JPH10319409A - Formation of oriented film for active matrix type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oriented film for an active matrix type liquid crystal display device having high quality by obtaining the compatibility of the display uniformity to make display abnormality obscure with a wide visual field angle. SOLUTION: At least the respective electrodes which constitute display pixels and are so constituted as to impress substantially parallel electric fields 9 on a liquid crystal layer in the plane direction of one substrate 7a and the other substrate 7b and polarization means 8a, 8b which are connected an outer control means arbitrarily controlling the electric fields 9 according to display patterns and change the optical characteristics of the light emitted from the other substrate 7b by the orientation state of the liquid crystal layer by the impressed electric fields 9 are provided in this device. Orientation controllability is imparted to at least one of the first oriented film and the second oriented film by printing the surface of the substrate with polyamic acid and baking the same to form a thin film of polyimide and irradiating the thin film with polarized light to bond the polyimide to each other.

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 device in which an electric field parallel to a substrate is applied to a liquid crystal layer to control the orientation of liquid crystal, and more particularly to a wider viewing angle and non-uniform display. The present invention relates to a method for forming an alignment film for an active matrix type liquid crystal display device, which has improved compatibility.

[0002]

2. Description of the Related Art Liquid crystal displays are widely used as devices for displaying various images including still images and moving images.

In a liquid crystal display device, a liquid crystal layer is sandwiched between two substrates, at least one of which is made of transparent glass or the like, and a voltage is selectively applied to various electrodes for pixel formation formed on the substrate. Is applied to turn on and off a predetermined pixel, and the above-mentioned various electrodes and an active element for pixel selection are formed, and the active element is selected to turn on and off a predetermined pixel. .

[0004] In particular, the latter type of liquid crystal display device is called an active matrix type, and has become the mainstream of the liquid crystal display device because of its contrast performance, high-speed display performance and the like.

A conventional active matrix type liquid crystal display device employs a so-called vertical electric field method in which an electric field for changing the orientation of a liquid crystal layer is applied between an electrode formed on one substrate and an electrode formed on the other substrate. Was adopted.

However, in recent years, a so-called in-plane switching (IPS) liquid crystal display device has been realized in which the direction of the electric field applied to the liquid crystal layer is made substantially parallel to the substrate surface. As this in-plane switching type liquid crystal display device, a device in which a very wide viewing angle is obtained by using a comb electrode on one of two substrates is known (Japanese Patent Publication No. 63-21907, US Japanese Patent No. 4345249).

On the other hand, as a typical example of a method for orienting liquid crystal molecules constituting a liquid crystal layer in a predetermined direction, a thin film of an organic polymer such as a polyimide (hereinafter simply referred to as polyimide) is formed on a substrate. An organic alignment film having an alignment control function by rubbing is used.

In the rubbing treatment (hereinafter simply referred to as rubbing), the surface of a polyimide-based polymer thin film formed on a substrate is rubbed with a cloth wound around a roller in order to uniformly align liquid crystal molecules constituting a liquid crystal layer. Work.

A method of irradiating light to an alignment film of an organic polymer thin film of a polyimide or the like formed on a substrate to have an alignment control function (photo alignment method) is also known (US Pat. No. 4,974,941). Specification, JP-A-5-34699
JP, JP-A-6-281937, JP-A-7-2
No. 47319).

However, these conventional photo-alignment techniques are not applied to the above-described horizontal electric field method, but have a different design concept from the vertical electric field method in which various electrodes for forming pixels are formed only on one substrate. No particular effect due to the application of the photo-alignment technology to the display method of the electric field method is taken into consideration at all, and the concept regarding the coupling of polyimide by light is not mentioned.

[0011]

The active matrix type liquid crystal display device of the vertical electric field type according to the prior art can achieve a wider viewing angle than the liquid crystal display device of the twisted nematic type, but has a large screen. There are problems such as display uniformity, limitation of viewing angle expansion, and coloring of yellow or blue in a specific direction.

Further, the so-called pretilt angle differs depending on the kind of the polyimide-based polymer material used as the alignment film. At a high pretilt angle, the viewing angle characteristics are not good and there is a problem that the pretilt angle is affected by rubbing conditions.

