JP2006337463A - Polarizing plate, its manufacturing method and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate capable of reducing processes, omitting adhesive layer, protective layer and the like and reducing the cost while reflections caused by every layers can be reduced because a directive diffuser does not need to be attached with adhesive material or the like. <P>SOLUTION: The polarizing plate in which a polarizer is held between supporting layers is characterized in that the directive diffuser composed of a specified refractive index region and a slender pillar-shaped refractive index region having a refractive index different from that of the specified refractive index region is disposed between the polarizer and one side supporting layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a polarizing plate having an angle dependency in light scattering characteristics, such as a scattering property that varies depending on the incident direction of light (or having an incident angle selectivity), a manufacturing method thereof, and a liquid crystal display device. Yes,
In particular, with respect to a diffusion film used to widen the viewing angle by installing on the front surface of the liquid crystal display device, by enabling the layer configuration at the time of installation to the liquid crystal display device can be simplified,
The present invention relates to a polarizing plate that is useful for improving the image quality of a display device by reducing noise light due to reflection on the boundary surface of each layer as well as reducing the overall cost, a manufacturing method thereof, and a technology related to a liquid crystal display device. ,

  The transmissive liquid crystal display device is a display element typified by a flat panel display, and has the advantages of being light and thin and having low power consumption. For this reason, it has been widely used for LCD TVs, car navigation systems, personal computer monitors, and the like.

  However, the transmissive liquid crystal display device has a characteristic that the viewing angle dependence is large, and what is supposed to be displayed in black when viewed from an oblique direction more than a certain angle looks whitish, or the gradation is reversed. There is a problem that the display contents cannot be read accurately by a person.

  For example, in a general TN alignment liquid crystal display device, gradation inversion occurs when the angle exceeds 5 ° in the downward direction, and the contrast ratio decreases to 10 or less when it exceeds 30 ° and 50 ° below. Here, the gradation inversion means that the order of the original gradation recognized in the front is reversed when viewed from a certain oblique direction, and the contrast ratio is white display brightness / black display brightness.

  Normally, LCD TVs, car navigation systems, etc. are often observed by people from an oblique direction, so a transmissive liquid crystal display device is required in which the black display does not become whitish from any direction and the gradation is not lost. ing.

  Therefore, in order to improve the viewing angle dependency of this type of liquid crystal display device, for example, a viewing angle improving liquid crystal display device using a retardation compensation film having negative refractive index anisotropy has been proposed (for example, Patent Document 1) (FIG. 3). In this method, the viewing angle can be improved in seven directions when the image is divided into eight directions without degrading the image quality.

  However, in the method using such a film, there is one direction in which correction cannot be performed in principle (usually downward), and color change or gradation inversion occurs in that direction. was there.

  Accordingly, the applicants have proposed a directional diffuser in which a long columnar region having a different refractive index as shown in FIG. This proposes a method of installing and using (FIG. 5).

  In a directional diffuser having a so-called kala-silencer-like structure comprising a specific refractive index region and a long and narrow columnar refractive index region having different refractive indexes as shown in FIG. The light is less scattered and can be given a characteristic of strongly diffusing in a direction along the cone at an angle as schematically shown in FIG.

Therefore, when such a method is taken, the image quality is improved by bringing light in a different direction (lateral direction) on a concentric circle with respect to the direction of inversion (downward direction) without affecting the front direction. Since it is averaged, image quality deterioration can be reduced, so that the viewing zone can be enlarged while maintaining the image quality in the front direction.

  In addition, the directional diffusion film having such a structure of calacylenecon is produced by, for example, the following method.

  First, a light-sensitive material having tackiness is recorded on the base film so that a difference in exposure amount is recorded as a difference in refractive index. Then, a diffusion film having no birefringence is laminated thereon to produce a film in which the photosensitive material 1 is sandwiched between the base film 2 and the diffusion film 3 as shown in FIG. As the photosensitive material used in this case, for example, OMNIDEX 352 manufactured by DuPont can be considered. As the diffusion film 3 having no birefringence, for example, a polycarbonate surface relief diffusion film prepared without stretching can be considered.

  Using this sandwich-shaped film, for example, a system as shown in FIG. 8 is used to irradiate the laser parallel light 5 from the diffusion film 3 side while feeding the film 4.

  At this time, the laser light that has passed through the diffusion film 3 forms a speckle pattern that is elongated in the traveling direction as shown in FIG. 9 due to interference. A speckle pattern is a bright and dark spot pattern that occurs when light with good coherence is scattered or reflected or transmitted by a rough surface. Light scattered by minute irregularities on the rough surface interferes with an irregular phase relationship. It happens.

  For this reason, a pattern in which the speckle pattern is divided by the thickness of the photosensitive material 1 as shown in FIG. 10 is recorded on the photosensitive material 7, and as a result, a kalashenkon pattern is recorded. .

