JP2008286960A - Microlens array sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microlens array sheet for a transmission type screen that is a light diffusion sheet which has high transmittance, by which a bright video is observed, by which an observer does not feel an unnatural feeling even when observing the video while changing a viewing angle and which has excellent diffusing performance. <P>SOLUTION: The microlens array sheet comprises a light emitting substrate 2 composed of transparent material, and a microlens comprising a light shielding layer 3 arranged on the light emitting substrate and having a plurality of nearly rectangular holes, a resin layer 4 provided on the surface of the light shielding layer and having a first refractive index, and a resin layer 5 formed to cover over the hole parts on the resin layer having the first refractive index and having a second refractive index, and the curvature of the microlens on the light emitting substrate side is larger than the 1/2 of the short side of the hole on the light emitting substrate side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a microlens array sheet having a plurality of spherical or aspherical microlenses, and more particularly to a transmissive screen microlens array sheet used in a rear projection type projection television.

  Conventionally, a screen using a microlens array sheet has been used to improve the viewing angle for a rear projection type projection television (see, for example, Patent Document 1). In this microlens array sheet, as shown in FIG. 10, a plurality of substantially conical holes 33 are provided in the light-shielding substrate 24, and the microlenses 26 are disposed on the holes 33. Since the hole 33 has a substantially conical shape in which the opening diameter on the microlens array 27 side is larger than the opening diameter on the opposite side, a high transmittance and high contrast image can be obtained.

  However, in this configuration, the viewing angle cannot be increased. Therefore, in order to further widen the viewing angle, a configuration in which a substantially conical hole itself provided in the social base material is used for the microlens is conceivable. The configuration is shown in FIG. FIG. 5A is a perspective view of the entire microlens, and the individual microlenses are arranged in a staggered manner. FIG. 5B is an enlarged portion of the microlens portion. As shown in the figure, a light shielding layer 3 having a hole tapered in the direction of the light emitting substrate 2 is provided on the light emitting substrate 2, and a resin layer 4 having a low refractive index is coated on the surface of the hole, On top of that, the entire hole is filled with a resin 5 having a refractive index higher than that of the resin layer 4 to form a macro lens.

A cross section of the microlens is shown in FIG. A low refractive index transparent layer is formed in a thin film shape of about 1 μm on the triangular inclined surface of the light shielding layer 3 and functions as a reflective layer. Further, the opening 6 sandwiched between the leg portions of the cross-sectional triangle of the light shielding layer 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.
JP 2006-209057 A

  However, in the conventional configuration, as shown by the dotted line in FIG. 7, the parallel light perpendicularly incident on the microlens array sheet 1 causes total reflection at a location intersecting the resin layer 4, and the totally reflected light. Is caused to return to the incident side of the microlens array sheet 1 by repeating total reflection on the resin layer 4 having the first refractive index formed on the opening 6, thereby reducing the transmittance. Had problems.

  The position where the return light is generated is a specific position. FIG. 8B shows a measurement method. The parallel light 9 emitted from the light source 11 passes through the microlens, and the light emitted to the light emitting substrate 2 is received by the detector 12 to measure the amount of emitted light. In this example, when the size of the short side of the microlens is 60 μm and the width Sw of the light source 11 that emits parallel light is 2 μm, the position of the light source that emits parallel light is the horizontal axis, and the position of the center of the microlens Is 0, and the position of the top of the light shielding layer 3 is 30. If the vertical axis represents the transmittance (ratio of the amount of emitted light to the amount of incident light), as shown in FIG. 9, the transmittance decreases in the range from 7.5 to 12.5 on the horizontal axis. That is, the light transmittance is reduced at this portion.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a microlens array sheet incorporating a light shielding layer with improved light transmittance.

  A light emitting substrate made of a transparent material, a light shielding layer having a plurality of substantially rectangular holes disposed on the light emitting substrate, a resin layer having a first refractive index provided on the surface of the light shielding layer, A microlens made of a resin layer having a second refractive index formed so as to cover the hole on the resin layer having the first refraction, and a curvature of the microlens on the light output substrate side is the light It is characterized by being larger than ½ of the short side of the hole on the output substrate side.

  According to the microlens array sheet of the present invention, the light component directly incident on the low refractive index resin lens formed at the opening of the sheet is controlled by the total reflection by controlling the magnitude of the curvature of the low refractive index resin. It is possible to suppress the return light, and it is possible to apply a low-refractive index resin as a reflective surface with a constant thickness up to the opening with respect to the slope of the light shielding layer. With respect to the light reflected by the applied low refractive index resin, the ratio of return light due to total reflection can be reduced, and a bright image can be obtained as a whole screen.

(Embodiment)
Hereinafter, embodiments of the microlens array sheet of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional structure diagram of the microlens array sheet of the present invention in the vertical direction. In FIG. 1A, a microlens array sheet 1 is roughly composed of a light emitting substrate 2, a light shielding layer 3, a resin layer 4 having a first refractive index, and a resin layer 5 having a second refractive index. Composed.

