WO2012063936A1

WO2012063936A1 - Liquid crystal display device and method for manufacturing liquid crystal display device

Info

Publication number: WO2012063936A1
Application number: PCT/JP2011/076057
Authority: WO
Inventors: 健史野間; 真伸水▲崎▼; 仲西　洋平
Original assignee: シャープ株式会社
Priority date: 2010-11-11
Filing date: 2011-11-11
Publication date: 2012-05-18

Abstract

The present invention provides a liquid crystal display device capable of suppressing degradation of the display characteristics such as a decrease in the aperture ratio and a decrease in the contrast ratio, and capable of suppressing the white spot phenomenon. One aspect of the present invention is a liquid crystal display device equipped with a pair of substrates and a liquid crystal layer sandwiched between said pair of substrates, wherein the aforementioned liquid crystal layer has a negative dielectric constant anisotropy, and at least one substrate of the aforementioned pair of substrates has an electrode, an orientation film that orients the adjacent liquid crystal molecules vertically, and a polymer layer that is formed by one or more types of bifunctional monomers on a portion of the main face of the aforementioned orientation film on the liquid crystal layer side, and that controls the orientation of the adjacent liquid crystal molecules. In addition, within the pixels there exists a first orientation region, wherein the aforementioned orientation film and the liquid crystal molecules are in contact, and a second orientation region, wherein the aforementioned polymer layer and the liquid crystal molecules are in contact, with the aforementioned first orientation region and the aforementioned second orientation region having different threshold voltages.

Description

Liquid crystal display device and method of manufacturing liquid crystal display device

The present invention relates to a liquid crystal display device and a method for manufacturing the liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device in which a polymer layer is formed on an alignment film in order to increase the alignment regulating force of liquid crystal, and a method for manufacturing a liquid crystal display device that can suitably form a polymer layer.

A liquid crystal display device is a display panel that controls light transmission / blocking (display on / off) by controlling the orientation of liquid crystal molecules having birefringence. As a technique for aligning liquid crystal molecules, for example, a rubbing method is used in which after an alignment film material is applied, grooves are formed by a roller or the like to form an alignment film.

Further, as in a multi-domain vertical alignment (MVA) mode, alignment control structures such as a bank-like protrusion formed of a dielectric provided on the electrode and a slit provided on the electrode After applying an alignment film material having a photo-alignment functional group instead of rubbing treatment, such as a method for controlling the alignment of liquid crystal molecules using UV and UV ² A (Ultraviolet induced multi-domain Vertical Alignment) technology A method of forming an alignment film by irradiating light is also known.

In a liquid crystal display device in the MVA mode, liquid crystal molecules are aligned perpendicular to the substrate surface when no voltage is applied. When a voltage is applied between the pixel electrode and the common electrode, the liquid crystal molecules become a voltage. It is tilted and oriented at an appropriate angle. At this time, a plurality of regions (domains) in which the directions in which the liquid crystal molecules fall are different from each other are formed in one pixel by slits or bank-like protrusions provided on the electrodes. Thus, by forming a plurality of domains in one pixel, good display characteristics can be obtained.

However, in a conventional MVA mode liquid crystal display device or a liquid crystal display device to which the UV ² A technology is applied, a phenomenon in which the screen looks whitish when viewed from an oblique direction (hereinafter also referred to as “whiteout”) in a halftone. .) May occur. FIG. 8 is a diagram showing the relationship between relative luminance and gradation in a conventional liquid crystal display device. FIG. 8 shows the relationship between relative luminance and gradation when the screen is viewed from the front (viewing angle 0 °) and obliquely (viewing angles 30 ° and 60 °). As shown in FIG. 8, in the halftone, the relative luminance is higher when viewed from an oblique direction than when the screen is viewed from the front. As a result, in halftone, white spots occur when the screen is viewed from an oblique direction. This is because the VT (voltage-transmittance) characteristics when viewed from the oblique direction and when viewed from the front direction are different, and the transmittance when viewed from the oblique direction is different from that from the front direction. This is because it becomes higher than the transmittance.

As a method for improving this white spot, it is also referred to as a technique (hereinafter referred to as “MPD (Multi-Pixel-Drive) technique) that controls gradation expression in cell units obtained by further dividing each RGB dot constituting one pixel into two. )It has been known.

In addition to the above MPD technology, as a method of improving white spots, a liquid crystal material containing a monomer is injected between substrates, the monomer is polymerized in a state where a voltage is applied, and a polymer in which the direction in which the liquid crystal molecules fall is memorized is stored. Is known ("PSA (Polymer Sustained Alignment) technology")) (see, for example, Patent Document 1).