  By removing the original diffusion film from the photosensitive material film and carrying out development treatment, a directional diffuser having a glassylencon-like configuration with a different refractive index can be obtained.

  However, when this method is actually used, since the directional diffuser comes to the outermost surface when the directional diffuser is provided on the polarizing plate, very high resistance is required. Since an actual directional diffuser is usually made by recording on a photopolymer light-sensitive material, its resistance is weak. In reality, a protective layer 7 is provided on the directional diffuser 6 as shown in FIG. The adhesive layer 8 for bonding is used when adhering.

  For this reason, the layer structure increases, and material costs for the protective layer, the adhesive layer, etc., in addition to the directional diffuser, are increased. Moreover, the process of bonding an adhesion layer, the process of bonding a protective layer, etc. are required also in a process, and a process increases. For this reason, the cost was considerably increased.

  In addition, since the refractive indexes of the respective layers do not completely coincide with each other, the reflected light at the boundary surface increases as the number of layers increases. For this reason, noise due to reflected light is increased, leading to deterioration in image quality of the liquid crystal display device.

The patent literature is as follows.
JP-A-7-159614

  As described above, the directional diffuser with a glass-silencer-like structure is installed in front of the front polarizing plate of the liquid crystal panel, thereby eliminating the inversion of the liquid crystal panel and enlarging the viewing area, and the layer structure is complicated. However, there is a problem that the cost is increased due to an increase in processes and materials to be used, and a problem that noise is increased due to reflection by each layer because the layer configuration is increased.

  The present invention has been made in order to solve such problems, and aims to reduce the cost of processes and materials by reducing the layer configuration, and to reduce noise caused by reflected light. Yes.

In order to solve the above problems, the invention of claim 1
In a polarizing plate in which a polarizer is sandwiched between support layers, a directional diffuser composed of a long columnar columnar refractive index region having a refractive index different from that of a specific refractive index region is different from that of the polarizer. A polarizing plate is proposed which is provided between the supporting layer and the support layer.

  When a directional diffuser is used in such a configuration, the directional diffuser does not have to be bonded with an adhesive material, etc., so the number of processes is reduced and the adhesive material layer, the protective film layer, etc. are reduced. Reflection by each layer can be reduced.

In the inventions of claims 2 and 7,
7. The polarizing plate according to claim 1 or 6, and a manufacturing method thereof, wherein the columnar refractive index region is elongated in a direction perpendicular to the surface of the directional diffuser.

  When the polarizing plate has such a structure, backscattering with respect to external light is reduced.

In invention of Claim 3 and 8,
The polarizing plate according to claim 1, 2, 6, or 7, and a method for manufacturing the polarizing plate, characterized by containing a vinyl acetate resin as a material of the directional diffuser.

  If it does in this way, the adhesiveness of a support layer and a directional diffuser will become favorable.

In the inventions of claims 4 and 9,
The polarizing plate according to any one of claims 1 to 3 and 6 to 8, wherein the surface of the directional diffuser that contacts the polarizer is a saponification-treated surface, and a method for manufacturing the polarizing plate.

  If it does in this way, adhesiveness with a support layer will become favorable.

In the invention of claim 5,
A liquid crystal display device using the directional diffuser of claim 1 is proposed.

In the invention of claim 6, a diffusion film is adhered and laminated on the photosensitive material in a state where the support layer and the photosensitive material having a characteristic that the refractive index changes upon exposure, and the laser beam is irradiated from the diffusion film side to diffuse. The speckle pattern of the laser beam generated in the diffusion film is used as a refractive index distribution in the photosensitive material by a method for producing a polarizing plate characterized by peeling the film and laminating the polarizer and the other support layer. A method for producing a polarizing plate is proposed in which recording is performed, and then the photosensitive material is saponified to provide adhesion to the support layer.

In the invention of claim 10, the laser irradiation is carried in a state in which a diffusion film is closely laminated on the photosensitive material in a state in which the photosensitive material having such a characteristic that the refractive index changes upon exposure is laminated. The manufacturing method of the polarizing plate in any one of Claim 6 to 9 characterized by performing to this is proposed.
Thus, an efficient method for manufacturing a polarizing plate is proposed.

  In the present invention, when a directional diffuser using a material capable of improving the adhesion between the support layer and the polarizer is used in a liquid crystal display device, the support layer on the front side of the liquid crystal display device, the polarizer, Because it is installed and used between the two, the layer structure associated with the installation of the directional diffuser is reduced to reduce the cost of processes and materials, and the noise due to reflection is reduced to improve the image quality of the liquid crystal display device. Can do.

  Hereinafter, the method of the present invention will be described in detail with reference to the drawings.

