JP2002196152A - Light guide for light source device, light source device using the same, and front light - Google Patents

Abstract

(57) [Summary] (With correction) [Problem] To irradiate satisfactorily with high utilization efficiency, improve display performance by light emitted from an illuminated body, and reduce contrast due to surface damage and external light. To provide a light guide capable of suppressing the occurrence of light. SOLUTION: At least one side end surface is a light incident surface 1a.
A light guide for a rectangular light source device, wherein one of two main surfaces substantially orthogonal to the light incident surface 1a is a light emitting surface 1c.
A light guide for a light source device, wherein a number of columnar bodies 4 having inclined surfaces 4a and 4b on the light incident surface side are intermittently arranged inside the light guide 1 in a manner substantially parallel to the light incident surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a notebook computer,
Liquid crystal display devices used for mobile electronic devices such as liquid crystal televisions, mobile phones, personal digital assistants, etc., guide signs and large signs at stations and public facilities, and traffic guides and signs on expressways and general roads. The present invention belongs to the technical field of a light source device such as a surface light source device used for a marking device, a rod-shaped light source device that converts a light source such as an LED into a uniform linear light source, and in particular, a light guide for the light source device and And a front light (front light source device) using the same.

[0002]

2. Description of the Related Art
As a front light used to illuminate a liquid crystal display device, a signboard, a traffic guide plate, and the like from the front side, a so-called edge light type light source device that is advantageous in reducing the weight and thickness of the device has been proposed. In recent years, there has been an increasing demand for mobile electronic devices such as mobile phones, personal digital assistants, electronic organizers, and portable game devices. The development of the following small and ultra-thin products is desired.

In an edge light type front light,
For example, as described in JP-A-8-94444, a primary light source disposed adjacent to a side end surface of a plate-shaped light guide is introduced into the light guide and guided inside the light guide. The reflected light is reflected by a prism array formed on one surface of the light guide, and a liquid crystal display (LED) or the like is directed in the direction normal to the surface of the light guide through the other flat surface. Irradiates toward the illuminated object. The light reflected by the illuminated object passes through the flat surface of the light guide and the surface on which the prism array is formed in this order, exits from the surface on which the prism array is formed, and travels toward the observer.

As described above, in the edge light type front light, the prism array formed on the observation side surface of the light guide exerts a function of directing light from the primary light source toward the illuminated object. Since it is necessary, it has a prism surface inclined with respect to the flat surface of the light guide. Therefore, when observing light from the illuminated object through the light guide, as a result of the refraction by the prism array, it is not possible to observe an appropriate image of the illuminated object, There was a drawback that the display was not sufficiently high in quality due to blurring.

[0005] By appropriately setting the inclination angle of the prism surface of the prism array, it is possible to minimize the above-described deterioration of the display performance as much as possible. However, such an inclination angle illuminates the primary light source light. It does not always coincide with the prism surface inclination angle for efficiently heading toward the body (that is, improving the use efficiency of illumination light). Therefore, it is difficult to realize both the improvement of the use efficiency of the illumination light and the improvement of the display performance, and the restrictions on the optical design also increase.

Further, as described above, since the prism array forming surface of the light guide is located closest to the observation side, scratches due to contact are likely to occur, and surface reflection on the observation side surface adversely affects display performance. give. For this reason, it is preferable to apply a hard coat or an anti-reflection film for preventing damage to the observation side surface, but it is technically difficult to apply a surface treatment to the non-flat prism array forming surface. .

Therefore, the present invention provides an edge light type front light which irradiates light emitted from a primary light source as illumination light to an illuminated object with high utilization efficiency, and displays an image by the light emitted from the illuminated object. The purpose is to improve performance. Another object of the present invention is to provide an improved light guide for realizing such a front light. A further object of the present invention is to provide an improved light guide that can realize the above-described front light and that can easily perform surface treatment on the surface on the observation side.

[0008]

That is, in the light guide for a light source device of the present invention, at least one side end surface is a light incident surface, and one of two main surfaces substantially orthogonal to the light incident surface emits light. A planar light guide for a light source device having a surface, wherein a number of columnar bodies having an inclined surface on the light incident surface side are intermittently arranged substantially parallel to the light incident surface inside the light guide. It is characterized by having. The light guide for a light source device of the present invention is a light guide for a flat light source device in which at least one side end surface is a light incident surface and one of two main surfaces substantially orthogonal to the light incident surface is a light emitting surface. A light guide, wherein a large number of columnar bodies having an inclined surface on the light incident surface side are intermittently arranged in a substantially arc shape concave on the light incident surface side inside the light guide. It is a feature.