9 is a schematic cross-sectional view of the liquid crystal display device according to Patent Document 1 before the polymerization process, and FIG. 10 is a schematic cross-sectional view of the liquid crystal display device according to Patent Document 1 after the polymerization process. As shown in FIG. 9, the array substrate 110 has a protrusion 115. The monomer 105 is present in the liquid crystal layer 130 before the polymerization step. In the light irradiation step, the liquid crystal layer 130 is irradiated with ultraviolet light from the side of the array substrate 110 on which the light shielding mask 125 is formed while a predetermined voltage is applied to the liquid crystal layer 130 through the

electrodes

113 and 123, and the polymerization of the monomer 105 is performed. Be started. The light shielding mask 125 is formed on the array substrate 110 so as to cover approximately half of one pixel. The monomer 105 present in the region not shielded by the light shielding mask 125 is polymerized. Thereafter, the light shielding mask 125 is removed, the entire surface of the liquid crystal panel is irradiated with ultraviolet light, and the monomer 105 remaining in the liquid crystal layer 130 is polymerized. As a result, the first polymer 126 having a strong binding force on the liquid crystal molecules is formed in the region not exposed to light shielding by the light shielding mask 125 (exposure region), while the region shielded by the light shielding mask 125 (light shielding region) is formed. The second polymer 127 having a weak binding force on the liquid crystal molecules is formed. As a result, a region having a strong binding force on the liquid crystal molecules (that is, a region having a high threshold voltage) and a region having a low binding force on the liquid crystal molecules (that is, a region having a low threshold voltage) are formed within one pixel. Can be suppressed.

JP 2006-267689 A

However, the above-described method for improving white spots may cause an increase in manufacturing cost and a decrease in display characteristics. For example, MPD technology requires a structure for changing the voltage applied in the dot. For this reason, there are disadvantages in that the manufacturing cost increases and the aperture ratio decreases due to an increase in wiring and the like.

Further, in the liquid crystal display device according to Patent Document 1 described above, the protrusion is used, but it is difficult to use the region where the protrusion is disposed for display. For this reason, there was room for improvement in terms of increasing the aperture ratio and improving the luminance. Moreover, since the alignment of the liquid crystal molecules is affected by the protrusions not only in the region where the protrusions are disposed but also in the vicinity thereof, it is difficult to control the alignment to a desired orientation. For this reason, there was room for improvement in terms of improving contrast. Moreover, in the liquid crystal display device according to Patent Document 1, since a voltage is applied when polymerization is performed, there is room for improvement in that the manufacturing cost is increased.

The present invention has been made in view of the above situation, and viewed the screen obliquely in a halftone while suppressing deterioration of other display characteristics conventionally seen such as a decrease in aperture ratio and a decrease in contrast ratio. An object of the present invention is to provide a liquid crystal display device capable of suppressing the occurrence of a so-called white spot phenomenon in which the brightness at the time is higher than the brightness when the screen is viewed from the front, and a method for manufacturing the liquid crystal display device Is.

The present inventors paid attention to the PSA technology as a method for suppressing the white spot phenomenon, and conducted intensive studies on monomers used in the PSA technology. As a result, it has been found that by forming a polymer layer using a bifunctional monomer on the vertical alignment film, it is possible to adjust the threshold voltage of a region whose orientation is controlled by the polymer layer. Then, the inventors have arrived at the present invention by conceiving that the above problem can be solved by changing the threshold voltage between the region controlled by the polymer layer and the region not controlled by the polymer layer. is there.

That is, one aspect of the present invention is a liquid crystal display device including a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates, the liquid crystal layer having negative dielectric anisotropy. And at least one of the pair of substrates is a main surface on the liquid crystal layer side of the alignment film by polymerization of an electrode, an alignment film for vertically aligning adjacent liquid crystal molecules, and at least one bifunctional monomer. A first alignment region in which the alignment layer and the liquid crystal molecule are in contact with each other, and a second alignment region in which the polymer layer and the liquid crystal molecule are in contact with each other. In the liquid crystal display device, the first alignment region and the second alignment region have different threshold voltages.

In the liquid crystal display device, a bifunctional monomer is used as a material for the polymer layer. The bifunctional monomer is not particularly limited as long as it is a monomer having two reactive functional groups. Examples of the reactive functional group include a functional group containing an unsaturated bond such as a double bond. Compared with a polymer layer using a monofunctional monomer, a polymer layer using a bifunctional monomer (1) can maintain a sufficient pretilt angle, and thus has high reliability, and (2) a polymerization rate. For example, photopolymerization is excellent in that the exposure time can be shortened, productivity can be improved, and / or manufacturing cost can be reduced. Further, the bifunctional monomer is superior in solubility in liquid crystal as compared with a polyfunctional monomer having three or more reactive functional groups, and it is easy to form a polymer layer.

The alignment film whose vertical alignment is controlled means an alignment film capable of realizing a liquid crystal display in a vertical alignment mode, and the liquid crystal molecules are only aligned perpendicularly to the film surface, that is, an alignment film that controls the alignment at 90 °. And an alignment film that controls the alignment of liquid crystal molecules substantially perpendicular to the film surface. Substantially perpendicular means 80 ° or more, preferably 85 ° or more.

The threshold voltage means a voltage value that generates an electric field that causes an optical change in the liquid crystal layer and changes a display state in the liquid crystal display device.

The difference between the threshold voltage difference of the first alignment region and the threshold voltage of the second alignment region is preferably 0.1 V or more, and more preferably 0.5 V to 1.5 V. .

In order to make the threshold voltage different between the first alignment region and the second alignment region, the pretilt angle of the liquid crystal molecules in each alignment region may be different. In addition, the threshold voltage can be made different by changing the anchoring strength in each alignment region. FIG. 11 is a diagram showing a change in a VT (voltage-transmittance) curve due to a difference in pretilt angle. As shown in FIG. 11, the threshold voltage increases as the pretilt angle increases.

The configuration of the liquid crystal display device is not particularly limited by other components as long as such components are essential.

