JP3619007B2 - Active matrix liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which the remaining image characteristics are improved and makes compatible a wide viewing field angle and inconspicuous display abnormality. SOLUTION: This device is equipped with a liquid crystal panel which is equipped with a liquid crystal layer consisting of a liquid crystal composition 6 sandwiched between 1st and 2nd orientation films formed on one substrate 7a and another substrate 7b and a polarizing means 8b for changing optical characteristics according to the orientation state of the liquid crystal layer on the surface of at least one substrate 7a on the opposite side to the liquid crystal layer and is provided with electrodes formed on one of the substrate 7a so that an electric field substantially in parallel with the substrate surface is applied to the liquid crystal layer and a control means which is connected to the respective electrodes formed on one substrate constituting the liquid crystal panel and capable of optionally controlling the electric field applied to the liquid crystal layer according to a display panel. At least one of a 1st orientation film 5a and a 2nd orientation film 5b has the modulus of film elasticity above about 5 GPa at 25 deg.C and an optical orientation film is applied to liquid crystal orientation control capability by being irradiated with linearly polarized light.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device that controls the alignment of liquid crystal by applying an electric field parallel to a substrate to a liquid crystal layer, and in particular, an active matrix type having a wide viewing angle and improved display non-uniformity. The present invention relates to a liquid crystal display device.
[0002]
[Prior art]
Liquid crystal display devices are widely used as devices that display various images including still images and moving images.
[0003]
This type of liquid crystal display device basically comprises a so-called liquid crystal panel in which a liquid crystal layer is sandwiched between two substrates, at least one of which is made of transparent glass or the like, and pixel formation formed on the substrate of the liquid crystal panel. A type in which a predetermined pixel is turned on and off by selectively applying a voltage to various electrodes for use, a predetermined element is formed by forming the various electrodes and an active element (switching element) for pixel selection and selecting the active element. It is classified into a form in which the pixel is turned on and off.
[0004]
In particular, the latter type of liquid crystal display device is referred to as an active matrix type, and has become the mainstream of liquid crystal display devices due to contrast performance, high-speed display performance, and the like. Conventional active matrix liquid crystal display devices employ a so-called vertical electric field method in which an electric field for changing the orientation direction of a liquid crystal layer is applied between an electrode formed on one substrate and an electrode formed on the other substrate. It was.
[0005]
However, in recent years, a so-called lateral electric field type (also referred to as IPS type) liquid crystal display device has been realized in which the direction of the electric field applied to the liquid crystal layer is substantially parallel to the substrate surface. As this lateral electric field type liquid crystal display device, a liquid crystal display device using a comb electrode on one of two substrates to obtain a very wide viewing angle is known (Japanese Patent Publication No. 63-21907, US). Japanese Patent No. 4345249).
[0006]
On the other hand, as a typical example of a method for aligning liquid crystal molecules constituting a liquid crystal layer in a predetermined direction, a polyimide-based organic polymer thin film is formed on a substrate, and this is rubbed to give alignment control ability. Organic alignment films have been put into practical use.
[0007]
Also known is a method (photo-alignment) for imparting alignment control ability by irradiating light to an alignment film of a polyimide-based organic polymer thin film formed on a substrate (US Pat. No. 4,974,941 specification, JP-A-5-34699, JP-A-6-281937, JP-A-7-247319).
[0008]
However, there is no example in which these conventional photo-alignment techniques are applied to the horizontal electric field method, and no mention is made of the great effect obtained by applying the photo-alignment technique to the horizontal electric field method. Further, no consideration is given to the physical properties of the photo-alignment film material required when the photo-alignment film material is applied to a liquid crystal display device.
[0009]
[Problems to be solved by the invention]
In a conventional liquid crystal display device, a practical means for aligning the molecules of the liquid crystal composition constituting the liquid crystal layer on the substrate surface (giving liquid crystal alignment control ability to the alignment film) is a rubbing method. However, the process of imparting liquid crystal alignment control ability by rubbing (hereinafter also simply referred to as alignment treatment or rubbing treatment) is a method in which a cloth is brought into direct contact with the alignment film surface. The surface may be contaminated.
[0010]
Static electricity generated in the alignment film may destroy an active element (switching element, generally a thin film transistor (TFT)) or change its switching characteristics. When contamination occurs on the surface of the alignment film, the frequency dependence of the local threshold voltage becomes non-uniform, the voltage holding ratio decreases, the pretilt angle changes, and the liquid crystal alignment changes.
[0011]
Furthermore, as the substrate, which is a transparent glass plate, generally becomes larger, it is difficult to control the load during the rubbing process on the entire substrate, so scratches and unevenness due to the rubbing process may occur on the large substrate. is there. In addition, fine shavings are generated from the thin film rubbed with the cloth, which becomes a major source of dust generation in the clean room where the liquid crystal display device is manufactured, which is the main factor that reduces the yield of other manufacturing processes. It also has the big problem of becoming.
[0012]
Further, the substrate surface has uneven steps due to the structure of the electrodes and active elements, and in the rubbing process, there are portions where the rubbing is insufficient or portions are not rubbed due to the steps. This causes light leakage in black display and causes a decrease in contrast. These problems become more pronounced as the substrate becomes larger.
