WO2012141173A1 - Scattering-type liquid crystal display device and method for manufacturing same - Google Patents

Abstract

This scattering-type liquid crystal display device (100A) has a first substrate (2) and a second substrate (3) disposed facing each other, a liquid crystal layer (1) disposed between the first substrate (2) and second substrate (3) and capable of switching states between a transmitting state for transmitting light and a scattering state for scattering light, and optical alignment films (12, 13) formed on one or both of the first substrate (2) and second substrate (3).

Description

Scattering type liquid crystal display device and manufacturing method thereof

The present invention relates to a scattering type liquid crystal display device and a manufacturing method thereof.

Liquid crystal display devices are widely used as liquid crystal televisions, monitors, mobile phones and the like as flat panel displays having features such as thinness and light weight. However, the most widely used liquid crystal display device at present is a system using two or one polarizing plate, and there is a problem that the light use efficiency is low.

So far, as a display method that does not use a polarizing plate, a guest-host method or a polymer dispersed liquid crystal (PDLC) method has been proposed (for example, Patent Document 1).

The liquid crystal layer (PDLC layer) of the PDLC type scattering liquid crystal display device has a plurality of liquid crystal regions dispersed in a polymer. Each liquid crystal region is formed in a space (hereinafter referred to as “small room”) defined by a wall made of a polymer. In such a PDLC layer, when no voltage is applied (when no voltage is applied), a difference in refractive index occurs between the liquid crystal in the liquid crystal region (nematic liquid crystal material) and the polymer, and light is scattered at these interfaces. Thus, a white display can be obtained. When a voltage is applied to the PDLC layer (when a voltage is applied), the alignment of the liquid crystal changes and the refractive indexes of the liquid crystal and the polymer become substantially equal, so that light passes through the PDLC layer without being scattered.

JP-A-5-053096

In the method of manufacturing a PDLC liquid crystal display device disclosed in Patent Document 1, a wall that defines a small chamber is obtained by irradiating a polymerizable monomer mixed with a nematic liquid crystal material with ultraviolet rays to polymerize the polymerizable monomer. Is formed. According to this method, since the nematic liquid crystal material is also irradiated with ultraviolet rays, the nematic liquid crystal material is decomposed to generate impurity ions. Impurity ions in the liquid crystal layer cause a reduction in voltage holding ratio and burn-in due to residual DC (Direct Current), which degrades display quality.

The present invention has been made in view of the above problems, and an object thereof is to provide a scattering type liquid crystal display device having high display quality.

A scattering-type liquid crystal display device according to an embodiment of the present invention includes a first substrate and a second substrate that are disposed to face each other, and a transmission state that is disposed between the first substrate and the second substrate and transmits light. A liquid crystal layer whose state can be switched between a light scattering state and a light scattering state, and a photo-alignment film formed on at least one of the first substrate and the second substrate.

In one embodiment, the liquid crystal layer has a plurality of liquid crystal domains, and director directions of the plurality of liquid crystal domains are randomly oriented.

In one embodiment, the photo-alignment film has an alignment treatment region subjected to alignment treatment and a non-alignment treatment region not subjected to alignment treatment, the width of the alignment treatment region is S, and the non-alignment treatment region When the width is L, the width S and the width L satisfy L + S ≦ 30 μm.

In one embodiment, the alignment treatment region and the non-alignment treatment region are rectangular regions, and the alignment treatment region and the non-orientation treatment region are formed in parallel and alternately.

In one embodiment, the photo-alignment film includes a first photo-alignment film formed on the first substrate and a second photo-alignment film formed on the second substrate, and the first photo-alignment film The alignment regulation direction of the alignment treatment region and the alignment regulation direction of the alignment treatment region of the second alignment film are orthogonal to each other.

In one embodiment, the liquid crystal layer has a nematic liquid crystal material having a positive dielectric anisotropy, the thickness of the liquid crystal layer is d, and the birefringence of the nematic liquid crystal material is Δn. Δn × d of the liquid crystal layer is 400 nm or more.

In one embodiment, the photo-alignment film is a horizontal alignment film.

In one embodiment, the photo-alignment film is formed from a cinnamic acid derivative.

The manufacturing method of the scattering type liquid crystal display device according to the embodiment of the present invention includes a step A for forming a photo-alignment film on a substrate, a step B for performing an alignment treatment on the photo-alignment film, and a step C for forming a liquid crystal layer. Is included.