Further, the light source device of the present invention includes the light guide for the light source device as described above, and a primary light source disposed adjacent to an end face of the light guide member, and the primary light source emits light. Is arranged on at least one side end surface of the light guide so that the light enters the end surface of the light guide. Further, a front light of the present invention includes the light guide for a light source device as described above, and a primary light source disposed adjacent to an end face of the light guide member, and the primary light source guides the emitted light to the light guide. The light guide is disposed on at least one side end face of the light guide so as to be incident on the end face of the light guide, and light incident on the light guide from the primary light source exits from a main surface serving as a back surface of the light guide. It is characterized by the following.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing one embodiment of a light guide for a light source device and a front light using the same according to the present invention. In FIG. 1, reference numeral 2 denotes a primary light source. As the primary light source 2, a self-luminous light source such as a cold-cathode tube, a fluorescent tube, an LED, and an LED array can be used. Reference numeral 1 denotes a plate-shaped light guide as a whole, which is a methacrylic resin, an acrylic resin, a polycarbonate resin,
Using various synthetic resins having high transparency such as a cyclic polyolefin resin and a vinyl chloride resin, the resin can be produced by an ordinary molding method such as extrusion molding and injection molding. 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 the content of methyl methacrylate is preferably 80% by weight or more. Also, 3
Is a reflection type liquid crystal display (LCD) as an illuminated body disposed below the light guide 1.

As shown in FIG. 1, a light guide 1 according to the present invention has a light incident surface 1a on which a primary light source 2 is disposed facing, and two main surfaces 1b and 1c substantially orthogonal to the light incident surface 1a. And one main surface 1c is a light emitting surface for emitting light incident on the light guide 1 from the primary light source.

In the present invention, a large number of columnar bodies 4 having inclined surfaces on the light emitting surface side of the light guide 1 are formed intermittently inside the light guide 1. The cross-sectional shape of the columnar body 4 is such that an inclined surface for totally reflecting incident light incident on the light guide 1 from the primary light source in a specific direction and emitting the light from the light guide 1 has a light emitting surface of the light guide 1. Although it is not particularly limited as long as it has on the side, a cross-section having a substantially triangular shape as shown in FIG. 1 is preferable. The inclined surface on the light emitting surface side of the hollow light guide 4 may be a flat surface or a convex or concave curved surface. The columnar body 4 is formed intermittently on a plane perpendicular to the light entrance surface and the light exit surface of the light guide 1, but is formed intermittently even if it is formed continuously in the longitudinal direction. It may be.

When a linear light source such as a cold-cathode tube is used as the primary light source 2, the columnar body 4 is preferably formed so as to be substantially parallel to the light incident surface 1. Also,
When a point-like light source such as an LED is used as the primary light source 2, the primary light source 2 is formed in a substantially arc shape so as to surround the primary light source 2, that is, in a substantially arc shape that is concave on the light incident surface 1 a side of the light guide 1. It is preferable that the incident light propagating radially from the point light source 2 and the columnar body 4 be formed substantially orthogonally. In particular, when used for a display device having a relatively small screen size such as a mobile phone or a portable information terminal, it is preferable to use a small point light source such as an LED as the primary light source 2. In the present invention, the primary light source 2 is not only installed on one side end face of the first prism member 4 as shown in FIG. It can also be installed further.

Columnar body 4 formed on light guide 1 of the present invention
Is usually a space in which the inside is air, but may be filled with a translucent resin having a refractive index lower than the refractive index of the material constituting the light guide 1. The light-transmitting resin to be used is not particularly limited as long as it is light-transmitting and has a low refractive index. In order to emit light in a desired direction, a resin having a difference in refractive index from the resin constituting the light guide 1 is preferably 0.2 or more, and more preferably 0.4 or more.

As shown in FIG.
A first inclined surface 4a on the side near the light incident surface 1a of the light guide 1,
A second inclined surface 4b farther from the light incident surface 1a;
And a surface 4c parallel to the main surface of the first surface is preferably substantially triangular in cross section.

The first inclined surface 4a has an angle of 20 with respect to the plane 4c.
The angle (θa) is preferably in the range of 70 to 70 degrees, and more preferably in the range of 35 to 55 degrees. By setting the angle of the first inclined surface 4a to 20 degrees or more, the first inclined surface of the incident light reflected from the irradiation target such as the liquid crystal display element and incident on the light guide 1 again when used as a front light. 4a, the influence of the reflection / refraction action can be reduced, and a decrease in display characteristics can be suppressed. When the angle is set to 70 degrees or less, incident light from the primary light source can be efficiently totally reflected and emitted in a desired direction. On the other hand, the second
The inclined surface 4b preferably has an angle (θb) of 70 to 90 degrees with respect to the plane 4c, more preferably 80 to 90 degrees.
The range is 90 degrees. By setting the angle of the second inclined surface 4b to 70 degrees or more, the second inclined surface of the incident light reflected from the irradiated object such as the liquid crystal display element and incident on the light guide 1 again when used as a front light. 4b, the influence of the reflection / refractive action can be reduced, and the deterioration of the display characteristics can be suppressed. Further, by setting the angle to 90 degrees or less, the columnar body 4 can be easily formed.

