is low. As means to solve this problem,
For example, it is proposed in Japanese Patent Application Laid-Open No. 9-73101.
The means is a method of using a transparent conductive film such as ITO for at least one of a pixel electrode and a common electrode for applying an electric field to liquid crystal molecules. The aperture ratio can be improved because light from the electrode portion is also transmitted, and as a result, the transmittance of the liquid crystal display device can be improved.

[0008]

As described above, in an IPS type liquid crystal display device in which light is switched by rotating liquid crystal molecules in a plane substantially parallel to a substrate, afterimages and image sticking are reduced. Therefore, an alignment film having a high elastic modulus is required. In order to increase the elastic modulus of the alignment film, it is desirable that the polymer constituting the alignment film has a rigid and highly linear molecular structure. However, such a high-modulus alignment film generally has a drawback that its surface is brittle, and in the rubbing step for aligning the liquid crystal molecules (the step of rubbing the alignment film surface with a rubbing cloth), the alignment film surface in the pixel is damaged. Causes scratches and debris. These scratches and debris in the pixel disturb the initial alignment of the liquid crystal molecules, causing a significant reduction in display characteristics as a liquid crystal display device, such as a decrease in black level and a decrease in contrast. Therefore, in order to reduce the afterimage and image sticking, and at the same time to improve the black level and the contrast, an alignment film having a high elastic modulus and rubbing resistance (which does not generate rubbing scratches or rubbing scraps) is required. Become.

An object of the present invention is to use a high-modulus alignment film having rubbing resistance, reduce afterimages and image sticking, and provide a high-quality, high-transmissivity liquid crystal display without black level reduction or contrast reduction. It is to provide a device.

[0010]

According to one embodiment of the present application, at least one of a pair of transparent substrates, a liquid crystal alignment control layer formed on opposing surfaces of the pair of substrates, The liquid crystal is disposed between the substrates so as to be in contact with the control layer, and includes a pixel electrode, a common electrode, and an active element formed on one of the pair of substrates, and applies a voltage to the pixel electrode and the common electrode. The liquid crystal display device performs display by controlling the alignment of the liquid crystal by using a liquid crystal alignment control layer comprising a diamine composed of one or two cyclic structures and a tetralayer composed of one or two cyclic structures. And a polymer material having at least one alkyl group bonded to the cyclic structure of at least one of the diamine and the tetracarboxylic acid.

One of the features of this embodiment is that the alkyl group has 2 or less carbon atoms.

In the above structure, the elastic modulus of the polymer material constituting the liquid crystal alignment control layer is 3 gigapascal (GP).
a) The above is one of the features.

Further, in the above embodiment, the diamine is
One of the features is that it is a diamine represented by Chemical Formula 1 or Chemical Formula 2.

[0014]

[R1 to R12 represent a hydrogen atom, a halogen atom or an alkyl group, the alkyl group being unsubstituted or mono- or poly-substituted by halogen, especially F or Cl; I do. X is a single bond or —O—, —S—, —CO—, —C (CH ₃ ) ₂ —,
—SO ₂ —. Further, in the above embodiment, the tetracarboxylic acid is
It is a tetracarboxylic acid represented by Chemical Formula 3 or Chemical Formula 4.

[0016]

[R13 to R20 represent a hydrogen atom, a halogen atom or an alkyl group, which alkyl group is unsubstituted or mono- or polysubstituted with halogen, especially F or Cl. I do. Further, X represents a single bond or a, -O -, - S -, - CO -, - CH 2 -, - C
Represents any of (CH ₃ ) ₂ — and —SO ₂ —. According to such an embodiment, a high-modulus polyimide alignment film having rubbing resistance (without generating rubbing scratches or rubbing debris) can be provided, and as a result, there is no afterimage or image sticking, and there is no black level reduction or contrast reduction. A high-quality liquid crystal display device can be provided.

[0018]

As described above, the afterimage and image sticking phenomenon peculiar to the IPS method due to the elastic deformation of the alignment film surface without depending on the residual charge can be achieved by using the alignment control film having a high elastic modulus. Can be reduced. In order to increase the elastic modulus of the orientation control film, it is desirable that the molecular structure of the polymer constituting the orientation control film is rigid and rich in linearity. In general, a polyimide alignment film is used as a liquid crystal alignment control film in a liquid crystal display device because of the alignment of liquid crystal and the stability of a manufacturing process. The general synthetic route of polyimide alignment film is shown in Chemical Formula 1.
6 is shown.

The polyimide alignment film is formed by applying a polyamic acid synthesized from a diamine and a tetracarboxylic acid onto a substrate by using a printing machine or a spinner, and firing this at a high temperature. The term "polyimide alignment film" used herein does not mean that all the amic acid sites of the polyamic acid are imidized, but also includes those in which some amic acid sites remain.

First, the correlation between the elastic modulus of the alignment film and the afterimage level of the liquid crystal display device was examined using two types of liquid crystal display devices having different electrode configurations. The electrode configuration of the pixel portion of the liquid crystal display device used for the study is shown in FIGS. 1, 2, 3 and 4.

The liquid crystal display device according to the first embodiment is shown in FIGS.
As shown in FIG. The liquid crystal display device is of the IPS type, in which a pixel electrode for generating an electric field applied to liquid crystal molecules and a common electrode are comb-shaped, and are metal electrodes. 1 and 2 are a cross-sectional view of a pixel portion and a plan view showing an electrode structure. FIG. 1 is a cross-sectional view taken along the line CC ′ in FIG.
(B) and (c) are AA ′ and B in FIG.
It is sectional drawing which followed the -B 'line. Each pixel includes a thin film transistor (TFT) 15, a pixel electrode 5, and a common electrode 3. A voltage is applied between the pixel electrode and the common electrode, and the liquid crystal is driven by an electric field 13 generated thereby. The metal electrode material is not particularly limited as long as it is a metal material having low electric resistance, and may be chromium, aluminum, copper, or the like. In a liquid crystal display device in which such an electrode is made of a metal material, there is a problem that light is not transmitted through the electrode portion and the transmittance and the aperture ratio are reduced. For this reason, the electrode spacing is designed to be relatively wide, for example, the pixel electrode and the common electrode are arranged so that the electrode spacing is at least twice the thickness of the liquid crystal layer, and the aperture ratio is secured. From the study of the present inventors, it has been found that it is desirable that the elastic modulus of the alignment film is at least 3 gigapascal (GPa) in order for the afterimage level of the liquid crystal display device to reach a level with no problem in display characteristics.

The elastic modulus of the alignment film referred to here is the elastic modulus of the bulk of the alignment film. As described above, the afterimage / image sticking phenomenon is due to the elastic deformation of the alignment film surface. Strictly speaking, the surface elastic modulus should be discussed as the alignment film elastic modulus. However, the surface elastic modulus is a physical property value that largely reflects the bulk elastic modulus, and from the study of the present inventor, there is also a correlation between the bulk elastic modulus of the alignment film and the level of image sticking and image sticking. It is known that the higher the ratio, the more the afterimage and image sticking can be reduced.

