JP2007072239A - Viewing angle controlling element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viewing angle controlling element capable of controlling a viewing angle on a display screen while suppressing the degradation of luminance. <P>SOLUTION: The viewing angle controlling element is constituted by integrating: a louver layer 1 in which a light transmitting band 11 and a light shielding band 12 are alternately arranged; and a polarizing plate 5 which absorbs other polarization components. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a viewing angle control body suitable as a constituent member of a liquid crystal display device, for example.

FIG. 4 is a schematic configuration diagram showing an example of a conventional liquid crystal display device. The liquid crystal display device of this example includes a liquid crystal panel 20 and a backlight unit 30 provided on the back side (opposite side to the viewing side) of the liquid crystal panel.
In the liquid crystal panel 20, the first polarizing plate 22 is laminated and integrated on one surface of the liquid crystal cell 21, and the second polarizing plate 24 is stacked and integrated on the other surface of the liquid crystal cell 21. Reference numeral 23 in the figure denotes a phase plate, which is provided as necessary.
Further, by providing a louver layer 31 in which light transmission bands and light shielding bands are alternately arranged between the liquid crystal panel 20 and the backlight unit 30, light incident on the liquid crystal cell 21 from the backlight unit 30 is provided. A configuration for controlling the incident angle is known (for example, Patent Document 1 below).
JP-A-5-61034

  By incorporating the louver layer 31 in the liquid crystal display device as described above, the viewing angle on the display screen can be controlled and the contrast can be improved. On the other hand, the luminance is lowered compared to the case where the louver layer 31 is not incorporated. There is a problem that it ends up.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a viewing angle control body that can control the viewing angle on a display screen while suppressing a decrease in luminance.

  As a result of studies by the present inventors in order to achieve the above object, in the conventional configuration, when a louver layer is incorporated in the liquid crystal display device, the backlight unit and Since the liquid crystal cell and the louver were arranged separately, an air layer was interposed between these members, and light reflection occurred at the interface between the two layers having different refractive indexes. It was found that this is one of the causes of the decrease in brightness. As a result of studying a configuration for reducing such interface reflection, the present invention has been completed.

  That is, the viewing angle control body of the present invention includes a louver layer in which light transmission bands and light shielding bands are alternately arranged, and a polarizing plate that selectively transmits a predetermined polarization component and absorbs other polarization components. And are integrated.

  The viewing angle control body of the present invention is arranged on the optical path of the liquid crystal display device from which the light emitted from the backlight unit passes through the liquid crystal cell and reaches the display screen, thereby suppressing a decrease in luminance. The viewing angle on the display screen can be controlled.

<First embodiment>
1 and 2 show a first embodiment of a viewing angle control body of the present invention. FIG. 1 is a perspective view, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. The drawing schematically shows an enlarged part of the viewing angle control body.
The viewing angle control body of the present embodiment includes a first adhesive layer 2 and a first transparent protective layer 3 on one surface of a louver layer 1 in which light transmission bands 11 and light shielding bands 12 are alternately arranged. The adhesive layer 4 and the polarizing plate 5 are laminated in order from the louver layer 1 side. A second transparent protective layer 7 is provided on the other surface of the louver layer 1 via a second adhesive layer 6.

[Louvre layer]
When the thickness direction of the louver layer 1 is the Z direction and the two directions perpendicular to each other in the plane perpendicular to the Z direction are the X direction and the Y direction, respectively, the light transmission band 11 and the light shielding band 12 constituting the louver layer 1. Are band-shaped extending in the X direction, and a plurality of light transmission bands 11 and a plurality of light shielding bands 12 are alternately arranged in the Y direction. The widths of the plurality of light transmission bands 11 in the Y direction are uniform and constant in the X direction. The widths of the plurality of light shielding bands 12 in the Y direction are also uniform and constant in the X direction.

  As the material of the light transmission band 11, a highly transparent resin is used. Specifically, a resin having high transparency such that the light transmittance when light is transmitted in the Z direction in the figure with respect to only the light transmission band 11 is 75% or more, preferably 85% or more. Material is preferred. For example, highly transparent thermoplastic resins and thermosetting resins are used. Specific examples include cellulose resins, polyolefin resins, polyester resins, silicone resins, polystyrene resins, polyvinyl chloride resins, acrylic resins, polycarbonates. Examples thereof include resins. Of these, silicone resins are preferred, and silicone rubber is particularly preferred from the viewpoint of heat resistance.