Hereinafter, preferred embodiments of the liquid crystal display device will be described in more detail.

As one of the preferable embodiments, the alignment film may be formed by irradiating polarized ultraviolet light to an alignment film material containing a photoreactive functional group (hereinafter, also referred to as a first embodiment). . Since the pretilt angle can be adjusted accurately by using polarized ultraviolet light, the liquid crystal display device of the first embodiment can be a photo-alignment type liquid crystal display device with excellent display quality.

In the first embodiment, the photoreactive functional group is preferably at least one selected from the group consisting of a chalcone group, a coumarin group, a cinnamate group, an azobenzene group, and a tolan group. When a polymer layer is formed using such a monomer having a photoreactive functional group, the orientation control can be performed with high accuracy. Therefore, the photoreactive functional group included in the group is aligned by irradiation with polarized ultraviolet light. The liquid crystal display device including the alignment film to be processed can be particularly preferably used.

As one of the preferable forms, there is a form in which the pretilt angle of the liquid crystal molecules in the first alignment region and the pretilt angle of the liquid crystal molecules in the second alignment region are different from each other. When the pretilt angle of the liquid crystal molecules in the first alignment region is different from the pretilt angle of the liquid crystal molecules in the second alignment region, the threshold voltages of the respective alignment regions are different, thereby suppressing white spots. be able to. Specifically, the difference between the pretilt angle of the liquid crystal molecules in the first alignment region and the pretilt angle of the liquid crystal molecules in the second alignment region is preferably about 0.5 ° to 15 °. . The pretilt angle of the liquid crystal molecules in the first alignment region is preferably 88.0 ° to 88.5 °, and the pretilt angle of the liquid crystal molecules in the second alignment region is 73.0 ° to 87. Preferably it is 5 °.

The pretilt angle of the liquid crystal molecules in the first alignment region is preferably larger than the pretilt angle of the liquid crystal molecules in the second alignment region. Since the pretilt angle of the liquid crystal molecules in the first alignment region is close to 90 °, the pretilt angle of the liquid crystal molecules in the second alignment region is larger than the pretilt angle of the liquid crystal molecules in the first alignment region. Is too large, the difference between the pretilt angle of the liquid crystal molecules in the first alignment region and the pretilt angle of the liquid crystal molecules in the second alignment region cannot be taken sufficiently, and a desired threshold voltage difference is obtained. May not be obtained.

The area of the second alignment region is preferably larger than 30% and smaller than 70% compared to the sum of the area of the first alignment region and the area of the second alignment region. If the area of the second alignment region is 30% or less, the area of the first alignment region is too large compared to the area of the second alignment region, so that white spots can be sufficiently suppressed. There is a risk that it will not be possible. On the other hand, if the area of the second alignment region is 70% or more, the area of the first alignment region is too small compared to the area of the second alignment region. You may not be able to do it. More preferably, the area of the first alignment region and the area of the second alignment region are substantially equal. Specifically, the second alignment region includes the first alignment region and the first alignment region. More preferably, it is larger than 45% and smaller than 55% compared with the total with the second alignment region.

The bifunctional monomer is preferably represented by the following chemical structural formula.
P ¹ -A ^1- (Z ¹ -A ² ) _n -P ²
(In the formula, P ¹ and P ² (reactive functional groups) each independently represent an acrylate group, a methacrylate group, a vinyl group, a vinyloxy group, or an epoxy group. A ¹ and A ² are each independently Represents a 1,4-phenylene group, a naphthalene-2,6-diyl group, an anthracene-2,6-diyl group, or a phenanthrene-2,7-diyl group, and the hydrogen atom contained in the ring structure is halogen, Z ¹ may be COO, OCO, O, CO, NHCO, CONH, S, or A, which may be substituted with a methyl group, an ethyl group, or a propyl group, and may be a heterocyclic structure. ¹ and A ² or A ² and A ² are directly bonded. N is 0, 1 or 2.)

The bifunctional monomer preferably has a dinaphthyl ether skeleton. Examples of the dinaphthyl ether skeleton include dinaphthyl ether skeletons represented by the following chemical formulas (1) to (4), and dimethacryloxy dinaphthyl ether represented by the following chemical formula (4) is particularly preferable. A polymer layer formed of a bifunctional monomer having a dinaphthyl ether skeleton can reduce the pretilt angle. Furthermore, the amount of change in the pretilt angle can be increased by increasing the concentration of the bifunctional monomer. As a result, it becomes easy to control the pretilt angle in the second alignment region at an angle suitable for suppressing white spots, and the threshold voltage of the second alignment region is different from the threshold voltage of the first alignment region. Therefore, it is possible to adjust so that white spots can be suitably suppressed.

Another aspect of the present invention is a method for manufacturing a liquid crystal display device comprising a pair of substrates and a liquid crystal layer having negative dielectric anisotropy sandwiched between the pair of substrates, the manufacturing method comprising: A step of forming an electrode on at least one of the pair of substrates, a step of forming an alignment film for controlling alignment of adjacent liquid crystal molecules vertically, and a part of a main surface on the liquid crystal side of the alignment film, Forming a polymer layer for controlling the alignment of adjacent liquid crystal molecules, wherein the polymer layer is formed by shielding a part of at least one of the pair of substrates by a light shielding member, In a state where the portion is not shielded from light, the bifunctional monomer added to the liquid crystal layer is polymerized by irradiating light, and the first alignment region where the alignment film and the liquid crystal molecule are in contact with each other, the polymer layer and the liquid crystal molecule A second alignment region in contact with the pixel A step of forming, wherein the first alignment region and the second alignment region, there is also a method for producing a threshold voltage having different liquid crystal display device.

