JP2008032811A - Optical sheet, transmission type screen and rear projection type display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet which can efficiently diffuse image light while suppressing the deterioration of gain and the deterioration of resolution and, thereby, can efficiently prevent glittering of an image. <P>SOLUTION: The optical sheet 29 is used for a transmission type screen 20. The optical sheet is provided with: a first light diffusion layer 30 comprising a first base material 31 which includes a rugged surface 32 made by arranging a plurality of unit lens shape parts 33 on the incident light side; and a second light diffusion layer 35 which is arranged on the light emission side of the first light diffusion layer and comprises a second base material 36 and a plurality of light diffusion agents 37 incorporated into the second base material. The unit lens shape parts include concave lenses. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical sheet having a light diffusing function used for a transmissive screen, and in particular, an optical sheet that can efficiently diffuse incident light and thereby efficiently suppress the occurrence of scintillation and the like. About.

  The present invention also relates to a transmission screen and a rear projection display device including such an optical sheet.

  Conventionally, a transmissive screen including an optical sheet such as a lenticular lens sheet or a Fresnel lens sheet is known. On such a transmission screen, image light is projected from a light source such as a CRT.

  In recent years, a projection tube with a small projection pupil such as a liquid crystal projector or a light valve has been used as a light source instead of a CRT. However, when a conventional transmission screen using an optical sheet is combined with such a projection tube having a small projection pupil, there is a problem that glare of an image called scintillation or speckle appears on the screen.

In order to solve such problems, it is considered effective to diffuse image light without directivity. For this reason, it has been studied to effectively solve these problems by forming irregularities on the surface of the optical sheet or dispersing a light diffusing agent (diffusible particles) in the optical sheet (for example, Patent Document 1).
Japanese Patent No. 3606862

  However, when an omnidirectional diffusion function is added to the optical sheet, another problem such as a decrease in gain and a decrease in resolution is caused.

  The present invention has been made in consideration of such points, and can efficiently diffuse image light while suppressing a decrease in gain and a decrease in resolution, thereby efficiently preventing image glare. An object is to provide an optical sheet, a transmission screen, and a rear projection display device.

  As shown in FIG. 1, the light beam LF incident on the unit diffusion element a may be once condensed by the unit diffusion element and then diffused. Here, the unit diffusing element a is an individual light diffusing agent (diffusible particle), an individual unevenness (unit lens shape part) forming a matte surface, and the like, and is a light diffusing agent in the illustrated example. . In such a case, if the next unit diffusing element (light diffusing agent in the illustrated example) b is disposed near the condensing point (position B in FIG. 1), the unit diffusing element a on the light incident side is The transmitted light beam LF is incident only on a part of the surface of the unit diffusion element b on the light output side. In this case, the light beam LF is not diffused in a wide range by the light-emitting unit diffusing element b, but can be visually recognized as a scintillation once condensed. Further, the unit diffusion element b on the light output side cannot greatly contribute to diffusing the light beam LF, but causes a decrease in gain and a decrease in resolution.

  That is, the unit diffusion element b on the light exit side is arranged at, for example, the position C or the position D in FIG. 1 so that the light beam LF incident on the unit diffusion element a on the light incident side enters the region S through which the light beam LF passes thereafter. Preferably it is. In such a case, the entire surface of the unit diffusion element b on the light output side contributes to the diffusion of transmitted light. In other words, since video light can be efficiently diffused over a wide range, video glare can be efficiently prevented without unnecessarily lowering gain or unnecessarily lowering resolution. it can. And this invention is made | formed based on such knowledge.

  A first optical sheet according to the present invention is an optical sheet for a transmissive screen, and includes a first base material including a first base material including an uneven surface formed by arranging a plurality of unit lens shape portions on a light incident side. A second light diffusion layer having a layer, a second base material disposed on the light output side of the first base material, and a plurality of light diffusing agents dispersed in the second base material, The unit lens shape part includes a concave lens. The first optical sheet according to the present invention further includes a light incident side layer disposed on a light incident side of the first light diffusion layer via a bonding layer, and the refractive index of the first substrate is determined by the bonding layer. The refractive index may be larger than the refractive index.

  A second optical sheet according to the present invention is an optical sheet for a transmissive screen, and includes a first base material including a first base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side. A second light diffusion layer having a layer, a second base material disposed on the light output side of the first base material, and a plurality of light diffusing agents dispersed in the second base material, The unit lens shape part includes a convex lens. The second optical sheet according to the present invention further includes a light incident side layer disposed on a light incident side of the first light diffusion layer via a bonding layer, and the refractive index of the first substrate is determined by the bonding layer. The refractive index may be smaller than the refractive index.

  In the second optical sheet according to the present invention, an average particle diameter of the light diffusing agent is D, and a light beam incident on one unit lens shape portion from a direction orthogonal to the sheet surface of the optical sheet is emitted from the one unit lens. Then, one light diffusing agent having a particle diameter of D and arranged on the most incident light side in the second base material may be allowed to enter the region that passes after being condensed.

In the second optical sheet according to the present invention, the average particle diameter of the light diffusing agent is D, the average arrangement pitch of the unit lens shape portions is P, the average thickness of the unit lens shape portions is Tl, If the average focal length of the unit lens shape portion is F, the average maximum length L1 from the light incident side surface of the second base material to the light incident side surface of the first base material along the direction orthogonal to the sheet surface is You may make it satisfy | fill the following formula | equation (1).
L1 ≧ ((P + D) × F / P) + Tl−D / 2 Equation (1)

Alternatively, the average particle diameter of the light diffusing agent is D, the average maximum width of the unit lens shape portion in a cross section orthogonal to the sheet surface is W, the average thickness of the unit lens shape portion is Tl, and the unit lens shape portion Is the average focal length F, the average maximum length L1 from the light incident side surface of the second base material to the light incident side surface of the first base material along the direction orthogonal to the sheet surface is expressed by the following formula ( 2) may be satisfied.
L1 ≧ ((W + D) × F / W) + Tl−D / 2 Equation (2)

  Alternatively, in the second optical sheet according to the present invention, an average particle diameter of the light diffusing agent is D, and a light beam incident on one unit lens shape portion from a direction orthogonal to the sheet surface of the optical sheet is the one unit lens. In the region through which the light passes through after being emitted from and before being condensed, one light diffusing agent having a particle diameter of D and disposed on the most outgoing light side in the second base material can enter. Good.

In the second optical sheet according to the present invention, the average particle diameter of the light diffusing agent is D, the average arrangement pitch of the unit lens shape portions is P, the average thickness of the unit lens shape portions is Tl, When the average focal length of the unit lens shape portion is F, the average maximum length L2 from the light exit side surface of the second base material to the light entrance side surface of the first base material along the direction orthogonal to the sheet surface is as follows: (3) may be satisfied.
L2 ≦ ((P−D) × F / P) + Tl + D / 2 Equation (3)

Alternatively, the average particle diameter of the light diffusing agent is D, the average maximum width of the unit lens shape portion in a cross section orthogonal to the sheet surface is W, the average thickness of the unit lens shape portion is Tl, and the unit lens shape portion Is the average focal length F, the average maximum length L2 from the light emitting side surface of the second base material to the light incident side surface of the first base material along the direction orthogonal to the sheet surface is expressed by the following formula (4 ) May be satisfied.
L2 ≦ ((W−D) × F / W) + Tl + D / 2 Equation (4)

  Further, in the first and second optical sheets according to the present invention, the first light diffusion layer may be disposed on the most incident light side.

  Furthermore, in the first and second optical sheets according to the present invention, the refractive index of the light diffusing agent may be smaller than the refractive index of the second base material.

  Further, in the first and second optical sheets according to the present invention, the first base material and the second base material are disposed adjacent to each other, and the refractive index of the first base material and the refraction of the second base material. It may be different from the rate. In this case, the refractive index of the first base material may be larger than the refractive index of the second base material.

  Alternatively, in the first and second optical sheets according to the present invention, the first base material and the second base material may be integrally formed of the same material.

  A third optical sheet according to the present invention is an optical sheet for a transmissive screen, and includes a base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side, and dispersed in the base material. A light diffusion layer having a plurality of light diffusing agents, and the unit lens shape portion includes a concave lens. The third optical sheet according to the present invention further includes a light incident side layer disposed on the light incident side of the light diffusion layer via a bonding layer, and the refractive index of the base material is higher than the refractive index of the bonding layer. May also be larger.

  In the third optical sheet according to the present invention, an average particle diameter of the light diffusing agent may be smaller than an average arrangement pitch of the unit lens shape portions.

  A fourth optical sheet according to the present invention is an optical sheet for a transmissive screen, and includes a base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side, and dispersed in the base material. A light diffusing layer having a plurality of light diffusing agents, wherein the unit lens shape portion includes a convex lens, and an average particle diameter of the light diffusing agent is smaller than an average arrangement pitch of the unit lens shape portions. It is characterized by. The fourth optical sheet according to the present invention further includes a light incident side layer disposed on the light incident side of the light diffusion layer via a bonding layer, and the refractive index of the base material is higher than the refractive index of the bonding layer. May be smaller.