In a lateral electric field system in which the liquid crystal molecules constituting the liquid crystal layer are oriented in the same direction on the upper and lower substrates, a so-called normally black system which performs black display when no voltage is applied and white display when voltage is applied. Is generally adopted. This method has a drawback that display abnormalities due to display defects become more remarkable as compared with the so-called normally white method in which white display is performed when no voltage is applied, which is adopted in the conventional twisted nematic method.

Furthermore, in the homogeneous alignment of liquid crystal molecules, it is remarkable that a slight alignment abnormality causes display problems.

Furthermore, in the lateral electric field method, the liquid crystal responds to an electric field instead of a voltage on the driving principle.
There is also a disadvantage that a slight change in the cell gap (gap between two substrates = thickness of the liquid crystal layer) is observed as non-uniformity of display.

On the other hand, in the method of forming the orientation control ability by the rubbing treatment, static electricity is generated in the film, and the film surface tends to be contaminated. The static electricity generated in the alignment film by the rubbing process is the active element thin film transistor (TFT)
In some cases, or its switching characteristics may be changed. Further, when the alignment film is contaminated by the rubbing process, the frequency dependence of the threshold voltage of the pixel becomes non-uniform. Furthermore, as the size of the substrate increases, it becomes difficult to control the load during rubbing over the entire area of the substrate, so that the rubbing may cause scratches and unevenness on a large substrate.

Further, fine shavings are generated from the alignment film rubbed with the cloth used in the rubbing process, and these fine shavings become a large source of dust in a clean room for manufacturing a liquid crystal display device. It has a serious problem that it is a major factor that lowers the yield of the manufacturing process.

Further, there are uneven steps in the configuration of active elements such as various electrodes for forming pixels and TFTs formed on the surface of the substrate, and a portion which is not rubbed due to the steps occurs during the rubbing process. This causes light leakage in black display, resulting in a decrease in contrast.

The method of aligning a liquid crystal using an alignment film provided with an alignment control function by rubbing, a so-called photo-alignment method, can be classified into three, photo-isomerization, photo-dimerization, and photo-decomposition, based on its action.

Among these methods, only a method using polyvinyl cinnamate is known as a photo-alignment method utilizing photodimerization. However, this method has a problem in heat resistance and has not been put to practical use.

In addition, the photo-alignment using the photo-decomposition method has a disadvantage that the afterimage characteristics are deteriorated due to radical generation.

In the photo-alignment using the photo-dimerization method,
There is a problem in heat resistance and light resistance, and it is difficult to achieve both heat resistance and afterimage characteristics.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to obtain a high-quality image display by achieving a wide viewing angle and display uniformity in which display abnormalities are not noticeable. An object of the present invention is to provide a method for forming an alignment film for an active matrix type liquid crystal display device.

[0024]

Means for Solving the Problems To solve the above problems, the present invention uses the following means (1) and (2). That is, (1) one substrate provided with at least a scanning signal electrode, a video signal electrode, a pixel electrode, and an active element constituting a display pixel; and a substrate directly or insulated on each electrode constituting the display pixel and the active element. A first alignment film formed with a layer interposed therebetween, a second alignment film having a second alignment film formed so as to face the first alignment film, and the other substrate bonded to the one substrate with a small gap; Having a liquid crystal layer sandwiched between opposing gaps between the first alignment film and the second alignment film, wherein each of the electrodes constituting the display pixel is configured such that the one substrate and the other electrode are arranged with respect to the liquid crystal layer. The liquid crystal layer is configured to apply an electric field substantially parallel to the plane direction of the substrate, and is connected to external control means for arbitrarily controlling the electric field in accordance with a display pattern. of A polarizing means for changing an optical characteristic of light emitted from the one substrate according to an alignment state, the method comprising forming an alignment film for an active matrix liquid crystal display device, wherein the first alignment film and the second alignment film At least one of the alignment films is printed with a polyamic acid on the substrate, baked to form a polyimide thin film, and the thin film is irradiated with polarized light to bond between the polyimides, thereby providing alignment control ability. Give.

(2) The polyimide thin film of (1) is formed by reacting cinnamoyl with an organic compound having a diamine component.

Next, the operation of the above means will be described.

The above-mentioned problems caused by widening of the viewing angle, uniformity of display, and rubbing can be solved by providing the alignment film with the ability to control the alignment of liquid crystal using light.

In the photo-alignment method, it has been confirmed that the anchoring strength for restricting the alignment of the liquid crystal is lower than that of rubbing, and that the pretilt angle is small. This is why the viewing angle characteristics and the display uniformity are remarkably improved by combining the means for orienting.

