JPH10282496A - Light transmission body, production of light transmission body and surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight surface light source reduced at its parts cost and manufacturing cost, a light transmission body included in the surface light source and the manufacturing method of the light transmission body by reducing the number of lenticular lens sheets to be used or eliminating the necessity of the sheet. SOLUTION: A transparent lens part 2 consisting of plural lenticular unit lenses formed by the same resin as the material of the light transmission body 1 is formed on the body 1. Each lenticular unit lens of the lens part 2 is a recessed or projected triangle pole prism and the ridge directions of respective lenticular unit lenses are mutually arrayed in approximately parallel. The vertical angles of these prisms are formed within a range of 125 deg. to 165 deg.. A face opposed to the lens part 2 is treated by light untransmitting processing so as not to transmit light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide, a method of manufacturing the light guide, and a surface light source, and more particularly, to a surface light source used for a backlight of a liquid crystal display device, an illumination advertisement, a traffic sign, and the like. And a light guide provided in the surface light source and a method for manufacturing the light guide.

[0002]

2. Description of the Related Art As a surface light source for a backlight of a liquid crystal display (LCD), an edge light type using a light-transmitting flat plate as a light guide is known. In such a surface light source,
Light is incident from both or one of the side end surfaces of the light guide made of a transparent parallel plate, and light is propagated throughout the light guide using the total internal reflection inside the light-transmitting plate. A part of the light is reflected by the light-scattering reflector on the back surface of the light guide to form a diffuse reflection light having a critical angle less than the critical angle, and diffuse light is emitted from the surface of the light guide.
-162201).

Also, a lens sheet having a triangular prism type lenticular lens projection on one surface and a smooth surface on the other surface is placed on the light guide surface of the above-mentioned surface light source with the projection surface up. Using the light focusing action of the lens,
A device capable of uniformly and isotropically diffusing the diffused radiation within a desired angle range is also known (Japanese Utility Model Application Laid-Open No. 4-1).
07201).

When this lens sheet is used in combination with a matte transparent diffuser (matte transparent sheet), the lens sheet uses only a matte transparent diffuser (US Pat. No. 4,729,067).
), The light energy of the light source can be more preferentially distributed within a desired limited angle range, and diffused light having high uniform isotropy can be obtained within that angle range. More recently, as a measure against the high luminance of the backlight used in the liquid crystal display device, there is a tendency to adopt a configuration in which two lenticular lens sheets are stacked at right angles as shown in FIG. 1 (Monthly Display, May 1996, p. 35). ~ P39).

[0005]

However, the conventional backlight of a liquid crystal display device not only has the problem that the visual characteristics are relatively narrow, but also uses two lenticular lens sheets. In addition to the cost, it is necessary to attach two lenticular lens sheets at right angles to each other and attach them, so that there is a problem in that a large manufacturing cost is generated and the backlight itself becomes very expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has reduced the cost of parts and manufacturing by reducing the number of lenticular lens sheets used to one or even eliminating the need. It is an object to provide a surface light source for a backlight, a light guide included in the surface light source, and a method for manufacturing the light guide.

[0007]

According to a first aspect of the present invention, there is provided a light guide, comprising: a light guide that emits light emitted from a light source provided adjacent to at least one side end face; A light guide that emits light from a light emitting surface, the light emitting surface comprising a first lens unit including a plurality of concave or convex lenticular unit lenses molded of the same resin as the light guide, The plurality of lenticular unit lenses of the lens portion are triangular prism prism portions having an apex angle of 125 to 165 degrees, and their ridge lines are arranged substantially parallel to each other.

According to a second aspect of the present invention, in the light guide according to the first aspect, an angle of a top of the plurality of lenticular unit lenses of the first lens portion is 135 to 165 degrees. It is characterized by the following. According to a third aspect of the present invention, in the light guide according to the first or second aspect, the angle of the top of the plurality of lenticular unit lenses of the first lens unit is about 150 degrees. It is characterized by.