[0013]
On the other hand, instead of such a contact type liquid crystal alignment treatment method, a so-called photo-alignment film is formed by applying a photo-alignment technique (photo-alignment method) that can achieve liquid crystal alignment without contact on the surface of the alignment film. It has been known. However, the following points are problems in applying the photo-alignment method to the alignment film in a practical liquid crystal display device. In other words, the liquid crystal display device obtained by the photo-alignment method has poor afterimage characteristics as compared with the liquid crystal display device obtained by the conventional rubbing method. In other words, when the display is switched after the display is continued for a certain period of time, the trace of the previous display becomes remarkable in the liquid crystal display device obtained by the photo-alignment method.
[0014]
The object of the present invention is to solve the above-mentioned problems in the prior art, particularly to improve the afterimage characteristics in a liquid crystal display device using an alignment film provided with liquid crystal alignment control ability by a photo-alignment method, and to have a wide viewing angle and display abnormality. An object of the present invention is to provide a liquid crystal display device that achieves both inconspicuous display uniformity.
[0015]
[Means for Solving the Problems]
In order to solve the above problems and achieve the above object, the present invention uses the following means. According to the research of the inventors of this application, a liquid crystal is aligned by irradiating polarized light to an alignment film made of polyimide or other organic polymer including a photochromic portion, and the viewing angle is reduced by applying it to a lateral electric field method. It was further improved, and it was found that the uniformity of display was greatly improved.
[0016]
When the polyimide alignment film is irradiated with light, the pretilt angle is almost zero, and it has been confirmed that the anchoring strength for constraining the alignment of the liquid crystal is weaker than that by the rubbing treatment. This is why viewing angle characteristics and display uniformity are significantly improved by combining a horizontal electric field method with a method of aligning liquid crystals by irradiating an alignment film, which is an organic polymer thin film, with polarized light.
[0017]
The polyimide alignment film here is a polyimide composed of a diamine component and an acid dianhydride, and includes a film having a photochromic site such as azobenzene, stilbene, or cinnamate. Specific examples of the acid dianhydride component include pyromellitic acid, methyl pyromellitic acid, dimethyl pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, p- (3,4-dicarboxyphenyl) ) Benzene, 2,3,3 ′, 4′-tetracarboxydiphenyl, 3,3 ′, 4,4′-tetracarboxydiphenyl ether, 2,3,3 ′, 4′-tetracarboxydiphenyl ether, 3,3 ′, 4,4′-tetracarboxybenzophenone, 2,3,3 ′, 4′-tetracarboxybenzophenone, 2,3,6,7-tetracarboxynaphthalene, 1,4,5,7-tetracarboxynaphthalene, 1,2 , 5,6-tetracarboxynaphthalene 3,3′4,4′-tetracarboxydiphenylmethane, 2,3,3 ′, 4′-tetracarboxydiphenylmethane, 2,2-bis (3,4-dicarboxyphenyl) propane, 3,3 ′, 4,4′-tetracarboxydiphenyl sulfone, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) phenyl ] Nonane, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) phenyl] decane, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) phenyl] tridecane, 2,2 -Bis [4- (3,4-dicarboxybenzoyloxy) phenyl] tetradecane, 2,2-bis [4- (3,4-dicarboxybenzoyloxy) phenyl] pentadecane, 1,1-bis [4- ( 3,4-dicarboxybenzoyloxy) phenyl] -2-methyloctane, 1,1-bis [4- (3,4-dicarboxybenzoyloxy) phenyl] -2 Ethyl pentadecane, 2,2-bis [3,5-dimethyl-4- (3,4-dicarboxybenzoyloxy) phenyl] dodecane, 2,2-bis [3,5-dimethyl-4- (3,4) Dicarboxybenzoyloxy) phenyl] decane, 2,2-bis [3,5-dimethyl-4- (3,4-dicarboxybenzoyloxy) phenyl] tridecane, 2,2-bis [3,5-dimethyl-4 -(3,4-dicarboxybenzoyloxy) phenyl] pentadecane. However, it is not limited to the above.
[0018]
Specific examples of the diamine component include p-phenylenediamine, m-phenylenediamine, diaminodiphenyl ether, diaminodiphenylmethane, 2,2-diaminodiphenylpropane, diaminodiphenylsulfone, diaminobenzophenone, 2,2-bis [ 4- (p-aminophenoxy) phenyl] ether, 2,2-bis [4- (p-aminophenoxy) phenyl] ketone, 2,2-bis [4- (p-aminophenoxy) phenyl] ester, 2,2-bis [4- (p-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (m-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (p-aminophenoxy) Phenyl] biphenyl, 2,2-bis [4- (p-aminophenoxy) phenyl] propane, 2,2 Bis [4- (p-aminophenoxy) phenyl] pentane, 2,2-bis [4- (p-aminophenoxy) phenyl] octane, 2,2-bis [4- (p-aminophenoxy) phenyl] tridecane, etc. There is. However, it is not limited to the above.
