JP4882635B2 - Optical sheet and display device - Google Patents

Description

  The present invention relates to an optical sheet that is used in a plasma television and can be disposed on an observer side of an image source to appropriately control image light and external light.

  In a display device such as a television using a plasma display panel (hereinafter sometimes referred to as “PDP”), an optical sheet is disposed on the viewer side of the PDP. This optical sheet transmits the image light and provides the image to the viewer side, and the light that appropriately blocks or reflects the image light and external light to improve the contrast and suppress the ghost. And an absorption part.

  However, since these prism parts and light absorption parts are arranged alternately and are in the form of horizontal stripes or vertical stripes, when a dark image or a video with much black is projected even when the PDP is not lit and when lit In some cases (hereinafter, sometimes referred to as “when not lit”, etc.), the screen is exposed to external light, which may cause moiré fringes in relation to the reflected light. This is a defect in the appearance of the screen when it is not lit.

  Patent Documents 1 and 2 disclose means for preventing the occurrence of interference fringes in a display device using a PDP.

JP-A-10-283122 JP 2001-34184 A

  However, the technique described in Patent Document 1 is a technique for preventing the generation of Newton rings, and the cause of the generation of interference fringes is different from that of moire fringes. Therefore, the above-described moire fringes are not always eliminated by the method described in Patent Document 1, and a more reliable and reliable method has been desired.

  Further, in the method described in Patent Document 2, it is necessary to perform mat processing on the PDP substrate itself as a light source, and the mat processing needs to be changed and newly manufactured depending on the form of the optical sheet, which increases costs. There was a problem inviting.

  Therefore, the present invention provides an optical sheet that is disposed on the viewer side of a PDP and has an optical function such as improving contrast without generating moire fringes, and a display device including the optical sheet. And

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  As a result of intensive studies, the inventors have found that one of the causes of the moire fringes is as follows. That is, at the time of non-lighting or the like, a part of the external light incident on the optical sheet passes through the prism portion and reaches the PDP, and the external light is reflected on the surface of the PDP. This reaches the light incident surface of the optical sheet, where it is reflected and reaches the PDP again. In this way, a part of the external light is reflected between the light absorbing part and the PDP a plurality of times without reducing the intensity so much and finally projected from the prism part. The light that has undergone such reflection, for example, is reflected once by the PDP and is directly projected from the prism portion to the outside, causing an optical path difference, and moire due to the relationship with the wavelength of the external light. One cause of the generation of stripes. Therefore, the inventors have intensively studied based on these findings and completed the following invention.

According to the first aspect of the present invention, a plurality of projections are arranged on the image projection side of the plasma display panel (2) with a predetermined interval from the image projection surface of the plasma display panel, and control and project incident light. an optical sheet having a layer of stacked (10, 20), the cross-sectional shape is substantially trapezoidal, prism portions (12, 12 having optical transparency that is arranged along a sheet surface, ..., 22, 22, ...) and a light absorption part (13, 13, ..., 23, 23, ...) disposed between the prism parts and having a wide bottom surface in a cross-sectional shape on the plasma display panel side. An optical sheet comprising light diffusing means (15, 15,..., 23a, 23a,...) Having a light diffusing action on a wide bottom surface, and no light diffusing means being disposed on the surface of the prism portion. By providing the above To resolve the problem.

  The invention according to claim 2 is characterized in that the light diffusing means of the optical sheet (20) according to claim 1 depends on the shape of the bottom surface (23a, 23a,...) Of the light absorbing portion (23, 23,...). And

  The invention according to claim 3 is a polyhedron or curved surface in which the shape of the bottom surface (23a, 23a,...) Of the optical sheet (20) according to claim 2 is convex on the side opposite to the plasma display panel (2) side. It is characterized by being.

  The invention according to claim 4 is characterized in that the bottom surface (23a ', 23a', ...) of the optical sheet (20 ') according to claim 2 or 3 is a mat surface.

  Here, the “mat surface” means a surface having minute irregularities on the surface (the same applies hereinafter).

  The invention according to claim 5 is the light diffusion layer (15, 15,...) In which the light diffusion means of the optical sheet (10) according to claim 1 is laminated on the bottom surface of the light absorbing portion (13, 13,...). ).

  In the invention according to claim 6, the interface between the light absorbing portion (13, 13,...) Of the optical sheet (10) according to claim 5 and the light diffusion layer (15, 15,...) Is a plasma display panel. (2) It is a polyhedron or a curved surface that is convex on the opposite side to the side.

  The invention according to claim 7 is characterized in that the side surface of the plasma display panel (2) of the light diffusion layer (15, 15, ...) of the optical sheet (10) according to claim 6 is a matte surface. .

  In the eighth aspect of the invention, the light diffusion layer (15, 15,...) Of the optical sheet (10) according to the seventh aspect contains light diffusion particles (15b ′, 15b ′,. The matte surface is formed by disposing a part of the diffusing particles so as to protrude toward the plasma display panel (2).

  As for invention of Claim 9, the light-diffusion layer (15,15, ...) of the optical sheet (10) as described in any one of Claims 5-8 is a light absorption part (13,13, ...). It is a white layer laminated on the bottom surface.

  The invention according to claim 10 is characterized in that the haze value of the optical sheet (10, 20) according to any one of claims 1 to 9 is greater than 18.0%.

  Here, the “haze value” means a value defined in JIS K7105, and is a ratio of diffuse transmittance to total light transmittance.

  The invention according to claim 11 is the cross-sectional shape of the light absorbing portion (13, 13, ..., 23, 23, ...) of the optical sheet (10, 20) according to any one of claims 1 to 10. The slope portion is curved and / or bent so that the angle formed by the slope portion extending in the sheet thickness direction from the bottom edge and the normal line of the sheet light exit surface is different between one and the other in the sheet thickness direction. It has a cross-sectional shape.

  The invention according to claim 12 is the cross-sectional shape of the light absorbing portion (13, 13, ..., 23, 23, ...) of the optical sheet (10, 20) according to any one of claims 1 to 10. The slope portion has a polygonal cross-sectional shape so that the angle between the slope portion extending from the bottom edge in the sheet thickness direction and the normal line of the sheet exit surface is different between one and the other in the sheet thickness direction. The angle formed is 0 to 10 degrees at any position.

  As for invention of Claim 13, light absorption particle | grains (16, 16, ...) whose average particle diameter is 1 micrometer or more in the light absorption part of the optical sheet (10, 20) as described in any one of Claims 1-12. , 26, 26,...).

  Here, “1 μm” when “average particle diameter is 1 μm or more” is a value obtained by particle size measurement by the weight distribution method.

The invention according to claim 1 4, to solve the above problems by providing a display apparatus characterized by the optical sheet is provided according to any one of claims 1 to 1 3 (1).

  According to the present invention, it is possible to provide an optical sheet and a display device that have an optical function such as a contrast improvement at the time of lighting, and can suppress moire fringes caused by outside light at the time of non-lighting. it can.

  Further, according to the present invention, the light diffusing means is provided only on the bottom surface side of the light absorbing portion, and is not disposed on the prism portion through which the image light is transmitted. Thereby, since the main image light is not affected by the light diffusing means, it is possible to prevent problems such as a decrease in transmittance. In addition, it is possible to prevent a decrease in the resolution of the image light.

  Furthermore, in the optical sheet of the present invention, at least a part of the light reflected by the light diffusing means is finally transmitted to the observer side, so that a large amount of light is absorbed by the light absorbing portion without being diffusely reflected. The transmittance can be improved as compared with the optical sheet.

  Such an operation and gain of the present invention will be made clear from the best mode for carrying out the invention described below.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  FIG. 1 is a diagram schematically showing a layer structure of a cross section of an optical sheet 10 according to the first embodiment of the present invention. In FIG. 1, some repetitive symbols are omitted for ease of viewing (the same applies to the following drawings). The optical sheet 10 has an optical function sheet layer 11, a PET film layer 17 as a base material layer, and an adhesive layer 18 laminated in this order. Each of the above layers is formed so as to extend in the back / front direction of the drawing while maintaining the cross section shown in FIG. Each layer will be described below.

  The optical function sheet layer 11 includes prism portions 12, 12,... Having a substantially trapezoidal cross section in a cross section orthogonal to the sheet surface of the optical sheet 10, and a light absorbing portion disposed between the prism portions 12, 12,. And light diffusion layers 15, 15,... Provided on the bottom surfaces of the light absorbing portions 13, 13. FIG. 2 shows an enlarged view focusing on one light absorbing portion 13 and the prism portions 12 and 12 adjacent thereto. The optical function sheet layer 11 will be described with reference to FIGS. 1 and 2 and the drawings appropriately shown.

  The prism parts 12, 12,... Are elements having a substantially trapezoidal cross section arranged so that the upper and lower bases face the PDP 2 side and the viewer side (see FIG. 8). The prism portions 12, 12,... Are made of a light transmissive resin having a refractive index Np. This is usually formed of, for example, epoxy acrylate having a characteristic of being cured by ionizing radiation, ultraviolet rays or the like.

  The light absorbing portions 13, 13,... Are portions disposed between the prism portions 12, 12,. The light absorbing parts 13, 13,... Are binder parts 14, 14,... Filled with a material having a refractive index Nb, and light absorbing particles 16, 16,. It has.

  The binder material filled in the binder parts 14, 14,... Is made of a material that is Nb having a refractive index lower than the refractive index Np of the prism parts 12, 12,. The difference in refractive index between Np and Nb is not particularly limited, but is preferably 0 to 0.06. The material used as the binder material is not particularly limited, and examples thereof include urethane acrylate having a characteristic of being cured by ionizing radiation, ultraviolet rays, and the like.

  The light absorbing particles 16, 16,... Are particles having an average particle diameter of 1 μm or more, and are colored to a predetermined concentration with a pigment such as carbon or a dye such as red, blue, or yellow. For this, for example, commercially available colored resin fine particles can be used. The refractive index Nr of the light absorbing particles 16, 16,... Is not particularly limited.

  The light diffusing layers 15, 15,... Are arranged on the bottom surfaces of the light absorbing portions 13, 13,... And are provided with a mat surface 15 a having fine irregularities so that the left side surface of FIG. It is. The form of the mat surface 15a is not particularly limited as long as it is formed as a surface having a light diffusing action. An example is shown in FIG. 3A shows the light diffusion layer 15 and the mat surface 15a of the present embodiment, and FIG. 3B schematically shows the light diffusion layer 15 ′ and the mat surface 15a ′ of the modification. is there.

  The light diffusing layer 15 shown in FIG. 3A has a mat surface 15a because the side surface opposite to the surface in contact with the binder portion 14 has jagged irregularities. With this configuration, the light reaching the mat surface 15a is scattered and reflected and diffused. The light diffusion layer 15 is formed by, for example, an ultraviolet curable resin, and the mat surface 15a is formed by transferring the unevenness corresponding to the unevenness to the mold at the time of molding. The degree of unevenness is not particularly limited as long as light is appropriately diffused, but it is preferable that the average roughness is 1 to 10 μm as an index of surface roughness.

  The light diffusing layer 15 ′ shown in FIG. 3B is obtained by adding light diffusing beads 15 b ′, 15 b ′, and 15 b ′ to the ultraviolet curable resin in the light diffusing layer 15 ′. At this time, a part of the light diffusing beads 15b ′, 15b ′, and 15b ′ is added so as to protrude to the side opposite to the surface in contact with the binder part 14, thereby forming the mat surface 15a ′ as shown in FIG. be able to. Examples of the light diffusion beads include silica beads, and the particle diameter is preferably 1 to 20 μm.