However, as described above, when photoisomerization is used among the photoalignment methods, there are problems with heat resistance and light resistance, and when photodecomposition is used, there is a problem of afterimage due to radical generation or the like. is there. Polyvinyl cinnamate is known as a method utilizing photodimerization, and although there is basically no problem of an afterimage such as photolysis, there is a problem in heat resistance.

Therefore, by introducing a photochromic portion capable of photodimerization into polyimide having excellent heat resistance, a photo-alignment film having excellent heat resistance and excellent afterimage characteristics can be obtained.

In an alignment film provided with an alignment control function by polarized light using a polyimide-based polymer thin film, the so-called pretilt angle is small and almost zero, and the anchoring strength for restricting the liquid crystal alignment is lower than that by rubbing. Have confirmed.

The alignment control ability by light irradiation is given to only one of the pair of substrates on which the polyimide thin film is formed, and the other is subjected to ordinary rubbing, so that the pretilt angle can be easily asymmetrical between the upper and lower substrates. It can be. Such asymmetry of the pretilt angle is effective in increasing the response speed of the liquid crystal.

Further, a technique using this light (photo-alignment method)
The viewing angle characteristic is further improved by setting the orientation directions of the liquid crystal when no voltage is applied to two or more. In the homogeneous orientation in one direction, the liquid crystal molecules are oriented in the same direction when no voltage is applied, and coloring occurs in the oblique direction viewed from the long axis and short axis of the director due to the difference in birefringence.

However, when two or more initial alignment directions are used, the direction in which the liquid crystal molecules face when a voltage is applied is divided into two directions. As a result, optical compensation is performed and the problem of coloring is eliminated. This is the so-called multi-domain method.

Until now, in the horizontal electric field method, a multi-domain method was possible by changing the electrode wiring structure, but there was a drawback that the aperture ratio was reduced. If the liquid crystal is aligned by appropriately irradiating polarized light to the polyimide alignment film in two directions, a multi-domain method can be realized without changing the electrode structure. Moreover. As described above, since the pretilt angle is small, the viewing angle is wide, and the anchoring strength is weak, the display uniformity is also excellent.

FIG. 8 is a schematic diagram for explaining an example of a polarized light irradiation method for imparting a polarization control function by irradiating polarized light to a polyimide-based polymer thin film, wherein 7 is a substrate, and 30 is an excimer laser as a light source. (Wavelength 353 nm), 31 is an attenuator, 32 and 34 are relay optical systems, 33 is a homogenizer, 35 is a mask, 36 is a projection lens,
7, a polarizer (polarizer); and 38, a sampling stage.

In FIG. 3, a substrate 7 on which a polyimide polymer thin film is formed is placed on a sendable sampling stage 38, and a laser beam emitted from an excimer laser 30 is passed through an attenuator 31 and a relay optical system 32 to a homogenizer 33. After the homogenization, the relay optical system 34,
The light is incident on the polarizer 37 via the mask 35 and the projection lens 36. The laser light polarized in a predetermined direction by the polarizer 37 is irradiated on the polyimide polymer thin film of the substrate 7 mounted on the sampling stage 38 which is sent at a constant speed in a constant direction. As a result, a predetermined orientation control ability is imparted to the polyimide-based polymer thin film.

It is known that, when a polyimide-based polymer thin film is irradiated with polarized light, charges easily accumulate on the irradiated surface. Therefore, the DC component easily accumulates in the liquid crystal panel, which causes an afterimage. Therefore, the specific resistance of the liquid crystal is 1
When the value is smaller than 0 ¹³ Ω · cm, the afterimage can be improved by compensating the charges in the liquid crystal.

Further, in the rubbing, a non-rubbed region is formed due to a step on the substrate surface, which causes a decrease in contrast. However, when light is used for liquid crystal alignment, such a phenomenon does not occur, and the step is 0.3 μm or more. There is no problem.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to examples.

[Embodiment 1] FIG. 1 is a conceptual diagram for explaining the entire structure of an active matrix type liquid crystal display device to which the present invention is applied. 8a is a lower polarizing plate, 8b is an upper polarizing plate,
4 is a thin film transistor (TF) as an active element
T), 18 denotes a scanning electrode driving circuit, 19 denotes a signal electrode driving circuit, 20 denotes a common electrode driving circuit, 22a and 22b denote black matrices, and 23 denotes a color filter.