  In the fourth optical sheet according to the present invention, an average particle diameter of the light diffusing agent is D, and a light beam incident on one unit lens shape portion from a direction orthogonal to the sheet surface of the optical sheet is emitted from the one unit lens. Then, one light diffusing agent having a particle diameter of D and disposed on the most light-exiting side in the substrate may be allowed to enter the region through which the light passes before being condensed.

In the fourth optical sheet according to the present invention, the average particle diameter of the light diffusing agent is D, the average arrangement pitch of the unit lens shape portions is P, the average thickness of the unit lens shape portions is Tl, When the average focal length of the unit lens shape portion is F, the average maximum thickness T of the base material may satisfy the following formula (5).
T ≦ ((P−D) × F / P) + Tl + D / 2 Equation (5)

Alternatively, the average particle diameter of the light diffusing agent is D, the average maximum width of the unit lens shape portion in a cross section orthogonal to the sheet surface is W, the average thickness of the unit lens shape portion is Tl, and the unit lens shape portion If the average focal length is F, the average maximum thickness T of the substrate may satisfy the following formula (6).
T ≦ ((W−D) × F / W) + Tl + D / 2 Equation (6)

  In the third and fourth optical sheets according to the present invention, the light diffusion layer may be disposed on the most incident light side.

  Alternatively, in the third and fourth optical sheets according to the present invention, the refractive index of the light diffusing agent may be smaller than the refractive index of the substrate.

A first transmissive screen according to the present invention includes any one of the above-described optical sheets. The second transmissive screen according to the present invention is characterized in that the first light diffusing layer or the light diffusing layer is the first. An optical sheet disposed on the light incident side is provided, and the optical sheet is disposed on the most light incident side.

  A rear projection display device according to the present invention includes any one of the transmissive screens described above.

<First Embodiment>
The first embodiment of the present invention will be described below with reference to the drawings.

  2 to 27 are diagrams for explaining embodiments of the optical sheet, the transmission screen, and the rear projection display device according to the present invention. Among these, FIGS. 2 and 3 show a rear projection display device to which the optical sheet and the transmission screen according to the present invention can be applied. 4 to 18 show a first embodiment of an optical sheet and a transmissive screen according to the present invention and a modification thereof.

  First, a first embodiment of an optical sheet and a transmissive screen, and a rear projection display device to which the optical sheet and the transmissive screen can be applied will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the rear projection type image display apparatus 10 transmits a light source 12 composed of a micro device (MD) such as an LCD or a DMD and image light projected from the light source 12 from the rear side. A transmissive screen 20 for forming an image. In the present embodiment, as shown in FIG. 2, the image light from the light source 12 is once reflected by the mirror 14 and projected onto the transmissive screen 20 and transmitted through the transmissive screen 20. However, the present invention is not limited to such an example, and image light may be directly projected from the light source 12 to the transmission screen 20 without using the mirror 14.

  As shown in FIGS. 4 and 5, the transmissive screen 20 in the present embodiment includes first to third optical sheets 21, 25, and 29. The first optical sheet 21 provided on the most incident light side (most light source side) orthogonalizes the image light enlarged and projected from the light source 12 to the sheet surface of the transmissive screen 20 (each optical sheet 21, 25, 29). A light deflection layer 22 for deflecting in the direction is provided. The second optical sheet 25 arranged on the light output side of the first optical sheet 21 expands the viewing angle for diffusing the incident video light in one direction (for example, the horizontal direction in a used state) to widen the viewing angle. A layer (directional light diffusion layer) 26 is provided. A third optical sheet 29 is provided on the light output side of the second optical sheet.

  In the illustrated example, the light deflection layer 22 is formed as a Fresnel lens portion that refracts and deflects incident light, but is not limited thereto. A known light deflection layer having the same function, for example, a light deflection layer formed as a total reflection type Fresnel lens portion that totally reflects and deflects incident light can be used. In the illustrated example, the viewing angle widening layer 26 is formed as a lenticular lens portion that mainly refracts and diffuses incident light, but is not limited thereto. A known viewing angle enlarging layer having the same function, for example, a viewing angle enlarging layer formed as a total reflection lenticular lens unit that mainly reflects and diffuses incident light can be used. Further, the light deflection layer 22 and the viewing angle widening layer 26 are not essential and can be omitted. Moreover, at least two of the first optical sheet 21, the second optical sheet 25, and the third optical sheet 29 may be integrated.

  Next, the third optical sheet 29 will be described in detail.

  As shown in FIGS. 5 and 6, the third optical sheet 29 in the present embodiment is arranged on the most incident light side, and an uneven surface 32 in which a plurality of unit lens shape portions 33 are arranged is used as the incident light side surface. The first light diffusion layer 30 having the formed first base material 31, the second base material 36 disposed adjacent to the light output side of the first base material 31, and the second base material 36 are dispersed. A second light diffusion layer 35 having a plurality of light diffusing agents (diffusible particles) 37 and a support layer 39 disposed on the light output side of the second light diffusion layer 35 are provided. Here, the light diffusing agent (diffusible particles) 37 has a substantially spherical shape.

  Among these, the support layer 39 is a layer that functions as a support substrate for increasing the rigidity of the entire transmission screen 20. As an example, the support layer 39 can be made of a resin or glass such as acrylic, acrylic / styrene copolymer, styrene, polycarbonate, acrylonitrile / styrene copolymer having a thickness of 2 mm. However, the support layer 39 can be omitted depending on the purpose.

  Next, the first light diffusion layer 30 will be described. In the present embodiment, the concavo-convex surface 32 of the first light diffusion layer 30 forms the light exit side surface of the third optical sheet 29. The unit lens shape portion 33 is provided in one direction (for example, a horizontal direction in a used state) on the light exit side surface of the third optical sheet 29 and / or in another direction orthogonal to the one direction (for example, a vertical direction in a used state). ) Can be arranged regularly or irregularly.

  Such a concavo-convex surface 32 is subjected to a blasting process on the base material by performing hairline processing on the surface of the base material by forming unevenness on the base material using a mold, for example, by various known methods. By embossing the base material, the resin containing fine particles is coated on the base material, thereby extruding a transparent resin containing fine three-dimensional crosslinked particles, and then the thermal shrinkage of the transparent resin. At the same time, the micro three-dimensional crosslinked particles can be produced by projecting on the surface of the resin. According to these manufacturing methods, for example, a unit lens shape portion formed as a convex lens, a unit lens shape portion formed as a concave lens, a unit lens shape portion having a cone shape, and a cone-shaped groove are formed. A unit lens shape portion 33 having various shapes such as a unit lens shape portion can be formed. Here, the convex lens means a lens having a function of condensing the light beam substantially at one point, and the concave lens emits the incident light beam emitted from one point as substantially parallel light. Means a lens having a function of Furthermore, according to these manufacturing methods, the unit lens shape portions 33 can be arranged by various arrangement methods such as a honeycomb arrangement and a square arrangement.

  In the example shown in FIG. 6, the unit lens shape portion 33 is formed as a concave lens 33b. The concave lens 33b has a shape provided with a concave portion corresponding to a part of an ellipse in a cross section orthogonal to the sheet surface. The unit lens shape portions 33 are regularly arranged along both one direction and the other direction on the light incident side surface of the third optical sheet 29. That is, in the example shown in FIG. 6, the concave and convex surface 32 that forms the light incident side surface of the third optical sheet 29 is formed by regularly arranging concave portions having a contour corresponding to a part of the spheroid. ing. As shown in FIG. 6, the light beam LF incident on the third optical sheet 29 is diffused two-dimensionally by the uneven surface 32 of the first base material 31.

  However, the configuration of the uneven surface 32 of the third optical sheet 29 is merely an example. For example, as shown in FIG. 7, the unit lens shape portion 33 may be formed as a convex lens 33a. The convex lens 33a has a shape corresponding to a part of an ellipse in a cross section orthogonal to the sheet surface. That is, the uneven surface 32 that forms the light incident side surface of the third optical sheet 29 may be formed by regularly arranging convex portions having a contour corresponding to a part of the spheroid. According to such a convex lens 33a, as shown in FIG. 7, the light beam LF passing through the concavo-convex surface 32 is once condensed and then diffused over a wide range.

  The term “ellipse” here is a concept including “circle”.

  Next, the second light diffusion layer 35 will be described. As the light diffusing agent 37 of the second light diffusing layer 35, a known light diffusing agent such as organic beads, inorganic beads or glass beads can be used.

  However, when the refractive index nc of the light diffusing agent 37 is larger than the refractive index nb of the second base material 36, the parallel light beam LF incident on the light diffusing agent 37 is once condensed as shown in FIG. After that, it can be spread over a wide area. On the other hand, when the refractive index nc of the light diffusing agent 37 is smaller than the refractive index nb of the second base material 36, the parallel light flux LF incident on the light diffusing agent 37 is once condensed as shown in FIG. Without being diffused, a wide range can be diffused. As described with reference to FIG. 1, the light flux that has passed through one unit diffusing element on the light incident side is disposed on the light exit side with respect to one unit diffusing element on the light incident side, in a region where the light beam subsequently passes. Preferably, only one unit diffusing element is inserted. In this case, the light diffusing function of one unit diffusing element arranged on the light exit side can be effectively exhibited. Therefore, in the case where an additional light diffusion layer including a plurality of minute unit diffusion layer elements is provided on the light output side of the second light diffusion layer 35 in the present embodiment, the light diffusion function of the additional light diffusion layer. In order to effectively exhibit the above, it is preferable that the refractive index nc of the light diffusing agent 37 is smaller than the refractive index nb of the second base material 36.

  Today, there are various known methods for specifying the refractive index value of a light diffusing agent. As a typical method for specifying the refractive index value of the light diffusing agent with high accuracy, there is a Becke line method. For the light diffusing agent dispersed in the substrate, the light diffusing agent is taken out from the substrate, the Becke line method is applied to the taken out light diffusing agent, and the refractive index value can be specified. it can.

  In order to effectively exhibit the light diffusing function of the second light diffusing layer 35, the light beam LF incident on one unit lens shape portion 33 of the first light diffusing layer 30 is in the region S through which the light LF passes thereafter. It is preferable that at least one light diffusing agent 37 enters. For this reason, it is generally preferable that the particle size of the light diffusing agent 37 in the second light diffusing layer 35 is small. Further, the average particle diameter D of the light diffusing agent 37 is smaller than the arrangement pitch P of the unit lens shape portions 33 of the first light diffusion layer 30, more strictly, the width of the lens surface of the unit lens shape portion 33. It is particularly preferable when the unit lens hair portion 33 is formed of a concave lens 33b.

  The average particle diameter D of the light diffusing agent 37 is usually in the range of 1 μm to 500 μm, and the arrangement pitch P of the unit lens shape portions 33 and the width of the lens surfaces of the unit lens shape portions 33 are usually It is in the range of 1 μm or more and 500 μm or less.

  Today, there are various known methods for specifying the average value (average particle size) of the particle size of the light diffusing agent. Among these, the laser diffraction scattering method has become the mainstream method for specifying the average particle size of the light diffusing agent because of its high performance and ease. In addition, when a three-dimensional electron microscope is used, the average particle size of the light diffusing agent can be accurately identified without removing the light diffusing agent dispersed in the substrate from the substrate. You can also

  On the other hand, the material used for the second substrate 36 is a known material such as acrylic, acrylic / styrene copolymer, styrene, polycarbonate, acrylonitrile / styrene copolymer, etc., together with the material used for the first substrate 31. Can be used.

  The third optical sheet 29 including the first light diffusion layer 30 and the second light diffusion layer 35 can be manufactured by a known manufacturing method, for example, an extrusion molding method. For example, when the third optical sheet 29 is manufactured by laminating the extruded layers, or by co-extrusion of different materials, the first base material 31 of the first light diffusion layer 30 and An interface may be formed between the second light diffusion layer 35 and the second base material 36. Thus, when an interface is formed between the first light diffusion layer 30 and the second light diffusion layer 35, the light passing through the interface is refracted at the interface.

  Here, as shown in FIGS. 6 and 7, when the refractive index nb of the second base material 36 is smaller than the refractive index na of the first base material 31, the first base material 31 and the second base material 36 The light beam LF passing through the interface is refracted at the interface and diffused over a wider range. Therefore, it is possible to easily enter one light diffusing agent 37 into the region S through which the light beam LF incident on one unit lens shape portion 33 passes thereafter, and the light diffusion function of the first light diffusion layer 30 is improved. This is convenient in terms of effective display.

  In addition, since the refractive index of a base material is high performance and easy, it is normally specified by the Abbe refractometer. As the Abbe refractometer, for example, DR-M2 manufactured by Atago Co., Ltd. can be used.

  On the other hand, the first base material 31 of the first light diffusion layer 30 and the second base material 36 of the second light diffusion layer 35 that are adjacent to each other are formed of the same material. An interface may not be formed between the base material 31 and the second base material 36 of the second light diffusion layer 35. In this case, a casting method in which the first light diffusion layer 30 and the second light diffusion layer 35 are formed by curing a fluid material in a desired shape can be used.

  When using the casting method, first, the light diffusing agent 37 having a specific gravity different from the specific gravity of the material is mixed in the fluid material, and then the light diffusing agent 37 is settled in the fluid material. Let Thereby, it will be in the state where the light-diffusion agent 37 was offset and arranged in the fuse | melted material. That is, here, the “fluid material” means that the mixed light diffusing agent 37 is contained in the material due to the difference between the specific gravity of the light diffusing agent 37 mixed in the material and the specific gravity of the material. It means a material having fluidity that can move.

  Thereafter, in this state, by curing the material that forms the first base material 31 of the first light diffusion layer 30 and the second base material 36 of the second light diffusion layer 35, the light diffusing agent 37 is offset. The second light diffusion layer 35 may be formed from the disposed portion, and the first light diffusion layer 30 may be formed from the other portion. In the first light diffusion layer 30 and the second light diffusion layer 35 obtained by such a method, as shown in FIG. 10, the first base material 31 and the second base material 36 are integrally formed from the same material. In addition, there is no interface (boundary) between the first base material 31 and the second base material 36.

  Similarly, the third optical sheet 29 in which the first base material 31 and the second base material 36 are integrally formed from the same material can be easily and inexpensively formed by coextrusion molding. When the coextrusion molding method is used, the third optical sheet 29 having three or more layers, for example, the first light diffusion layer 30, the second light diffusion layer 35, the first light diffusion layer 30, and the second light diffusion layer 35 is used. And the third optical sheet 29 in which the base material of each layer is integrally formed from the same material can be easily and inexpensively manufactured.

  Next, a method for designing the third optical sheet 29 including the first light diffusion layer 30 and the second light diffusion layer 35 in the case where the uneven surface 32 of the first light diffusion layer 30 is formed from the convex lens 33a will be described in detail. .

  When the uneven surface 32 of the first light diffusion layer 30 is formed by the convex lens 33a, the light beam LF incident on the light incident side surface (the uneven surface 32) of the first light diffusion layer 30 is once condensed and then diffused. As described above, in order to effectively exhibit the light diffusing function of each light diffusing agent 37 in the second light diffusing layer 35, the light beam LF incident on one unit lens shape portion 33 passes thereafter. It is preferable that at least one light diffusing agent 37 enters the region S. In this case, the entire surface of the light diffusing agent 37 in the second light diffusing layer 30 can contribute to further diffusing the light diffused in the first light diffusing layer 30.

  For this purpose, the passing region S after the incident light beam LF is focused on the unit lens shape portion 33 may include the light diffusing agent 37 in the second light diffusing layer 35.

  One unit lens-shaped portion 33 has an incident light flux LF from a direction orthogonal to the sheet surface of the third optical sheet 29 within the region S through which it passes after being emitted from the unit lens-shaped portion 33 and condensed. In order to allow one unit lens shape portion 33 to enter, it is preferable to design the third optical sheet 29 with reference to the light diffusing agent 37 disposed on the most incident light side in the second base material 36. . The light beam LF incident on the unit lens shape portion 33 is emitted from the unit lens shape portion 33 and condensed, and then gradually spreads over a wide range. Therefore, the light diffusing agent 33 disposed on the most incident light side in the second base material 36 closest to the unit lens shape portion 33 is passed through the subsequent passage region S of the incident light beam LF to one unit lens shape portion 33. It is preferable to enter inside. In this case, the light diffusing agent 37 can enter the passage region S of the light beam LF transmitted through any one of the unit lens shape portions 33.

  A method for designing the third optical sheet 29 including the first light diffusion layer 30 and the second light diffusion layer 35 will be described more specifically with reference to FIGS. 11 and 12.

  As shown in FIG. 11, the average arrangement pitch of the unit lens shape portions 33 is P, and the average thickness of the unit lens shape portions 33 along the direction orthogonal to the sheet surface of the third optical sheet 29 is Tl. The focal length of the shape portion 33 is F, the average particle diameter of the light diffusing agent 37 is D, and the second base material 36 (second light diffusing layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The average of the maximum length from the light incident side surface to the light incident side surface of the first base material 31 (first light diffusion layer 30) is L1. Here, the maximum length from the light incident side surface of the second base material 36 to the light incident side surface of the first base material 31 is the maximum protrusion (top portion) of the unit lens shape portion 33 from the light incident side surface of the second base material 36. ).

Assume that the light beam LF incident on one unit lens shape portion 33 is condensed and then diffused so as to include the light diffusing agent 37 disposed on the most incident light side in the second light diffusion layer 35. From the similarity of triangles, the following formula (7) is established.
P: F = D: (L1 + D / 2−F−Tl) (7)
Therefore, in order for the passage region S of the incident light beam LF to the single unit lens shape portion 33 to include the light diffusing agent 37 disposed on the most incident light side in the second light diffusing layer 35, From the light incident side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the three optical sheets 29 to the light incident side surface of the first base material 31 (first light diffusion layer 30). The average L1 of the maximum lengths of the above may satisfy the following formula (8).
L1 ≧ ((D + P) × F / P) + Tl−D / 2 Expression (8)

  Note that the focal length F of the unit lens shape portion 33 can be obtained, for example, by simulating the optical path of incident light to the unit lens shape portion 33 and actually measuring the focal length from the simulation result.

By the way, when the unit lens shape portion 33 is formed with a gap, as shown in FIG. 12, based on the average maximum width W of the unit lens shape portion 33 instead of the arrangement pitch P of the unit lens shape portion 33, The third optical sheet 29 can be designed. In this case, in order for the passing region S of the incident light beam LF to one unit lens shape portion 33 to include the light diffusing agent 37 disposed on the most incident light side in the second light diffusing layer 35, The light incident side surface of the first base material 31 (first light diffusion layer 30) from the light incident side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The average L1 of the maximum length up to the above may satisfy the following formula (9).
L1 ≧ ((D + W) × F / P) + Tl−D / 2 Formula (9)

  Here, the average maximum width W of the unit lens shape portion 33 is an average value of the maximum width of the unit lens shape portion 33 in a cross section along a direction orthogonal to the sheet surface of the third optical sheet 29. When the unit lens shape portion 33 has a shape extending along one direction, for example, like a lenticular lens, the average maximum width W of the unit lens shape portion 33 is orthogonal to the one direction, and It means the average value of the widths of the unit lens shape portions 33 in a cross section along the direction orthogonal to the sheet surface of the third optical sheet 29.

  Further, F in the equation (9) is a focal length of the unit lens shape portion 33 whose maximum width is W. Such a focal length F can be obtained, for example, by simulating the optical path of the incident light to the unit lens shape portion 33 and actually measuring the focal length from the simulation result.

  As described above, the first base material 31 (first light diffusion layer) from the light incident side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. 30) The lower limit of the average L1 of the maximum length to the light incident side surface can be set. On the other hand, the first substrate 31 (first light diffusion layer 30) enters from the light incident side surface of the second substrate 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The longer the average length L1 to the optical side, the better. For example, the first base material 31 (first light diffusion layer 30) enters from the light incident side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. If the average L1 of the maximum length to the light side surface is too long, there arises a problem that the resolution deteriorates. From this viewpoint, the first base material 31 (first light diffusion layer 30) from the light incident side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The average L1 of the maximum length to the light incident side is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less.

  By the way, in the above examination, the incident light beam LF passes through one unit lens shape portion 33 from the direction orthogonal to the sheet surface of the third optical sheet 29 after being emitted from the unit lens shape portion 33 and condensed. The third optical sheet 29 is designed so that one light diffusing agent 33 can enter the region S to be processed. On the other hand, before the light beam LF incident on one unit lens shape portion 33 is emitted from the unit lens shape portion 33 from the direction orthogonal to the sheet surface of the third optical sheet 29 and before being condensed. The third optical sheet 29 can be designed so that one light diffusing agent 37 can enter the passing region S. Such a design is very effective for the third optical sheet 29 in which the first light diffusion layer 30 is thin. In addition, the third optical sheet 29 having a small thickness of the first light diffusion layer 30 is formed by, for example, coating the second light diffusion layer 35 with a resin containing beads and the same material as the beads, or It can be formed by coating a resin on the second light diffusion layer 35 and embossing the resin.

  A design method of the third optical sheet 29 including the first light diffusion layer 30 and the second light diffusion layer 35 will be described more specifically with reference to FIGS. 13 and 14.

  In the region S through which the incident light beam LF passes from the direction orthogonal to the sheet surface of the third optical sheet 29 to one unit lens shape portion 33 before being emitted from the unit lens shape portion 33 and collected. In order to allow one light diffusing agent 33 to enter, it is preferable to design the third optical sheet 29 on the basis of the light diffusing agent 37 disposed on the most outgoing light side in the second base material 36. The light beam LF incident on the unit lens shape portion 33 is emitted from the unit lens shape portion 33 and then gradually converges toward the condensing point. Therefore, the light diffusing agent 37 disposed on the most light-emitting side in the second base material 36 that is farthest from the unit lens shape portion 33 is within the passage region S of the light beam LF emitted from one unit lens shape portion 33. Just go in.

  As shown in FIG. 13, the average arrangement pitch of the unit lens shape portions 33 is P, and the average thickness of the unit lens shape portions 33 along the direction orthogonal to the sheet surface of the third optical sheet 29 is Tl. The focal length of the shape portion 33 is F, the average particle diameter of the light diffusing agent 37 is D, and the second base material 36 (second light diffusing layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The average of the maximum length from the light exit side to the light entrance side of the first base material 31 (first light diffusion layer 30) is L2. Here, the maximum length from the light exit side surface of the second base material 36 to the light entrance side surface of the first base material 31 is from the light output side surface of the second base material 36 to the maximum protrusion (top) of the unit lens shape portion 33. It is the length of.

As shown in FIG. 13, the light beam LF incident on one unit lens shape portion 33 is then condensed so as to include a light diffusing agent 37 disposed on the most light-emitting side in the second light diffusion layer 35. Then, the following equation (10) is established from the similarity of triangles.
P: F = D: (F + Tl−L2 + D / 2) (10)
Therefore, in order to allow the passage region S of the incident light beam LF to the single unit lens shape portion 33 to include the light diffusing agent 37 disposed on the most outgoing light side in the second light diffusing layer 35, the third region is used. Maximum from the light exit side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the optical sheet 29 to the light entrance side surface of the first base material 31 (first light diffusion layer 30) The average length L2 may satisfy the following formula (11).
L2 ≦ ((P−D) × F / P) + Tl + D / 2 Expression (11)

  The focal length F of the unit lens shape portion 33 can be obtained, for example, by simulating the optical path of the incident light to the unit lens shape portion 33 and actually measuring the focal length from the simulation result.

By the way, when the unit lens shape portion 33 is formed with a gap, as shown in FIG. 14, based on the average maximum width W of the unit lens shape portion 33 instead of the arrangement pitch P of the unit lens shape portion 33, The third optical sheet 29 can be designed. In this case, in order for the passage region S of the incident light beam LF to the single unit lens shape portion 33 to include the light diffusing agent 37 disposed on the most light-emitting side in the second light diffusing layer 35, 3 From the light emission side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the optical sheet 29 to the light incident side surface of the first base material 31 (first light diffusion layer 30). What is necessary is just to make it the average L2 of maximum length satisfy | fill the following formula | equation (12).
L2 ≦ ((P−D) × F / P) + Tl + D / 2 Expression (12)

  Here, the average maximum width W of the unit lens shape portion 33 is an average value of the maximum width of the unit lens shape portion 33 in a cross section along a direction orthogonal to the sheet surface of the third optical sheet 29. When the unit lens shape portion 33 has a shape extending along one direction, for example, like a lenticular lens, the average maximum width W of the unit lens shape portion 33 is orthogonal to the one direction, and It means the average value of the widths of the unit lens shape portions 33 in a cross section along the direction orthogonal to the sheet surface of the third optical sheet 29.

  Further, F in the expression (12) is a focal length of the unit lens shape portion 33 whose maximum width is W. Such a focal length F can be obtained, for example, by simulating the optical path of the incident light to the unit lens shape portion 33 and actually measuring the focal length from the simulation result.

  As described above, the first base material 31 (first light diffusion layer 30) from the light exit side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The upper limit value of the average length L2 of the maximum length to the light incident side surface can be set. On the other hand, light incident on the first base material 31 (first light diffusion layer 30) from the light exit side surface of the second base material 36 (second light diffusion layer 35) along the direction orthogonal to the sheet surface of the third optical sheet 29. The average L2 of the maximum length to the side surface is naturally the sum of the minimum thickness of the first base material 31 (first light diffusion layer 30) and the minimum thickness of the second base material 36 (second light diffusion layer 35). That is, the average thickness Tl of the unit lens shape 33 and the average particle diameter of the light diffusing agent 37 must be equal to or greater than the sum.

  According to the present embodiment as described above, the light diffused in the first light diffusion layer 30 is efficiently diffused by the second light diffusion layer 35 disposed on the light output side of the first light diffusion layer 30. Can be made. That is, for example, by dispersing a large amount of the light diffusing agent 37 in the second light diffusing layer 35 without excessively enhancing the light diffusing function of the individual light diffusing layers 30, 35 included in the third optical sheet 29. The light diffusion function of the third optical sheet 29 as a whole can be enhanced. Accordingly, it is possible to suppress glare of the video such as scintillation while avoiding unnecessary video degradation such as excessive gain reduction and excessive contrast reduction.

  Note that various modifications can be made within the scope of the present invention with respect to the first embodiment described above.

  For example, in the above-described embodiment, an example in which one kind of light diffusing agent 37 is dispersed in the second base material 36 is shown, but the present invention is not limited thereto. In the second base material 36, a further light diffusing agent of a type different from the light diffusing agent 37 described above, for example, a light diffusing agent having an average particle diameter different from the average particle diameter of the light diffusing agent 37 described above, A light diffusing agent having a refractive index different from that of the light diffusing agent 37 described above may be further dispersed. The further light diffusing agent may be configured in the same manner as the above-described light diffusing agent, or may be configured differently. However, it is preferable that the further light diffusing agent also follows the above-described configuration, for example, the above-described design method. In the above-described embodiment, the example in which only the second light diffusion layer 35 contains the light diffusing agent 37 has been described, but the present invention is not limited thereto. For example, the first light diffusion layer 30 and the support layer 39 may contain a light diffusing agent. Furthermore, it is not necessary for one light diffusing agent 37 to be made of one kind of material. For example, a light diffusing agent (for example, JP-A-2-120702) composed of a plurality of types of materials and having partially different refractive indexes may be used.

  In the above-described embodiment, the example in which the first light diffusion layer 30 of the third optical sheet 29 is disposed adjacent to the second light diffusion layer 35 has been described, but the present invention is not limited thereto. A separate intermediate layer may be provided between the first light diffusion layer 30 and the second light diffusion layer 35 disposed on the light incident side of the first light diffusion layer 30.

  Furthermore, although the transmission type screen 20 mentioned above showed the example which has the 1st thru | or 3rd optical sheets 21, 25, 29, it is not restricted to this. The transmissive screen 20 can have any number of optical sheets equal to or greater than one. Moreover, although the example in which the first light diffusing layer 30 and the second light diffusing layer 35 are included only in the third optical sheet 29 on the most outgoing light side is shown, the present invention is not limited thereto. The first light diffusion layer 30 and the second light diffusion layer 35 may be included in an optical sheet other than the optical sheet disposed on the most light-emitting side, or may be included in a plurality of optical sheets. Good. Furthermore, although the example in which the first light diffusing layer 30 is disposed on the most incident light side of the optical sheet has been shown, the present invention is not limited thereto, and a separate light emitting side layer 43 is provided on the light incident side of the first light diffusing layer 30. It may be provided. An example of such a modification will be described below with reference to FIGS. 15 to 18, the same reference numerals are given to the same portions as those of the above-described embodiment, and the detailed description thereof is omitted.

  In the example shown in FIG. 15, the transmissive screen 20 includes first to third optical sheets 21 a, 25, and 29. Among these, the 2nd optical sheet 25 and the 3rd optical sheet 29 can be comprised the same as the corresponding component of embodiment mentioned above. On the other hand, the first optical sheet 21 a is obtained by replacing the support layer 39 of the third optical sheet 229 with the light deflection layer 22. Therefore, the first optical sheet 21 a includes the first light diffusion layer 30, the second light diffusion layer 35, and the light deflection layer 22. That is, the first light diffusion layer 30 of the first optical sheet 21 a is disposed on the most incident light side of the transmissive screen 20, and the uneven surface 32 of the first light diffusion layer 30 is the most incident light of the transmissive screen 20. Make the side.

  According to such a transmissive screen 20, the light diffused by the first light diffusion layer 30 of the third optical sheet 29 can be efficiently diffused by the second light diffusion layer 35 of the third optical sheet 29. In addition, the light diffused by the first light diffusion layer 30 of the first optical sheet 21a can be efficiently diffused by the second light diffusion layer 35 of the first optical sheet 21a. That is, for example, by dispersing a large amount of the light diffusing agent 37 in the second light diffusing layer 35 of the first optical sheet 21a, the light diffusing function of the individual light diffusing layers 30 and 35 included in the first optical sheet 21 is achieved. The light diffusion function of the first optical sheet 21a as a whole can be enhanced without being excessively enhanced. Accordingly, it is possible to suppress glare of the video such as scintillation while avoiding unnecessary video degradation such as excessive gain reduction and excessive contrast reduction.

  In addition, since the light deflection layer 22 and the viewing angle widening layer 26 (second optical sheet 25) have an appropriate thickness, the light diffused by the first optical sheet 21a is transmitted to the light output side of the first optical sheet 21. The arranged third optical sheet 29 can also be efficiently diffused. That is, the light diffusion function of the entire transmission screen 20 can be enhanced without excessively enhancing the light diffusion functions of the first optical sheet 21 and the third optical sheet 29. Thereby, glare of images, such as scintillation, can further be controlled.

  On the other hand, in the example shown in FIG. 16, the transmissive screen 20 includes a first optical sheet 21 and a second optical sheet 25a. Among these, the 1st optical sheet 21 can be comprised the same as the corresponding component of embodiment mentioned above. On the other hand, the second optical sheet 25a according to the present modification is provided with the light incident side layer 43 via the bonding layer 42 on the light incident side of the third optical sheet 29 (see FIG. 5) in the above-described embodiment. It is the comprised optical sheet. That is, in the present modification, the first light diffusion layer 30 is not disposed on the most incident light side of the optical sheet. Here, the light incident side layer 43 can be configured in the same manner as the viewing angle widening layer 26 described above, for example. However, the present invention is not limited to this, and a layer having various optical functions can be used as the light incident side layer 43.

  In such a modification, the light diffused by the first light diffusion layer 30 can be efficiently diffused by the second light diffusion layer 35 disposed on the light output side of the first light diffusion layer 30. . That is, for example, by dispersing a large amount of the light diffusing agent 37 in the second light diffusing layer 35 without excessively enhancing the light diffusing function of the individual light diffusing layers 30 and 35 included in the second optical sheet 25. The light diffusion function of the second optical sheet 25 as a whole can be enhanced. Accordingly, it is possible to suppress glare of the video such as scintillation while avoiding unnecessary video degradation such as excessive gain reduction and excessive contrast reduction.

  A known material such as an acrylic adhesive can be used as the material of the bonding layer 42 disposed on the light incident side of the first light diffusion layer 30. If the refractive index of the bonding layer 42 and the refractive index of the first base material 31 of the first light diffusion layer 30 are different, the transmitted light is refracted at the interface between the bonding layer 42 and the first light diffusion layer 30. It will be. At this time, when the unit lens shape portion 33 that forms the uneven surface 32 of the first light diffusion layer 30 is a convex lens 33 a, the refractive index of the bonding layer 42 may be larger than the refractive index of the first base material 31. preferable. In this case, as shown in FIG. 17, the light passing through the interface between the first light diffusion layer 30 and the bonding layer 42 is diffused without being collected.

  On the other hand, when the unit lens shape portion 33 that forms the concave / convex surface 32 of the first light diffusion layer 30 is a concave lens 33 b, it is preferable that the refractive index of the bonding layer 42 be smaller than the refractive index of the first base material 31. . In this case, as shown in FIG. 18, the light passing through the interface between the first light diffusion layer 30 and the bonding layer 42 is diffused without being collected.

<Second Embodiment>
Next, a second embodiment of the optical sheet and the transmissive screen will be described mainly with reference to FIGS. The same parts as those in the first embodiment described above with reference to FIGS. 2 to 18 and the modifications thereof are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 19, the transmission screen 120 in the present embodiment includes first to third optical sheets 21, 25, and 129. The first optical sheet 21 and the second optical sheet 25 can be configured in the same manner as the corresponding components in the first to third embodiments described above. Further, such a transmission screen 120 can be used as a constituent member of the rear projection display device 10 shown in FIGS. 2 and 3.

  Next, the third optical sheet 129 will be described in detail.

  As shown in FIGS. 19 and 20, the third optical sheet 129 according to the present embodiment is arranged on the most incident light side, and an uneven surface 132 formed by arranging a plurality of unit lens shape portions 133 is used as the incident light side surface. The light diffusion layer 130 having the formed base material 131 and the support layer 39 disposed on the light output side of the light diffusion layer 130 are provided. Among these, the support layer 39 can be configured in the same manner as the corresponding components in the first to third embodiments described above. In addition, a light diffusing agent 137 having a substantially spherical shape is dispersed in the base material 131 of the light diffusion layer 130.

  In the present embodiment, the uneven surface 132 of the light diffusion layer 130 forms the light incident side surface of the third optical sheet 129. The unit lens shape portion 133 is in one direction on the light incident side surface of the third optical sheet 129 (for example, the horizontal direction in the used state) and / or in the other direction orthogonal to the one direction (for example, vertical in the used state). Can be arranged regularly or irregularly along (direction).

  Such a concavo-convex surface 132 is subjected to a blasting process on the base material by performing hairline processing on the surface of the base material by forming the concavo-convex shape on the base material using a mold, for example, by various known methods. By embossing the base material, the resin containing fine particles is coated on the base material, thereby extruding a transparent resin containing fine three-dimensional crosslinked particles, and then the thermal shrinkage of the transparent resin. At the same time, the micro three-dimensional crosslinked particles can be produced by projecting on the surface of the resin. According to these manufacturing methods, for example, a unit lens shape portion formed as a convex lens, a unit lens shape portion formed as a concave lens, a unit lens shape portion having a cone shape, and a cone-shaped groove are formed. A unit lens shape portion 133 having various shapes such as a unit lens shape portion can be formed. Here, the convex lens means a lens having a function of condensing the light beam substantially at one point, and the concave lens emits the incident light beam emitted from one point as substantially parallel light. Means a lens having a function of Further, according to these manufacturing methods, the unit lens shape portions 133 can be arranged by various arrangement methods such as a honeycomb arrangement and a square arrangement.

  In the example shown in FIG. 20, the unit lens shape part 133 is formed as a concave lens 133b. The concave lens 133b has a shape in which a concave portion corresponding to a part of an ellipse is provided in a cross section orthogonal to the sheet surface. The unit lens shape portions 133 are regularly arranged along both one direction and the other direction on the light incident side surface of the third optical sheet 129. That is, in the example shown in FIG. 20, the concave and convex surface 132 that forms the light incident side surface of the third optical sheet 129 is formed by regularly arranging the concave portions having the outline corresponding to a part of the spheroid. ing. As shown in FIG. 45, the light beam LF incident on the third optical sheet 129 is diffused two-dimensionally by the uneven surface 132 of the base material 131.

  However, the configuration of the uneven surface 132 of the third optical sheet 129 is merely an example. For example, as shown in FIG. 21, the unit lens shape part 133 may be formed as a convex lens 133a. The convex lens 133a has a shape corresponding to a part of an ellipse in a cross section orthogonal to the sheet surface. That is, the uneven surface 132 that forms the light incident side surface of the third optical sheet 129 may be formed by regularly arranging convex portions having an outline corresponding to a part of the spheroid. According to such a convex lens 133a, as shown in FIG. 21, the light beam LF passing through the concavo-convex surface 132 is once condensed and then diffused over a wide range.

  The term “ellipse” here is a concept including “circle”.

  As a material used for the base material 131 of the light diffusion layer 130, a known material such as acrylic, acrylic / styrene copolymer, styrene, polycarbonate, acrylonitrile / styrene copolymer, or the like can be used. On the other hand, as the light diffusing agent 137, a known light diffusing agent such as organic beads, inorganic beads, or glass beads can be used.

  However, when the refractive index nc of the light diffusing agent 137 is larger than the refractive index na of the base material 131, as shown in FIG. 22, the light beam LF incident on the light diffusing agent 137 is once condensed and thereafter It can be diffused. On the other hand, when the refractive index nc of the light diffusing agent 137 is smaller than the refractive index na of the substrate 131, as shown in FIG. 23, the light beam LF incident on the light diffusing agent 137 is not condensed once, It can be diffused. As described with reference to FIG. 1, the light flux that has passed through one unit diffusing element on the light incident side is disposed on the light exit side with respect to one unit diffusing element on the light incident side, in a region where the light beam subsequently passes. Preferably, only one unit diffusing element is inserted. In this case, the light diffusing function of one unit diffusing element arranged on the light exit side can be effectively exhibited. Therefore, when a further light diffusion layer including a plurality of minute unit diffusion layer elements is provided on the light output side of the light diffusion layer 130 in the present embodiment, the light diffusion function of the further light diffusion layer is effective. Therefore, the refractive index nc of the light diffusing agent 137 is preferably smaller than the refractive index na of the substrate 136.

  Further, in order to effectively exhibit the light diffusing function of each light diffusing agent 137 in the light diffusing layer 130, at least within a range in which the light beam LF incident on one unit lens shape portion 133 passes thereafter. It is preferable that one light diffusing agent 137 enters. For this purpose, it is generally preferable that the particle size D of the light diffusing agent 137 is small. Typically, it is preferable that the average particle diameter D of the light diffusing agent 137 is smaller than the arrangement pitch P of the unit lens shape portions 133, more strictly, the width of the lens surface of the unit lens shape portions 133. .

  The average particle diameter D of the light diffusing agent 137 is usually in the range of 1 μm to 500 μm, and the arrangement pitch P of the unit lens shape parts 133 and the width of the lens surfaces of the unit lens shape parts 133 are usually It is in the range of 1 μm or more and 500 μm or less.

  The third optical sheet 129 including such a light diffusion layer 130 can be manufactured by a known manufacturing method such as an extrusion molding method. Further, the base material 131 of the light diffusion layer 130 and the base material of the support layer 39 which are adjacent to each other may be formed from the same material. In this case, a casting method in which the light diffusion layer 130 and the support layer 39 are formed by curing a fluid material in a desired shape can be used.

  When the casting method is used, first, a light diffusing agent 137 having a specific gravity different from the specific gravity of the material is mixed in the fluid material, and then the light diffusing agent 137 is settled in the fluid material. Let Thereby, in the material which has fluidity | liquidity, it will be in the state by which the light-diffusion agent 137 was offset and arrange | positioned. That is, here, the “material having fluidity” means that the mixed light diffusing agent 137 is contained in the material due to the difference between the specific gravity of the light diffusing agent 137 mixed in the material and the specific gravity of the material. It means a material having fluidity that can move.

  Thereafter, in this state, the material that forms the base material 131 and the support layer 39 is cured, whereby the light diffusion layer 130 is formed from the portion where the light diffusing agent 137 is offset, and from the other portions. A support layer 39 may be formed. In the light diffusion layer 130 and the support layer 39 obtained by such a method, the base material 131 of the light diffusion layer 130 and the base material of the support layer 39 are integrally formed from the same material, and the light diffusion layer 130 (base) is formed. There is no interface (boundary) between the material 131) and the support layer 39.

  Similarly, the third optical sheet 129 in which the base material 131 of the light diffusion layer 130 and the base material of the support layer 39 are integrally formed from the same material can be easily and inexpensively formed by coextrusion molding.

  Next, a method for designing the third optical sheet 129 including the light diffusion layer 130 in the case where the uneven surface 132 of the light diffusion layer 130 is formed from the convex lens 133a will be described in detail.

  When the uneven surface 132 of the light diffusion layer 130 is formed from the convex lens 133a, the light beam LF incident on the light incident side surface (uneven surface 132) of the light diffusion layer 130 is once condensed and then diffused. As described above, in order to effectively exhibit the light diffusing function of each light diffusing agent 137 in the light diffusing layer 130, the region S through which the light beam LF incident on one unit lens shape portion 133 passes thereafter. It is preferable that at least one light diffusing agent 137 is contained therein. In this case, the entire surface of the light diffusing agent 137 in the light diffusion layer 130 can contribute to diffusing the light diffused by the uneven surface 132 to a wider range. For this purpose, the light diffusion agent 137 may be included in the passing region S of the incident light beam LF to the unit lens shape portion 137 before being condensed.

  Therefore, in the present embodiment, the average particle diameter D of the light diffusing agent 137 is larger than the arrangement pitch P of the unit lens shape portions, and the light diffusing agent 137 is disposed close to the uneven surface 132. Preferably it is. Further, as indicated by a two-dot chain line in FIG. 24, it is more preferable that at least a part of the light diffusing agent 137 at least partially enters the unit lens shape portion 133 of the base material 131. Specifically, the average particle diameter D of the light diffusing agent 137 is set larger than the arrangement pitch P of the unit lens shape portions, more strictly, the width of the lens surface of the unit lens shape portion 133, and the light diffusion layer. By limiting the thickness of 130 (base material 131), the light diffusing agent 137 can be arranged in the vicinity of the uneven surface 132.

  A method for designing the third optical sheet 129 including the light diffusion layer 130 will be described more specifically with reference to FIGS. 24 and 25.

  In a region S through which the incident light beam LF passes from one unit lens shape portion 133 before it is emitted from the unit lens shape portion 133 and collected from the direction orthogonal to the sheet surface of the third optical sheet 129, In order to allow one light diffusing agent 137 to enter, it is preferable to design the third optical sheet 129 on the basis of the light diffusing agent 137 disposed on the most outgoing light side in the substrate 131. The light beam LF incident on the unit lens shape portion 133 is emitted from the unit lens shape portion 133 and then gradually converges toward the condensing point. Therefore, the light diffusing agent 137 disposed on the most light-emitting side in the base member 131 farthest from the unit lens shape portion 133 enters the passage region S of the light beam LF emitted from one unit lens shape portion 133. It is preferable that

  For this reason, as shown in FIG. 24, the incident light beam LF is emitted from the unit lens shape portion 133 to the one unit lens shape portion 133 from the direction orthogonal to the sheet surface of the third optical sheet 129 and is condensed. It is preferable that one light diffusing agent 137 arranged on the most light-emitting side in the base material 131 can enter the region S that passes through before entering.

  As shown in FIG. 24, the average arrangement pitch of the unit lens shape parts 133 is P, and the average thickness of the unit lens shape parts 133 along the direction orthogonal to the sheet surface of the third optical sheet 129 is Tl. The focal length of the shape part 133 is F, the average particle diameter of the light diffusing agent 137 is D, and the maximum thickness of the base material 131 (light diffusing layer 130) along the direction orthogonal to the sheet surface of the third optical sheet 129 is set. Let T be the average. Here, the maximum thickness of the substrate 131 (light diffusion layer 130) is the length from the light exit side surface of the substrate 131 to the maximum protrusion (top) of the unit lens shape portion 133.

Assuming that the light diffusion agent 137 arranged on the most light-emitting side in the light diffusion layer 130 is included in the passage region S of incident light to one unit lens shape portion 133, the following equation (93 ) Holds.
P: F = D: (F−T + D / 2 + Tl) (13)
Therefore, in order for the passage region S of the incident light beam LF to the light diffusing agent 137 to include the light diffusing agent 137 disposed on the most light-emitting side in the light diffusing layer 130, the sheet of the third optical sheet 129 is used. What is necessary is just to make it the average T of the maximum thickness of the base material 131 (light-diffusion layer 130) along the direction orthogonal to a surface satisfy | fill the following formula | equation (14).
T ≦ ((P−D) × F / P) + Tl + D / 2 Expression (14)

  The focal length F of the unit lens shape portion 133 can be obtained, for example, by simulating the optical path of incident light to the unit lens shape portion 133 and actually measuring the focal length from the simulation result.

By the way, when the unit lens shape part 133 is formed with a gap, as shown in FIG. 25, based on the average maximum width W of the unit lens shape part 133 instead of the arrangement pitch P of the unit lens shape part 133, The third optical sheet 129 can be designed. In this case, in order for the passing region S of the incident light beam LF to the single unit lens shape portion 133 to include the light diffusing agent 137 disposed on the most light-emitting side in the light diffusion layer 130, the third optical The average T of the maximum thicknesses of the base material 131 (light diffusion layer 130) along the direction orthogonal to the sheet surface of the sheet 129 may satisfy the following formula (15).
T ≦ ((W−D) × F / P) + Tl + D / 2 Equation (15)
Here, the average maximum width W of the unit lens shape portion 133 is an average value of the maximum widths of the unit lens shape portions 133 in a cross section along a direction orthogonal to the sheet surface of the third optical sheet 129. When the unit lens shape part 133 has a shape extending along one direction, for example, like a lenticular lens, the average maximum width W of the unit lens shape part 133 is orthogonal to the one direction, and The average value of the width of the unit lens shape part 133 in the cross section along the direction orthogonal to the sheet surface of the third optical sheet 129 is indicated.

  Further, F in the equation (15) is a focal length of the unit lens shape portion 133 whose maximum width is W. Such a focal length F can be obtained, for example, by simulating the optical path of incident light to the unit lens shape portion 133 and actually measuring the focal length from the simulation result.

  As described above, the upper limit value of the average thickness T of the base material 131 (light diffusion layer 130) along the direction orthogonal to the sheet surface of the third optical sheet 129 can be set. On the other hand, the thickness T of the base material 131 (light diffusion layer 130) along the direction orthogonal to the sheet surface of the third optical sheet 129 is naturally the average particle diameter D of the light diffusion agent 130 and the thickness of the unit lens shape portion. Must be greater than or equal to Tl.

  According to the present embodiment as described above, the light diffused by the uneven surface 132 of the substrate 131 can be efficiently diffused by the light diffusing agent 137 in the substrate 131. That is, for example, the light diffusing function of the entire light diffusing layer 130 is enhanced without excessively enhancing the light diffusing function based on the light diffusing agent 137 by, for example, dispersing a large amount of the light diffusing agent 137 in the base material 131. Can do. Accordingly, it is possible to suppress glare of the video such as scintillation while avoiding unnecessary video degradation such as excessive gain reduction and excessive contrast reduction.

  Note that various modifications can be made to the above-described fourth embodiment within the scope of the present invention.

  For example, in the above-described embodiment, an example in which one kind of light diffusing agent 137 is dispersed in the base material 131 is shown, but the present invention is not limited thereto. In the base material 131, a further light diffusing agent of a type different from the light diffusing agent 137 described above, for example, a light diffusing agent having an average particle diameter different from the average particle diameter of the light diffusing agent 137 described above, A light diffusing agent having a refractive index different from that of the light diffusing agent 137 may be further dispersed. The further light diffusing agent may be configured in the same manner as the above-described light diffusing agent, or may be configured differently. However, it is preferable that the further light diffusing agent also follows the above-described configuration, for example, the above-described design method. In the above-described embodiment, the example in which only the light diffusing layer 130 contains the light diffusing agent 137 has been described, but the present invention is not limited thereto. For example, the support layer 39 may contain a light diffusing agent. Furthermore, it is not necessary for one light diffusing agent 137 to be made of one kind of material. For example, a light diffusing agent (for example, JP-A-2-120702) composed of a plurality of types of materials and having partially different refractive indexes may be used.

  Moreover, although the transmission type screen 120 mentioned above showed the example which has the 1st thru | or 3rd optical sheet 21,25,129, it is not restricted to this. The transmissive screen 120 can have any number of optical sheets greater than or equal to one. Moreover, although the example in which the light-diffusion layer 130 is contained only in the 3rd optical sheet 129 of the most light-emitting side was shown, it is not restricted to this. The light diffusion layer 130 may be included in an optical sheet other than the optical sheet disposed on the most light-emitting side, or may be included in a plurality of optical sheets. Furthermore, although the example in which the light diffusion layer 130 is disposed on the most incident light side of the optical sheet has been shown, the present invention is not limited thereto, and a separate light incident side layer 143 is provided on the light incident side of the light diffusion layer 130. May be.

  As an example, FIGS. 26 and 26 show a modification in which a light incident side layer 143 is provided on the light incident side of the light diffusion layer 130 of the third optical sheet 129a via a bonding layer 142. FIG. Here, the light incident side layer 143 can be configured in the same manner as the viewing angle widening layer 26 described above, for example. However, the present invention is not limited to this, and a layer having various optical functions can be used as the light incident side layer 143.

  As the material of the bonding layer 142 disposed on the light incident side of the light diffusion layer 130, a known material such as an acrylic adhesive can be used. If the refractive index of the bonding layer 142 and the refractive index of the base material 131 of the light diffusion layer 130 are different, the transmitted light is refracted at the interface between the bonding layer 142 and the light diffusion layer 130.

  At this time, when the unit lens shape portion 133 forming the uneven surface 132 of the light diffusion layer 130 is a convex lens 133a, it is preferable that the refractive index of the bonding layer 142 is larger than the refractive index of the base material 131. In this case, as shown in FIG. 26, the light passing through the interface between the light diffusion layer 130 and the bonding layer 142 is diffused without being collected.

  On the other hand, when the unit lens shape part 133 that forms the uneven surface 132 of the light diffusion layer 130 is a concave lens 133 b, it is preferable that the refractive index of the bonding layer 142 be smaller than the refractive index of the base material 131. In this case, as shown in FIG. 26, the light passing through the interface between the light diffusion layer 130 and the bonding layer 142 is diffused without being collected. 25 and 26, the same reference numerals are given to the same portions as those in the above-described embodiment, the first embodiment, and the modifications thereof, and the detailed description thereof is omitted.