As shown in FIGS. 1 and 2, the shape of the optical function sheet layer 11 is such that the prism portions 12, 12,... Have a substantially trapezoidal cross section, and are formed between the light absorbing portions 13, 13, ... has a triangular cross-section. However, in order to appropriately control light, these shapes are not particularly limited, and appropriate shapes are appropriately adopted. FIG. 4 shows another modification. FIG. 4 is a view corresponding to FIG. 2 and shows one light absorbing portion 13 ″ and prism portions 12 ″ and 12 ″ arranged on both sides thereof. As can be seen from FIG. 4, the inclined surface of the light absorbing portion 13 ″ (the inclined surfaces of the prism portions 12 ″ and 12 ″) is composed of two planes, not one plane. That is, the cross section has a polygonal slope. Specifically, the inclined surface disposed on the light diffusion layer 15 ″ side (left side of the sheet) has an angle θ ₁ with respect to the sheet exit surface of the optical sheet. On the other hand, the inclined surface arranged on the PET film layer 17 side (the right side of the drawing) has an angle θ ₂ with respect to the sheet exit surface of the optical sheet. This angle is preferably in the range of 0 to 10 degrees with the relationship of θ ₁ > θ ₂ . A more preferable angle is 0 to 6 degrees. Further, the two inclined surfaces intersect with each other in the thickness direction of the optical functional sheet layer 12 at positions divided into T ₁ and T ₂ . T ₁ and T ₂ are preferably the same size.

  Although the said other modification is an example comprised by two planes, the broken line shape in a cross section may be formed by comprising by more planes. Furthermore, this may be a curved surface.

  FIG. 5 shows still another modification. In still another modified example, the interface between the bottom surface of the light absorbing portion 13 ″ ″ and the light diffusion layer 15 ″ ″ is a curved surface that is convex toward the viewer side. In this way, the interface may be a curved surface. Further, the curved surface portion may be a convex portion made of a polygon.

  Further, the light diffusion layers 15, 15 ′, 15 ″ and 15 ″ ″ shown above may be white layers. Thereby, the effect of diffuse reflection of light can be further improved and the transmittance can be increased. In order to make the white layer white, it is possible to apply white ink or white paste directly, or to form a layer by containing these in a resin.

  Returning to FIG. 1, another configuration of the optical sheet 10 will be described. The PET film layer 17 is a film layer serving as a base for forming the optical functional sheet layer 11 on the PET film layer 17 and is formed mainly of PET. The PET film layer 17 only needs to contain PET as a main component, and may contain other resins. Here, the main component means 50% by mass or more based on the whole PET film layer. Various additives may be added in appropriate amounts. Examples of general additives include phenol-based antioxidants, lactone-based stabilizers, and the like.

  As will be described later, the pressure-sensitive adhesive layer 18 is a layer in which a pressure-sensitive adhesive for adhering the optical sheet 10 to, for example, a glass layer that is disposed to ensure the strength, flatness, and the like of the plasma television 1 is disposed. The material of the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer 18 is not particularly limited as long as it transmits light and can appropriately bond the optical sheet 10 to the other. Examples thereof include an acrylic copolymer, and the adhesive strength thereof is, for example, about several N / 25 mm to 20 N / 25 mm.

  With the optical sheet 10 having the above-described configuration, even when external light is incident and the light reflected from the PDP is received when the PDP is not lit, the light is diffused by the mat surface and light interference is suppressed. Therefore, the generation of moire fringes can be suppressed. Details will be described later.

  FIG. 6 shows one of the optical sheet 20 of the present invention according to the second embodiment, and one of the optical sheets 20 ′ that is a modification thereof, one light absorbing section 23, 23 ′, and prism sections 22 disposed on both sides thereof. It is the figure which paid its attention to 22, 22 ', and 22'. Since other configurations are the same as those of the optical sheet 10 of the first embodiment, description and explanation are omitted. FIG. 6A shows an optical sheet 20, and FIG. 6B shows an optical sheet 20 'according to a modification thereof.