[0019]
Further, a silane coupling agent is added to the alignment film in order to improve the adhesion with the glass as the substrate, but it is reduced to 5% by weight or less. As the amino-based silane coupling agent to be added, γ- (N-β-aminoethyl) aminopropylmethyldimethoxysilane, γ- (N-β-aminoethyl) aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, There are γ-aminopropyltriethoxysilane, N-benzylaminopropyltrimethoxysilane and the like. However, it is not limited to the above.
[0020]
On the other hand, liquid crystal display devices are required to have good display characteristics. However, as described above, the afterimage characteristic that the previous image remains when the display is switched after the constant display is continued in the optical orientation is worse than the rubbing method. Thus, as a result of intensive studies, it was found that the afterimage characteristics equivalent to the rubbing method can be obtained even by the photo-alignment method by setting the film elastic modulus to about 5 GPa or more at 25 ° C.
[0021]
FIG. 1 is an explanatory diagram of the relationship between the film elastic modulus and the afterimage characteristics, where the horizontal axis represents the film elastic modulus (GPa) and the vertical axis represents the afterimage time (afterimage / min). FIG. 2 is an explanatory view of the afterimage evaluation result when the film elastic modulus is changed, and the horizontal axis indicates the film elastic modulus (GPa), and the vertical axis indicates the result of visual evaluation (sensitive inspection). . As shown in FIG. 1, it can be seen that as the film elastic modulus increases, the afterimage time decreases. As shown in FIG. 2, it can be seen that when the film elastic modulus is 5 GPa or more, the afterimage time becomes very short, the afterimage is not visually recognized, and the afterimage characteristic does not become a problem.
[0022]
The film elastic modulus herein is a physical property value of a film obtained by attaching a diamond tip to an AFM / STM (atomic force microscope / scanning tunneling microscope) head and applying indentation with a very small force. Specific examples of the measuring device include a triboscope (trade name) manufactured by Heidistron. The high elastic modulus corresponds to a strong restoring force when stress is applied, and it is considered that the high elastic alignment film undergoes stress deformation of the alignment film caused by the change in liquid crystal alignment deformed by the electric field in a short time.
[0023]
When the polyimide is irradiated with light, the pretilt angle of the liquid crystal alignment is small and almost equal to zero. Therefore, the pretilt angle can be easily made asymmetric between the upper and lower substrates by irradiating only one of the pair of substrates and performing photo-alignment treatment, and subjecting the other substrate to normal rubbing treatment to give a pretilt angle. Such asymmetry is effective in increasing the response speed of the liquid crystal.
[0024]
In addition, since the anchoring strength of the photo-alignment film is too small, local alignment abnormality occurs in the liquid crystal alignment when both substrates are subjected to photo-alignment treatment. Therefore, it is effective for improving the uniform alignment of the liquid crystal to perform the photo-alignment treatment on one substrate and the rubbing treatment on the other substrate.
[0025]
It is known that when polyimide is irradiated with light, charges are likely to accumulate on the irradiated surface. Therefore, a direct current component is easily accumulated in the liquid crystal panel, causing afterimages. A compound having a cyano group at the terminal is a substance that is relatively easy to attract impurities and effective in reducing specific resistance. Therefore, a compound having a cyano group is mixed in the liquid crystal, and the specific resistance of the liquid crystal is 10. ¹³ If the value is smaller than Ω · cm, the afterimage can be improved by compensating the charge in the liquid crystal.
[0026]
Furthermore, rubbing caused a region that was not rubbed due to uneven steps on the substrate surface, which caused a decrease in contrast. However, when photo-alignment processing was used for liquid crystal alignment, this was not the case and the step was 0.3 μm or more. no problem.
[0027]
Based on the above facts, the present invention is characterized in that it is configured as described in the following (1) to (5). That is,
(1) The first alignment film is formed directly on the upper layer of the scanning signal electrode, the video signal electrode, the pixel electrode, the active element, the electrode constituting the display pixel, and the active element constituting the display pixel or via the insulating layer. One substrate formed, a second alignment film formed so as to face the first alignment film, the other substrate disposed with a predetermined gap from the one substrate, the one substrate and the other substrate A liquid crystal layer composed of a liquid crystal composition sandwiched between first and second alignment films formed on the substrate, and at least the surface of the one substrate opposite to the liquid crystal layer depending on the alignment state of the liquid crystal layer A liquid crystal panel comprising polarizing means for changing optical characteristics, wherein each electrode formed on the one substrate applies an electric field substantially parallel to the substrate surface to the liquid crystal layer;
Control means connected to each electrode formed on the one substrate constituting the liquid crystal panel and capable of arbitrarily controlling an electric field applied to the liquid crystal layer according to a display pattern, the first alignment At least one of the film and the second alignment film was a photo-alignment film having a film elastic modulus of about 5 GPa or more at 25 ° C. and having a liquid crystal alignment control ability by irradiation with linearly polarized light.
[0028]
With this configuration, the afterimage characteristics of the liquid crystal display device using the alignment film provided with the liquid crystal alignment control ability by the photo-alignment method are improved, and the liquid crystal display device achieves both a wide viewing angle and display uniformity in which display abnormality is not noticeable. Is obtained.