This liquid crystal display device is a so-called lateral electric field type (IP).
S), in which various electrodes and switching elements for pixel selection are formed on one substrate (generally, a lower substrate), and only a color filter is formed on the other substrate (upper substrate) and sandwiched between both substrates. A lighting / non-lighting is controlled by forming an electric field in a direction substantially parallel to the substrate plane in the liquid crystal layer and changing the orientation direction of liquid crystal molecules forming the liquid crystal layer in the substrate plane.

FIG. 2 is a cross-sectional view of one pixel of this type of liquid crystal display device, wherein 1 is a common electrode, 2 is a gate insulating film, 3 is a video signal electrode, 4 is a pixel electrode, 5a is a lower alignment film, 5b is an upper alignment film, 6 is a liquid crystal molecule, 7a is a lower substrate, 7b is an upper substrate, 8a is a lower polarizing plate, 8b is an upper polarizing plate, 9 is an electric field, 22
Is a black matrix, 23 is a color filter, 24 is an overcoat film, and 26 is an insulating film (PSV).

In FIG. 1, a lower substrate 7a has a thin film transistor 14 (see FIG. 1), a video signal electrode (pixel electrode) 3 as an electrode for driving liquid crystal, and a common electrode 1 formed of a silicon nitride film (insulating film). An insulating film 26 is formed on (SiN) 2 and covers these electrodes. A color filter 23 partitioned by a black matrix 22 is formed on the upper substrate 7b. The liquid crystal molecules 6 are disposed between the lower alignment film 5a and the upper alignment film 5b formed on the opposing surfaces of the substrates 7a and 7b. Liquid crystal layer is sandwiched. In addition,
A lower polarizing plate 8a and an upper polarizing plate 8b are laminated on the outer surface of the lower substrate 7a and the outer surface of the upper substrate 7b, respectively. The video signal electrode and the common electrode 1 which are in direct contact with the alignment film and the liquid crystal layer are formed of ITO (Indium Tin) in consideration of metal corrosion.
Oxide).

FIG. 3 is a conceptual diagram of a drive circuit of an active matrix type liquid crystal display device, wherein 17 is a control circuit, 18 is a scan electrode drive circuit, 19 is a signal electrode drive circuit, 20 is a common electrode drive circuit, and 21 is It is an active matrix type liquid crystal display device. Incidentally, C _LC is the capacitance component of the liquid crystal, the C _S indicates a holding capacitance.

Active matrix type liquid crystal display device 21
The TFTs for switching the respective pixels include a scan electrode drive circuit 18, a signal electrode drive circuit 19, and a common electrode drive circuit 2.
0 selectively turns on / off. This on / off is controlled by the control circuit 17.

The liquid crystal layer in which the alignment direction of the molecules changes when the TFT is turned on / off has an initial state in the alignment state (alignment control ability) of the lower and upper alignment films 5a and 5b on which the substrates 7a and 7b are formed. The orientation direction is set.

In this embodiment, a polyimide obtained by chemically modifying cinnamate (cinnamate) was used as the alignment film. That is, cinnamoyl chloride was reacted with 2,4-dinitrophenol to obtain 2,4-dinitrophenol cinnamate. And NaBH ₄ / SnCl ₂
Was used to reduce only the nitro group to obtain 2,4-diaminophenol cinnamate.

The polyamic acid was obtained by mixing the 2,4-diaminophenol cinnamate with 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride.

Thereafter, a polyimide film as an alignment film was formed on the active element substrate (TFT substrate) by ordinary printing and baking. Next, in order to align the liquid crystal on the surface, polarized UV was applied to the surface of the polyimide alignment film in the configuration shown in FIG. A XeF excimer laser (wavelength: 353 nm) was used as a light source.

At this time, the irradiation energy is 10 mJ / c
Irradiation was performed for 76 shots at m ² . The substrate can be scanned at a constant speed, and the irradiation surface is uniformly polarized with UV.
The feed speed of the substrate was set so that six shots were irradiated.

Further, the above-mentioned polyimide was applied to the outermost surface of a color filter substrate with a black matrix, which is another substrate, and irradiated with polarized UV as described above. Note that the liquid crystal molecules are aligned in a direction perpendicular to polarized light.

