JP2012113054A - Optical sheet and manufacturing method of the same, image display device, and mold roll and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet capable of preventing luminance reduction at the top and bottom of a screen of a display panel and improving in-plane luminance unevenness on the assumption that a viewing angle of a viewer is set to be 0 degrees at the center of the screen of the display panel.SOLUTION: In an optical sheet, a contrast improvement layer having light transmission parts arranged in parallel along a sheet surface of the optical sheet so as to transmit light and light absorption parts arranged in parallel between the light transmission parts so as to absorb light is arranged on one surface of a base material layer, and an adhesive layer for directly or indirectly attaching the optical sheet to the display panel is arranged on the other surface side of the base material layer or the opposite side of the base material layer in the contrast improvement layer. A line segment from the center at the incident side of the light transmission parts to the center at the emission side of the light transmission parts in the contrast improvement layer is directed toward the center side of the optical sheet with respect to the normal direction of the optical sheet.

Description

  The present invention relates to an optical sheet having a plurality of layers, which is arranged on the viewer side from the display panel, and controls the light incident from the display panel side to be emitted to the viewer side, its manufacturing method, and the optical sheet In particular, the present invention relates to an optical sheet that can prevent a decrease in luminance at the top and bottom of a display panel and improve in-plane luminance unevenness, and a method for manufacturing the same.

In recent years, in a display device such as a television using a plasma display panel (hereinafter also referred to as PDP), an optical sheet is disposed on the viewer side of the PDP in order to provide a good quality image to the viewer.
In such an optical sheet, a light transmission part (also referred to as a prism part) that transmits the image light from the PDP is arranged in parallel along the sheet surface, and the image light and the external light are appropriately blocked or reflected to thereby contrast. A light absorbing portion that improves the light intensity and suppresses ghost is disposed between the light transmitting portions. (Refer to patent document 1 (Unexamined-Japanese-Patent No. 2006-189867)).

Recently, a technique called a direct attachment method in which the optical sheet is attached to a PDP directly or via a certain layer from the viewpoint of reducing the thickness of a plasma television or the like has been increasingly employed (Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-32083). 2009-031322) and cited reference 3 (Japanese Patent Laid-Open No. 2008-020878).
In the case of this direct attachment method, since it is necessary to provide an adhesive layer on the optical sheet, for example, as shown in FIG. 9A, from the PDP side (left side of the paper surface) to the observer side (right side of the paper surface) It has an adhesive layer 313 for attaching to the PDP, a light transmission part (prism part) 312a and a light absorption part 312b, and controls the blocking and reflection of image light and external light to improve contrast and suppress ghosting. An optical sheet 320 having a layer structure in which a contrast improving layer 312 and a PET film layer 311 serving as a base material are laminated in this order.
Here, the contrast enhancement layer 312 is a layer in which the light transmission part (prism part) 312a and the light absorption part 312b are arranged along the sheet surface.
With this configuration, the optical sheet 320 can be directly attached to the PDP.
Alternatively, for example, as shown in FIG. 9B, from the PDP side (left side of the paper) to the viewer side (right side of the paper), the adhesive layer 313, the PET film layer 311 as the base material, and the contrast improving layer 312 However, the optical sheet 320 </ b> A has a layer configuration that is laminated in this order.
In the optical sheet 320 shown in FIG. 9A and the optical sheet 320A shown in FIG. 9B, the stacking order of the contrast improving layer 312 and the PET film layer 311 as the base material is reversed with respect to the adhesive layer 313. It has become.

In such an optical sheet, a light transmitting portion (prism portion) 112a and a light absorbing portion 112b having an isosceles trapezoidal shape are arranged in parallel at a predetermined pitch on the entire surface of the sheet, as shown in FIG. When the contrast enhancement layer 112 is arranged,
(1) When observing in front of the screen, the top and bottom of the screen become dark.
(2) When observing the screen from above, the bottom of the screen becomes particularly dark.
(3) Since the external light angle from the ceiling is shallow on the screen, the external light is likely to enter and the bright room contrast is lowered.
(4) Since the external light angle from the ceiling is deep under the screen, the external light is difficult to enter and the bright room contrast is high.
There is a problem.
In FIG. 7, only the contrast improving layer 112 of the optical sheet layer configuration is shown for easy understanding, the display panel is on the left side of the page, and the optical sheet is arranged on the viewer side of the display panel. Has been.
In FIG. 7, 112c is a layer made of the same material as the light transmitting portion 112a, and 17d, 17e, and 17f indicate the relative light intensity distribution in each direction of the emitted light from the light transmitting portion 112a of the image light at each position. It is the figure shown (light intensity distribution map).
Further, an optical sheet 100 as shown in FIG. 8A (refer to cited document 2 (Japanese Patent Laid-Open No. 2009-031322)), or FIG. 8B (cited document 3 (Japanese Patent Laid-Open No. 2008-020878)). In the case of the optical sheet having the contrast enhancing layer 212 shown in FIG. 8B, since the top and bottom of the contrast enhancing layer (112 in FIG. 8A and 212 in FIG. 8B) are asymmetric, Even if it is turned upside down, it is difficult to distinguish the top and bottom, and there is a problem that it is difficult to manage.
U and D in FIG. 8A mean the upper part and the lower part, and in FIG. 8B, θ1 <θ2.
In addition, in the optical sheet having the contrast improving layer 212 shown in FIG. 8B (see cited document 3 (Japanese Patent Laid-Open No. 2008-020878)), the viewing angle is generally downward, and from above. There was a problem that it was dark to see.

JP 2006-189867 A JP 2009-031322 A JP 2008-020878 A

As described above, when the optical sheet is arranged as shown in FIG. 7, there is a difference in the bright room contrast between the top and bottom of the screen due to the influence of outside light (illumination light) on the ceiling, and FIG. 8 or the optical sheet having the contrast enhancement layer 212 as shown in FIG. 8B, the contrast enhancement layer (112 in FIG. 8A, 212 in FIG. 8B). Since the top and bottom of the screen is asymmetric, when the optical sheet is a single piece, it is difficult to distinguish the top and bottom even if it is flipped up and down, making it difficult to manage, and further, it has a contrast improving layer 212 shown in FIG. In the case of the optical sheet, the viewing angle is generally lowered, and there is a problem that it is dark when viewed from above, and an optical sheet having an optical functional sheet layer that can solve these problems has been demanded.
The present invention corresponds to these, and on the premise of an observer who sets the viewing angle at the center of the screen of the display panel to 0 degree, it is possible to prevent a decrease in luminance at the top and bottom of the screen of the display panel and improve in-plane luminance unevenness. We are going to provide an optical sheet.

The optical sheet of the present invention is an optical sheet having a plurality of layers, arranged on the viewer side of the display panel of the display device, and controlling the light incident from the display panel side to be emitted to the viewer side, Contrast having, on one surface of the base material layer, a light transmission part arranged in parallel along the sheet surface of the optical sheet so that light can be transmitted, and a light absorption part arranged in parallel so as to absorb light between the light transmission parts An improvement layer is disposed and the display layer is directly or indirectly on the other side of the base material layer that is not the one surface side, or on the opposite side of the contrast improvement layer from the base material layer. The direction of the line segment connecting from the center on the incident side of the light transmission part of the contrast improving layer to the center on the emission side of the light transmission part is in the normal direction of the optical sheet. On the other hand, it is suitable for the center side of the optical sheet. Is shall.
And in the above optical sheet, in the cross section in the thickness direction of the contrast improving layer, the light transmission part is a trapezoid having a long lower base on one side and a short upper base on the other side, and the light absorption part is A triangle having a base on the other side, or a trapezoid having a short upper base on the one side and a long lower base on the other side, and the contrast enhancing layer is light along the lower base of the light transmitting portion. A layer of the same material as that of the transmission part is arranged along the sheet surface.
And, in any one of the above optical sheets, the refractive index n _t and the expected angle θ of the light transmission part are:
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
It is characterized by satisfying the following formula.
The optical sheet according to any one of the above, wherein the outermost layer includes an antireflection layer or an antiglare layer.
In addition, the optical sheet according to any one of the above-described items, includes a wavelength filter layer having a function of suppressing transmission of light having a predetermined wavelength.
In addition, any one of the optical sheets described above is provided with an electromagnetic wave shielding layer having a function of shielding electromagnetic waves.