The light shielding member is formed on one substrate so as to cover a part of one pixel region, for example. By irradiating light toward the substrate on which the light shielding member is formed, a region that is not shielded by the light shielding member and a region that is shielded from light are generated in one pixel region. In the non-shielded region, the bifunctional monomer is polymerized by light irradiation, and the polymer layer is formed on the alignment film. As a result, a second alignment region in which the alignment of liquid crystal molecules is controlled by the polymer layer is formed in the pixel. On the other hand, the bifunctional monomer is not substantially polymerized in the light shielding region. As a result, a first alignment region in which the alignment of liquid crystal molecules is controlled by the alignment film is formed. Since the alignment regulating forces of the polymer layer and the alignment film are different from each other, the first alignment region and the second alignment region have different threshold voltages. Thus, according to the manufacturing method of the liquid crystal display device, the liquid crystal display device can be preferably manufactured.

The configuration of the manufacturing method of the liquid crystal display device is not particularly limited by other components and processes as long as such components and processes are formed as essential.
A preferred embodiment of the method for manufacturing the liquid crystal display device will be described below.

In the step of polymerizing the bifunctional monomer, the alignment film controls the pretilt angle of liquid crystal molecules, the light shielding member shields a part of the pixel, and the light irradiation is performed without applying a voltage to the liquid crystal layer. And performing photopolymerization of the bifunctional monomer to form the polymer layer, wherein the pretilt angle of the liquid crystal molecules in the first alignment region is greater than the pretilt angle of the liquid crystal molecules in the second alignment region. Is preferably a large value. In this aspect, voltage application is not necessary, so that an increase in manufacturing cost can be suppressed. Further, the difference between the pretilt angle of the liquid crystal molecules in the first alignment region and the pretilt angle of the liquid crystal molecules in the second alignment region is set to a desired value, and the difference in threshold voltage is set to a desired value. Becomes easy.

The region that is not shielded by the light shielding member is preferably larger than 30% and smaller than 70% compared to all the regions where the liquid crystal is orientation controlled. If the volume of the second alignment region is 30% or less, the volume of the first alignment region is too large compared to the volume of the second alignment region, so that white spots can be sufficiently suppressed. There is a risk that it will not be possible. On the contrary, when the volume of the second alignment region is 70% or more, the volume of the first alignment region is too small compared to the volume of the second alignment region, so that white spots are sufficiently suppressed. You may not be able to do it. More preferably, the volume of the first alignment region is substantially equal to the volume of the second alignment region. Specifically, it is more preferable that the second alignment region is larger than 45% and smaller than 55% as compared with the total of the first alignment region and the second alignment region.

According to the liquid crystal display device, it is not necessary to form protrusions on the substrate, and it is not necessary to provide MPD wiring or the like, and the first alignment region and the second alignment region having different threshold voltages can be formed. Therefore, it is possible to obtain a liquid crystal display device that is low in cost and has a high aperture ratio while suppressing white spots.

FIG. 3 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 before the polymerization step. FIG. 3 is a schematic cross-sectional view after the polymerization step of the liquid crystal display device according to the first embodiment. FIG. 3 is a schematic plan view showing a state in which light shielding masks are arranged to overlap in one pixel region of the array substrate of the liquid crystal display device according to the first embodiment. FIG. 6 is a diagram showing measurement results of pretilt angles in Test Examples 1 to 3 and Comparative Example 1. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 2 before a polymerization process. FIG. FIG. 6 is a schematic cross-sectional view after a polymerization process of a liquid crystal display device according to Embodiment 2. It is a figure which shows the measurement result of the pretilt angle in Test Examples 2, 4, and 5. It is a figure which shows the relationship between the relative brightness | luminance and the gradation in the conventional liquid crystal display device. It is a cross-sectional schematic diagram before the superposition | polymerization process of the liquid crystal display device which concerns on patent document 1. It is a cross-sectional schematic diagram after the superposition | polymerization process of the liquid crystal display device which concerns on patent document 1. It is a figure which shows the change of the VT (voltage-transmittance) curve by the difference in a pretilt angle.

Embodiments will be described below, and the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.

Embodiment 1
In Embodiment 1, one type of bifunctional monomer is used to form the polymer layer. Hereinafter, the polymer layer is also referred to as a PSA (Polymer Sustained Alignment) film. Examples of the bifunctional monomer used to form the PSA film in Embodiment 1 include those represented by the above chemical formulas (1) to (4).

Hereinafter, the liquid crystal display device according to Embodiment 1 will be described in detail. FIG. 1 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 before the polymerization step, and FIG. 2 is a schematic cross-sectional view of the liquid crystal display device according to Embodiment 1 after the polymerization step. 1 and 2 are also schematic cross-sectional views of one pixel region of the liquid crystal display device. FIG. 3 is a schematic plan view showing a state in which light shielding masks are arranged to overlap in one pixel region of the array substrate of the liquid crystal display device according to the first embodiment. As shown in FIGS. 1 and 2, the liquid crystal display device of Embodiment 1 is a liquid crystal cell in which an array substrate 10, a liquid crystal layer 30, and a color filter substrate 20 are arranged from the back side of the liquid crystal display device toward the observation surface side. It has. The liquid crystal layer 30 sandwiched between a pair of substrates including the array substrate 10 and the color filter substrate 20 has negative dielectric anisotropy. A linear polarizing plate is provided on the back side of the array substrate 10 and the observation surface side of the color filter substrate 20. For these linearly polarizing plates, a retardation plate may be further arranged to form a circularly polarizing plate.