In the above-mentioned liquid crystal display device, since a metal is used as an electrode material, a large problem is that the aperture ratio and the transmittance are low. To solve such a problem, Japanese Patent Laid-Open No.
No. 73101 proposes using a transparent conductive film as an electrode material. By using the transparent conductive film, light is transmitted through the electrode portion, and as a result, a high aperture ratio and a high transmittance can be achieved. There is another advantage of using a transparent conductive film. That is, the distance between the pixel electrode and the common electrode can be reduced without lowering the aperture ratio. By reducing the distance between the electrodes, the intensity of the electric field applied to the liquid crystal increases, and as a result, low-voltage driving and high-speed response of the liquid crystal become possible. In addition, the manufacturing process of the liquid crystal display device is simplified,
Considering an improvement in productivity, an IPS type liquid crystal display device in which one electrode is overlapped with the other electrode over substantially the entire area at the pixel opening to facilitate alignment between the pixel electrode and the common electrode is also considered. It is possible.

Therefore, the IPS type liquid crystal display device according to the second embodiment shown in FIGS. 3 and 4 was studied. A comb-shaped pixel electrode for generating an electric field to be applied to the liquid crystal molecules and a common electrode covering almost the entire pixel portion, and at least one or both of these electrodes are formed of a transparent conductive film. ITO or IZ with good processing accuracy as transparent conductive film
O is desirable. FIG. 3 is a cross-sectional view taken along the line CC ′ in FIG. FIGS. 4 (b) and 4 (c) respectively show FIG.
It is sectional drawing in alignment with the AA 'and BB' line in (a). Each pixel includes a thin film transistor (TFT) 115, a comb-shaped pixel electrode 105, and a common electrode 103 that substantially covers the entire pixel portion via an insulating film. Comb-shaped pixel electrodes are designed for low-voltage driving and high-speed response.
The electrode width and the electrode interval are extremely narrow as compared with the pixel electrodes in the liquid crystal display device according to the first embodiment. Also,
The lower common electrode does not need to be patterned in a comb shape, and the production efficiency is high since there is a margin for alignment with the upper comb-shaped pixel electrode. A voltage is applied between the pixel electrode and the common electrode, and an electric field 113 generated by the voltage is applied.
Drives the liquid crystal. With such a configuration, the electrode interval between the pixel electrode and the common electrode is substantially equal to the thickness of the insulating film interposed between the electrodes. As a result, the intensity of the electric field applied to the liquid crystal is extremely high, and low-voltage driving and high-speed response are possible.

According to the study of the present inventor, in such a liquid crystal display device, the elasticity of the alignment film must be at least 5 gigapascal (GPa) or more in order for the afterimage level to reach a level that does not cause a problem in display characteristics. Turned out to be desirable. It is considered that the need for an alignment film having a higher elastic modulus than that of the liquid crystal display device according to the first embodiment is due to the electric field concentration near the electrode edge.

In the liquid crystal display device of the second embodiment, the electrode interval is extremely narrow, and the electrode interval is substantially equal to the thickness of the insulating film interposed between the pixel electrode and the common electrode. When the electrode interval is extremely narrow as described above, electric field concentration occurs near the electrode edge, and the rotation angle of liquid crystal molecules in that region becomes larger than the average rotation angle of the entire liquid crystal layer. It is considered that the rotational torque increases. This increase in the rotational torque increases the amount of elastic deformation of the alignment film surface near the electrode edge, and consequently deteriorates the afterimage level. Therefore, as in the liquid crystal display device of the present embodiment, when the narrowest distance between the pixel electrode and the common electrode for applying an electric field to the liquid crystal is smaller than the thickness of the liquid crystal layer, the liquid crystal in the first embodiment is not used. An alignment film having less elastic deformation of the alignment film than the display device, that is, an alignment film having a large elastic modulus is required.

In a liquid crystal display device having such an electrode structure, it is known that high transmittance can be realized by using a liquid crystal having a negative dielectric anisotropy (Δε <0). When a liquid crystal having such a negative dielectric anisotropy is used, the rubbing angle θ (minimum angle between the rubbing direction and the long axis direction of the comb electrode) is 45 ° <θ <.
90 °, and preferably θ = about 75 ° in consideration of the actual transmittance, drive voltage, and the like. On the other hand, when a liquid crystal having a positive dielectric anisotropy is used, the rubbing angle θ is 0 °.
<[Theta] <40 [deg.], And it is preferable that [theta] = about 15 [deg.] In consideration of the transmittance and the driving voltage. At this time, when liquid crystal having negative dielectric anisotropy is used, rubbing bristle is less likely to hit the electrode edge portion due to the electrode step than when liquid crystal having positive dielectric anisotropy is used. The area, that is, the area where the rubbing is weak and the liquid crystal regulating force of the alignment film is weak is widened. In such a region, when an electric field is applied, the rotation angle of the liquid crystal molecules increases, and the effective torque increases. As a result, the afterimage level deteriorates.
Therefore, in a liquid crystal display device having such a negative dielectric anisotropy and having a narrow electrode spacing, an alignment film having a higher elastic modulus is required to reduce the afterimage level.

However, as confirmed by the present inventors' studies, in general, such an alignment film having a high modulus of elasticity, particularly, an alignment film of 5 gigapascal (GPa) or more in the second embodiment, is rubbed. Not resistant. That is, in the rubbing step for aligning the liquid crystal (the step of rubbing the surface of the alignment film with a cloth or the like), rubbing scratches and rubbing debris are generated due to abrasion of the film surface. This tendency increases as the elastic modulus of the alignment film increases. Further, in the liquid crystal display device according to the second embodiment, since the electrode width and the interval of the upper comb-shaped pixel electrode are extremely narrow, unevenness in the pixel portion increases. The structure having many steps easily causes rubbing scratches and rubbing debris. These rubbing scratches and rubbing debris disturb the initial alignment of liquid crystal molecules, and as a result, lower the black level and lower the contrast, thereby deteriorating the display characteristics of the liquid crystal display device. Therefore, in order to achieve both the afterimage characteristics and the rubbing resistance, it is necessary to develop an alignment film having a high elastic modulus and not causing abrasion of the film surface during the rubbing step.

For the above purpose, a polyimide alignment film is synthesized using a rigid and highly linear diamine and tetracarboxylic acid, and the modulus of elasticity of each polyimide alignment film, rubbing scratches at the time of rubbing, and rubbing scrap generation. It was investigated. The rigid and highly linear diamine used had a structure represented by (Chemical Formula 1) and (Chemical Formula 2).

