JP2012027486A - Liquid crystal display device - Google Patents

Abstract

Disclosed is a liquid crystal display device in which a desired value of retardation is provided by photo-alignment.
A liquid crystal display device has a liquid crystal layer LC between a pair of substrates SUB1 and SUB2, and is composed of two upper and lower alignment films ORI1 and ORI2 sandwiching the liquid crystal layer, and the alignment film has a thickness of 1 to 80 nm. The anchoring strength was 1.0 × 10 −3 Jm −2 or more.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal display device. The present invention is particularly suitable for a liquid crystal display device in which an alignment film is subjected to alignment treatment by light irradiation.

  In the manufacture of a liquid crystal display device, as a general process for the liquid crystal alignment control layer, a so-called rubbing process is performed in which a substrate is rubbed with a cloth on an organic film made of polyimide or the like. This rubbing treatment has problems such as contamination due to dust generation during rubbing, generation of electrostatic damage due to friction with respect to the transparent substrate on which the TFT type element is mounted, and reduction in manufacturing yield based on them. For this reason, a non-contact liquid crystal alignment technique is desired, and one of the methods is a photo-alignment process (Patent Document 1).

  The technique disclosed in Patent Document 1 irradiates the organic alignment film formed on the transparent substrate with polarized ultraviolet rays, and causes the molecules constituting the organic alignment film to undergo a chemical change in accordance with the polarization direction of the ultraviolet rays. In this technique, the orientation direction and the pretilt angle of the liquid crystal alignment are given to the organic alignment film. Therefore, according to this technique, contamination due to dust generation during rubbing and occurrence of electrostatic damage to the TFT-type element mounting substrate can be prevented, and a decrease in manufacturing yield can be prevented.

  In addition, in today's liquid crystal display devices, in order to widen the viewing angle of the liquid crystal display device or to compensate for the residual phase difference of the liquid crystal cell holding the liquid crystal layer between two pairs of substrates used in the liquid crystal display device, A layer having an azimuth retardation called a phase difference plate is placed between a liquid crystal cell holding a liquid crystal layer between two pairs of substrates and a polarizing plate of the liquid crystal cell, for example, from the light incident side, the polarizing plate, the phase difference plate, the liquid crystal cell, Lamination is performed in the order of a phase difference plate and a polarizing plate.

For example, in a TN type liquid crystal cell in which liquid crystal molecules are twist-aligned at approximately 90 °, as shown in Patent Document 2, it is said that color tone reversal can be suppressed even if the viewing angle is changed. In a normally white liquid crystal cell with liquid crystal molecules aligned in parallel, a retardation plate is used to compensate for the residual phase difference in the liquid crystal cell, as shown in Patent Document 3. Yes. Even in the so-called VA type liquid crystal cell in which the liquid crystal molecules are aligned perpendicularly to the plate of the liquid crystal cell, as described in Patent Document 4, by slightly rubbing with emphasis on viewing angle characteristics, The liquid crystal molecules may be slightly twisted while being tilted. In this case, since the liquid crystal molecules are not completely perpendicular to the liquid crystal cell, a residual phase difference is generated in the liquid crystal cell. However, this residual phase difference is not so large and the influence is smaller than in the case of homogeneous orientation, and it is difficult to obtain a phase plate with a small phase difference, so it is considered that the phase difference is not compensated.
[Prior art documents]
[Patent Literature]

JP 7-318942 A JP-A-6-167707 JP 2003-255347 A JP-A-11-2842 Japanese Patent Laid-Open No. 10-48627 Japanese Patent Laid-Open No. 10-55000 JP-A-8-136935

  Although the photo-alignment treatment has the above-described features, there has been no practical example to date. The cause is that when a liquid crystal display screen is displayed for a long time with the same image, and when the display of that image is stopped and, for example, a full-scale gray display is performed, the previous image is burned and displayed. This is because it is much easier to generate than the liquid crystal display device obtained by the processing, and it is judged that the performance of the display device is practically insufficient.

  This afterimage is characterized in that it can be seen in black display (initial alignment state with no voltage applied) in the normally closed display mode, and is generated due to the weak alignment regulating force of the alignment regulating layer. It is known that the anchoring strength of the liquid crystal display device obtained by the photo-alignment treatment is only 1/10 to 1/100 or less of the rubbing-processed liquid crystal display device. In order to achieve this, it is indispensable that an anchoring strength equivalent to that of rubbing can be obtained even with photo-alignment treatment.

  In addition, a retardation plate for widening the viewing angle of a liquid crystal display device or compensating for a residual phase difference of a liquid crystal cell having a liquid crystal layer held between two pairs of substrates used in the liquid crystal display device has a phase difference of 80 nm. In general, it is difficult to obtain a phase plate having a small phase difference as described below, resulting in a high-cost liquid crystal display device. In addition, as described in Patent Document 5 and the like, there is a technology for forming a retardation plate inside a liquid crystal cell using a UV curable liquid crystal. In order to form this phase plate, a UV curable liquid crystal cell is used. Since the complicated process of removing the counter substrate after the liquid crystal layer is cured is added, the finished liquid crystal display device is still expensive.

  Accordingly, a first object of the present invention is to provide a highly reliable liquid crystal display device and a method for manufacturing the same, in which the occurrence of afterimages is suppressed in a liquid crystal display device in which an alignment film is aligned by photo-alignment treatment. A second object is to provide a liquid crystal display device and a method for manufacturing the same capable of producing a small retardation layer having a retardation of 80 nm or less at a low cost.

In order to achieve the above object, the present invention focuses on the birefringence anisotropy of the alignment film in order to increase the anchoring strength of the liquid crystal display device in which the alignment film is aligned by photo-alignment treatment, and the azimuth retardation of the alignment film. It was decided to improve the afterimage characteristics by the improvement. The liquid crystal display device of the present invention is, in the first invention, a liquid crystal display device having an alignment film aligned by light irradiation, the alignment film having an azimuth angle retardation of 1.0 nm or more, and anchoring. The strength is 1.0 × 10 ⁻³ Jm ⁻² or more.

In the second invention, a liquid crystal display device having an alignment film, the alignment film has an azimuth retardation value of 1.0 nm or more and an anchoring strength of 1.0 × 10 ⁻³ Jm ⁻² or more. That's it. In the liquid crystal display device having such a configuration, a liquid crystal display device having a low afterimage level can be obtained.

This liquid crystal display device has a liquid crystal layer between a pair of substrates, and this alignment film is composed of two upper and lower alignment films sandwiching the liquid crystal layer, and this alignment film is irradiated with light. That is, it is composed of an alignment film aligned by the above. This alignment film is configured by irradiating an integrated light amount of light of 9.0 J / cm ² or more. Such an alignment film is suitable for an IPS liquid crystal display device.

  In the third invention, the liquid crystal display device is characterized in that the alignment film or the film on the substrate has an azimuth retardation value of 1 to 80 nm.

  As described above, according to the first aspect of the present invention, unlike the prior art, it is possible to produce a liquid crystal display device in which an afterimage is not easily generated even by a photo-alignment process.

