JP2007264037A - Liquid crystal display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a domain-divided liquid crystal display device of VATN mode, in which a higher aperture rate and improved display characteristics are obtained. <P>SOLUTION: The liquid crystal display device has a first substrate and a second substrate, a liquid crystal layer provided between the substrates, a first alignment layer provided on a surface of the first substrate on the side of the liquid crystal layer, and a second alignment layer provided on a surface of the second substrate on the side of the liquid crystal layer. The liquid crystal layer contains liquid crystal molecules having negative dielectric constant anisotropy, and the first alignment layer and second alignment layer align nearby liquid crystal molecules substantially perpendicularly to alignment layer surfaces and orthogonally to each other and also have two or more regions where the nearby liquid molecules are aligned in different directions for each pixel. The liquid crystal display device includes a change-over-time suppressing means for dark line width. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a liquid crystal display device and a manufacturing method thereof. More specifically, the present invention relates to a liquid crystal display device with high display quality, which can obtain a wide viewing angle and high-speed response, and can be widely applied to monitors for televisions, personal computers, and the like, and a manufacturing method thereof.

In recent years, a vertical alignment (VA) mode liquid crystal display panel has a wide viewing angle characteristic, and is therefore used in liquid crystal display devices such as personal computer monitors and televisions. In particular, as an alignment control structure, an electrode slit is provided on one substrate, a projection structure is provided on the other substrate, and an MVA (Multi-Domain Vertical Alignment) mode in which pixel division (alignment division) is performed, and electrode slits are provided on both substrates. A VA mode liquid crystal display device in which alignment division such as PVA (Patterned Vertical Alignment) mode in which pixel division (alignment division) is performed has been put into practical use.

However, the MVA mode and PVA mode liquid crystal display devices have room for improvement in that the response speed is slow. That is, even when a high voltage is applied to respond from the black state to the white state, it is only the liquid crystal molecules near the electrode slit and the protrusion structure that start to respond instantaneously, and a distance far from these alignment control structures. The liquid crystal molecules in are delayed in response.

In order to improve the response speed, it is effective to provide an alignment film on the surface of the substrate on the liquid crystal layer side and perform an alignment treatment to give a pretilt angle to the liquid crystal molecules in advance. Even in the VA mode, by slightly tilting the liquid crystal molecules with respect to the vertical alignment film in advance, it becomes easy to tilt the liquid crystal molecules when a voltage is applied to the liquid crystal layer, so that the response speed can be increased. it can. Examples of the alignment treatment method for imparting a pretilt angle to the liquid crystal molecules include a rubbing method, a method of obliquely depositing SiO _X, and a photo alignment method.

In the MVA mode and the PVA mode, alignment division is performed as a means for obtaining a wide viewing angle. However, when alignment division is performed, there is room for improvement in that the number of alignment treatment steps for the alignment film is increased. was there. For example, a rubbing method has been proposed in which a rubbing region and a non-rubbing region are separated by patterning with a resist. In the photo-alignment method, a method of performing alignment division by performing exposure through a photomask a plurality of times has been proposed. It is desirable that the number of times of performing these alignment treatments is small from the viewpoint of simplifying the manufacturing process. However, in order to ensure a wide viewing angle, the number of domains of one pixel is desirably 2 or more, and particularly desirably 4 or more. Therefore, there has been a demand for a method that can secure a large number of domains with a small number of alignment treatments.

As the VA mode in which alignment division is performed, as shown in FIGS. 15, 16-1 and 16-2, for any domain, a VA mode using a vertical alignment film in which the alignment treatment direction is antiparallel to each other substrate. (Hereinafter also referred to as VAECB (Vertical Alignment Electrically Controlled Birefringence) mode) has been proposed. In the VAECB mode, as shown in FIG. 16A, the absorption axis direction of the first polarizing plate 5 provided on the first substrate side and the absorption axis direction of the second polarizing plate 6 provided on the second substrate side, The alignment orientation of the first alignment film 1a and the second alignment film 2a is shifted by 45 degrees. In the case of the VAECB mode, in the type in which one pixel excellent in viewing angle is divided into four domains, alignment processing is performed in four directions of 45 degrees, 135 degrees, 225 degrees, and 315 degrees as shown in FIG. Therefore, the throughput during mass production is reduced. For example, when the VAECB mode is formed by performing an alignment process by the photo-alignment method, the alignment film exposure process is required eight times in total.
On the other hand, in the case of a VAHAN (Vertical Alignment Hybrid-Aligned Nematic) mode in which a vertical alignment film is formed on one substrate but no alignment treatment is performed, the number of alignment treatments can be reduced. Since the pretilt angle of the molecule remains 90 degrees, there is room for improvement in response speed.

On the other hand, a VA mode (hereinafter also referred to as a VATN (Vertical Alignment Twisted Nematic) mode) in which liquid crystal molecules have a twist structure by using a vertical alignment film in which the alignment processing directions are orthogonal to each other is proposed. (For example, refer to Patent Document 1). In the VATN mode, the absorption axis direction of the first polarizing plate and the alignment direction of the first alignment film are the same, and the absorption axis direction of the second polarizing film and the alignment direction of the second alignment film are the same. Further, the absorption axis direction of the first polarizing plate and the alignment direction of the second alignment film may be the same, and the absorption axis direction of the second polarizing plate and the alignment direction of the first alignment film may be the same. In the case of the VATN mode, as shown in FIG. 7, in a mode in which one pixel is divided into four domains (hereinafter also referred to as a 4VATN mode), only four alignment processes are required, which is half the number of alignment processes in the 4VAECB mode. .

Such a VATN mode is excellent in principle in that it can realize a wide viewing angle and high-speed response with a small number of processes, but has not yet reached the stage where the manufacturing technology has been established, and is practical. There is still room for improvement in terms of realizing level display characteristics. For example, there has been a technique for preventing image burn-in in a 4VATN mode liquid crystal display device (see, for example, Patent Document 1). In particular, due to the strong demand for higher aperture ratios in recent liquid crystal display devices, in the VATN mode liquid crystal display device in which the alignment is divided such as the 4VATN mode, the area of the light shielding film for concealing the dark line generated at the domain boundary can be increased. There was room for further improvement in terms of reducing the size as much as possible and achieving a high aperture ratio. Further, in the VATN mode liquid crystal display device, an afterimage may be seen on the display screen, and there is room for improvement in terms of further improving display characteristics.
JP-A-11-133429

The present invention has been made in view of the above-described situation, and an object of the present invention is to realize a high aperture ratio and an improvement in display characteristics of an alignment-divided VATN mode liquid crystal display device.