A light guide according to a fourth aspect of the present invention is the light guide according to any one of the first to third aspects,
A light reflecting surface opposed to the light emitting surface, a second lens portion including a plurality of concave or convex lenticular unit lenses formed of the same resin as the light guide, and a plurality of the second lens portions; Is a triangular prism having an apex angle of 125 to 165 degrees, and their ridge directions are arranged substantially parallel to each other.

According to a fifth aspect of the present invention, in the light guide according to the fourth aspect, an angle of a top of the plurality of lenticular unit lenses of the second lens portion is 135 to 165 degrees. It is characterized by the following. According to a sixth aspect of the present invention, in the light guide according to the fourth or fifth aspect, an angle of a top of the plurality of lenticular unit lenses of the second lens unit is about 150 degrees. It is characterized by.

A light guide according to a seventh aspect of the present invention is the light guide according to any one of the fourth to sixth aspects,
The ridge line directions of the plurality of lenticular unit lenses of the first lens unit and the ridge line directions of the plurality of lenticular unit lenses of the second lens unit are substantially orthogonal to each other. The surface light source of the present invention according to claim 8 includes the light guide according to any one of claims 1 to 7, and a light source provided adjacent to at least one side end surface of the light guide. It is characterized by having.

According to a ninth aspect of the present invention, there is provided a method of manufacturing a light guide according to any one of the first to seventh aspects, wherein the light guide is formed by a mold. It is characterized by including a step of molding.

[0013]

Embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 7A and 7B are perspective views showing a light guide, and the following terms are defined using this figure. A lenticular unit lens is shown in FIG.
In FIG. 7B, a triangular prism having a triangular base formed by a vertex ABC and a pentagonal prism having a pentagon formed by a vertex ABDEC as a base is referred to. However, the lenticular unit lens 1 exemplified here
b is merely an example, and is not limited to these. In addition, in this figure, the lenticular unit lens has only a convex shape, but may have a concave shape (not shown).

The prism portion of the triangular prism of the lenticular unit lens corresponds to the vertex AB in both FIGS. 7A and 7B.
A triangular prism having a triangular bottom formed by C as a bottom surface. The top of the triangular prism is the vertex A in both FIGS. 7A and 7B.

The angle of the top of the prism portion of the triangular prism refers to the angle formed by the point BAC in both FIGS. 7A and 7B. FIGS. 8A, 8B, and 8C are schematic diagrams showing a cross-sectional shape of a triangular prism. As shown in FIG. 8 (A), the prism portion of the triangular prism is desirably an isosceles triangle. For example, as shown in FIG. 8 (B), the top A is slightly chipped and becomes a pentagonal shape. Even if the top A has a smoothly curved shape as shown in FIG. 8C, it hardly affects the performance of the light guide. Therefore, all prisms having these shapes are included in the prism portion of the triangular prism of the present invention. It is.

FIG. 2 is a perspective view showing a light guide according to the present invention. The light guide 1 is provided with a transmission lens portion 2 including a plurality of lenticular unit lenses formed of the same resin as the light guide 1. The opposite surface of the transmission lens unit 2 is subjected to light reflection processing (for example, fine irregularities or spot-like processing such as screen printing) for irregularly reflecting and uniformly diffusing light, and preventing light leakage. For this purpose, a reflection plate is attached in a later step (not shown).

The lenticular unit lens of the transmission lens section 2 is a prism having a triangular prism, and the ridge directions thereof are arranged substantially parallel to each other. In particular, the apex angle of the prism having the triangular prism is based on a calculation result described later. , 125 degrees to 165 degrees. Also, if the apex angle of the triangular prism is in the range of 125 to 165 degrees, the performance of the light guide body is not affected even if the size, pitch, height and apex angle of the triangular prism fluctuate or vary. Has no effect. In particular, as shown in FIG. 9, even when the pitch of the prism is changed in the range of 10 μm to 1000 μm,
It can be seen that the luminance distribution characteristics do not change significantly.