Note that the value of “light transmittance” in this specification is D ₆₅ defined in JIS Z 8720 as a light source, and in the apparatus for measuring the intensity of inspection light emitted from the light source with a light receiving sensor, the inspection light is used. The output value of the light receiving sensor when there is no object to be measured on the optical path is set to A, the object to be measured is set on the optical path of the inspection light, and the transmitted light transmitted through the object to be measured is received by the light receiving sensor. When the output value of B is B, the light transmittance = (B / A) × 100 (unit:%).

As the material of the light-shielding band 12, a colored resin obtained by using the above-described resin as the material of the light-transmitting band 11 as a base material and adding a colorant such as a pigment or a dye thereto is suitably used. The shade of the light-shielding band 12 is usually black, but may be gray, red, yellow, green, blue, light blue, or the like depending on circumstances. The color tone of the shading band 12 can be adjusted by the type and amount of the colorant. Specifically, it is preferable that only the light-shielding band 12 has a light-shielding property so that the light transmittance when light is transmitted in the Y direction in the figure is 40% or less, preferably 10% or less.
Specific examples of the colorant include general organic pigments or inorganic pigments such as carbon black, benkara, iron oxide, titanium oxide, yellow iron oxide, disazo yellow, and phthalocyanine blue. One colorant may be used, or two or more colorants may be used. When a black pigment is not used, it is preferable to use a white pigment in combination in order to obtain good light shielding properties.
In the louver layer 1, the resin material forming the light transmission band 11 and the resin material as the base material of the light shielding band 12 may be the same or different. From the point of adhesiveness to 12, it is preferable that both are the same.

In the louver layer 1, the viewing angle θ in a plane perpendicular to the X direction (the paper surface in FIG. 2) is determined by the thickness of the light transmission band 11 in the Z direction and the width in the Y direction. Further, the ratio of the width of the light transmission band 11 to the width of the light shielding band 12 in the Y direction affects the transmittance of light rays parallel to the Z direction.
Specifically, the viewing angle θ in the louver layer 1 is preferably in the range of 30 to 150 °, more preferably 60 to 120 °.
The thickness T in the Z direction of the light transmission band 11 is preferably about 0.1 to 2.5 mm, and more preferably about 0.14 to 0.4 mm.
The width W1 in the Y direction of the light transmission band 11 is preferably in the range of 50 μm to 0.3 mm, and more preferably in the range of 75 μm to 0.2 mm.
The width W2 of the light shielding band 12 in the Y direction is preferably in the range of 5 μm to 50 μm, and more preferably in the range of 15 μm to 30 μm.
The thickness T of the light shielding band 12 in the Z direction is the same as the thickness T of the light transmission band 11.

  The louver layer 1 having such a configuration can be manufactured as follows. First, a plurality of sheets of the first sheet made of the constituent material of the light transmission band 11 and the thickness W1 and a plurality of sheets of the second sheet made of the constituent material of the light shielding band 12 and the thickness W2 Are alternately laminated, and heated and pressed to form a block body in which the plurality of sheets are integrated. Next, the louver layer 1 is obtained by slicing the block body along a cut surface perpendicular to the sheet surface. The thickness (slice width) when slicing is the above T.

[First and second adhesive layers]
The material of the first adhesive layer 2 between the louver layer 1 and the first transparent protective layer 3 and the material of the second adhesive layer 6 between the louver layer 1 and the second transparent protective layer 7 are cured. An adhesive having transparency later is preferred. Specifically, the light transmittance of the single layer of the adhesive layer 2 after curing the adhesive is preferably 65% or more, and more preferably 80% or more.
For example, a thermosetting adhesive, a multi-component reaction adhesive, an ultraviolet curable adhesive, and the like can be given. Specifically, epoxy adhesives, urethane adhesives, acrylic adhesives, melamine adhesives, polyester adhesives, silicone adhesives, and the like can be suitably used.
Among these, it is more preferable to use the same type of adhesive as the louver layer 1 in order to obtain good adhesion to the louver layer 1. For example, when the louver layer 1 is made of silicone rubber, it is preferable to use a silicone-based adhesive.
The first adhesive layer 2 and the second adhesive layer 6 may be made of the same material, or may be made of different materials.