The inventors of the present invention have made various studies on a liquid crystal display device capable of increasing the aperture ratio and improving the display characteristics, and have focused on the alignment-divided VATN mode. As a result of the study, it has been found that in the VATN mode in which the orientation is divided, the width of the dark line generated at the domain boundary changes with time, and the width of the dark line gradually increases with time. As a result of further investigations, it has been found that in the VATN mode in which the orientation is divided, it is possible to reduce the increase in the width of the dark line due to a change with time by controlling the pretilt angle or the like. Then, it has been found that a liquid crystal display device having a high aperture ratio and excellent display characteristics can be realized by providing an alignment-divided VATN mode liquid crystal display device with means for suppressing dark line width aging, and the above-mentioned problems are solved. The present inventors have arrived at the present invention by conceiving that it can be solved on a case-by-case basis.

That is, the present invention includes a first substrate and a second substrate, a liquid crystal layer provided between the substrates, a first alignment film provided on a surface of the first substrate on the liquid crystal layer side, and the second substrate. And a second alignment film provided on the surface of the liquid crystal layer, wherein the liquid crystal layer includes liquid crystal molecules having negative dielectric anisotropy, and the first alignment The film and the second alignment film are for aligning the liquid crystal molecules in the vicinity thereof in a direction substantially perpendicular to the surface of the alignment film and perpendicular to each other. The liquid crystal display device is a liquid crystal display device provided with means for suppressing change in dark line width over time.
The present invention is described in detail below.

The liquid crystal display device of the present invention is provided as a basic configuration of the liquid crystal display device, on the first substrate and the second substrate, the liquid crystal layer provided between the substrates, and the surface of the first substrate on the liquid crystal layer side. A first alignment film; and a second alignment film provided on the surface of the second substrate on the liquid crystal layer side. The configuration of the liquid crystal display device of the present invention is not particularly limited as long as such components are formed as essential components, and may or may not include other components. Usually, the first polarizing plate and the second polarizing plate are provided on the surfaces of the first and second substrates opposite to the liquid crystal layers. The absorption axis directions of the first and second polarizing plates are usually arranged so as to be orthogonal to each other, and substantially orthogonal to the alignment treatment direction of the first alignment film and the alignment treatment direction of the second alignment film. Or it arrange | positions so that it may become substantially parallel.

In the liquid crystal display device of the present invention, as a basic configuration of the alignment-divided VATN mode, the liquid crystal layer includes liquid crystal molecules having negative dielectric anisotropy, and the first alignment film and the second alignment film The alignment film aligns liquid crystal molecules in the vicinity thereof in a direction substantially perpendicular to the alignment film surface and perpendicular to each other, and further has two or more regions in which the alignment directions of the liquid crystal molecules in the vicinity are different in one pixel. . By using such a liquid crystal layer and an alignment film, a wide viewing angle VATN mode liquid crystal display device in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface and has a twist structure between the substrates is formed. In this specification, the orientation direction means an orientation shown when the tilt direction of liquid crystal molecules is projected onto the substrate surface.

In the VATN mode, for example, two regions in which the orientation directions of liquid crystal molecules in the vicinity thereof are approximately 180 degrees are formed in each of the first alignment film and the second alignment film, and the first alignment film and the second alignment film are formed. By aligning the alignment films so that the alignment directions of the liquid crystal molecules in the vicinity of the film are orthogonal to each other, each region of the first alignment film is aligned and divided by each region of the second alignment film, and four domains per pixel Can be formed. As a result, when one pixel is divided into four domains, the alignment process performed for alignment division is performed twice for each of the first alignment film and the second alignment film, for a total of four times. The number of times can be reduced from the VAECB mode, which is required four times for the second alignment film, a total of eight times. Therefore, in each alignment film, one pixel can be divided into four or more domains by providing regions having two or more different orientation directions in one pixel, and a sufficient viewing angle can be obtained.

The liquid crystal display device of the present invention includes dark line width change means for suppressing dark line width (means for suppressing an increase in dark line width accompanying change over time). As a result, the time-dependent change in the width of the dark line generated at the domain boundary can be reduced and the area occupied by the light shielding film can be reduced, so that a high aperture ratio can be realized in the alignment-divided VATN mode liquid crystal display device. Can do. In addition, since the change with time of the dark line width is small, it is possible to reduce the change with time of the average transmittance in the pixel and to suppress problems such as the occurrence of an afterimage on the display screen. The display characteristics of the display device can be improved.

In this specification, a dark line is different from a region where light from a backlight is blocked by a light shielding body such as a bus line or a light shielding film, and the orientation direction of liquid crystal molecules and the absorption axis direction of a polarizing plate are the same. It is a dark line with low brightness that occurs on the display screen by becoming or orthogonal. Even if the direction in which the liquid crystal molecules are tilted when the voltage is applied is the same in each domain of the alignment-divided pixel, the directions in which the liquid crystal molecules are tilted are different between different domains. Further, since the liquid crystal molecules are continuous elastic bodies, the liquid crystal molecules are aligned so as to continuously connect the liquid crystal molecules that have fallen in different directions between different domains. Therefore, for example, between different domains in the four-domain alignment, the orientation direction of the liquid crystal molecules is the same as or perpendicular to the absorption axis direction of the polarizing plate usually provided in the liquid crystal display device. In the polarized light in the portion oriented in the same or orthogonal direction as the absorption axis direction of this polarizing plate, the retardation (phase difference) due to liquid crystal molecules does not occur, and the polarized light transmitted through the polarizing plate installed on the backlight side is It is cut by the polarizing plate installed on the display screen side without being affected by the liquid crystal layer, and as a result, it becomes a dark line (dark line in this specification) with low luminance.

In this specification, the width of the dark line is a length between positions that is 90% with respect to the maximum transmittance on a straight line substantially perpendicular to the dark line.
A preferred embodiment of the liquid crystal display device of the present invention will be described in detail below.

