JP5471371B2 - Optical sheet manufacturing method, optical sheet and image display device - Google Patents

Description

  The present invention relates to a method of manufacturing an optical sheet that controls image light emitted from an image source and emits the light to an observer side, an optical sheet obtained by the method, and an image display device including the optical sheet.

  For video display devices that emit images to the viewer, such as liquid crystal displays, plasma displays, rear projection displays, organic ELs, FEDs, etc., the viewer can improve the quality of the video source and the video light from the video source. And an optical sheet having layers having various functions for emitting light.

  Several techniques relating to such an optical sheet have been disclosed so far, and for example, Patent Document 1 discloses one of them. Patent Document 1 includes a tapered waveguide (corresponding to the “prism portion” of the present invention) having an inclined surface that is disposed at an interval and reflects and diffuses incident light. The tube is disposed between the waveguides, and the display optical device includes a space portion for forming a light absorption portion (corresponding to the “light absorption portion” of the present invention) for absorbing external light and reducing the amount of reflection. (Corresponding to the “optical function sheet layer” of the present invention), wherein the light absorbing portion is (a) coated and cured along the inner wall surface of the space portion, and refracted from the side wall of the waveguide. The light-absorbing particles (corresponding to the “light-absorbing particles” of the present invention) having a different refractive index, preferably made of resin having a refractive index relatively smaller than that of the side wall of the waveguide are included. No first resin layer, and (b) is packed in the space outside the first resin layer and absorbs external light A display optical device comprising: blackish light-absorbing particles; and (c) a light-absorbing particle holder (corresponding to the “binder” of the present invention) for fixing the light-absorbing particles. An apparatus is disclosed.

Special table 2008-501128 gazette

  When obtaining an optical functional sheet layer filled with a binder in which light-absorbing particles are dispersed as in the technique described in Patent Document 1, the excess binder and light-absorbing particles are scraped after filling the binder and light-absorbing particles. Includes the process of dropping. At that time, streaky appearance defects sometimes occurred on the surface of the optical function sheet layer. When the optical functional sheet layer in which such a streak-like appearance defect occurs and another layer are laminated to form an optical sheet, the optical sheet is also adversely affected.

  Therefore, the present invention provides an optical sheet manufacturing method capable of obtaining an optical sheet having good appearance quality and capable of preventing haze rise, an optical sheet manufactured by the method, and an image display device including the sheet. Is an issue.

  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.

  Invention of Claim 1 is a manufacturing method of the optical sheet which has a some layer, Comprising: At least 1 layer is formed in parallel along the surface of a base material layer (1) among several layers. , An optical functional sheet layer (10) having a prism portion (2, 2,...) That can transmit light and a light absorbing portion (3, 3,...) That can be absorbed in parallel between the prism portions. In the cross section of the optical functional sheet layer, the light absorbing portion is formed from a resin in a groove (7) having an opening (7b) on one side and a tip (7a) on the other side. And a light-absorbing particle (5, 5,...), A prism part forming step for forming a prism part on one side of the base material layer, and a side on which the prism part is formed A particle group including a binder and light absorbing particles dispersed in the binder is supplied on the surface. The light absorption part formation which forms a light absorption part by scraping off the surplus binder and the particle group among the binder and the particle group supplied in the supply process and the supply process, and curing the binder remaining in the groove. The above-mentioned problem is solved by a method for producing an optical sheet, wherein particles larger than the width of the groove opening are contained in the particle group in an amount of 1% by volume to less than 8% by volume.

  In the present invention, “being formed in parallel along the surface of the base material layer” is not limited to being parallel in one direction on the base material layer, and is predetermined along the surface of the base material layer. It is a good concept if it is arranged so as to be arranged with the law of Therefore, for example, they may be arranged obliquely along the surface of the base material layer, or may be arranged in a staggered manner. Further, “light absorbing particles” mean particles having a light absorbing effect, and are a concept including particles scraped off in the light absorbing portion forming step in addition to the particles included in the light absorbing portion. Furthermore, the “width of the opening of the groove” means the length of the groove in a direction perpendicular to the longitudinal direction of the groove in a plane overlapping the opening of the groove. That is, in the form illustrated in FIG. 2 (a cross-sectional view showing an enlarged part of the optical function sheet layer), Wu is the width of the opening of the groove. The “particle larger than the width of the groove opening” means a particle having a longest diameter in the largest cross section of the particle longer than the width of the groove opening.

  According to a second aspect of the present invention, in the optical sheet manufacturing method according to the first aspect, the width of the front end portion (7a) of the groove (7) is 3 μm or more, and the front end portion from the opening (7b) of the groove The surface formed toward the surface has an angle of 0 degree or more and 5 degrees or less with respect to the normal direction of the sheet surface of the optical function sheet layer (10).

  In the present invention, the “width of the tip portion of the groove” means the length of the groove in a direction perpendicular to the longitudinal direction of the groove in a plane including the tip portion of the groove. That is, in the embodiment illustrated in FIG. 2 (a cross-sectional view showing an enlarged part of the optical function sheet layer), Wl is the width of the tip of the groove.

  The invention according to claim 3 is the method for producing an optical sheet according to claim 1 or 2, wherein all the particles contained in the particle group are light-absorbing particles (5, 5,...).

  According to the present invention, there are provided an optical sheet manufacturing method capable of obtaining an optical sheet having good appearance quality and preventing haze rise, an optical sheet manufactured by the method, and an image display device including the sheet. be able to.

It is the figure which showed a part of cross section roughly, paying attention to the optical function sheet | seat layer among the optical sheets of this invention. It is the figure which expanded and showed a part of optical function sheet | seat layer shown in FIG. It is the figure which showed the other example of the shape of a prism part and a light absorption part. It is a figure which shows the particle size distribution (volume) of the light absorption particle used in the Example.

  The above-described operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a diagram schematically showing a part of a cross section of the optical sheet of the present invention, focusing on the optical function sheet layer 10. In FIG. 1, some repetitive symbols may be omitted for the sake of clarity (the same applies to the following drawings). As shown in FIG. 1, the optical function sheet layer 10 includes prism portions 2, 2,... And light absorption portions 3, 3,. The optical function sheet layer 10 extends in the back / front direction of the paper while maintaining the cross section shown in FIG.

  The optical function sheet layer 10 includes prism portions 2, 2,... That are substantially trapezoidal in the cross section in the layer thickness direction, and light absorbing portions 3, 3,... Disposed between the prism portions 2, 2,. ing. FIG. 2 shows an enlarged view focusing on one light absorbing portion 3 and prism portions 2 and 2 adjacent thereto. The optical function sheet layer 10 will be described with reference to FIGS. 1 and 2.

  The prism portions 2, 2,... Are elements having a substantially trapezoidal cross section arranged such that one sheet surface side is an upper base and the other sheet surface side is a lower bottom. The prism portions 2, 2,... Are made of a light transmissive resin having a refractive index of Np. This is usually formed of, for example, urethane acrylate having a characteristic of being cured by ionizing radiation, ultraviolet rays or the like.

  The light absorbing portions 3, 3,... Are elements arranged between the prism portions 2, 2,... And having a substantially triangular cross section in the cross section shown in FIG. The surface corresponding to the base of the triangular cross section is arranged in parallel so as to face the sheet surface on the upper base side of the prism portions 2, 2. Thus, one surface of the optical function sheet layer 10 is formed by the bottom sides of the light absorbing portions 3, 3,... And the upper bases of the prism portions 2, 2,. In the cross section of the optical functional sheet layer 10, the light absorbing portions 3, 3,... Have light absorbing particles 5, 5 in a groove 7 having an opening 7 b on one side and a tip 7 a on the other side. Are filled with a binder made of a resin in which a group of particles including. Here, the width Wl of the tip portion 7a of the groove 7 is preferably 3 μm or more, and the surface of the groove 7 formed from the opening 7b toward the tip portion 7a and the sheet surface of the optical function sheet layer 10 are used. The angle θ0 formed with the line is preferably 0 ° or more and 5 ° or less. When the light absorbing portions 3, 3,... Are formed as described later, if the width Wl is too small, it becomes difficult to fill the light absorbing particles 5, 5,. This is because it is difficult to fill the grooves 7 with the light-absorbing particles 5, 5,.

  The light absorbing parts 3, 3,... Are made of a predetermined material having a refractive index Nb that is the same as or smaller than the refractive index Np of the prism parts 2, 2,. In this way, the refractive index Np of the prism portions 2, 2,... And the refractive index Nb of the light absorbing portions 3, 3,. The image light from the light source can be appropriately reflected at the interface between the light absorbing portions 3, 3,... And the prism portions 2, 2,. The difference in refractive index between Np and Nb is not particularly limited, but is preferably 0 or more and 0.06 or less.

  In addition, the light absorbing parts 3, 3,... In the optical function sheet layer 10 are configured by containing light absorbing particles 5, 5,. That is, the light absorbing particles 5, 5,... Are dispersed in the binder part 4. Thereby, in light absorption part 3, 3, ..., it injects into the inside of light absorption part 3, 3, ..., without reflecting in the interface of prism part 2,2, ... and light absorption part 3,3, ... Can be absorbed by the light absorbing particles 5, 5... Furthermore, it is possible to appropriately absorb external light from the observer side that is incident at a predetermined angle, and it is possible to improve contrast.

  At this time, the binder of the binder part 4 is made of the material having the refractive index Nb. Although what is used as a binder is not specifically limited, For example, the epoxy acrylate etc. which have the characteristics hardened | cured by ionizing radiation, an ultraviolet-ray, etc. can be mentioned. Further, the light absorbing particles 5, 5,... Preferably have an average particle size of 1 μm or more. “1 μm” is a value obtained by particle size measurement by the weight distribution method. Although the said particle | grain will not be specifically limited if it has light absorptivity, It is preferable that it is black and a commercially available particle | grain can also be used for this.

  Next, the base material layer 1 will be described. The base material layer 1 is a film layer serving as a base for forming the prism portions 2, 2,... And the light absorption portions 3, 3,. The said base material layer 1 should just contain PET as a main component, and other resin may be contained. Various additives may be added in appropriate amounts. 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).

  In addition, about the base material layer 1, the material does not necessarily need to be PET, "polyester resin", such as polybutylene terephthalate resin (PBT) or polytrimethylene terephthalate (PTT) 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.

  Next, a method for manufacturing the optical function sheet layer 10 will be described. In the method for manufacturing the optical function sheet layer 10 described above, a prism part forming step of forming the prism parts 2, 2,... On one side of the base material layer 1, and the side on which the prism parts 2, 2,. On the surface, supplying a particle group including a binder and light-absorbing particles 5, 5,... Dispersed in the binder, and a surplus of the binder and the particle group supplied in the supply process A light absorbing part forming step of forming the light absorbing parts 3, 3,... By scraping off the binder and the particle group and curing the binder remaining in the grooves 7, 7,.

  In the prism part forming step, the method of forming the prism parts 2, 2,... On one side of the base material layer 1 is not particularly limited, and a conventionally known method can be used. In the cross section of the optical function sheet layer 10, each of the grooves 7, 7,... Has an opening 7b on one side and a tip 7a on the other side. In the present invention, a particle group including particles larger than the width Wu of the opening 7b of the groove 7 is used in the supplying step. The particle group used in the supplying step only needs to include at least light absorbing particles 5, 5,... Having a size that can be filled in the grooves 7, 7,. That is, in the particle group, particles having a size that is not filled in the grooves 7, 7,... May be light absorbing particles or particles that do not have a light absorbing effect. However, it is preferable that the particle group is constituted only by light-absorbing particles (including light-absorbing particles having a size not filled in the grooves 7, 7...). Next, in the light absorption part forming step, excess binder and particle group are scraped off from the binder and particle group supplied in the supplying step. Therefore, particles larger than the width Wu of the opening 7b of the groove 7 in the particle group are scraped off at this time. After scraping off the excess binder and particle group, the grooves 7, 7,... Are filled with at least the binder and light absorbing particles smaller than the width Wu of the opening 7b of the groove 7, and the grooves 7, 7, The light absorbing portions 3, 3,... Can be formed by curing the binder filled in. Then, the optical function sheet layer 10 can be obtained by cutting out to an appropriate size.

  Conventionally, in order to sufficiently fill the grooves 7, 7,... With the light absorbing particles 5, 5,..., The light absorbing parts are used by using the light absorbing particles 5, 5,. 3, 3, ... were formed. However, in the present invention, as described above, by using the binder in which the particle group including particles larger than the width Wu of the opening 7b of the groove 7 is dispersed, the excess binder and the particle group as described above. When scraping off, it is possible to suppress the formation of streaks on the surface of the optical function sheet layer 10. This is because particles larger than the width Wu of the opening 7 b of the groove 7 are scraped off by particles larger than the width Wu of the opening 7 b of the groove 7, and the dent formed on the surface of the optical function sheet layer 10 can be reduced. This is probably because of this. When scraping off the surplus binder and particle group, if there is a part with a large indent in the surface, it will be a streak, but it can be suppressed by scratching with a uniformly large particle in the surface Conceivable. Therefore, the appearance of the optical function sheet layer 10 can be improved. Further, when the optical functional sheet layer 10 with improved appearance and another layer are laminated to obtain an optical sheet, the appearance of the optical sheet is improved. Furthermore, since the streaks (dents) on the surface of the optical function sheet layer 10 are reduced, the diffusion of light in the portion is reduced, and an effect of preventing an increase in haze can be obtained.

  However, the ratio of particles larger than the width Wu of the opening 7b of the groove 7 included in the particle group is 1% by volume or more and less than 8% by volume. If the ratio of particles larger than the width Wu of the opening 7b of the groove 7 included in the particle group is too small, it is difficult to obtain the effect of using the large particles, and particles larger than the width Wu of the opening 7b of the groove 7 If the ratio is too large, the large particles block the opening 7b of the groove 7, and the light absorbing particles 5, 5,...

  In the description of the present invention so far, the description has been given of the form in which the cross-sectional shape of the light absorbing portion is a substantially triangular shape having two linear hypotenuses, but the present invention is not limited to such a form. The other example of a light absorption part was shown in FIG. FIG. 3A shows an example in which the hypotenuse in the cross section of the light absorbing portion 3 ′ is a polygonal line, and FIG. 3B shows the hypotenuse in the cross section of the light absorbing portion 3 ″ as a curved line. An example was given. In the case shown in FIG. 3A, the hypotenuse of the light absorption unit 3 ′ (the hypotenuse of the prism units 2 ′ and 2 ′) is composed of two sides instead of one side. That is, the cross section has a polygonal oblique side. Specifically, the hypotenuse on the bottom side (upper side in the drawing) forms an angle θ1 with respect to the thickness direction of the optical function sheet. On the other hand, the hypotenuse arranged on the base material layer 1 side (the lower side in the drawing) forms an angle θ2 with respect to the thickness direction of the optical function sheet. This angle is in a relationship of θ1> θ2, and it is preferable that both are in the range of 0 ° to 5 °. A more preferable angle is greater than 0 degree and 3 degrees or less. The two hypotenuses have sizes T1 and T2 in the thickness direction of the optical function sheet, respectively. T1 and T2 are preferably the same size.

  Further, the example of FIG. 3A is an example constituted by two oblique sides, but in the cross section shown in FIG. 3A, the oblique side may be formed as a polygonal line with more sides.

  In the case shown in FIG. 3B, the inclined surface of the light absorbing portion 3 ″ (the oblique sides of the prism portions 2 ″, 2 ″,...) Has a curved shape. As described above, the hypotenuse having a substantially triangular cross-sectional shape in the light absorbing portion may be curved. Even in this case, the angle formed between the curve and the normal line of the light exit surface of the optical sheet is preferably smaller on the base material layer 1 side (lower side of the paper) than on the bottom side (upper side of the paper) of the light absorbing portion. . Furthermore, the angle is preferably in the range of 0 degree to 5 degrees in any part. A more preferable angle is greater than 0 degree and 3 degrees or less. Here, the angle formed by the curve and the normal line of the sheet light exit surface is defined by the angle formed by dividing the curve into 10 equal parts and connecting the ends to the normal line of the sheet light exit surface.