[Transparent protective layer]
As materials for the first transparent protective layer 3 and the second transparent protective layer 7, the resins listed above as the material of the light transmission band 11 can be used. For each of the first transparent protective layer 3 and the second transparent protective layer 7, the light transmittance when light is transmitted in the Z direction in the figure is preferably 75% or more, and 85% More preferably.
The materials of the first transparent protective layer 3 and the second transparent protective layer 7 are polycarbonate resin, polyester resin, acrylic resin, polyolefin resin (especially cycloolefin polymer), particularly from the viewpoint of transparency and heat resistance. Cellulosic resins are preferred, with polycarbonate and polyester resins being more preferred.
If the thickness of the first transparent protective layer 3 and the second transparent protective layer 7 in the Z direction is too thin, a sufficient protective function cannot be obtained, and the light transmittance decreases as the thickness increases. About 0.5 mm is preferable, and about 0.1-0.2 mm is more preferable.
The 1st transparent protective layer 3 and the 2nd transparent protective layer 7 may consist of the same material, and may consist of a mutually different material. Moreover, both thickness may be the same or different.

[Polarizer]
The polarizing plate 5 selectively transmits a predetermined polarization component and absorbs and / or scatters other polarization components. For example, when natural light is incident, only one of two orthogonally polarized components of the incident light is selectively transmitted, and the other is shielded by absorption and / or scattering, not by reflection, What has a function which changes the incident natural light into a linearly polarized light and emits it is used. The transmittance of the polarizing plate 5 is generally 30 to 50%, preferably 40 to 50%.
The polarizing plate 5 is not particularly limited as long as it has such a function, and various commercially available polarizing plates for liquid crystal display devices can be appropriately used. A film-like polarizing plate is preferably used.
For example, a polarizing film formed by dying dichroic materials such as iodine and organic dyes on a base material made of a polyvinyl alcohol thin film to develop absorption dichroism by highly stretching and orienting the dichroic material, acetic acid A laminated film integrated between two protective films made of cellulose (TAC: cellulose triacetate) is preferably used.

[Adhesive layer]
The adhesive layer 4 is formed using an adhesive such as an adhesive or a pressure-sensitive adhesive. Here, the adhesive is one that loses tackiness by being cured after sticking, and the pressure-sensitive adhesive means one that maintains a certain degree of tackiness even after sticking. In any case, it is preferable that the adhesive layer 4 has transparency, and a light beam when light is transmitted in the Z direction in the figure with respect to a single element of the adhesive layer 4 (after the adhesive is cured). The transmittance is preferably 75% or more, and more preferably 85% or more.
Examples of the adhesive constituting the adhesive layer 4 include the adhesives mentioned above as materials for the first adhesive layer 2 and the second adhesive layer 6.
The pressure-sensitive adhesive constituting the adhesive layer 4 is not particularly limited as long as it has such a pressure-sensitive adhesive force that it can be removably bonded to the polarizing plate 5 and is preferably highly transparent. Moreover, when the polarizing plate 5 is peeled off, it is preferable that there is little adhesive residue. For example, a commercially available material can be used as the removable adhesive. Specific examples of the removable adhesive include acrylic adhesives, urethane adhesives, rubber adhesives, and the like.
Alternatively, the releasable adhesive layer 4 can also be obtained by mirror-treating the surface (adhesive surface with the polarizing plate 5) of a layer made of an elastomer (including a low-crosslink density gel-like substance). Specific examples of the elastomer include silicone rubber, silicone gel, urethane rubber, and urethane gel.
Among these, acrylic adhesives are particularly preferable in terms of repairability and adhesive strength.
If the thickness of the adhesive layer 4 in the Z direction is too thin, the adhesive strength decreases, and the thicker the light transmittance decreases, the preferable range is about 0.01 to 0.5 mm, and about 0.02 to 0.1 mm. Is more preferable.
For example, a commercially available transparent adhesive tape can be used as the adhesive layer 4.