The means for suppressing the dark line width change with time is not particularly limited. (A) When the transmittance after 15 milliseconds from the voltage application is T (15) and the transmittance after 100 milliseconds is T (100) In addition, the transmittance decrease defined by T (15) -T (100) is set to be equal to or less than the conversion point in the relationship between the transmittance decrease and the pretilt angles of the liquid crystal molecules in the vicinity of the first alignment film and the second alignment film. (B) A means for setting the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film and the second alignment film to 89.5 degrees or less is preferable. T (15) and T (100) are average transmittances of one pixel after voltage application of 15 milliseconds and 100 milliseconds, respectively. Further, in this specification, the conversion point means an inflection point in a differential curve of a curve indicating the relationship between the transmittance decrease and the pretilt angle.

The technical significance of the parameter (a) is as follows. That is, the significance of the transmittance reduction defined by T (15) -T (100) is that the transmittance reduction is, for example, 8% in the relationship between the transmittance reduction and the pretilt angle as in the embodiment described later. It has been found that it has a critical point (conversion point). More specifically, as the pretilt angle decreases from 90 degrees, the decrease in transmittance decreases. However, in the relationship between them, a conversion point (for example, a point at 8% decrease in transmittance and a point at a pretilt angle of 89.5 degrees). Found that there exists. The liquid crystal display device in which the decrease in transmittance is below the conversion point is compared with a conventional liquid crystal display device having almost no pretilt angle, for example, a liquid crystal display device in which the pretilt angle is greater than 89.5 degrees and less than 90 degrees. Thus, it is apparent from the examples described later that there is a remarkable difference between the effect of suppressing the decrease in transmittance and the effect of suppressing the change in dark line width with time.

Considering the relationship between the decrease in transmittance and the pretilt angle in this way, in order to exert the effect of suppressing the change in dark line width with time, the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film and the second alignment film is transmitted. It is preferable that the ratio be less than or equal to the conversion point in the relationship between the decrease in the rate and the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film and the second alignment film. More specifically, the liquid crystal display device of the present invention has the above (b) As shown in FIG. 5, it is preferable that the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film and the second alignment film is 89.5 degrees or less. Thus, an alignment-divided VATN mode liquid crystal display device having a high aperture ratio and excellent display characteristics can be easily realized.

Further, as another specific form for sufficiently exhibiting the effect of suppressing the change in dark line width over time, the width of the dark line after 100 msec of voltage application is preferably less than 11.5 μm, and is 11.0 μm or less. More preferably, it is 10.5 μm or less.

In the liquid crystal display device, the difference in pretilt angle of the liquid crystal molecules is preferably less than 1.0 degree between the vicinity of the first alignment film and the vicinity of the second alignment film, and more preferably 0.5 degrees or less. In this way, by controlling the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film and the pretilt angle of the liquid crystal molecules in the vicinity of the second alignment film with high accuracy, transmission due to variations in the pretilt angle is achieved in the VATN mode liquid crystal display device. It is possible to suppress a decrease in rate, obtain a stable transmittance, and improve display luminance characteristics.

In the liquid crystal display device, a pretilt angle of liquid crystal molecules in the vicinity of the first alignment film and the second alignment film is preferably 89 degrees or less. Thereby, even in the VATN mode, a liquid crystal display device having a high transmittance equivalent to that in the VAECB mode can be provided.

The material of the first alignment film and / or the second alignment film is not particularly limited, but is preferably a photo-alignment film. In particular, the first alignment film and / or the second alignment film is a 4-chalcone. A group (the following chemical formula (1)), a 4'-chalcone group (the following chemical formula (2)), a coumarin group (the following chemical formula (3)), and a cinnamoyl group (the following chemical formula (4), also referred to as a cinnamate group). It preferably contains at least one photosensitive group selected from the group or a bond structure thereof.

In the present specification, the photo-alignment film means a film formed of a material whose alignment regulating force changes by light irradiation, and includes a photosensitive group-bonded structure means that the photo-sensitive film included in the constituent molecules. This means that it includes a structure (crosslinked structure) in which these functional groups are bonded to each other. Using the above photosensitive group or its bonded structure alignment film and controlling the wavelength, light amount, irradiation angle, polarization direction, etc. and performing alignment treatment by light irradiation, the pretilt angle of the liquid crystal molecules was controlled with high precision and stabilized. A pretilt angle can be obtained, and a desired transmittance can be controlled in the liquid crystal display device.

In addition to the dimerization reaction, the photosensitive group causes an isomerization reaction and reorientation. According to this, variation in the pretilt angle can be effectively suppressed, and the desired pretilt angle and transmission can be reduced. It is possible to easily provide a VATN mode liquid crystal display device having a ratio. In addition, the alignment film containing the photosensitive group preferably does not cause a photodecomposition reaction, and thus, the pretilt angle is more effectively improved than a photodecomposition type alignment film in which the alignment regulation force is changed by the photodecomposition reaction. Variations can be suppressed. For example, an alignment film material having a cinnamoyl group undergoes a dimerization reaction as shown in the following chemical formulas (5) and (6), and an isomerization reaction from a trans isomer to a cis isomer as shown in the following chemical formula (7). Do. In addition, reorientation means that the direction of a constituent molecule changes through an excited state by light.

In addition, the bonding structure of the photosensitive group is preferably formed by a dimerization reaction from the viewpoint of effectively suppressing variation in the pretilt angle. In this case, for example, light having a wavelength of 250 to 400 nm is used. Irradiation can form a bonded structure.

The present invention also relates to a method for manufacturing a liquid crystal display device according to the present invention, wherein the manufacturing method reduces the transmittance defined by T (15) -T (100), and reduces the transmittance and the first alignment film. And the first alignment film and the second alignment film in which the pretilt angle of the liquid crystal molecules in the vicinity of the alignment film is 89.5 degrees or less in order to make the conversion point or less in the relationship with the pretilt angle of the liquid crystal molecules in the vicinity of the second alignment film. It is also a manufacturing method of the liquid crystal display device including the process of forming. Thus, an alignment-divided VATN mode liquid crystal display device having a high aperture ratio and excellent display characteristics can be easily manufactured.