  The video display device of the present invention is characterized in that the optical sheet according to any one of claims 1 to 6 is arranged on an observer side of a plasma display panel (PDP).

  The optical sheet manufacturing method of the present invention is the optical sheet manufacturing method according to any one of claims 1 to 6, wherein the contrast improving layer is formed by (a) forming a light transmission portion. A step of preparing a mold roll of (b), (b) a step of adjusting the light transmitting portion constituting composition, (c) supplying the light transmitting portion constituting composition onto a previously prepared base material, Filling the light transmitting part constituting composition between a mold roll and a nip roll, and irradiating ultraviolet rays to cure the light transmitting part constituting composition to form a light transmitting part; and (d) the mold A step of releasing the light transmitting portion from the mold roll, and the mold roll cuts a groove continuous in the circumferential direction of the mold roll or in an oblique direction with respect to the circumference with a cutting tool. And a plurality of grooves formed in the width direction, and each groove is a width direction of the mold roll. The center is characterized in that it is formed by increasing the angle of tilting toward the center of the groove in accordance with the angle of tilting toward the center of the groove is 0, leaving the width direction, from the center.

A mold roll of the present invention is a mold roll for forming a light transmission part of a contrast improving layer of an optical sheet according to any one of claims 1 to 6, wherein the mold roll is in a circumferential direction. Alternatively, a plurality of continuous grooves in the oblique direction with respect to the circumference are cut with a cutting tool and formed in the width direction, and each groove is inclined toward the center of the groove at the center in the width direction of the mold roll. It is characterized in that the angle is set to 0 and the angle to be inclined toward the center of the groove is increased as the distance from the center is increased.
The mold roll manufacturing method of the present invention is the mold roll manufacturing method according to claim 9, wherein the angle of tilting the cutting tool toward the center side in the width direction of the mold roll is set for each feed of each tool. Control to cut from one end in the width direction of the mold roll to the other end through the center, and at the center of the mold width direction the angle tilted toward the center is 0, The cutting is performed by increasing the angle of inclination toward the center as the distance from the center of the mold increases.

Alternatively, a mold roll of the present invention is a mold roll for forming a light transmission part of a contrast improving layer of an optical sheet according to any one of claims 1 to 6, wherein the mold roll is a circle of the mold roll. Grooves that are continuous in the circumferential direction or in an oblique direction with respect to the circumference are cut with a cutting tool to form a plurality of grooves in the width direction. Each groove is at the center of the groove in the width direction center of the mold roll. It is characterized in that the angle of inclination is 0, and the angle of inclination to the opposite side of the center of the groove is increased as the distance from the center is increased.
Alternatively, the mold roll manufacturing method according to the present invention is a mold roll manufacturing method according to claim 11, wherein the angle at which the cutting tool is inclined toward the center side in the width direction of the mold roll is set for each feed of each cutting tool. In this way, cutting is performed from one end in the width direction of the mold roll to the other end through the center, and at the center in the width direction of the mold, the angle inclined toward the center is set to 0. The cutting is performed by increasing the angle inclined to the side opposite to the center as the distance from the center in the mold width direction increases.

(Function)
The optical sheet of the present invention has such a configuration, and on the premise of an observer whose viewing angle at the center of the screen of the display panel is 0 degree, prevents a decrease in luminance at the top and bottom of the screen of the display panel. It is possible to provide an optical sheet that can improve luminance unevenness.
Specifically, on one surface of the base material layer, a light transmission part arranged in parallel along the sheet surface of the optical sheet so that light can be transmitted and a light absorption system arranged in parallel so that light can be absorbed between the light transmission parts And a contrast improving layer having a portion, and directly or indirectly on the other side of the base material layer that is not the one surface side, or on the opposite side of the contrast improving layer from the base material layer. In addition, an adhesive layer for attaching to the display panel is arranged, and the direction of the line segment connecting from the center on the incident side of the light transmission portion of the contrast improving layer to the center on the emission side of the light transmission portion is an optical sheet. More specifically, the refractive index n _t and the expected angle θ of the light transmissive part are as follows.
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
This is achieved by satisfying the relationship of
As a specific shape, in the cross section in the thickness direction of the contrast improving layer, the light transmission part is a trapezoid having a long lower base on one side and a short upper base on the other side, A triangle having a base on the other side, or a trapezoid having a short upper base on one side and a long lower base on the other side, and the contrast enhancing layer transmits light along the lower base of the light transmitting portion. The form which has arrange | positioned the layer of the same material as a part along a sheet | seat surface is mentioned.
Specifically, in the optical sheet of the present invention, the light transmission portion corresponding to a position away from the center of the screen is formed by the above configuration on the assumption that the viewing angle at the center of the screen of the display panel is 0 degree. By adjusting the light intensity distribution (see ellipses 17a and 17c in FIG. 1) toward the viewer side, the luminance distribution on the entire screen can be reduced in variation.
In the present invention, since the viewing angle is centered at the top and bottom of the screen, the top and bottom of the screen are not dark when viewed from the front of the screen.
Further, according to the present invention, the external light absorbability on the screen is further increased, and a decrease in bright room contrast can be prevented.
Further, in the present invention, the external light absorption under the screen is lowered, but the in-plane uniformity is rather increased.

The refractive index nt and the expected angle θ of the light transmission part are
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
By satisfying the relationship of
The effect of absorbing external light is reduced, the bright room contrast is prevented from being lowered, and the viewing angle for the PDP can be secured.
When the above equation is attached to the PDP, as shown in FIG. 1 (b), the normal direction connecting the incident side of the lower light absorption unit of one light transmission unit to the emission side of the upper light absorption unit is shown. Assuming that the angle is a prospective angle θ, the viewing angle emitted into the air is calculated as asin (n _t × sin θ) from the refractive index of the light transmitting portion with respect to θ in the medium (light transmitting portion). It means that the viewing angle when it is emitted inside is preferably in the range of 30 ° to 60 °.
In general, the viewing angle characteristic is as shown in FIG. 6, and the transmittance decreases as the angle increases from 0 ° in the front where the transmittance is high. In the example of FIG. 6, there is an inflection point in the vicinity of 40 ° to 50 °. Although it is almost constant at higher angles, the value of asin (n _t × sin θ) corresponds to the inflection point of 40 ° to 50 °.
Therefore, if the inflection point angle asin (n _t × sin θ) is less than 30 °, the viewing angle is too narrow and unsuitable for television use. Conversely, if it exceeds 60 °, the viewing angle is wide. Since the light absorption effect is reduced, there is a problem that the bright room contrast is lowered and the effect of providing the optical function layer is lost, and asin (n _t × sin θ) is defined as in the above equation.

Moreover, the form of invention of Claim 4 provided with the antireflection layer or the glare-proof layer in the outermost layer is mentioned.
When the antireflection layer is provided, it is possible to suppress external light from being reflected on the viewer side surface of the optical sheet and returning to the viewer side, so-called reflection is generated, and the image is difficult to see.
When the antiglare layer is provided, so-called glare can be suppressed.
The antiglare layer is sometimes called an antiglare layer or an AG layer.

Moreover, the form of invention of Claim 5 provided with the wavelength filter layer which has the function to suppress transmission of the light of a predetermined wavelength is mentioned.
The wavelength filter layer is a layer having a function of filtering light of a predetermined wavelength. By adopting this form, it is possible to filter light of a predetermined wavelength.
The wavelength to be filtered can be appropriately selected according to need. Usually, a layer that cuts neon lines emitted from the image light source or cuts infrared rays, near infrared rays, and ultraviolet rays is used.
In addition, it can be combined with other functional layers such as an adhesive layer.

Moreover, the form of invention of Claim 6 provided with the electromagnetic wave shielding layer which has the function to shield electromagnetic waves is mentioned.
As the name indicates, the electromagnetic wave shielding layer is a layer having a function of shielding electromagnetic waves, and is not particularly limited as long as it has the function, and examples thereof include a copper mesh.
The pitch of the copper mesh is appropriately designed according to the electromagnetic wave to be blocked, the required transmittance, and the state of occurrence of moire, and examples thereof include a pitch of about 300 μm and a line width of 12 μm.

  The video display device of the present invention is configured in such a manner so that the top and bottom of the screen of the plasma display panel (PDP) is premised on an observer who assumes a viewing angle of 0 degrees at the center of the screen of the plasma display panel (PDP). It is possible to prevent a decrease in luminance and improve in-plane luminance unevenness.

The optical sheet manufacturing method of the present invention has such a configuration, and prevents a decrease in luminance at the top and bottom of the screen of the display panel on the premise of an observer who sets the viewing angle at the center of the screen of the display panel to 0 degrees. Therefore, it is possible to provide an optical sheet that can improve in-plane luminance unevenness.
In addition, the mold roll of the present invention has such a configuration to prevent a decrease in luminance at the top and bottom of the screen of the display panel on the premise of an observer who sets the viewing angle at the center of the screen of the display panel to 0 degrees. This enables mass production of the contrast enhancement layer of the optical sheet that can improve the in-plane luminance unevenness.

  As described above, the present invention is based on the assumption that the viewer has a viewing angle of 0 degrees at the center of the screen of the display panel. It is possible to provide a method for manufacturing the optical sheet.

FIG. 1A is a schematic cross-sectional view showing a first example of an embodiment of the optical sheet of the present invention and its usage, and FIG. 1B shows an optical sheet of the first example as an observer of a display panel. It is the schematic which showed the observer's observation state in the case of arranging on the side. FIG. 2A is a schematic diagram for explaining a cutting method of a cutting tool when forming a mold in a mold roll used when forming a light transmitting portion of the contrast improving layer of the optical sheet of the first example. 2 (b) is a view showing each cutting position (A, B, C) shown in FIG. 2 (a) by a position on a die roll. FIG. 3A to FIG. 3E are schematic cross-sectional views showing second to sixth examples of optical sheet embodiments of the present invention and usage patterns thereof, respectively. FIG. 4A is a schematic process diagram showing the formation of a light transmission part using a mold roll, and FIG. 4B is a process of filling the groove between the light transmission parts with the light absorbing part constituent composition. It is the shown schematic. FIG. 5A and FIG. 5B are diagrams showing a mold roll, respectively. It is a figure for demonstrating the relationship between a viewing angle and the transmittance | permeability of image light. FIG. 7 is a schematic view showing an observer's observation state when a conventional optical sheet is arranged on the observer side of the display panel. FIG. 8A is a schematic sectional view showing a conventional optical sheet, and FIG. 8B is a schematic sectional view showing a conventional contrast improving layer. FIG. 9A and FIG. 9B are schematic cross-sectional views showing a conventional optical sheet.

First, the 1st example of embodiment of the optical sheet of this invention is demonstrated based on FIG.
The optical sheet of the first example is disposed on the observer side of a PDP (plasma display panel) 20 and controls the light incident from the PDP side to emit the optical sheet 10 to the observer side. In this case, as shown in FIG. 1A, the PDP 20 is attached to the PDP 20 with an adhesive layer 13 and used.
The first example optical sheet includes, in order from the pressure-sensitive adhesive layer 13 side, a base material layer 11 serving as a base material, a light transmission portion arranged in parallel along the sheet surface of the optical sheet so that light can be transmitted, and the light transmission portion It has a structure in which a contrast enhancement layer 12, a functional layer 14, and a functional layer 15 (antireflection layer or antiglare layer) having a light absorbing portion arranged in parallel so as to be able to absorb light are laminated. It is attached directly to the PDP.
As the functional layer 15, either one of an antireflection layer or an antiglare layer is provided.
As the functional layer 14, one or more layers of a wavelength filter layer and an electromagnetic wave shielding layer are disposed.
In the optical sheet of this example, the direction of the line segment connecting from the center of the light transmission side 12a of the light transmission part 12a of the contrast improving layer 12 to the center of the light transmission part of the light transmission side of the image light is determined by the method of the optical sheet. It faces the center side of the optical sheet with respect to the line direction.
In this example, in particular, the position corresponding to the center of the screen of the PDP 20 is defined as the center of the optical sheet 10, and the above-described line segment with respect to the normal direction of the optical sheet is increased from the center of the optical sheet 10 in the vertical direction of the screen. The size of the angle gradually increases.
Here, the normal direction of the sheet surface at the center of the optical sheet is the normal direction of the optical sheet, and similarly, the normal direction of the sheet surface at the center of the contrast enhancement layer 12 is the normal direction of the contrast enhancement layer. .
In the first example, the refractive index n _t and the expected angle θ of the light transmitting portion 12a are
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
The relationship is satisfied.
In FIG. 1 (b), only the contrast improving layer 12 of the layer configuration of the optical sheet 10 shown in FIG. 1 (a) is shown for easy understanding, as shown in FIG. 1 (a). In addition, the PDP panel 20 is on the left side in FIG. 1B, and the optical sheet 10 is disposed on the observer side of the PDP panel 20.
In FIG. 1B, 12a, 12b, and 12c are layers made of the same material as the light transmitting portion, the light absorbing portion, and the light transmitting portion 12a, respectively, and the layer 12c and the light transmitting portion made of the same material as the light transmitting portion. 12a is continuous and the boundary between the two is not actually seen, but here, for convenience, the boundary between the two is indicated by a dotted line.
Also, in FIG. 1B, 17a, 17b, and 17c are diagrams that relatively show the light intensity distribution in each direction of the emitted light from the light transmitting portion 12a of the image light at each position (light intensity distribution diagram). It is.

In this example, as shown in FIG. 1B, in the cross section in the thickness direction of the contrast improving layer 12, the light transmitting portion 12 a has a long bottom on one side that is the incident side of the image light, and the other on the emission side of the image light. The light-absorbing portion 12b is a trapezoid having a short upper base on the one side and a long lower base on the other side.
Note that the trapezoid referred to here does not have to be a strict trapezoid and means a substantially trapezoidal shape.
And the contrast improvement layer 12 distribute | arranges the layer 12c of the same material as the light transmissive part along the sheet | seat surface along the lower bottom of the light transmissive part 12a.
The lower bottom of the light absorbing portion 12b and the upper bottom of the light transmitting portion 12a are arranged on one plane, the upper bottom of the light absorbing portion 12b and the lower bottom of the light transmitting portion 12a are arranged on one plane, One surface is formed on the other side of the contrast improving layer 12 by the lower bottom of the light absorbing portion 12b and the upper bottom of the light transmitting portion 12a.
The trapezoidal shape of the cross section of the light absorbing portion 12b does not need to be a strict trapezoid, and the inclination of the hypotenuse does not necessarily have to be constant, and may be a polygonal line or a curved line. The angle of the hypotenuse in the trapezoid of the cross section of the absorber 12b is preferably 0 ° or more and 10 ° or less with respect to the normal direction of the sheet surface of the contrast improving layer 12.

The optical sheet of the first example has such a configuration, and therefore, on the premise of an observer who has a viewing angle of 0 degrees at the center of the display panel, it prevents brightness reduction at the top and bottom of the screen of the display panel. It is possible to provide an optical sheet that can improve unevenness.
In the optical sheet of the first example, on the assumption that the viewing angle at the center of the screen of the display panel is 0 degree, the above configuration allows the light transmitting portion corresponding to a position away from the center of the screen to be configured. By adjusting the light intensity distribution (see 17a and 17c in FIG. 1) toward the viewer side, the luminance distribution on the entire screen can be reduced.
In the first example, since the viewing angle is centered at the top and bottom of the screen, when observing from the front of the screen, the top and bottom of the screen do not become darker, the external light absorption on the screen becomes higher, and the bright room contrast decreases. Can be prevented.
In the first example, the external light absorption under the screen decreases, but the in-plane uniformity increases.

In the optical sheet of the first example, the refractive index n _t and the expected angle θ of the light transmission part 12a are:
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
By adopting a configuration satisfying the following equation, it is possible to prevent the bright room contrast from being lowered and to secure a viewing angle for PDP.

In the optical sheet of the first example, in the formation of the light transmission portion of the contrast enhancement layer using a mold roll, the transmittance of the image light is reduced while ensuring the release of the light transmission portion from the mold. Therefore, the direction connecting the center on the incident side and the center on the output side of the light absorbing portion 12a is not less than 0 degrees and not more than 10 degrees with respect to the normal direction of the optical sheet. (See Fig. 4 (a))
In general, in the case of a vertically symmetric shape, when the angle of inclination of the light absorbing portion exceeds 5 degrees on one side, there is a problem that the image light absorbed by the light absorbing portion increases and the transmittance of the image light decreases.
In order to achieve the above-mentioned effects effectively, it is assumed that the angle of the light absorption part is changed at least at the top and bottom of the screen, but the slope angle is 5 degrees on one side at the top and bottom of the screen, and the slope angle of the light absorption part is minimum. If the angle of the light absorbing part is changed up and down within the range of 0 degrees, the top on the screen is -10 degrees, the bottom is 0 degrees, the top of the screen is -5 degrees, the bottom is 5 degrees, and the top bottom of the screen is 0 degrees and 10 degrees below.
Accordingly, the direction connecting the center on the incident side and the center on the emission side of the light absorbing portion is set to 0 degree or more and 10 degrees or less with respect to the normal direction of the optical sheet.
More preferably, 2 degrees on one side is desirable, and at this time, the direction connecting the center of the light absorbing part on the incident side and the center of the light exit side is 0 degree or more and 4 degrees or less with respect to the normal direction of the optical sheet.

When an antireflection layer is provided as the outermost functional layer 15, the external light is reflected on the viewer side of the optical sheet and returns to the viewer side, so that the so-called reflection occurs and the image becomes difficult to see. Can be suppressed.
When an antiglare layer is provided as the outermost functional layer 15, so-called glare can be suppressed. The antiglare layer is sometimes called an antiglare layer or an AG layer.

When the functional layer 14 includes a wavelength filter layer that is a layer having a function of filtering light having a predetermined wavelength, transmission of light having the predetermined wavelength can be suppressed.
The wavelength to be filtered can be appropriately selected as necessary, and examples thereof include a layer that cuts a neon line emitted from an image light source or cuts infrared rays, near infrared rays, and ultraviolet rays.
It can be combined with other functional layers such as an adhesive layer.
When an electromagnetic wave shielding layer is provided as the functional layer 14, the electromagnetic wave can be blocked.
In addition, an electromagnetic wave shielding layer is a layer which has the function which interrupts | blocks an electromagnetic wave as the name shows. As long as the layer has the function, a means for blocking electromagnetic waves is not particularly limited. This can include, for example, a copper mesh.
As a method for obtaining the copper mesh, it is effective to form a fine copper mesh pattern by etching, vapor deposition or the like.
The pitch of the copper mesh is appropriately designed according to the electromagnetic wave to be blocked, the required transmittance, and the state of occurrence of moire, and examples thereof include a pitch of about 300 μm and a line width of 12 μm.

The base material layer 11 is a layer as a base material for forming a contrast enhancement layer described in detail later.
The base material layer 11 is preferably composed of a material mainly composed of polyethylene terephthalate (PET).
When the base material layer 11 has PET as a main component, the base material layer 11 may contain other resins.
Various additives may be added as appropriate.
Examples of general additives include phenol-based antioxidants, lactone-based stabilizers, and the like.
Here, “main component” means that the PET is contained in an amount of 50% by mass or more with respect to the entire material forming the base material layer (hereinafter the same).
However, the main component of the material constituting the base material layer 11 is not necessarily PET, and other materials may be used.
Examples thereof include polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, polyester resins such as terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer, and polyamide resins such as nylon 6. , Polyolefin resins such as polypropylene and polymethylpentene, acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and styrene-acrylonitrile copolymer, cellulose resins such as triacetyl cellulose, imide resins and polycarbonate resins Etc.
Moreover, you may add additives, such as a ultraviolet absorber, a filler, a plasticizer, an antistatic agent, in these resins suitably as needed.
In addition to performance, from the viewpoints of mass productivity, price, availability, etc., it is preferable that the base material layer 11 is composed of a resin mainly composed of PET.

Next, the contrast improving layer 12 will be described.
The contrast improving layer 12 is arranged in parallel at a predetermined interval along the sheet surface and is formed so as to be able to absorb light between the light transmitting portion 12a formed so as to be able to transmit light and the adjacent light transmitting portion 12a. And an absorbing portion 12b.
The contrast enhancement layer 12 is a layer that controls the optical path of the image light from the image light source side and has a function of appropriately absorbing stray light and external light.
For example, as shown in FIG. 4A, the light transmitting portion 12a is formed in a state where a composition for forming a light transmitting portion (hereinafter referred to as a light transmitting portion composition) is applied on a base material 51. The material 51 is transported and inserted between the mold roll 60 and the nip roll 62, the light transmitting portion constituting composition 52 is pressed between the mold roll 60 and the nip roll 62, and the ultraviolet rays 53 are applied to the light transmitting portion constituting composition 52. Irradiation is performed to cure the light transmitting portion constituting composition 52, and the light transmitting portion 12 a is formed on the base material 51.
As the mold roll 60, grooves 61a are cut with a cutting tool (not shown) in the circumferential direction of the mold roll 61 as shown in FIG. 5A, or as shown in FIG. 5B. As described above, a plurality of grooves 61aA continuous in the oblique direction with respect to the circumference of the mold roll 61A are cut with a cutting tool (not shown) and formed in the width direction.
In the mold roll (61, 61A) for forming the light transmission part of the contrast improving layer 12 of the optical sheet 10 of this example, as shown in FIG. With respect to the normal line direction, cutting is performed obliquely in the center direction in the width direction of the mold roll.
That is, each cut groove is formed by setting the angle to be inclined toward the center of the groove at the center of the mold roll in the width direction to 0 and increasing the angle to be inclined toward the center of the groove as the distance from the center is increased. ing.
2B, the cross sections in the regions A, B, and C of FIG. 2B show the cross sections of A, B, and C in FIG. Shows direction. In FIG. 2A, only one cutting tool is actually used, but a plurality of cutting tools are shown for the sake of convenience so that the cutting position of the cutting tool can be understood.
For example, as shown in FIG. 4 (b), the light absorbing portion 12b is formed by a composition for forming a light absorbing portion (hereinafter referred to as a light absorbing portion) containing light absorbing particles and a binder in which the light absorbing particles are dispersed. 70) (referred to as a constituent composition) is scraped and filled with a doctor blade 75 into a groove 54b between adjacent light transmitting portions of the light transmitting portion 54a (corresponding to 12a) formed as described above, and cured. Forming.
When scraping, the use of colored particles having an average particle diameter of 1.0 μm or more makes it difficult for the colored particles to pass through the gap between the doctor blade 75 and the light transmitting part 12a. It is possible to prevent the colored particles from remaining.

The light absorbing portion 12b is made of a predetermined material having a refractive index Nb smaller than the refractive index Np of the light transmitting portion 12a.
Thus, by setting the refractive index Np of the light transmission part 12b and the refractive index Nb of the light absorption part 12a to Np> Nb, the image light from the light source incident on the light transmission part 12a is converted into the light absorption part 12b and the light. Reflection can be performed by Snell's law at the interface with the transmission part 12a, and a bright image can be provided to the observer.
The difference in refractive index between Np and Nb is not particularly limited, but is preferably 0 or more and 0.06 or less.

As the light transmitting part constituting composition, for example, a photocurable resin composition in which a reactive dilution monomer (M1) and a photopolymerization initiator (S1) are blended with a photocurable prepolymer (P1) is preferably used.
Examples of the photocurable prepolymer (P1) include epoxy acrylate-based, urethane acrylate-based, polyether acrylate-based, polyester acrylate-based, and polythiol-based prepolymers.
Examples of the reactive dilution monomer (M1) include vinyl pyrrolidone, 2-ethylhexyl acrylate, β-hydroxy acrylate, and tetrahydrofurfuryl acrylate.
Examples of the photopolymerization initiator (S1) include hydroxybenzoyl compounds (2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, benzoin alkyl ether, etc.), benzoyl Formate compounds (such as methylbenzoylformate), thioxanthone compounds (such as isopropylthioxanthone), benzophenones (such as benzophenone), phosphate compounds (1,3,5-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-) Trimethylbenzoyl) -phenylphosphine oxide and the like, and benzyldimethyl ketal and the like. Among these, the irradiation device for curing the photocurable resin composition and the curability of the photocurable resin composition can be arbitrarily selected.
From the viewpoint of preventing coloring of the light transmitting portion 12a, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone and bis (2,4,6-trimethylbenzoyl) are preferable. ) -Phenylphosphine oxide.