As shown in FIG. 3, in the liquid crystal display device according to the first embodiment, a plurality of pixels are arranged in a matrix or delta form to constitute one display surface. The array substrate 10 includes various wirings, a thin film transistor (TFT) 44 and the like on an insulating transparent substrate 11 made of glass or the like. Specifically, as shown in FIG. 3, the array substrate 10 includes a plurality of gate wirings 45 and auxiliary capacitance (Cs) wirings 43. The plurality of gate lines 45 and the auxiliary capacitance (Cs) lines 43 extend in parallel to each other. The array substrate 10 further includes a plurality of source lines 42 that intersect with the gate lines 45 and the auxiliary capacitance (Cs) lines 43 and extend in parallel to each other, and are provided in the vicinity of each intersection of the gate lines 45 and the source lines 42. TFT 44 is provided. In each pixel (pixel region), a pixel electrode 13 having a substantially rectangular shape is arranged.

The color filter substrate 20 includes an insulating transparent substrate 21 made of glass or the like, and a common electrode 23, a color filter, a black matrix, and the like formed on the transparent substrate 21.

Examples of the method for forming the pixel electrode 13 and the common electrode 23 include a sputtering method, a chemical vapor deposition (CVD) method, and a vapor deposition method. For example, the pixel electrode 13 can be patterned into a shape having a slit or a comb shape by using a photolithography method, but the pixel electrode 13 is not patterned into a shape having a slit or a comb shape, It may be a flat plate electrode formed in the pixel region. As a material of the pixel electrode 13 and the common electrode 23, a transparent metal oxide film such as indium tin oxide (ITO: Indium 用い Tin Oxide) is preferably used.

The array substrate 10 includes an alignment film 12, and the color filter substrate 20 also includes an alignment film 22. The

alignment films

12 and 22 are vertical alignment films, and can preliminarily align (initially tilt) liquid crystal molecules in the vertical direction. The alignment film material for forming the

alignment films

12 and 22 is not particularly limited. For example, a material obtained by dissolving a polymer material in a solvent is used. Examples of the polymer material include polyimide, polyamide, polyvinyl, polysiloxane, and the like. The polymer material preferably contains a photoreactive functional group. Examples of the photoreactive functional group include a chalcone group, a coumarin group, a cinnamate group, an azobenzene group, and a tolan group.

Examples of a method for forming the

alignment films

12 and 22 include a rubbing method in which grooves are formed by a roller or the like after applying an alignment film material to form an alignment film. Moreover, after apply | coating the alignment film material containing a photoreactive functional group, the formation method of irradiating light and forming a photo-alignment film is mentioned. The type of light irradiated at this time is not particularly limited as long as the photoreactive functional group can be reacted to develop the alignment function. For example, polarized ultraviolet rays are suitable.

As shown in FIG. 1, the bifunctional monomer 5 is present in the liquid crystal layer 30 before the bifunctional monomer polymerization step. In addition, a light shielding mask 25 is provided on the outer side of the transparent substrate 21 (opposite the liquid crystal side), and shields about half of one pixel region. In the bifunctional monomer polymerization step, non-polarized ultraviolet rays are irradiated from the normal direction of the transparent substrate 21. At this time, a voltage may be applied to the liquid crystal layer 30 via the pixel electrode 13 and the common electrode 23, but it is preferable that no voltage is applied from the viewpoint of reducing manufacturing costs. By irradiation with non-polarized ultraviolet rays, the bifunctional monomer 5 starts to be polymerized, and as shown in FIG. 2, a PSA layer 26 is formed on the

alignment films

12 and 22 in a region not shielded from light. As a result, the light shielding mask 25 shields the light, the PSA layer 26 is not formed, the region where the

alignment films

12 and 22 and the liquid crystal layer 30 are in contact (the first alignment region 40), and the PSA layer 26 are formed. A region where the liquid crystal layer 30 is in contact with the liquid crystal layer 30 (second alignment region 41) is formed. Since the PSA layer 26 changes the alignment regulating force of the

alignment films

12 and 22, the first alignment region 40 and the second alignment region 41 have different alignment regulating forces. The voltages will be different from each other. In the liquid crystal display device shown in FIGS. 1 and 2, no voltage is applied, and the liquid crystal molecules are aligned substantially vertically.

The threshold voltage in the first alignment region is preferably larger than the threshold voltage in the second alignment region. As described above, since the threshold voltage increases as the pretilt angle increases, the pretilt angle of the liquid crystal molecules in the first alignment region is larger than the pretilt angle of the liquid crystal molecules in the second alignment region. It is preferable to do. Further, by making the anchoring strength of the first alignment region stronger than the anchoring strength of the second alignment region, the threshold voltage in the first alignment region is made larger than the threshold voltage in the second alignment region. can do. A preferable range of the threshold voltage in the first alignment region is 2.0V to 2.5V. A preferable range of the threshold voltage in the second alignment region is 0.5V to 2.0V.

