JP2012118100A - Optical sheet and manufacturing method thereof, image display device, and mold roll and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet, for a viewer having a viewing angle of 0 degree with respect to the screen center of a display panel, which prevents lower luminance in the upper and lower screen of the display panel, and is capable of improving in-plane luminance unevenness as well as luminance unevenness for a viewer who watches the display panel from an upper side thereof.SOLUTION: An optical sheet comprises, on one surface of a basic material layer, a contrast improvement layer including light transmission parts in parallel along a sheet plane of the optical sheet so as to be capable of transmitting light and light absorption parts in parallel between the light transmission parts so as to be capable of absorbing light, and an adhesive layer for adhering the optical sheet to the display panel. The contrast improvement layer has a uniform in-plane thickness. Each light absorption part of the contrast improvement layer has a cross-sectional trapezoid shape, the height of the trapezoids is constant, and the trapezoids are formed making the lower base thereof lined with one plane of the contrast improvement layer. In addition, the light absorption parts have a narrower pitch in the upper and lower with respect to the center, and the cross-sectional trapezoid has a wider upper base and lower base in the center and a narrower in the upper and lower.

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. 10A, 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. 10B, from the PDP side (left side of the paper surface) to the observer side (right side of the paper surface), 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. 10A and the optical sheet 320A shown in FIG. 10B, 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.
There is a problem.
In FIG. 8, only the contrast improving layer 112 of the optical sheet layer structure 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. 8, 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 light emitted 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. 9A (refer to cited document 2 (Japanese Patent Laid-Open No. 2009-031322)) or FIG. 9B (cited document 3 (Japanese Patent Laid-Open No. 2008-020878)). In the case of the optical sheet having the contrast improving layer 212 shown in FIG. 9B, the contrast improving layer (112 in FIG. 9A and 212 in FIG. 9B) is asymmetrical, so that when the optical sheet is a single piece, 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. 9A mean the upper part and the lower part. In FIG. 9B, θ1 <θ2.
In addition, in the optical sheet having the contrast improving layer 212 shown in FIG. 9B (refer to cited document 3 (Japanese Patent Laid-Open No. 2008-020878)), the viewing angle is generally directed 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 an optical sheet is arranged as shown in FIG. 8, when observing from the front of the screen, the top and bottom of the screen are dark, and when observing from the top when looking down, the bottom of the screen is particularly dark. In the case of the optical sheet 100 shown in FIG. 9A or the optical sheet having the contrast improving layer 212 as shown in FIG. 9B, the contrast improving layer (112 in FIG. 9A, FIG. Since the top and bottom of the screen of 212) of b) is asymmetrical, when the optical sheet is a single unit, it is difficult to distinguish the top and bottom even if it is flipped up and down, making it difficult to manage, and further, as shown in FIG. In the case of the optical sheet having the contrast enhancement layer 212, the viewing angle is generally lowered, and there is a problem that it is dark when viewed from above, and the optical sheet having the optical function sheet layer that can solve these problems. Theft 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. In addition, we are going to provide an optical sheet that can improve the brightness unevenness of the observer viewing from the upper side of the display panel.

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 thickness of the contrast improving layer is uniform in the plane, each light absorption part of the contrast improving layer is trapezoidal in cross section, and the height of the trapezoid is constant. The bottom of the trapezoid is on one side of the contrast enhancement layer And the light absorbing portion is narrower in the vertical direction with respect to the center of the optical sheet in the cross-sectional direction, and the width of the upper and lower bases of the cross-sectional trapezoid is set to the cross-section. The directional optical sheet is characterized by being thick at the center and thin at the top and bottom.
Then, in the above-described optical sheet, and the refractive index n _t and an apparent angle θ of the light transmitting portion,
_{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 is provided with 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.
The optical sheet according to item 1 above, further comprising 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 5 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 5, wherein the contrast improving layer is manufactured by (a) forming a light transmitting 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 transmission part from the mold roll, and the mold roll is continuous in the circumferential direction of the mold roll or in an oblique direction with respect to the circumference, and the shape of the light transmission part A plurality of grooves for forming light transmission parts corresponding to the above are cut in the width direction with a cutting tool. In the width direction of the mold roll, each groove corresponds to the pitch of each light absorbing portion to be formed, the width of the upper and lower bottoms of the cross-sectional shape, and the pitch is changed in the width direction of the mold roll. The central part is wide, narrow in the width direction and away from the center, and has a constant width and a constant depth.

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 5, wherein the mold roll is in a circumferential direction. Or, a groove continuous in an oblique direction with respect to the circumference is cut with a cutting tool to form a plurality of grooves in the width direction, and each groove absorbs each light absorption formed in the width direction of the mold roll. Corresponding to the pitch and cross-sectional shape of the part, the pitch is wide in the center part in the width direction of the mold roll, and narrowed as it is away from the center in the width direction, to a predetermined constant width, a predetermined constant depth, It is characterized by being formed.
The mold roll manufacturing method of the present invention is a mold roll manufacturing method according to claim 8, wherein one groove portion for forming a light transmitting portion is formed by a cutting tool in a normal direction of the mold roll. The width of the mold roll is divided into a first cutting process that is formed by cutting at a certain depth and a second cutting process that is performed at a certain depth from the mold surface and shallower than the depth of each groove. While the direction and the pitch are alternately fed, cutting is performed from one end in the width direction of the mold roll to the other end through the center. Corresponding to the pitch and cross-sectional shape of each light absorbing part to be formed in the linear direction, the cutting tool feed pitch of the first cutting process is wide at the center part in the width direction of the mold roll and narrows as the distance from the center is wide. A predetermined constant depth from the surface at a constant radius from the axis of rotation of the mold roll In the second cutting process, the region between adjacent light transmitting portion forming grooves is shallower than the groove in the normal direction of the die roll. It is characterized by cutting at a certain depth from a surface having a certain radius from the rotation axis of the roll.

(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. An optical sheet capable of improving luminance unevenness can be provided, and in addition, an optical sheet capable of improving luminance unevenness of an observer viewed from the upper side of the display panel can be provided.
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 disposed, the thickness of the contrast improving layer is uniform in the plane, and each light absorbing portion of the contrast improving layer has a trapezoidal cross section, and the height of the trapezoid And the bottom of the trapezoid is formed so as to be aligned with one surface of the contrast improving layer, and the light absorbing portion is narrower in the top and bottom with respect to the center of the cross-sectional direction optical sheet. And the widths of the upper and lower bases of the trapezoidal cross section, Thick at the center in the plane direction optical sheet, by being thin in the vertical, more specifically, the refractive index of the light transmitting portion n _t and an apparent angle θ is
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
This is achieved by satisfying the relationship of
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) to be stronger on the observer side, the luminance distribution on the entire screen can be reduced in variation. .
When observing in front of the screen, the top and bottom of the screen are not dark, and even the observer from the top of the screen (the observer who is standing) does not darken the bottom of the screen.

The refractive index n _t of the light transmitting portion and the expected angle θ are
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
By adopting the form of the invention of claim 2 which satisfies the relationship of the above formula, the effect of absorbing external light is reduced, the bright room contrast can be prevented from being lowered, and the viewing angle for 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 absorbing portion of one light transmitting portion to the outgoing side of the upper light absorbing portion. The angle of view with respect to θ is the expected angle θ, and the viewing angle emitted into the air is calculated as asin (n _t × sin θ) with respect to θ in the medium (light transmitting portion), from the refractive index of the light transmitting portion, This means that a viewing angle of 30 ° to 60 ° when exiting into the air is desirable.
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 °. , more becomes substantially constant at a high angle, the value of the previous asin (n _t × sinθ) is equivalent to the inflection point of the 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. In FIG. 6, the transmittance in the direction higher than the viewing angle inflection point is due to the image light that has passed through the light absorbing portion. However, in the point of widening the viewing angle in the display panel, Under the screen of the panel, it is also necessary to increase the amount of image light that has passed through the light absorbing portion.

Moreover, the form of invention of Claim 3 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 4 provided with the wavelength filter layer which has a function which suppresses 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 5 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). In this case, it is possible to provide an optical sheet capable of improving the in-plane brightness unevenness and further improving the brightness unevenness of an observer viewed from the upper side of the display panel.

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. In addition, it is possible to provide a method for producing an optical sheet that can improve in-plane brightness unevenness and, in addition, can improve brightness unevenness of an observer viewed from above the display panel.
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. In addition, the in-plane luminance unevenness can be improved, and in addition, the optical sheet contrast enhancement layer capable of improving the luminance unevenness of the observer viewed from the upper side of the display panel can be mass-produced.