The width of the columnar body 4 is not particularly limited, but is preferably 2 to 1000 μm, more preferably 2 to 20 μm. This is because the columnar body 4 can be easily formed by setting the width of the columnar body 4 to 2 μm or more. This is because the influence of the reflection and refraction of the incident light that has been reflected and reentered the light guide 1 by the columnar body 4 can be reduced, and the deterioration of the display characteristics can be suppressed.

Further, the distance between the adjacent columnar members 4 is gradually reduced as the distance from the light incident surface 1a is increased so that the light emitted from the light guide 1 has a uniform intensity on the light emitting surface. It is preferable that the height of the columnar body 4 be gradually increased as the distance from the light incident surface 1a increases.

As shown by an arrow in FIG. 1, light emitted from the primary light source 2 is incident on the light incident surface 4a of the light guide 4 located opposite to the primary light source 2, and Propagating in the body 4, the traveling direction is changed downward by the total internal reflection by the first inclined surface 4 a of the columnar body 4, and the back surface 1 of the light guide 1 is changed.
c, and illuminates the reflective LCD 3 as illumination light.

Image information is formed on the LCD 3, and the light carrying the image information (reflected light of the illumination light) becomes light traveling substantially in the normal direction of the main surface of the light guide 1, and is transmitted from the back surface 1 c. Light that reenters the light guide 1 and mainly passes through a portion where the columnar body 4 is not formed exits from the surface 1b of the light guide 1 in the normal direction. Further, the light hitting the columnar body 4 is totally internally reflected by the first inclined surface 4a or the second inclined surface 4b,
A part of the light guided through the light guide 1 is emitted from the back surface 1c of the light guide 1 and enters the light guide 1 again. It is preferable that the second inclined surface 4b of the columnar body 4 be perpendicular to the plane 4c from the viewpoint of the utilization efficiency of light totally internally reflected by the columnar body 4.

Since most of the light carrying the image information passing through the light guide 1 and exiting from the surface 1b of the light guide 1 is not refracted in the light guide 1, an image due to refraction is formed. There is no adverse effect on display performance.

As described above, in this embodiment, L
Since an image formed by light traveling from the CD 3 to the observation side via the light guide 1 is hardly affected by the inclined surface of the columnar body 4,
The inclination angles of the first inclined surface 4a and the second inclined surface 4b are
It can be designed to optimize the total internal reflection characteristics of the first inclined surface 4a toward the LCD 3. Thereby, both the improvement of the use efficiency of the light amount from the primary light source 2 and the improvement of the image display performance can be easily realized.

Further, the light guide 1 of the present invention has a surface 1
b is a flat surface, and a surface treatment layer such as a hard coat layer or an anti-reflection layer can be easily formed. Therefore, it is possible to prevent the surface on the observation side from being damaged, and to lower the contrast due to external light. Can also be suppressed. In the present invention, such a surface treatment layer can be easily applied not only to the front surface 1b of the light guide 1 but also to the back surface 1a.

Next, another embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 2, the light guide 1 is a first light guide member 1 on the back surface 1 a side having a columnar body 4.
1 and a second light guide member 12 arranged on the front side of the first light guide member and constituting the front surface 1b. The first light guide member 11 has a rectangular shape in which V-shaped grooves 4 for forming the columnar body 4 are formed in parallel on its surface. The second light guide member 12 is a flat plate-like member that can be laminated and integrated on the surface of the first light guide member 11 where the V-shaped groove 4 is formed via an adhesive or the like.

The first light guide member 11 and the second light guide member 12 preferably have a relatively small thickness of, for example, about 0.5 to 2 mm, and more preferably have a thickness T1 of the first light guide member 11.
Is 0.7 to 2 mm, and the thickness T2 of the second light guide member 12 is
Is 0.1 to 1 mm, which is thinner than the first light guide member 11. The first light guide member 11 and the second light guide member 12 are preferably made of the same translucent material. Even when they are made of different materials, the difference in the refractive index is preferably within 0.1, more preferably 0. .04 or less.

It should be noted that the light source device according to the above-described embodiment is perpendicular to the columnar body 4 as shown in FIG. 1 (that is, perpendicular to the primary light source 2) and parallel to each other and has an appropriate width (for example, A plurality of rod-shaped light sources can be obtained by cutting several into a plurality of cut surfaces positioned at every 5 times or less of the thickness). As such a rod-shaped light source, the primary light source 2 is L
An example using a small point light source such as an ED is exemplified.