  The light emitting 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 the diameter of the base material is about 10 μm or less. 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 light shielding layer 3 is a combination of the first three-dimensional light shielding portion 301 having a quadrangular cross section and the second three-dimensional light shielding portion 302 having a triangular cross section, both of which are thermosetting or two-component curable as a base material. An EB curable polyurethane-based resin or the like is used, and light-absorbing black pigment fine particles are dispersed in the substrate.

  In this embodiment, the thickness of the light emitting substrate 2 is 1 mm, and the horizontal and vertical pitches of the light shielding layer 3 are 60 μm and 85 μm, respectively. With respect to the cross section of the light shielding layer 3 in FIG. 1A, the cross section of the first three-dimensional light shielding portion 301 having a quadrangular cross section is rectangular, and the length a in the direction perpendicular to the screen surface of the first three-dimensional light shielding portion 301. Is 10 μm, the horizontal length 2b is 40 μm, and a half of this is b (= 20 μm). Further, the cross-sectional shape of the second three-dimensional light shielding portion 302 is substantially triangular, and the combined height h0 of the first three-dimensional light shielding portion 301 and the second three-dimensional light shielding portion 302 is 156 μm. Further, the angle θ1 formed by the inclined surface and the horizontal plane at the bottom of the triangular cross section of the second three-dimensional light shielding portion 302 is 80 deg, and the angle θ2 formed by the inclined surface near the top of the triangular triangular shape of the second three-dimensional light blocking portion 302 and the horizontal plane is 85 deg. The slope between the bottom and the top of the triangular cross section of the second three-dimensional light shielding portion 302 is an arc. The width B of the opening 6 is 20 μm.

  Next, a low refractive index transparent resin lower than the refractive index of the resin used in the resin layer 5 having the second refractive index is used as a material and applied to the surface of the light shielding layer 3 and the surface of the opening 6. A resin layer 4 having a refractive index is formed. For example, a low refractive index acrylate resin into which silicon or fluorine is introduced is used. This time, a transparent UV curable resin having a low refractive index and a material having a refractive index of 1.46 were used.

  This low refractive index transparent ultraviolet curable resin was quantitatively applied to the concavo-convex surface of the light shielding layer 3 by a spray method, and then UV cured. Prior to spray application, the surface of the light shielding layer 3 was treated with ozone 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 shielding layer 3, and a spherical refractive lens 8 is formed in the opening 6 by a concave meniscus.

  The spherical refractive lens 8 is formed between the boundary between the first three-dimensional light shielding part and the second three-dimensional light shielding part. The height position of the spherical refractive lens 8 and the magnitude of the curvature are inflection points P and P ′ at the boundaries between the first three-dimensional light shielding portion 301 and the second three-dimensional light shielding portion 302 in FIG. The magnitude of the curvature of the lens formed between -P 'is adjusted by the amount of liquid applied. That is, the concave spherical refractive lens 8 formed at the position PP ′ of the boundary between the first three-dimensional light shielding portion 301 and the second three-dimensional light shielding portion 302 is adjusted by applying a large amount of liquid. Curvature increases.

  Next, a transparent UV curable resin having a high refractive index to be the resin layer 5 having the second refractive index was applied by a spray method so that the film thickness from the top of the light shielding layer 3 was 100 μm. A material having a refractive index of 1.57 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.

  In addition, as shown in FIG. 5, the shape of the opening part on the opposite side of the light diffusing screen 1 of the light diffusing screen 1 is arranged in an infinite number of substantially rectangular shapes in a staggered manner. The shape which closely arranged what has the shape of this may be sufficient.

  Next, the results of performance evaluation by optical simulation on the produced light diffusion screen 1 will be described.

  FIG. 3 is a graph showing the change in transmittance depending on the position of the light source of the microlens array sheet in Embodiment 1 of the present invention. Moreover, the figure which shows typically the measurement by the position of the light source of a micro lens array sheet | seat in FIG. 8 is shown. In FIG. 3, the horizontal axis represents the position of the light source. The position at which the light source is placed at the center of the spherical refractive lens 8 in FIG. 8 (on the broken line (i)) is 0 μm, and the position at which the light source is placed at the top of the light shielding layer 3 (on the broken line in (ii)) is 30 μm. . The light source width Sw is 2 μm. The vertical axis represents the screen transmittance. The detector 12 is placed on the exit side of the screen, and the value obtained by dividing the amount of light generated from the light source by the amount of light received by the detector 12 is taken as the transmittance. Regarding the characteristics of FIG. 3, the solid line shows the transmittance distribution according to the shape of the present invention, and the broken line shows the transmittance distribution according to the conventional shape.

  When the position of the light source is 0, the transmittance is about 90% for both the shape of the present invention and the conventional shape. However, the position of the light source is shifted, and the transmittance decreases as the value increases. Both the shape of the present invention and the conventional shape are minimum values. The transmittance at that time is 50% for the conventional shape and 70% for the shape of the present invention. When the position of the light source exceeds 10, the transmittance is improved. When the position of the light source is 30, the transmittance is again 90%. From the transmittance distribution of FIG. 3, a difference in transmittance occurs when the position of the light source is in the range of 7.5 to 12.5 and the conventional shape and the shape of the present invention are compared. This is because the spherical refractive lens 8 of FIG. 8A is formed below the bottom surface of the first three-dimensional light shielding portion 301, so that the first three-dimensional light shielding portion 301 is coated on the surface. The ratio of the light reflected by the resin layer 4 having a refractive index that is transmitted through the opening 6 and the light emitting substrate 2 is increased as compared with the conventional shape, and the curvature of the spherical refractive lens 8 is adjusted, so that the screen In the vertically incident light, the light directly incident on the spherical refractive lens 8 without being reflected by the resin layer 4 having the first refractive index is transmitted through the opening 6 and the light emitting substrate 2 without causing total reflection. It is.

  FIG. 4 is a characteristic diagram of screen transmittance with respect to the dimensional ratio of the spherical refractive lens 8 of the present invention. With respect to the concave spherical refractive lens 8 in FIG. 1B, the width of the formed lens (the width between PP ′) is Lw, and the boundary between the first three-dimensional light shielding portion 301 and the second three-dimensional light shielding portion 302 When the height from the position PP ′ to the bottom surface is Lh, parallel light emitted from the light source is directly incident on the concave spherical refractive lens 8 and the characteristic of the magnitude of transmittance with respect to the ratio of Lh / Lw The figure is shown in FIG. As the Lh / Lw ratio increases, the curvature of the concave spherical refractive lens 8 decreases, and when Lh / Lw is 0.5, the concave spherical refractive lens 8 has a semicircular cross section.

  The setting of the light source is set to 20 μm, similar to the length of Lw. FIG. 4 shows characteristics when the refractive index of the resin layer having the first refractive index is 1.46 and the refractive index of the resin layer having the second refractive index is 1.57. When the value of Lh / Lw ranges from 0 to 0.3, the transmittance is about 93%. However, when the value of Lh / Lw exceeds 0.3, the transmittance decreases linearly. That is, in order to set Lh / Lw within a range where the transmittance does not decrease and to maximize the diffusion effect by the lens, the refractive index of the resin layer having the first refractive index in FIG. When the refractive index of the resin layer having the second refractive index is 1.57, it is desirable to set Lh / Lw to around 0.3.

  The diffusing sheet for a transmissive screen according to the present invention eliminates unevenness due to three luminance peaks that strongly appear in the total reflection type light diffusing sheet, has a wide viewing angle and high transmittance, and is used as a rear projection display or the like. Useful.

The figure which shows typically the cross section of the micro lens array sheet in Embodiment 1 of this invention. Explanatory drawing of the effect of the invention of the microlens array sheet in Embodiment 1 of this invention The graph which shows the change of the transmittance | permeability by the position of the light source of the micro lens array sheet in Embodiment 1 of this invention Characteristic chart of screen bottom curvature and transmittance of microlens array sheet in Embodiment 1 of the present invention The perspective view of the whole micro lens array sheet in Embodiment 1 of this invention The figure which shows the cross section of the conventional micro lens array sheet typically Operation explanatory diagram of a conventional microlens array sheet The figure which shows typically the measurement by the position of the light source of a micro lens array sheet Characteristic diagram showing the change in transmittance according to the position of the light source of the conventional microlens array sheet The figure which shows the conventional micro lens array sheet typically

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusing sheet 2 Light emission board | substrate 3 Light-shielding layer 4 Resin layer with 1st refractive index 5 Resin layer with 2nd refractive index 6 Opening part 7 Reflective lens 8 Spherical refractive lens 9 Parallel light 10 Reflected light 11 Light source 12 Detector 24 Light-shielding base material 25 Transparent layer 26 Micro lens 27 Micro lens array 32 Laser light 33 Self-alignment hole 34 Light emitting surface 35 Micro lens array sheet 301 First three-dimensional light shielding portion 302 Second three-dimensional light shielding portion

Claims (4)

A light emitting substrate made of a transparent material;
A light shielding layer having a plurality of substantially rectangular holes disposed on the light emitting substrate;
A resin layer having a first refractive index provided on the surface of the light shielding layer;
A microlens made of a resin layer having a second refractive index which is higher in refractive index than the resin layer having the first refraction and is formed on the resin layer having the first refraction so as to cover the hole. When,
A microlens array sheet in which a curvature of the microlens on the light output substrate side is larger than ½ of a short side of the hole on the light output substrate side. The light shielding layer is configured to cover a first three-dimensional light shielding portion to which a resin layer having a first refractive index serving as a reflection surface is applied, and the substantially rectangular hole below the first three-dimensional light shielding portion. The curvature of the resin layer having the first refractive index is formed, and a second three-dimensional light shielding portion is formed between the first three-dimensional light shielding portion and the light emitting substrate. The microlens array sheet according to 1. The microlens array sheet according to claim 1, wherein a shape of the microlens is a spherical surface or an aspherical surface. 2. The microlens array sheet according to claim 1, wherein the substantially rectangular hole has an opening on the light emitting substrate side smaller than an opening on the opposite side to the light emitting substrate side.

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