[Production method]
The viewing angle control body of this embodiment can be manufactured, for example, by the following method. First, the louver layer 1 is produced.
Separately from this, a first transparent protective layer 3 is prepared, and an adhesive constituting the first adhesive layer 2 is applied to one surface thereof, and one of the first transparent protective layer 3 and the louver layer 1 is applied. After bonding the surfaces together via the adhesive, the adhesive is cured.
In addition, a second transparent protective layer 7 is prepared separately, and an adhesive constituting the second adhesive layer 6 is applied to one surface thereof, and the other surface of the second transparent protective layer 7 and the louver layer 1 is applied. Are bonded together via the adhesive, and then the adhesive is cured.
Next, the adhesive layer 4 is provided on the other surface of the first transparent protective layer 3, and the polarizing plate 5 is attached via the adhesive layer 4, whereby the viewing angle control body of this embodiment is obtained. . The polarizing plate 5 that has already been integrated with a liquid crystal cell or the like may be used.

In the viewing angle control body of the present invention, when the polarizing plate 5 has a function of obtaining linearly polarized light, the transmission axis of the polarizing plate 5 (intersection between the polarizing plane of linearly polarized light that passes through the polarizing plate and the polarizing plate) and polarized light Laminates other than the plate 5 (in this embodiment, the adhesive layer 4, the first transparent protective layer 3, the first adhesive layer 2, the louver layer 1, the second adhesive layer 6, and the second transparent protective layer 7) It is preferable that either the slow axis or the fast axis in the laminate) is parallel.
The slow axis or the fast axis of the above “laminate other than the polarizing plate 5” is the slow axis or the fast axis when the entire laminate is regarded as an integral birefringence medium. It is determined by the sum of the optical characteristics of the layers constituting the layer.
Thus, by making the transmission axis of the polarizing plate 5 parallel to the slow axis or the fast axis in the laminate other than the polarizing plate 5, the linearly polarized light passes through the laminate and then enters the polarizing plate 5. In both cases where the light is incident and linearly polarized light transmitted through the polarizing plate 5 is transmitted through the laminate, the influence of the laminate on the polarization state obtained by the polarizing plate 5 can be reduced. .

The viewing angle control body of this embodiment is used as a component of a liquid crystal display device.
For example, the polarizing plate 5 constituting the viewing angle control body of this embodiment can be used as one of the polarizing plates disposed on both sides of the liquid crystal cell. In other words, a liquid crystal display device can be configured by arranging the polarizing plate 5 of the viewing angle control body of the present embodiment, which is further integrated with a liquid crystal cell, the other polarizing plate, and the like on the viewing side of the light source. .
Specifically, a configuration in which the louver layer 1, the polarizing plate 5, the liquid crystal cell, and the other polarizing plate are arranged in this order from the light source side, or the other polarizing plate, the liquid crystal cell, the polarizing plate 5, and the louver from the light source side. It can be set as the structure arrange | positioned in order of the layer 1. FIG.

Or as the polarizing plate 5 which comprises the viewing angle control body of this embodiment, the antireflection polarizing plate provided in the visual recognition side of a liquid crystal cell can be used.
For example, when a touch panel is provided on the viewing side of a display element such as a liquid crystal panel, the touch panel, the polarizing plate (antireflection polarizing plate) 5 and the louver layer 1 (outermost layer) are arranged in this order from the liquid crystal panel side. can do. In this configuration, the touch panel and the polarizing plate (antireflection polarizing plate) 5 may be bonded and integrated, or may be separate.

Furthermore, the viewing angle control body of the present invention can be arranged such that the louver layer 1 is closer to the liquid crystal cell than the polarizing plate 5.
For example, a configuration in which the polarizing plate 5, the louver layer 1, the liquid crystal cell, and the other polarizing plate are arranged in this order from the light source side, or the other polarizing plate, the liquid crystal cell, the louver layer 1, and the polarizing plate 5 from the light source side. A configuration in which the touch panel, the louver layer 1 and the polarizing plate (antireflection polarizing plate) 5 (outermost layer) are arranged in this order from the liquid crystal panel side are also possible.

In the liquid crystal display device configured as described above, the traveling direction of the light emitted from the light source and transmitted through the liquid crystal cell to the display screen is limited by the louver layer 1 of the viewing angle control body. This limits the viewing angle on the display screen and improves contrast.
In addition, since no air layer is interposed between the louver layer 1 and the polarizing plate 5, reflection of light at the interface between the air layer and another layer can be reduced. Thereby, the transmission loss of the light which reaches | attains a display screen among the lights radiate | emitted from a light source can be reduced, and the brightness | luminance in a display screen can be improved.
Further, in particular, according to the configuration of the present embodiment, since the louver layer 1 has a sandwich structure sandwiched between the first transparent protective layer 3 and the second transparent protective layer 7, the symmetry of the structure increases, Structural stability is improved, for example, warpage hardly occurs.