[0030]

[R1 to R12 represent a hydrogen atom, a halogen atom or an alkyl group, the alkyl group being unsubstituted or mono- or polysubstituted with halogen, especially F or Cl. I do. X is a single bond or —O—, —S—, —CO—, —C (CH ₃ ) ₂ —,
—SO ₂ —. In addition, a rigid and highly linear tetracarboxylic acid having a structure represented by (Chemical Formula 3) to (Chemical Formula 5) was used.

[0032]

[R13 to R20 represent a hydrogen atom, a halogen atom or an alkyl group, the alkyl group being unsubstituted or mono- or polysubstituted with halogen, especially F or Cl. I do. Further, X represents a single bond or a, -O -, - S -, - CO -, - CH 2 -, - C
Represents any of (CH ₃ ) ₂ — and —SO ₂ —. ]

Through these studies, we have found several polyimide alignment films having both high elastic modulus and rubbing resistance. And they found one common feature in their molecular structures. That is, it is synthesized from a diamine composed of one or two cyclic structures and a tetracarboxylic acid composed of one or two cyclic structures, and further, at least one of these cyclic structures has an alkyl group. The polyimide alignment film into which is introduced has a high elastic modulus and a rubbing resistance. This alkyl group may be present in one or more of either diamine and tetracarboxylic acid, or may be present in both. Furthermore, a plurality may be included in the same annular structure portion. In addition, the cyclic structure portion refers to an aromatic ring or an alicyclic structure, and does not include, for example, a ring structure generated by dehydrating tetracarboxylic acid. That is, in the case of the two kinds of tetracarboxylic anhydrides represented by (Chemical formula 11) or (Chemical formula 5), there is one cyclic structure portion. In the case of the tetracarboxylic anhydride represented by (Chemical formula 12), there are two cyclic structures.

[0035]

[0036]

The polyimide alignment film comprises one or more of the diamines represented by Formula 1 or Formula 2 and the tetracarboxylic acid represented by Formula 3 or Formula 4 It may be synthesized from one or more kinds of tetracarboxylic acids. Also, (Chemical formula 5)
May be synthesized from a tetracarboxylic acid represented by the formula and one or more diamines among the diamines represented by the (chemical formula 1) or (chemical formula 2). Furthermore, (Chemical formula 5)
And at least one of tetracarboxylic acids represented by (Chemical Formula 3) or (Chemical Formula 4) and a diamine represented by (Chemical Formula 1) or (Chemical Formula 2) It may be synthesized from one or more diamines.

Further, it has been found from the investigation that the alkyl group introduced into the cyclic structure preferably has 2 or less carbon atoms. When the number of carbon atoms in the side chain alkyl group introduced into the cyclic structure is 3 or more, at least the following two problems occur. In an alkyl group having 3 or more carbon atoms, the carbon chain has flexibility and lowers the elastic modulus of the polyimide alignment film. The decrease in the elastic modulus deteriorates the afterimage characteristics. This tendency increases as the carbon number increases. When an alkyl group having 3 or more carbon atoms is present as a side chain, a pretilt angle of a liquid crystal molecule is generated. In a method of switching light by rotating liquid crystal molecules on a plane substantially parallel to the substrate surface such as the IPS method, a large pretilt angle causes a viewing angle dependence such as a color tone.

Hereinafter, embodiments will be described in detail with reference to the drawings of the present invention, but the present invention is not limited to these embodiments. Embodiment 1 FIG. 1 is a schematic view of a liquid crystal display device according to this embodiment.
And FIG. FIG. 5 shows an equivalent circuit of the display matrix unit and its peripheral circuits. Liquid crystal display device is IPS
In this method, a voltage is applied between electrodes formed on the same substrate, and liquid crystal molecules are driven by an electric field substantially parallel to the substrate surface generated by the application of voltage, thereby controlling an optical state and controlling display.

The liquid crystal display device used was a transparent glass substrate 1 or 2 having a display portion having a diagonal size of 14.1 inches, a thickness of 0.7 mm, and a polished surface. On the glass substrate 1, signal electrodes 6 and scanning electrodes 16 were formed as shown in FIG. Each pixel has a thin film transistor (TFT) 15,
It comprises a comb-shaped pixel electrode 5 and a comb-shaped common electrode 3. A voltage is applied between the pixel electrode and the common electrode, and the liquid crystal is driven by an electric field 13 generated thereby. The pixel electrode is connected to a thin film transistor (TFT), and the common electrode is integrated with a common voltage signal line. It should be noted that chromium is used as the electrode material, and the electrode is a long and thin electrode configured in a comb shape. The electrode width and the electrode interval are 10 μm and 15 μm, respectively. The electrode material is not particularly limited as long as it is a metal material having low electric resistance, and may be aluminum, copper, or the like. Further, a transparent conductive film such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium germanium oxide (IGO) with high processing accuracy may be used.

On the other hand, a structure is provided in which a three-color RGB color filter 11 and a black matrix 12 are provided on the opposing glass substrate 2. A color filter protective film 10 for flattening was formed on the color filter and the black matrix. Epoxy resin was used as the color filter protective film. Further, columnar spacers were formed on a black matrix, which is a light shielding portion of a glass substrate, to uniformly control the thickness of the liquid crystal layer in the display area. In FIG. 1, the columnar spacer is omitted.

Next, a polyimide alignment film 8 necessary for aligning liquid crystal molecules was formed on the surfaces of the glass substrates 1 and 2. Generally, a polyimide film is obtained by reacting a diamine and a tetracarboxylic acid monomer in an appropriate solvent to synthesize a polyamic acid, which is a precursor of polyimide, and baking it at a high temperature. The synthesis of the polyimide alignment film used in this example will be described. DMAP represented by (chemical formula 13) was used as a diamine, and PMDA represented by (chemical formula 11) was used as a tetracarboxylic acid.

[0043]

First, in order to remove the water adsorbed on each monomer, it was vacuum dried in a desiccator (diamine: 40
° C / 8h, tetracarboxylic acid: 130 ° C / 8h).
1.0 mol% of diamine DMAP was dissolved in N-methyl-2-pyrrolidone, and after confirming that diamine DMAP was sufficiently dissolved, tetracarboxylic acid PMDA 1.
0 mol% was added and reacted at 25 ° C. for 60 hours to synthesize a polyamic acid varnish. In this embodiment, the diamine and the tetracarboxylic acid are reacted at a ratio of 1: 1 (mol%). However, in consideration of the stability of the synthetic polymer, for example, the diamine is closed so that the polymer terminal group is closed with the tetracarboxylic acid. The molar percentage of tetracarboxylic acid may be slightly increased. As a result, the physical property values such as the elastic modulus of the synthetic polyimide film do not significantly change. In this example, N-methyl-2-pyrrolidone was used as the solvent.
Other than this, for example, polar butyl cellosolve, butyl lactone, or a mixed solution thereof may be used, but the present invention is not limited thereto. The polyamic acid varnish synthesized here was diluted to a solid concentration of 2%, and applied to a glass substrate with a printing machine. After calcination to remove the solvent, calcination was performed at 240 ° C. for 15 minutes. The thickness of the obtained polyimide alignment film was about 100 nm.

