JPH11265612A - Surface light source element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source element having a high quality without causing a dazzle and having a high luminance. SOLUTION: A surface light source element comprises a light source 2, a light guiding body 1 having a light incident surface placed opposite to the light source 2 and a light emitting surface crossed at nearly right angles to the light incident surface, a reflective layer 4 disposed opposite to the light emitting surface, and a light deflecting sheet 3 disposed on the light emitting surface side of the light guiding body 1 and on which many lens rows are formed. In addition, the light deflecting sheet 3, the light guiding body 1, and the reflective layer 4 are formed as the surface light source element wrapped by a reflector 5 together with the light source 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a notebook computer,
The present invention relates to a surface light source element constituting a back light source device used for a liquid crystal display device used for a liquid crystal television, a signboard, a traffic guide board, and the like.

[0002]

2. Description of the Related Art As a rear light source device used for a liquid crystal display device, a signboard, a traffic guide plate, etc., a direct light type, plate-shaped light guide in which a plurality of linear light sources such as fluorescent lamps are installed in a housing. There is an edge light method in which a linear light source is disposed on the side end surface of the light source. In the direct-type back light source device, it is difficult to reduce the weight and thickness of the light source unit, and there is a problem that a see-through phenomenon that a fluorescent light used as a light source can be seen through a sign plate easily occurs. I was An edge light type light source has been widely used as a light and thin back light source device.

[0003] Such an edge light type rear light source device usually uses a plate-shaped transparent material such as an acrylic resin plate as a light guide, and receives light from a linear light source disposed on a side end face thereof. A light emitting surface such as a light scattering portion formed on the front surface (light emitting surface) or the back surface of the light guide is provided by causing the light to enter the light guide from an end surface (light incident surface). From the surface. Further, the light diverting sheet provided on the light guide exit surface directs the light emitted from the light guide toward the observer, thereby improving the luminance.

In such an edge light type surface light source element, there is a problem that a so-called glare phenomenon is observed near the light source, that is, a bright line or a band-like brightness is observed, and the appearance is poor. In particular, as a light diverting sheet, a light diverting sheet provided with a row of prisms parallel to a linear light source is proposed in Japanese Patent Publication No. Hei 7-27137 in which the prism row is set to face the light guide. This phenomenon was remarkably observed in a flat surface light source element.

The cause of the glare phenomenon is considered to be that light having an angle smaller than the critical angle with respect to the light guide exit surface enters from the edges of the light guide and gaps between members. Japanese Patent Application Laid-Open No. 7-270623 proposes a method of arranging a band-shaped light shielding material on the light source side of a light diverting sheet to absorb light that causes glare.
Further, in order to remove light entering from the edge portions of the light guide and the gap between the members, a method of devising the shape of the light guide or providing a shielding material covering the edge portion is disclosed in Japanese Patent Application Laid-Open No. 8-32772.
8 and JP-A-9-197404.

[0006]

However, although these methods can suppress glare to some extent, they have a problem that the luminance of the entire exit surface is reduced and a dark band is generated near the light source. And it was not yet satisfactory. Therefore, an object of the surface light source element of the present invention is to provide a surface light source element that reduces glare, does not lower the luminance of the entire exit surface, and does not cause dark bands.

[0007]

That is, a surface light source element according to the present invention comprises a light source, a light guide having a light incident surface facing the light source and a light exit surface substantially orthogonal thereto, and a light guide opposite to the exit surface. And a light diverting sheet formed by juxtaposing a plurality of lens arrays disposed in parallel on a light exit surface side of the light guide, and the light diverting sheet, The body and the reflective layer are surrounded by a reflector together with the light source.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a surface light source device according to the present invention comprises a linear light source 2, at least one light incident surface facing the light source 2, and a light emitting surface substantially orthogonal to the light source. , A light bending sheet 3 placed on the light exit surface of the light guide 1, a reflection sheet 4 placed on the opposite side of the light exit surface, and a light guide for light from the light source efficiently. And a reflector 5 for guiding into the body.