According to the liquid crystal display device of the present invention, a high aperture ratio and an improvement in display characteristics can be realized in the VATN mode using a vertical alignment film in which the alignment processing directions are orthogonal to each other.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
1A and 1B are conceptual diagrams for explaining the driving principle of the VATN mode liquid crystal display device according to the first embodiment. FIG. 1A shows an OFF state, and FIG. 1B shows an ON state.
As shown in FIG. 1A, the VATN mode liquid crystal display device of this embodiment includes an opposing substrate (not shown), a liquid crystal layer 7 provided between the substrates, and one substrate (first substrate). ) Of the first alignment film 1 provided on the liquid crystal layer side surface and the second alignment film 2 provided on the liquid crystal layer side surface of the other substrate (second substrate). Is configured to include liquid crystal molecules having negative dielectric anisotropy. In the VATN mode liquid crystal display device according to the present embodiment, in the off state (voltage off state) in which the voltage applied between the substrates is less than the threshold voltage, the first alignment film and the second alignment film are adjacent to each other. Liquid crystal molecules are aligned in a direction substantially perpendicular to the surface of the alignment film (usually substantially the same surface as the substrate) and perpendicular to each other. That is, in the voltage off state, the first alignment film and the second alignment film align liquid crystal molecules in the vicinity thereof substantially perpendicular to the surface of the alignment film and align liquid crystal molecules in the vicinity thereof in directions orthogonal to each other. ing. In this specification, “the first alignment film and the second alignment film align liquid crystal molecules in the vicinity thereof in directions orthogonal to each other” means that the alignment directions of the liquid crystal molecules in the vicinity of the first alignment film and It means that the orientation directions of the liquid crystal molecules in the vicinity of the two alignment films are orthogonal to each other. “Orienting liquid crystal molecules in the vicinity thereof in directions orthogonal to each other” means that the liquid crystal molecules in the vicinity of the first and second alignment films are substantially orthogonal to each other to the extent that liquid crystal display in the VATN mode is possible. Liquid crystal molecules in the vicinity of the first and second alignment films do not have to be completely orthogonal, and the alignment orientation of the liquid crystal molecules in the vicinity of the first and second alignment films is 85 to 95 degrees. It is preferable to cross. On the other hand, as shown in FIG. 1B, in the on state (voltage on state) in which the voltage applied between the substrates exceeds the threshold voltage, the VATN mode liquid crystal display device of this embodiment has a negative dielectric The liquid crystal molecules having anisotropy are aligned in a direction parallel to the substrate surface according to the applied voltage, and exhibit birefringence with respect to the transmitted light of the liquid crystal display panel.

Hereinafter, a manufacturing method of the VATN mode liquid crystal display device according to the first embodiment will be described.
In this embodiment, first, a pair of substrates before alignment film formation is prepared by a normal method.
As the first substrate, which is one substrate, (1) a thin film forming process using sputtering, plasma enhanced chemical vapor deposition (PCVD), vacuum deposition, etc., (2) a resist that is baked after spin coating, roll coating, etc. Coating process, (3) exposure process by exposure methods such as lens projection (stepper), mirror projection, proximity, (4) development process, (5) etching process by dry etching, wet etching, etc., (6) plasma (dry ) Repeating the resist stripping process by ashing, wet stripping, etc. to form a thin film and pattern it so that the scanning signal lines and the data signal lines cross in a grid pattern on the glass substrate through the insulating film. Thin film transistor in which a thin film transistor and a pixel electrode are formed at each intersection Ray to produce a substrate (TFT array substrate).
The second substrate, which is the other substrate, is a color in which (1) a black matrix, (2) an RGB coloring pattern, (3) a protective film, and (4) a transparent electrode film are sequentially formed on a glass substrate. A filter substrate (CF substrate) is produced.

Next, after applying a solution of alignment film material to the first substrate and the second substrate by spin casting, the alignment film is formed by baking, for example, at 180 ° C. for 60 minutes. In this embodiment, a material having a 4-chalcone group is used as the alignment film material.

Subsequently, in order to obtain a desired pretilt angle, the light irradiation angle, light irradiation intensity, light irradiation time, etc. are appropriately set for the alignment film along the alignment direction shown in FIG. Perform the process. For example, when P-polarized light with an incident angle of 40 degrees and a wavelength of 365 nm is irradiated to the alignment film at an intensity of 3 mW / cm ² for 400 seconds, the pretilt angles of the liquid crystal molecules in the vicinity of the first and second alignment films are both 88.5 degrees. became. The constituent molecules of the alignment film have a photofunctional group (photosensitive group) in the side chain of the polymer chain. By this alignment treatment, the photofunctional group forms a dimer by a dimerization reaction, and a bond structure is formed. Will be. In addition, a part of the constituent molecules of the alignment film undergoes cis-trans isomerization by an isomerization reaction by the alignment treatment, and the other part is reoriented.
In this embodiment, each pixel of the first substrate is divided into two alignment processing regions, and light irradiation is performed from opposite directions. Similarly, each pixel of the second substrate is divided into two alignment processing regions, and light is irradiated from opposite directions.
And after performing seal formation, spacer dispersion | distribution, etc., in a board | substrate bonding process, as shown to FIGS. 2-2, the 1st board | substrate and the 2nd board | substrate are bonded so that an orientation process direction may orthogonally cross. Thus, four domains having different twist directions of liquid crystal molecules can be formed in each pixel, that is, the VATN mode liquid crystal display device of this embodiment is a 4VATN mode liquid crystal display device.

Next, liquid crystal molecules having negative dielectric anisotropy are injected between the bonded first substrate and second substrate. Subsequently, the polarizing plate is pasted so that the positional relationship between the orientation direction of the alignment film and the absorption axis of the polarizing plate is as shown in FIG. 2-1 (a) or (b), and the VATN mode liquid crystal display Complete the panel. Further, by performing the mounting process, the VATN mode (4VATN mode) liquid crystal display device of this embodiment can be manufactured.

(Dark line over time)
Here, a description will be given of the results of examining the dark line with time in the above-described 4VATN mode liquid crystal display device.

FIGS. 3-1 to 3-4 are diagrams showing the results of alignment simulation in one pixel of a 4VATN mode liquid crystal display device, and FIG. 3-1 shows the case where the pretilt angle is 87.5 degrees. -2 indicates a case where the pretilt angle is 88.0 degrees, FIG. 3-3 indicates a case where the pretilt angle is 89.0 degrees, and FIG. 3-4 indicates a case where the pretilt angle is 89.9 degrees. In each figure, (a) is the state after 17.5 msec after voltage application, (b) is the state after 25.0 msec after voltage application, and (c) is the state after voltage application in each figure. The state after 100 msec is shown. The alignment simulation was performed under the condition of a cell thickness of 4 μm using a negative liquid crystal material (trade name: MLC2039, manufactured by Merck).