The light shielding mask 25 may be formed in close contact with the transparent substrate 21 or may be formed apart from the transparent substrate 21. The light shielding mask 25 is not particularly limited as long as it shields light. For example, the light shielding mask 25 may be formed of a metal such as Cr or Al, or may be formed of a resin.

Further, the first alignment region and the second alignment region will be described in detail with reference to FIG.

As shown in FIG. 3, the light shielding mask 25 is formed so as to cover approximately half of one pixel region. At this time, if the direction in which the liquid crystal molecules are aligned is divided into two in the longitudinal direction of the pixels in one pixel region before the second alignment region is formed, the second alignment region is formed. Thus, the alignment direction of the liquid crystal molecules is divided into four within one pixel. Furthermore, the shape of the light shielding mask 25 is not limited to the example of FIG. 3, and may be, for example, a shape that bisects the longitudinal direction of one pixel region, or is arranged in a checkered pattern in one pixel region. Such a shape may be used.

Hereinafter, based on the liquid crystal display device according to the first embodiment, a test example in which a liquid crystal cell having only the second alignment region is manufactured and the pretilt angle is measured will be described.

The liquid crystal cell was shaken, the retardation was measured by the Senarmont method, and the pretilt angle was calculated by fitting using the crystal rotation method. As the measuring device, OMS-AF2 manufactured by Chuo Seiki Co., Ltd. was used. A He—Ne laser irradiation device was used as a light source, and linearly polarized He—Ne laser light (wavelength 632.8 nm, output 2 mW) was irradiated. The spot diameter was 1 mm and the temperature was 25 ° C.

Test example 1
An electrode was formed on the entire principal surface on one side of a pair of glass substrates, and an alignment film material containing polyimide having a cinnamate group that is a photoreactive functional group and an imidization ratio of 50% was applied by spin coating.

After application, temporary drying was performed at 90 ° C. for 1 minute, followed by baking at 200 ° C. for 60 minutes.

Next, the surface of each glass substrate was irradiated with polarized ultraviolet rays as an alignment treatment to form a vertical alignment film. The pretilt angle of the vertical alignment film was 88.1 ° to 88.5 °.

Next, after a seal is applied to one glass substrate and beads are dispersed on the other glass substrate, the two glass substrates are bonded together, and the bonded glass substrates are subjected to a pressure of 0.5 kgf / cm ² . While being pressurized, the seal was cured by heating at 200 ° C. for 60 minutes in a nitrogen purged furnace.

A liquid crystal exhibiting negative dielectric anisotropy was injected into the cell produced by the above method. In the liquid crystal, 2,2 ″ -dimethacryloxydinaphthyl ether, which is a bifunctional monomer, was added so as to be 0.3 wt% of the entire liquid crystal composition.

Next, non-polarized UV (0.33 mW / cm ² ) was irradiated for 4 hours from the normal direction of the main surface of the glass substrate to polymerize the bifunctional monomer.

Test example 2
A liquid crystal cell was prepared in the same manner as in Test Example 1, except that 2,2 ″ -dimethacryloxydinaphthyl ether, which is a bifunctional monomer, was added to the liquid crystal so as to be 0.6 wt% of the total liquid crystal composition. Was made.

Test example 3
Instead of adding 2,2 ″ -dimethacryloxydinaphthyl ether to the liquid crystal so as to be 0.3 wt% of the entire liquid crystal composition, 4,4′-dimethacryloxybiphenyl was added to the liquid crystal composition. A liquid crystal cell was produced in the same manner as in Test Example 1 except that it was added so as to be 0.3 wt% of the whole.

Comparative Example 1
A liquid crystal cell was produced in the same manner as in Test Example 1 except that the bifunctional monomer was not added to the liquid crystal and that the non-polarized UV was not irradiated.

Table 1 shows monomer conditions and non-polarized ultraviolet irradiation conditions in the liquid crystal display devices according to Test Examples 1 to 3 and Comparative Example 1.

FIG. 4 is a diagram showing measurement results of pretilt angles in Test Examples 1 to 3 and Comparative Example 1. As shown in FIG. 4, in Comparative Example 1 in which no bifunctional monomer was added, the pretilt angle was 88.3 °. On the other hand, in Test Example 1 in which 0.3 wt% of 2,2 ″ -dimethacryloxydinaphthyl ether which is a bifunctional monomer was added, the pretilt angle was 86.5 °. In Test Example 2 in which 0.6 wt% of 2,2 ″ -dimethacryloxydinaphthyl ether was added, the pretilt angle was 82.6 °.

From the above, the PSA layer formed by polymerizing 2,2 ″ -dimethacryloxydinaphthyl ether can have a smaller pretilt angle than the alignment film. It has been found that the pretilt angle can be further reduced by increasing the concentration of oxydinaphthyl ether. That is, it was found that by adjusting the concentration of 2,2 ″ -dimethacryloxydinaphthyl ether, the pretilt angle in the second alignment region can be controlled and the threshold voltage in the second alignment region can be adjusted. Accordingly, white spots can be suitably suppressed and contrast can be improved even if the voltage applied to all pixels is constant without changing the voltage applied to each pixel as in MPD. As a result, the cost can be reduced and the aperture ratio can be increased.
On the other hand, in Test Example 3 using only 4,4′-dimethacryloxybiphenyl, the pretilt angle was 88.3 °, and there was no difference from Comparative Example 1 as long as about 0.3 wt% was added. It was.