[0029]
(2) A plurality of color filters are provided below the alignment film on the other substrate in (1).
[0030]
(3) The alignment film in (1) or (2) is a polyimide organic polymer film.
[0031]
(4) Only the first alignment film formed on the one substrate in (1) to (3) is a photo-alignment film, and the second alignment film formed on the other substrate is subjected to liquid crystal alignment control by rubbing treatment. Added the ability.
[0032]
(5) 1% or more of a compound having a cyano group was included in the liquid crystal composition constituting the liquid crystal layer in (1) to (4).
[0033]
With the configurations (2) to (5) above, the afterimage characteristics in the liquid crystal display device using the alignment film provided with the liquid crystal alignment control ability by the photo-alignment method are specifically improved, and the wide viewing angle and the display abnormality are not conspicuous. A liquid crystal display device having both display uniformity can be obtained.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to examples.
[0035]
[Example 1]
FIG. 3 is a conceptual diagram of the whole of a horizontal electric field type active matrix liquid crystal display device to which the present invention is applied, and FIG. 4 is a cross-sectional view illustrating a configuration example of one pixel of the horizontal electric field type active matrix liquid crystal display device. 5 is a conceptual diagram of a drive circuit section of the switching element, and FIG. 6 is a display principle diagram of a lateral electric field type active matrix liquid crystal display device.
[0036]
In FIG. 3, 8a is a lower polarizing plate, 8b is an upper polarizing plate, 14 is a thin film transistor (TFT) as a switching element, 18 is a scanning electrode driving circuit, 19 is a signal electrode driving circuit, 20 is a common electrode driving circuit, 22a, 22b represents a black matrix, and 23 represents a color filter. The substrate is not shown.
[0037]
This liquid crystal display device is a so-called lateral electric field type (IPS), and various electrodes for pixel selection and a TFT 14 are formed on one substrate (generally also referred to as a lower substrate, a TFT substrate or an active substrate), and the other substrate ( Only the color filter 23 partitioned by the black matrices 22a and 22b is formed on the upper substrate (which is also referred to as a color filter substrate having a color filter as in this embodiment), and does not have electrodes for pixel selection. Then, an electric field in a direction substantially parallel to the substrate plane is formed on the liquid crystal layer sandwiched between both substrates, and lighting / non-lighting is controlled by changing the orientation direction of the liquid crystal molecules forming the liquid crystal layer within the substrate plane. To do.
[0038]
3 and 4, one and the other substrates (7a and 7b in FIG. 4) are made of a transparent glass plate having a polished surface with a thickness of 0.7 mm, a size of 230 × 370 mm, and a display area of 203 × 270 mm. Use. A thin film transistor was formed on one of these substrates, and a silicon nitride film as an insulating film was formed thereon. Insulating films 2 and 26 were formed on the upper layer so as to cover the pixel electrode 4 and the common electrode 1 which are electrodes for driving the liquid crystal, and an alignment film 5a was further coated thereon. The pixel electrode 4 and the common electrode 1 were made of chromium, which is a metal.
[0039]
In FIG. 4, 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 constituting a liquid crystal layer, and 7a is Lower substrate (one substrate), 7b is an upper substrate (the other 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, Reference numeral 26 denotes an insulating film (PSV).
[0040]
On one substrate, the lower substrate 7a, a thin film transistor 14 (see FIG. 3), a video signal electrode 3 which is an electrode for driving a liquid crystal (liquid crystal molecule) 6 and a silicon nitride film (SiN) whose common electrode 1 is an insulating film. ) 2 and an insulating film 26 is formed to cover these electrodes. The upper substrate 7b, which is the other substrate, is provided with a color filter 23 partitioned by a black matrix 22 (22a, 22b), and the lower alignment film 5a formed on the opposing surfaces of both the substrates 7a and 7b and the upper alignment film. A liquid crystal layer composed of liquid crystal molecules 6 is sandwiched between the film 5b. 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 that are in direct contact with the alignment film or the liquid crystal layer use ITO (Indium Tin Oxide) in consideration of metal corrosion.
[0041]
In FIG. 5, 1 is a common electrode, 3 is a video signal electrode, 17 is a control circuit, 18 is a scanning electrode drive circuit, 19 is a signal electrode drive circuit, 20 is a common electrode drive circuit, and 21 is a liquid crystal panel. TFT is a switching element, C _LC Is the capacitive component of liquid crystal, C _S Indicates a storage capacity.
[0042]
The TFT for switching each pixel of the liquid crystal panel 21 is selectively turned on / off by the scanning electrode driving circuit 18, the signal electrode driving circuit 19 and the common electrode driving circuit 20. This on / off is controlled by the control circuit 17.
[0043]
The liquid crystal layer in which the orientation direction of molecules is changed by turning on / off the TFT is the initial orientation direction in the orientation state (liquid crystal orientation control ability) of the lower and upper orientation films 5a and 5b formed on both substrates 7a and 7b. Is set.