In one embodiment, the above-described method for manufacturing a scattering type liquid crystal display device includes a rectangular opening region and a rectangular light shielding region in Step B, and the width of the rectangular opening region is S1, When the rectangular light shielding region is L1, a mask satisfying S1 + L1 ≦ 30 μm is used as the width S1 and the width L1.

In one embodiment, the rectangular opening regions and the rectangular light shielding regions are formed in parallel and alternately.

In one embodiment, the step B includes a step B1 of irradiating the photo-alignment film with light, and the number of times of the light irradiation is one.

In one embodiment, the step C does not include a monomer polymerization step that imparts scattering ability.

According to the present invention, a scattering type liquid crystal display device with high display quality is provided.

(A) is typical sectional drawing of the scattering type liquid crystal display device 100A in embodiment by this invention, (b) is a figure explaining the photo-alignment films 12 and 13. FIG. It is a figure explaining the orientation of the liquid crystal molecule. It is a figure which shows the polarizing microscope image of the liquid crystal layer 1 of 100 A of scattering type liquid crystal display devices. It is a graph which shows an applied voltage-scattering intensity curve. (A)-(c) is a figure explaining the measuring method of scattering intensity. It is a figure which shows the polarization microscope image of the liquid crystal layer 1 of the scattering type liquid crystal display device 100A at the time of no voltage application. It is a figure explaining orientation processing field O1 and non-alignment processing field D1. It is an enlarged view of the area | region A of FIG. (A) is a figure which shows the polarization microscope image of the liquid crystal layer 1 of the liquid crystal display device 200 at the time of no voltage application, (b) is a figure explaining the orientation state of a liquid crystal molecule. It is a figure explaining the mask 110. FIG.

Hereinafter, a scattering type liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the illustrated embodiment.

A scattering type liquid crystal display device 100A according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a schematic cross-sectional view of the scattering type liquid crystal display device 100A. FIG. 1B is a diagram illustrating the photo-alignment films 12 and 13.

The scattering-type liquid crystal display device 100A is disposed between the first substrate 2 and the second substrate 3, which are disposed to face each other, and between the first substrate 2 and the second substrate 3, and transmits a light transmitting state and light. A liquid crystal layer 1 that can be switched between a scattering state and a scattering state. The thickness (d) of the liquid crystal layer 1 is, for example, 3.5 μm (d = 3.5 μm).

Further, the scattering-type liquid crystal display device 100A includes a photo-alignment film (in this embodiment, the first photo-alignment film 12 and the second photo-alignment film 13) formed on at least one of the first substrate 2 and the second substrate 3. ). As shown in FIG. 1B, the first photo-alignment film 12 and the second photo-alignment film 13 are each provided with alignment treatment regions O1 and O2 that have been subjected to alignment treatment (in this embodiment, photo-alignment treatment), Non-orientation-treated regions D1 and D2 that are not subjected to the orientation treatment. The alignment treatment regions O1 and O2 and the non-alignment treatment regions D1 and D2 are, for example, rectangular regions. For example, the alignment processing region O1 and the non-alignment processing region D1 are arranged in parallel and alternately in a stripe shape. Similarly, the alignment treatment region O2 and the non-alignment treatment region D2 are, for example, arranged in parallel and alternately in a stripe shape. Instead of forming the alignment treatment region and the non-orientation treatment region in the photo-alignment film, for example, the photo-alignment film is subjected to alignment treatments having different orientation treatment directions at a predetermined pitch (for example, a pitch of 30 μm or less). A predetermined alignment treatment region may be formed in the photo-alignment film.

In the present embodiment, the first photo-alignment film is such that the alignment regulating direction L1 of the alignment treatment region O1 of the first photo-alignment film 12 and the alignment regulation direction L2 of the alignment treatment region O2 of the second photo-alignment film 13 are orthogonal to each other. 12 and the second photo-alignment film 13 are formed. Further, when the widths of the alignment treatment regions O1 and O2 are S and the widths of the non-alignment treatment regions D1 and D2 are L, the width S and the width L satisfy L + S ≦ 30 μm. In the scattering type liquid crystal display device 100A, L = 5 μm and S = 25 μm. In addition, the thickness of the 1st photo-alignment film 12 and the 2nd photo-alignment film 13 is 100 nm, respectively, for example. The liquid crystal layer 1 includes, for example, a nematic liquid crystal material (not shown) having positive dielectric anisotropy. The nematic liquid crystal material has, for example, properties of a birefringence index (Δn) of 0.08 (Δn = 0.08) and a dielectric anisotropy (Δε) of 5 (Δε = 5). The liquid crystal layer 1 is hermetically held by a sealant (for example, an ultraviolet curable resin (trade name: TB3026E (manufactured by Three Bond)) formed on the periphery of the scattering type liquid crystal display device 100A. The display device 100A includes a thin film transistor 5 and a pixel electrode 4 formed for each pixel, and the scattering type liquid crystal display device 100A includes a common electrode 8 formed on the liquid crystal layer 1 side of the second substrate 3.

The first photo-alignment film 12 and the second photo-alignment film 13 are, for example, horizontal alignment films. The first photo-alignment film 12 and the second photo-alignment film 13 are made of, for example, a cinnamic acid derivative (for example, polyvinyl cinnamate). The photo-alignment treatment is performed by irradiating the photo-alignment film with linearly polarized ultraviolet rays (sometimes referred to as linearly polarized ultraviolet rays). As shown in FIG. 1B, an alignment regulating force (see the alignment regulating direction L1) for aligning liquid crystal molecules is generated in a direction orthogonal to the polarization direction P1 of the irradiated ultraviolet rays. Therefore, as shown in FIG. 2, in the alignment treatment regions O1 and O2, the liquid crystal molecules 71 in the respective regions are aligned so that the major axis direction of the liquid crystal molecules 71 is parallel to the alignment regulating direction L1 or L2. The liquid crystal molecules 71 in the non-alignment processing regions D1 and D2 are aligned almost randomly in various directions. That is, the director directions of the plurality of liquid crystal domains included in the liquid crystal layer 1 are randomly oriented (sometimes referred to as random orientation).

FIG. 3 is a diagram showing a polarization microscope image of the liquid crystal layer 1 of the scattering type liquid crystal display device 100A when no voltage is applied.

As shown in FIG. 3, the nematic liquid crystal material in the liquid crystal layer 1 is roughly randomly aligned by the alignment treatment applied to the photo-alignment films 12 and 13, and includes many disclination lines (also referred to as domain boundaries). When a liquid crystal cell having such a liquid crystal layer 1 is irradiated with laser light from the normal direction of the liquid crystal cell (direction parallel to the thickness direction of the liquid crystal layer 1), the liquid crystal display device 200 of Comparative Example 1 described later is used. Also confirmed the scattering effect of spreading the laser spot. This scattering effect is attributed to the fact that the liquid crystal molecules have birefringence and the liquid crystal molecules are oriented almost randomly.

In general, when a photo-alignment film that has been subjected to photo-alignment treatment is used, liquid crystal molecules are aligned in the alignment regulating direction defined by the photo-alignment treatment (see FIG. 2). However, in this embodiment, even when a photo-alignment film that has been subjected to photo-alignment treatment is used, random alignment including many domain boundaries was obtained. This is a knowledge obtained as a result of various studies by the present inventors. Thereby, when no voltage is applied, the liquid crystal layer 1 is formed with a spatial modulation structure of the refractive index, and is in a scattering state in which light is scattered. Further, when a voltage is applied to the liquid crystal layer 1, the liquid crystal molecules in the liquid crystal layer 1 are aligned perpendicular to the first substrate 2, and the liquid crystal layer 1 becomes transparent.

Generally, liquid crystal molecules have the property of being aligned in the same direction as adjacent liquid crystal molecules. The distance that one liquid crystal molecule affects the orientation of surrounding liquid crystal molecules is said to be less than 1 μm in the case of nematic liquid crystal molecules. Accordingly, even if alignment patterning is performed on the photo-alignment film with an order of less than 1 μm, the liquid crystal molecules are not aligned according to the alignment pattern. In this embodiment, since the width L and the width S are each 1 μm or more, it seems that in principle the liquid crystal molecules may be aligned according to the alignment pattern (see FIG. 2). However, when L + S = 30 μm, the liquid crystal molecules were not aligned according to the alignment pattern. This is because the alignment deformation of the liquid crystal material is accompanied by a change in elastic energy, and the rapid alignment deformation at a narrow pitch causes a significant increase in elastic energy, so the liquid crystal material does not completely follow the alignment pattern imparted to the alignment film. Furthermore, since the alignment regulating direction L1 of the first photo-alignment film 12 and the alignment regulating direction L2 of the second photo-alignment film 13 intersect (for example, orthogonal), splay alignment, bend alignment, left twist and right twist This is probably because many alignment patterns such as the twist alignment of the liquid crystal molecules can exist with equal probability, and the alignment of the liquid crystal molecules can be complicated.

Next, the electro-optical characteristics of the scattering type liquid crystal display device 100A will be described.

FIG. 4 is a graph showing the scattered light intensity with respect to the applied voltage (V) in the scattering-type liquid crystal display device 100A. In addition, the measurement of the scattering intensity in a graph was performed with the following method.

FIG. 5 is a diagram for explaining the scattering intensity.

As shown in FIG. 5A and FIG. 5B, the liquid crystal cells 51a and 51b having the liquid crystal layer 1 are irradiated with the laser beam oscillated from the laser oscillator 90, respectively. A direct beam (0th-order diffracted light) that has passed through is projected onto the screen 81. The screen 81 was photographed with a digital camera (EOS KISS DISITAL N (manufactured by CANON)), and the light intensity was measured. A voltage is applied to the liquid crystal cell 51a shown in FIG. 5A, and the liquid crystal layer 1 of the liquid crystal cell 51a is in a transmissive state. No voltage is applied to the liquid crystal cell 51b shown in FIG. 5B, and the liquid crystal layer 1 of the liquid crystal cell 51b is in a scattering state. Curves 52a and 52b shown in FIGS. 5A and 5B represent light intensity distribution curves projected on the screen 81, respectively.

In the light intensity distribution curve 52b shown in FIG. 5B, the light intensity of the 0th-order diffracted light is reduced due to diffraction, and the region where the laser is projected onto the screen is widened due to scattering.

The obtained light intensity distribution curves 52a and 52b are normalized by the maximum intensity of the respective 0th-order diffracted light, and the difference between the normalized light intensity distribution curve 52a ′ and the light intensity distribution curve 52b ′ is taken as the scattering intensity. (See the hatching area h1 shown in FIG. 5C).

As can be seen from FIG. 4, when no voltage is applied, the scattering intensity of the scattering-type liquid crystal display device 100A is strong, and when a voltage is applied, the scattering intensity decreases.

When no voltage was applied, it was found that the scattering type liquid crystal display device 100A has a diffraction effect and a scattering effect, and thus has a high scattering intensity. Further, it was found that when the voltage is applied, the scattering type liquid crystal display device 100A is in a favorable transparent state when the liquid crystal molecules of the liquid crystal layer 1 are aligned perpendicular to the first substrate 2.

Next, the width S of the alignment treatment regions O1 and O2 and the width L of the non-alignment treatment regions D1 and D2 will be described with reference to FIGS. FIG. 6 is a diagram showing a polarization microscope image of the liquid crystal layer 1 of the scattering type liquid crystal display device 100A when no voltage is applied. FIG. 7 is a diagram illustrating a result of performing fast Fourier transform (FFT Fourier Transform: FFT) on the polarization microscope image of the liquid crystal layer 1 of the scattering type liquid crystal display device 100A when no voltage is applied. FIG. 8 is an enlarged view of region A in FIG. In addition, the polarizing plate of the polarizing microscope used for obtaining FIG. 6 is arranged in crossed Nicols, and image analysis software manufactured by Media Cybernetics, Inc. was used for FFT. Specifically, a digital photograph (JPEG format) of the liquid crystal layer 1 of the scattering-type liquid crystal display device 100A when no voltage is applied is taken using a polarizing microscope in which polarizing plates are arranged in crossed Nicols. The image is converted to 8-bit gray scale. Perform FFT on the image converted to 8-bit grayscale. As a result, spots (arrows in FIG. 8) corresponding to a period of 30 μm appeared in the horizontal and vertical directions. This corresponds to the sum of the width S of the alignment treatment region O1 and the width L of the non-alignment treatment region D1 (S + L, in this embodiment, S + L = 30 μm) (hereinafter also referred to as an exposure cycle). I found out. In addition to this method, for example, the period of the alignment treatment pattern can be calculated from the diffraction angle of the diffracted light obtained by irradiating the liquid crystal layer 1 of the scattering type liquid crystal display device 100A with laser when no voltage is applied.

Unlike the PDLC type liquid crystal display device disclosed in Patent Document 1, the scattering type liquid crystal display device 100A is manufactured without going through a process of forming a polymer wall that defines a liquid crystal region. For this reason, the nematic liquid crystal material is not irradiated with ultraviolet rays, and impurity ions are not easily generated. Therefore, a decrease in voltage holding ratio and a seizure due to residual DC hardly occur, and a liquid crystal display device with high display quality can be obtained. Although details will be described later, in a liquid crystal display device having a structure like the scattering type liquid crystal display device 100A, the first substrate 2 and the second substrate 3 do not need to be aligned with high accuracy, and thus manufacturing is easy. become.

Further, the inventor sets the width S of the alignment treatment regions O1 and O2 and the width L of the non-alignment treatment regions D1 and D2 of the scattering type liquid crystal display device 100A to 10 μm (S = 10 μm, L = 10 μm, S + L = 20 μm), respectively. The scattering type liquid crystal display device (referred to as the scattering type liquid crystal display device of Modification 1) was also studied. As a result, it was found that the scattering-type liquid crystal display device of Modification Example 1 has a scattering effect similar to that of the scattering-type liquid crystal display device 100A. Furthermore, it was found that the scattering type liquid crystal display device of Modification Example 1 has a larger diffraction angle than the scattering type liquid crystal display device 100A.

Further, the inventor sets the birefringence (Δn) of the nematic liquid crystal material included in the liquid crystal layer 1 of the scattering type liquid crystal display device 100A to 0.22 (Δn = 0.22), and sets the dielectric anisotropy (Δε). A scattering-type liquid crystal display device with 5 (Δε = 5) (referred to as a scattering-type liquid crystal display device of Modification 2) was also examined. As a result, it was found that the scattering type liquid crystal display device of Modification Example 2 has a higher scattering ability than the scattering type liquid crystal display device 100A. This is considered to be because Δn increases and the amplitude of spatial modulation of the refractive index increases. The scattering intensity is considered to be substantially proportional to the product (Δn × d) of the thickness (d) of the liquid crystal layer 1 and the birefringence index (Δn).

Further, the inventor is a scattering type liquid crystal display device (referred to as a scattering type liquid crystal display device of Modification 3) in which the thickness (d) of the liquid crystal layer 1 of the scattering type liquid crystal display device 100A is 5 μm (d = 5 μm). Also examined. As a result, it was found that the scattering type liquid crystal display device of Modification Example 3 has a higher scattering ability than the scattering type liquid crystal display device 100A. This is considered to be because Δn × d increases and the amplitude of spatial modulation of Δn × d increases. As a result of investigating the scattering power of the scattering type liquid crystal display devices of the modification example 2 and the modification example 3, it was found that the larger the Δn × d of the liquid crystal layer 1, the greater the scattering ability. Furthermore, it has been found by the inventors that a scattering type liquid crystal display device having good scattering characteristics can be obtained when Δn × d of the liquid crystal layer 1 is 400 nm or more.

Next, a liquid crystal display device 200 according to a comparative example will be described with reference to the drawings. Constituent elements common to the scattering type liquid crystal display device 100A are denoted by the same reference numerals.

In the liquid crystal display device 200, the width S of the alignment treatment regions O1 and O2 and the width L of the non-alignment treatment regions D1 and D2 of the scattering type liquid crystal display device 100A are 25 μm (S = 25 μm, L = 25 μm, S + L = 50 μm). This is a liquid crystal display device.

FIG. 9A is a diagram showing a polarization microscope image of the liquid crystal layer 1 of the liquid crystal display device 200. The polarizing plate of the polarizing microscope used for photography is arranged in crossed Nicols. In the liquid crystal display device 200, unlike the scattering type liquid crystal display device 100A, it was found that liquid crystal molecules are periodically arranged and there are few disclination lines.