FIG. 4 is an explanatory view of the definition of the alignment control direction of the alignment film and the direction of the transmission axis of the polarizing plate, where 9 is the electric field direction, 10 is the alignment control direction of the alignment film, and 11 is the transmission axis direction of the polarizing plate. .

In the present embodiment, as shown in the figure, the easy axes of the alignment molecules of the liquid crystal on the interface with the upper and lower alignment films are substantially parallel to each other, and formed with the direction of the applied electric field. The angle was set to 75 degrees (φ _LC1 = φ _LC2 = 75 °).

The dielectric anisotropy Δε is positive between the two substrates, the value is 7.3, and the refractive index anisotropy Δn is 0.07.
4 (wavelength 589 nm, 20 ° C.) to form a liquid crystal layer with a nematic liquid crystal composition interposed therebetween.

The gap between the two substrates, that is, the cell gap d, was set by dispersing spherical polymer beads between the substrates, and was set to 4.0 μm when the liquid crystal was sealed. Therefore,
Δn · d is 0.296 μm.

[0057] Two polarizing plates (for example, G manufactured by Nitto Denko Corporation)
1220 DU) sandwiching the liquid crystal panel, the polarization transmission axis of one polarizing plate is set to φ _p1 = 75 °, and the other is orthogonal to this.
That is, φ _p2 = −15 °. In this embodiment, a normally-closed characteristic is employed in which a dark state occurs at a low voltage (V _OFF ) and a bright state occurs at a high voltage (V _ON ).

FIG. 5 is a schematic diagram for explaining the operation of liquid crystal molecules in a bright state and a dark state in a liquid crystal display device of a horizontal electric field type.

FIG. 7A is a sectional view of a dark state at an applied voltage (V _OFF ), FIG. 7B is a sectional view of a dark state at a bright state at an applied voltage (V _ON ), and FIG. (V _OFF ) is a sectional view of a dark state in a dark state, and (d) is a plan view of an applied voltage (V _ON ) in a bright state.

In the dark state shown in (a) and (c), since no electric field exists between the common electrode 1 and the pixel electrode 4, the liquid crystal molecules 6 are in the initial alignment state and are set on the lower surface of the lower substrate 7a. The illumination light from the backlight (not shown) is
It does not reach b side.

On the other hand, in the bright state shown in (b) and (d), an electric field 9 exists between the common electrode 1 and the pixel electrode 4, and the orientation direction of the liquid crystal molecules 6 is rotated by the electric field 9, so that the lower substrate is rotated. 7a
Illumination light from a backlight (not shown) installed on the lower surface of the device reaches the upper substrate 7b side. As described above, in the liquid crystal display device of the in-plane switching mode, the liquid crystal molecules 6 rotate in a plane parallel to the plane of the substrate, that is, in the horizontal direction, and form an image by switching between a bright state and a dark state.

FIGS. 6A and 6B are explanatory views of an electrode structure in a first embodiment of the active matrix type liquid crystal display device according to the present invention, wherein FIG. 6A is a plan view seen from a direction perpendicular to the substrate, and FIG.
3A is a cross-sectional view taken along line AA of FIG. 3A, and FIG. 3C is a cross-sectional view taken along line BB of FIG.

The thin film transistor (TFT) 14 is a pixel electrode (source electrode) 4 and a video signal electrode (drain electrode).
3, a scanning electrode (gate electrode) 12 and amorphous silicon (a-Si) 13. Scan electrode 1
2 and a part 1a of the common electrode, and a video signal electrode 3 and a part 4a of the pixel electrode were formed by patterning the same metal layer. Further, after the insulating film 25 is formed, a part 1b of the common electrode, which is a part for driving the liquid crystal, is connected to the part 1a of the common electrode by a through hole, and the pixel electrode is also contacted by a through hole in the transistor part. Thus, a part 4b of the pixel electrode was formed. A part 1b of the common electrode and a part 4b of the pixel electrode were formed using ITO.

The capacitive element 16 forming the storage capacitor was formed to have a structure in which an insulating protective film (gate insulating film) 2 was sandwiched between the pixel electrode 4 and the common electrode 1 in a region connecting between the two common electrodes 1. The pixel electrodes are arranged between the three common electrodes 1 as shown in the plan view (a). The pixel pitch is 100 μm in the horizontal direction (that is, between the video signal wiring electrodes).
m, 300 μm in the vertical direction (that is, between the scanning wiring electrodes)
It is. The electrode width is set such that the scanning electrode, the signal electrode, and the common electrode wiring portion (a portion extending in parallel (horizontal direction in FIG. 7 to be described later) with the scanning wiring electrode), which are wiring electrodes extending over a plurality of pixels, are widened. Avoid flaws. Its width is 10μ each
m, 8 μm and 8 μm.