[0044]
In this example, polyimide was adopted as the alignment film shown in FIG. 4, and the surface of the polyimide film was irradiated with polarized UV light in order to impart alignment control ability to the surface. A KrF excimer laser (wavelength 248 nm) is used as the polarized UV light source, and the irradiation energy is 5 mJ / cm. ² Irradiated with 76 shots. The lower substrate 7a on which the alignment film is formed is fed at a constant speed, and the feeding speed is set so that the irradiation surface is uniformly irradiated with 76 shots of polarized UV light.
[0045]
Further, polyimide was applied to the outermost surface of the upper substrate 7b, which is a color filter substrate, and irradiated with polarized UV in the same manner as described above. The liquid crystal molecules 6 are aligned in a direction perpendicular to the polarized light.
[0046]
In FIG. 6, (a) shows the applied voltage (V _OFF ) Is a cross-sectional view in the dark state, and (b) is an applied voltage (V _ON ) Is a cross-sectional view of the dark state in the bright state, (c) is the applied voltage (V _OFF ) In the dark state in the dark state, (d) is the applied voltage (V _ON ) Is a plan view in a bright state.
[0047]
In the dark state shown in FIGS. 6A and 6C, since there is no electric field between the common electrode 1 and the pixel electrode 4, the liquid crystal molecules 6 are in the initial alignment state and installed on the lower surface of the lower substrate 7a. The illumination light from the backlight (not shown) does not reach the upper substrate 7b side.
[0048]
On the other hand, in the bright state shown in FIGS. 6B and 6D, an electric field 9 exists between the common electrode 1 and the pixel electrode 4, and the alignment direction of the liquid crystal molecules 6 is rotated by the electric field 9 and the lower substrate. Illumination light from a backlight (not shown) installed on the lower surface of 7a reaches the upper substrate 7b side.
[0049]
As described above, in the horizontal electric field type liquid crystal display device, the liquid crystal molecules 6 are rotated in a plane parallel to the plane of the substrate, that is, in the horizontal direction to form an image by switching between a bright state and a dark state.
[0050]
7A and 7B are explanatory views of an electrode structure in the first embodiment of the active matrix type liquid crystal display device according to the present invention. FIG. 7A is a plan view seen from a direction perpendicular to the substrate, and FIG. A sectional view taken along line A, (c) is a sectional view taken along line BB of (a).
[0051]
The thin film transistor (TFT) 14 includes a pixel electrode (source electrode) 4, a video signal electrode (drain electrode) 3, a scanning electrode (gate electrode) 12, and amorphous silicon (a-Si) 13. The scanning electrode 12 and part 1a of the common electrode, and the video signal electrode 3 and part 4a of the pixel electrode were configured 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 through a through hole, and the pixel electrode is also contacted with the through hole in the transistor portion. Thus, a part 4b of the pixel electrode was formed. The part 1b of the common electrode and the part 4b of the pixel electrode were formed using ITO.
[0052]
The capacitor element 16 forming the storage capacitor is formed in a structure in which the insulating protective film (gate insulating film) 2 is sandwiched between the pixel electrode 4 and the common electrode 1 in a region where the two common electrodes 1 are coupled. The pixel electrode is disposed 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), and 300 μm in the vertical direction (that is, between the scanning wiring electrodes). The electrode width is set so that the scanning electrode, signal electrode, and common electrode wiring portion (a portion extending in parallel to the scanning wiring electrode (horizontal direction in FIG. 8 to be described later)) are widened. The defect is avoided. The widths are 10 μm, 8 μm, and 8 μm, respectively.
[0053]
On the other hand, the width of the pixel electrode formed independently for each pixel and the portion of the common electrode extending in the longitudinal direction of the signal wiring electrode were slightly narrowed to 5 μm and 6 μm, respectively. Narrowing the width of these electrodes increases the possibility of disconnection due to the inclusion of foreign matter or the like. In this case, however, a partial defect of one pixel is sufficient, and no line defect occurs. The signal electrode 3 and the common electrode 1 were provided at an interval of 2 μm via the insulating film 25. The number of pixels was set to 640 × 3 × 480 by 640 × 3 (R, G, B) signal wiring electrodes and 480 wiring electrodes.
[0054]
FIG. 8 is a structural explanatory view of a color filter substrate with a black matrix (BM), where (a) is a plan view viewed from a direction perpendicular to the substrate surface, and (b) is a line AA ′ in (a). (C) is sectional drawing which followed the BB 'line | wire of (a).
[0055]
As the black matrix 22, a material in which carbon and an organic pigment are mixed was used. The arrangement of the black matrix 22 with respect to the electrode substrate is indicated by a broken line in FIG.
[0056]
After forming the black matrix 22, R, G, and B pigments were dispersed in the photosensitive resin, and each color filter 23 was formed by coating, patterning exposure, and development, respectively. Then, an epoxy polymer thin film was applied and formed as an overcoat film 24 on the color filter 23.
[0057]
The active matrix liquid crystal display device thus obtained can obtain an image display with a wide viewing angle and good display uniformity.
[0058]
In this example, polyimide was used as the alignment film, and the surface of the polyimide alignment film was irradiated with polarized UV to align the liquid crystal on the surface. A KrF excimer laser 248 nm was used as a light source. At this time, the irradiation energy is 7.5 mJ / cm. ² Irradiated with 300 shots. The substrate can be scanned at a constant speed, and the feed speed of the substrate was set so that the irradiated surface was irradiated uniformly with 300 shots of polarized UV light.