  Specifically, taking polyimide known as a general alignment film as an example, rubbing treatment is performed on an alignment film with a thickness of about 100 nm, and azimuth angle retardation is measured (residual phase difference of the substrate is measured). Not included), about 0.3 to 0.7 nm. A liquid crystal display device was prepared using this alignment-treated substrate and an afterimage evaluation was performed.

  Specifically, when a black and white checker pattern as shown in FIG. 8 is displayed for 2 hours, and when this display pattern is stopped and immediately the entire black display is performed, the black and white checker pattern disappears immediately. Here, the checker pattern in FIG. 8 is a pattern in which a black display as in (8-1) and a black display as in (8-2) are arranged.

On the other hand, when non-contact alignment (photo-alignment treatment) is performed, a liquid crystal display device is similarly prepared and an afterimage evaluation is performed using a substrate having a azimuth angle retardation of about 0.3 to 0.7 nm, which is similar to that of rubbing. As a result, an afterimage was easily generated. The anchoring strength of 1.0 × 10 ⁻³ Jm ⁻² or more is achieved for the first time when the value of the azimuth angle retardation is 1.0 nm or more at the same film thickness, and afterimage test is performed in the same manner as rubbing. The pattern disappeared.

  The reason why the required azimuth retardation is different depending on the alignment treatment is considered to be because the distribution in the depth direction of the azimuth retardation applied to the alignment film differs depending on the alignment treatment. That is, in the rubbing process, azimuth retardation is generated on the alignment film surface in order to rub the alignment film surface. On the other hand, in the photo-alignment treatment, the light imparting the orientation reaches the depth direction of the alignment film sufficiently while being absorbed by the alignment film.

  For this reason, it is considered that the azimuth angle retardation occurs over the entire cross section of the alignment film, and the azimuth angle retardation on the surface of the alignment film occupies only a part of the entire azimuth angle retardation. In particular, it is appropriate to consider that the afterimage due to the orientation as seen in the IPS system depends on the orientation of the alignment film surface. In the case of photo-alignment treatment, it is necessary to prevent the afterimage from being generated. The value of the correct azimuth angle retardation is larger than that in the rubbing process. As a result of intensive studies on the relationship between the azimuth angle retardation value and the afterimage, the inventors have found that an afterimage does not occur for the first time under the conditions shown in the first invention.

  In the second invention of the present invention, unlike the prior art, it is possible to produce a small retardation layer having a retardation of 80 nm or less at a low cost. Specifically, using an alignment film that increases the azimuth angle retardation by light irradiation at the same film thickness, adjusting the film thickness, irradiation light amount, and heating temperature at the time of irradiation, the phase difference becomes 80 nm or less. An arbitrary retardation layer can be created with high accuracy.

It is a schematic diagram explaining the cross-sectional structure of the liquid crystal panel which comprises the TN system liquid crystal display device explaining Examples 1-6, 12 of this invention. FIG. 2 is a diagram for explaining a shaft configuration of a liquid crystal panel constituting the TN mode liquid crystal display device shown in FIG. 1. It is a figure which shows the cross-sectional block diagram of the homogeneous type liquid crystal panel explaining Example 78 of this invention. It is the figure which showed the axial structure of the liquid crystal panel of the homogeneous orientation type | mold shown in FIG. 3 for demonstrating Example 7 of this invention. It is a cross-sectional block diagram of the liquid crystal panel of a vertical alignment system explaining Example 8 of this invention. It is explanatory drawing of the cross-sectional structure of the IPS type liquid crystal panel and its axial structure explaining Example 8 and 9 of this invention. It is explanatory drawing of the orientation film | membrane micro birefringence measurement system for measuring the retardation in Example 10 and 11 of this invention. It is a figure which shows a black-and-white checker pattern. It is a figure which shows the relationship between the integrated light quantity of the irradiation light at the time of alignment film formation, and an azimuth angle retardation. It is a figure which shows the relationship between the integrated light quantity of the irradiation light at the time of alignment film formation, and anchoring intensity | strength. It is a figure which shows the relationship between anchoring intensity | strength and an afterimage disappearance level. It is a figure which shows the relationship between an azimuth | direction angle retardation and an afterimage disappearance level. It is the table | surface which put together the measurement result of FIGS.

  The best mode for carrying out the invention will be described below with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention should not be construed as being limited to the description of the embodiment modes.

  FIG. 1 is an explanatory diagram of a cross-sectional structure of an IPS-type liquid crystal panel and a shaft configuration thereof for explaining the first embodiment of the present invention. FIG. 1A is an explanatory diagram of a cross-sectional structure of a liquid crystal panel constituting an IPS type liquid crystal display device. A liquid crystal layer LC is held between substrates SUB1 and SUB2, and a color is formed on the main surface of one substrate SUB2. An organic film such as a filter CF is disposed, and an alignment film ORI2 is disposed on the color filter CF. Further, the pixel electrode PX and the counter electrode CT are disposed on the main surface of the substrate SUB1, and the alignment film ORI1 is disposed thereon.

  FIG. 1B is an explanatory diagram of the shaft configuration of the IPS liquid crystal panel shown in FIG. In addition, (alpha) in FIG.1 (b) shows the arbitrary angles of 0-360 degrees. Furthermore, the direction of the axis indicates the direction of the azimuth when the display panel is viewed from the front of the display side. The pair of polarizing plates laminated on the outer surface of the liquid crystal panel in FIG. 2, that is, the upper polarizing plate POL2 and the lower polarizing plate POL1, have an electric field applied to the liquid crystal layer compared to the transmittance when the electric field is applied to the liquid crystal layer LC. It is arranged so that the transmittance is low when not. For example, the upper polarizing plate POL2 and the lower polarizing plate POL1 are arranged via a liquid crystal panel so that their polarization axes are orthogonal to each other (so-called crossed Nicols arrangement).

  The axial directions of the alignment films ORI2 and ORL1 provided on the upper side and the lower side of the liquid crystal panel are set so as to form an angle parallel (that is, 0 °) with the polarization axis of the polarizing plate on the same substrate side. The liquid crystal molecules are arranged along the axial direction of the alignment film. At this time, the product Δnd (azimuth angle retardation) of the gap d of the liquid crystal panel of the liquid crystal layer and the refractive index anisotropy Δn is set in the range of 300 to 400 nm (measurement wavelength 589 nm).

  With the above configuration, when no voltage is applied, the azimuth retardation of the liquid crystal layer when viewed from the normal direction of the substrate is minimized, and black is displayed by the upper polarizing plate and the lower polarizing plate arranged in the crossed Nicols state. .

  When a sufficiently high voltage is applied to the liquid crystal layer, the liquid crystal molecules having positive dielectric anisotropy are inclined in the direction of the electric field formed between the electrodes, and the substrate method is formed by forming an angle other than 0 ° with the polarizing plate. When viewed from the line direction, the light of the lower polarizing plate POL1 arranged in the crossed Nicol state by the azimuth angle retardation value of the liquid crystal layer is transmitted through the upper polarizing plate POL2, and white is displayed.