  In addition, the shape of the light absorbing portion is not limited to that of the present embodiment, and can be appropriately changed as long as it can absorb external light appropriately. This can include, for example, a case where the cross-sectional shape is rectangular.

  The optical sheet of the present invention has at least one optical functional sheet layer produced as described above, and is provided with layers having various other functions depending on the application. As a layer that can be provided in the optical sheet of the present invention, those used in conventional optical sheets can be used without any particular limitation. Specific examples include an antireflection layer, an adhesive layer, an electromagnetic wave shielding layer, a wavelength filter layer, an antiglare layer, and a hard coat layer. The order of lamination of these layers and the number of laminations are appropriately determined according to the use of the optical sheet. Hereinafter, functions of these layers will be described.

  The antireflection layer is a layer that is disposed closest to the viewer and has a function of preventing reflection of external light. According to this, it can suppress that external light reflects on the observer side surface of an optical sheet, returns to the observer side, and what is called reflection arises and it becomes difficult to see an image | video. Such an antireflection layer can be constituted by using a commercially available antireflection film.

The pressure-sensitive adhesive layer is a layer in which a pressure-sensitive adhesive is disposed. PSA (pressure sensitive adhesive) can be mentioned as an adhesive. However, the pressure-sensitive adhesive is not limited to this as long as necessary light transmittance, adhesiveness, and weather resistance can be obtained. The adhesive strength is preferably about several N / 25 mm to 20 N / 25 mm, for example. However, in the case where the pressure-sensitive adhesive layer is bonded to the glass surface, it is desirable that the thickness be several N / 25 mm to 10 N / 25 mm in consideration of re-sticking (rework) and recycling. Also, when bonded to the electromagnetic wave shielding layer, it contains an antioxidant, such as benzotriazole, -COOH, it is preferable that does not contain acid groups such as -NH _2. Further, depending on the layer structure, it is desirable to include a UV absorbent (such as benzotriazole) having an effect of absorbing ultraviolet rays in the pressure-sensitive adhesive in order to prevent deterioration of the pigment.

  As the name indicates, the electromagnetic wave shielding layer is a layer having a function of shielding electromagnetic waves. 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 or the like of the copper mesh is appropriately designed depending on the electromagnetic wave to be blocked, and examples include a pitch of about 300 μm and a line width of 12 μm.

  The wavelength filter layer is a layer having a function of filtering light having a predetermined wavelength. The wavelength to be filtered can be appropriately selected as necessary, and examples thereof include a layer that cuts a neon line emitted from a PDP and cuts infrared rays and near infrared rays.

  The antiglare layer is a layer having a function of suppressing so-called glare and is sometimes called an antiglare layer or an AG layer. A commercially available layer can be used as such an antiglare layer.

  The hard coat layer may be referred to as an HC layer. This is a layer in which a film having a function capable of imparting scratch resistance is provided in order to prevent the image display surface from being scratched.

  Since the optical sheet of the present invention includes the optical functional sheet layer having an improved appearance as described above, the appearance is improved.

  The video display device of the present invention includes the above-described optical sheet of the present invention. For example, a plasma display can be obtained by using a PDP as an image source and overlaying the optical sheet of the present invention on the PDP. Further, when combined with a light source and a liquid crystal panel, a liquid crystal display device can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

  An optical functional sheet layer having a thickness of 140 μm was formed on one surface side of the base material layer (double-sided easy-adhesive PET film, thickness 100 μm, trade name “Cosmo Shine A4300”, manufactured by Toyobo Co., Ltd.). A urethane acrylate UV curable resin having a refractive index of 1.58 was used for the prism portion provided in the optical function sheet layer. After the prism portion is formed, on the surface on which the prism portion is formed, light absorbing particles described below and a binder in which the light absorbing particles are dispersed (epoxy acrylate, viscosity at normal temperature: 4000 (mPa · s) ) At room temperature. Thereafter, surplus light absorbing particles and binder out of the supplied light absorbing particles and binder were scraped off by a blade inclined by 30 ° in the traveling direction with respect to the normal direction of the sheet surface. Thereafter, the binder remaining in the grooves between the prism portions was cured to form a light absorption portion including the binder and light absorption particles dispersed in the binder. In addition, the light absorption part was made into the form which has a substantially triangular cross section as shown in FIG. 2, or the form which has a rectangular cross section. The depth (thickness) of the groove in which the light absorbing portion is formed is 120 μm, the angle θ0 [°] of the hypotenuse in the triangular cross section with respect to the normal direction of the sheet surface of the optical function sheet layer, and the light absorbing portion is formed. The groove opening width Wu [μm] and the tip width Wl [μm] were as shown in Table 1. In the angle item of Table 1, “0” means that the light absorption part has a rectangular cross section.

  Two types of light-absorbing particles having an average particle diameter of 4 μm and 6 μm were used. The particle size distribution (volume) of the light absorbing particles used is shown in FIG. Table 1 shows the minimum particle size Rmin [μm], the average particle size Rave [μm], and the maximum particle size Rmax [μm] of the light absorbing particles used, and the opening width of the groove where the light absorbing portion is formed. The ratio [% by volume] of particles larger than Wu [μm] is shown. The average particle size “A μm” means that obtained by particle size measurement by the weight distribution method. Further, the minimum particle size means a minimum particle size whose frequency of particle size distribution is not zero, and the maximum particle size means a maximum particle size whose frequency of particle size distribution is not zero.

  When the optical functional sheet layer produced as described above is mounted on a plasma television (Panasonic, PZ700, 50 inches) and observed from various angles at a distance of 2 m (about 3 times the screen vertical dimension = 3H). It was confirmed that streaks were visible. The results are shown in Table 1. “A” means that almost no streak was confirmed, “O” means that a conspicuous streak could not be confirmed, and “x” means that a streak was generated as it was difficult to adjust. Table 1 also shows the result of confirming whether or not the light absorbing part is filled with the light absorbing particles and the binder. “◎” means that the light-absorbing particles and the binder are sufficiently filled, and “x” means that the light-absorbing particles and the binder are not sufficiently filled.

  As shown in Table 1, when using light absorbing particles containing particles larger than 1% by volume and less than 8% by volume larger than the width of the groove opening, an optical functional sheet layer having good appearance quality could be obtained. .

  Although the invention has been described with reference to embodiments that are presently practical and preferred, the invention is not limited to the embodiments disclosed herein, but is claimed. The optical sheet manufacturing method, the optical sheet, and the image display device with such changes are also within the technical scope of the present invention. It must be understood as included.

DESCRIPTION OF SYMBOLS 1 Base material layer 2 Prism part 3 Light absorption part 4 Binder part 5 Light absorption particle 7 Groove 7a Tip part 7b Opening part 10 Optical function sheet layer Wu Groove opening width Wl Groove tip width

Claims (3)

A method for producing an optical sheet having a plurality of layers,
Among the plurality of layers, at least one layer is formed in parallel along the surface of the base material layer, and a prism portion capable of transmitting light, and a light capable of absorbing light, which is arranged in parallel between the prism portions. An optical functional sheet layer having an absorbing portion,
In the cross section of the optical functional sheet layer, the light absorbing portion includes a resin binder and light absorbing particles in a groove having an opening on one side and a tip on the other side. Has been
Forming the prism portion on one side of the base material layer, a prism portion forming step;
Supplying a particle group including the binder and the light-absorbing particles dispersed in the binder on the surface on which the prism portion is formed; and
Of the binder and the particle group supplied in the supply step, scrape off the excess binder and the particle group, and form the light absorption part by curing the binder remaining in the groove, light An absorption part forming step,
The manufacturing method of the optical sheet in which the particle | grains larger than the width | variety of the opening part of the said groove | channel are contained 1 volume% or more and less than 8 volume% in the said particle group.   The width of the groove tip is 3 μm or more, and the surface formed from the groove opening toward the tip is 0 degree or more and 5 degrees with respect to the normal direction of the sheet surface of the optical function sheet layer. The manufacturing method of the optical sheet of Claim 1 which has comprised the following angles.   The method for producing an optical sheet according to claim 1, wherein all particles contained in the particle group are the light absorbing particles.

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