[0059]
FIG. 9 is a conceptual diagram of a polarized light irradiation method and a polarized light irradiation apparatus for aligning liquid crystals in this embodiment. FIGS. 10A and 10B are explanatory views of the polarization separating means in FIG. 9, wherein FIG. 10A is a perspective view and FIG. 10B is a side view.
[0060]
9 and 10, 100 is a light source suitable for a laser, 101 is an attenuator, 102 relay optical system (102a is a first mirror, 102c is a second mirror, 102e is a third mirror, 102b is a first lens system, 102d is the second lens system), 103 is the homogenizer, 104 is the fourth mirror, 105 is the slit, 106 is the imaging lens system, 107 is the holder, 108 is the polarization separating means, 109 is the scanning means, and 110 is the irradiation surface. .
[0061]
The light emitted from the light source 100, which is a KrF excimer laser, reaches the slit 105 after the light intensity of the cross section is made uniform through the attenuator 101, the relay optical system 102, the homogenizer 103, and the fourth mirror.
[0062]
The slit 105 is a rectangular opening, and a cross section of light passing through the slit 105 is shaped into a rectangular beam pattern and introduced into the imaging lens system 106. The light emitted from the imaging lens system 106 is also rectangular beam pattern BP. And enters the polarization separation means 108.
[0063]
The polarization separation means 108 is formed by forming a multilayer film on a rectangular quartz plate having a long side of 25 cm and a short side of 3 cm, and its polarization axis is the incident light beam (the beam pattern BP emitted from the imaging lens system 106). Light) P wave polarization axis AX _P The holder 107 is arranged so that the long side of the quartz plate is parallel to the substrate which is the irradiation surface 110 in a state tilted at a Brewster angle θ with respect to the optical axis of the incident light beam. Is held by. The shape of the quartz plate is not limited to a rectangle.
[0064]
As shown in FIG. 10, by arranging the polarization separating means 108 at the Brewster angle θ, the S wave component B (polarization axis AX) included in the incident light beam A of the beam pattern BP. _S ) Is selectively reflected by the polarization separator 108.
[0065]
Therefore, the light beam that passes through the polarization separation means 107 and reaches the irradiation surface 110 is polarized with the polarization axis AX. _P Only the P wave component with
[0066]
The irradiation surface 110 is supported by a scanning stage 109 (FIG. 9) that can move in two dimensions perpendicular to the optical axis of the irradiation light, and the light beam pattern BP is moved by moving the scanning stage 109 in the directions of arrows X and Y. Irradiation surface 110 can be irradiated two-dimensionally in a wider range than the size of.
[0067]
When a polarization separation plate (hereinafter also described by reference numeral 108) having a multilayer film formed on the surface of a rectangular quartz plate is used as the polarization separation means 108, the polarization axis AX of the P wave _P In principle, either the short side coincides with the surface parallel to the short side (the short side and the irradiated surface are parallel) or the long side coincides (the long side and the irradiated surface are parallel). P wave polarization axis AX _P It is possible to efficiently irradiate the irradiation surface 110 having a large area.
[0068]
The liquid crystal molecules constituting the liquid crystal layer are aligned in a direction perpendicular to the polarized light. In this example, the orientation axes of liquid crystal molecules on the upper and lower interfaces are almost parallel to each other, and the angle between the applied electric field direction is 75 degrees (see FIG. 11).
[0069]
FIG. 11 is an explanatory view of the definition of the orientation direction of the orientation film and the transmission axis direction of the polarizing plate installed on the outer surface of the substrate, where 9 is the electric field direction, 10 is the orientation direction of the orientation film, and 11 is the polarization transmission axis direction. is there.
[0070]
In this embodiment, the liquid crystal molecules are aligned in a direction perpendicular to the polarized light. Easy axis of liquid crystal alignment on the interface with the upper and lower alignment films (upper alignment axis of the upper alignment film: φ _LC1 , Easy orientation axis of lower alignment film: φ _LC2 ) Are substantially parallel to each other and the angle between the applied electric field direction is 75 degrees (φ _LC1 = Φ _LC2 = 75 °).
[0071]
A nematic liquid crystal composition having a positive dielectric anisotropy Δε of 7.3 and a refractive index anisotropy Δn of 0.074 (wavelength 589 nm, 20 ° C.) is sandwiched between these two substrates. A liquid crystal layer was formed.
[0072]
The gap between two substrates (one substrate: TFT substrate and the other substrate: color filter substrate), that is, the cell gap d is set by dispersing spherical polymer beads between the substrates, and is 4.0 μm when liquid crystal is sealed. It was. Therefore, Δn · d is 0.296 μm.
[0073]
The liquid crystal panel is sandwiched between two polarizing plates (for example, G1220DU manufactured by Nitto Denko Corporation), and the polarizing transmission axis φ of the polarizing plate _P The polarization transmission axis of one polarizing plate: φ _p1 Is set to 75 °, and the polarization transmission axis of the other polarizing plate: φ _p1 Orthogonal to this, that is, φ _p2 = −15 °. In this embodiment, the low voltage (V _OFF ) Dark state, high voltage (V _ON ) Adopted normally closed characteristics that take a bright state.