  As described above, the present invention is based on the premise of an observer who sets the viewing angle at the screen center of the display panel to 0 degree, and can prevent luminance reduction at the top and bottom of the display panel and improve in-plane luminance unevenness. Further, it is possible to provide an optical sheet that can improve luminance unevenness of an observer viewed from the upper side of the display panel and 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 a mold 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. It is the schematic explaining the brightness | luminance measurement state by standing. FIG. 8 is a schematic diagram showing an observation state of an observer when a conventional optical sheet is arranged on the observer side of the display panel. FIG. 9A is a schematic sectional view showing a conventional optical sheet, and FIG. 9B is a schematic sectional view showing a conventional contrast enhancement layer. 10 (a) and 10 (b) 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 optical sheet of the first example 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 The contrast enhancement layer 12, the functional layer 14, and the functional layer 15 having light absorption portions arranged in parallel so as to be able to absorb light between the portions are laminated, and are directly attached to the PDP by the adhesive layer 13.
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 first example, in particular, the thickness of the contrast enhancement layer 12 is uniform in the plane, and each light absorbing portion of the contrast enhancement layer 12 has a trapezoidal cross section, and the height of the trapezoid is constant, The bottom is aligned with one surface of the contrast enhancement layer, and the light absorbing portion 12b has a pitch narrower in the vertical direction with respect to the direction of the cross section and the center of the optical sheet. The widths of the upper base and the lower base of the trapezoidal cross section are thicker in the cross-sectional direction, the center of the optical sheet, and are gradually narrowed away from the center of the optical sheet 10 in the vertical direction of the screen.
In addition, although mentioned later, the cross-sectional shape of the light transmission part 12a and the light absorption part 12b is substantially trapezoid, Here, the height of those trapezoid is respectively set to the height of the light transmission part 12a, and the light absorption part. The height is 12b.
Here, the normal direction of the sheet surface at the center of the optical sheet is the normal direction of the optical sheet. 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. It is said.
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.
In FIG. 1B, 17a, 17b, and 17c are general-purpose diagrams (light intensity distributions) that relatively show the light intensity distribution in each direction of light emitted from the light transmitting portion 112a of the image light at each position. Figure).

In the first example, as shown in FIG. 1B, in the cross section in the thickness direction of the contrast enhancing layer 12, the light transmitting portion 12a has a long bottom on one side which is the incident side of the image light, and the emission of the image light. The light absorbing portion 12b has a substantially trapezoidal shape having a short upper base on the one side and a long lower base on the other side.
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 in a substantially planar shape, and 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 cross-sectional shape of the light absorbing portion 12b does not have 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. It is preferable that the angle of the hypotenuse when the hypotenuse of the trapezoidal cross section of the portion 12b is a straight line is 0 degree or more and 10 degrees 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, and in addition, it is possible to provide an optical sheet that can improve luminance unevenness of an observer viewed from the upper side of the display panel.
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. The intensity distribution (see 17a and 17c in FIG. 1) of the light depending on the emission direction of the light is adjusted so as to be strong on the viewer side, and the luminance distribution on the entire screen can be reduced, and at the same time Also, it is possible to reduce variations in the luminance distribution on the entire screen even for the observer on the upper side of the screen.
In the first example, when the image is observed in front of the screen, the top and bottom of the screen are not darkened, and a decrease in bright room contrast can be prevented.

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 that satisfies the relationship, the external light absorption effect is reduced, the bright room contrast can be prevented from being lowered, and the viewing angle for the PDP can be secured.

Moreover, in the optical sheet of the first example, in the formation of the light transmission part of the contrast enhancement layer using a mold roll (see FIG. 4A), the release of the light transmission part from the mold is ensured. However, in order to prevent a decrease in the transmittance of the image light, the direction connecting the center on the incident side and the center on the emission side of the light absorbing portion is 0 degree or more and 10 degrees or less with respect to the normal direction of the optical sheet. is there.
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 premised that the angle of the light absorbing part is changed at least at the top and bottom of the screen, but the slope angle is 5 degrees on one side and the slope angle of the light absorbing part is minimum at the top and bottom of the screen. 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, one side is 2 degrees, and at this time, the direction connecting the center on the incident side and the center on the exit side of the light absorbing portion is 0 degree or more and 4 degrees or less with respect to the normal direction of the optical sheet.