The material of the light guide 1 is selected from translucent materials. Usually, acrylic or polycarbonate resin is used. The thickness of the light guide is usually 1 to 10 m
m is used. Other translucent materials include acrylate or methacrylate homo- or copolymers such as polymethyl methacrylate and polymethyl acrylate, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and the like.
Thermoplastic resin such as polycarbonate, polystyrene, polymethylpentene, or cross-linked by ultraviolet or electron beam,
Acrylics such as polyfunctional urethane acrylates and polyester acrylates, transparent resins such as unsaturated polyesters, transparent ceramics such as transparent glass, and the like are used.

Next, the operation of the light guide according to the present invention will be described with reference to FIG.
This will be described with reference to FIG. Light (right side in FIG. 2) emitted from a light source (not shown) provided adjacent to the side end surface 1a of the light guide 1 enters the inside of the light guide 1 from the side end surface 1a, and is transmitted through the transmission lens portion. The light reflected on the side surface other than the opposing surface and the side end surface 1a of the second lens 2 and guided toward the transmission lens portion 2 has an action of converging the light, and diffuses the radiated light within a desired angle range. The light is emitted from the transmission lens unit 2 that uniformly and isotropically diffuses (upward in FIG. 2).

FIG. 3 is a graph showing luminance distribution characteristics. The horizontal axis represents the position of the light guide from the lamp in percent, with the length of the light guide as 100%,
The position of the value 0 is the end face position of the light guide closest to the lamp, while the position of the value 100 is the end face position of the light guide farthest from the lamp. The vertical axis does not show a unit, but is a luminance, and a larger value means a brighter.

FIG. 3 is a graph showing the luminance distribution characteristics of the light guide obtained by analyzing the luminance distribution characteristics of the light guide using CODE, which is an optical design evaluation software developed by ORA in the United States. The wavelength of the irradiated light is 600 nm, the refractive index of typical PMMA is 1.49 as the material of the light guide, and the apex angles of the triangular prism are 90 °, 120 °, 125 °, 150 °, 16 °.
The simulation results of the luminance distribution characteristics when the angle is changed to 5 ° and flat (that is, without a triangular prism) are shown.

As can be clearly seen from the figure, the apex angle of the lens sheet used with the conventional light guide is 9
The luminance distribution characteristics from 0 ° to 120 ° are not only inferior to those that are flat, but also 125 °.
The luminance distribution characteristics from to 165 ° are greatly improved as compared with the conventional luminance distribution characteristics from 90 ° to 120 °. Further, the characteristic improvement from 135 ° to 165 ° is remarkable, and it can be easily understood that a peak effect appears in the luminance distribution characteristic especially around 150 °.

However, even if the wavelength of light or the refractive index of the material of the light guide is slightly changed, there is no significant effect on the luminance distribution characteristics found here. In addition, the present applicant has departed from the conventional idea of 90 ° to 120 °, which is the range of the apex angle of the conventional lens sheet, and independently simulated the basic optical design of the light guide. 125 ° to 1
The present inventors have found that the temperature can be greatly improved in the range up to 65 °, and propose a completely new light guide plate based on the results.

FIG. 4 is a graph showing viewing angle characteristics.
The horizontal axis indicates the viewing angle with respect to the light guide, and the value 0
(Not shown) is the direction perpendicular to the light guide, and the value -9
0 means a direction horizontal to the light guide. The vertical axis does not show a unit, but is a luminance, and a larger value means a brighter.

The graph showing the viewing angle characteristics of FIG. 4 is obtained by analyzing the viewing angle characteristics of the light guide using CODE in the same manner as described above. As an evaluation parameter, the wavelength of light emitted from the lamp is set to 600 nm. The typical refractive index of PMMA is 1.49 as the material of the light guide, and the apex angles of the triangular prisms are 90 °, 120 °, 125 °, 135 °, and 1 °.
10 shows simulation results of luminance distribution characteristics when the angle is changed to 50 °, 165 ° and flat (that is, without a triangular prism).