In the present invention, the lamp reflector 5
Is installed so as to surround the light diverting sheet and the light guide.
By wrapping the light diverting sheet together with the light guide, the traveling direction of the invading light from the edge causing the bright line near the light source is disturbed, and the bright line becomes difficult to visually recognize. In order to effectively prevent glare, between the light diverting sheet 3 and the reflector 5,
Alternatively, the light shielding member 6 can be provided between the light guide 1 and the reflection layer 4 or both. Light turning sheet 3
The width of the shielding material used between the light guide and the reflector 5 is desirably about the same as the thickness of the light guide. If the width is too large, the display area as the surface light source element will be small, and if the width is too small, the effect of preventing light that has entered from the lower edge 7 will be lost. As this shielding material, a sheet having an appropriate transmittance may be inserted into a predetermined place, or a paint having a shielding effect may be printed on the light diverting sheet 3.

The shielding material used between the light guide 1 and the reflection layer 4 has a transmittance that changes stepwise in a direction perpendicular to the linear light source,
It is preferable that the light guide has a structure in which a pattern that minimizes the light transmittance at a portion separated by the light guide thickness from the light incident surface of the light guide is provided. With such a structure, the light that has entered from the upper edge 8 hits the place where the transmittance is lowest, so that the image of the bright line can be reduced. As the shielding material, a material having a pattern printed on a sheet may be used, or a paint having a shielding effect may be printed on the reflective layer.

As the light guide 1, a transparent plate made of glass, synthetic resin or the like can be used. As the synthetic resin, for example, an acrylic resin, a polycarbonate resin, various highly transparent synthetic resins such as a vinyl chloride resin can be used, and this resin is extruded by a normal molding method such as injection molding. The light guide can be manufactured by molding into a plate-like body. In particular, methacrylic resin is excellent in light transmittance, heat resistance, mechanical properties, and moldability, and is most suitable as a light guide material. Such a methacrylic resin is a resin containing methyl methacrylate as a main component, and 80% by weight of methyl methacrylate.
It is preferable that it is above. At least one surface of the light guide is provided with an uneven shape for emitting light. The concavo-convex shape may be minute and random concavo-convex, or may be a lens array parallel to each other, or a lens independent of each other.
The light guide 1 may contain a light diffusing agent, fine particles, or the like. Further, as the light guide 1, various shapes such as a plate shape, a wedge shape, and a boat shape can be used. In order to prevent the glare, it is desirable that a lens array substantially perpendicular to the linear light source is formed on one surface of the light guide 1.

In order to emit light, if the light guide 1 is provided with a minute uneven structure on the surface thereof, the light source 2 should be separated from the surface having the uneven structure from the center of the light guide. It is preferable to install them because it is difficult to see bright and dark bands.
In the surface light source element of the present invention, a light source 2 such as a fluorescent lamp is arranged at one end of the light guide 1 as described above, and a reflection layer 4 is formed on a back surface facing a light emission surface by a reflection film or the like. It is formed.

In the surface light source element of the present invention, the emission direction of the light emitted from the light guide 1 is generally light having directivity in a direction inclined from the normal to the light emission surface. The light deflection sheet 3 is placed on the light guide 1 in order to change the angle in a specific direction such as the normal direction. In this case, examples of the light diverting sheet 3 to be used include a diffusion sheet and a lens sheet having a lens surface in which a large number of lens units are formed in parallel on at least one surface. As the lens shape formed on the lens sheet, various shapes are used depending on the purpose, and examples thereof include a prism shape, a lenticular lens shape, and a corrugated shape. The pitch of the lens unit of the lens sheet is preferably about 30 μm to 0.5 mm, and when a prism sheet is used,
The prism apex angle is appropriately selected according to the outgoing angle of the outgoing light from the light guide, but is generally preferably in the range of 50 to 120 °. Also, the orientation of the prism sheet is appropriately selected according to the emission angle of the light emitted from the light guide, and may be mounted so that the lens surface faces the light guide, or may be mounted in the opposite direction. You may.