In this example, the amount of the photopolymerization initiator (S1) contained in the photocurable resin composition is based on the total amount of the photocurable resin composition from the viewpoint of curability and cost of the photocurable resin composition (100 mass). %) Is preferably 0.5% by mass or more and 5.0% by mass or less.
The photopolymerization initiator (S1) may be colored (for example, colored yellow), provided that it is substantially colorless when the light transmitting part is cured to form the light transmitting part. And
These photocurable prepolymer (P1), reactive diluent monomer (M1) and photopolymerization initiator (S1) can be used alone or in combination of two or more.
In addition, in the light transmitting part constituting composition, if necessary, silicone additives, rheology control agents, It is also possible to add a defoaming agent, a release agent, an antistatic agent, an ultraviolet absorber, and the like.

Although what is used as a binder of the light absorption part composition 70 is not specifically limited, For example, a reactive dilution monomer (M2) and a photoinitiator (S2) are added to a photocurable prepolymer (P2). A blended photocurable resin composition is preferably used.
Examples of the photocurable prepolymer (P2) include urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate.
Examples of the reactive dilution monomer (M2) include monofunctional monomers such as N-vinyl pyrrolidone, N-vinyl caprolactone, vinyl imidazole, vinyl pyridine, styrene, and other vinyl monomers, lauryl (meth) acrylate, stearyl ( (Meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, paracumylphenoxyethyl (meth) ) Acrylate, nonylphenoxy polyethylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) a (Meth) acrylic acid ester monomers such as relate, cyclohexyl (meth) acrylate, benzyl methacrylate, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylate, acryloylmorpholine, A (meth) acrylamide derivative is mentioned. Polyfunctional monomers include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polytetra Methylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 3-methyl-1, 5-pentanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate Bisphenol A polypropoxydiol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) Acrylate, glyceryl tri (meth) acrylate, propoxylated glyceryl tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate And dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.
Examples of the photopolymerization initiator (S2) include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethane- Examples include 1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide.
Among these, the irradiation device for curing the photocurable resin composition and the curability of the photocurable resin composition can be arbitrarily selected.
In this example, the amount of the photopolymerization initiator (S2) contained in the photocurable resin composition is based on the total amount of the photocurable resin composition from the viewpoint of curability and cost of the photocurable resin composition (100 mass). %) Is preferably included in an amount of 0.5% by mass or more and 10.0% by mass or less.
These photocurable prepolymer (P2), reactive diluent monomer (M2) and photopolymerization initiator (S2) can be used alone or in combination of two or more.
Specifically, a photopolymerizable component composed of urethane acrylate, epoxy acrylate, tripropylene glycol diacrylate and methoxytriethylene glycol acrylate (specifically, photocurable prepolymer (P2) and reactive dilution monomer (M2)). In consideration of the refractive index, the viscosity, the influence on the performance of the optical function sheet 10, etc., they are arbitrarily mixed and used.

  Moreover, you may add a silicone, an antifoamer, a leveling agent, a solvent, etc. to a light absorption part structure composition as an additive as needed.

The light-absorbing particles are contained in the light-absorbing part constituting composition, and act to absorb stray light and external light when the light-absorbing part is configured.
As the light-absorbing particles, light-absorbing colored particles such as carbon black are preferably used, but the light-absorbing particles are not limited to these, and colored particles that selectively absorb a specific wavelength according to the characteristics of the image light. May be used.
Specific examples include organic fine particles colored with metal salts such as carbon black, graphite, and black iron oxide, dyes, pigments, colored glass beads, and the like.
In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality, availability, and the like.
More specifically, acrylic cross-linked fine particles containing carbon black, urethane cross-linked fine particles containing carbon black, and the like are preferably used.
Such colored particles are usually contained in the light absorbing part constituting composition in a range of 3% by mass to 30% by mass.
The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less.
When forming the light absorbing portion, as shown in FIG. 4B (a diagram schematically showing a method of manufacturing the light absorbing portion), the light absorbing portion constituting composition 35 containing the colored particles is light-transmitted. The process which scrapes off the excess light absorption part structure composition 35 using the doctor blade 36, filling the groove | channel between parts 12, 12, ... is included.

Next, a second example and a third example of the embodiment of the optical sheet of the present invention will be described based on FIG. 3 (a) and FIG. 3 (b), respectively.
First, a second example will be described.
Similarly to the first example, the second example includes a plurality of layers that are arranged on the observer side of the PDP (plasma display panel) 20 and control the light incident from the PDP side to be emitted to the observer side. An optical sheet 10 </ b> A having an adhesive layer 13 attached to the PDP 20 as shown in FIG.
As the functional layer 15, either one of an antireflection layer or an antiglare layer is provided.
As the functional layer 14, one or more layers of a wavelength filter layer and an electromagnetic wave shielding layer are disposed.
Each part (each layer) in the second example is exactly the same as each corresponding layer in the first example, but in order from the adhesive layer 13 side, the functional layer 14, the base material layer 11, the contrast improving layer 12, and the functional layer. 15 and is directly attached to the PDP by the pressure-sensitive adhesive layer 13.
In the case of the second example as well, basically as in the first example, on the premise of an observer who sets the viewing angle at the center of the screen of the display panel to 0 degrees, a decrease in luminance at the top and bottom of the screen of the display panel is prevented. It is possible to provide an optical sheet that can improve in-plane luminance unevenness.
Also in this example, the viewing angle is centered at the top and bottom of the screen, so when observing in front of the screen, the top and bottom of the screen will not become darker, and the external light absorption on the screen will be higher, preventing a decrease in bright room contrast. it can.
In addition, the external light absorptivity under the screen is lowered, but the in-plane uniformity is rather increased.
Each part is the same as in the first example, and a description thereof is omitted here.
Next, a third example will be described.
Similarly to the first example and the second example, the third example is also arranged on the observer side of the PDP (plasma display panel) 20, and controls the light incident from the PDP side to be emitted to the observer side. The optical sheet has a plurality of layers, and is used by being attached to the PDP 20 with an adhesive layer 13 as shown in FIG.
Each part (each layer) in the third example is exactly the same as each corresponding layer in the first example, but in order from the pressure-sensitive adhesive layer 13 side, the functional layer 14a, the base material layer 11, the contrast improving layer 12, and the functional layer. 14b and the functional layer 15 are laminated.
Here, an electromagnetic shielding layer is disposed as the functional layer 14a, and a wavelength filter layer is disposed as the functional layer 14b.
As the functional layer 15, either one of an antireflection layer or an antiglare layer is provided.
In the case of the third example, basically, as in the first example and the second example, the brightness of the upper and lower sides of the screen of the display panel is assumed on the premise of an observer who sets the viewing angle at the center of the display panel to 0 degrees. It is possible to provide an optical sheet that can prevent the decrease and improve the in-plane luminance unevenness.

Next, the fourth to sixth examples will be briefly described.
Similarly to the first to third examples, the fourth to sixth examples are arranged on the viewer side of the PDP (plasma display panel) 20 and control the light incident from the PDP side to perform the observation. An optical sheet having a plurality of layers that is emitted to the user side, and is used by being attached to the PDP 20 by the adhesive layer 13.
The fourth to sixth examples are the same as the first to third examples, in which a contrast improving layer 12A is provided instead of the contrast improving layer 12, and the contrast improving layer 12A and the base are arranged from the PDP side. The material layer 11 is the same as the first example, but from the center of the light transmitting portion 12a of the contrast improving layer 12A on the image light incident side to the center of the light transmitting portion on the image light emitting side. The direction of the line connected to the optical sheet is directed toward the center side of the optical sheet with respect to the normal direction of the optical sheet, and with respect to the normal direction of the optical sheet as it moves away from the center of the optical sheet in the vertical direction of the screen. The angle of the line segment is gradually increased.
In the contrast improving layer 12 and the contrast improving layer 12A, the directions of the trapezoidal upper and lower bases in the cross section of the light transmitting portion 12a are reversed from the adhesive layer 13 side.
As described above, in the mold rolls (61 and 61A in FIG. 5) for forming the light transmission portion of the contrast improving layer 12 of the optical sheets of the first to third examples, As shown in FIG. 2 (a), the cutting tool 35 is cut obliquely with respect to the normal direction of the mold roll 30 in the center direction in the width direction of the mold roll. In the mold roll forming the light transmission part of the contrast improving layer 12A of the optical sheet 6, the bite 35 is set to 0 degree as the center part, and as it moves away from the center, with respect to the normal direction of the mold roll 30, The die roll is cut obliquely at a large angle in a direction opposite to the center in the width direction of the mold roll.
In other words, the angle of tilting each groove cut toward the center of the groove in the width direction center of the die roll is 0, and the angle tilted toward the opposite side of the groove is increased as the distance from the center in the width direction increases. Is formed.
Of course, the directions of the trapezoidal upper and lower bases in the cross section of the light absorbing portion 12b are in reverse order when viewed from the adhesive layer 13 side.
In the case of the fourth example to the sixth example, basically, as in the first example to the third example, the display panel is assumed on the premise of an observer whose viewing angle at the center of the screen of the display panel is 0 degree. Thus, it is possible to provide an optical sheet that can prevent the brightness drop at the top and bottom of the screen and improve the in-plane brightness unevenness.