As can be clearly seen from the figure, the apex angle of the lens sheet used with the conventional light guide is 9
Comparing the viewing angle characteristics of 0 ° and the viewing angle characteristics of 120 °, the result of 120 ° is much worse than that of 90 °, while the viewing angle characteristics from 125 ° to 165 ° are It can be easily understood that the viewing angle characteristic is much improved as compared with the conventional 90 ° viewing angle characteristic, and a peak effect appears.

FIG. 5 is a perspective view showing a light guide according to the present invention. The light guide 1 is provided with a transmission lens unit 2 and a reflection lens unit 3 formed of a plurality of lenticular unit lenses formed of the same resin as the light guide 1. The lenticular unit lenses of the transmission lens unit 2 and the reflection lens unit 3 are triangular prisms, and their ridge directions are arranged substantially parallel to each other, and the ridge direction of the plurality of lenticular unit lenses of the transmission lens unit 2 And the lenticular directions of the plurality of lenticular unit lenses of the reflection lens unit 3 are arranged so as to be substantially perpendicular to each other.

Further, the lower surface of the reflecting lens section 3 is subjected to a reflecting surface treatment by aluminum vapor deposition or the like so as not to transmit light (not shown). Next, the operation of the light guide according to the present invention will be described with reference to FIG. Light (right side in FIG. 5) emitted from a light source (not shown) provided adjacent to the side end face 1a of the light guide 1 enters the inside of the light guide 1 from the side end face 1a and is reflected by the reflection lens portion. 3 is reflected on the lower surface and on the side end surfaces other than the side end surface 1a. At this time, the reflection lens unit 3 has an action of equalizing the light guided to the transmission lens unit 2 in the light guide 1, and guides the diffused light toward the transmission lens unit 2.

The light guided toward the transmission lens unit 2 by the reflection lens unit 3 has a function of converging the light, and diffuses the diffused radiation uniformly and isotropically within a desired angle range. The light exits from the transmission lens unit 2 (upward in FIG. 5). FIG. 6 is a schematic diagram showing a liquid crystal display device including the surface light source according to the present invention. The liquid crystal display device includes a liquid crystal panel 6 and a surface light source 5, and the surface light source 5 includes the light guide 1 according to the present invention, the light source 4 such as a fluorescent tube, and various control circuits (not shown). I have.

The light emitted from the light source 4 enters the inside from the side end surface of the light guide 1, is reflected by the side end surface other than the lower surface and the side end surface of the reflection lens unit 3, repeats focusing, and diffused light is desired. Is uniformly and isotropically diffused within the angle range described above and guided to the liquid crystal panel 6. Further, in the method for manufacturing a light guide according to the present invention, a mold in which a fine pattern of the transmission lens portion 2 is processed, or a mold in which a fine pattern of the transmission lens portion 2 and the reflection lens portion 3 are processed, The method includes a step of molding the light guide, wherein a plurality of lenticular unit lenses molded with the same resin as the light guide are formed simultaneously with the molding.

Further, the applicant of the present application has disclosed a light guide for a surface light source or a light guide for a light source according to Japanese Patent Application Nos. 7-286046, 7-286047 and 7-304484 as one means for reducing the manufacturing cost of the light guide. An application for a method for manufacturing a light guide has been filed.
In Japanese Patent Application Nos. Hei 7-286046 and Hei 7-286047, one surface of a flat plate is used as a light emitting surface, and a fine pattern that provides a lens effect is formed only on this surface, and only a mold part on which the fine pattern is applied is formed. Exchangeable.

In Japanese Patent Application No. 7-304484, a light opaque process is performed on the lower surface of the reflection lens unit 3.
A heat transfer foil is inserted in a mold part for forming a fine pattern of the above, and the light-impermeable material thin film laminated on the heat transfer foil is transferred simultaneously with molding by the heat of fusion at the time of resin injection and the molding pressure. Therefore, by applying the present invention to the above-described invention, it is possible to eliminate the need for two lens film sheets, which have been conventionally required, and to perform light opaque treatment on the lower surface of the reflective lens portion 3 simultaneously with molding. It can be expected to bring a new effect that leads to significant cost reduction.

[0033]

As described above, according to the light guide and the method of manufacturing the light guide according to the present invention, since the lenticular lens is formed simultaneously with the molding, the number of lenticular lens sheets conventionally required is used. It can be reduced or even eliminated, resulting in a significant reduction in manufacturing costs.

According to the surface light source of the present invention, since the light guide is used, the component cost of the surface light source can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a conventional liquid crystal display device.

FIG. 2 is a perspective view showing a light guide according to the present invention.

FIG. 3 is a graph showing luminance distribution characteristics.

FIG. 4 is a graph showing viewing angle characteristics.

FIG. 5 is a perspective view showing a light guide according to the present invention.

FIG. 6 is a schematic view showing a liquid crystal display device including a surface light source according to the present invention.

FIG. 7 is a perspective view showing a light guide.

FIG. 8 is a schematic view showing a cross-sectional shape of a prism portion of a triangular prism.

FIG. 9 is a graph showing a change in a luminance distribution characteristic with respect to a prism pitch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide 1a End surface 1b Lenticular unit lens 2 Transmission lens part 3 Reflection lens part 4 Light source 5 Surface light source 6 Liquid crystal panel

 ──────────────────────────────────────────────────の Continued on the front page (72) Katsutoshi Hibino 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kenji Torazawa 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5-5 Sanyo Electric Co., Ltd. (72) Inventor Masahiro Higuchi 2-5-5 Sanyo Electric Co., Ltd., Osaka Prefecture Moriguchi City Inside (72) Inventor Takaya Fukakusa Keihan Motodori, Moriguchi City, Osaka Prefecture 2-5-5 Sanyo Electric Co., Ltd.

Claims (9)

[Claims] 1. A light guide for emitting light emitted from a light source provided adjacent to at least one side end surface from a light emitting surface, wherein the light emitting surface is formed of the same resin as the light guide. A plurality of concave or convex lenticular unit lenses, and the plurality of lenticular unit lenses of the first lens unit is a triangular prism having a top angle of 125 to 165 degrees. Wherein the ridge lines are arranged substantially parallel to each other. 2. The light guide according to claim 1, wherein an angle of a top of the plurality of lenticular unit lenses of the first lens portion is 135 degrees to 165 degrees. 3. The light guide according to claim 1, wherein an angle of a top of the plurality of lenticular unit lenses of the first lens unit is about 150 degrees. . 4. The light guide according to claim 1, wherein a plurality of recesses or a plurality of recesses formed of the same resin as the light guide are provided on a light reflection surface facing the light emission surface. A second lens unit including a convex lenticular unit lens, wherein the plurality of lenticular unit lenses of the second lens unit are triangular prism prism units having a top angle of 125 to 165 degrees, and their ridge lines A light guide, wherein directions are arranged substantially parallel to each other. 5. The light guide according to claim 4, wherein an angle of a top of the plurality of lenticular unit lenses of the second lens unit is 135 to 165 degrees. 6. The light guide according to claim 4, wherein an angle of an apex of the plurality of lenticular unit lenses of the second lens unit is about 150 degrees. . 7. The light guide according to claim 4, wherein a ridge line direction of the plurality of lenticular unit lenses of the first lens unit and a plurality of lenticular unit lenses of the second lens unit. The light guide is characterized in that the ridge directions of the light guides are arranged substantially perpendicular to each other. 8. A light guide according to claim 1, further comprising: a light source provided adjacent to at least one side end surface of the light guide. Surface light source. 9. The method of manufacturing a light guide according to claim 1, further comprising a step of molding the light guide with a mold. Manufacturing method.