As shown in FIG. 3A to FIG. 3A, dark lines were confirmed in a cross shape in the 4VATN mode liquid crystal display device having any pretilt angle. In the four regions separated by the dark lines, the orientation directions of the liquid crystal molecules are different by about 90 degrees, which enables a wide viewing angle of the liquid crystal display device. Further, in FIGS. 3-1 to 3-4, it was found that the width of the dark line gradually increased as time changed from (a) to (c). This is considered to be because when the pretilt angle is large (89.9 ° or the like), the alignment regulating force of the alignment film in the vicinity of the dark line is insufficient. However, it has been confirmed that as the pretilt angle is smaller, the increase in the width of the dark line accompanying the change with time, that is, the decrease in the area of the light emitting portion is suppressed.

Next, the result of examining the change in transmittance based on the simulation result is shown. FIG. 4 shows a luminance profile (change in transmittance on the A-A ′ line) on the A-A ′ line (that is, 100 msec after voltage application) in FIG. 3C to FIG. The points A and A ′ are points 15 μm apart on the same straight line from the substantially central part of the dark line, and the transmittance at each point is normalized by the transmittance at the points A and A ′. Indicates the value. As shown in FIG. 4, when the pretilt angle is not sufficient (the smaller the pretilt angle is), the transmittance is decreased, and the width of the dark line (distance between two points where the transmittance is 0.9) may be increased. It could be confirmed. More specifically, when the pretilt angle is 87.0 degrees, the dark line width is 10.0 μm, and when the pretilt angle is 88.0 degrees, the dark line width is 10.5 μm. When the angle is 89.0 degrees, the width of the dark line is 11.0 μm, and when the pretilt angle is 89.9 degrees, the width of the dark line is 11.5 μm. This is because the larger the pretilt angle, the greater the energy for aligning the liquid crystal molecules in the parallel direction. When the same voltage is applied to the liquid crystal display devices having different pretilt angles, the liquid crystal display device with the larger pretilt angle has a higher This is presumably because the inclination in the parallel direction is small, that is, the birefringence exhibited by the light transmitted through the liquid crystal layer is small. Here, the width of the dark line is a length between positions that is 90% with respect to the transmittance at point A or point A ′ in the luminance profile of FIG.

Further, FIG. 5 shows a change with time of the transmittance calculated from the result of the orientation simulation. As shown in FIG. 5, in the liquid crystal display device having any pretilt angle, it was found that the transmittance gradually decreased with time after reaching a peak after about 15 msec after voltage application. As a result, in a liquid crystal display device having a large pretilt angle, an afterimage can be seen on the display screen due to a decrease in transmittance.
Further, FIG. 6 shows a change in transmittance decrease defined by T (15) -T (100). FIG. 6 shows the transmittance T (15) after 15 msec (t) after voltage application and the transmittance T (100) after 100 msec (t ′) after voltage application in the time-dependent change in transmittance calculated in the same manner as FIG. The relationship between the difference (transmittance reduction, expressed in%) and the pretilt angle (87.0 to 89.9 °) is shown. As shown in FIG. 6, it was found that the decrease in transmittance was eliminated as the pretilt angle was decreased. Then, when the pretilt angle is larger than 89.5 degrees, the transmittance is drastically decreased, and it has been found that the decrease in transmittance is significantly suppressed particularly when the pretilt angle is 89.5 degrees or less. As described above, in the relationship between the transmittance decrease and the pretilt angle, for example, when the transmittance decrease is 8% (the pretilt angle is 89.5 degrees), it becomes clear that a critical point (conversion point) exists. Thus, it has been found that the value of transmittance reduction that greatly affects the display performance of the liquid crystal display device can be easily controlled. The conversion point was obtained from the inflection point in the differential curve obtained by differentiating the curve indicating the relationship between the transmittance reduction and the pretilt angle in FIG.

As described above, in the present embodiment, when the transmittance decrease is 8% and when the pretilt angle is 89.5 degrees, there is a conversion point, so that the time-dependent change of the dark line width is suppressed. As a means, by reducing the transmittance decrease to 8% or less and the pretilt angle to 89.5 degrees or less, it is possible to easily suppress the decrease in transmittance and the width of the dark line. In a liquid crystal display device, a high aperture ratio can be realized while suppressing the occurrence of display defects such as afterimages.

(Pretilt angle variation)
As an alignment film material, a photodegradable alignment film material is used. As an alignment process by light irradiation, P-polarized light with a wavelength of 254 nm is irradiated for 500 seconds with an intensity of ² mW / cm ² , and the constituent molecules of the light distribution film are photodecomposed Except for the above, alignment treatment by light irradiation was performed in the same manner as in Example 1 to produce a VATN mode (4VATN mode) liquid crystal display panel (hereinafter also referred to as “comparative sample”) for comparison.

The pretilt angle was measured for a plurality of liquid crystal display panels produced by the method of Example 1 or the comparative sample described above. A commercially available tilt angle measuring device (manufactured by Syntex, trade name: Optipro) was used for the measurement of the pretilt angle. As a result of the above measurement, in the liquid crystal display panel having the photocoupled (dimerization) type alignment film produced by the method of Example 1, the pretilt angle was 88.5 ± 0.5 degrees. On the other hand, in the liquid crystal display panel having the photolytic alignment film produced by the method of the comparative sample, the pretilt angle was 88.5 ± 1.0 degrees. According to the measurement apparatus, a value obtained by averaging the pretilt angle in the vicinity of the first alignment film and the pretilt angle in the vicinity of the second alignment film was obtained, but the average of the pretilt angles measured by a plurality of liquid crystal display panels was obtained. When the photo-coupled (dimerization) type alignment film is used (in the case of Example 1), the difference in pretilt angle between the vicinity of the first alignment film and the vicinity of the second alignment film is ± 0. It was found to be within 5 degrees. On the other hand, when a photodegradable alignment film is used (in the case of a comparative sample), the difference in pretilt angle between the vicinity of the first alignment film and the vicinity of the second alignment film may be about ± 1.0 degrees. I understood.
In the present specification, the pretilt angle is an angle formed by the alignment film surface and the major axis direction of the liquid crystal molecules in the vicinity of the alignment film, as shown in FIG. Regardless of whether the voltage is off or on, the angle between the alignment film surface and the major axis direction of the liquid crystal molecules in the vicinity of the alignment film is referred to as a tilt angle or polar angle.