Next, an alignment treatment for aligning the liquid crystal molecules was performed. The alignment treatment was performed by rubbing the surface of the polyimide alignment film formed on both glass substrates. A rubbing machine (FS-55R type made by Fujioka) was used for the rubbing treatment, and a buff cloth made of rayon was used for the rubbing roll (100φ). The rubbing conditions were a roll rotation speed of 950 rpm, a substrate feed speed of 30 mm / sec, and a pushing amount of 0.4 mm. Here, the pushing amount is the amount by which the rubbing roll is pushed from the surface of the alignment film toward the glass substrate. The larger the pushing amount, the deeper the rubbing roll was pushed. The rubbing direction of the rubbing cloth from the surface of the alignment film to the glass substrate was set at 15 ° with respect to the long axis of the comb electrode. After the rubbing step, when both substrates were observed with a microscope, no rubbing scratches or rubbing chips were found in the display area.

A sealing material (thermosetting resin) was applied to the periphery of the display area of the glass substrate 1 and the opposing glass substrates 2 were overlaid, and then pressurized while heating to bond and fix both substrates. The gap between glass substrates (liquid crystal layer thickness) is 4.0μ
m. Thereafter, liquid crystal was injected from the sealing port, and the sealing port was sealed with a photocurable resin. In this embodiment, a liquid crystal having a positive dielectric anisotropy is used. A polarizing plate 14 was attached to both surfaces of the glass substrates 1 and 2 to complete a liquid crystal panel. The polarizing plate was attached so that the liquid crystal display device had normally closed characteristics (black display at low voltage, white display at high voltage). Further, as shown in FIG. 5, a scanning electrode drive circuit 20, a signal electrode drive circuit 21, a power supply circuit and a control circuit 23 are connected to the glass substrate of the liquid crystal panel to supply a scanning signal voltage, a video signal voltage, and a timing signal. , Active matrix drive. Thereafter, the liquid crystal display panel 29 is provided with the shield case 30, the diffusion plate 31, the light guide 32,
The liquid crystal display device 37 was assembled by combining the reflection plate 33, the backlight 34, the lower case 35, and the inverter circuit board 36.

When the display area of the liquid crystal display device thus assembled was observed with a microscope, no defective liquid crystal alignment due to rubbing scratches or rubbing debris was observed, and basic display characteristics such as black level and contrast were good. .
The contrast ratio (the value obtained by dividing the maximum transmittance by the minimum transmittance) was 300.

In order to quantitatively evaluate the afterimage and image printing, the evaluation was performed using an oscilloscope combined with a photodiode. First, a window pattern is displayed on the screen at the maximum brightness for 30 minutes, and thereafter, the entire display screen is switched so that the afterimage is most conspicuous, in this case, the brightness is 10% of the maximum brightness. The magnitude ΔB of the luminance variation in the luminance B in the peripheral halftone portion
/ B (10%) was evaluated as an afterimage intensity. As a display characteristic of the liquid crystal display device, a level at which there is no problem of image sticking and image sticking is determined to have an image sticking intensity of 3% or less. As a result of the evaluation, in the liquid crystal display device of this embodiment, the afterimage intensity is 1.
A result of 0% was obtained.

In order to quantitatively measure the brittleness of the alignment film surface, it was evaluated by a scratch test. In the scratch test, a diamond needle vibrated at a frequency of 30 Hz and an amplitude of 80 μm is pressed against the alignment film with a known force, and by sweeping the magnitude of the force, the pressing force at which the film surface starts to be scraped is measured, and the rubbing resistance of the film surface is measured. Is a method for evaluating quantitatively. The pressing force at which the film surface starts to be scraped is called a critical load value. The smaller the critical load, the more easily the surface of the film is damaged, and the larger the value of the critical load, the less the surface is damaged. In this evaluation, a polyamic acid synthesized on a glass substrate was applied by a spinner and then baked at 240 ° C. for 15 minutes. The thickness was about 100 nm. The critical load value was about 45 nanonewtons (nN).

Next, a polyimide film was formed on the polyimide alignment film, and the bulk modulus of the polyimide was measured by a tensile test of the film. As a result, 10
Approximately 14 gigapascal (GP
a) was obtained.

According to the present example, a polyimide alignment film having a high critical load value while having a high elastic modulus, that is, a scratch-resistant polyimide film was obtained. As a result, it was possible to obtain a high-quality liquid crystal display device which does not generate rubbing scratches or rubbing debris and has no afterimage or image sticking. (Example 2) A liquid crystal display device similar to that of Example 1 was assembled except for the alignment film used. The polyimide alignment film synthesized in this example will be described. As a diamine (chemical formula 14)
And PMDA represented by (Formula 11) was used as tetracarboxylic acid.

[0052]

Vacuum drying in a desiccator to remove water adsorbed on each monomer (diamine: 40 ° C./8
h, tetracarboxylic acid: 130 ° C./8 h). First,
1.0 mol% of diamine TMPPD was dissolved in N-methyl-2-pyrrolidone, and after confirming that diamine TMPPD was sufficiently dissolved, tetracarboxylic acid PMDA 1.
0 mol% was added and reacted at 25 ° C. for 60 hours to synthesize a polyamic acid varnish. In this example, the diamine and the tetracarboxylic acid are reacted at a ratio of 1: 1 (mol%). However, in consideration of the stability of the synthetic polymer, for example, the polymer terminal group is closed with the tetracarboxylic acid. The molar percentage of the tetracarboxylic acid may be slightly higher than the diamine. As a result, the physical property values such as the elastic modulus of the synthetic polyimide film do not significantly change. In this embodiment, N-methyl-2-pyrrolidone is used as the solvent. However, other than this, for example, polar butylcellosolve, butyllactone, or a mixed solution thereof may be used. It is not something to be done. The polyamic acid varnish synthesized here was diluted to a solid concentration of 2%, and applied to a glass substrate with a printing machine. After calcination to remove the solvent, calcination was performed at 240 ° C. for 15 minutes. The thickness of the obtained polyimide alignment film was about 100 nm.

When the display area of the liquid crystal display device obtained in this example was observed with a microscope, no defective liquid crystal alignment due to rubbing scratches or rubbing debris was observed, and the basic display characteristics such as black level and contrast were good. Was. In addition,
The contrast ratio was 300.

The afterimage intensity was measured in the same manner as in Example 1. As a display characteristic of the liquid crystal display device, a level at which there is no problem of image sticking and image sticking is determined to have an image sticking intensity of 3% or less.
As a result of the evaluation, in the present liquid crystal display device, the afterimage intensity was 0.3.
A result of 5% was obtained.

Evaluation was made by a scratch test in order to quantitatively measure the brittleness of the alignment film surface. In this evaluation, a polyamic acid synthesized on a glass substrate was applied by a spinner and then baked at 240 ° C. for 15 minutes. The thickness was about 100 nm. The critical load value was about 40 nanonewtons (nN).