  Normally, as shown in FIG. 12, the polarizing plate used in a liquid crystal display device has a structure in which a polarizer 9 made of PVA is sandwiched between two TAC films as a support layer. Such an example will be described. As shown in FIG. 1, a directional diffuser is used between a polarizer 9 made of PVA in such a polarizing plate and a TAC film 10 as a support layer, which is used on the front surface of a liquid crystal display device. 11 will be described below.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration when the polarizing plate of claim 1 of the present invention is used in a liquid crystal display device. In this figure, the directional diffuser 11 is disposed between a TAC film 10 on the front surface forming a polarizing plate on the front surface of the liquid crystal display device and a polarizer 9 made of PVA.

  In this configuration, since the TAC film 10 is present in front of the directional diffuser 11, a protective layer for the directional diffuser is unnecessary. For this reason, since the layer corresponding to the protective layer 7 and the adhesion layer 8 of the structure of the conventional FIG. 11 decreases, the material cost with respect to these can be reduced. Further, since the number of layers is reduced by the amount corresponding to the protective layer 7 and the adhesive layer 8, noise due to reflection of external light at the boundary surface is reduced.

  An example of a method for manufacturing a polarizing plate having such a directional diffuser will be described later in the process.

  First, a photosensitive material that has good adhesion to the TAC film and that records the difference in exposure amount as the difference in refractive index is coated on the TAC film. As such a photosensitive material, for example, a photopolymer containing a vinyl acetate resin as a binder polymer can be considered.

  A web in which a diffusion film having no birefringence is laminated on such a photosensitive material and the photosensitive material 1 is sandwiched between the TAC film 2 and the diffusion film 3 as shown in FIG. Is made. As the diffusion film used at this time, for example, a diffusion film obtained by relief-treating the surface of a polycarbonate produced without stretching can be considered.

  Using this web, a parallel laser beam 5 is irradiated from the diffusion film 3 side while feeding the web 4 by a system as shown in FIG.

  In this way, by recording a speckle pattern having a shape elongated in the traveling direction on the photosensitive material due to interference, a specific refractive index region and a specific refractive index region of the photosensitive material have a long and narrow columnar shape with different refractive indexes. A so-called karashirenkon pattern consisting of a columnar refractive index region is recorded and becomes a directional diffuser 11.

  When the original diffusion film is peeled from the web and developed, a directional diffuser having a structure of a calacylenecone having a different refractive index is adhered to the TAC film.

  Next, the saponification treatment is performed on the product thus obtained. Vinyl acetate resin does not have strong adhesion to a polarizer such as PVA. However, when saponification treatment is performed on the directional diffuser, the acetate group of the vinyl acetate resin contained on the surface of the directional diffuser is replaced with a hydroxyl group, so this portion has the same structure as PVA. For this reason, strong adhesiveness comes to be obtained between the polarizers made of PVA.

  Thus, when the manufactured TAC film to which the directional diffuser is in close contact is used in a normal polarizing plate manufacturing process, a glassylon-cone shape is formed between the TAC film forming the support layer and the polarizer made of PVA. A polarizing plate provided with a directional diffuser can be manufactured.

  The production of the directional diffuser portion of the polarizing plate by this method can be carried out in substantially the same steps as those of the conventional polarizing plate except for the saponification step.

  On the other hand, since the TAC film is usually used after being saponified in the manufacturing process of the polarizing plate, considering the entire manufacturing process of the polarizing plate, the fact that the saponification treatment process is included does not increase the number of processes.

  For this reason, the process of pasting the adhesive layer and the process of pasting the protective layer, which were necessary as a process after manufacturing the directional diffuser by the conventional method, is unnecessary, so the manufacturing process can be reduced and the manufacturing cost can be reduced. can do.

  Hereinafter, the method of the present invention will be described in detail with reference to the drawings.

  First, from a photopolymer that contains a vinyl acetate resin as a binder polymer that has good adhesion to a TAC film of 80 μm thickness (manufactured by Fuji Photo Film Co., Ltd.) and that records the difference in exposure as the difference in refractive index. The resulting photosensitive material is coated on the TAC film by a thickness of 20 μm.

  FIG. 7 shows a laminate of a diffusion film which is made of a non-stretched polycarbonate having no birefringence with a thickness of 100 μm from the top of such a photosensitive material and whose surface is relief-treated by an extrusion method using a relief pattern. In addition, a web in which the photosensitive material 1 is sandwiched between the TAC film 2 and the diffusion film 3 is manufactured.

  Using this web, a parallel laser beam 5 having a wavelength of 355 nm is irradiated from the diffusion film side 31 while feeding the web 4 by a system as shown in FIG.

In this way, by recording a speckle pattern having a shape elongated in the traveling direction on the photosensitive material due to interference, a specific refractive index region and a specific refractive index region of the photosensitive material have a long and narrow columnar shape with different refractive indexes. A so-called karashirenkon pattern consisting of a columnar refractive index region is recorded and becomes a directional diffuser 11.