Embodiment 2
In Embodiment 2, two types of bifunctional monomers are used to form a PSA film. Examples of the photopolymerizable monomer used to form the PSA film in Embodiment 2 include those represented by the following chemical formula (5) in addition to those represented by the above chemical formulas (1) to (4). .

Hereinafter, the liquid crystal display device according to the second embodiment will be described in detail. Descriptions common to the first embodiment are omitted here. FIG. 5 is a schematic cross-sectional view of the liquid crystal display device according to the second embodiment before the polymerization step, and FIG. 6 is a schematic cross-sectional view of the liquid crystal display device according to the second embodiment after the polymerization step. As shown in FIG. 5 and FIG. 6, the liquid crystal display device of Embodiment 2 is the same as the bifunctional monomer 5 except that the bifunctional monomer 6 is added to form the PSA layer 27 in addition to the bifunctional monomer 5. This is the same as the liquid crystal display device according to the first embodiment.

Hereinafter, based on the liquid crystal display device according to the second embodiment, a test example in which a liquid crystal cell having only the second alignment region was produced and the pretilt angle was measured will be described.

Test example 4
In addition to adding 2,2 ″ -dimethacryloxydinaphthyl ether to the liquid crystal so as to be 0.6 wt% of the total liquid crystal composition, 4,4′-dimethacryloxybiphenyl was added to the liquid crystal composition. The same liquid crystal cell as in Test Example 2 was produced, except that it was added so as to be 0.1 wt% of the whole.

Test Example 5
In addition to adding 2,2 ″ -dimethacryloxydinaphthyl ether to the liquid crystal so as to be 0.6 wt% of the total liquid crystal composition, 4,4′-dimethacryloxybiphenyl was added to the liquid crystal composition. The same liquid crystal cell as in Test Example 2 was produced except that it was added so as to be 0.3 wt% of the whole. 4,4′-Dimethacryloxybiphenyl was manufactured by Merck & Co., Inc.

Table 2 shows the monomer conditions and the non-polarized ultraviolet irradiation conditions in the liquid crystal display devices according to Test Examples 2, 4 and 5. The measurement results of the pretilt angle in Test Examples 2, 4, and 5 are shown in FIG.

As shown in FIG. 7, in Test Example 2 in which only 0.6 wt% of 2,2 ″ -dimethacryloxydinaphthyl ether was added, the pretilt angle was 82.6 °. On the other hand, in Test Example 4 in which 0.6 wt% of 2,2 ″ -dimethacryloxydinaphthyl ether and 0.1 wt% of 4,4′-dimethacryloxybiphenyl were added, the pretilt angle was 84.8 °. It became. Further, in Test Example 5 in which 0.6 wt% of 2,2 ″ -dimethacryloxydinaphthyl ether and 0.3 wt% of 4,4′-dimethacryloxybiphenyl were added, the pretilt angle was 88.0 °. It became.

According to Test Examples 1 and 2, the higher the concentration of 2,2 ″ -dimethacryloxydinaphthyl ether, the smaller the pretilt angle. On the other hand, according to Test Examples 4 and 5, when 4,4′-dimethacryloxybiphenyl is added in addition to 2,2 ″ -dimethacryloxydinaphthyl ether, the pretilt angle becomes large and approaches 90 °. It was. It was found that the pretilt angle can be brought close to 90 ° by increasing the concentration of 4,4′-dimethacryloxybiphenyl. That is, by adjusting the concentrations of 2,2 ″ -dimethacryloxydinaphthyl ether and 4,4′-dimethacryloxybiphenyl, respectively, the pretilt angle in the second alignment region is controlled with high accuracy, It has been found that the threshold voltage of the second alignment region can be adjusted precisely. As a result, white spots can be suitably suppressed and contrast can be improved even if the voltage applied to all the pixels is constant without changing the voltage applied to each pixel as in MPD. As a result, the cost can be reduced and the aperture ratio can be increased.

In addition, when only 2,2 ″ -dimethacryloxydinaphthyl ether is added, the pretilt angle decreases according to the dose of unpolarized ultraviolet light. In addition, it was found that when 4,4′-dimethacryloxybiphenyl was added, the pretilt angle did not become 84 ° or less. By utilizing this, the pretilt angle can be suitably controlled.

Various modifications may be made to the above-described embodiments without departing from the technical idea of the present invention. The modification of

Embodiment

1 and 2 is shown below. The liquid crystal display device according to the first and second embodiments may be any of a transmission type, a reflection type, and a reflection / transmission type. If it is a transmission type or a reflection / transmission type, the liquid crystal display device of Embodiment 1 further includes a backlight. The backlight is disposed on the back side of the liquid crystal cell, and is disposed such that light is transmitted through the array substrate 10, the liquid crystal layer 30, and the color filter substrate 20 in this order. In the case of a reflection type or a reflection / transmission type, the array substrate 10 includes a reflection plate for reflecting external light. Further, at least in a region where reflected light is used as a display, the polarizing plate of the color filter substrate 20 needs to be a circularly polarizing plate.