  The manufacturing method of the organic film such as the color filter CF on the substrate SUB2 and the manufacturing method of the pixel electrode PX and the counter electrode CT of the substrate SUB1 can be manufactured by, for example, the method of Patent Document 6. A 6% N-methylpyrrolidone solution of polyamic acid or polyimide was printed on these substrates and heat-treated at 230 ° C. for 2 hours to form an alignment film layer ORI2 or ORI1 having a thickness of about 100 nm. This was irradiated with polarized light to give azimuth angle retardation by photo-alignment.

  More preferably, the material used is a photodegradable photo-alignable polyimide (for example, molecular weight 4000-100000), and the diamine portion is BAPP; 2,2-bis {4- (paraaminophenoxy) phenyl} propane, acid anhydride Is preferably CBDA; 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

  For example, an optical system having the configuration shown in FIG. 2 of Patent Document 7 can be used as the polarization irradiation apparatus for performing photo-alignment. In this embodiment, a high-pressure mercury lamp (HgHP) is used as the polarization source, and the emitted light is converted into linearly polarized light having a predetermined polarization direction by a polarization separator, and this polarized light is irradiated to the alignment film on the substrate through a shutter. .

In this example, the irradiation energy of the polarized irradiation system used was about 15 mW / cm ² in terms of a wavelength of 254 nm, and this linearly polarized light was irradiated in the range of the accumulated light amount of 0 to 18 J / cm ² . . At the time of irradiation, the substrate was placed on a hot plate that can be heated to 150 ° C., and irradiation was performed while heating.

  For example, a method for manufacturing a liquid crystal display device after the alignment treatment step, such as a method of holding the liquid crystal layer LC between the substrates SUB1 and SUB2, was manufactured by a normal method as described in, for example, [Patent Document 6].

  With respect to the liquid crystal display device manufactured by this method, the liquid crystal display device was disassembled, and the azimuth angle retardation and anchoring strength of the substrate SUB1 and the substrate SUB2 were measured. Since the azimuth angle retardation measured here is often on the order of 0.1 nm to several nm at most, a highly accurate optical measuring device is required.

  Here, first, a method for measuring the azimuth angle retardation will be described. FIG. 2 is an explanatory diagram of an alignment film microbirefringence measurement system for measuring the azimuth angle retardation in the present invention. The single wavelength light output from the light source passes through the incident-side polarizing plate, retardation plate, measurement sample, and transmission-side polarizing plate arranged substantially orthogonal to the optical axis, and is input to the photodetector. It has become.

  A commercially available spectrophotometer can be used for the light source and the photodetector. In this example, a double beam spectrophotometer U-3310 (wavelength slit width 2 nm) manufactured by Hitachi, Ltd. was used. Two measurement samples were collected from adjacent locations for the substrate SUB1 and the substrate SUB2. The microbirefringence optical system was placed on the sample side of the spectrophotometer, and only another measurement sample with the same specification was placed on the reference side.

  The polarizing plate needs to have a high degree of polarization, and the retardation plate preferably has a small wavelength dispersion. In this example, SEG1425DU manufactured by Nitto Denko Co., Ltd. was used as the polarizing plate, and Arton film (1/2 wavelength plate) manufactured by JSR Co., Ltd. as a retardation plate was bonded to Corning 7059 manufactured by Corning. The polarization axis of the incident-side polarizing plate and the change axis of the transmission-side polarizing plate are arranged so as to be substantially orthogonal (45 ° and 135 ° in FIG. 2), and the retardation plate has an incident-side polarizing axis and a transmission-side polarizing axis, respectively. Is arranged so as to have an angle of about 45 ° (0 ° in FIG. 2).

  The measurement sample is mounted on a stage that can be freely rotated in a plane perpendicular to the optical axis on the optical path (for example, a rotary stage manufactured by Sigma Kogyo Co., Ltd.), and is arranged so that the orientation axis is an angle of about 0 ° with respect to the phase difference plate Then, the spectral transmittance is measured in increments of 1 nm in the wavelength range of 400 nm to 700 nm, and further arranged so that the orientation axis is an angle of about 90 ° with respect to the retardation plate, and similarly 1 nm in the wavelength range of 400 nm to 700 nm. The spectral transmittance was measured in steps, and the wavelength at which the spectral transmittance was minimized was determined for each case.

  The wavelength when the spectral transmittance is minimized when arranged in the 0 ° direction with respect to the phase difference plate and the spectrum when arranged in the 90 ° direction with respect to the phase difference plate, measured by the above-described minute birefringence measurement system. Next, a method for obtaining the azimuth angle retardation of the measurement substrate using the wavelength at which the transmittance is minimized will be described.

  When a uniaxial thin film whose optical axis is parallel to the y-axis is sandwiched between two polarizing plates, the transmitted light intensity is expressed by equation (1).

I = I ₀ [cos2ψ−sin2φsin2 (φ−ψ) sin ² δ / 2] (1)
However, I ₀ is the incident light intensity, δ = 2πΔn · d / λ.

  As shown in FIG. 2, when the upper and lower polarization axes are orthogonal to each other and form an angle of 45 ° with the optical axis, ψ = 90 ° and φ = 45 °, and the equation (1) becomes (2) It is simplified like the formula.

I = I ₀ sin2 (πΔn · d / λ) (2)
The transmitted light intensity is minimized when the condition of equation (3) is satisfied.
πΔn · d / λ = m (m = 0, 1, 2,...) (3)
Using the relationship of the expression (3), Δnd can be obtained from the measurement of the minimum transmittance wavelength (λmin). Since the retardation plate used in the present invention has a cubic minimum (m = 3) in the vicinity of a wavelength of 550 nm, the expression (3) becomes the expression (4).

πΔn · d / λ = 3 (4)
The combined retardation of the retardation plates using two uniaxial films is given by the sum of both when the optical axes are laminated in parallel, and by the difference when the optical axes are laminated orthogonally. Here, Δnd of the retardation film is R, and azimuth retardation of the measurement substrate is r. Assuming that the minimum transmittance wavelength is λp when the optical axis of the phase difference plate is parallel to the orientation direction, and the minimum transmittance wavelength is λT when the optical axis of the retardation plate is orthogonal to the orientation direction, From the equation (4), the following equations (5) and (6) are obtained.

R + r = 3λp (5)
R−r = 3λT (6)
By subtracting equation (6) from equation (5), equation (7) is obtained.

r = 3 (λp−λT) / 2 (7)
That is, if λp and λT are measured using a spectrophotometer, the azimuth angle retardation r of the measurement substrate can be obtained from the equation (7). Since R and r have wavelength dependence, equation (7) is not strictly correct. However, in the measurement of a minute phase difference, the values of λp and λT are close to each other (about 50 nm at most), and an arton film having a small wavelength dispersion is used for the phase difference plate. The wavelength dependence of the azimuth angle retardation need not be substantially considered, and the expression (7) is applicable.