On the other hand, the width of the pixel electrode and the common electrode extending in the longitudinal direction of the pixel electrode and the common electrode signal wiring electrode were slightly reduced to 5 μm and 6 μm, respectively.
By reducing the width of these electrodes, the possibility of disconnection due to the incorporation of foreign matter or the like increases, but in this case, a partial defect of one pixel is sufficient, and no line defect occurs. Signal electrode 3 and common electrode 1
Are provided at an interval of 2 μm via the insulating film 25. The number of pixels was 640 × 3 × 480 with 640 × 3 (R, G, B) signal wiring electrodes and 480 wiring electrodes.

FIGS. 7A and 7B are explanatory diagrams of the structure of a color filter substrate with a black matrix (BM), wherein FIG. 7A is a plan view as viewed from a direction perpendicular to the substrate surface, and FIG.
FIG. 3C is a cross-sectional view along the line A ′, and FIG. 3C is a cross-sectional view along the line BB ′ in FIG.

As the black matrix 22, a material obtained by mixing carbon and an organic pigment was used. The arrangement of the black matrix 22 with respect to the electrode substrate is shown by a broken line in FIG.

After the formation of the black matrix 22, R, G, and B pigments were dispersed in a photosensitive resin, and each color filter 23 was formed by coating, patterning exposure, and development. Then, an epoxy-based polymer thin film was applied and formed as an overcoat film 24 on the color filter 23.

The active matrix type liquid crystal display device of Example 1 obtained in this manner has a wide viewing angle in which gradation inversion does not occur while maintaining a contrast of 10 or more at 80 degrees, up, down, left and right, and uniform display. A good image display can be obtained.

[Embodiment 2] The second embodiment of the present invention is the same as the first embodiment except for the following points.

That is, in this example, polyimide was employed as the alignment film of the active element substrate, and its surface was irradiated with polarized UV to impart liquid crystal alignment capability. A KrF excimer laser (wavelength: 353 nm) was used as a polarized light source, and the irradiation energy was 10 mJ / cm ² and 51 shots were irradiated. The substrate can be scanned at a constant speed, and the feed speed of the substrate was set so that the irradiation surface was uniformly irradiated with 51 shots of polarized UV.

A polyimide was applied to the outermost surface of the other substrate, a color filter substrate with a black matrix, and rubbed. Note that the liquid crystal molecules are aligned in a direction perpendicular to polarized light. In this embodiment, the directions of the easy axes of the alignment molecules on the upper and lower interfaces are substantially parallel to each other, and the angle formed with the applied voltage in the pixel is 75 degrees (φ
_LC1 = _φLC2 = 75 °).

The active matrix type liquid crystal display device of the present embodiment obtained in this manner has a wide viewing angle in which no grayscale inversion occurs while maintaining a contrast of 10 or more at 80 degrees, up, down, left and right, and display. The uniformity was also good. In addition, the response time (the luminance change at the time of voltage on / off, 0
% To 90% and 100% to 10%) is 48m
s.

[Embodiment 3] A third embodiment of the present invention is the same as the first embodiment except for the following points.

That is, in this example, polyimide was employed as the alignment film of the active element substrate, and its surface was irradiated with polarized UV to impart liquid crystal alignment capability. A KrF excimer laser (wavelength: 353 nm) was used as a polarized light source, and the irradiation energy was 5 mJ / cm ² and 51 shots were irradiated. The substrate can be scanned at a constant speed, and the feed speed of the substrate was set so that the irradiation surface was uniformly irradiated with 51 shots of polarized UV.

A polyimide was applied to the outermost surface of the other substrate, a color filter substrate with a black matrix, and irradiated with polarized UV light in the same manner as described above. Note that the liquid crystal molecules are aligned in a direction perpendicular to polarized light. In the present embodiment, the directions of the easy axes of the alignment molecules on the interface between the upper and lower substrates are substantially parallel to each other, and the angle between the pixel and the applied voltage is 89 degrees (φ _LC1 = φ _LC2 ) as shown in FIG. = 89
°) and 91 degrees (φ _LC1 = φ _LC2 = 91 °), and the upper and lower substrates were irradiated with polarized UV twice using a suitable mask.