FIG. 1 is a diagram for explaining the relationship between a unit diffusion element arranged on the light incident side and a unit diffusion element arranged on the light emission side. FIG. 2 is a perspective view showing an embodiment of a rear projection type image display device according to the present invention. FIG. 3 is a diagram showing a schematic configuration of an optical system in the rear projection display device. FIG. 4 is a perspective view showing a first embodiment of a transmission screen according to the present invention. FIG. 5 is a diagram showing a first embodiment of a transmissive screen and an optical sheet according to the present invention. FIG. 6 is a diagram illustrating an example of the optical sheet illustrated in FIG. 5. FIG. 7 is a diagram showing another example of the optical sheet shown in FIG. FIG. 8 is a diagram for explaining the operation of the optical sheet shown in FIG. FIG. 9 is a diagram for explaining another function of the optical sheet shown in FIG. FIG. 10 is a diagram showing still another example of the optical sheet shown in FIG. FIG. 11 is a diagram for explaining a method of designing an optical sheet. FIG. 12 is a diagram for explaining another design method of the optical sheet. FIG. 13 is a diagram for explaining still another method for designing an optical sheet. FIG. 14 is a diagram for explaining still another method for designing an optical sheet. FIG. 15 is a view showing a modification of the transmission screen and the optical sheet shown in FIG. FIG. 16 is a diagram showing another modification of the transmission screen and the optical sheet shown in FIG. FIG. 17 is a diagram illustrating an example of the optical sheet illustrated in FIG. 16. FIG. 18 is a diagram showing another example of the optical sheet shown in FIG. FIG. 19 is a diagram showing a second embodiment of the transmission screen and the optical sheet according to the present invention. 20 is a diagram illustrating an example of the optical sheet illustrated in FIG. FIG. 21 is a diagram showing another example of the optical sheet shown in FIG. FIG. 22 is a diagram for explaining the operation of the optical sheet shown in FIG. FIG. 23 is a diagram for explaining the operation of the optical sheet shown in FIG. FIG. 24 is a diagram for explaining a method of designing an optical sheet. FIG. 25 is a diagram for explaining another design method of the optical sheet. FIG. 26 is a diagram showing a modification of the optical sheet shown in FIG. FIG. 27 is a view showing a modification of the optical sheet shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Back projection type display apparatus 20 Transmission type screen 21a Optical sheet 25a Optical sheet 29 Optical sheet 30 1st light-diffusion layer 31 1st base material 32 Uneven surface 33 Unit lens shape part 33a Convex lens 33b Concave lens 35 2nd light-diffusion layer 36 1st 2 base material 37 light diffusing agent 42 bonding layer 43 light incident side layer 120 transmissive screen 129 optical sheet 129a optical sheet 130 light diffusing layer 131 base material 132 uneven surface 133 unit lens shape portion 133a convex lens 133b concave lens 137 light diffusing agent 142 bonding Layer 143 Light incident side layer

Claims (28)

In an optical sheet for a transmissive screen,
A first light diffusion layer having a first base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side;
A second light diffusion layer having a second substrate disposed on the light output side of the first substrate and a plurality of light diffusing agents dispersed in the second substrate;
The optical sheet, wherein the unit lens shape part includes a concave lens. In an optical sheet for a transmissive screen,
A first light diffusion layer having a first base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side;
A second light diffusion layer having a second substrate disposed on the light output side of the first substrate and a plurality of light diffusing agents dispersed in the second substrate;
The optical sheet, wherein the unit lens shape portion includes a convex lens.   In the region where the average particle diameter of the light diffusing agent is D, and the light beam incident on one unit lens shape portion from the direction orthogonal to the sheet surface of the optical sheet passes through after being emitted from the one unit lens and condensed. 50. The optical sheet according to claim 48, wherein the particle size is D and one light diffusing agent disposed on the most incident light side in the second base material can enter. When the average particle diameter of the light diffusing agent is D, the average arrangement pitch of the unit lens shape portions is P, the average thickness of the unit lens shape portions is Tl, and the average focal length of the unit lens shape portions is F. The average maximum length L1 from the light incident side surface of the second base material to the light incident side surface of the first base material along the direction orthogonal to the sheet surface satisfies the following formula (1): The optical sheet according to claim 2 or 3.
L1 ≧ ((P + D) × F / P) + Tl−D / 2 Equation (1) The average particle diameter of the light diffusing agent is D, the average maximum width of the unit lens shape portion in a cross section orthogonal to the sheet surface is W, the average thickness of the unit lens shape portion is Tl, and the average of the unit lens shape portion When the focal length is F, the average maximum length L1 from the light incident side surface of the second base material to the light incident side surface of the first base material along the direction orthogonal to the sheet surface is expressed by the following equation (2) The optical sheet according to claim 2 or 3, wherein:
L1 ≧ ((W + D) × F / W) + Tl−D / 2 Equation (2)   The average particle diameter of the light diffusing agent is D, and the light beam incident on one unit lens shape portion from the direction orthogonal to the sheet surface of the optical sheet is emitted from the one unit lens and before being condensed. The particle size is D, and one light diffusing agent arranged on the most light-emitting side in the second base material can enter the region that passes through. Optical sheet. When the average particle diameter of the light diffusing agent is D, the average arrangement pitch of the unit lens shape portions is P, the average thickness of the unit lens shape portions is Tl, and the average focal length of the unit lens shape portions is F. The average maximum length L2 from the light exit side surface of the second base material to the light entrance side surface of the first base material along the direction orthogonal to the sheet surface satisfies the following formula (3): The optical sheet according to claim 2 or 6.
L2 ≦ ((P−D) × F / P) + Tl + D / 2 Equation (3) The average particle diameter of the light diffusing agent is D, the average maximum width of the unit lens shape portion in a cross section orthogonal to the sheet surface is W, the average thickness of the unit lens shape portion is Tl, and the average of the unit lens shape portion Assuming that the focal length is F, the average maximum length L2 from the light exit side surface of the second base material to the light entrance side surface of the first base material along the direction orthogonal to the sheet surface is expressed by the following equation (4). The optical sheet according to claim 2, wherein the optical sheet is satisfied.
L2 ≦ ((W−D) × F / W) + Tl + D / 2 Equation (4)   The optical sheet according to claim 1, wherein the first light diffusion layer is disposed on the most incident light side. A light incident side layer disposed on the light incident side of the first light diffusion layer via a bonding layer;
The optical sheet according to claim 2, wherein a refractive index of the first base material is smaller than a refractive index of the bonding layer. A light incident side layer disposed on the light incident side of the first light diffusion layer via a bonding layer;
The optical sheet according to claim 1, wherein a refractive index of the first base material is larger than a refractive index of the bonding layer.   The optical sheet according to claim 1, wherein a refractive index of the light diffusing agent is smaller than a refractive index of the second base material.   The first base material and the second base material are disposed adjacent to each other, and the refractive index of the first base material is different from the refractive index of the second base material. The optical sheet according to any one of the above.   The optical sheet according to claim 13, wherein the refractive index of the first base material is larger than the refractive index of the second base material.   The optical sheet according to any one of claims 1 to 11, wherein the first base material and the second base material are integrally formed of the same material. In an optical sheet for a transmissive screen,
A light diffusion layer having a base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side, and a plurality of light diffusing agents dispersed in the base material;
The optical sheet, wherein the unit lens shape part includes a concave lens.   The optical sheet according to claim 16, wherein an average particle diameter of the light diffusing agent is smaller than an average arrangement pitch of the unit lens shape portions. In an optical sheet for a transmissive screen,
A light diffusion layer having a base material including an uneven surface formed by arranging a plurality of unit lens shape portions on the light incident side, and a plurality of light diffusing agents dispersed in the base material;
The unit lens shape part includes a convex lens,
The optical sheet, wherein an average particle diameter of the light diffusing agent is smaller than an average arrangement pitch of the unit lens shape portions.   The average particle diameter of the light diffusing agent is D, and the light beam incident on one unit lens shape portion from the direction orthogonal to the sheet surface of the optical sheet is emitted from the one unit lens and before being condensed. 19. The optical sheet according to claim 18, wherein a particle size is D and one light diffusing agent disposed on the most light-emitting side in the base material can enter the region through which the light passes. . When the average particle diameter of the light diffusing agent is D, the average arrangement pitch of the unit lens shape portions is P, the average thickness of the unit lens shape portions is Tl, and the average focal length of the unit lens shape portions is F. The optical sheet according to claim 18 or 19, wherein the average maximum thickness T of the substrate satisfies the following formula (5).
T ≦ ((P−D) × F / P) + Tl + D / 2 Equation (5) The average particle diameter of the light diffusing agent is D, the average maximum width of the unit lens shape portion in a cross section orthogonal to the sheet surface is W, the average thickness of the unit lens shape portion is Tl, and the average of the unit lens shape portion 20. The optical sheet according to claim 18, wherein an average maximum thickness T of the base material satisfies the following formula (6), where F is a focal length.
T ≦ ((W−D) × F / W) + Tl + D / 2 Equation (6)   The optical sheet according to any one of claims 16 to 21, wherein the light diffusion layer is disposed on the most incident light side. A light incident side layer disposed on the light incident side of the light diffusion layer via a bonding layer;
The optical sheet according to any one of claims 18 to 21, wherein a refractive index of the base material is smaller than a refractive index of the bonding layer. A light incident side layer disposed on the light incident side of the light diffusion layer via a bonding layer;
The optical sheet according to claim 16 or 17, wherein a refractive index of the substrate is larger than a refractive index of the bonding layer.   The optical sheet according to any one of claims 16 to 24, wherein a refractive index of the light diffusing agent is smaller than a refractive index of the base material.   A transmissive screen comprising the optical sheet according to any one of claims 1 to 25. An optical sheet according to claim 9 or 22,
The transmissive screen, wherein the optical sheet is disposed on the most incident light side.   A rear projection display device comprising the transmission screen according to claim 26 or 27.

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