FIG. 9B is a diagram for explaining the alignment state of the liquid crystal molecules 71 of the liquid crystal layer 1 of the liquid crystal display device 200. The first photo-alignment film 12 and the second photo-alignment so that the alignment regulating directions in the alignment treatment regions O1 and O2 of the first photo-alignment film 12 and the second photo-alignment film 13 of the liquid crystal display device 200 are orthogonal to each other. The film 13 is formed. In the liquid crystal layer 1 of the liquid crystal display device 200, the random alignment region 72 in which the liquid crystal molecules 71 are approximately randomly aligned and the liquid crystal molecules 71 are parallel to the alignment regulating direction of the first photo-alignment film 12 or the second photo-alignment film 13. And a TN (Twisted Nematic) alignment region 74 in which the liquid crystal molecules 71 are twisted and aligned. The random alignment region 72 is a region where the non-alignment processing region D1 of the first photo-alignment film 12 and the non-alignment processing region D2 of the second photo-alignment film 13 overlap.

The uniaxial alignment region 73 is a region where the alignment treatment region O1 of the first photo-alignment film 12 overlaps with the non-alignment treatment region D2 of the second photo-alignment film 13, or the non-alignment treatment region D1 of the first photo-alignment film 12. This is a region where the alignment treatment region O2 of the second photo-alignment film 13 overlaps. The TN alignment region 74 is a region where the alignment treatment region O1 of the first photo-alignment film 12 and the alignment treatment region O2 of the second photo-alignment film 13 overlap. In the twist direction in the plurality of TN alignment regions 74, since the pretilt angle of the liquid crystal molecules is small (pretilt angle less than 1 °), the right and left twists that degenerate are mixed (some are left-twisted and some are right-twisted). ing. The liquid crystal molecules 71 in the uniaxial alignment region 73 are substantially uniaxially aligned due to the correlation length of the liquid crystal molecules 71.

When laser was applied to the liquid crystal layer 1 from the normal direction of the display surface of the liquid crystal display device 200, a clear diffraction effect due to the periodic arrangement of the liquid crystal molecules 71 was obtained, but scattering could not be confirmed. The liquid crystal display device 200 has a scattering ability if the light incident on the liquid crystal layer 1 is non-parallel light. However, in the liquid crystal display device 200, diffraction occurs when the light incident on the liquid crystal layer 1 is parallel light, but the effect of scattering is small.

Therefore, as described above, as a scattering-type liquid crystal display device capable of obtaining a sufficient scattering effect, the width S of the alignment treatment regions O1 and O2 and the width L of the non-alignment treatment regions D1 and D2 satisfy S + L ≦ 30 μm. It is preferable. The lower limit value of S + L is not particularly limited, and is considered to depend on the capability of the manufacturing apparatus (for example, the resolution of the exposure apparatus).

Next, a manufacturing method of the scattering type liquid crystal display device 100A will be described.

The manufacturing method of the scattering-type liquid crystal display device 100A according to the embodiment of the present invention includes a process A for forming the photo-alignment films 12 and 13 on the substrates 2 and 3, and a process B for performing the alignment process on the photo-alignment films 12 and 13; And step C of forming the liquid crystal layer 1. Further, in step B, when the rectangular opening region O3 and the rectangular light shielding region D3 are provided, the width of the rectangular opening region O3 is S1, and the width of the rectangular light shielding region D3 is L1, It is preferable to use a mask (for example, photomask) 110 that satisfies S1 + L1 ≦ 30 μm (see FIG. 10). Furthermore, it is preferable that the rectangular opening regions O3 and the rectangular light shielding regions D3 are formed in parallel and alternately. Furthermore, the process B includes a process B1 in which the photo-alignment film 12 (or 13) is irradiated with light, and the number of times of light irradiation is preferably one. Furthermore, since the liquid crystal layer 1 has a nematic liquid crystal material and does not have a monomer, the process C does not include a monomer polymerization process (for example, a light irradiation process) that imparts scattering ability.

Specifically, a manufacturing method of the scattering type liquid crystal display device 100A will be described.

First, substrates (for example, glass substrates (# 1737 (manufactured by Corning)) 2 and 3 on which a transparent electrode is formed are prepared.The transparent electrode is formed of, for example, ITO (Indium Tin Oxide).

Next, for example, a polyvinyl cinnamate solution is applied on the transparent electrode by a spin coating method. As a solvent for the polyvinyl cinnamate solution, a mixture of N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether in an equivalent amount was used. The above solution was prepared by dissolving 3% by weight of polyvinyl cinnamate in this solvent.

Next, after temporary drying at 90 ° C. for 1 minute, baking is performed at 130 ° C. for 60 minutes while replacing nitrogen (N ₂ ) to form the photo-alignment film 12 (or 13). did. The thickness of the photo-alignment film 12 (or 13) after firing was 100 nm. However, the thickness of the photo-alignment film 12 (or 13) after firing is not limited to this.

Next, as the alignment treatment, for example, linearly polarized ultraviolet rays were irradiated once from the normal direction of the substrate 2 (or 3) so as to be 5 J / cm ² at a wavelength of 313 nm. That is, the number of times that the photo-alignment film 12 is irradiated with the linearly polarized ultraviolet light is one, and the number of times that the photo-alignment film 13 is irradiated with the linearly polarized ultraviolet light is one. At this time, linearly polarized ultraviolet rays were irradiated while using the mask 110 described above. Thereby, the alignment treatment region O1 and the non-alignment treatment region D1 are formed in the photo-alignment films 12 and 13. However, the alignment treatment method and the photo-alignment film are not limited to this. Instead of using the mask 110 in which the rectangular opening region O3 and the rectangular light shielding region D3 are formed in a line shape, for example, a mask in which the opening region O3 and the light shielding region D3 are formed in a mosaic shape may be used. Alternatively, a mask formed so that the opening region O3 and the light shielding region D3 have a hexagonal (hexagonal) periodic structure may be used.

Next, for example, a thermosetting sealant (for example, HC1413EP (manufactured by Mitsui Chemicals)) was printed on one of the substrates 2 and 3 by a screen printing method.

Next, beads having a diameter of 3.5 μm (for example, SP-2035 (manufactured by Sekisui Chemical Co., Ltd.)) were spread on the other substrate by a known method.

Next, the substrate 2 and the substrate 3 were bonded so that the alignment regulation direction L1 of the photo-alignment film 12 and the alignment regulation direction L2 of the photo-alignment film 13 were orthogonal, for example.

Next, while pressing the bonded substrates 2 and 3 at a pressure of 0.5 kgf / cm ² , the sealing agent is cured by heating in a furnace purged with nitrogen at 200 ° C. for 60 minutes, and the liquid crystal cell is Completed.

Next, a nematic liquid crystal material was injected into the liquid crystal cell by a known method. At this time, no monomer is injected into the liquid crystal cell.

Next, the injection port of the liquid crystal cell was closed with, for example, an ultraviolet curable resin (TB3026E (manufactured by ThreeBond)), and the resin was cured by irradiation with ultraviolet rays (wavelength 365 nm). At this time, a region that becomes a display region of the scattering type liquid crystal display device 100A is shielded from light so that ultraviolet rays do not hit this region. Further, the transparent electrodes were short-circuited so that the alignment of the liquid crystal molecules was not disturbed by the external field, and the surfaces of the substrates 2 and 3 were subjected to static elimination treatment.

Next, the liquid crystal cell in which the nematic liquid crystal material is injected is heated at 130 ° C. for 40 minutes to perform a realignment treatment to make the liquid crystal molecules isotropic phase, thereby removing the flow alignment of the liquid crystal molecules, and the scattering type liquid crystal A display device 100A was obtained.

In such a manufacturing method, the nematic liquid crystal material is not exposed to ultraviolet rays, and impurity ions are not easily generated. Therefore, a scattering-type liquid crystal display device having good electrical characteristics is obtained which is less likely to cause a decrease in voltage holding ratio and a residual DC. can get. As a result, a scattering type liquid crystal display device with high display quality can be obtained.

Next, the scattering characteristics of the liquid crystal display device 200 of the comparative example, the scattering type liquid crystal display device 100A, and the scattering type liquid crystal display devices of the modified examples 1 to 3 were evaluated.

The liquid crystal layer 1 of the liquid crystal display device 200 and the scattering type liquid crystal display device in this embodiment is irradiated with a red laser (for example, wavelength 630 nm, luminous intensity 5 mW) from the normal direction of the display surface of each liquid crystal display device. The spot of the next diffracted light was visually observed through an ND (Neutral Density) filter, a filter that made the scattered light invisible was selected, and the scattering intensity was evaluated. The results are shown in Table 1.

In Table 1, the smaller the numerical value of the ND filter, the greater the scattering intensity.

Table 1 shows that the liquid crystal display device 200 cannot obtain scattered light. Furthermore, it was found that the scattered liquid crystal display devices of the modification example 2 and the modification example 3 can obtain stronger scattered light than the scattering type liquid crystal display device 100A and the scattering type liquid crystal display device of the modification example 1. This is because Δn × d of the liquid crystal layer 1 of the scattering type liquid crystal display devices of Modification Example 2 and Modification Example 3 is Δn × d of the liquid crystal layer 1 of the scattering type liquid crystal display device 100A and of the scattering type liquid crystal display device of Modification Example 1. It is thought that it is larger.

The scattering type liquid crystal display device according to the present invention provides a scattering type liquid crystal display device with high display quality.

The present invention can be applied to a liquid crystal display device and various electric devices using the liquid crystal display device. In particular, it is suitably used for large liquid crystal display devices such as digital signage.

1 Liquid crystal layer 2, 3 Substrate 4, 8 Transparent electrode 5 TFT
12, 13 Photo-alignment film 100A Scattering type liquid crystal display device O1, O2 Alignment processing region D1, D2 Non-alignment processing region P1, P2 Polarization direction L1, L2 Alignment regulation direction L, S Width

Claims (13)

A first substrate and a second substrate disposed opposite to each other;
A liquid crystal layer disposed between the first substrate and the second substrate, the state of which can be switched between a transmission state transmitting light and a scattering state scattering light;
A scattering-type liquid crystal display device comprising: a photo-alignment film formed on at least one of the first substrate and the second substrate. The liquid crystal layer has a plurality of liquid crystal domains,
The scattering type liquid crystal display device according to claim 1, wherein director directions of the plurality of liquid crystal domains are randomly oriented. The photo-alignment film has an alignment treatment region that has been subjected to an alignment treatment and a non-alignment treatment region that has not been subjected to an alignment treatment.
3. The scattering-type liquid crystal display device according to claim 1, wherein the width S and the width L satisfy L + S ≦ 30 μm, where S is a width of the alignment treatment region and L is a width of the non-alignment treatment region. The alignment treatment region and the non-orientation treatment region are rectangular regions,
The scattering-type liquid crystal display device according to claim 3, wherein the alignment treatment regions and the non-alignment treatment regions are formed in parallel and alternately. The photo-alignment film includes a first photo-alignment film formed on the first substrate and a second photo-alignment film formed on the second substrate,
5. The scattering type liquid crystal according to claim 3, wherein the alignment regulating direction of the alignment treatment region of the first photo-alignment film is orthogonal to the alignment regulating direction of the alignment treatment region of the second alignment film. Display device. The liquid crystal layer has a nematic liquid crystal material having a positive dielectric anisotropy,
When the thickness of the liquid crystal layer is d and the birefringence of the nematic liquid crystal material is Δn,
The scattering type liquid crystal display device according to claim 1, wherein Δn × d of the liquid crystal layer is 400 nm or more. The scattering liquid crystal display device according to claim 1, wherein the photo-alignment film is a horizontal alignment film. The scattering type liquid crystal display device according to any one of claims 1 to 7, wherein the photo-alignment film is formed of a cinnamic acid derivative. Forming a photo-alignment film on the substrate;
Step B for performing an alignment treatment on the photo-alignment film;
A method of manufacturing a scattering-type liquid crystal display device, comprising a step C of forming a liquid crystal layer. In the step B, when the rectangular opening region and the rectangular light shielding region are provided, the width of the rectangular opening region is S1, and the rectangular light shielding region is L1, the width S1 and the width L1 10. The method for manufacturing a scattering type liquid crystal display device according to claim 9, wherein a mask satisfying S1 + L1 ≦ 30 μm is used. The method of manufacturing a scattering type liquid crystal display device according to claim 10, wherein the rectangular opening regions and the rectangular light shielding regions are formed in parallel and alternately. The step B includes a step B1 of irradiating the photo-alignment film with light.
The method of manufacturing a scattering type liquid crystal display device according to claim 9, wherein the number of times of light irradiation is one. The method for manufacturing a scattering type liquid crystal display device according to any one of claims 9 to 12, wherein the step C does not include a monomer polymerization step for imparting scattering ability.

Images