The thus-obtained active matrix type liquid crystal display device of the present embodiment has a wide viewing angle in which no grayscale inversion occurs while maintaining a contrast of 10 or more at 80 degrees, up, down, left and right, and color shift. Very little uniform display properties were obtained.

[Embodiment 4] A fourth embodiment of the present invention is the same as the first embodiment except for the following points.

That is, in the present embodiment, a liquid crystal in which a cyano compound having a specific resistance of 4 × 10 ¹² Ω · cm before encapsulation was mixed as the liquid crystal was used. The specific resistance of the liquid crystal remaining in the liquid crystal dish after sealing was 2 × 10 ¹¹ Ω · cm.

The active matrix type liquid crystal ratio device obtained in this manner has a wide viewing angle at which gradation inversion does not occur while maintaining a contrast of 10 or more at 80 degrees, up, down, left and right, and uniformity of display. Was also good. In addition, no afterimage was observed.

FIG. 9 is an exploded perspective view for explaining the whole structure of an active matrix type liquid crystal display device using an alignment film according to the present invention.

FIG. 13 shows a liquid crystal display device (hereinafter, referred to as a liquid crystal display device) according to the present invention.
The liquid crystal display panel, the circuit board, the backlight, and a module in which other components are integrated: this is referred to as MDL).

SHD is a shield case (also called a metal frame) made of a metal plate, WD is a display window, INS1
To 3 are insulating sheets, PCB1 to 3 are circuit boards (PCB1
Is a drain side circuit board: a video signal line driving circuit board, P
CB2 is a gate side circuit board, PCB3 is an interface circuit board), JN1 to 3 are joiners for electrically connecting the circuit boards PCB1 to 3, TCP1 and TCP2 are tape carrier packages, PNL is a liquid crystal display panel, G
C is a rubber cushion, ILS is a light shielding spacer, PRS is a prism sheet, SPS is a diffusion sheet, GLB is a light guide plate, RFS is a reflection sheet, MCA is a lower case (mold frame) formed by integral molding, MO is MC
A opening, LP is fluorescent tube, LPC is lamp cable, G
B is a rubber bush supporting the fluorescent tube LP, BAT is a double-sided adhesive tape, BL is a backlight made of a fluorescent tube, a light guide plate, and the like, and a liquid crystal display module MDL is assembled by stacking diffusion plate members in the arrangement shown in the figure. .

The liquid crystal display module MDL has two kinds of storage / holding members of a lower case MCA and a shield case SHD, and includes insulating sheets INS1 to INS3 and circuit boards PCB1 to PCB1.
3. A metal shield case SHD in which a liquid crystal display panel PNL is stored and fixed, and a lower case MCA in which a backlight BL including a fluorescent tube LP, a light guide plate GLB, a prism sheet PRS, and the like are stored are combined.

An integrated circuit chip for driving each pixel of the liquid crystal display panel PNL is mounted on the video signal line driving circuit board PCB1, and the interface circuit board PC
The B3 includes an integrated circuit chip that receives a video signal from an external host, receives a control signal such as a timing signal, and a timing converter TCON that processes a timing to generate a clock signal.

The clock signal generated by the timing converter is integrated on the video signal line driving circuit board PCB1 via the clock signal line CLL laid on the interface circuit board PCB3 and the video signal line driving circuit board PCB1. Supplied to the circuit chip.

The interface circuit board PCB3 and the video signal line driving circuit board PCB1 are multilayer wiring boards, and the clock signal line CLL is the interface circuit board PCB3 and the video signal line driving circuit board PC
It is formed as an inner wiring of B1.

The liquid crystal display panel PNL has a drain-side circuit board PCB1, a gate-side circuit board PCB2, and an interface circuit board PC for driving TFTs.
B3 is connected by tape carrier packages TCP1 and TCP2, and the circuit boards are connected by joiners JN1, JN2, JN3.

The liquid crystal display panel PNL is an in-plane switching mode active matrix type liquid crystal display device according to the present invention, and the liquid crystal alignment ability formed on the alignment film is given by the polarized light described in the above embodiment.

FIG. 10 is an external view of a personal computer for explaining an example of an information processing apparatus equipped with the liquid crystal display device according to the present invention.
Is an inverter power supply for driving the fluorescent tube, and CPU is a central processing unit on the host side.