<Second Embodiment>
FIG. 3 is a sectional view showing a second embodiment of the viewing angle control body of the present invention. The difference between the viewing angle control body of the present embodiment and the first embodiment is that the louver layer 1 and the polarizing plate 5 are laminated and integrated through the adhesive layer 4, and the first is between them. The adhesive layer 2 and the first transparent protective layer 3 are not interposed. In FIG. 3, the same components as those of FIG.

According to the configuration of the present embodiment, similarly to the first embodiment, it is possible to control the viewing angle and improve the contrast on the display screen, and at the same time, it is possible to improve the luminance by reducing the transmission loss.
In particular, according to the configuration of the present embodiment, since the first adhesive layer 2 and the first transparent protective layer 3 are not interposed between the louver layer 1 and the polarizing plate 5, these laminates are This is advantageous in reducing the thickness, and light transmission loss is further reduced.

Examples are given below, but the present invention is not limited to these examples.
Example 1
A viewing angle control body having the configuration shown in FIGS.
First, a first sheet made of transparent silicone rubber (trade name: KE153U, manufactured by Shin-Etsu Chemical Co., Ltd.) having a thickness of 200 μm was prepared as the light transmission band 11.
Separately, a second sheet having a thickness of 20 μm made of a material obtained by adding 15 parts by mass of carbon black to 100 parts by mass of transparent silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KE153U) as the light shielding band 12. Prepared.
A plurality of first sheets and a plurality of second sheets were alternately laminated, heat vulcanized and pressurized to form a block body in which these sheets were integrated.
Subsequently, the louver layer 1 was produced by slicing the block body to a thickness of 360 μm at a cut surface perpendicular to the sheet surface.

Subsequently, a polycarbonate sheet (first transparent protective layer 3) coated with a thermosetting adhesive (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KE1825) as the first adhesive layer 2 was used as the louver layer obtained above. The adhesive was heat cured.
Also, a polycarbonate sheet (second transparent protective layer 7) coated with a thermosetting adhesive (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KE1825) as the second adhesive layer 6 on the other surface of the louver layer 1. ) And the adhesive was thermally cured.
The viewing angle θ in the laminate thus obtained was 120 °.
Furthermore, on the first transparent protective layer (polycarbonate sheet) 3 of the laminate, a transparent adhesive tape (manufactured by Sekisui Chemical Co., Ltd., product name: double tack tape # 5511) was applied to form an adhesive layer 4.
A liquid crystal display device for Play Station Portable-1000 manufactured by SONY is prepared, and the laminate obtained as described above is placed on the polarizing plate on the backlight unit side of the liquid crystal panel constituting the device. 4 was attached to the liquid crystal display device.

(Comparative Example 1)
In the same manner as in Example 1, a laminate composed of the louver layer 1, the first adhesive layer 2, the first transparent protective layer 3, the second adhesive layer 6, and the second transparent protective layer 7 was produced. The adhesive layer 4 was not provided.
The same liquid crystal display device as in Example 1 was prepared, and the laminate obtained above was not integrated with the polarizing plate of the liquid crystal panel between the liquid crystal panel constituting the device and the backlight unit. Incorporated.

  With respect to the liquid crystal display devices obtained in Example 1 and Comparative Example 1, the luminance on the display screen when image display was performed under the same conditions was measured. As a result, Example 1 was compared with Comparative Example 1. The brightness is improved by about 10%.

1 is a perspective view showing a first embodiment of the present invention. It is sectional drawing which follows the II-II line | wire in FIG. It is sectional drawing which shows the 2nd Embodiment of this invention. It is a schematic block diagram which shows an example of the conventional liquid crystal display device.

Explanation of symbols

1 louver layer 2 first adhesive layer 3 first transparent protective layer 4 adhesive layer 5 polarizing plate 6 second adhesive layer 7 second transparent protective layer 11 light transmission band 12 light shielding band

Claims (1)

A louver layer in which light transmission bands and light shielding bands are alternately arranged;
A viewing angle control body comprising a polarizing plate that selectively transmits a predetermined polarization component and absorbs and / or scatters another polarization component.

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