Next, the modulus of elasticity of the polyimide alignment film was measured. As a result, the bulk elastic modulus of the polyimide alignment film at 10 Hz was measured.
Pa).

According to the present example, a polyimide alignment film having a high critical load value while having a high elastic modulus, that is, a scratch-resistant polyimide film could be obtained. As a result, it was possible to obtain a high-quality liquid crystal display device which does not generate rubbing scratches or rubbing debris and has no afterimage or image sticking. (Embodiment 3) A schematic diagram of a liquid crystal display device in this embodiment is shown in FIG.
And FIG. FIG. 5 shows an equivalent circuit of the display matrix unit and its peripheral circuits. A voltage is applied between the electrodes formed on the same substrate, and the liquid crystal molecules are driven by an electric field generated by the voltage, thereby controlling an optical state and controlling a display. Since the distance between the pixel electrode 105 and the common electrode 103 is much smaller than that of the liquid crystal display devices according to the first and second embodiments, the electric field intensity applied to the liquid crystal is strong, thereby enabling low-voltage driving and high-speed response.

As the liquid crystal display element, transparent glass substrates 101 and 102 having a display section of 14.1 inches in diagonal size, a thickness of 0.7 mm and a polished surface were used. Glass substrate 1
As shown in FIG. 5, signal electrodes 6 and scanning electrodes 16 were formed on 01. Each pixel is a thin film transistor (T
FT) 15, the pixel electrode 105, and the common electrode 103. The pixel electrode 105 is connected to the common electrode 10 via an insulating film.
3 are arranged so as to overlap. In such a liquid crystal display device, there is no need to pattern the common electrode under the insulating film, and since there is a margin for alignment with the comb-shaped pixel electrode on the insulating film, the manufacturing process can be simplified and the productivity can be improved. It is possible. A voltage is applied between the pixel electrode and the common electrode, and the liquid crystal is driven by an electric field 113 generated by the voltage. Since the distance between the electrodes is very narrow as compared with the liquid crystal display devices of the first and second embodiments, the electric field intensity is strong, and low-voltage driving and high-speed response are possible. The pixel electrode is connected to a thin film transistor (TFT), and the common electrode is integrated with a common voltage signal line. Note that the pixel electrode is a transparent electrode made of indium tin oxide (ITO), is formed in a comb shape, and has a long and thin structure. The electrode width and the electrode interval are both 4 μm. Alternatively, indium zinc oxide (IZO) or the like may be used as the electrode material.

On the other hand, on the opposite glass substrate 101, a structure was provided in which a three-color RGB color filter 111 and a black matrix 112 in a stripe shape were provided. A color filter protective film 110 for flattening was formed on the color filter and the black matrix. Epoxy resin was used as the color filter protective film. Further, the glass substrate 10
A columnar spacer was formed on the black matrix, which is a light shielding portion, to uniformly control the thickness of the liquid crystal layer in the display region. In FIG. 3, the columnar spacer is omitted.

Next, a polyimide alignment film 1 necessary for aligning liquid crystal molecules on the surfaces of the two glass substrates 101 and 102.
08 was formed. The polyimide alignment film used in this example is the same as that in Example 1. The firing was performed at 240 ° C. for 15 minutes, and the thickness of the obtained polyimide alignment film was about 100 nm.

Next, an alignment treatment for aligning the liquid crystal molecules was performed. The alignment treatment was performed by rubbing the surface of the polyimide alignment film formed on both glass substrates. A rubbing machine (FS-55R type made by Fujioka) was used for the rubbing treatment, and a buff cloth made of rayon was used for the rubbing roll (100φ). The rubbing conditions were a roll rotation speed of 950 rpm, a substrate feed speed of 30 mm / sec, and a pushing amount of 0.4 mm. Here, the pushing amount is the amount by which the rubbing roll is pushed from the surface of the alignment film toward the glass substrate. The rubbing direction was set at 75 ° with respect to the major axis of the ITO comb electrode. Compared to the liquid crystal display device of the first embodiment, since the electrode spacing and electrode width are narrow, the surface of the substrate is very uneven due to the narrowness, and rubbing scratches and rubbing debris are likely to be generated. Upon observation, no rubbing scratches or rubbing debris were found in the display area.

A sealing material (thermosetting resin) is applied to the periphery of the display area of the glass substrate 101, and the opposite glass substrate 102
Then, pressure was applied while heating, and both substrates were bonded and fixed. The gap between the glass substrates (liquid crystal layer thickness) is 4.
It was set to 0 μm. Thereafter, liquid crystal was injected from the sealing port, and the sealing port was sealed with a photocurable resin. In this embodiment, a liquid crystal having a negative dielectric anisotropy is used. Glass substrates 101, 10
The liquid crystal display device was completed by attaching the polarizing plate 114 to both sides of the second liquid crystal display. The polarizing plate was attached so as to have normally closed characteristics (black display at low voltage, white display at high voltage).
Further, a scanning electrode drive circuit 20, a signal electrode drive circuit 21, a power supply circuit and a control circuit 23 are connected to the glass substrate as shown in FIG.
A video signal voltage and a timing signal were supplied, and active matrix driving was performed. Then, the liquid crystal display panel 29 shown in FIG.
Case 30, diffusion plate 31, light guide 3 shown in FIG.
2, reflector 33, backlight 34, lower case 35,
The liquid crystal display device 37 was assembled by combining the inverter circuit board 36.

When the inside of the display area of the liquid crystal display device assembled in this manner was observed with a microscope, no defective liquid crystal alignment due to rubbing scratches or rubbing debris was observed, and basic display characteristics such as black level and contrast were also good. .
The contrast ratio was 500.

In order to quantitatively evaluate the afterimage and image printing, the evaluation was performed using an oscilloscope combined with a photodiode. First, a window pattern is displayed on the screen at the maximum brightness for 30 minutes, and thereafter, the entire display screen is switched so that the afterimage is most conspicuous, in this case, the brightness is 10% of the maximum brightness. The magnitude ΔB of the luminance variation in the luminance B in the peripheral halftone portion
/ B (10%) was evaluated as an afterimage intensity. However, as a display characteristic of the liquid crystal display device, a level where image sticking and image sticking are not a problem has an after image intensity of 3% or less. As a result of the evaluation, in the present liquid crystal display device, a result having an afterimage intensity of 2.0% was obtained.

According to the present example, a polyimide alignment film having a large critical load value while having a high elastic modulus, that is, a scratch-resistant polyimide film could be obtained. As a result, it was possible to obtain a high-quality liquid crystal display device which does not generate rubbing scratches or rubbing debris and has no afterimage or image sticking. (Example 4) A liquid crystal display device similar to that of Example 3 was assembled except for the alignment film used. Further, the polyimide alignment film used in this example was synthesized in Example 2. The thickness of the obtained polyimide alignment film was about 100 nm.

When the inside of the display area of the liquid crystal display device obtained in this embodiment was observed with a microscope, the width and interval of the comb-tooth electrodes were extremely narrow and the unevenness of the substrate surface was extremely severe as compared with the second embodiment. Nevertheless, poor liquid crystal alignment due to rubbing scratches and rubbing debris was not observed, and the basic display characteristics such as black level and contrast were good. The contrast ratio was 500.

Further, the afterimage intensity was measured in the same manner as in Example 1. As a display characteristic of the liquid crystal display device, a level at which there is no problem of image sticking and image sticking is determined to have an image sticking intensity of 3% or less.
As a result of the evaluation, in the present liquid crystal display device, the afterimage intensity was 1.
A result of 0% was obtained.

According to the present example, a polyimide alignment film having a high critical load value while having a high elastic modulus, that is, a scratch-resistant polyimide film could be obtained. As a result, it was possible to obtain a high-quality liquid crystal display device which does not generate rubbing scratches or rubbing debris and has no afterimage or image sticking. (Example 5) A liquid crystal display device similar to that of Example 3 was assembled except for the alignment film used. The polyimide alignment film synthesized in this example will be described. As a diamine (chemical formula 13)
CBDA represented by (Chemical Formula 5) was used as DMAP represented by the following formula and tetracarboxylic acid.

[0070]

Vacuum drying in a desiccator to remove water adsorbed on each monomer (diamine: 40 ° C./8
h, tetracarboxylic acid: 130 ° C./8 h). First,
1.0 mol% of diamine DMAP was dissolved in N-methyl-2-pyrrolidone, and after confirming that diamine DMAP was sufficiently dissolved, tetracarboxylic acid CBDA 1.
0 mol% was added and reacted at 25 ° C. for 60 hours to synthesize a polyamic acid varnish. In this example, the diamine and the tetracarboxylic acid are reacted at a ratio of 1: 1 (mol%). However, in consideration of the stability of the synthetic polymer, for example, the polymer terminal group is closed with the tetracarboxylic acid. The molar percentage of the tetracarboxylic acid may be slightly higher than the diamine. As a result, the physical property values such as the elastic modulus of the synthetic polyimide film do not significantly change. In this example, N-methyl-2-pyrrolidone was used as the solvent.
Other than this, for example, polar butyl cellosolve, butyl lactone, or a mixed solution thereof may be used, but the present invention is not limited thereto. The polyamic acid varnish synthesized here was diluted to a solid concentration of 5%, and applied to a glass substrate by a printing machine. After calcination to remove the solvent, calcination was performed at 240 ° C. for 15 minutes. The thickness of the obtained polyimide alignment film was about 100 nm.

When the display area of the liquid crystal display device obtained in this example was observed with a microscope, no defective liquid crystal alignment due to rubbing scratches or rubbing debris was observed, and the basic display characteristics such as black level and contrast were good. Was. In addition,
The contrast ratio was 500.

Further, the afterimage intensity was measured in the same manner as in Example 1. As a display characteristic of the liquid crystal display device, a level at which there is no problem of image sticking and image sticking is determined to have an image sticking intensity of 3% or less.
As a result of the evaluation, in the present liquid crystal display device, the afterimage intensity was 1.
A result of 5% was obtained.

In order to quantitatively measure the brittleness of the alignment film surface, evaluation was made by a scratch test. In this evaluation, a polyamic acid synthesized on a glass substrate was applied by a spinner and then baked at 240 ° C. for 15 minutes. The thickness was about 100 nm. The critical load value was about 45 nanonewtons (nN).

Next, the modulus of elasticity of the polyimide alignment film was measured. As a result, the bulk elastic modulus of the polyimide alignment film at 10 Hz was measured.
Pa). According to this example, a polyimide alignment film having a large critical load value while having a high elastic modulus, that is, a scratch-resistant polyimide film could be obtained. As a result,
Does not generate rubbing scratches or rubbing debris.
A high quality liquid crystal display device without image sticking was obtained. (Example 6) A liquid crystal display device similar to that of Example 3 was assembled except for the alignment film used. The polyimide alignment film synthesized in this example will be described. As a diamine (chemical formula 14)
And PMDA represented by (Chemical Formula 11) and SBPDA represented by (Chemical Formula 12) were used as tetracarboxylic acids.

[0076]

[0077]

Vacuum drying in a desiccator to remove water adsorbed on each monomer (diamine: 40 ° C./8
h, tetracarboxylic acid: 130 ° C./8 h). First,
1.0 mol% of diamine TMPPD was dissolved in N-methyl-2-pyrrolidone, and after confirming that the diamine TMPPD was sufficiently dissolved, 0.5 mol% of each of PMDA and SBPDA tetracarboxylic acid was added, and 6 at ℃
After reacting for 0 hour, a polyamic acid varnish was synthesized. In this example, the diamine and the tetracarboxylic acid were mixed at a ratio of 1: 1.
(Mol%), but in consideration of the stability of the synthetic polymer, for example, the mol% of tetracarboxylic acid may be slightly larger than that of diamine so that the polymer terminal group is closed with tetracarboxylic acid. . As a result, the physical property values such as the elastic modulus of the synthetic polyimide film do not significantly change. In this embodiment, N-methyl-2-pyrrolidone is used as the solvent. However, other than this, for example, polar butylcellosolve, butyllactone, or a mixed solution thereof may be used. It is not something to be done. The polyamic acid varnish synthesized here was diluted to a solid concentration of 5%, and applied to a glass substrate by a printing machine. After calcination to remove the solvent, 240 ° C / 15
The main firing was performed in minutes. The thickness of the obtained polyimide alignment film is 1
It was about 00 nm.

When the inside of the display area of the liquid crystal display device obtained in this example was observed with a microscope, no defective liquid crystal alignment due to rubbing scratches or rubbing debris was observed, and the basic display characteristics such as black level and contrast were good. Was. In addition,
The contrast ratio was 500.

The afterimage intensity was measured in the same manner as in Example 1. As a display characteristic of the liquid crystal display device, a level at which there is no problem of image sticking and image sticking is determined to have an image sticking intensity of 3% or less.
As a result of the evaluation, in the present liquid crystal display device, the afterimage intensity was 1.
A result of 0% was obtained.

Evaluation was made by a scratch test in order to quantitatively measure the brittleness of the alignment film surface. In this evaluation, a polyamic acid synthesized on a glass substrate was applied by a spinner and then baked at 240 ° C. for 15 minutes. The thickness was about 100 nm. The critical load value was about 45 nanonewtons (nN).

Next, the modulus of elasticity of the polyimide alignment film was measured. As a result, the bulk elastic modulus of the polyimide alignment film at 10 Hz was measured.
Pa).