[0074]
The chemical structure of the polyimide used is a polyimide composed of pyromellitic dianhydride and 2,2-bis [4- (p-aminophenoxy) phenyl] propane, and has a film thickness of about 1300 mm and a film elastic modulus of 6. 0.7 GPa. Here, the above-mentioned triboscope (trade name) manufactured by Heidistron was used for the film elastic modulus.
[0075]
The active matrix liquid crystal display device thus obtained had no afterimage after displaying the same image for 30 minutes. In addition, a wide viewing angle at which gradation inversion does not occur while maintaining a contrast of 10 or more at 80 degrees or more in the vertical and horizontal directions, and display uniformity was also good.
[0076]
[Example 2]
This embodiment has the same configuration as that of the first embodiment except for the following. In this example, polyimide was used as the alignment film, and the surface of the polyimide alignment film was irradiated with polarized UV in order to align the liquid crystal on the surface. A KrF excimer laser 248 nm was used as a light source. At this time, the irradiation energy is 7.5 mJ / cm. ² For 700 shots. The substrate can be scanned at a constant speed, and the feed speed of the substrate was set so that the irradiated surface was irradiated uniformly with 700 polarized UV rays.
[0077]
The chemical structure of the polyimide used was a polyimide composed of pyromellitic dianhydride and diaminodiphenyl ether, and had a film thickness of about 800 mm and a film elastic modulus of 10.3 GPa. Here, the membrane elasticity was the same as that of the above-mentioned example using a triboscope (trade name) manufactured by Heidistron.
[0078]
The active matrix type liquid crystal display device thus obtained had no afterimage after the same image was displayed for 30 minutes. In addition, a wide viewing angle at which gradation inversion does not occur while maintaining a contrast of 10 or more at 80 degrees or more in the vertical and horizontal directions, and display uniformity was also good.
[0079]
Example 3
This embodiment has the same configuration as that of the first embodiment except for the following. In this example, polyimide was used as the alignment film, and the surface of the polyimide alignment film was irradiated with polarized UV in order to align the liquid crystal on the surface. A KrF excimer laser 248 nm was used as a light source. At this time, the irradiation energy is 7.5 mJ / cm. ² Irradiated with 300 shots. The substrate can be scanned at a constant speed, and the feed speed of the substrate was set so that the irradiated surface was irradiated uniformly with 300 shots of polarized UV light.
[0080]
Also, polyimide was applied to the outermost surface of the color filter substrate with a black matrix, which was the other substrate (the other substrate), and rubbed. Note that the liquid crystal molecules are aligned in a direction perpendicular to the polarized light. In this embodiment, the easy axis directions of the alignment molecules of the liquid crystal on the upper and lower interfaces are substantially parallel to each other, and the angle formed between the applied electric field direction in the pixel is 75 degrees (φLC ₁ = ΦLC ₂ = 75 °).
[0081]
The chemical structure of the polyimide used was a polyimide composed of pyromellitic dianhydride and diaminodiphenyl ether, and had a film thickness of about 800 mm and a film elastic modulus of 10.3 GPa. Again, the membrane elastic modulus was a triboscope (trade name) manufactured by Heidistron.
[0082]
The active matrix type liquid crystal display device thus obtained had no afterimage after the same image was displayed for 30 minutes. In addition, a wide viewing angle at which gradation inversion does not occur while maintaining a contrast of 10 or more at 80 degrees or more in the vertical and horizontal directions, and display uniformity was also good. There were no alignment defect neil walls due to the low anchoring strength. In addition, the response time (the sum of luminance changes from 0% to 90% and 100% to 10% when the voltage is on and off) is 32 ms.
[0083]
Example 4
This embodiment has the same configuration as that of the first embodiment except for the following. To the liquid crystal, 1% by weight of 1- (4-cyanophenyl) -4-propylcyclohexane was added to MLC-6252 (trade name) manufactured by Merck Japan, which is composed of only a compound having a fluoro group at the terminal. Specific resistance before encapsulation is 4 × 10 ¹² A mixture of Ω · cm 2 cyano compounds was enclosed. The specific resistance of the liquid crystal remaining in the liquid crystal dish after sealing is 2 × 10 ¹¹ It was Ω · cm.
[0084]
The chemical structure of the polyimide used was a polyimide composed of pyromellitic dianhydride and diaminodiphenyl ether, and had a film thickness of about 800 mm and a film elastic modulus of 10.3 GPa. Here, the membrane elastic modulus was a triboscope (trade name) manufactured by Heidistron.
[0085]
The active matrix type liquid crystal display device thus obtained had no afterimage after the same image was displayed for 30 minutes. In addition, a wide viewing angle at which gradation inversion does not occur while maintaining a contrast of 10 or more at 80 degrees or more in the vertical and horizontal directions, and display uniformity was also good. In addition, no afterimage was observed.