As the functional layer 15, either one of an antireflection layer or an antiglare layer is disposed, but when an antireflection layer is provided as the outermost layer, external light is reflected on the viewer side of the optical sheet. Returning to the viewer side, it is possible to suppress so-called reflection and making it difficult to see the image.
When an antiglare layer is provided as the outermost layer, 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 disposed 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. It is cut in line with the normal direction which is the direction of the diameter.
FIG. 2A shows a cross section in the region A of the mold roll shown in FIG.
In FIG. 2A, only one cutting tool is actually used, but a plurality of cutting tools are shown for 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 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.

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 70 containing the colored particles is light-transmitted. A step of scraping off an excess of the light absorbing portion constituting composition 70 using the doctor blade 75 while filling the groove 54b between the portions 54a 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.
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.
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 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, and in addition, it is possible to provide an optical sheet that can improve the luminance unevenness of an observer viewed from the upper side of the display panel.
The light intensity distribution (see the ellipses 17a and 17c in FIG. 1B) corresponding to the emission direction from the light transmitting portion corresponding to the position away from the center of the screen (upper and lower positions of the screen) becomes stronger on the observer side. Thus, the luminance distribution in the entire screen can be reduced in variation.
Also in this example, when observing in front of the screen, the upper and lower sides of the screen do not become dark, and a decrease in bright room contrast can be prevented.
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 attached to the PDP 20 with the 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 wave 7 length 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 screen of the display panel to 0 degree. It is possible to provide an optical sheet that can prevent the decrease and improve the in-plane luminance unevenness, and in addition, can provide an optical sheet that can improve the luminance unevenness of the observer viewed from the upper side of the display panel.

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. (See FIG. 3 (c) to FIG. 3 (e))
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. Although the material layer 11 is used, the contrast improving layer 12 and the contrast improving layer 12A have the trapezoidal upper and lower bases in the cross section of the light transmitting portion 12a in the reverse order when viewed from the adhesive layer 13 side. Thus, the contrast improving layer 12A is obtained by reversing the contrast improving layer 12 upside down.
Of course, the directions of the upper base and the lower base of the trapezoid in the cross section of the light absorbing portion 12b are reversed 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. It is possible to provide an optical sheet that can prevent brightness drop at the top and bottom of the screen and improve in-plane brightness unevenness. In addition, it is possible to provide an optical sheet that can improve brightness unevenness of the observer viewing from the upper side of the display panel Yes.