According to this example, a polyimide alignment film having a large critical load value while having a high elastic modulus, that is, a scratch-resistant polyimide film could be obtained. As a result, it was possible to obtain a high-quality liquid crystal display device which does not generate rubbing scratches or rubbing debris and has no afterimage or image sticking. Comparative Example 1 A liquid crystal display device similar to that of Example 3 was assembled except for the alignment film used. The polyimide alignment film synthesized in this example will be described. As a diamine (chemical formula 15)
Represented by the formula:
PMDA shown in 1) was used.

[0084]

Vacuum drying in a desiccator to remove water adsorbed on each monomer (diamine: 40 ° C./8
h, tetracarboxylic acid: 130 ° C./8 h). First,
1.0 mol% of diamine AP was dissolved in N-methyl-2-pyrrolidone, and after confirming that the diamine AP was sufficiently dissolved, 1.0 mol% of tetracarboxylic acid PMDA was dissolved.
Was added and reacted at 25 ° C. for 60 hours to synthesize a polyamic acid varnish. The polyamic acid varnish synthesized here was diluted to a solid concentration of 6%, and applied on a glass substrate by a printing machine. After calcination to blow off the solvent,
The firing was performed in 15 minutes. The thickness of the obtained polyimide alignment film was about 100 nm.

When the inside of the display area of the liquid crystal display device obtained in this example was observed with a microscope, it was confirmed that a large amount of rubbing scratches and rubbing scraps were generated in the display area. In addition, poor initial alignment of the liquid crystal due to these scratches and debris was confirmed, and a liquid crystal display device having a low black level and low contrast and low display characteristics was obtained. The contrast ratio was 200.

Further, the afterimage intensity was measured in the same manner as in Example 1. As a display characteristic of the liquid crystal display device, a level at which there is no problem of image sticking and image sticking is determined to have an image sticking intensity of 3% or less.
As a result of the evaluation, in the present liquid crystal display device, the afterimage intensity was 2.
A result of 5% was obtained.

Evaluation was made by a scratch test to quantitatively measure the brittleness of the alignment film surface. In this evaluation, a polyamic acid synthesized on a glass substrate was applied by a spinner and then baked at 240 ° C. for 15 minutes. The thickness was about 100 nm. The critical load value was about 14 nanonewtons (nN).

Next, the bulk modulus of the polyimide alignment film was measured. As a result, a result that the bulk elastic modulus at 10 Hz was about 12 gigapascal (GPa) was obtained.

Since the polyimide alignment film obtained by the synthesis in this example has a high elastic modulus, elastic deformation on the alignment film surface is unlikely to occur, and the afterimage intensity achieves a level that does not cause any problem (3% or less). are doing. However, the film has a small critical load value and is easily shaved. Therefore, a large number of rubbing scratches and rubbing debris generated in the rubbing process are confirmed in the display area, which causes a decrease in black level and a decrease in contrast due to poor initial alignment of the liquid crystal, thereby deteriorating display characteristics as a liquid crystal display device. ing. Comparative Example 2 A liquid crystal display device similar to that of Example 3 was assembled except for the alignment film used. Although the specific structure of the polyimide alignment film used in this example is unknown, the bulk elastic modulus is about 3 gigapascal (GPa), and the critical load value by the scratch test is about 45 nanonewton (nN). is there. This polyimide alignment film was applied on a glass substrate by a printing machine in the same manner as in Example 3, and calcined in order to remove the solvent, and then calcined at 240 ° C. for 15 minutes. The thickness of the obtained polyimide alignment film was about 100 nm.

When the inside of the display area of the liquid crystal display device obtained in this example was observed with a microscope, it was confirmed that no rubbing scratches or rubbing chips were generated. In addition, a liquid crystal display device having good black level and high contrast was obtained. The contrast ratio was 500.

Further, the afterimage intensity was measured in the same manner as in Example 1. As a display characteristic of the liquid crystal display device, the level of no problem of image sticking and image sticking is considered to have an afterimage intensity of 3% or less. As a result of the evaluation, this liquid crystal display device has a result of 20% of the afterimage intensity. Was.

The polyimide alignment film used in the present example has a considerably large critical load value as determined by a scratch test, and is a film whose surface is not easily shaved. Therefore, rubbing scratches and rubbing debris do not occur in the rubbing step. However, since the elastic modulus is low, elastic deformation easily occurs on the surface of the alignment film, the afterimage intensity is extremely large, and the display characteristics of the liquid crystal display device are not good.

[0094]

By using an alignment control layer having a high elastic modulus and a strong rubbing resistance, a high-quality liquid crystal display device free from liquid crystal alignment defects due to rubbing scratches and rubbing debris and free from afterimages and image sticking phenomena. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a pixel region illustrating a configuration of a liquid crystal display device according to a first embodiment and a second embodiment.

FIG. 2 is a schematic plan view and cross-sectional view of a pixel region showing an electrode structure of a liquid crystal display device according to Embodiments 1 and 2.

FIG. 3 is a schematic cross-sectional view of a pixel region illustrating a configuration of a liquid crystal display device according to a third embodiment and a fourth embodiment.

FIG. 4 is a schematic plan and cross-sectional view of a pixel region showing an electrode structure of a liquid crystal display device according to a third embodiment and a fourth embodiment.

FIG. 5 is a diagram illustrating a system configuration for driving a liquid crystal display device.

FIG. 6 is an exploded perspective view of a liquid crystal display device.

[Description of References] 1, 2, 101, 102: glass substrate, 3, 103: common electrode (common electrode), 4, 7, 104, 107: insulating protective film, 5, 105: pixel electrode (source electrode), 6,1
06: signal electrode (drain electrode), 8, 108: alignment film, 9, 109: liquid crystal, 10, 110: color filter protective film, 11, 111: color filter, 12, 112
... black matrix (light shielding film), 13, 113 ... electric field, 14, 114 ... polarizing plate, 15, 115 ... thin film transistor (TFT), 16, 116 ... scanning electrode (gate electrode), 17, 117 ... capacitance element, 18, 118 ... Amorphous silicon, 20 ... Scan electrode drive circuit, 21 ... Signal electrode drive circuit, 22 ... Common electrode drive circuit, 23 ... Power supply circuit and control circuit, 29 ... Liquid crystal display panel, 30
... Shield case, 31 ... Diffusion plate, 32 ... Light guide plate, 33
... Reflector, 34 ... Backlight, 35 ... Lower case, 3
6 ... Inverter circuit board, 37 ... Liquid crystal display device.