  Next, a method for measuring anchoring strength will be described.

  In order to measure the anchoring strength, a homogeneous alignment liquid crystal panel is manufactured for each of the substrate SUB1 and the substrate SUB2. In this example, a cell having a substrate size of 25 × 50 mm and a linear thermosetting sealing material containing glass fibers having a diameter of 10 μm on two long sides of the substrate was produced.

  The anchoring strength was measured for this cell by the following procedure.

  (1) About 2 mm of one side of the short side of the cell prepared in a container immersed in liquid crystal (Δn = 0.26) was immersed to enclose the liquid crystal. The sealed cell was aged in an oven (set temperature 90 ° C.) for 15 minutes, removed from the oven, allowed to stand at room temperature, and left overnight.

  (2) The optical twist angle (φ1) of the cell was measured using a polarizing microscope. The polarization microscope used has an optical system in which light from a light source is output to a visual observation and a photodetector (a photomultiplier manufactured by Hamamatsu Photonics) through a polarizer, a measurement sample, and an analyzer. The signal detected by the photodetector is digitally output by an A / D converter (manufactured by Hewlett Packard) and can be taken into a PC. The polarizer / analyzer can be driven by a stepping motor (minimum drive unit 0.005 °), and the angle at which the light intensity is minimized by rotating the polarizer by 0.01 ° is obtained by fourth-order fitting. Then, the polarizer angle (θ1) and the analyzer angle at which the transmittance is minimized by repeating the work of rotating the analyzer by 0.01 ° to obtain the angle at which the light intensity is minimized by the fourth-order fitting. (Θ2) was determined, and the optical twist angle (φ1) was calculated using equation (8).

φ = θ1 + 90−θ2 (8)
(3) The cell was fixed in a direction perpendicular to the central axis of the centrifuge, centrifuged (500 rpm) for 3 minutes, and high pressure air was blown into the cell to remove liquid crystal in the cell.

  (4) The liquid crystal mixture obtained by adjusting the concentration of the chiral material S-811 made by Merck so that the pitch is 46 μm in the liquid crystal of Δn = 0.26 used in (1) was immersed in a container, and One side of the short side was immersed for about 2 mm to enclose liquid crystal. The sealed cell was aged in an oven (set temperature 90 ° C.) for 15 minutes, removed from the oven, allowed to stand at room temperature, and left overnight.

  (5) The optical twist angle (φ2) was calculated using the same method as in (2).

  The anchoring strength (Aφ) was calculated by the equation (9) using the data of the optical twist angle (φ1) when no chiral was measured and the optical twist angle (φ2) when chiral was contained.

  Aφ = 2K2 (2πd / P-φ2) / dsin (φ2-φ1) (9)

  The measurement results of the azimuth angle retardation and anchoring strength of the substrates SUB1 and SUB2 prepared in this example are shown in FIGS. In these figures, the integrated light quantity is shown in the range of 0 to 15 J / cm2. FIG. 9 is a diagram illustrating the relationship between the integrated light amount of irradiation light and the azimuth retardation when forming an alignment film. FIG. 10 is a diagram illustrating a relationship between the integrated light amount of the irradiation light and the anchoring intensity when forming the alignment film.

  Next, an afterimage disappearance level check is performed in which the black and white checker pattern shown in FIG. 8 is displayed for 2 hours on the liquid crystal display device manufactured by the method of Example 1, and the entire black display is immediately performed after the display pattern is stopped. went. The results are shown in FIG. 11 and FIG.

  FIG. 11 is a diagram showing the relationship between the anchoring intensity and the afterimage disappearance level. FIG. 12 is a diagram showing the relationship between the azimuth angle retardation and the afterimage disappearance level. Each value of “afterimage disappearance level” indicates a level of afterimage disappearance in each azimuth angle retardation, 4: burn-in does not disappear, 3: disappears within 24 hours, 2: disappears within 2 hours, 1 means disappearing within 30 minutes, 0 means disappearing immediately.

  FIG. 13 shows a table summarizing the measurement results of FIGS. In FIG. 13, ILQ is an integrated light quantity, and LV is an afterimage disappearance level by a sensory test. As shown in these charts, it was confirmed that the azimuth angle retardation and anchoring strength of the alignment film formed by light irradiation have a significant effect on the afterimage disappearance. According to the measurement results this time, it was confirmed that the black-and-white checker pattern disappeared immediately when the orientation film was formed with an azimuth angle retardation of 1.0 or more and an anchoring strength of 0.99 Jm-2 or more.

  In the entire black display of this liquid crystal display device, streaky luminance unevenness did not occur. Further, when the alignment film surfaces of the substrate SUB1 and the substrate SUB2 of the liquid crystal display device were observed with a microscope, no scratches were confirmed on the surfaces.

Based on the above results, in this embodiment, the alignment film is formed so that the azimuth angle retardation is 1.0 or more and the anchoring strength is 0.99 Jm ⁻² or more. That is, it can be seen from this example that a liquid crystal display device with no afterimage can be obtained as long as the orientation film has an azimuth angle retardation of 1.0 or more and an anchoring strength of 1.0 Jm ⁻² or more.

Comparative Example 1

In the alignment treatment of the alignment film, the irradiation energy of the polarized irradiation system used is about 15 mW / cm ² in terms of a wavelength of 254 nm, and the irradiation time is adjusted so that the irradiation amount of this linearly polarized light is 5 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 150 ° C., and irradiation was performed while heating. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth angle retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Comparative Example 1 was the same and was 0.7.

The anchoring strengths of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Comparative Example 1 were the same and were 6.2 × 10 ⁻⁴ Jm ⁻² .

  When the black and white checker pattern is displayed for 2 hours on the liquid crystal display device manufactured by the method of Comparative Example 1 and this display pattern is stopped and immediately the entire black display is performed, the black and white checker pattern is confirmed as an afterimage even in the full black display. It was done.

Comparative Example 2

  In the alignment treatment of the alignment film, a rubbing treatment was performed using a rayon cloth (YA-19R manufactured by Yoshikawa Processing) at a roll rotation speed of 500 rpm, a roll traveling speed of 20 mm / second, and an indentation amount of 0.6 mm. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Comparative Example 2 was the same and was 0.7.

The anchoring strengths of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Comparative Example 2 were the same, 1.1 × 10 ⁻⁴ Jm ⁻² .

  When the black and white checker pattern was displayed on the liquid crystal display device produced by the method of Comparative Example 2 for 2 hours, and this display pattern was stopped and the entire black display was performed immediately, the black and white checker pattern immediately disappeared. However, streaky luminance unevenness occurred in the entire black display of the liquid crystal display device. When the alignment film surfaces of the substrate SUB1 and the substrate SUB2 of the liquid crystal display device were observed with a microscope, streak-like scratches associated with rubbing were confirmed on the surface. In addition, defects in which some of the pixels are not displayed were seen in several places.

  The experimental results of the above examples and comparative examples are summarized in Table 1.