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) including the adhesive layer 13, the contrast improving layer 12 </ b> A, and the base material layer 11 from the PDP side without the functional layer 14 and the functional layer 15. It is done.
Further, in each example, the position corresponding to the center of the screen of the PDP 20 is limited to the upper and lower regions, and the center of the optical sheet 10 is set higher than the center of the optical sheet 10. In the same way as in the first example, it is possible to reduce the brightness at the top and bottom of the display panel, assuming that the viewing angle at the center of the display panel is 0 degree. It is possible to provide an optical sheet that can improve luminance unevenness, and in addition, it is possible to provide an optical sheet that can improve luminance unevenness of an observer viewed from the upper side of the display panel.
In addition, there are various aspects of changes that gradually reduce the width and pitch of the light absorbing portion 12b as the distance from the center of the optical sheet increases in the vertical direction of the screen. If it can improve, it will not specifically limit.
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 position and the cutting depth were changed to change the shape of the groove 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.
Using such a diamond tool, the outer periphery of the copper plating layer of the mold roll was cut to form a groove.
In FIG. 2A, numbers 1 to 4 assigned to the cutting tool 35 indicate the order of cutting.
Here, in the normal direction of the mold roll, a first cutting process in which one groove for forming a light transmitting portion is cut at a certain depth by a cutting tool with a cutting tool, and a certain depth from the mold surface. Then, the second cutting process of cutting shallower than the depth of each groove is alternately performed by feeding the pitch direction in the width direction of the mold roll, while passing through the center from the one end in the width direction of the mold roll and the other. The first cutting process is performed in the normal direction of the mold roll in accordance with the pitch and cross-sectional shape of each light absorbing portion to be formed. The center of the mold roll in the width direction is wide, narrow in the width direction and away from the center, and from the surface at a certain radius from the rotation axis of the mold roll to a predetermined constant depth, The second cutting process is performed in the normal direction of the mold roll. The region between the parts forming grooves shallower than the groove, at a certain depth from the surface at a constant radius from the rotational axis of the mold roll, cutting.
Due to the change in the bite feed pitch in the first cutting process, the remaining portion between the adjacent grooves is wide at the center portion in the width direction of the mold roll and narrows as the distance from the center increases.
Each of cutting 2 and cutting 4 in FIG. 2A corresponds to a first cutting process, and each of cutting 1 and cutting 3 in FIG. 2A corresponds to a second cutting process.
Here, cutting was performed as follows.
The second cutting process for cutting to a depth of 10 μm from the surface of the mold and the first cutting process for cutting to a depth of 95 μm from the mold surface are repeated by sending the bite position in the width direction of the mold roll, Cutting starts from the cutting start part (also called cutting start part) at one end in the width direction of the die roll to the cutting end part (also called cutting end part) at the other end in the width direction of the die roll. The pitch of the part is set to 42 μm, and then the pitch is continuously increased so as to be 45 μm at the center in the width direction of the mold roll. Further, the pitch is continuously decreased and the end point of the mold roll is cut. It cut so that it might become 42 micrometers.
Here, at the cutting start portion at one end in the width direction of the mold roll, first, a second cutting process (corresponding to cutting 1) is performed to cut to a depth of 10 μm from the mold surface, and then the mold surface To a depth of 95 μm is performed (corresponding to cutting 2).
Then, at the end point of cutting at one end in the width direction of the mold roll, after performing the first cutting process to cut to a depth of 95 μm from the mold surface, the second to cut to a depth of 10 μm from the mold surface. A cutting process is performed and cutting is terminated.
As a result, at the cutting start portion at one end in the width direction of the mold roll and at the cutting end portion at the other end, the apex width of the die 3 μm, the cutting width of the die surface 39 μm, the uncut width of the die bottom 7 μm, the die bottom A groove having a cutting width of 35 μm is formed, and at the center of the mold roll in the width direction, the apex width of the mold is 6 μm, the cutting width of the mold surface is 39 μm, the uncut width of the mold bottom is 10 μm, and the cutting of the mold bottom is performed. A groove having a width of 35 μm was formed.
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. The light transmitting part constituting composition was applied at a thickness of 100 μm, and the light transmitting part constituting composition was cured by irradiating an ultraviolet ray of 800 mJ / cm ² with a high pressure mercury lamp, and the multiwavelength Abbe refractometer DR-M4 ( The refractive index of 589 nm was measured using 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 (see FIG. 4)
The base material prepared in the above (3) was inserted between the mold roll and the nip roll prepared in the above (1) and conveyed.
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.
Thus, the intermediate member (laminated body) 54 in which the 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.

The 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.
The width of the lower base and the upper base of the light transmission part are 39 μm and 35 μm at the center, respectively.
The width of the lower and upper bases of the light absorbing portion is 10 μm and 6 μm at the center and 7 μm and 3 μm at the top and bottom, respectively, and the distance between two adjacent light absorbing portions (pitch). Also) was 45 μm at the center and 42 μm at the top and bottom.

(Example 2)
In Example 2, the cutting start part and the cutting end part of Example 1 were cut at a pitch of 42.0 μm to 43.5 μm to produce the optical sheet of the seventh example. Same as Example 1.

(Comparative Example 1)
In Comparative Example 1, the width of the groove for forming the light transmission part of the mold roll in Example 1 is constant in the plane as the center width in Example 1, and the cutting depth is constant in the plane. And, the pitch of the cutting remaining portion for forming the light absorption part between the grooves to be cut was constant in-plane to 45 μm, and the entire area was cut, and the others were the same as in Example 1, the adhesive layer, An optical sheet composed of a base material layer and a contrast improving layer was produced.