As described above, when the pretilt angle of a liquid crystal molecule is controlled using a material that causes a structure (conformation) change due to a light-sensitive group bonding reaction (dimerization reaction), The variation was as small as ± 0.5 degrees compared to the comparative sample, and a stable pretilt angle could be obtained. This is thought to be because the bonding reaction of the photosensitive group has saturation characteristics with respect to the light irradiation amount.
On the other hand, in the comparative sample, since the pretilt angle of the liquid crystal molecules was controlled using a material that caused a decomposition reaction by light irradiation, the variation in the pretilt angle was ± 1.0 degrees, which was larger than that in Example 1. This is because, in a photodegradation reaction type photo-alignment film, the pretilt tends to tilt as the amount of light irradiation increases, and does not exhibit saturation characteristics, so the variation in the amount of light irradiation directly leads to the variation in the pretilt angle. This is probably because of this.

Next, when the transmittance of the liquid crystal display panel manufactured in Example 1 and the comparative sample was measured, the liquid crystal display panel having the photolytic alignment film manufactured in the comparative sample had a large variation in transmittance. There was found. In order to investigate the cause, a liquid crystal display panel having a photolytic alignment film made of a comparative sample gives the maximum transmittance when the polarizing plates are kept orthogonal to each other and the orientation is rotated only by the panel. It turned out that the direction was shifted. As a result of further examination of this phenomenon, as can be seen from FIG. 13 and the like to be described later, in the VATN mode liquid crystal display device, when the variation in the pretilt angle is large, the orientation direction of the liquid crystal molecules at the center of the panel at the time of voltage application is , It was found to deviate greatly from the 0 degree orientation.

Therefore, from the results of Example 1 and the comparative sample, suppression of variation in the pretilt angle is important for display uniformity in the VATN mode, and as the asymmetry of the pretilt angle increases between the first substrate and the second substrate, It turned out that the fall of the transmittance | permeability becomes large. As a countermeasure, it has been found effective to use a photo-coupled (dimerization) type alignment film.
In particular, when manufacturing a liquid crystal display panel for a television, an alignment film is usually formed on a substrate having a size of 1 m or more in order to increase the size of the liquid crystal television and improve the manufacturing efficiency. Is going. For this reason, it is difficult to completely prevent illuminance unevenness in exposure within the substrate surface, and it is desired to effectively suppress variation in pretilt with respect to illuminance fluctuations.

(Preparation of evaluation sample)
In the alignment treatment by light irradiation in Example 1, the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film and the second alignment film is set to 85 to 90 by changing the light irradiation intensity and the light irradiation time to form the alignment film. A VATN mode liquid crystal display device was manufactured.
In the present invention, the pretilt angle can also be controlled by adjusting the alignment film material, the light irradiation angle, and the like. In the case of the alignment film material, the pretilt angle can be controlled by adjusting the component and number of side chains, the polar group, and the like. In the case of the light irradiation angle, the pretilt angle can be increased by increasing the irradiation angle.
For comparison, a VAECB mode liquid crystal display device in which the pretilt angle of liquid crystal molecules in the vicinity of the first alignment film and the second alignment film was set to 85 to 90 degrees was manufactured.

(Relationship between pretilt angle and contrast ratio)
FIG. 4 shows the relationship between the pretilt angle and the contrast ratio in the above-described VATN mode liquid crystal display device and VAECB mode liquid crystal display device. FIG. 8 shows the case where the pretilt angles of the liquid crystal molecules are the same in the vicinity of the first alignment film and in the vicinity of the second alignment film.
As shown in FIG. 8, when the pretilt angles of the liquid crystal molecules are the same in the vicinity of the first alignment film and in the vicinity of the second alignment film, the VATN mode is advantageous in obtaining a higher contrast ratio than the VAECB mode. In other words, in the VATN mode, when the pretilt angle is decreased, the contrast ratio decrease is smaller than in the VAECB mode, and when the pretilt angle is 86.5 degrees or more, the contrast ratio decrease is 10% or less with respect to the maximum contrast ratio. Can be suppressed. This is because in the VAECB mode, a slight change in retardation caused by reducing the pretilt angle of the liquid crystal molecules causes light leakage in the black display (off state). In the VATN mode, the first alignment film and the second alignment film It is considered that this is because minute changes in retardation are canceled each other because the orientation directions of the alignment films are orthogonal.
Accordingly, it is generally known that in the VA mode, the response speed from the off state to the on state can be improved by reducing the pretilt angle of the liquid crystal molecules (increasing the tilt angle). In the mode, since the decrease in contrast ratio is small even if the pretilt angle is reduced, it can be said that the mode is more advantageous than the VAECB mode in terms of improving the response speed.

(Relationship between pretilt angle and voltage-transmittance curve)
FIG. 9 shows how the voltage-transmittance curve changes when the pretilt angle is changed in the above-described VATN mode liquid crystal display device and VAECB mode liquid crystal display device. FIG. 9 shows a case where the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film is fixed to 88.5 degrees. Further, in the above-described VATN mode liquid crystal display device and VAECB mode liquid crystal display device, the transmittance at 6.2 V changes when the pretilt angle of the liquid crystal molecules in the vicinity of the second alignment film is changed. This is shown in FIG. FIG. 10 shows the case where the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film is fixed at 88.5 degrees.
In the VATN mode, when the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film is changed to 88.5 degrees and the pretilt angle of the liquid crystal molecules in the vicinity of the second alignment film is changed, as shown in FIG. Thus, when the angle is 88.5 degrees, the rise characteristic of the transmittance with respect to the voltage change is excellent, and as shown in FIG.
On the other hand, in the VAECB mode, when the pretilt angle of the liquid crystal molecules in the vicinity of the second alignment film is changed while the pretilt angle of the liquid crystal molecules in the vicinity of the first alignment film is fixed at 88.5 degrees, FIG. As shown in FIG. 10 and FIG. 10, the rise characteristic of the transmittance with respect to the voltage change hardly changes.
As described above, in the VATN mode, when the difference in pretilt angle between the first alignment film and the second alignment film is large, the transmittance is greatly reduced compared to the VAECB mode, and the control of the pretilt angle improves the display characteristics. It turns out that it is extremely important in making it happen. According to FIG. 10, in the VATN mode, a high transmittance is stably obtained when the pretilt angle of the liquid crystal molecules in the vicinity of the second alignment film is 87.5 to 89.0 degrees. Therefore, the difference in pretilt angle between the liquid crystal molecules near the first alignment film and the second alignment film is set to 1.0 degrees or less, and the pretilt between the liquid crystal molecules near the first alignment film and the second alignment film. It can be seen that the angle is preferably 89 degrees or less.