[0027]

As described above, according to the present invention,
Since a columnar body having an inclined surface on the light incident surface side is formed in the light guide, the light emitted from the primary light source when a primary light source is arranged adjacent to the end surface of the light guide to constitute a front light Can be satisfactorily illuminated with high utilization efficiency as illumination light to the object to be illuminated, and display performance by light emitted from the object to be illuminated can be improved. Further, in the light guide of the present invention, since both main surfaces are flat surfaces, the formation of the surface treatment layer is facilitated, and it is possible to prevent the surface from being damaged and the contrast from being lowered by external light.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a light guide for a light source device according to the present invention and a front light using the same.

FIG. 2 is a schematic sectional view showing a light guide for a light source device and a front light using the same according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide 1 a light incident surface 1 b front surface 1 c back surface 2 primary light source 3 liquid crystal display element 4 columnar body 4 a first inclined surface 4 b second inclined surface 4 c plane 11 first light guide member 12 second light guide member

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F21Y 103: 00 F21Y 103: 00 F term (reference) 2H038 AA55 BA06 2H091 FA23X FA23Z FA41X FA41Z FA42Z FA43Z FA45Z FB02 KA01 KA10 LA17 5G435 AA02 BB12 BB16 EE22 FF08 GG23 GG24

Claims (18)

[Claims] 1. A flat light guide for a light source device, wherein at least one side end surface is a light incident surface, and one of two main surfaces substantially orthogonal to the light incident surface is a light exit surface. A light guide for a light source device, wherein a number of pillars having an inclined surface on the side of the light incident surface are intermittently arranged in the light body substantially parallel to the light incident surface. 2. A flat light guide for a light source device, wherein at least one side end surface is a light incident surface and one of two main surfaces substantially orthogonal to the light incident surface is a light emitting surface. A light guide for a light source device, wherein a number of columnar bodies having an inclined surface on the light incident surface side are intermittently arranged in a substantially arc shape concave on the light incident surface side inside the light body. body. 3. The light guide for a light source device according to claim 1, wherein the column has a substantially triangular cross section. 4. The light guide for a light source device according to claim 1, wherein the inside of the columnar body is a gap. 5. The light source according to claim 1, wherein a light-transmitting resin having a lower refractive index than a material forming the light guide is filled in the columnar body. Light guide for equipment. 6. The light guide for a light source device according to claim 5, wherein a refractive index of the light transmitting resin is smaller than a refractive index of the light guide member by 0.2 or more. 7. The light guide for a light source device according to claim 1, wherein the distance between the adjacent pillars decreases as the distance from the light incident surface increases. . 8. The light guide for a light source device according to claim 1, wherein the height of the columnar body increases as the distance from the light incident surface increases. 9. The columnar body has a first inclined surface closer to the light incident surface and a second inclined surface farther from the light incident surface, and the first inclined surface is the flat surface. 20-7 for
The light guide for a light source device according to any one of claims 1 to 8, wherein the second inclined surface forms an angle of 80 to 100 degrees with respect to the flat surface. Light body. 10. The width of the columnar body is 20 to 1000 μm.
The light guide for a light source device according to any one of claims 1 to 9, wherein 11. A flat first light guide member in which a plurality of V-shaped grooves having a substantially triangular cross section are formed in parallel on one surface, and a V-shaped light guide member of the first light guide member. The light guide for a light source device according to any one of claims 1 to 10, comprising: a second light guide member having a flat plate shape, which is laminated and integrated on the groove forming surface. 12. The method according to claim 12, wherein a refractive index of the first light guide member and the second light guide member are different from each other.
The light guide for a light source device according to claim 11, wherein a difference from a refractive index of the light guide member is within 0.02. 13. The light guide for a light source device according to claim 1, wherein a surface treatment layer is formed on at least one main surface of the light guide. 14. The light guide for a light source device according to claim 11, wherein a surface treatment layer is formed on at least one main surface of the second light guide member. 15. A light guide for a light source device according to claim 1, further comprising: a primary light source disposed adjacent to an end face of the light guide member, wherein the primary light source emits light emitted from the primary light source. A light source device, wherein the light source device is arranged on at least one side end surface of the light guide so as to be incident on an end surface of the light guide. 16. The light source device according to claim 15, wherein the primary light source is a linear light source. 17. The light source device according to claim 16, wherein the primary light source is a point light source. 18. A light guide for a light source device according to claim 1, further comprising a primary light source disposed adjacent to an end face of the light guide member, wherein the primary light source emits light emitted from the primary light source. The light guide is disposed on at least one side end face of the light guide so as to be incident on the end face of the light guide, and light incident on the light guide from the primary light source exits from a main surface serving as a back surface of the light guide. A front light characterized by: