JP2006113098A - Light diffusing sheet, lens sheet and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusing sheet capable of reducing hot bars and relaxing scintillation in a screen with a projector using a high brightness light source, to provide a lenticular sheet and to provide an image display device. <P>SOLUTION: The light diffusing sheet is made by providing a light diffusing layer consisting of transparent resin, in which light diffusing fine particles are dispersed, on a light transmissive substrate, wherein the light transmissive fine particles are a mixture of organic filler such as acryl-styrene copolymer resin of globular shape and inorganic filler such as talc of indefinite shape, refractive index of organic filler falls into the range of 1.49 to 1.59 and refractive index of inorganic filler falls into the range of 1.4 to 1.7. Each of the lenticular sheet and image display device uses the light diffusing sheet. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention projects display image light generated by irradiating illumination light onto an image display element in which display pixels are defined by transmission / non-transmission, transmission / light dispersion, or selective reflection. The present invention relates to a light diffusing sheet used for a display screen of a display device. Examples of the image display element include LCD (Liquid Crystal Display Element), DMD (Digital Mirror Device: trademark of Texas Instruments), LCOS (Liquid Crystal on Silicon), and the like.

There are two types of projection (television) type television apparatuses, a reflective type (front type) and a transmissive type (rear type). As screens used for visual observation of respective images, a reflective type screen and a transmissive type are used. There are two types of screens.
In particular, a rear projection television usually transmits image light projected from a projector having a light source, an image display body, and a projection lens through a screen composed of a Fresnel lens sheet having a Fresnel lens part and a lenticular sheet having a lenticular lens part. However, the image light is configured to reach the observer.

  The screen (transmission type = rear projection screen) used in the rear projection television is required to have a directivity that is wide in the horizontal direction and slightly narrower in the vertical direction than in the horizontal direction. In general, a lenticular lens is used as the element, and a light diffusion substrate (light diffusion sheet or light diffusion layer) in which a light diffusing agent is dispersed is used as the vertical diffusion element.

As a recent rear projection television, there is a demand for providing a transmissive projection screen capable of observing bright images of the same chromaticity in a wide range. With regard to the above-mentioned transmissive projection screen that can observe bright images with the same chromaticity over a wide range, a bright white lamp as a light source has been developed, making it possible to observe bright and bright images. .
On the other hand, there is a demand for reducing the weight of the screen, and accordingly, there is a tendency to make the light diffusion substrate thinner.
JP-A-10-246916 JP 11-38512 A

  However, when a projector using a high-intensity light source is used, high-intensity light is projected, so that when a conventional screen is used, strong light tends to concentrate at the center of the screen. The intense light concentrated at the center of the screen tends to cause an undesirable phenomenon that appears as a bright horizontal stripe pattern called a hot bar or hot band (hereinafter referred to as a hot bar).

  Generally, the brightness of the display image on the screen is the largest in the normal direction with respect to the screen, and decreases as the observation angle with respect to the screen increases (out of the vertical direction). When the brightness change of the screen due to the change of the observation angle becomes remarkably large, a hot bar is generated. When this hot bar is transmitted through the lenticular lens, the unevenness of brightness is expanded in the horizontal direction, so that it is observed as a bright horizontal stripe pattern on the screen.

  In addition, when a projector using a high-intensity light source (50 lumens or more) is used as described above, high-intensity light is projected, so the light diffusing agent used as a vertical diffusing element causes glare on the screen. This causes a problem that uneven brightness occurs. This slight brightness unevenness is generally called scintillation.

Further, when the screen is made thinner, it is necessary to increase the amount of the light diffusing agent added to the conventional screen in order to maintain the diffusibility, and there is a problem that scintillation with minute glare becomes more remarkable.
Such a thin screen has a problem that it is difficult to obtain a thin diffusion of a light diffusion substrate (light diffusion sheet or light diffusion layer) and a good diffusion function as compared with a screen having a conventional thickness. .

  As described above, in a transmissive screen using an LCD or DMD as a video display, a high-luminance image is obtained by using a high-luminance light source in response to demands such as obtaining a bright image with high luminance and reducing the screen weight. Although it has been attempted to reduce the thickness of the screen for weight reduction, a hot bar with a large change in brightness due to a change in the viewing angle with respect to the screen occurs, or a slight glare occurs. Some scintillations were more noticeable and difficult to observe.

  The present invention has been made in order to solve the above-described problems, and in a screen using a projector using a high-intensity light source, a light diffusive sheet and a lenticular sheet that can reduce scintillation and reduce hot bars and images An object is to provide a display device.

  In a light diffusing sheet comprising a light diffusing layer made of a transparent resin in which light diffusing fine particles are dispersed on a light transmissive substrate, the light diffusing fine particles are a mixture of a spherical organic filler and an amorphous inorganic filler. It is a light diffusive sheet characterized by being.

The light diffusing sheet according to claim 1, wherein the organic filler is an acrylic-styrene copolymer resin, and the inorganic filler is hydrous magnesium silicate [Mg ₃ Si ₄ O ₁₀ (OH) ₂ ].

  The light diffusing sheet according to claim 1, wherein the refractive index of the organic filler is in the range of 1.49 to 1.59, and the refractive index of the inorganic filler is in the range of 1.4 to 1.7. Features.

  4. The light diffusing sheet according to claim 1, wherein the refractive index difference between the transparent resin and the light diffusing fine particles is in the range of 0 to 0.1.

  The thickness of the light diffusing sheet light diffusion layer according to any one of claims 1 to 4 is in a range of 1 to 500 µm.

The light diffusing sheet according to any one of claims 1 to 5, wherein the addition amount of the light diffusing fine particles is in the range of 1 to 65% by weight in 100% by weight of the light diffusing layer.

  The light diffusable sheet according to any one of claims 1 to 6, wherein the average particle diameter of the organic filler in the light diffusing fine particles is in the range of 1 to 30 µm, and the average particle diameter of the inorganic filler is 0.1 to 10 µm. It is characterized by being in the range of 60 μm.

  8. A lens sheet, wherein the light diffusive sheet according to claim 1 is disposed on a surface side of the lens sheet where the lens portion is not formed, or between the surface and the lens portion.

  The lens sheet according to claim 8 is either a lenticular lens sheet or a Fresnel lens sheet.

  An image in which a display image is formed by irradiating illumination light to an image display element whose display pixels are defined by transmission / non-transmission, transmission / light dispersion, or selective reflection, and projecting the display image on the display screen A display device, wherein the light diffusive sheet according to any one of claims 1 to 9 is arranged on the display screen alone or in combination with another lens sheet.

  The light diffusing sheet according to the present invention has a high luminance by using a mixture of a spherical organic filler capable of controlling the light diffusing fine particles constituting the light diffusing layer to a certain extent and an amorphous inorganic filler. In a screen using a projector using a light source, a light diffusing screen in which hot bars are reduced and scintillation is reduced can be realized.

  As shown in the cross-sectional view of FIG. 1, a light diffusing sheet 1 according to the present invention comprises a light diffusing layer 7 made of a transparent resin 5 in which light diffusing fine particles 2 are dispersed, and a translucent base material 6. The diffusible fine particles are a mixture of a spherical organic filler 3 and an amorphous inorganic filler 4.

The refractive index of the organic filler 3 and inorganic filler 4 of the light diffusing fine particles 2 used in the light diffusing sheet 1 of the present invention, and the refractive index difference between the light diffusing fine particles 2 and the transparent resin 5 satisfy the following conditions. It is preferable that the dispersibility to 5 is excellent.
Specifically, the shape of the organic filler 3 is more preferably spherical, particularly true spherical, the average particle diameter is preferably in the range of 1 to 30 μm, more preferably in the range of 10 to 15 μm, and the refractive index is 1. Specific examples of such fine particles in the range of 49 to 1.59 include fine particles of organic polymer compounds made of acrylic / styrene copolymer resin, polycarbonate, melamine resin, and the like. Control by the organic filler 3 includes, for example, control of the refractive index of the organic filler by changing the polymerization ratio of methyl methacrylate and styrene.
The inorganic filler 4 has an indefinite shape, but the average particle diameter by laser diffraction scattering method is 0.1 to 60 μm or less, more preferably about 15 to 30 μm, and the refractive index is 1.4 to 1.7. In this range, fine particles of inorganic compounds such as talc, silica, alumina, calcium carbonate, glass, bentonite, and zeolite are included.
It should be noted that the particle size can be controlled to some extent from the size of the mesh by filtering with a fine mesh at the time of generation of the irregular fine particles. Further, the average particle shape can be measured by a laser diffraction scattering method.

The addition amount of the light diffusing fine particles 2 is in the range of 1 to 65 parts by weight, more preferably in the range of 10 to 30 parts by weight with respect to 100 parts by weight of the light diffusion layer.
In addition, although the inorganic filler 4 can reduce scintillation by increasing the addition amount, since a large amount of mixing causes a decrease in luminance and color shift of the display screen, the addition amount requires attention.

  Furthermore, the refractive index difference between the transparent resin 5 and the light diffusing fine particles 2 may be controlled in the range of 0 to 1, more preferably in the range of 0 to 0.1, and still more preferably in the range of 0 to 0.02.

The transparent resin 5 that disperses the light diffusing fine particles 2 used in the light diffusing sheet 1 according to the present invention is transparent so that the refractive index difference from the light diffusing fine particles 2 satisfies the above-described conditions. It is preferable that it is excellent in adhesiveness and the adhesiveness with the translucent base material 6.
Further, it is more preferable that the light diffusion layer 7 is not easily cracked when bent and has excellent flexibility.
The material of the transparent resin 6 is not particularly limited as long as it satisfies the above conditions, and examples thereof include a plastic resin, a thermosetting resin, and an energy ray curable resin such as an ultraviolet ray and an electron beam.
Further, the thickness of the transparent resin, that is, the thickness of the light diffusion layer 7 is preferably in the range of 1 to 500 μm, more preferably in the range of 150 to 200 μm, in order to prevent a decrease in contrast.

The material of the translucent substrate 7 of the light diffusing sheet 1 according to the present invention is preferably a transparent substrate, and examples thereof include a plastic substrate, but are not particularly limited. Resins, thermosetting resins, energy ray curable resins such as ultraviolet rays and electron beams can be used.
Specific examples include polyolefin resins such as polyethylene and polypropylene, polyolefin resins such as polyethylene terephthalate, cellulose resins such as triacetyl cellulose and butyl cellulose, polystyrene, polyurethane, vinyl chloride, acrylic resins, polycarbonate resins, and polyester resins. It is done.
Although there is no restriction | limiting in particular in the thickness of the translucent base material 7, From the point of the weight reduction of the light diffusable sheet | seat 1, and the cost reduction, Preferably it is the range of 10-5000 micrometers, More preferably, the range of 1000-2500 micrometers is good.

  In addition, various treatments can be applied to the surface of the translucent substrate 6 in order to improve the adhesion with the light diffusion layer 7. Examples of the treatment method include corona treatment, anchor treatment, saponification treatment, treatment with a silane coupling agent, and the like.

  Next, the method for producing the light diffusive sheet 1 of the present invention is not particularly limited. For example, a method of extruding in two layers while each of a pellet of a diffusing agent and a pellet of a transparent resin is thermally melted by an extruder. In addition, there are an injection molding method, a method of adding a diffusing agent to a resin having adhesiveness, and transferring it to a substrate.

  In the light diffusing sheet 1 of the present invention, a light diffusing layer 7 is formed on a transparent substrate 6. As shown in FIG. 3, (a) a lenticular sheet 9 having a lenticular lens portion 8, and (b) a Fresnel lens. The light diffusion layer 7 may be formed directly on the Fresnel sheet 11 having the portion 10 or the lens sheet 12 such as a prism sheet (not shown) on which a prism having a light blocking function is formed by a total reflection method.

Hereinafter, the light diffusing sheet 1 according to the present invention will be described based on an embodiment in which the light diffusing sheet 1 is combined with a lens sheet 12 and used for a transmission type screen 13.
First, as shown in the image display device 15 of FIG. 2, the video display body 14 uses a liquid crystal projector, and the projected video light is reflected by the reflecting mirrors 16 and 17 and is incident on the transmissive screen 13. Yes.
The transmissive projection screen 13 shown in FIG. 4 is composed of a Fresnel lens sheet 11 from the light source side and a lenticular sheet 9 formed with the light diffusive sheet 1 according to the present invention on the observation side.

Example 1
The transparent resin of the light diffusing layer has a refractive index different from that of the light diffusing fine particles. The transparent resin has a refractive index of 1.53, and the material is acrylic or styrene copolymer. The fine particles have a spherical organic filler which is an organic polymer compound made of an acrylic-styrene copolymer resin having a refractive index of 1.49 and an average particle diameter of 20 μm, a refractive index of 1.56 and an average particle diameter of 30 μm. It consists of an irregularly shaped inorganic filler, which is an inorganic compound composed of talc mainly composed of magnesium silicate, and these are mixed based on the addition amount shown in Table 1 below. A light diffusing layer having a thickness of 1500 μm was formed on a light transmissive substrate made of copolymer by extrusion molding to obtain a light diffusing sheet.
These light diffusing sheets were combined on the front side of the observation side lenticular sheet of the transmission type projection screen.
This was incorporated into a rear projection television, and an image was projected, and it was visually evaluated whether the scintillation changed to a certain degree. In the evaluation, the haze value of the screen surface was made constant, and the front brightness of the screen was made equal.
The evaluation results are shown in Table 1.
In the table, “◎”, “◯”, “Δ”, and “X” indicate the degree of occurrence of scintillation in order, and “X” indicates that the occurrence of scintillation was observed.

(Example 2)
A light diffusing sheet was prepared and evaluated in the same manner as in Example 1 except that the inorganic filler was amorphous alumina having a refractive index of 1.56, an average particle diameter of about φ20 μm.
The evaluation results are shown in Table 2.

(Comparative example)
As a comparative example, an acrylic-styrene copolymer (refractive index: 1.49 to 1.59) is used as the transparent resin, and an organic filler (refractive index: 1.49 to 1.59, particle size 1) is used as the diffusion particle. A light diffusing sheet was prepared and evaluated in the same manner as in Example 1 using only ˜30 μm, about 10%)).

  From the results of Tables 1 and 2, the light diffusive sheet according to the present invention has less scintillation compared to the sheet of the comparative example. According to this, the appearance rate of scintillation depends on the ratio of the added amount of organic filler and inorganic filler. It was confirmed that it changed.

  The light diffusing sheet according to the present invention is a light diffusing layer made of a transparent resin in which light diffusing fine particles made of a mixture of a spherical organic filler and an indefinite shape filler are dispersed on a translucent substrate. As a result, it was possible to maintain a wide range of brightness over the entire screen, and to suppress the occurrence of scintillation.

It is sectional drawing which shows an example of the light diffusable sheet | seat of this invention. It is a schematic sectional explanatory drawing of the image display apparatus which has a light diffusable sheet of this invention. It is a schematic sectional drawing of the lens sheet which has a light diffusable sheet of this invention. It is a schematic sectional explanatory drawing of the transmissive | pervious projection screen which has the light diffusable sheet | seat of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light diffusable sheet 2 ... Light diffusible fine particle 3 ... Organic filler 4 ... Inorganic filler 5 ... Transparent resin 6 ... Translucent base material 7 ... Light diffusing layer 8 ... Lenticular lens part 9 ... Lenticular lens part 10 ... Fresnel lens part DESCRIPTION OF SYMBOLS 11 ... Fresnel lens sheet 12 ... Lens sheet 13 ... Transmission type projection screen 14 ... Image | video display body 15 ... Image display apparatus 16 ... Reflective mirror 17 ... Reflective mirror

Claims (10)

  A light diffusion sheet comprising a light diffusing layer made of a transparent resin in which light diffusing fine particles are dispersed on a light transmissive substrate, wherein the light diffusing fine particles are a mixture of a spherical organic filler and an amorphous inorganic filler. A light diffusing sheet characterized by the above.   2. The light diffusing sheet according to claim 1, wherein the organic filler is an acrylic / styrene copolymer resin, and the inorganic filler is magnesium silicate.   2. The light diffusibility according to claim 1, wherein the refractive index of the organic filler is in the range of 1.49 to 1.59, and the refractive index of the inorganic filler is in the range of 1.4 to 1.7. Sheet.   The light diffusive sheet according to claim 1, wherein the refractive index difference between the transparent resin and the light diffusing fine particles is in the range of 0 to 0.1.   The thickness of a light-diffusion layer is the range of 1-500 micrometers, The light-diffusion sheet | seat in any one of Claims 1-4 characterized by the above-mentioned.   The light diffusing sheet according to any one of claims 1 to 5, wherein the amount of the light diffusing fine particles added is in the range of 1 to 65% by weight in 100% by weight of the light diffusing layer.   The light diffusing fine particles have an average particle diameter of the organic filler in the range of 1 to 30 μm and an average particle diameter of the inorganic filler in the range of 0.1 to 60 μm. A light diffusing sheet according to claim 1.   7. A lens sheet, wherein the light diffusing sheet according to claim 1 is disposed on a surface side of the lens sheet where the lens portion is not formed, or between the surface side and the lens portion.   The lens sheet according to claim 8, wherein the lens sheet is either a lenticular lens sheet or a Fresnel lens sheet.   An image in which a display image is formed by irradiating illumination light to an image display element whose display pixels are defined by transmission / non-transmission, transmission / light dispersion, or selective reflection, and projecting the display image on the display screen It is a display apparatus, Comprising: The light diffusable sheet in any one of Claims 1-7 is arrange | positioned on the said display screen individually or in combination with another lens sheet, The image display apparatus characterized by the above-mentioned.

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