In Example 1, for the substrate SUB2 on which an organic film such as the color filter CF is formed and the substrate SUB1 on which the pixel electrode PX and the counter electrode CT are formed, 6% N of polyamic acid or polyimide is formed on these substrates. -A methylpyrrolidone solution was applied by a spin coat method and heat-treated at 230 ° C for 2 hours to form an alignment film layer ORI2 or ORI1 having a thickness of 100 nm. In the alignment treatment of the alignment film, using a polarized light irradiation system having a light intensity of about 15 mW / cm ^{2 in} terms of a wavelength of 254 nm, the irradiation time is adjusted so that the irradiation amount of this linearly polarized light is 20 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 150 ° C., and irradiation was performed while heating. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth angle retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Example 2 was the same, 2.1.

In Example 1, with respect to the substrate SUB2 on which an organic film such as the color filter CF is formed and the substrate SUB1 on which the pixel electrode PX and the counter electrode CT are formed, 8% N of polyamic acid or polyimide is formed on these substrates. -A methylpyrrolidone solution was applied by spin coating, and heat treatment was performed at 230 ° C for 2 hours to form an alignment film layer ORI2 or ORI1 having a thickness of 200 nm. In the alignment treatment of the alignment film, using a polarized light irradiation system having a light intensity of about 15 mW / cm ^{2 in} terms of a wavelength of 254 nm, the irradiation time is adjusted so that the dose of the linearly polarized light is 15 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 200 ° C., and irradiation was performed while heating. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth angle retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Example 3 was the same and was 5.4.

In Example 1, with respect to the substrate SUB2 on which an organic film such as the color filter CF is formed and the substrate SUB1 on which the pixel electrode PX and the counter electrode CT are formed, 8% N of polyamic acid or polyimide is formed on these substrates. -A methylpyrrolidone solution was applied by spin coating under low-speed rotation conditions, and heat treatment was performed at 230 ° C for 2 hours to form an alignment film layer ORI2 or ORI1 having a thickness of about 0.5 µm. In the alignment treatment of the alignment film, using a polarized light irradiation system having a light intensity of about 15 mW / cm ^{2 in} terms of a wavelength of 254 nm, the irradiation time is adjusted so that the dose of the linearly polarized light is 30 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 200 ° C., and irradiation was performed while heating. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth angle retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Example 4 was the same, 11.9.

In Example 1, the substrate SUB2 on which an organic film such as the color filter CF is formed and the substrate SUB1 on which the pixel electrode PX and the counter electrode CT are formed are 10% N of polyamic acid or polyimide on these substrates. -A methylpyrrolidone solution was applied by spin coating under low-speed rotation conditions, and heat treatment was performed at 230 ° C for 2 hours to form an alignment film layer ORI2 or ORI1 having a thickness of about 1.0 µm. In the alignment treatment of the alignment film, using a polarized light irradiation system having a light intensity of about 15 mW / cm ^{2 in} terms of a wavelength of 254 nm, the irradiation time is adjusted so that the irradiation amount of this linearly polarized light is 60 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 200 ° C., and irradiation was performed while heating. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth angle retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Example 5 was the same, which was 20.3.

In Example 1, for the substrate SUB2 on which an organic film such as the color filter CF is formed and the substrate SUB1 on which the pixel electrode PX and the counter electrode CT are formed, 10% N of polyamic acid or polyimide is formed on these substrates. -A methylpyrrolidone solution was applied by spin coating under low-speed rotation conditions, and heat treatment was performed at 230 ° C for 2 hours to form an alignment film layer ORI2 or ORI1 having a thickness of about 1.0 µm. In the alignment treatment of the alignment film, using a polarized light irradiation system having a light intensity of about 15 mW / cm ^{2 in} terms of a wavelength of 254 nm, the irradiation time is adjusted so that the irradiation amount of this linearly polarized light is 60 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 200 ° C., and irradiation was performed while heating.

On these substrates, a 10% N-methylpyrrolidone solution of polyamic acid or polyimide was further applied by a spin coating method under low-speed rotation conditions, and heat treatment was performed at 230 ° C. for 2 hours to obtain a total film thickness of about 2.0 μm. The alignment film layer ORI2 or ORI1 was formed. In the alignment treatment of the alignment film, using a polarized light irradiation system having a light intensity of about 15 mW / cm ^{2 in} terms of a wavelength of 254 nm, the irradiation time is adjusted so that the irradiation amount of this linearly polarized light is 60 J / cm ^2. And irradiated. At the time of irradiation, the substrate was placed on a hot plate that can be heated to 200 ° C., and irradiation was performed while heating. Other liquid crystal display device manufacturing methods were performed in the same manner as in Example 1.

  The azimuth angle retardation of the substrates SUB1 and SUB2 of the liquid crystal display device manufactured by the method of Example 6 was the same, 41.3.

  The experimental results of the above examples and comparative examples are summarized in Table 2.

  By adjusting the film thickness, irradiation light amount, and heating temperature at the time of irradiation of the organic film having the property of generating azimuth angle retardation by polarized light irradiation such as the alignment film described above, an arbitrary phase difference of 100 nm or less is obtained. The retardation layer can be created with high accuracy. In Examples 2 to 6, an IPS substrate was used as the base substrate. However, the generation of the azimuth angle retardation involves only the organic film layer having the property of generating the azimuth angle retardation by polarization irradiation regardless of the base substrate. Therefore, it is obvious that the present invention can be applied not only to IPS but also to any other system such as TN, VA, and homogeneous alignment. The azimuth angle retardation obtained by polarized light irradiation in Examples 2 to 6 can be used in various ways. Some examples of Examples 7-12 below are shown.

  FIG. 3 is a schematic diagram for explaining a cross-sectional configuration of a liquid crystal panel constituting a TN mode liquid crystal display device for explaining an embodiment 7 of the present invention. In FIG. 3, this TN liquid crystal panel (also referred to as a TN liquid crystal cell or simply a TN cell) has a configuration in which a liquid crystal layer LC is sandwiched between main surfaces of insulating supports (hereinafter referred to as substrates) SUB1 and SUB2 such as glass. An alignment film ORI1 is disposed on the main surface of one substrate SUB1. Further, an organic film such as a color filter CF is disposed on the main surface of the other substrate SUB2, and an electrode film typified by the counter electrode CT and an alignment film ORI2 are disposed on the color filter CF. Note that the pixel electrode PX is disposed on the main surface of one substrate SUB1, the polarizing plate POL1 is stacked on the outer surface, and the retardation plate PS1 is disposed as necessary. Further, a polarizing plate POL2 is also laminated on the outer surface of the other substrate SUB2, and a retardation plate PS2 is disposed as necessary.

  In Example 7, in the configuration of FIG. 3, the alignment film ORI1 disposed on one substrate SUB1 and the organic film such as the color filter CF impart retardation to the alignment film ORI2 disposed on the other substrate SUB2. The liquid crystal display device provided with a desired value of retardation is configured.

  FIG. 4 is a diagram for explaining a shaft configuration of a liquid crystal panel constituting the TN liquid crystal display device shown in FIG. 4A is a TN liquid crystal panel similar to that in FIG. 3, and FIG. 4B is a diagram for explaining the optical axis relationship of each component layer in FIG. 4A.

  The relationship between each component and the axis will be described with reference to FIG. The pair of polarizing plates provided outside the liquid crystal cell, that is, the upper polarizing plate POL2 and the lower polarizing plate POL1, have an electric field applied to the liquid crystal layer LC as compared with the transmittance when the electric field is applied to the liquid crystal layer LC. It is arranged so that the transmittance is high when not. For example, the upper polarizing plate POL2 and the lower polarizing plate POL1 are arranged via a liquid crystal cell so that their respective polarization axes are orthogonal to each other (so-called crossed Nicols arrangement). That is, the liquid crystal display device shown in FIG. 2 performs display in a so-called normally white mode (hereinafter also referred to as “NW mode”).

  When a sufficiently high voltage is applied to the liquid crystal layer LC, the liquid crystal molecules having positive dielectric anisotropy are aligned almost perpendicular to the substrate surface, and the retardation of the liquid crystal layer when observed from the normal direction of the substrate is very high. The light is reduced and almost no light is transmitted through the upper polarizing plate POL2 and the lower polarizing plate POL1 arranged in the crossed Nicols state, and black is displayed.

  The axial directions of the alignment films ORI2 and ORI1 provided on the upper and lower sides of the liquid crystal cell are set so as to be parallel to the polarization axis of the polarizing plate on the same substrate side. In addition, an organic film such as a color filter CF is formed on at least one substrate (here, the other substrate SUB2). At this time, retardation of 2 to 200 nm (measurement wavelength: 589 nm) is imparted to the two alignment film layers and the organic film layer combined with the upper and lower substrates.

  By such an alignment treatment, the liquid crystal molecules of the liquid crystal layer LC are aligned with a twist of about 90 °. The value of the product Δnd (retardation) of the gap d and the refractive index anisotropy Δn of the liquid crystal cell is set in the range of 350 to 400 nm (measurement wavelength: 589 nm).

  As described above, in the configuration of FIG. 4, as shown in (b-1), the phase difference axis is arranged in parallel or orthogonal to the polarization axis of the upper polarizing plate. Further, as shown in (b-2), the phase difference axis is arranged in parallel or orthogonal to the polarization axis of the lower polarizing plate. The polarizing axis of the upper polarizing plate and the polarizing axis of the lower polarizing plate are disposed so as to be orthogonal to each other (b-3).

  Next, a method for imparting retardation to such a TN liquid crystal panel will be described.

  An alignment film material made of polyimide is printed on the alignment film by spin coating or the like, and a layer having a thickness of about 30 to 3000 nm is formed by baking at 230 ° C. for 2 hours. This is irradiated with polarized light to give retardation by photo-alignment. In addition, as a material to be used, a photodecomposition type photo-alignment polyimide (for example, molecular weight 4000-100000, diamine is BAPP; 2,2-bis {4- (paraaminophenoxy) phenyl} propane, acid anhydride is CBDA 1,2,3,4-cyclobutanetetracarboxylic dianhydride, etc. may be used.

  In addition, a color filter made of acrylic or epoxy, a protective film, or a photodegradable polyimide film is formed on the organic film formed on the base of the alignment film.

As an exposure apparatus for performing photo-alignment, an optical system having a configuration shown in FIG. A high pressure mercury lamp (HgHP) is used as the polarization source, and the emitted light is converted into linearly polarized light having a predetermined polarization direction by a polarization separator or the like. This polarized light reaches the mask through the shutter, and the lower alignment film on the substrate is irradiated with the lens. This linearly polarized light is exposed for about 30 minutes at a wavelength of 254 nm. The irradiation energy at the time of exposure is about 15 mW / cm ² . A desired retardation can be obtained by adjusting the film thickness of the underlying organic film, its presence or absence, and the amount of light irradiation. The retardation of the substrate obtained in Example 7 is shown in Table 2.

  In this way, a TN liquid crystal display device can be configured with a liquid crystal panel provided with a retardation of a desired value. The greater the retardation, the clearer the improvement effect.

  FIG. 5 is a cross-sectional view of a homogeneous liquid crystal panel for explaining an eighth embodiment of the present invention. 3 denote the same functional parts. In a normally white liquid crystal display device with homogeneous alignment, when a sufficiently high voltage is applied to the liquid crystal layer LC, the liquid crystal molecules having positive dielectric anisotropy are aligned almost perpendicular to the substrate surface. The retardation of the liquid crystal layer LC when observed from the line direction becomes very small, and almost no light is transmitted through the upper polarizing plate POL2 and the lower polarizing plate POL1 arranged in the crossed Nicols state, and black is displayed.

  However, the liquid crystal molecules in the liquid crystal layer LC existing in the vicinity of the surfaces of the alignment films ORI1 and ORI2 have a strong alignment regulating force (anchoring effect) from the alignment film, so that in a normal active matrix liquid crystal display device At a voltage of about 5V used, the alignment of these liquid crystal molecules does not change. That is, even when a voltage for performing black display is applied, there are liquid crystal molecules that remain aligned parallel to the substrate surface. The liquid crystal molecules exhibit a finite (non-zero) retardation with respect to light incident perpendicularly to the liquid crystal layer LC. This retardation is called residual retardation, and its size is about 20 nm although it depends on the liquid crystal material. The residual retardation causes light leakage in the black display state (hereinafter also referred to as “black float”), and lowers the contrast ratio.

  In FIG. 5, the liquid crystal is sandwiched between the main surfaces of the substrates SUB1 and SUB2, an organic film such as a color filter CF is disposed on one support, and a counter electrode CT or the like is disposed on the color filter CF. An electrode film and an upper alignment film ORI2 are disposed. Further, a lower alignment film ORI1 is disposed on the main surface of the lower substrate SUB1.

  In Example 8, in the panel configuration shown in FIG. 5 described above, by providing retardation to the alignment film disposed on one substrate and the organic film such as a color filter, and the alignment film disposed on the other substrate. A liquid crystal display device having a desired value of retardation is configured.

  FIG. 6 is a diagram showing the shaft configuration of the homogeneous alignment type liquid crystal panel shown in FIG. 5 for explaining the eighth embodiment of the present invention. 6A is a cross-sectional configuration of the same liquid crystal panel as FIG. 5, and FIG. 6B is an explanatory diagram of the shaft configuration of FIG. 6A. In FIG. 6B, “axis 1-a-1 (i)” indicates the case where the orientation axis and the phase difference direction are substantially horizontal, and “axis 1-a-1 (ii)” indicates the orientation axis and the phase difference. The case where the directions of are substantially orthogonal is shown. In order to make the orientation axis and the phase difference direction substantially orthogonal to each other, a layer in which a phase difference is formed is formed a plurality of times as in Example 6 and light is irradiated on the outermost layer and other layers. Can be realized by making them substantially orthogonal.

  The pair of polarizing plates provided on the outer surface of the liquid crystal panel, that is, the upper polarizing plate POL2 and the lower polarizing plate POL1, have an electric field applied to the liquid crystal layer LC compared to the transmittance when the electric field is applied to the liquid crystal layer LC. It is arranged so that the transmittance is high when not. For example, the upper polarizing plate POL2 and the lower polarizing plate POL1 are arranged via a liquid crystal panel so that their polarization axes are orthogonal to each other (so-called crossed Nicols arrangement).

  The axial directions of the alignment films ORI2 and ORI1 provided on the upper side and the lower side of the liquid crystal panel are set so as to form a 45 ° angle with the polarization axis of the polarizing plate on the same substrate side. The liquid crystal molecules of the liquid crystal layer LC are aligned with a 45 ° angle with the polarization axis of the polarizing plate. At this time, the product Δnd (retardation) of the gap d of the liquid crystal panel LC of the liquid crystal layer and the refractive index anisotropy Δn is set in a range of 350 to 400 nm (measurement wavelength: 589 nm).

  As shown in FIG. 6B-3, the alignment axis of the alignment film ORI2 arranged on the upper polarizing plate POL2 side of the liquid crystal layer is arranged so as to be orthogonal to the retardation axis. Further, as shown in (b-4), the alignment film ORI1 arranged on the lower polarizing plate POL1 side of the liquid crystal layer is also arranged so as to be orthogonal to the retardation axis. Note that the alignment axis ORI2 and the organic film phase axis are arranged in the same direction (b-5).

  With the above configuration, when no voltage is applied, the retardation of the liquid crystal layer is maximized when observed from the normal direction of the substrate, and white is displayed by the light transmitted through the upper and lower polarizing plates arranged in the crossed Nicols state. Is done.

  When a sufficiently high voltage is applied to the liquid crystal layer, the liquid crystal molecules having positive dielectric anisotropy are aligned almost perpendicular to the substrate surface, and the retardation of the liquid crystal layer when observed from the normal direction of the substrate is very small. Thus, almost no light is transmitted through the upper polarizing plate and the lower polarizing plate arranged in the crossed Nicols state, and black is displayed.

  An organic film such as a color filter is formed on at least one side substrate. A part of this organic film is composed of an organic film layer having a property that azimuth angle retardation is generated by irradiation with polarized light, and is oriented as shown by “axis 1-a-1 (i)” in FIG. The shaft is arranged so that the direction of the phase difference from the shaft is substantially horizontal. This organic film was produced by the method according to Example 6, and the azimuth angle retardation was 41.3 nm. An alignment film was formed on this layer according to the conditions of Example 5. As a result, the azimuth angle retardation of this substrate SUB2 was 61.6 nm. On the substrate SUB1, the organic film layer having the property of generating azimuth angle retardation by polarized light irradiation was only the alignment film, and the azimuth angle retardation was 20.3 nm.

  Effect of substrate with retardation: When a sufficiently high voltage is applied to the liquid crystal layer, liquid crystal molecules having positive dielectric anisotropy are aligned almost perpendicular to the substrate surface, and are observed when viewed from the normal direction of the substrate. The retardation of the liquid crystal layer becomes very small, and almost no light passes through the upper polarizing plate POL2 and the lower polarizing plate POL1 arranged in the crossed Nicols state, and black is displayed.

  However, since liquid crystal molecules existing in the vicinity of the surface of the alignment film have a strong alignment regulating force (anchoring effect) from the alignment film, at a voltage of about 5 V used in a normal active matrix liquid crystal display device. The alignment of these liquid crystal molecules does not change. That is, even when a voltage for performing black display is applied, there are liquid crystal molecules that remain aligned parallel to the substrate surface. The liquid crystal molecules exhibit a finite (non-zero) retardation for light that is incident perpendicular to the liquid crystal layer. This retardation is called residual retardation, and its size is about 20 nm, although it depends on the liquid crystal material. The residual retardation causes light leakage in the black display state (hereinafter also referred to as “black float”), and lowers the contrast ratio.

  In order to compensate for this phase difference, a phase difference plate orthogonal to the direction of residual azimuth angle retardation may be attached to the outside. However, the required azimuth angle retardation value is as small as about 20 nm, and on the other hand, it is difficult to manufacture a retardation plate attached to the outside with a small azimuth angle retardation value of 20 nm. However, in this embodiment, the substrate SUB2 has an azimuth angle retardation of 61.6 nm, and the substrate SUB1 has an azimuth angle retardation of 20.3 nm. Since the residual azimuth angle retardation of the liquid crystal is the same as the alignment direction of the alignment film, the azimuth angle retardation of the entire liquid crystal cell is 102 nm, and this value of azimuth angle retardation is a readily available 102 nm retardation plate. Can be offset by being arranged so as to be substantially orthogonal to the phase difference axis direction, and light leakage can be suppressed.

  In contrast to Example 8, a part of the organic film of the substrate SUB2 is composed of an organic film layer having a property of generating azimuth angle retardation by polarized light irradiation, and “axis 1-a-1” in FIG. As in (ii), the axes are arranged so that the orientation axis and the phase difference direction are substantially orthogonal. This organic film was produced by the method according to Example 5, and the azimuth angle retardation was 20.3 nm. An alignment film was formed on this layer in accordance with the conditions of Example 1 so that the phase axis was substantially orthogonal to the lower organic film.

  The residual azimuth angle retardation of the liquid crystal is the same as the alignment direction of the alignment film, and becomes 22.3 nm when combined with the azimuth angle retardation of the alignment film. However, since the azimuth angle retardation of 20.3 nm is formed in the organic film layer so as to be orthogonal to this, the azimuth angle retardation of the entire liquid crystal cell is reduced to 2.3 nm, and light leakage can be suppressed.

  FIG. 7 is a cross-sectional configuration diagram of a vertical alignment type liquid crystal panel. The same reference numerals as those in the embodiment in FIG. 5 correspond to the same functional parts. A vertical alignment (VA) type liquid crystal panel does not require an alignment film. However, when there is no alignment film and the liquid crystal is aligned completely vertically, the driving direction of the liquid crystal when a voltage is applied becomes uniform. Domain may occur. For this reason, it is better to arrange the alignment film and perform the alignment treatment. However, performing this alignment treatment means that the liquid crystal layer has a pretilt in the initial alignment state, and the retardation does not become zero, so that there is a problem that light leakage occurs and the contrast is lowered.

  In FIG. 7, a liquid crystal layer is sandwiched between a pair of substrates, an organic film such as a color filter CF is disposed on the main surface of one substrate SUB2, and an electrode film such as a counter electrode is disposed on the color filter CF. An alignment film ORI2 is disposed. Further, the pixel electrode PX and the alignment film ORI1 are disposed on the main surface of the other substrate SUB1.

  In Example 10, in such a configuration of FIG. 7, it is desired to provide retardation to the alignment film and the organic film such as the color filter disposed on one substrate and the alignment film disposed on the other substrate. The liquid crystal display device which gave the retardation of the value of is comprised.