(Relationship between pretilt angle and liquid crystal molecule behavior)
Regarding the above-mentioned VATN mode liquid crystal display device and VAECB mode liquid crystal display device, the orientation of liquid crystal molecules in the off state (liquid crystal layer applied voltage: 1.5 V) and the on state (liquid crystal layer applied voltage: 6.2 V) The orientation of the liquid crystal molecules in is shown in FIGS.

FIG. 11 shows a case where the pretilt angle in the vicinity of the first alignment film is 88.5 degrees and the pretilt angle in the vicinity of the second alignment film is 88.5 degrees in the VATN mode. b) shows the ON state. As shown in FIG. 11A, in the off state where the voltage applied between the substrates sandwiching the liquid crystal layer is less than the threshold voltage, the polar angle of the liquid crystal molecules (the tilt angle of the liquid crystal molecules with respect to the substrate surface) is 88. The azimuth angle of the liquid crystal molecules changes at a constant rate from −45 degrees to +45 degrees from the first substrate to the second substrate. On the other hand, as shown in FIG. 11B, in the ON state where the voltage applied between the substrates sandwiching the liquid crystal layer exceeds the threshold voltage, the polar angle of the liquid crystal molecules is in the vicinity of the first alignment film and the second alignment film. In the vicinity of the alignment film, the alignment film maintains the substantially vertical alignment, but in the central portion far from the alignment film, the alignment film changes to a substantially horizontal alignment by the voltage applied to the liquid crystal layer. At this time, the azimuth angle of the liquid crystal molecules greatly changes at substantially the same rate in the vicinity of the first alignment film and in the vicinity of the second alignment film, and is constant from the first substrate toward the second substrate in the central portion far from the alignment film. Shows a small change at a rate of. This is because substantially vertical alignment is maintained in the vicinity of the first alignment film and in the vicinity of the second alignment film, and the azimuth angle can be changed with less energy than the central portion far from the alignment film by twisting the liquid crystal molecules. This is probably because of this. Further, since the pretilt angles are the same in the vicinity of the first alignment film and in the vicinity of the second alignment film, the change in azimuth angle (twist of liquid crystal molecules) is symmetric between the first substrate side and the second substrate side. It is possible to obtain a high transmittance.

FIGS. 12 and 13 show a case where the pretilt angle near the first alignment film is 89.0 degrees or 89.5 degrees and the pretilt angle near the second alignment film is 88.5 degrees in the VATN mode. a) shows an off state, and (b) shows an on state. As shown in FIGS. 12A and 13A, in the off state, the polar angle of the liquid crystal molecules is 89.0 degrees or 89.5 degrees to 88.88 from the first substrate toward the second substrate. It changes at an almost constant rate up to 5 degrees. In addition, the azimuth angle of the liquid crystal molecules changes from −45 degrees to +45 degrees with a slight increase on the first substrate side from the first substrate toward the second substrate. On the other hand, as shown in FIGS. 12B and 13B, in the ON state, the polar angle of the liquid crystal molecules is maintained in a substantially vertical alignment by the alignment film in the vicinity of the first alignment film and in the vicinity of the second alignment film. However, in the central portion far from the alignment film, the alignment is changed to a substantially horizontal alignment by the voltage applied to the liquid crystal layer. At this time, the azimuth angle of the liquid crystal molecules changes in the vicinity of the first alignment film having a large polar angle at a larger rate than in the vicinity of the second alignment film. Thus, when the pretilt angle is different between the vicinity of the first alignment film and the vicinity of the second alignment film, the change in the azimuth angle (the twist of the liquid crystal molecules) is symmetric between the first substrate side and the second substrate side. Therefore, the transmittance is reduced.

FIG. 14 shows a case where the pretilt angle in the vicinity of the first alignment film is 89.5 degrees and the pretilt angle in the vicinity of the second alignment film is 88.5 degrees in the VAECB mode. b) shows the ON state. As shown in FIG. 14A, in the off state, the polar angle of the liquid crystal molecules changes from a first substrate to a second substrate at a substantially constant rate from 89.5 degrees to 88.5 degrees. ing. On the other hand, as shown in FIG. 14B, in the ON state, the polar angle of the liquid crystal molecules is maintained in a substantially vertical alignment by the alignment film in the vicinity of the first alignment film and in the vicinity of the second alignment film. In the central portion far from the film, the orientation changes to a substantially horizontal orientation by the voltage applied to the liquid crystal layer. The azimuth angle of the liquid crystal molecules is constant at 0 degrees in both the off state and the on state. For this reason, in the case of the VAECB mode, the behavior of the liquid crystal molecules does not basically change due to the difference in the pretilt angle of the liquid crystal molecules between the vicinity of the first alignment film and the vicinity of the second alignment film, as shown in FIG. The transmittance hardly changes.