  In the optical sheets 20 and 20 ′ of the second embodiment, the light diffusing means is configured by the shape of the bottom surfaces 23 a and 23 a ′ of the light absorbing portions 23 and 23 ′. Specifically, in the optical sheet 20 shown in FIG. 6A, the bottom surface 23a of the light absorbing portion 23 is formed by a curved surface. Thereby, the light irradiated on the bottom surface 23a is diffused and reflected by the action of the curved surface. Accordingly, light is diffusely reflected by the bottom surface 23a, and the above-described interference of light can be suppressed, so that generation of moire fringes can be suppressed.

  According to the optical sheet 20, since it is not necessary to form a light diffusion layer, it is easy to manufacture and the cost can be reduced.

  On the other hand, in the optical sheet 20 ′ shown in FIG. 6B, the bottom surface 23 a ′ of the light absorbing portion 23 ′ is a mat surface. As a result, the light applied to the bottom surface 23a 'is diffused and reflected by the action of the mat surface. Therefore, the light is diffusely reflected by the bottom surface 23a ', and the above-described interference of the light is suppressed, so that the generation of moire fringes can be suppressed.

  FIG. 7 is a cross-sectional view of the optical sheet 30 of the present invention according to the third embodiment, schematically showing the layer configuration. The optical sheet 30 of the present embodiment is one in which another optical functional sheet layer 31 is sandwiched between the optical functional sheet layer 11 and the PET film layer 17 of the optical sheet 10 of the first embodiment. is there. At this time, in the optical function sheet layer 31, the prism part 32 and the light absorption part (not shown in the figure) are orthogonal to the prism parts 12, 12,... And the light absorption parts 13, 13,. To be arranged. That is, in FIG. 7, the prism portions 32 and the light absorbing portions of the optical function sheet layer 31 are alternately arranged in parallel in the back / front direction of the paper.

  When the two optical function sheet layers 11 and 31 are laminated in this way, the light diffusing means may be provided only in the optical function sheet layer 11 arranged closest to the light source.

Also, the angles (θ ₁ , θ ₂ in FIG. 4) that the slope of the light absorbing portion 13 of the optical function sheet layer 11 have and the angles that the slope of the light absorbing portion of the optical function sheet layer 31 that is defined similarly have. It may be the same or different. However, with respect to the average angle of the angle of the inclined surface, the light absorbing portions 13, 13,... Are arranged horizontally in the average angle of the optical function sheet layer 31 in which the light absorbing portions are arranged vertically. It is preferably smaller than the average angle of the optical function sheet layer 11.

  In the optical sheet of the present invention described above, the material of the base material layer is not necessarily PET, such as polybutylene terephthalate resin (PBT) or polytrimethylene terephthalate (PTT) resin. A “polyester resin” can be used. In the present embodiment, it has been described that a resin having PET as a main component is a preferable material from the viewpoint of mass productivity, price, availability, etc. in addition to performance.

Furthermore, the optical sheet 10 may be provided with a functional film layer such as an infrared cut film layer, an electromagnetic wave shield layer, or a film layer for preventing reflection on one surface thereof.

  The optical functional sheet layer of the optical sheet of the present invention is formed on the PET film layer 17 as follows, for example. That is, first, a material that becomes a liquid prism portion is applied to one side of the PET film. Next, it is cured by irradiating with ultraviolet rays in a state where the material to be the prism portion is sandwiched between the roll mold for forming the prism portion shape and the PET film, thereby forming the prism portion.

  Then, a binder part is formed between the formed prism parts by, for example, filling a material in which black light-absorbing particles are added into a transparent resin. Further, a light diffusion layer is formed by filling a material to be a light diffusion layer from above the binder portion and irradiating with ultraviolet rays. At this time, when the mat surface 15a shown in FIG. 3A is obtained, ultraviolet rays are irradiated in a state where the shape of the mold corresponding to the mat surface 15a is transferred.

  On the other hand, when the mat surface 15 ′ shown in FIG. 3B is obtained, an ultraviolet curable resin to which the light diffusing beads 15b ′, 15b ′, and 15b ′ are added is filled in the portion that becomes the light diffusing layer, and the ultraviolet light is irradiated. To cure.

  Next, a configuration when the optical sheet 10 of the present invention as described above is attached to the plasma television 1 as a display device, an optical path at that time, and the like will be described. FIG. 8 is a cross-sectional view focusing on a portion where the PDP 2 and the optical sheet 10 are arranged when the optical sheet 10 is arranged on the projection side of the PDP 2 and the PDP 2 and the optical sheet 10 are provided in the plasma television 1. It is. In FIG. 8, the right side of the drawing is the observer side. FIG. 9 is a diagram for explaining an optical path in which a part of FIG. 8 is enlarged.

  As shown in FIG. 8, the optical sheet 10 of the present invention is disposed on the viewer side with a gap indicated by A with respect to the PDP 2 that is an image source. On the viewer side of the pressure-sensitive adhesive layer 18, various layers having a glass plate and AR, AS, and AG functions are provided. Here, “AR” is an abbreviation for “anti-reflection” and refers to a function of suppressing the reflectance of light, and “AS” is an abbreviation for “anti-static” and means an antistatic function. “AG” is an abbreviation for “anti-glare” and can prevent glare on the prism surface.

  Next, the optical path will be described with reference to FIG. The external lights L1 and L2 incident on the prism part 12 pass through the prism part 12, pass through the gap A, and are reflected by the PDP2. The reflected lights L1 and L2 are diffusely reflected by the light diffusion layer 15 as indicated by broken lines. A part of the diffused light passes through the prism portion 12 again as indicated by L1 'and exits to the viewer side. On the other hand, the light L2 passes through the prism portion 12 again while maintaining its intensity after the reflection, and is emitted to the observer side. In the optical sheet 10 of the present invention, the light L1 is diffusely reflected as described above and the intensity in one direction is weakened. Therefore, the interference with the light L2 is reduced and the generation of moire fringes can be suppressed.

  Here, the optical sheet 10 has been described as an example, but the same description applies to the optical sheet 20 according to the above-described other embodiments and modifications, and the effect is obtained.

Examples of the optical sheet having the above configuration will be described below in more detail. However, the present invention is not limited to the scope of the examples.

As an example, an example is shown in which the effect of the diffusion layer is tested with a haze value that is increased by providing a light diffusion means. The conditions and results will be described below.
<Test sample>
As the test sample, a sample in which the pitch of the light absorbing portion, the occupied area ratio of the light absorbing portion, and the angle of the inclined surface of the light absorbing portion were changed was used. Here, the occupation area ratio of the light absorbing portion is represented by the ratio (%) of the area of the light absorbing portion appearing on the light source side surface of the optical sheet to the area of the surface.
<Haze value>
The haze value is a ratio of the diffuse transmittance to the total light transmittance of the optical sheet. The measurement method conforms to JIS K7105. In this embodiment, different haze values were used. Here, a high haze value indicates a large diffusion on the bottom surface of the light absorbing portion, and a low haze value indicates a small diffusion on the bottom surface of the light absorbing portion.
<Evaluation>
The evaluation of the occurrence of moire fringes was made by visual observation, and was good when it was good, and was bad when it was not.

  The results are described below. Table 1 shows the above-described conditions and evaluation results (light and dark stripes).

As can be seen from Table 1, no. 1-No. In any of the cases 10, the occurrence of moire fringes (bright and dark stripes) is suppressed when the haze value is greater than 18.0%. That is, the diffuse transmittance can be increased by the light diffusion means of the present invention, and moire fringes can be suppressed.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is limited to the embodiments disclosed herein. However, the invention can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and an optical sheet and a display device accompanied by such a change are also included in the technical scope of the present invention. It must be understood as a thing.

It is the figure which showed the cross section of the optical sheet of this invention concerning 1st embodiment, and represented the layer structure typically. It is the figure which expanded and showed a part of optical sheet shown in FIG. It is the figure which showed the light-diffusion layer typically. It is the figure which expanded and showed a part of optical sheet of this invention concerning another modification. It is the figure which expanded and showed a part of optical sheet of this invention concerning the further another modification. It is the figure which expanded and showed a part of optical sheet of this invention concerning 2nd embodiment and its modification. It is the figure which showed the cross section of the optical sheet of this invention concerning 3rd embodiment, and represented the layer structure typically. It is the figure which paid its attention to PDP and an optical sheet part in the scene where the optical sheet of this invention was attached to the plasma television. It is the figure which showed typically the optical path of the external light in the optical sheet periphery.

Explanation of symbols

1 Plasma TV (display device)
2 Plasma display panel 10, 20, 20 ', 30 Optical sheet 11, 21, 31 Optical function sheet layer 12, 22, 32 Prism part 13, 23 Light absorption part 14, 24 Binder part 15, 15' Light diffusion layer 15b ' Light diffusion particles (beads)
16, 26 Light-absorbing particles 17 PET film layer 23a, 23a ′ Light diffusion means

Claims (14)

On the image projection side of the plasma display panel, an optical sheet is disposed with a predetermined interval from the image projection surface of the plasma display panel, and is laminated with a plurality of layers for controlling and projecting incident light,
A prism portion having a light-transmitting property and having a substantially trapezoidal cross-sectional shape and arranged along the sheet surface;
A light absorption part disposed between the prism parts and having a wide bottom surface in a cross-sectional shape on the plasma display panel side,
A light diffusing means having a light diffusing action is provided on the wide bottom surface of the light absorbing portion ;
An optical sheet, wherein the light diffusing means is not disposed on a surface of the prism portion .   The optical sheet according to claim 1, wherein the light diffusing means depends on a shape of the bottom surface of the light absorbing portion.   The optical sheet according to claim 2, wherein the shape of the bottom surface is a polyhedron or a curved surface that is convex on the opposite side to the plasma display panel side.   The optical sheet according to claim 2, wherein the bottom surface is a mat surface.   The optical sheet according to claim 1, wherein the light diffusion means is a light diffusion layer laminated on the bottom surface of the light absorption unit.   The optical sheet according to claim 5, wherein an interface between the light absorbing portion and the light diffusion layer is a polyhedron or a curved surface that is convex on the opposite side to the plasma display panel side.   The optical sheet according to claim 5 or 6, wherein a side surface of the plasma display panel of the light diffusion layer is a mat surface.   The light diffusion layer contains light diffusing particles, and a portion of the light diffusing particles protrudes toward the plasma display panel to form the mat surface. Optical sheet.   The optical sheet according to claim 5, wherein the light diffusion layer is a white layer laminated on the bottom surface of the light absorption unit.   The optical sheet according to any one of claims 1 to 9, wherein a haze value is greater than 18.0%.   The angle formed by the slope portion extending in the sheet thickness direction from the bottom end portion of the cross-sectional shape of the light absorbing portion and the normal line of the sheet exit surface is different between one and the other in the sheet thickness direction. The optical sheet according to any one of claims 1 to 10, wherein the slope portion has the cross-sectional shape of a curved line and / or a polygonal line.   The angle formed by the slope portion extending in the sheet thickness direction from the bottom end portion of the cross-sectional shape of the light absorbing portion and the normal line of the sheet exit surface is different between one and the other in the sheet thickness direction. The optical sheet according to any one of claims 1 to 10, wherein the slope portion has the polygonal cross-sectional shape, and the formed angle is 0 to 10 degrees at any position.   The optical sheet according to claim 1, wherein the light absorbing portion contains light absorbing particles having an average particle diameter of 1 μm or more. Display device characterized by the optical sheet is provided according to any one of claims 1 to 13.

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