[0086]
FIG. 12 is a perspective view of a notebook personal computer which is an example of an information device in which the liquid crystal display device according to the present invention is mounted. The notebook computer (portable personal computer) includes a keyboard unit (main body unit) and a display unit connected to the keyboard unit by a hinge. The keyboard unit accommodates a signal generation function such as a keyboard, a host (host computer), and a CPU, and the display unit includes a liquid crystal panel PNL, around which drive circuit boards PCB1 and PCB2, a control chip TCON, and a CPU A PCB 3 on which a connector CT for connecting signals and the like are mounted, an inverter power supply board as a backlight power supply, and the like are mounted. The liquid crystal panel PNL has the alignment film described in each of the above embodiments.
[0087]
Various circuit boards PCB1, PCB2, PCB3, an inverter power supply board, and a backlight are integrated with the liquid crystal panel PNL and mounted as a liquid crystal display module MDL.
[0088]
【The invention's effect】
As described above, according to the present invention, the afterimage characteristics are improved by using the alignment film imparted with the ability to control the alignment of liquid crystals by irradiating polarized light, and the display is uniform with a wide viewing angle and display anomaly not noticeable. Thus, an active matrix liquid crystal display device having compatible properties can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a relationship between film elastic modulus and afterimage characteristics.
FIG. 2 is an explanatory diagram of an afterimage evaluation result when the film elastic modulus is changed.
FIG. 3 is an overall conceptual diagram of a horizontal electric field type active matrix liquid crystal display device to which the present invention is applied.
FIG. 4 is a cross-sectional view illustrating a configuration example of one pixel of a horizontal electric field type active matrix liquid crystal display device.
FIG. 5 is a conceptual diagram of a drive circuit unit of a switching element.
FIG. 6 is a display principle diagram of a horizontal electric field type active matrix liquid crystal display device.
FIG. 7 is an explanatory diagram of an electrode structure in the first embodiment of the active matrix liquid crystal display device according to the present invention;
FIG. 8 is an explanatory diagram of the structure of a color filter substrate with a black matrix.
FIG. 9 is a conceptual diagram of a polarized light irradiation method and a polarized light irradiation device for aligning liquid crystals in an embodiment of the present invention.
10 is an explanatory diagram of a polarized light separating means portion in FIG. 9. FIG.
FIG. 11 is an explanatory diagram of the definition of the alignment direction of the alignment film and the direction of the transmission axis of the polarizing plate placed on the outer surface of the substrate.
FIG. 12 is a perspective view of a notebook personal computer which is an example of an information device on which the liquid crystal display device according to the present invention is mounted.
[Explanation of symbols]
1 (1a, 1b) Common electrode (common electrode)
2 Gate insulation film
3 Video signal electrode (drain electrode)
4 (4a, 4b) Pixel electrode (source electrode)
5 (5a, 5b) Alignment film
6 Liquid crystal molecules
7 (7a, 7b) substrate
8 (8a, 8b) Polarizing plate
9 Electric field
10 Rubbing direction
11 Polarizing plate transmission axis direction
12 Scanning electrodes
13 a-silicon
14 Thin film transistor
16 Storage capacity
17 Control circuit
18 Scan electrode driving circuit
19 Signal electrode drive circuit
20 Common electrode drive circuit
21 LCD panel
22 (22a, 22b) Black matrix
23 Color filter
24 Overcoat film
25 Insulating film
26 Insulating layer.

Claims (4)

One of a scanning signal electrode, a video signal electrode, a pixel electrode, an active element constituting the display pixel, each electrode constituting the display pixel, and a first alignment film formed directly on the active element or via an insulating layer A second alignment film is formed so as to face the first alignment film, the other substrate is disposed with a predetermined gap from the one substrate, and the one substrate and the other substrate are formed. A liquid crystal layer composed of a liquid crystal composition sandwiched between the first and second alignment films, and at least the surface of the other substrate opposite to the liquid crystal layer has optical characteristics depending on the alignment state of the liquid crystal layer. A transverse electric field type liquid crystal panel having polarization means to change;
A liquid crystal display device comprising: control means connected to each electrode formed on the one substrate constituting the liquid crystal panel and capable of arbitrarily controlling an electric field applied to the liquid crystal layer according to a display pattern; ,
The first alignment film and the second alignment film are polyimides composed of a diamine component and an acid dianhydride,
Wherein the first alignment film and at least one of the second alignment layer has a film modulus of over approximately 5GPa at 25 ° C, light of wavelength 248nm polarized linearly by at least 380 mJ / cm ² irradiation the active matrix type liquid crystal display device, characterized in that the liquid crystal alignment controllability is photo-alignment film which is imparted. 2. The active matrix liquid crystal display device according to claim 1, further comprising a plurality of color filters under the alignment film on the other substrate. Only the first alignment film formed on the one substrate is a photo-alignment film, and the second alignment film formed on the other substrate is given a liquid crystal alignment control ability by rubbing treatment. 3. An active matrix liquid crystal display device according to claim 1 or 2. 4. The active matrix liquid crystal display device according to claim 1, wherein the liquid crystal composition constituting the liquid crystal layer contains 1% or more of a compound having a cyano group.

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