The liquid crystal display device according to the first and second embodiments may be in the form of a color filter on array (Color Filter On Array) including color filters on the array substrate 10. In addition, the liquid crystal display device according to the first and second embodiments may be a monochrome display. In that case, the color filter does not need to be arranged.

This application claims priority based on the Paris Convention or the laws and regulations in the country to which the transition is based on Japanese Patent Application No. 2010-253211 filed on November 11, 2010. The contents of these applications are hereby incorporated by reference in their entirety.

4, 104: Liquid crystal molecules 5, 6: Bifunctional monomer 10, 110: Array substrate 11, 21:

Transparent substrate

12, 22, 112, 122: Alignment film 13: Pixel electrode 23: Common electrode 20, 120: Color filter substrate 25, 125: light shielding mask 26, 27: PSA layer 30, 130: liquid crystal layer 40: first alignment region 41: second alignment region 42: source wiring 43: auxiliary capacitance (CS) wiring 44: TFT
45: Gate wiring 105: Monomer 113, 123: Electrode 115: Protrusion 126: First polymer 127: Second polymer

Claims

A liquid crystal display device comprising a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates,
The liquid crystal layer has negative dielectric anisotropy;
At least one of the pair of substrates is a part of a main surface of the alignment film on the liquid crystal layer side by polymerization of an electrode, an alignment film that vertically aligns adjacent liquid crystal molecules, and at least one bifunctional monomer. And a polymer layer for controlling the alignment of adjacent liquid crystal molecules,
A plurality of pixels provided with a first alignment region in contact with the alignment film and liquid crystal molecules, and a second alignment region in contact with the polymer layer and liquid crystal molecules;
The liquid crystal display device, wherein the first alignment region and the second alignment region have different threshold voltages.
2. The liquid crystal display device according to claim 1, wherein a pretilt angle of the liquid crystal molecules in the first alignment region and a pretilt angle of the liquid crystal molecules in the second alignment region are different from each other.
3. The liquid crystal display device according to claim 2, wherein the pretilt angle of the liquid crystal molecules in the first alignment region is larger than the pretilt angle of the liquid crystal molecules in the second alignment region.
4. The liquid crystal display device according to claim 1, wherein the alignment film is formed by irradiating polarized ultraviolet light to an alignment film material containing a photoreactive functional group.
5. The liquid crystal display device according to claim 4, wherein the photoreactive functional group is at least one selected from the group consisting of a chalcone group, a coumarin group, a cinnamate group, an azobenzene group, and a tolan group.
The area of the second alignment region is larger than 30% and smaller than 70% as compared with the sum of the area of the first alignment region and the area of the second alignment region. 6. A liquid crystal display device according to any one of 1 to 5.
The liquid crystal display device according to any one of claims 1 to 6, wherein the bifunctional monomer is represented by the following chemical structural formula.
P1-A1- (Z1-A2) n-P2
(In the formula, P1 and P2 each independently represent an acrylate group, a methacrylate group, a vinyl group, a vinyloxy group, or an epoxy group. A1 and A2 each independently represent a 1,4-phenylene group, naphthalene- 2,6-diyl group, anthracene-2,6-diyl group or phenanthrene-2,7-diyl group, wherein the hydrogen atom contained in the ring structure is halogen, methyl group, ethyl group or propyl group Z1 may be COO, OCO, O, CO, NHCO, CONH, or S, or A1 and A2 or A2 and A2 may be directly bonded to each other. (N is 0, 1, or 2)
The liquid crystal display device according to any one of claims 1 to 7, wherein the bifunctional monomer has a dinaphthyl ether skeleton.
The liquid crystal display device according to claim 8, wherein the bifunctional monomer is dimethacryloxydinaphthyl ether.
A method of manufacturing a liquid crystal display device comprising a pair of substrates and a liquid crystal layer having negative dielectric anisotropy sandwiched between the pair of substrates,
The manufacturing method includes a step of forming an electrode on at least one of the pair of substrates, a step of forming an alignment film that vertically controls liquid crystal molecules adjacent thereto, and a main surface on the liquid crystal side of the alignment film. Forming a polymer layer that controls the alignment of liquid crystal molecules adjacent to a part of
The step of forming the polymer layer was added to the liquid crystal layer by irradiating light in a state where a part of at least one of the pair of substrates was shielded by the light shielding member and the remaining part was not shielded. A step of polymerizing a bifunctional monomer to form a first alignment region in contact with the alignment film and liquid crystal molecules, and a second alignment region in contact with the polymer layer and liquid crystal molecules in the pixel;
A method for manufacturing a liquid crystal display device, wherein the first alignment region and the second alignment region have different threshold voltages.
In the step of polymerizing the bifunctional monomer, the alignment film controls the pretilt angle of liquid crystal molecules, the light shielding member shields a part of the pixel, and the light irradiation is performed without applying a voltage to the liquid crystal layer. Performing the step of photopolymerizing the bifunctional monomer to form the polymer layer,
The method of manufacturing a liquid crystal display device according to claim 10, wherein a pretilt angle of the liquid crystal molecules in the first alignment region is larger than a pretilt angle of the liquid crystal molecules in the second alignment region. .
12. The method of manufacturing a liquid crystal display device according to claim 10, wherein the area not shielded by the light shielding member is larger than 30% and smaller than 70% as compared with all the areas where the liquid crystal is orientation controlled.