Continued on the front page (72) Inventor Shinji Yamada 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. 2H090 HB08Y HB09Y JB02 KA05 LA01 MB01 4J043 PA04 QB15 QB26 QB31 RA34 SA52 SA54 SA55 TA42 TA43 TA44 TA47 TA48 UA121 UA122 UA131 UA632 UB021 UB022 UB121 UB122 UB151 UB152 UB281 UB282 UB301 UB302 VA041 VA092 ZA32 ZB23

Claims (23)

[Claims] 1. A pair of substrates, at least one of which is transparent, a liquid crystal alignment control layer formed on mutually facing surfaces of the pair of substrates, and a liquid crystal alignment control layer which is in contact with the liquid crystal alignment control layer. The liquid crystal arranged includes a pixel electrode, a common electrode, and an active element formed on one of the pair of substrates. The liquid crystal is oriented by applying a voltage between the pixel electrode and the common electrode. In a liquid crystal display device that performs display by controlling, the liquid crystal alignment control layer is synthesized from a diamine composed of one or two cyclic structures and a tetracarboxylic acid composed of one or two cyclic structures. A liquid crystal display device comprising a polymer material having at least one alkyl group bonded to the cyclic structure portion of at least one of the diamine and the tetracarboxylic acid. 2. The liquid crystal display device according to claim 1, wherein said alkyl group has 2 or less carbon atoms. 3. The liquid crystal display device according to claim 1, wherein an elastic modulus of the polymer material constituting the liquid crystal alignment control layer is 3 gigapascals (GPa) or more. 4. The diamine is represented by Formula 1 or 2
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a diamine represented by the following formula: [R1 to R12 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or -O
—, —S—, —CO—, —C (CH ₃ ) ₂ —, or —SO ₂ —. ] 5. The liquid crystal display device according to claim 1, wherein the tetracarboxylic acid is a tetracarboxylic acid represented by Chemical Formula 3 or Chemical Formula 4. . [R13 to R20 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted or mono- or polysubstituted with halogen, particularly F or Cl. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3) 2 -,
—SO ₂ —. ] 6. The polymer material according to claim 1, wherein
Wherein the compound is synthesized from one or more of the diamines represented by formula (1) and one or more of the tetracarboxylic acids of the tetracarboxylic acid represented by the formula (3) or (4). The liquid crystal display device according to claim 1. 7. The polymer material is synthesized from a tetracarboxylic acid represented by Chemical Formula 5 and one or more diamines represented by Chemical Formula 1 or Chemical Formula 2. The liquid crystal display device according to claim 1. [R1 to R12 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or -O
—, —S—, —CO—, —C (CH ₃ ) ₂ —, or —SO ₂ —. ] 8. The polymer material comprising a tetracarboxylic acid represented by the formula 5, one or more tetracarboxylic acids represented by the formula 3 or 4, and a diamine represented by the formula 1 or 2 The liquid crystal display device according to any one of claims 1 to 5, wherein the liquid crystal display device is synthesized using one or more diamines. [R13 to R20 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted or mono- or polysubstituted with halogen, particularly F or Cl. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3) 2 -,
—SO ₂ —. ] [R1 to R12 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or -O
—, —S—, —CO—, —C (CH ₃ ) ₂ —, or —SO ₂ —. ] 9. The liquid crystal display according to claim 1, wherein at least one of the pixel electrode and the common electrode is formed using a transparent conductive material. apparatus. 10. The transparent conductive material is indium tin oxide.
The liquid crystal display device according to claim 9, wherein the liquid crystal display device is (ITO), indium zinc oxide (IZO), or indium germanium oxide (IGO). 11. A pair of substrates, at least one of which is transparent;
A liquid crystal alignment control layer formed on surfaces of the pair of substrates facing each other, a liquid crystal disposed between the substrates so as to contact the liquid crystal alignment control layer, and one of the pair of substrates. A pixel electrode, a common electrode, and an active element.The distance between the pixel electrode and the common electrode is smaller than the thickness of the liquid crystal layer, and a voltage is applied between the pixel electrode and the common electrode. In a liquid crystal display device that performs display by controlling the alignment of liquid crystal, the liquid crystal alignment control layer includes a diamine composed of one or two cyclic structures and a tetracarboxylic acid composed of one or two cyclic structures. And a polymer material having at least one alkyl group bonded to the cyclic structure of at least one of the diamine and the tetracarboxylic acid. Crystal display device. 12. The liquid crystal display device according to claim 11, wherein said alkyl group has 2 or less carbon atoms. 13. The liquid crystal display device according to claim 11, wherein an elastic modulus of the polymer material constituting the liquid crystal alignment control layer is 5 gigapascal (GPa) or more. 14. The method according to claim 1, wherein the diamine is a diamine represented by Formula 6 or Formula 7.
The liquid crystal display device according to any one of claims 1 to 14. [R21 to R32 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3)
₂ -, - SO ₂ - represents either. ] 15. The liquid crystal display device according to claim 11, wherein the tetracarboxylic acid is a tetracarboxylic acid represented by Formula 8 or Formula 9. . [R33 to R40 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted or mono- or polysubstituted with halogen, particularly F or Cl. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3) 2 -,
—SO ₂ —. ] 16. The polymer material is one or more of diamines represented by the chemical formulas 6 and 7, and one or two kinds of tetracarboxylic acids represented by the chemical formula 8 or 9 The compound is synthesized from the above tetracarboxylic acid.
The liquid crystal display device according to claim 1. [R21 to R32 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3)
₂ -, - SO ₂ - represents either. ] [R33 to R40 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted or mono- or polysubstituted with halogen, particularly F or Cl. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3) 2 -,
—SO ₂ —. ] 17. The polymer material is synthesized from a tetracarboxylic acid represented by Chemical Formula 10 and one or more diamines represented by Chemical Formula 6 or Chemical Formula 7. The liquid crystal display device according to any one of claims 11 to 14. [R21 to R32 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3)
₂ -, - SO ₂ - represents either. ] 18. The polymer material according to claim 1, wherein the polymer material is a tetracarboxylic acid represented by the formula (10), one or more tetracarboxylic acids represented by the formula (8) or (9) and a diamine represented by the formula (6) or (7) The liquid crystal display device according to any one of claims 11 to 15, wherein the liquid crystal display device is synthesized using one or more diamines. [R33 to R40 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted or mono- or polysubstituted with halogen, particularly F or Cl. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3) 2 -,
—SO ₂ —. ] [R21 to R32 represent a hydrogen atom, a halogen atom or an alkyl group, and the alkyl group is unsubstituted, monosubstituted with halogen, particularly F or Cl, or polysubstituted. X is a single bond or-
O -, - S -, - CO -, - CH 2 -, - C (CH 3)
₂ -, - SO ₂ - represents either. ] 19. The liquid crystal display device according to claim 11, wherein the liquid crystal has a negative dielectric anisotropy. 20. The liquid crystal display according to claim 11, wherein at least one of the pixel electrode and the common electrode is formed using a transparent conductive material. apparatus. 21. The transparent conductive material is indium tin oxide
The liquid crystal display device according to claim 20, wherein the liquid crystal display device is (ITO), indium zinc oxide (IZO), or indium germanium oxide (IGO). 22. The liquid crystal display device according to claim 1, wherein said active element is a thin film transistor. 23. The liquid crystal display device according to claim 1, wherein the polymer material is polyimide, polyamic acid, or a mixture thereof.