The form of the present invention is not limited to the first to sixth examples.
For example, in the first example, there is also a mode (seventh example) including the adhesive layer 13, the base material layer 11, and the contrast improving layer 12 from the PDP side without the functional layer 14 and the functional layer 15. .
Further, in the fourth example, there is also an embodiment (the eighth example) which is composed of the adhesive layer 13, the contrast improving layer 12A, and the base material layer 11 from the PDP side without the functional layer 14 and the functional layer 15. .
In each example, the direction of the line segment connecting from the center of the light transmitting portion 12a of the contrast improving layer 12 to the center of the image light incident side to the center of the light transmitting portion of the image light emitting side is limited to the upper and lower regions. However, even if the structure is oriented toward the center side of the optical sheet with respect to the normal direction of the optical sheet, as in the first example, it is assumed that the viewer has a viewing angle of 0 degrees at the center of the screen of the display panel. In addition, it is possible to provide an optical sheet that can prevent a decrease in luminance at the top and bottom of the display panel and improve in-plane luminance unevenness.
Also, there are various aspects of the angle change that gradually increases the angle of the line segment with respect to the normal direction of the optical sheet. However, at least basically, the luminance is improved in the upper and lower regions. If it is possible, there is no particular limitation.
Moreover, in each example, the cross-sectional shape of the light absorption part 12b is not restricted to a trapezoid, and the form made into a triangle is also mentioned.
In the above embodiment example, the optical sheet is directly attached to the PDP with an adhesive layer. However, the optical sheet of the above embodiment example is arranged on the viewer side of the PDP through the glass layer. Examples of usage forms are also included.
Moreover, you may further add another functional layer to the optical sheet of the said embodiment example as needed.

Further, as an example, an example in which the contrast improving layer 12 used in the optical sheets of the first to third examples is formed on the base material layer 11 and the optical sheet of the seventh example is manufactured. This will be described below.
Example 1
(1) Production of mold roll A mold roll used for production of the contrast enhancement layer was produced as follows.
With respect to a cylindrical roll having copper plated on the roll surface, the copper plated portion on the surface was cut with a cutting tool to form a groove for forming a light transmitting portion, thereby producing a mold roll.
As a cutting tool, a diamond cutting tool was used, and as shown in FIG. 2 (a), the cutting angle was changed to change the groove shape to be cut by the die roll.
The tip width is 35 μm, the slope angle is 1.9 degrees, and the width when the depth is 85 μm is 41 μm.
The cutting method is as follows: the start of cutting is inclined with respect to the normal direction of the die roll by tilting the tip side of the 1.9 degree tool toward the center of the roll, the cutting center is 0 degree, and the cutting end is 1.9 degree tool. Cutting was performed by continuously changing the incident angle of the cutting tool so that the tip end side of the tool was inclined toward the center side of the roll.
Using such a diamond tool, the groove pitch in the roll axis direction was 45 μm, and the outer periphery of the copper plating layer of the mold roll was cut to form a groove.
Thus, a trapezoidal shape having a depth of 85 μm, a groove bottom width of 35 μm, and a groove width on the mold surface side of 41 μm was formed.
Thus, the groove | channel which continued in the circumferential direction of the metal mold | die roll, or the diagonal direction with respect to the circumference was cut with the cutting tool, and multiple pieces were formed in the width direction, and each groove | channel is metal A mold roll was formed in which the angle inclined toward the center of the groove was set to 0 at the center in the width direction of the mold roll, and the angle inclined toward the center of the groove was increased as the distance from the center was increased.
The cut roll was chrome plated.
(2) Adjustment of light transmission part composition 40.0 parts by mass of bisphenol A-ethylene oxide 2 mol adduct, 15.0 parts by mass of isophorone diisocyanate, bismuth tri (2-ethylhexanoate, 2 -0.02 mass part of ethyl hexanoic acid 50 mass% solution) was mixed, and it was made to react at 80 degreeC for 5 hours. Thereafter, 5.0 parts by mass of 2-hydroxyethyl acrylate was added and reacted at 80 ° C. for 5 hours to obtain a photocurable prepolymer (P1).
Next, 60.0 parts by mass of the photocurable prepolymer (P1), 15.0 parts by mass of phenoxyethyl acrylate (molecular weight 192) as the reactive diluent monomer (M1), and 4 mol of bisphenol A-ethylene oxide were added. Phosphate ester (monoester / diester = molar ratio 1/1) to which 25.0 parts by mass of the diacrylate (molecular weight 512) and 10 mol of tetradecanol-ethylene oxide as the mold release agent (S1) were added 0.05 parts by mass, and 15 parts adduct of stearylamine-ethylene oxide with 0.05 parts by mass, 1-hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184, Ciba Specialty) as a photopolymerization initiator (I1) Chemicals Co., Ltd.) is mixed with 3 parts by mass, and homogenized to form a light transmission part A composition was obtained. In addition, this light transmission part constituent composition was applied with a thickness of 100 μm, and the light transmission part constituent composition was cured by irradiating with an ultraviolet ray of 800 mJ / cm 2 with a high pressure mercury lamp, and a multi-wavelength Abbe refractometer DR-M4 (stock) The refractive index of 589 nm was measured using a product of Atago Co., Ltd. and found to be 1.550.
(3) Preparation of base material layer As the base material layer 11, PET film, brand name: A4300, the Toyobo Co., Ltd. make and 100 micrometers in thickness were prepared.
(4) Formation of light transmission part The base material produced by said (3) was inserted and conveyed between the mold roll produced by said (1), and the nip roll.
In accordance with the conveyance of the base material, the light transmission part constituting composition obtained in (2) above is supplied from the supply device onto the base material layer of the base material, and the base material is pressed by the pressing force between the mold roll and the nip roll. The light transmitting portion constituting composition was filled between the layer and the mold roll.
Then, 800 mJ / cm <2> of ultraviolet rays were irradiated from the base material side with the high pressure mercury lamp, the light transmissive part composition was hardened, and the light transmissive part was formed.
Then, the light transmission part was released from the mold roll with a peeling roll, and a sheet (intermediate member) having a thickness including the light transmission part of 205 ± 20 μm was produced. About the produced intermediate member, the elastic modulus of the light transmission part was measured by applying a load to the micro indenter material using a compression micro hardness tester (FISCHER HM2000) and unloading it.
At this time, the load force was 100 mN, the load speed was 4 μm / 10 seconds, and the holding time was 60 seconds.
The elastic modulus of the light transmission part was 800 MPa.
In this way, an intermediate member (laminated body) (corresponding to 54 in FIG. 4) in which a light transmission part was formed on one surface of the base material 51 was formed.
(5) Preparation of light absorbing portion constituting composition As photocurable prepolymer, ethylene oxide, 2,2 ′-[(1-methylethylidene) bis (4,1-phenyleneoxymethylene)] bis-, homopolymer, G 20.0 parts by mass of 2-propenoate, 20.0 parts by mass of 2-phenoxyethyl acrylate, 20.0 parts by mass of α-acryloyl-ω-phenoxypoly (oxyethylene), and 2- { 13.0 parts by mass of 2- [2- (acryloyloxy) (methyl) ethoxy] (methyl) ethoxy} (methyl) ethyl acrylate and 25% carbon black having an average particle size of 4.0 μm as light absorbing particles 20.0 parts by mass of crosslinked acrylic fine particles (manufactured by Ganz Kasei Co., Ltd.) and 1-hydroxycyclohexyl as a photopolymerization initiator Eniruketon: (trade name: Irgacure 184, by Ciba Specialty Chemicals Co., Ltd.) 7.0 parts by mass, were mixed to obtain a light-absorbing portion configured composition was homogenized.
The composition excluding the light-absorbing particles of the composition constituting the light-absorbing part was applied at a thickness of 10 μm, cured by irradiating with 800 mJ / cm ² of ultraviolet light with a high-pressure mercury lamp, and the multi-wavelength Abbe refractometer DR- It was 1.547 when the refractive index of 589 nm was measured using M4 (made by Atago Co., Ltd.).
(6) Formation of light absorbing portion (see FIG. 4)
The light absorbing portion constituting composition obtained in the above (5) was supplied from the supply device onto the intermediate member produced in the above (4).
In addition, using a doctor blade disposed substantially perpendicular to the traveling direction of the intermediate member, the light absorbing portion constituting composition supplied onto the intermediate member is formed into a substantially V-shaped groove (between the light transmitting portions) formed in the intermediate member. In addition, the excess light absorbing portion constituting composition was scraped off.
Thereafter, the light absorbing part constituting composition was cured by irradiating 800 mJ / cm ² of ultraviolet light (UV light) with a high pressure mercury lamp, and the light absorbing part was formed by the cured light absorbing part constituting composition.
In this state, the light absorbing particles were filled to a depth of 6 μm. Furthermore, when only the binder of the light absorption part was applied in the same manner and cured in the same manner, the binder was filled to a depth of 3 μm. Thus, the contrast improvement layer 12 used for the optical sheet of each example of a 1st example-a 3rd example was formed on the base material layer 11, and the laminated member was obtained.