As shown in the figure, a personal computer on which the liquid crystal display device according to the present invention is mounted is a video signal line driving circuit board (horizontal driving circuit board: drain side circuit board) PC
By arranging B1 only at the upper part of the screen, a space below the display unit (keyboard side) can be given a margin, and the installation space (hinge space) of the hinge connecting the keyboard unit and the display unit can be reduced. Therefore, the outer size of the display unit can be reduced, and the size of the entire personal computer can be reduced.

[0092]

As described above, according to the present invention,
By irradiating polarized light to a thin film of an alignment film material such as a polyimide-based organic film in the horizontal electric field method, a new bond between polyimides is generated and the liquid crystal is aligned, so that the wide viewing angle is improved even more than the conventional horizontal electric field method. An active matrix type liquid crystal display device which achieves both display uniformity can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an overall configuration of an active matrix type liquid crystal display device according to the present invention.

FIG. 2 is a sectional view of one pixel of an active matrix type liquid crystal display device according to the present invention.

FIG. 3 is a conceptual diagram of a drive circuit of an active matrix type liquid crystal display device according to the present invention.

FIG. 4 is an explanatory diagram of a definition of an alignment control direction of an alignment film and a transmission axis direction of a polarizing plate.

FIG. 5 is a schematic diagram for explaining the operation of liquid crystal molecules in a bright state and a dark state in a liquid crystal display device of an in-plane switching mode.

FIG. 6 is an explanatory diagram of an electrode structure in a first embodiment of the active matrix type liquid crystal display device according to the present invention.

FIG. 7 is a structural explanatory view of a color filter substrate with a black matrix (BM).

FIG. 8 is a schematic diagram illustrating an example of a polarized light irradiation method for irradiating polarized light to a polyimide-based polymer thin film to impart polarization control ability.

FIG. 9 is an exploded perspective view illustrating an overall configuration of an active matrix type liquid crystal display device using an alignment film according to the present invention.

FIG. 10 is an external view of a personal computer explaining an example of an information processing device in which an active matrix type liquid crystal display device using an alignment film according to the present invention is mounted.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Common electrode 2 Gate insulating film 3 Video signal electrode 4 Pixel electrode 5a Lower alignment film 5b Upper alignment film 6 Liquid crystal molecule 7a Lower substrate 7b Upper substrate 8a Lower polarizing plate 8b Upper polarizing plate 9 Electric field 14 Thin film transistor (TF) as an active element
T) 18 scan electrode drive circuit 19 signal electrode drive circuit 20 common electrode drive circuit 22 (22a, 22b) black matrix 23 color filter 24 overcoat film 26 insulating film (PSV) 30 excimer laser (wavelength 248 nm) 31 attenuator 32, 34 Relay optical system 33 Homogenizer 35 Mask 36 Projection lens 37 Polarizer (Polarizer) 38 Sampling stage.

Claims (2)

[Claims] 1. A substrate provided with at least a scanning signal electrode, a video signal electrode, a pixel electrode and an active element constituting a display pixel, and directly or insulated on an upper layer of each electrode constituting the display pixel and the active element. A first alignment film formed via a layer, and a second alignment film including a second alignment film formed so as to face the first alignment film and bonded to the one substrate with a small gap, A liquid crystal layer sandwiched between opposing gaps between the first alignment film and the second alignment film, wherein each electrode constituting the display pixel is configured such that the one substrate and the other electrode correspond to the liquid crystal layer. The liquid crystal layer is configured to apply an electric field substantially parallel to the plane direction of the substrate, and is connected to external control means for arbitrarily controlling the electric field in accordance with a display pattern. Arrangement A polarizing means for changing an optical characteristic of light emitted from the one substrate according to an orientation state, the method comprising: forming an alignment film for an active matrix type liquid crystal display device, wherein the first alignment film and the second At least one of the alignment films is printed with a polyamic acid on the substrate, baked to form a polyimide thin film, and the thin film is irradiated with polarized light to bond between the polyimides, thereby providing alignment control ability. A method for forming an alignment film for an active matrix liquid crystal display device, the method comprising: 2. The method for forming an alignment film for an active matrix type liquid crystal display device according to claim 1, wherein said polyimide thin film is formed by reacting cinnamoyl with an organic compound having a diamine component.