2A and 2B are conceptual diagrams illustrating a driving principle of the VATN mode liquid crystal display device according to the first embodiment, in which FIG. 3A illustrates an off state and FIG. 3B illustrates an on state; It is a conceptual diagram which shows the positional relationship of the orientation azimuth | direction of the orientation film | membrane and the absorption axis of a polarizing plate in one domain contained in the liquid crystal display device of the VATN mode of Example 1, (a) and (b) are position, respectively. An example of the relationship is shown. FIG. 3 is a conceptual diagram illustrating a relationship between four domains in one pixel included in the VATN mode liquid crystal display device of Example 1 and an alignment direction of an alignment film. It is a figure which shows the result of the orientation simulation in one pixel of the liquid crystal display device of 4VATN mode whose pretilt angle is 87.5 degree, (a) is the state after 17.5 msec after voltage application, (b) is voltage The state after 25.0 msec after application, (c) shows the state after 100 msec after voltage application. It is a figure which shows the result of the orientation simulation in one pixel of the 4VATN mode liquid crystal display device whose pretilt angle is 88.0 degree | times, (a) is the state after 17.5 msec after voltage application, (b) is voltage The state after 25.0 msec after application, (c) shows the state after 100 msec after voltage application. It is a figure which shows the result of the orientation simulation in one pixel of the 4VATN mode liquid crystal display device whose pretilt angle is 89.0 degree | times, (a) is the state after 17.5 msec after voltage application, (b) is voltage The state after 25.0 msec after application, (c) shows the state after 100 msec after voltage application. It is a figure which shows the result of the orientation simulation in the pixel of 4VATN mode liquid crystal display device whose pretilt angle is 89.9 degree | times, (a) is the state after 17.5 msec after voltage application, (b) is voltage The state after 25.0 msec after application, (c) shows the state after 100 msec after voltage application. It is a figure which shows the luminance profile (change of the transmittance | permeability in an A-A 'line) in the A-A' line (namely, 100 msec after voltage application) in (c) of FIGS. 3-1 to 3-4. The points A and A ′ are points 15 μm apart on the same straight line from the substantially central part of the dark line, and the transmittance is a value normalized by the transmittance at the points A and A ′. . It is a figure which shows the time-dependent change of the transmittance | permeability computed from the result of the orientation simulation. The difference between the transmittance after 15 msec (t) after voltage application and the transmittance after 100 msec (t ′) after voltage application (transmission decrease) and the pretilt angle (87 .0 to 89.9 °). It is a conceptual diagram for demonstrating the pretilt angle of a liquid crystal molecule. It is a graph which shows the relationship between a pretilt angle and contrast ratio about the liquid crystal display device of VATN mode, and the liquid crystal display device of VAECB mode. FIG. 5 is a graph showing how the voltage-transmittance curve changes when the pretilt angle is changed for a VATN mode liquid crystal display device and a VAECB mode liquid crystal display device, where (a) is a VATN mode; (b) Indicates VAECB mode. 6 is a graph showing how the transmittance at 6.2 V changes when the pretilt angle of liquid crystal molecules in the vicinity of the second alignment film is changed for a VATN mode liquid crystal display device and a VAECB mode liquid crystal display device. . The VATN mode liquid crystal display device shows the alignment of liquid crystal molecules when the pretilt angle near the first alignment film is 88.5 degrees and the pretilt angle near the second alignment film is 88.5 degrees, (a) Indicates an off state, and (b) indicates an on state. The VATN mode liquid crystal display device shows the alignment of liquid crystal molecules when the pretilt angle near the first alignment film is 89.0 degrees and the pretilt angle near the second alignment film is 88.5 degrees, (a) Indicates an off state, and (b) indicates an on state. For the VATN mode liquid crystal display device, the alignment of liquid crystal molecules when the pretilt angle near the first alignment film is 89.5 degrees and the pretilt angle near the second alignment film is 88.5 degrees is shown. (A) Indicates an off state, and (b) indicates an on state. The liquid crystal display device in the VAECB mode shows the alignment of liquid crystal molecules when the pretilt angle near the first alignment film is 89.5 degrees and the pretilt angle near the second alignment film is 88.5 degrees, (a) Indicates an off state, and (b) indicates an on state. It is a conceptual diagram explaining the drive principle of the liquid crystal display device of VAECB mode, (a) shows an OFF state, (b) has shown the ON state. It is a conceptual diagram which shows the positional relationship of the orientation azimuth | direction of the orientation film in one domain contained in the VAECB mode liquid crystal display device, and the absorption axis of a polarizing plate. It is a conceptual diagram which shows the relationship between the four domains in one pixel contained in the VAECB mode liquid crystal display device, and the orientation azimuth of the orientation film.

Explanation of symbols

1: first alignment film 1a: first alignment film orientation direction 2: second alignment film 2a: second alignment film alignment direction 3: liquid crystal molecule 4: pretilt angle 5: first polarizing plate absorption axis 6: second Polarizing plate absorption axis 7: liquid crystal layer

Claims (7)

A first substrate and a second substrate; a liquid crystal layer provided between the substrates; a first alignment film provided on a surface of the first substrate on a liquid crystal layer side; and a surface of the second substrate on a liquid crystal layer side A second alignment film provided on the liquid crystal display device,
The liquid crystal layer is configured to include liquid crystal molecules having negative dielectric anisotropy,
The first alignment film and the second alignment film align liquid crystal molecules in the vicinity thereof in an orientation that is substantially perpendicular to the alignment film surface and orthogonal to each other, and the alignment directions of the liquid crystal molecules in the vicinity thereof are different. Have two or more areas per pixel,
The liquid crystal display device is provided with a dark line width aging change suppressing means. The dark line width change with time control means T (15) −T, where T (15) is the transmittance after 15 milliseconds from the voltage application and T (100) is the transmittance after 100 milliseconds. The transmittance decrease defined by (100) is set to be equal to or less than a conversion point in the relationship between the transmittance decrease and the pretilt angles of liquid crystal molecules in the vicinity of the first alignment film and the second alignment film. The liquid crystal display device described. 2. The liquid crystal display device according to claim 1, wherein the dark line width temporal change suppressing means sets a pretilt angle of liquid crystal molecules in the vicinity of the first alignment film and the second alignment film to 89.5 degrees or less. 2. The liquid crystal display device according to claim 1, wherein a difference in pretilt angle of liquid crystal molecules is less than 1.0 degrees between the vicinity of the first alignment film and the vicinity of the second alignment film. 2. The liquid crystal display device according to claim 1, wherein a pretilt angle of liquid crystal molecules in the vicinity of the first alignment film and the second alignment film is 89 degrees or less. The first alignment film and / or the second alignment film includes at least one photosensitive group selected from the group consisting of a 4-chalcone group, a 4′-chalcone group, a coumarin group, and a cinnamoyl group, or a bonding structure thereof. The liquid crystal display device according to claim 1. A method of manufacturing a liquid crystal display device according to claim 1,
The manufacturing method converts a decrease in transmittance defined by T (15) -T (100) into a conversion point in the relationship between the decrease in transmittance and the pretilt angles of liquid crystal molecules in the vicinity of the first alignment film and the second alignment film. In order to achieve the following, a method for manufacturing a liquid crystal display device, including a step of forming a first alignment film and a second alignment film in which a pretilt angle of liquid crystal molecules in the vicinity of the alignment film is 89.5 degrees or less.