  A method for providing the azimuth angle retardation of such a VA liquid crystal display device can be obtained by the same method as in the first to sixth embodiments. Here, the axes are arranged so that the direction of the alignment axis and the phase difference are substantially horizontal. The substrate SUB1 and the substrate SUB2 have an azimuth retardation of 41.3 nm. Since the alignment layer is an extremely weak alignment treatment, almost no azimuth angle retardation occurs. The residual azimuth angle retardation of the liquid crystal layer is about 2 to 3 nm, and the azimuth angle retardation formed in the alignment axis direction is 85 nm in total. This value of azimuth angle retardation can be offset by arranging an easily available 85 nm retardation plate so as to be substantially orthogonal to the phase difference axis direction of the liquid crystal cell, and light leakage can be suppressed.

  Compared to Example 10, a part of the organic film of the substrate SUB2 is composed of an organic film layer having a property of generating azimuth angle retardation by polarized light irradiation so that the orientation axis and the phase difference direction are substantially orthogonal to each other. It is axially arranged. This organic film was produced by the method according to Example 1, and the azimuth angle retardation was 2 nm. Further, an alignment film was formed on this layer so that the phase axis was substantially orthogonal to the lower organic film. Since the alignment layer is an extremely weak alignment treatment, almost no azimuth angle retardation occurs.

  The residual azimuth angle retardation of the liquid crystal is the same as the alignment direction of the alignment film, and is 2 to 3 nm when combined with the azimuth angle retardation of the alignment film. However, since the azimuth angle retardation of 2 nm is formed in the organic film layer so as to be orthogonal to this, the azimuth angle retardation of the entire liquid crystal cell is reduced to 1 nm, and light leakage can be suppressed.

  A twelfth embodiment of the present invention will be described with reference to FIG. In the IPS liquid crystal panel, since the alignment axis of the alignment film and the polarization axis of the polarizing plate are arranged to coincide with each other, even if there is a phase difference in the alignment film layer, the influence can be ignored. However, in reality, it is difficult to make the angles of the alignment axis and the polarization axis completely coincide with each other, and the alignment axis having a phase difference causes a light leak due to the phase difference corresponding to the axis deviation angle of the polarization axis, resulting in a decrease in contrast. It becomes a factor of. The residual retardation of the alignment film is usually as small as 1 nm or less, and correction with a retardation plate laminated on the outer surface of the substrate is extremely difficult.

  In the cross-sectional structure of the liquid crystal panel constituting the IPS type liquid crystal display device shown in FIG. 1A, the liquid crystal layer LC is sandwiched between the substrates SUB1 and SUB2, and the color filter CF is formed on the main surface of one substrate SUB2. An alignment film ORI2 is disposed on the color filter CF. Further, the pixel electrode PX and the counter electrode CT are disposed on the main surface of the substrate SUB1, and the alignment film ORI1 is disposed thereon.

  In Example 12, in such a cross-sectional structure, a desired value is obtained by imparting retardation to an alignment film and an organic film such as a color filter disposed on one substrate and an alignment film disposed on the other substrate. The liquid crystal panel which gave the retardation is comprised.

  In the shaft configuration of the IPS liquid crystal panel shown in FIG. 1B, the pair of polarizing plates stacked on the outer surface of the liquid crystal panel, that is, the upper polarizing plate POL2 and the lower polarizing plate POL1, have an electric field applied to the liquid crystal layer LC. The liquid crystal layer is disposed such that the transmittance when no electric field is applied is higher than the transmittance when it is applied. For example, the upper polarizing plate POL2 and the lower polarizing plate POL1 are arranged via a liquid crystal panel so that their polarization axes are orthogonal to each other (so-called crossed Nicols arrangement).

  The axial directions of the alignment films ORI2 and ORI1 provided on the upper side and the lower side of the liquid crystal panel are set so as to form an angle parallel to the polarizing axis of the polarizing plate on the same substrate side (that is, 0 °). The liquid crystal molecules are arranged along the axial direction of the alignment film. At this time, the product Δnd (retardation) of the gap d of the liquid crystal panel of the liquid crystal layer and the refractive index anisotropy Δn is set in a range of 350 to 400 nm (measurement wavelength: 589 nm).

  With the above configuration, when no voltage is applied, the retardation of the liquid crystal layer when viewed from the normal direction of the substrate is minimized, and black is displayed by the light transmitted through the upper and lower polarizers arranged in the crossed Nicols state. Is done.

  When a sufficiently high voltage is applied to the liquid crystal layer, the liquid crystal molecules having positive dielectric anisotropy tilt in the direction of the electric field formed between the electrodes and form a non-zero angle with the polarizing plate, thereby causing the normal direction of the substrate When viewed from above, the light of the lower polarizing plate POL1 arranged in the crossed Nicol state is transmitted through the upper polarizing plate POL2 depending on the retardation value of the liquid crystal layer, and white is displayed.

  The method of providing the azimuth angle retardation of such an IPS type liquid crystal display device can be obtained by the same method as in the first to sixth embodiments. Here, the axes are arranged so that the direction of the alignment axis and the phase difference are substantially horizontal. The substrate SUB1 and the substrate SUB2 have an azimuth angle retardation of 2 nm by performing light irradiation according to the method of Example 2.

  The phase difference axis of the organic film is shifted to the left by 0.5 ° with respect to the original design value due to a problem in the light irradiation apparatus. The alignment film layer has an azimuth retardation of 1 nm by performing light irradiation according to the method of Example 1. When irradiating light, the orientation direction of the alignment film is shifted to the right by 0.5 ° with respect to the original design value by reversing the feeding direction of the substrate to be introduced to that of the organic film. The residual azimuth retardation of the liquid crystal layer is about 2 to 3 nm, and the total azimuth retardation formed in the alignment axis direction is 5 nm. However, the azimuth retardation in the direction of the organic film layer is perpendicular to the alignment direction. The azimuth angle retardation is canceled and light leakage can be suppressed.

  As described above, a liquid crystal display device in which an afterimage is not easily generated even by the photo-alignment process can be produced. Further, it can be used for a method of forming phase differences of various azimuth angle retardation values, and can be effectively used for reducing light leakage of various liquid crystal cells.

SUB1, SUB2 ... Substrate, LC ... Liquid crystal layer, ORI1, ORI2 ... Alignment film, CF ... Color filter, CT ... Counter electrode, PX ... Pixel electrode, POL1, POL2, ... -Polarizing plate, PS1, PS2 ... retardation plate.

Claims (3)

In liquid crystal display devices,
A liquid crystal display device having an azimuth angle retardation value of 1 to 80 nm on an alignment film or a film on a substrate. The liquid crystal display device according to claim 1.
The liquid crystal display device, wherein the alignment film is an alignment film aligned by light irradiation. The liquid crystal display device according to claim 1 or 2,
The liquid crystal display device is an IPS type liquid crystal display device.

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