A particularly preferred method of use is to install the lens such that the lens surface is on the light guide side. In order to provide an effect of preventing glare, the lens intersects the back surface of the lens surface at a predetermined angle with the back surface of the lens surface. It is more desirable that a surface, a hairline structure, or minute unevenness is provided.
In the surface light source element of the present invention, a plurality of light diverting sheets 3 can be used as required, if necessary. For example, when using two lens sheets,
Two lens sheets can be used stacked such that the respective lens rows are angled or parallel to each other.

The lens sheet of the present invention is preferably manufactured using a material having a high visible light transmittance and a relatively high refractive index. For example, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, an active energy Wire-curable resins and the like can be mentioned. Above all, the scratch resistance of the lens sheet,
Active energy ray-curable resins are preferred from the viewpoints of handleability and productivity. If necessary, additives such as an antioxidant, an ultraviolet absorber, a yellowing inhibitor, a bluing agent, a pigment, and a diffusing agent may be added to the lens sheet. Methods for producing lens sheets include extrusion molding,
Conventional molding methods such as injection molding can be used. When manufacturing the lens sheet 3 using an active energy ray-curable resin, a transparent resin such as a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, or a polyolefin resin is used. A lens portion is formed on a transparent substrate such as a transparent film or sheet using an active energy ray-curable resin. First, an active energy ray-curable resin liquid is injected into a lens mold having a predetermined lens pattern formed thereon, and a transparent substrate is overlaid. Next, an active energy ray such as an ultraviolet ray or an electron beam is irradiated through a transparent base material, and the active energy ray-curable resin liquid is polymerized and cured, and is separated from a lens mold to obtain a lens sheet.

In the surface light source element of the present invention, in addition to the lens sheet as described above, a light diffusing sheet, a color filter, a polarizing film, or the like, optically deforms, converges, or diffuses light, and has an optical characteristic. Various optical elements that vary can be used. By mounting a liquid crystal display element on the light emitting surface side of the surface light source element thus configured, it can be used as a liquid crystal display device used for a notebook computer, a liquid crystal television, and the like. In addition, by placing a sign plate formed by cutting, printing, or the like on a translucent plastic plate such as a methacryl plate on the light emitting surface side of the surface light source element, a station, a public facility, etc. It can be used as a signage device such as a guide signboard, a large signboard, a traffic sign, and the like.

In the present invention, a general straight tube type fluorescent lamp can be used as the light source 2, but when it is difficult to replace the light source 2, a line light composed of a plurality of optical fibers is used. Light can also be transmitted from a separately installed light source.

[0018]

EXAMPLE 1 (Mold 1) The surface of a glass plate was made to have a particle size of 125 to 149.
μm glass beads (FGB-120 manufactured by Fuji Seisakusho)
The distance from the glass plate to the spray nozzle is 10
The blast treatment was performed at a spray pressure of 4 kg / cm ² . Thereafter, the blast surface was chemically etched by performing a hydrofluoric acid treatment, and a mold 1 was obtained by electroforming.

(Preparation of Surface Light Source Element) Using a mold 1, a rough surface was transferred by thermal transfer to one surface of an acrylic plate having a thickness of 3 mm, one side of 210 mm and the other side of 165 mm. A silver-deposited PET film is attached to two end faces of 165 mm and one end face of 210 mm of this plate by adhesion processing, and PET is deposited on a face opposite to the roughened light emission face.
The film was taped to form a reflective surface, which was used as a light guide A.

On a light exit surface of the light guide A, a light diverting sheet in which a number of prism rows having a head angle of 63 degrees and a pitch of 50 μm are formed on a PET film with an acrylic UV curable resin having a refractive index of 1.53 is formed by a prism. The prisms were arranged so that the surface faced the light emitting surface side of the light guide, and the prism rows were parallel to the cold cathode tubes. A PET film on which silver was deposited was used as a reflector. A cold cathode tube, a light guide, and a light deflection sheet were wound around one of the 210 mm sides by a reflector. At this time, a gray light shielding material with a width of 3 mm was placed between the reflector and the light diverting sheet, and a gray paint was placed on the transparent sheet with a width of 6 mm between the light guide and the reflection layer. A light shielding material printed so as to have a low transmittance was inserted to obtain a surface light source element 1. FIG. 2 shows the configuration of the members at the time of ramping. In the obtained surface light source element 1, the bright line was slightly visible.

Example 2 A light diverting sheet is provided on the surface opposite to the light guide surface of the light diverting sheet of Example 1 with a prism array having a vertex angle of 90 ° and a pitch of 50 μm, and a prism array formed of a cold cathode tube. A surface light source element 2 was formed in the same manner as in Example 1, except that the surface light source element 2 was formed at an angle of 90 degrees. In the obtained surface light source element 2, there was almost no glare.

Example 3 A light guide was formed on the surface opposite to the roughened surface of the light guide A, a prism array having a top angle of 90 ° and a pitch of 50 μm, and the prism array was inclined by 90 ° with respect to the cold cathode tube. A surface light source element 3 was formed in the same manner as in Example 1 except that the light source was formed as described above (light guide B). In the obtained surface light source element 3, there was almost no glare.

Example 4 A surface light source element 4 was formed in the same manner as in Example 4 except that the lamp installation position was changed to the center of the light guide as shown in FIG.
In the obtained surface light source element 4, the bright line was slightly visible.

Example 5 A surface light source element 5 was formed in the same manner as in Example 2, except that the shielding material between the light guide and the reflection layer was changed to a monochromatic gray sheet. In the obtained surface light source element 5, the dark band was slightly visible.

Comparative Example 1 A surface light source element 6 was prepared in the same manner as in Example 1 except that the structure of the member at the time of the lamp was as shown in FIG. In the obtained surface light source element, a bright line and a dark band were visible, so that it was not practical.

[0026]

According to the surface light source device of the present invention, a high quality surface light source device without glare can be provided by wrapping the light diverting sheet, the light guide and the reflection layer together with the light source with a reflector.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a surface light source element of the present invention.

FIG. 2 is a partial cross-sectional view illustrating a surface light source element according to Embodiment 1 of the present invention.

FIG. 3 is a partial sectional view showing a surface light source element according to a fourth embodiment of the present invention.

FIG. 4 is a partial cross-sectional view showing a surface light source element of Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide 2 Light source 3 Lens sheet 4 Reflection layer 5 Reflector 6 Light shielding material 7 Lower edge 8 Upper edge

Claims (7)

[Claims] 1. A light source, a light guide having a light incident surface facing the light source and a light exit surface substantially orthogonal to the light source, a reflective layer disposed on the opposite side of the exit surface, and the light guide A light diverting sheet formed by arranging a number of lens rows arranged in parallel on the light emitting surface side of the light diverting sheet, the light diverting sheet, the light guide, and the reflection layer are wrapped by a reflector together with the light source. A surface light source element characterized by the above-mentioned. 2. The surface light source device according to claim 1, wherein a light shielding material is provided between the light diverting sheet and the reflector, or between the light guide and the reflection layer, or both. 3. The surface light source device according to claim 1, wherein the light diverting sheet has a prism shape on the light guide side. 4. The surface light source device according to claim 1, wherein a lens row or a hairline that is substantially perpendicular to the lens row, or a minute uneven shape is provided on a surface of the light deflection sheet opposite to the lens row. 5. The surface light source element according to claim 1, wherein a lens array in a direction substantially perpendicular to the linear light source is provided on the light emitting surface of the light guide or on the opposite surface or both surfaces thereof. . 6. A light shielding material disposed between the light guide and the reflection layer, wherein the transmittance changes stepwise in a direction perpendicular to the linear light source,
3. The surface light source device according to claim 2, wherein a pattern is provided such that a light transmittance of a portion separated from the light incident surface of the light guide by the light guide thickness is minimized. 7. A light guide wherein minute unevenness is formed on one surface of the light guide, and the installation position of the linear light source is shifted away from the surface on which the fine unevenness is formed than the center of the light guide. The surface light source element according to claim 1, wherein: