JP2007272209A - Light diffusion sheet for transmission type screen, and a method for manufacturing light diffusion sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion sheet which is for a transmission type screen, and which has excellent diffusion performance in such a way that an observer does not feel abnormal even when an image is observed while varying a viewing angle. <P>SOLUTION: The light diffusion sheet is equipped with: a light emitting side substrate 2 being a transparent substrate; light shielding bodies 3 with triangular shapes in cross sections arranged on one face of the light emitting side substrate 2 with an opening portion to be a light transmitting portion interposed in between; reflection lenses 7 disposed on slopes of the light shielding bodies 3 with triangular shapes in cross sections and formed with transparent resin layers with a first refractive index; a spherical refracting lens 8 formed on the opening portion 6 between adjacent light shielding bodies 3, formed with the transparent resin layer having the first refractive index; and a light incident side resin layer 5 covering the reflection lenses 7 and the spherical refracting lens 8, and formed with a transparent resin layer having a second refractive index which is higher than the first refractive index. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light diffusing sheet for a transmissive screen, and can be suitably used particularly for a rear projection display.

  In recent years, the demand for large-screen displays has increased, and among them, a rear projection display capable of easily displaying a large screen is expected.

  FIG. 9 is a structural diagram schematically showing the rear projection display 10. In FIG. 9, a lamp serving as a light source, an illumination optical system, a color separation optical system, a liquid crystal panel, a color synthesis optical system, and the like are appropriately arranged inside the optical engine 11. Light from the lamp illuminates the liquid crystal panel through the illumination optical system. The illumination light is spatially modulated by the liquid crystal panel to form an image. The image is enlarged and projected by the projection lens 12.

  The image light 14 bent and projected by the mirror 13 forms an image on the transmission screen 15. Since the image light 14 is diffused when passing through the transmissive screen 15, a color image can be observed from various angles. These elements are disposed inside the cabinet 16 and prevent the entry of external light into the apparatus.

  FIG. 10 is a schematic diagram showing the basic configuration of the transmission screen 15. The transmission screen 15 includes a Fresnel lens sheet 17 and a light diffusion sheet 1. The Fresnel lens sheet 17 is arranged on the projection side and the light diffusion sheet 1 is arranged on the observer side. The Fresnel lens sheet 17 includes a fresnel lens having a sawtooth cross section formed concentrically on the image light exit surface side.

  The light diffusing sheet 1 is composed of a light diffusing lens and a light shielding body having an opening that transmits light to the light condensing portion of the light diffusing lens in order from the image light incident surface side. In general, the light diffusing lens and the light blocking body are arranged in a stripe shape in the horizontal direction of the transmissive screen 15.

The image light 14 projected on the transmission screen 15 is refracted by the Fresnel lens sheet 17 and adjusted to parallel light 9 projected in the vertical direction with respect to the light diffusion sheet 1.
The parallel light 9 is collected by the light diffusion lens, passes through the opening of the light blocking body, and then is diffused in the left-right direction of the transmissive screen 15 to observe an image with a wide viewing angle in the left-right direction of the rear projection display 10. be able to.

  On the other hand, since the external light incident from the image light exit surface of the light diffusion sheet 1 is absorbed by the light shielding body, an image can be observed with high contrast even in a bright room. As such a light diffusing sheet 1, a light diffusing sheet 1 utilizing total reflection at a boundary surface between a high refractive index transparent resin and a light shielding body has been proposed. A three-dimensional view of this basic structure is shown in FIG. 11, and a cross-sectional view is shown in FIG. The light diffusing sheet 1 includes a high refractive index transparent resin layer 18 and a light shielding body 3 formed of a triangular low refractive index material arranged in parallel with one another on one surface of the high refractive index transparent resin layer. It is the structure provided (for example, refer patent document 1).

  In this light diffusion sheet 1, the interface of the low refractive index material in which a part of the parallel light 9 entering the high refractive index transparent resin material is exposed on the inclined surface of the light shielding body 3 serves as a reflection lens. The light can be emitted as diffused light in a direction perpendicular to the longitudinal direction, and an image can be observed with a wide viewing angle in the left-right direction.

  However, in this method, a part of the parallel light 9 incident perpendicularly to the flat surface of the high refractive index transparent resin is incident on the opening 6 of the light shield 3 and passes without being diffused. On the other hand, the remaining part of the parallel light 9 is reflected by the reflecting lens surface of the inclined surface of the light shielding body 3, and parallel reflected light whose direction is changed from the opening 6 of the light shielding body 3 according to the inclination angle of the reflecting lens is transmitted. Then emitted.

  For this reason, the viewing angle of the transmissive screen 15 is such that the output light gc having a viewing angle of 0 ° through which parallel light directly enters and passes through the opening 6 of the light shielding body 3 and the light shielding body 3 as shown in FIG. A viewing angle characteristic having three strong peaks with the output lights gs and gs ′ having a specific viewing angle totally reflected by the inclined surface appears.

  When an image projected on the transmission screen 15 having such viewing angle characteristics is viewed from all angles, there is a problem that a bright and dark portion is formed depending on the observation angle.

  An observer of the rear transmission display 10 including the light diffusion sheet 1 having the viewing angle characteristic having three luminance peaks as described above recognizes the brightness of the image on the display, and the uniformity of brightness is extremely poor. You will observe the video.

  For such a problem, a light diffusion sheet 1 to which an auxiliary diffusion layer is added has been devised. FIG. 14 shows a schematic diagram of the basic structure.

  A light incident side resin layer 5 having a high refractive index, a light shielding body 3 made of a low refractive index material having a triangular cross section and arranged in parallel on one surface of the light incident side resin layer 5; A plurality of configurations have been proposed in the basic structure of a total reflection type transmissive screen provided with a substrate 2 (see, for example, Patent Document 2).

  As a first conventional example, there is a configuration in which a diffuser layer formed of diffusion fine particles or the like is provided only in a region immediately below the opening 6 of the high refractive index transparent resin material shown in the basic structure of FIG. In this configuration, a light incident resin layer 5 having a high refractive index in which a plurality of grooves having a triangular cross section are formed in parallel on one surface is formed, and a diffuser layer is formed just below the opening 6 by a printing method or the like. Then, the groove having a triangular cross section is filled with a light-shielding material of a low refractive index material, and the light emission side substrate 2 is joined. According to this configuration, the parallel light directly incident on the opening 6 of the light shield 3 and the reflected parallel light reflected by the inclined surface of the light shield 3 are arranged directly below the opening 6 when passing through the opening 6. The diffuser layer emits the light as non-parallel light so as to improve the brightness uniformity according to the viewing angle.

As a second conventional example, a refractive structure is embedded in the upper part of the light emitting side substrate 2 located immediately below the opening 6 of the high refractive index transparent resin shown in the basic structure of FIG. In this configuration, a lenslet that diverges light is provided on at least two dispersion surfaces. In this configuration, a light incident resin layer 5 having a high refractive index in which a plurality of triangular grooves are formed in parallel on one surface is formed, a light shielding material of a low refractive index material is filled in the triangular grooves, and light is emitted. The refractive structure embedded in the side substrate 2 is disposed immediately below the opening 6 of the light incident resin layer 5 having a high refractive index, and the light emission side substrate 2 is joined. According to this configuration, the parallel light directly incident on the opening 6 of the light shield 3 and the reflected parallel light reflected from the inclined surface of the light shield 3 are non-parallel light by the diffusion structure disposed at the exit of the opening 6. And the brightness uniformity according to the viewing angle is improved.
Japanese Utility Model Publication No. 50-121753 (FIG. 5) Japanese translation of PCT publication No. 2003-504691 (FIGS. 20 and 22)

  In the configuration of the first conventional example, since the diffusion layer is formed only directly below the opening 6, the parallel light directly incident on the opening 6 of the light shield 3 and the reflection parallel reflected by the inclined surface of the light shield 3 are reflected. Since the light is emitted as non-parallel light by the diffuser layer disposed at the exit of the opening 6, the three peak gains are alleviated. However, the diffuser layer by printing or the like formed with diffusing particles or the like directly under the opening 6 has a very low light diffusion effect, which eliminates the three luminance peaks and does not eliminate the brightness of the display screen. There was a problem.

  Further, in the configuration of the second conventional example, the refractive structure is embedded in the position of the light emitting side substrate 2 directly below the opening 6, and a description of a specific structure of the diffusion structure and a description of the diffusion effect is provided. Although not made, there is a possibility that the three peak gains emitted from the opening 6 can be relatively buffered. However, in the manufacturing method, in order to accurately align the position of the refractive structure of the light emitting side substrate 2 and the opening 6 of the light incident resin layer 5 having a high refractive index, Therefore, a technique with a high degree of difficulty is required, and misalignment is likely to occur. When such misalignment occurs, there is a problem in that stable viewing angle characteristics cannot be obtained because light that has passed through the opening 6 is transmitted through the diffusion structure and light that is not transmitted. .

  The present invention solves the above-mentioned conventional problems. In the total reflection type light diffusion sheet, a spherical refractive lens is formed immediately above the opening of the light shielding body, the unevenness of the three luminance peaks is eliminated, and the viewing angle is increased. An object of the present invention is to provide a high-quality light diffusing sheet and a transmission screen using the same, in which a viewer does not feel uncomfortable even when observing an image while changing, with a simple manufacturing process.

  In order to solve the above-described conventional problems, a light diffusing sheet for a transmissive screen according to the present invention has a light emitting side substrate of a transparent substrate and an opening serving as a light transmitting portion on one surface of the light emitting side substrate. A light-shielding body having a triangular cross-section arranged in an intervening manner, a reflection lens formed of a transparent resin layer having a first refractive index provided on the inclined surface of the light-shielding body having a triangular cross-section, and an adjacent light-shielding body A spherical refractive lens of the transparent resin layer having the first refractive index formed in the opening, and a transparent resin having a second refractive index higher than the first refractive index covering the reflective lens and the spherical refractive lens. And a light incident side resin layer formed of layers.

  The method for manufacturing a light diffusing sheet for a transmissive screen according to the present invention includes a light shielding body having a triangular cross section arranged on one surface of a light emitting side substrate of a transparent substrate with an opening serving as a light transmitting portion interposed therebetween. A reflection lens is formed by a first step of forming and a transparent resin layer having a first refractive index provided on an inclined surface of the light shielding body having a triangular cross section, and the first lens is formed in the opening of the adjacent light shielding body. A second step of forming a spherical refractive lens of a transparent resin layer having a refractive index of 2nd and a second refractive index higher than the first refractive index covering the reflective lens and the spherical refractive lens after the second step. And a third step of forming a light incident side resin layer with a transparent resin layer having a refractive index.

  The light diffusing sheet for a transmissive screen according to the present invention includes a light emitting side substrate of a transparent substrate and a triangular cross section arranged on one surface of the light emitting side substrate with an opening serving as a light transmitting portion. A light shielding body having a shape; a spherical refractive lens of a transparent resin layer having a first refractive index formed in an opening of the adjacent light shielding body; and the first refractive index covering the light shielding body and the spherical refractive lens. A light incident side resin layer formed of a transparent resin layer having a higher second refractive index than the transparent resin layer having a third refractive index lower than the transparent resin layer having the second refractive index. The inclined surface of the light shielding body is formed as a reflection lens.

  According to the light diffusing sheet of the present invention and the transmissive screen using the same, the unevenness caused by the three luminance peaks that strongly appear in the total reflection type light diffusing sheet is eliminated, and observation is performed even when the image is observed while changing the viewing angle. It is possible to observe an image that the person does not feel uncomfortable. In addition, the present invention also works effectively in a vertical viewing angle expansion structure in which reflecting lenses are arranged in the vertical direction in addition to the horizontal direction, and a wide viewing angle is obtained in the vertical direction so that an observer can sit or stand. An image with a smooth change in screen brightness can be obtained.

  Embodiments of a transmissive screen diffusion sheet according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a cross-sectional structure diagram of a light diffusing sheet 1 of a transmissive screen according to a first embodiment of the present invention. As shown in FIG. 1, the light diffusion sheet 1 is mainly composed of a light emission side substrate 2, a light shielding body 3, a lens resin layer 4, and a light incident side resin layer 5.

  The light emission side substrate 2 is usually made of PMMA having a refractive index of 1.49 or MS resin (polymer of styrene and MMA) having a refractive index of about 1.52 as a base material, and has a diameter of about 10 μm in the base material. The following diffusion fine particles are dispersed at a volume ratio of about 10%. As the diffusion fine particles, beads made of MS resin having a refractive index higher than that of the base material are generally used. The refractive index of the MS resin material used for the substrate and the diffusing fine particles is changed from 1.49 to 1.59 by changing the blending ratio of MMA resin having a refractive index of about 1.49 and styrene resin having a refractive index of about 1.59. It can be adjusted within the range.

  Such diffusing fine particles have a function of uniformly diffusing and emitting incident light to the light emission side substrate 2 in all directions, and have an improvement effect such as uniform viewing angle curve and reduction of scintillation, while being transmitted. As this leads to a reduction in the rate, the optimal particle material, diameter and content are selected. Various configurations such as mixing the diffusion fine particles by changing the distribution rate in the thickness direction of the substrate, forming a sheet having a very high diffusion fine particle content, and pasting the pure transparent resin substrate are considered.

  The light-shielding body 3 uses a thermosetting, two-component curable, or EB-curable polyurethane resin as a base material, and light-absorbing black pigment fine particles are dispersed in the base material. The cross-sectional shape of the light shielding body 2 is an isosceles triangle shape having a bottom portion in close contact with the light emitting side substrate 2 and having an apex angle on the light incident surface side. Further, the light shields 3 are arranged in parallel at equal intervals with the openings 6 therebetween, and are continuous in the cross-sectional depth direction.

  A lens resin layer 4 is formed by applying a low refractive index transparent resin lower than the refractive index of the resin used in the light incident side resin layer 5 to the surface of the light shielding body 3 and the surface of the opening 6. For example, a low refractive index acrylate resin into which silicon or fluorine is introduced is used. Here, the lens resin layer 4 is a continuous low refractive index formed without a gap on both the surface of the inclined surface of the light-shielding body 3 forming the reflective layer and the surface of the opening 6 forming the spherical refractive layer. A transparent resin layer is shown. A low-refractive-index transparent layer is formed in a thin film of about 1 μm on the triangular inclined surface of the light-shielding body 3 forming the reflection layer, and functions as the reflection lens 7. Further, the opening 6 sandwiched between the legs of the cross-sectional triangle of the light blocking body 3 forming the spherical refractive layer is formed in a spherical lens shape convex in the light emitting direction, and functions as the spherical refractive lens 8.

  That is, the lens resin layer 4 at the inclined portion of the light shield 3 has a function as the reflection lens 7, and the lens resin layer 4 at the upper portion of the opening 6 has the function of the spherical refraction lens 8. The refractive lens 8 is formed from a continuous lens resin layer 4.

  The light incident side resin layer 5 is made of a high refractive index transparent resin having a higher refractive index than the low refractive index transparent resin of the lens resin layer 4, and for example, an ultraviolet curable acrylate resin or the like is used. The entire surface of the lens resin layer 4 is covered, and the light incident side is a flat surface parallel to the surface of the light emitting side substrate 2.

  In FIG. 1, the interval P is the interval between the apexes of the cross-sectional triangle shape of the light shield 3 (the center point when the top is flat) and the apex of the cross-sectional triangle shape of the adjacent light shield 3. This corresponds to a single cell on the configuration of the light diffusion sheet 1. The center line between the light shield 3 and the adjacent light shield 3 coincides with the center line of the spherical surface of the refractive lens 8, and this center line also corresponds to a symmetric line in the single cell. In this single cell, the left side from the center line is a region I, and the right side is a region II. The thin film region of the low refractive index transparent resin formed on the inclined surface of the light shield 3 in the region I is a region bi, and corresponds to the reflection lens 7 having a function of totally reflecting incident light. The thin film region of the low refractive index transparent resin formed on the inclined surface of the light shielding body 3 in the region II is a region bii, which is the same functional region as the reflective lens 7. Further, the region a is a spherical low refractive index transparent resin provided in the opening 6 and corresponds to the spherical refractive lens 8 having a function of refracting and transmitting incident light.

  In order to obtain the total reflection function of the reflection lens 7 and the light refraction function of the spherical refraction lens 8, the light shielding body 3 and the lens resin layer 4 are formed under the following conditions, respectively.

  Parallel to the substrate on which the low-refractive-index transparent resin layer and the high-refractive-index transparent resin layer are formed in close contact with each other from the high-refractive-index transparent resin layer side to the perpendicular to the low-refractive-index transparent resin surface (incident angle) When light is incident, total reflection occurs when parallel light is incident at an incident angle greater than the critical angle, and refractive transmission occurs when parallel light is incident at a critical angle or less. The critical angle is a value determined by the ratio of the refractive indexes of the low refractive index transparent resin layer and the high refractive index transparent resin layer.

  Therefore, the reflection lens 7 has an angle formed by the normal of the inclined surface of the light shielding body 3 having a triangular cross section and parallel light incident perpendicularly to the flat surface of the light incident side resin layer 5 (that is, the inclined surface of the light shielding body 3). The light incident angle on the light shielding body 3 is formed on the condition that the angle is greater than the critical angle with respect to the inclined surface of the light shield 3. For example, in the case of the refractive index 1.45 of the low refractive index transparent resin and the high refractive index transparent resin 1.55, since the critical angle is about 70 °, the light shielding body 3 is inclined so that the incident angle is 70 ° or more. A surface angle is provided. This incident angle corresponds to the angle θ formed by the bottom surface of the light shield 3 and the inclined surface. The regions bi and bii of the lens resin layer 4 configured under such conditions serve as the reflection lens 7.

  On the other hand, the spherical lens resin layer in the region a corresponding to the opening 6 is formed so that the incident angle of the parallel light incident from the high refractive index transparent resin on the light incident side substrate is less than the total reflection angle. Then, the light is refracted in the direction of condensing incident light on the surface of the spherical refractive lens 8, emitted from the opening 6, focused in the light emitting substrate 2, and then diffused.

  Next, the method for manufacturing the light diffusing sheet 1 will be described in three steps. In the first step, the light shielding body 3 is formed on the light emitting side substrate 2. A glass containing resin or spherical fine particles mixed with a transparent resin having a higher refractive index than that of the base material and formed by extrusion or the like, and the surface of the light emitting side substrate 2 having a thickness of 1 to 3 mm contains a few percent of carbon fine particles. A refractive index transparent resin is formed by arranging a plurality of light blocking bodies 3 having a triangular cross section at intervals of the openings 6 in parallel. The light-shielding body 3 is molded by being filled with resin in a mold provided with a groove having a triangular cross-section on the surface, and at the same time being polymerized and cured by overheating, chemical reaction, electron beam, or the like.

  In the second step, the lens resin layer 4 is formed. First, a liquid of a low refractive index ultraviolet curable transparent resin is quantitatively applied to the surfaces of the opening 6 and the light shielding body 3. When the coating amount is very small, when it is desired to increase the liquid coating and improve the controllability, the solvent may be removed after the UV curable transparent resin is diluted with the solvent and applied. The applied ultraviolet curable transparent liquid forms a thin film on the surface of the light shielding body 3, and a meniscus spherical surface is formed in the opening 6 between the leg portions of the light shielding body 3 due to the surface tension of the resin liquid. Next, the resin film formed by these liquid surfaces is cured by ultraviolet irradiation to form the lens resin layer 4.

  In the third step, the light incident side resin layer 5 is formed. An ultraviolet curable transparent resin having a high refractive index is applied from above the lens resin layer 4 to completely fill the irregularities of the triangular light shield 3 to form a flat surface, and then solidify by irradiation with ultraviolet rays.

  In the formation of the lens resin layer 4 in the second step, a low refractive index resin liquid is applied to form a thin film on the inclined surface of the light shielding body 3 (reflection lens 7) and a concave spherical surface on the opening 6 ( In order to perform the spherical refraction lens 8) at the same time, it is necessary that the entire area of both the inclined surface of the light shield 3 and the surface of the opening 6 be wetted by the low refractive index resin liquid. In general, the value of the contact angle is used as an indicator of the wettability between the solid and the liquid. Roughly speaking, it is expressed that the liquid repels the surface of the solid when it is higher than 90 ° and wet when it is lower than 90 °. When the liquid is put into a cylindrical tube with the bottom closed and standing vertically, if the opposing wall surfaces in the tube are parallel, a horizontal liquid surface is obtained at a contact angle of 90 °, and if it is lower than 90 °, it is formed at the contact point between the tube surface and the liquid. A concave meniscus liquid level is formed along the contact angle. Based on the same principle, the condition that the liquid surface inside the inclined surface of the opposing light shielding body 3 becomes horizontal is that the inclination angle and the contact angle of the light shielding body 3 have the same value. In order to form the contact angle, the contact angle may be lower than the inclination angle.

  FIG. 2 is a schematic view of a meniscus liquid surface formed when a liquid is put between the inclined surfaces of the opposing light shielding body 3. A spherical surface is formed along the liquid surface of the contact angle ω formed at the contact point between the inclined surface of the light shielding body 3 and the low refractive index resin liquid.

  On the other hand, in order to form a thin film of low refractive index resin liquid on the inclined surface of the light shielding body 3, it is necessary that the liquid layer be stably formed without repelling this liquid on the inclined surface. In general, it is known that any liquid having a surface tension smaller than the critical surface tension of a solid (particularly an organic compound) spreads on the surface of the solid. For example, when it is desired to wet the surface of PMMA (polymethylmethacrylate) with a liquid, a liquid having a lower surface tension than the PMMA critical surface tension of 39 dyn / cm may be used. The liquid of the ultraviolet curable resin can be obtained by selecting or adjusting a suitable material from various products such as acrylic and epoxy. In addition, in the case of a material having a very low critical surface tension such as a fluorine-based resin, it is possible to activate the surface by performing ozone ashing treatment on the solid surface, thereby making it easy to wet the liquid. This is a process of ashing the solid surface by generating oxygen radicals by irradiating ultraviolet rays to ozone at atmospheric pressure, etc., and the organic group of the organic material is cleaved to form a functional group containing oxygen. A surface state rich in activity is obtained.

  If the critical surface tension of the solid surface is increased in this way, most liquid can be wetted and spread on the solid surface, and a liquid surface layer can be formed. Thus, the inclined surface of the light shielding body 3 and the low refractive index material liquid were selected and adjusted based on the critical surface tension. In the present embodiment, as a practical method, the definition of a liquid having a critical surface tension or less is determined by maintaining a wet state on the material surface of the light blocking body 3. On the other hand, when the inclined surface of the light shielding body 3 and the opening 6 are in a wet state with the low refractive index resin material liquid, the inclined surface of the light shielding body 3 has a contact angle with the low refractive index resin material liquid equal to 0, The meniscus liquid surface shape formed in the portion 6 is a concave spherical surface having the smallest curvature radius. In this way, by using a low refractive index resin material liquid that is smaller than the critical surface tension of the inclined surface of the light shielding body 3, the thin film of the inclined surface of the light shielding body 3 as shown in FIG. 8 was formed. In the present embodiment, the film thickness of the low refractive index material on the inclined surface of the light shielding body 3 has a correlation with the viscosity of the resin liquid, and a desired film thickness can be obtained by selectively adjusting the viscosity of the resin liquid. Is possible.

  By using the lens forming method as described above, the reflection lens 7 on the surface of the light shield 3 and the ultrafine spherical refraction lens 8 in the opening 6 can be simultaneously formed without using expensive and difficult mold forming. Thus, a reliable alignment between the light shield 3 and the spherical refractive lens 8 can be achieved by self-alignment without using a special position adjusting mechanism, and therefore, a highly accurate and inexpensive manufacturing method is provided.

  Further, if the above-described ozone ashing treatment is applied to the surface layer of the lens resin layer 4, the adhesion between the lens resin layer 4 and the light incident side resin layer 5 is enhanced, and the lens resin layer 4 is highly refracted onto the uneven surface. This is very effective in improving the filling property of the resin material liquid.

  Next, the operation of the transmissive screen diffusion sheet 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the operation when the parallel light 9 incident perpendicularly to the flat surface of the light incident side resin layer 5 directly enters the spherical refractive lens 8 above the opening 6 of the light shield 3. The parallel light 9 incident on the high refractive index resin of the light incident resin substrate 5 travels straight and reaches the surface of the spherical refractive lens 8 formed of the low refractive index resin, and the light is refracted in the light condensing direction. 6, the light is condensed and diffused in the light emission side substrate 2 to become non-parallel light and is emitted from the surface of the light emission side substrate 2. The diffusion angle at this time depends on the refractive index difference between the high refractive index resin and the low refractive index resin and the radius of curvature of the spherical refractive lens 8, and the higher the refractive index difference, the larger the curvature radius. Become.

  Conventionally, light directly incident on the opening 6 passes through without being diffused or is only slightly diffused by a diffusing agent inside the light emitting side substrate 2. According to the arranged present invention, parallel light directly incident on the opening 6 can be diffused with high efficiency.

  Next, FIG. 4 illustrates an operation in the case where the parallel light 9 incident perpendicularly to the flat surface of the light incident side resin layer 5 is applied to the reflection lens 7 provided on the inclined portion of the light shield 3. . Since the reflection lens 7 is provided symmetrically and opposed to the central axis of the opening 6 of the light shield 3, only the operation of the reflection lens 7 corresponding to the region II on one side will be described here. As shown in FIG. 4, when the region bii of the reflecting lens 7 in the region II is irradiated with the incident parallel light 9, the trajectory of the light until it is emitted to the inside of the light emitting side substrate 2 is a light ray h and a light ray f. Show.

  The light beam f incident from the high refractive index transparent resin material on the reflection lens 7 in the vicinity of the vertex of the triangle of the light shield 3 is reflected by the surface of the reflection lens 7 and then enters the surface of the spherical refraction lens 8 on the region I side. The light is refracted in the condensing direction toward the axis, passes through the opening 6, and exits to the light exit side substrate 2. On the other hand, the light beam h applied to the reflection lens 7 in the vicinity of the leg portion of the light shield 3 is reflected by the surface of the reflection lens 7 and refracted greatly in the direction away from the central axis by the spherical refraction lens 8 in the region II. The light passes through the portion 6 and is emitted to the light emission side substrate 2.

  As described above, even when the incident parallel light is irradiated onto the reflection lens 7, the light (light ray f) irradiated in the vicinity of the vertex of the triangle of the light shield 3 has a lower viewing angle because the spherical lens 8 is provided. Since the light (ray h) irradiated to the vicinity of the triangular leg portion of the light shield 3 moves to the higher viewing angle side, the reflected light of the reflection lens 7 is reflected on the lower viewing angle side and the higher viewing angle side. In both cases, the light is emitted to the emission side substrate 2 with a large spread. Further, even when non-parallel light is created by using the triangular inclined surface of the light shield 3 as a curved surface, the presence of such a spherical refractive lens 8 enhances the diffusion effect and reduces the peak of the viewing angle curve. As it increases, it has the effect of further widening the base on the high viewing angle side.

  FIG. 5 shows a viewing angle curve Cb before passing through the light emitting side substrate 2 containing diffusing particles and a viewing angle curve Cf after passing through. In the curve Cb before passing through the light emitting side substrate 2, the peak gc is the gain of the light directly incident on the region a of the light shield opening 6, and the peaks gs and gs ′ are the regions bi and bii of the reflection lens 7. The gain characteristic of the light reflected by is shown. Compared with the gain characteristic without the conventional spherical refraction lens 8, when the three gain peaks are diffused greatly, as shown by the curve Cf, when passing through the light emitting side substrate 2 containing general diffusion particles, 3 One peak is eliminated. Thus, when the present invention is applied, there is no unevenness of the viewing angle curve, and a characteristic having a wide viewing angle performance can be obtained.

  As described above, by arranging the spherical refractive lens 8 in the opening 6, the parallel light 9 incident on the area of the opening 6 and the light shielding body 3 relaxes the luminance peak generated from both areas, and the gain is reduced. Since the base can be expanded, after passing through the light emitting side substrate 2 with a general diffusion function, the separation of the three luminance peaks is eliminated, and a wide base is obtained on the high viewing angle side, so that high quality light is obtained. The light diffusing sheet 1 of a transmissive screen can be provided.

  In the first embodiment, the reflection lens 7 is formed using the total reflection boundary between the transparent resin layer having the first refractive index and the transparent resin layer having the second refractive index applied to the upper surface of the light shield 3. However, the light shielding body 3 is formed of a resin material having a third refractive index lower than that of the transparent resin layer having the second refractive index, and the second refractive index is transparent on the light shielding body 3 and the spherical refractive lens in the opening. A resin layer may be formed, and a reflection lens may be formed at the boundary between the inclined surface of the light shield 3 and the transparent resin layer having the second refractive index. Here, the spherical refractive lens formed in the opening is formed by applying an appropriate amount of a transparent resin material liquid having a relatively low first refractive index of about 100 cps on the light shielding layer and the opening. The transparent resin liquid having a low viscosity slides down the inclined surface of the light shielding layer 3 and accumulates in the opening to form a concave liquid surface (concave meniscus). In addition, for the application of the transparent resin material liquid having the first refractive index, an appropriate amount can be applied to the opening by inkjet. Furthermore, the transparent resin having the first and third refractive indexes may be a material having the same refractive index.

(Embodiment 2)
Next, a light diffusing sheet 1 for a transmissive screen according to a second embodiment of the present invention will be described. In the second embodiment, the viewing angle is expanded in both the left and right and top and bottom directions. FIG. 6 shows a top view of the light diffusing sheet 1 of the transmission screen in the second embodiment of the present invention. FIG. 7 is a structural diagram of the AA ′ cut surface of FIG. FIG. 8 is a structural diagram of the BB ′ cut surface of FIG.

  In the first embodiment of the present invention, the light shielding body 3 having a triangular cross section is formed in a stripe shape that is continuous in the depth direction, whereas in the second embodiment, the light diffusion sheet of FIG. 1, in addition to the conventional arrangement in the left-right direction, the light-shielding bodies 3 are continuously formed in the vertical direction in the depth direction, and the intersections of the light-shielding bodies 3 arranged in the left-right and up-down directions It is configured to be connected with. Accordingly, the openings 6 are separated into islands when viewed from above, and the inclined surface of the light shield 3 has a bowl-like configuration in which the island-like openings 6 are surrounded on four sides. This one bowl shape becomes a single cell.

  Here, the configuration of the A-A ′ section relates to the horizontal viewing angle, and the configuration of the B-B ′ section relates to the vertical viewing angle. In the case where the horizontal viewing angle is more important than the vertical viewing angle, it can be adjusted by increasing the pitch of the light shields 3 in the vertical cross section and reducing the incident light irradiation area ratio to the reflection lens 7. The fact that the pitch Pv of the light shield 3 in FIG. 8 is larger than the pitch Ph in FIG. 7 corresponds to an example in which the horizontal viewing angle is emphasized.

  Also in the spherical refraction lens 8, by using the same lens forming process with the liquid surface as in the first embodiment, high positional accuracy of the light shielding body 3 in both the horizontal direction in FIG. 7 and the vertical direction in FIG. And can be formed easily.

  Furthermore, the configuration of the light shielding body 3 in the vertical viewing angle expansion may be a monochromatic pattern, and is not limited to the lattice type.

  Due to the structure of the spherical refraction lens 8 and the manufacturing process thereof as described above, the spherical refraction lens can be provided in both the horizontal direction and the vertical direction even in the vertical viewing angle expansion configuration in which the light shields 3 are arranged in both the horizontal direction and the vertical direction. 8 can be easily formed with high accuracy, and a continuous and smooth luminance characteristic with a wide viewing angle can be obtained by eliminating three luminance peaks in both the horizontal and vertical directions.

  In addition, since the light diffusing sheet 1 according to the present invention has a flat surface on the light incident side substrate, the light diffusing sheet 1 has a flat surface and is adhered to a reflective Fresnel lens sheet with an adhesive or the like. It is possible. By adopting such a configuration, since there is no gap between the Fresnel lens sheet and the light diffusion sheet 1 and a stable quality image can be provided, the present invention is combined with a reflective Fresnel lens sheet. It works extremely effectively. Conventionally, a light diffusion lens with concave and convex surfaces formed on the surface on the light incident side cannot be joined because an air layer is required between the Fresnel lens sheets, and a gap occurs due to the difference in the amount of warpage due to temperature changes. Had problems such as.

  In the present embodiment, a light diffusion sheet of a transmission screen of a vertical viewing angle type in which light shielding bodies 3 are arranged in a lattice shape is shown. The cross section of the light shield 3 has a substantially triangular shape, and the light shield 3 has a shape in which the pitch of the light shield 3 is 90 μm, the bottom width is 60 μm, the height is 90 μm, and the width of the opening 6 of the light shield 3 is 30 μm. The design value was set as follows.

  First, a two-component mixed urethane resin containing carbon fine particles with a volume ratio of 9% on a light emission side substrate 2 based on an acrylic resin mixed with resin beads having a particle diameter of 10 μm or less and a volume ratio of about 5%. A black liquid resin having a base material is applied.

  Next, using the transfer mold of the light shielding body 3 in which the cross-sectional triangular grooves of the light shielding body 3 are processed in the horizontal direction and the vertical direction, the pressure is applied from above to the black liquid resin before curing. Then, the black liquid resin was cured on the light emitting side substrate 2 to form a lattice-shaped light blocking body 3.

  Here, the thickness of the light emitting side substrate 2 is 2 mm, the horizontal and vertical pitches of the light shielding body 3 are 55 μm and 80 μm, respectively, and the average angle of the inclined surface θ having a triangular cross section of the light shielding body 3 is 80 ° (here, The slant surface of the light shield 3 is curved so that all the reflected light from the reflection lens 7 passes through the opening 6).

  Next, a low refractive index transparent curable resin to be the lens resin layer 4 is applied from the upper surface of the manufactured light shield 3. This time, OG134 of Epotec Co. was used as a transparent UV curable resin having a low refractive index.

  This low refractive index transparent ultraviolet curable resin was quantitatively applied to the uneven surface of the light shielding body 3 by a spray method, followed by ultraviolet curing.

  Prior to spray application, the surface of the light-shielding body 3 was subjected to ozone treatment in order to improve wettability with the application liquid. Immediately after spray coating, a thin film of coating liquid is formed on the inclined surface of the light shield 3, and a spherical refractive lens 8 is formed in the opening 6 by a concave meniscus.

  Next, a transparent UV curable resin with a high refractive index to be the light incident side resin layer 5 was applied by a spray method so that the film thickness from the top of the light shield 3 was 100 μm.

  Noland NOA-60 was used as the transparent UV curable resin having a high refractive index. After coating, UV curing was performed to complete the light diffusion screen 1.

  Both screens were evaluated by measuring the total light transmittance using a turbidimeter (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.).

  As a result, a smooth viewing angle characteristic having a peak viewing angle of 0 ° was obtained. Further, a wide β and a vertical viewing angle were obtained with a horizontal β angle (viewing angle of 1/3 peak luminance) of 37 ° and a vertical β angle of 18 °.

  A transmissive screen with the light diffusing screen produced as described above was produced, and a rear projection display was produced. As a result, a good rear projection display with a high viewing angle without uneven brightness was obtained.

  The diffusing sheet for a transmissive screen according to the present invention forms the reflection lens and the spherical refraction lens with high alignment accuracy by a simple manufacturing process, so that unevenness due to three luminance peaks that strongly appear in the total reflection type light diffusing sheet is formed. Eliminates and has a wide viewing angle and is useful as a rear projection display

The figure which shows typically the cross section of the light-diffusion sheet | seat in 1st Example of this invention. The figure for demonstrating the spherical refraction lens of the light-diffusion sheet | seat in 1st Example of this invention. Operation explanatory diagram of the light diffusion sheet in the first embodiment of the present invention Operation explanatory diagram of the reflection lens of the light diffusion sheet in the first embodiment of the present invention The figure which shows the viewing angle characteristic of the light-diffusion sheet | seat in 1st Example of this invention The top view of the light-diffusion sheet in 2nd Example of this invention A-A 'sectional view of the light diffusion sheet of the present invention shown in FIG. The book shown in FIG. 6 is a B-B ′ sectional view of the light diffusion sheet. The figure which shows the structure of the rear projection type display typically Diagram showing the structure of a transmission screen The figure which shows the three-dimensional structure of the conventional reflection type light-diffusion sheet roughly Operation explanatory diagram of conventional reflection type light diffusion sheet The figure which shows the viewing angle characteristic of the conventional reflection type light diffusion sheet The figure which shows typically the cross section of the light diffusion sheet of a 1st prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusing sheet 2 Light emission side board | substrate 3 Light-shielding body 4 Lens resin layer 5 Light incident side resin layer 6 Aperture 7 Reflective lens 8 Spherical refractive lens 9 Parallel light 10 Rear projection display 11 Optical engine 12 Projection lens 13 Mirror 14 Image Light 15 Transmission type screen 16 Cabinet 17 Fresnel lens sheet 18 High refractive index transparent resin layer

Claims (11)

A light emission side substrate of a transparent substrate;
A light shielding body having a triangular cross section arranged on one surface of the light emitting side substrate with an opening serving as a light transmitting portion interposed therebetween;
A reflective lens formed of a transparent resin layer having a first refractive index provided on an inclined surface of the light shielding body having a triangular cross section;
A spherical refractive lens of the transparent resin layer of the first refractive index formed in the opening of the adjacent light shield;
A light diffusing sheet for a transmission type screen, comprising: a light incident side resin layer formed of a transparent resin layer having a second refractive index higher than the first refractive index, covering the reflective lens and the spherical refractive lens. 2. The spherical refractive lens is formed by forming a transparent resin material having the first refractive index in an opening portion of the light shielding body having a triangular cross section adjacent thereto and having a concave surface on the light incident side. A light diffusing sheet for light transmissive screens as described in 1. The angle formed between the parallel light perpendicularly incident on the flat surface of the light incident resin layer having the second refractive index and the normal line of the inclined surface of the light shielding body is determined by the material of the lens resin layer having the first refractive index and the first refractive index. 3. The light diffusing sheet for a transmissive screen according to claim 2, wherein the light diffusing sheet has a refractive index greater than a critical angle which is a total reflection angle determined by a refractive index of the material with the light incident resin layer having a refractive index of 2. When forming a lens resin layer formed of a transparent resin layer having a first refractive index, a low refractive index resin material liquid exhibiting a surface tension smaller than the critical surface tension of the surface of the light shielding body is used. The light diffusing sheet for transmissive screen according to claim 1. During the formation of the lens resin layer formed of the transparent resin layer having the first refractive index, before applying the low refractive index resin material liquid to the surface of the light shielding body and the surface of the opening, the surface of the light shielding body and The light diffusing sheet for a transmissive screen according to claim 1, wherein the surface of the opening is subjected to ozone ashing. The light diffusing sheet for a transmissive screen according to claim 1, wherein the light emitting side substrate is formed to contain diffusing particles. A first step of forming a light-shielding body having a triangular cross section arranged on one surface of the light emitting side substrate of the transparent substrate with an opening serving as a light transmitting portion interposed therebetween;
A reflective lens is formed of a transparent resin layer having a first refractive index provided on the inclined surface of the light shielding body having a triangular cross section, and the transparent resin layer having the first refractive index is formed in an opening of the adjacent light shielding body. A second step of forming a spherical refractive lens;
A third step of forming a light incident side resin layer with a transparent resin layer having a second refractive index higher than the first refractive index, covering the reflective lens and the spherical refractive lens after the second step; A method for producing a light diffusing sheet for a transmissive screen comprising: 8. The light diffusing sheet for a transmissive screen according to claim 7, wherein in the second step, a low refractive index resin material liquid having a surface tension smaller than a critical surface tension of the surface of the light shielding body is used. Method. In the second step, the surface of the light shielding body and the surface of the opening are subjected to ozone ashing before applying the low refractive index resin material liquid to the surface of the light shielding body and the surface of the opening. Item 8. A method for producing a light diffusing sheet for a transmissive screen according to Item 7. The angle formed between the parallel light perpendicularly incident on the surface of the light incident resin layer having the second refractive index and the normal line of the inclined surface of the light shielding body is determined by the material of the lens resin layer having the first refractive index and the second refractive index. The method for producing a light diffusing sheet for a transmission type screen according to claim 7, wherein the light diffusion sheet has a refractive index larger than a critical angle which is a total reflection angle determined by a refractive index of a material with the light incident resin layer. A light emission side substrate of a transparent substrate;
A light shielding body having a triangular cross section arranged on one surface of the light emitting side substrate with an opening serving as a light transmitting portion interposed therebetween;
A spherical refractive lens of a transparent resin layer having a first refractive index formed in an opening of the adjacent light shield;
A light incident side resin layer formed of a transparent resin layer having a second refractive index higher than the first refractive index covering the light shielding body and the spherical refractive lens;
The light shielding body is formed of a resin material having a third refractive index lower than that of the transparent resin layer having the second refractive index, and the inclined surface of the light shielding body serves as a reflection lens;
A light diffusing sheet for a transmissive screen characterized by the above.

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