上記のように、実施例１、実施例２では、比較例１に比べて、画面正面の輝度の均一性が増し、また画面下の暗さを改善することができた。
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、画面正面の輝度の均一性が増し、また画面下の暗さを改善することができるものと判断される。 Next, an optical filter (also referred to as an optical sheet) of PDP (Panasonic VIERA TH-P50G2 50 inch) was peeled off, and each optical sheet of Example 1 and Comparative Example 1 manufactured as described above was used. The panel was directly pasted on the observer side through the adhesive layer, and image light was observed from the front of the screen and the upper side of the screen.
The result of measuring the luminance (cc / m ² ) at a point 2 m away from the front of the screen with respect to the display panel of the display device is as shown in Table 1. Also, as shown in FIG. The brightness (cc / m ² ) measured when looking down from 45 degrees is as shown in Table 2.

As described above, in Example 1 and Example 2, the uniformity of the brightness at the front of the screen increased compared to Comparative Example 1, and the darkness at the bottom of the screen could be 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 luminance uniformity on the front of the screen is increased and the darkness at the bottom of the screen can be improved.

10 to 10E Optical sheet 12 Contrast improvement layer 12a Light transmission part 12b Light absorption part 12c Layer 13 made of the same material as the light transmission part Adhesive layers 14, 14a, 14b Functional layer 15 Antireflection layer (or antiglare layer)
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 part composition 52A Supply device 53 UV light (ultraviolet light)
54 Laminate (also called intermediate member)
54a Light transmission 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

Claims (9)

  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 thickness of the contrast enhancement layer is uniform in the plane, and each light absorption part of the contrast enhancement layer is trapezoidal in cross section, and the height of the trapezoid is constant, and the bottom base of the trapezoid is It is formed on one side of the contrast enhancement layer, The light absorbing portion is narrower in the vertical direction with respect to the center of the cross-sectional direction optical sheet, and the width of the upper and lower bases of the cross-sectional trapezoid is set at the center of the cross-sectional direction optical sheet. An optical sheet characterized by being thick and thin at the top and bottom. The optical sheet according to claim 1, wherein the refractive index n _t and the expected angle θ of the light transmission part are:
_{30 ° ≦ asin (n t ×} sinθ) ≦ 60 °
An optical sheet characterized by satisfying the relationship:   The optical sheet according to claim 1, wherein the outermost layer is provided with an antireflection layer or an antiglare layer.   4. The optical sheet according to claim 1, further comprising a wavelength filter layer having a function of suppressing transmission of light having a predetermined wavelength.   5. The optical sheet according to claim 1, further comprising an electromagnetic wave shielding layer having a function of shielding electromagnetic waves.   6. An image display device, wherein the optical sheet according to claim 1 is 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 5, 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 a groove for forming a light transmission part corresponding to the shape of the light transmission part continuously in the circumferential direction of the mold roll or in an oblique direction with respect to the circumference. Are cut with a cutting tool and formed in the width direction. The width of the mold roll is wide in the center in the width direction and away from the center, corresponding to the pitch of each light absorbing part to be formed and the width of the upper and lower bases of the cross-sectional shape. Accordingly, the method for producing an optical sheet is characterized in that the optical sheet is formed to have a narrow width, a constant width, and a constant depth.   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 5, 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 corresponds to the pitch and cross-sectional shape of each light absorbing portion to be formed in the width direction of the mold roll. The width of the die roll is wide in the center, and the width of the mold roll is narrowed away from the center, so that the pitch is formed to have a predetermined constant width and a predetermined constant depth. Mold roll to do.   9. The method for producing a mold roll according to claim 8, wherein the first roll part is formed by cutting one groove part for forming a light transmission part at a certain depth by a cutting tool in the normal direction of the mold roll. While performing the cutting process and the second cutting process of cutting at a certain depth from the mold surface and shallower than the depth of each groove part, by alternately feeding the mold roll in the width direction, Cutting is performed from one end in the width direction of the roll to the other end through the center, and the first cutting treatment is performed in the normal direction of the mold roll, and the pitch of each light absorbing portion to be formed, Corresponding to the cross-sectional shape, the tool feed pitch of the first cutting process is wide at the center of the mold roll in the width direction and narrower as it goes away from the center in the width direction, so that it has a constant radius from the axis of rotation of the mold roll. The tool is cut at a predetermined constant depth from the surface at a width of the cutting tool. In the second cutting process, in the normal direction of the mold roll, a region between adjacent light transmission part forming grooves is shallower than the groove and constant from a surface having a constant radius from the rotation axis of the mold roll. A method for producing a mold roll, characterized by cutting at a depth of 5 mm.

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