  When the original diffusion film is peeled from the web and developed, a directional diffuser having a structure of a calacylenecone having a different refractive index is adhered to the TAC film.

  Next, the product thus obtained is subjected to a saponification treatment with a strong alkali.

  In this way, when the manufactured TAC film with the directional diffuser adhered thereto is used in a normal polarizing plate manufacturing process, the TAC film that forms a support layer having a thickness of 80 μm and a polarizer made of PVA are used. It is possible to manufacture a polarizing plate in which a glass-silenced directional diffuser is installed.

  The production of the directional diffuser portion of the polarizing plate by this method can be carried out in substantially the same steps as those of the conventional polarizing plate except for the saponification step.

  On the other hand, since the TAC film is usually used after being saponified in the manufacturing process of the polarizing plate, considering the entire manufacturing process of the polarizing plate, the fact that the saponification treatment process is included does not increase the number of processes.

  For this reason, the process of pasting the adhesive layer and the process of pasting the protective layer, which were necessary as a process after manufacturing the directional diffuser by the conventional method, is unnecessary, so the manufacturing process can be reduced and the manufacturing cost can be reduced. can do.

  The present invention relates to a directional diffuser and a polarizing plate that are installed in front of a liquid crystal display device and used to widen the viewing angle.

It is a schematic sectional drawing which shows an example of a structure when the directional diffuser of this invention is installed in the polarizing plate. It is a schematic sectional drawing which shows an example of a structure in the case of installing the polarizing plate of this invention in a liquid crystal display device. It is a conceptual sectional view showing an example of a liquid crystal display device using the conventional phase difference compensation film. It is a schematic perspective view which shows an example of a structure of a directional diffuser. It is a conceptual sectional view showing a liquid crystal display device using a directional diffuser and a phase difference compensation film. It is a general | schematic perspective view which shows the mode of the diffused light of a directional diffuser. It is a general | schematic sectional drawing which shows an example of the relationship between the photosensitive material in a manufacturing method of a polarizing plate, an original plate film, etc. It is a general | schematic process figure which shows an example of the exposure system in the manufacturing method of a polarizing plate. It is an outline sectional view for explaining a principle of a manufacturing process of a directional diffuser. It is a schematic sectional drawing for the principle explanation in the manufacturing process of a directional diffuser. It is a schematic sectional drawing which shows the structural example in the case of actually installing a directional diffuser in a liquid crystal display device. It is a schematic sectional drawing which shows the conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive material 2 TAC film 3 Diffusion film 4 Web 5 Laser beam 6 Directional diffuser 7 Adhesive layer 8 Protective layer 9 Polarizer 10 TAC film 11 Directional diffuser 12 Speckle pattern 13 Diffusion film side 14 Developing device 15 Unwinding roll 16 Winding roll 21 High refractive index region 22 Low refractive index region 31 Polarizing plate 32 Phase difference compensation film 33 Polarizing plate with diffuser 34 TN liquid crystal cell 35 Backlight 36 Directional diffusion film

Claims (10)

  In a polarizing plate in which a polarizer is sandwiched between support layers, a directional diffuser composed of a long columnar columnar refractive index region having a refractive index different from that of a specific refractive index region is different from that of the polarizer and one of the specific refractive index regions. A polarizing plate provided between the support layer and the support layer.   2. The polarizing plate according to claim 1, wherein the columnar refractive index region is elongated in a direction perpendicular to the surface of the directional diffuser.   The polarizing plate according to claim 1 or 2, wherein a vinyl acetate resin is included as a material of the directional diffuser.   The polarizing plate according to any one of claims 1 to 3, wherein a surface of the directional diffuser that contacts the polarizer is a saponification-treated surface.   A liquid crystal display device comprising the polarizing plate according to claim 1.   In the state where the support layer and the photosensitive material whose refractive index changes depending on the exposure, are laminated, a diffusion film is adhered and laminated on the photosensitive material, laser irradiation is performed from the diffusion film side, the diffusion film is peeled off, and polarization is performed. A method for producing a polarizing plate, comprising laminating a child and the other support layer.   The method for producing a polarizing plate according to claim 6, wherein the laser irradiation is perpendicular to the surface of the directional diffuser.   The method for producing a polarizing plate according to claim 6 or 7, wherein the photosensitive material contains a vinyl acetate resin.   9. The polarizing plate according to claim 6, wherein a surface of the directional diffuser in contact with the polarizer is saponified between the polarizer and the other support layer after the diffusion film is peeled off. Production method.   Laser irradiation is performed for a state in which a diffusion film is closely laminated and conveyed on a photosensitive material in a state where a photosensitive material having a characteristic that the refractive index changes by exposure is laminated. The method for producing a polarizing plate according to claim 6, wherein the method is characterized in that:

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