  A pressure-sensitive adhesive layer was applied and formed on the side of the base material layer 11 of the laminated member thus obtained opposite to the contrast improving layer 12 to obtain the optical sheet of the seventh example.

(Comparative Example 1)
In Comparative Example 1, the cutting angle of the tool roll in Example 1 is not changed as in Example 1, but the cutting angle at the center B in the width direction of the die roll in FIG. An optical sheet composed of an adhesive layer, a base material layer, and a contrast improving layer was prepared in the same manner as in Example 1 except that the groove for forming the light transmitting portion was cut in the entire region.

上記のように、実施例１では、比較例１に比べて、画面正面に対する画面上下の輝度の均一性が増し、コントラストが向上した。
これより、実施例１のコントラスト向上層１２を用いた実施の形態の第１の例〜第３の例の各例の光学シートにおいても、比較例１のコントラスト向上層を用いた場合に比べて、画面正面に対する画面上下の輝度の均一性が増しコントラストが向上されるものと判断される。
同様に、実施の形態の第４の例〜第６の例の各例の光学シートにおいても、コントラスト向上層１２Ａを用いていることによる上記の効果が期待できるものと判断される。 Next, the optical sheets of PDP (Panasonic VIERA TH-P50G2 50 inch) were peeled off and the optical sheets of Example 1 and Comparative Example 1 produced as described above were passed through the adhesive layer. Table 1 shows the result of measuring the luminance of the image light on the front side, on the screen, and on the bottom of the screen directly pasted on the viewer side of the PDP.
In addition, about the direction (front and back) of the said laminated body, it was set as the direction corresponding to the embodiment mentioned above.
Moreover, the numerical value (%) in Table 1 represents the ratio of the luminance when the laminate is present to the luminance at the front of the panel without the laminate at a point 2 m away from the screen front with respect to the display device. Thing.

As described above, in Example 1, as compared with Comparative Example 1, the uniformity of the brightness at the top and bottom of the screen relative to the front of the screen was increased, and the contrast was improved.
Thus, in the optical sheets of the first to third examples of the embodiment using the contrast improving layer 12 of Example 1, as compared with the case where the contrast improving layer of Comparative Example 1 is used. Therefore, it is determined that the uniformity of the brightness at the top and bottom of the screen with respect to the front of the screen is increased and the contrast is improved.
Similarly, in the optical sheets of the fourth to sixth examples of the embodiment, it is determined that the above-described effect can be expected by using the contrast improving layer 12A.

10 to 10E Optical sheet 12 Contrast improving layer 12a Light transmitting part 12b Light absorbing part 12c Layer 13 made of the same material as light transmitting part Adhesive layers 14, 14a, 14b Functional layer 15 Antireflection layer (or antiglare layer) 1
17a-17f Light intensity distribution chart 20 PDP (Plasma Display Panel)
30 Mold roll (also called roll)
35 Bite 31 Cutting remainder 51 Base material 52 Light transmission portion constituting composition 53 UV light (ultraviolet light)
54 Laminated body 54a Light transmitting portion 54b Groove (also referred to as a gap)
60, 61, 61A Die roll 61a, 61aA Groove 61b, 61bA Mountain 62, 63 Nip roll 70 Light absorbing part composition 75 Doctor blade 100 Optical sheet 111 Base layer 112 Contrast improving layer 112a Light transmitting part 112b Light absorbing part 113 Adhesive layer 212 Contrast improvement layer 212a Light transmission part 212b Light absorption part θ1, θ2 Angles 320, 320A Optical sheet 311 Base material 312 Contrast improvement layer 312a Light transmission part 312b Light absorption part 313 Adhesive layer

First, the 1st example of embodiment of the optical sheet of this invention is demonstrated based on FIG.
The optical sheet of the first example is disposed on the observer side of a PDP (plasma display panel) 20 and controls the light incident from the PDP side to emit the optical sheet 10 to the observer side. In this case, as shown in FIG. 1A, the PDP 20 is attached to the PDP 20 with an adhesive layer 13 and used.
The first example optical sheet includes, in order from the pressure-sensitive adhesive layer 13 side, a base material layer 11 serving as a base material, a light transmission portion arranged in parallel along the sheet surface of the optical sheet so that light can be transmitted, and the light transmission portion It has a structure in which a contrast enhancement layer 12, a functional layer 14, and a functional layer 15 (antireflection layer or antiglare layer) having a light absorbing portion arranged in parallel so as to be able to absorb light are laminated. It is attached directly to the PDP.
As the functional layer 15, either one of an antireflection layer or an antiglare layer is provided.
As the functional layer 14, one or more layers of a wavelength filter layer and an electromagnetic wave shielding layer are disposed.
In the optical sheet of this example, the direction of the line segment connecting from the center of the light transmission side 12a of the light transmission part 12a of the contrast improving layer 12 to the center of the light transmission part of the light transmission side of the image light is determined by the method of the optical sheet. It faces the center side of the optical sheet with respect to the line direction.
In this example, in particular, the position corresponding to the center of the screen of the PDP 20 is defined as the center of the optical sheet 10, and the above-described line segment with respect to the normal direction of the optical sheet is increased from the center of the optical sheet 10 in the vertical direction of the screen. The size of the angle gradually increases.
Here, the normal direction of the sheet surface at the center of the optical sheet is the normal direction of the optical sheet, and similarly, the normal direction of the sheet surface at the center of the contrast enhancement layer 12 is the normal direction of the contrast enhancement layer. .
In the first example, the refractive index nt and the expected angle θ of the light transmitting portion 12a are
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
The relationship is satisfied.
In the FIG. 1 (b), the shows only contrast enhancing layer 12 of the layer structure of the optical sheet 10 in order was Kusuru be easy understanding of the explanation shown in FIG. 1 (a), in FIGS. 1 (a) As shown, the PDP panel 20 is on the left side of the drawing in FIG. 1B, and the optical sheet 10 is disposed on the observer side of the PDP panel 20.
In FIG. 1B, 12a, 12b, and 12c are layers made of the same material as the light transmitting portion, the light absorbing portion, and the light transmitting portion 12a, respectively, and the layer 12c and the light transmitting portion made of the same material as the light transmitting portion. 12a is continuous and the boundary between the two is not actually seen, but here, for convenience, the boundary between the two is indicated by a dotted line.
Also, in FIG. 1B, 17a, 17b, and 17c are diagrams that relatively show the light intensity distribution in each direction of the emitted light from the light transmitting portion 12a of the image light at each position (light intensity distribution diagram). It is.

The light absorbing portion 12b is made of a predetermined material having a refractive index Nb smaller than the refractive index Np of the light transmitting portion 12a.
Thus, by setting the refractive index Np of the light transmitting portion 12a and the refractive index Nb of the light absorbing portion 12b to Np> Nb, the image light from the light source incident on the light transmitting portion 12a is converted into the light absorbing portion 12b and the light. Reflection can be performed by Snell's law at the interface with the transmission part 12a, and a bright image can be provided to the observer.
The difference in refractive index between Np and Nb is not particularly limited, but is preferably 0 or more and 0.06 or less.

The light-absorbing particles are contained in the light-absorbing part constituting composition, and act to absorb stray light and external light when the light-absorbing part is configured.
As the light-absorbing particles, light-absorbing colored particles such as carbon black are preferably used, but the light-absorbing particles are not limited to these, and colored particles that selectively absorb a specific wavelength according to the characteristics of the image light. May be used.
Specific examples include organic fine particles colored with metal salts such as carbon black, graphite, and black iron oxide, dyes, pigments, colored glass beads, and the like.
In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality, availability, and the like.
More specifically, acrylic cross-linked fine particles containing carbon black, urethane cross-linked fine particles containing carbon black, and the like are preferably used.
Such colored particles are usually contained in the light absorbing part constituting composition in a range of 3% by mass to 30% by mass.
The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less.
When forming the light absorbing portion, as shown in FIG. 4B (a diagram schematically showing a method of manufacturing the light absorbing portion), the light absorbing portion constituting composition 70 containing the colored particles is light-transmitted. while filling the grooves between the parts 54a, it includes the step of scraping off the light absorbing portion configured composition 70 of excess by using a doctor blade 75.

Next, the fourth to sixth examples will be briefly described.
Similarly to the first to third examples, the fourth to sixth examples are arranged on the viewer side of the PDP (plasma display panel) 20 and control the light incident from the PDP side to perform the observation. An optical sheet having a plurality of layers that is emitted to the user side, and is used by being attached to the PDP 20 by the adhesive layer 13.
The fourth to sixth examples are the same as the first to third examples, in which a contrast improving layer 12A is provided instead of the contrast improving layer 12, and the contrast improving layer 12A and the base are arranged from the PDP side. The material layer 11 is the same as the first example, but from the center of the light transmitting portion 12a of the contrast improving layer 12A on the image light incident side to the center of the light transmitting portion on the image light emitting side. The direction of the line connected to the optical sheet is directed toward the center side of the optical sheet with respect to the normal direction of the optical sheet, and with respect to the normal direction of the optical sheet as it moves away from the center of the optical sheet in the vertical direction of the screen. The angle of the line segment is gradually increased.
In the contrast improving layer 12 and the contrast improving layer 12A, the directions of the trapezoidal upper and lower bases in the cross section of the light transmitting portion 12a are reversed from the adhesive layer 13 side.
As described above, in the mold rolls (61 and 61A in FIG. 5) for forming the light transmitting portion of the contrast improving layer 12 of the optical sheets of the first to third examples , FIG. As shown to (a), although the cutting tool 35 is inclined and inclined to the center direction of the width direction of a metal mold | die roll with respect to the normal line direction of the said metal mold | die roll 30, 4th-6th In the mold roll for forming the light transmission part of the contrast improving layer 12A of the optical sheet, the tool 35 is set at 0 degree as the center part, and as the distance from the center increases, Cutting is performed by inclining at a large angle in a direction opposite to the center of the mold roll in the width direction.
In other words, the angle of tilting each groove cut toward the center of the groove in the width direction center of the die roll is 0, and the angle tilted toward the opposite side of the groove is increased as the distance from the center in the width direction increases. Is formed.
Of course, the directions of the trapezoidal upper and lower bases in the cross section of the light absorbing portion 12b are in reverse order when viewed from the adhesive layer 13 side.
In the case of the fourth example to the sixth example, basically, as in the first example to the third example, the display panel is assumed on the premise of an observer whose viewing angle at the center of the screen of the display panel is 0 degree. Thus, it is possible to provide an optical sheet that can prevent the brightness drop at the top and bottom of the screen and improve the in-plane brightness unevenness.

Claims (12)

  An optical sheet having a plurality of layers, disposed on the viewer side of the display panel of the display device, and controlling the light incident from the display panel side and emitting the light to the viewer side, one surface of the base material layer In addition, a contrast improving layer having a light transmission portion arranged in parallel along the sheet surface of the optical sheet so that light can be transmitted and a light absorption portion arranged in parallel so as to be able to absorb light is disposed between the light transmission portions. And an adhesive layer for attaching to the display panel, directly or indirectly, on the other side of the base material layer that is not the one surface side, or on the opposite side of the contrast improving layer to the base material layer. The direction of the line segment connecting from the center of the light transmission part of the contrast improving layer to the center of the light transmission part of the light transmission part is the center side of the optical sheet with respect to the normal direction of the optical sheet. An optical sheet characterized by being suitable for.   2. The optical sheet according to claim 1, wherein in the cross section in the thickness direction of the contrast improving layer, the light transmission part is a trapezoid having a long lower base on one side and a short upper base on the other side, and a light absorbing part. Is a triangle having a base on the other side, or a trapezoid having a short upper base on the one side and a long lower base on the other side, and the contrast enhancing layer is formed on the lower base of the light transmitting portion. An optical sheet characterized in that a layer of the same material as that of the light transmission part is arranged along the sheet surface. 3. The optical sheet according to claim 1, wherein the light transmission portion has a refractive index n _t and an expected angle θ.
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
An optical sheet characterized by satisfying the following formula   The optical sheet according to any one of claims 1 to 3, wherein the outermost layer is provided with an antireflection layer or an antiglare layer.   The optical sheet according to any one of claims 1 to 4, further comprising a wavelength filter layer having a function of suppressing transmission of light having a predetermined wavelength.   The optical sheet according to any one of claims 1 to 5, further comprising an electromagnetic wave shielding layer having a function of shielding electromagnetic waves.   An image display device comprising the optical sheet according to claim 1 arranged on an observer side of a plasma display panel (PDP).   The method for producing an optical sheet according to any one of claims 1 to 6, wherein the production of the contrast enhancement layer includes (a) a step of producing a mold roll for forming a light transmission part; (B) a step of adjusting the light transmitting portion constituting composition; and (c) supplying the light transmitting portion constituting composition on a base material prepared in advance, and between the mold roll and the nip roll, Filling the light transmitting portion constituting composition, irradiating ultraviolet rays to cure the light transmitting portion constituting composition to form a light transmitting portion; and (d) releasing the light transmitting portion from the mold roll. The mold roll is formed by cutting a groove continuous in the circumferential direction of the mold roll or in an oblique direction with respect to the circumference with a cutting tool to form a plurality of widths in the width direction. And each groove is an angle inclined toward the center of the groove at the center of the mold roll in the width direction. To 0, a manufacturing method of an optical sheet characterized by being formed by increasing the angle of tilting toward the center of the groove with distance from the widthwise center.   It is a metal mold | die roll for forming the light transmissive part of the contrast improvement layer of the optical sheet of any one of Claim 1 thru | or 6, Comprising: It is diagonal with respect to the circumferential direction of a metal mold | die roll, or a circumference | surroundings. Grooves that are continuous in the direction are cut with a cutting tool to form a plurality of grooves in the width direction. Each groove has a tilt angle of 0 toward the center of the groove at the center of the width direction of the mold roll. A mold roll formed by increasing the angle of inclination toward the center of the groove as it moves away from the center.   The method for producing a mold roll according to claim 9, wherein an angle of tilting the cutting tool toward the center side in the width direction of the mold roll is controlled for each feed of the tool roll, and one of the mold rolls in the width direction is controlled. Cutting from the end through the center to the other end, and at the center in the width direction of the mold, the angle tilted toward the center is 0, and the center in the width direction of the mold as the distance from the center increases. A method for producing a mold roll, characterized in that cutting is performed by increasing the angle of inclination to the side.   It is a metal mold | die roll for forming the light transmissive part of the contrast improvement layer of the optical sheet of any one of Claim 1 thru | or 6, Comprising: It is diagonal with respect to the circumferential direction of a metal mold | die roll, or a circumference | surroundings. Grooves that are continuous in the direction are cut with a cutting tool to form a plurality of grooves in the width direction. Each groove has a tilt angle of 0 toward the center of the groove at the center of the width direction of the mold roll. A mold roll characterized in that it is formed with a larger angle of inclination to the opposite side to the center of the groove as it is away from the center.   12. The method for producing a mold roll according to claim 11, wherein an angle of tilting the cutting tool toward the center side in the width direction of the mold roll is controlled for each feeding of the cutting tool, and one of the mold rolls in the width direction is controlled. Cutting from the end through the center to the other end, and at the center in the width direction of the mold, the angle tilted toward the center is 0, and the center in the width direction of the mold as the distance from the center increases. A method for producing a mold roll, characterized in that cutting is performed by increasing the angle of inclination to the opposite side.

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