JP2000066030A - Surface light source element - Google Patents

Abstract

(57) [Problem] To provide a surface light source element capable of obtaining high luminance and having excellent in-plane luminance uniformity. SOLUTION: The surface light source element of the present invention includes a light guide 3 having light sources 2 provided on both end surfaces 1, and an emission light control plate 4 for directing light from an emission surface in a front direction. The emission light control plate 4 is arranged on the light guide 3, and the light incident on the incident surface 5 is emitted from the emission surface 6. A large number of projections 7 are formed on the incident surface 5 of the emission light control plate 4, and the tips of the projections 7 are in close contact with the emission surface of the light guide 3 via the adhesive layer 8 or the adhesive layer. . At the center of the light guide, the height of the convex portion 7 is low, and the adhesive layer 8 has a high adhesion portion at a side closer to the end surface 1 and a small adhesion portion at a position away from the end surface.
On the other hand, on the end side of the light guide 3, the height of the projection 7 is high, and the adhesive layer 8 is thin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface light source element used for a personal computer, a computer monitor, a video camera, a television receiver, a car navigation system and the like.

[0002]

2. Description of the Related Art A transmissive display device typified by a liquid crystal panel is composed of a backlight which emits light in a plane and a display panel in which pixels are arranged in a dot form. Characters and images are displayed by controlling the transmittance. As the backlight, a combination of a halogen lamp, a reflector, a lens, and the like is used to control the luminance distribution of the emitted light. A fluorescent tube is provided on the end face of the light guide, and light from the fluorescent tube is perpendicular to the end face. And a fluorescent tube provided inside the light guide (direct type). A backlight using a halogen lamp is mainly used for a liquid crystal projector requiring high luminance. On the other hand, since a backlight using a light guide can be made thin, it is often used for a direct-view type liquid crystal TV, a display of a personal computer, and the like.

In a backlight used for a liquid crystal TV, a notebook personal computer, and the like, it is required to reduce power consumption and to have high luminance. Higher brightness can be realized by increasing the number of light sources such as cold cathode tubes, but this method is not practical because it leads to an increase in power consumption. Therefore, various surface light source elements have been developed to realize higher luminance. Japanese Patent Application Laid-Open No. 8-221003 discloses a first light guide 14 for transmitting light from a light source 13 reflected by a reflector 11 and incident from an end face 12 in a front direction, as shown in FIG. A backlight device including a second light guide 15 disposed on the surface of the light body 14 is shown. In this backlight device, a second light guide 15 having a function of extracting light is provided on a light guide plate, and an attempt is made to reduce light loss by using total reflection of light.

[0004]

In display displays such as a direct-view type liquid crystal TV and a personal computer display, it is also important that the luminance of the backlight is uniform within the plane in order to obtain high image quality. is there. In the backlight device described in Japanese Patent Application Laid-Open No. H08-221013, since light propagating in the light guide is sequentially extracted, the amount of light propagating decreases as the distance from the light source increases. In other words, there is a problem of in-plane luminance non-uniformity in which the luminance on the light source side is high and the luminance decreases as the distance from the light source increases.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a surface light source element which can obtain high luminance and has excellent in-plane luminance uniformity.

[0006]

According to the present invention, there is provided a surface light source device, comprising: a light source; a reflector; a light guide to which light from the light source reflected by the reflector is incident from an end face; An emission light control plate provided on the emission surface side of the light body and directing light from the light guide in the front direction, the emission light control plate having a plurality of convex portions on a surface facing the light guide. Having, the convex portion is in close contact with the emission surface of the light guide, and the ratio of the convex portion in close contact with the light guide is small in a portion close to the light source,
It is characterized in that it changes so as to become larger at a portion away from the light source. Here, for example, the distribution itself of the number of protrusions does not change in the emission light control plate surface, and the area of the portion where each protrusion of the emission light control plate is in close contact with the emission surface of the light guide is Either change the value so that it is small at the part close to the light source and large at the part distant from the light source, or change the number of projections of the emission light control plate so that it is small near the light source and large at the part distant from the light source By doing so, it is possible to change the ratio in which the convex portion is in close contact with the light guide in a portion close to the light source and large in a portion away from the light source. The convex portion has a function of introducing light that enters from the end face of the light guide, propagates inside the light guide, into the emission light control plate, and propagates the light by utilizing total reflection of the wall surface. .

[0007] The ratio of the convex portion of the emission light control plate in close contact with the light guide has an area large enough to include the contact portion with the plurality of convex portions in the exit surface of the light guide. Considering a minute portion, it can be obtained by calculating the ratio of the total area of the portion where the projection of the emission light control plate is in close contact with the light guide to the area of the minute portion. That is, referring to FIG. 1, when considering the A1 portion and the A2 portion having the same area, the total area of the contact portion between the convex portion indicated by a black circle and the light guide is A1.
By calculating the proportion of the area or the area of the area A2 to the area, the proportion of the protrusion of the emission light control plate in close contact with the light guide is obtained. In general, the proportion of the convex portion of the emission light control plate in close contact with the exit surface of the light guide in the region farthest from the light source is determined by the convex portion of the emission light control plate in the region near the end surface of the light guide. It is in the range of 30 to 95% of the ratio of being in close contact with the emission surface of the light body.

The projection of the emission light control plate and the emission surface of the light guide may be in close contact with each other via an adhesive layer or an adhesive layer.
Then, the ratio of the convex portion of the emission light control plate in close contact with the emission surface of the light guide may be changed stepwise or may be changed continuously. Further, the ratio of the convex portion of the emission light control plate in close contact with the emission surface of the light guide is also changed in a direction parallel to the light source, and in a portion where the brightness of the light source is high (for example, near the center of the light source). The ratio may be large in a portion where the luminance is low and the luminance of the light source is low (for example, near the end of the light source).

[0009]

FIG. 1 is a schematic diagram showing an example of a surface light source device according to the present invention. The surface light source element includes a light guide 3 having light sources 2 provided on both end surfaces 1 and an emission light control plate 4 for directing light from the light guide 3 in the front direction. The emission light control plate 4 is arranged on the light guide 3, and the light incident on the incident surface 5 is emitted from the emission surface 6. Incident surface 5 of emission light control plate 4
Are formed with a large number of projections 7, and as shown in FIG. 2B, the tip of the projection 7 and the emission surface of the light guide 3 via the adhesive layer 8 or the adhesive layer are point-shaped. Or, it adheres linearly. A reflector 8 is provided around the light source 2 for reflecting light traveling in the direction opposite to the end face of the light guide and traveling in the direction of the end face of the light guide.
Is provided. As shown in FIG. 1, the pressure-sensitive adhesive layer 8 or the adhesive layer has a thickness distribution in the plane of the light guide. That is, the height of the projection 7 is low at the center of the light guide,
On the other hand, on the end side of the light guide 3, the height of the projection 7 is high, and the adhesive layer 8 is thin. As a result, as shown in FIGS. 2A and 2B, the ratio of the contact portion is small (A1) on the side close to the end surface 1 and large (A2) at a position away from the end surface. Has changed in two stages. In the example shown in FIG. 2B, the distribution of the adhesion ratio is not given in a direction parallel to the end face 1 (in FIG. 1, the thickness direction of the paper). In the emission light control plate shown in FIG. 1, the distribution itself of the number of projections is not changed in the plane of the emission light control plate, but the number of projections of the emission light control plate is small in a portion close to the light source, and It can be changed so as to increase in a distant part. In the present invention, the inclination of the wall surface of the projection of the emission light control plate is preferably between 20 ° and 89 ° with respect to the emission surface of the light guide plate. More preferably, it is in the range of 30 ° to 89 °.

In this surface light source element, light incident from the end face 1 propagates inside the light guide 3 by repeating total reflection. The propagating light is taken into the emission light control plate 4 from the contact portion between the convex portion 7 and the light guide 3, and is emitted. Since a part of the light propagating in the light guide 3 is sequentially extracted at the contact portion, the amount of propagating light attenuates as the light propagates. When the ratio of the contact portion between the convex portion 7 and the light guide 3 is the same on the entire surface of the light guide, the amount of emitted light is also attenuated by the attenuation of the amount of propagation light.
Brightness non-uniformity occurs in the plane of the light guide. In the present invention, the ratio of the contact portion is small on the light source side and large at a location away from the light source, so that the attenuation of the light amount of the propagation light is canceled by increasing the extracted light amount, thereby achieving in-plane uniformity. Can be improved.

FIG. 3 is a schematic structural view of a second example of the surface light source element of the present invention. This surface light source element has a light source 2
Are provided, and the emission light control plate 4 is provided.
A large number of projections 7 are formed on the incident surface of the emission light control plate 4,
The light guide side end of the convex portion 7 and the light emitting surface of the light guide 3 are in close contact with each other. As shown in FIGS. 4A and 4B, the ratio of the contact portion between the convex portion 7 and the light guide 3 is small in a portion close to the light source 2 and large in a portion away from the light source 2. −A ′ direction (FIG. 3). In addition, in this case, in correspondence with the use of a fluorescent tube having a high luminance at the center and a low luminance near the end, the fluorescent tube is also adhered in a direction parallel to the end face 1 (BB 'direction shown in FIG. 3). There is a distribution such that the proportion of close contact is small near the center of the light source, which is a brighter part, and is large near the end of the light source, which is a darker part. I have. This makes it possible to reduce the in-plane luminance non-uniformity caused by the luminance unevenness of the light source. In the case where a fluorescent tube having a low luminance at the center and a high luminance near the ends is used, on the contrary, the contact portion ratio may be small near the light source end and large at the center. Further, when the luminance is high near one end of the fluorescent tube and the luminance is low near the other end, the ratio of the adhered portion near the high luminance end is reduced, and the luminance near the low luminance end is reduced. What is necessary is just to increase the ratio of the close contact part in. In any case, it is possible to reduce the non-uniformity of the luminance due to the luminance unevenness of the light source by changing the ratio of the contact portion in accordance with the luminance distribution of the fluorescent tube.

FIG. 5 is a schematic structural diagram of a third example of the surface light source element of the present invention. The surface light source element includes a light guide 3 having a light source 2 provided on one end surface 1 and an emission light control plate 4. A large number of projections 7 are formed on the incident surface of the emission light control plate 4, and the light guide side end of the projections 7 and the light emission surface of the light guide 3 are in close contact. As shown in FIGS. 6A and 6B, the area of the contact portion between the convex portion 7 and the light guide 3 is small in a portion close to the light source 2 and large in a portion away from the light source 2. Has changed. When the light source is provided only on one side of the light guide, the in-plane luminance uniformity is greatly reduced. The non-uniformity can be reduced by changing the contact ratio in three stages. In the surface light source element of the present invention, the light sources may be provided not only on the two end faces or one end face of the light guide as described above, but also on the four end faces of the light guide. .

In each of the above examples, the ratio of the contact portion is changed stepwise. However, FIGS. 7A and 7B show an example in which light sources are provided at both ends of the light guide and only one end of the light guide. As shown in FIGS. 8A and 8B in which a light source is provided, the thickness of the adhesive layer 8 or the adhesive layer is continuously changed so that the ratio of the contact portion is continuously changed. good.

FIG. 9 is a schematic structural diagram of a fourth example of the surface light source element of the present invention. This surface light source element has a light source 2
Are provided, and the emission light control plate 4 is provided.
A large number of projections 7 are formed on the incident surface of the emission light control plate 4,
A minute protrusion is provided on the top of the convex portion 7, and the light guide side end of the convex portion 7 and the light emitting surface of the light guide 3 are in close contact with each other. As shown in FIGS. 9A and 9B, the number of the protrusions is such that the ratio of the contact portion between the convex portion 7 and the light guide 3 is the light source 2.
Is small in a portion close to the light source 2 and is large in a portion distant from the light source 2.

FIG. 11 is a schematic structural diagram of a fifth example of the surface light source element of the present invention. This surface light source element includes a light guide 3 having light sources 2 provided on both end surfaces 1, and an emission light control plate 4. A large number of projections 7 are formed on the incident surface of the emission light control plate 4, and the light guide side tip and the light emission surface of the light guide 3 are in close contact with the fine projections at the tops of the projections 7. . FIG. 12 (a)
And (b), the ratio of the contact portion between the convex portion 7 and the light guide 3 is small in a portion close to the light source 2 and large in a portion away from the light source 2 (A-A 'direction ( FIG.
It has changed in 1). In addition, there is also a distribution of the ratio of the contact portion in a direction parallel to the end surface 1 (direction BB ′ shown in FIG. 11), and the ratio of the contact portion increases near the center of the light source, which is a brighter portion. As described above, in the vicinity of the end portion of the light source, which is a darker portion, the distribution of the contact portions is provided so that the ratio of the contact portions becomes small. This makes it possible to reduce the in-plane luminance non-uniformity caused by the luminance unevenness of the light source.

FIG. 13 is a schematic structural diagram of a sixth example of the surface light source element of the present invention. This surface light source element includes a light guide 3 having a light source 2 provided on one end surface 1 and an emission light control plate 4. A large number of projections 7 are formed on the incident surface of the emission light control plate 4, and fine projections at the tops of the projections 7 cause the light guide side tip of the projections 7 and the light emission of the light guide 3. The surface is in close contact. As shown in FIGS. 14A and 14B, the ratio of the contact portion between the convex portion 7 and the light guide 3 is small in a portion close to the light source 2 and large in a portion away from the light source 2. Has changed. In this example, the distribution of the close contact ratio is not given in a direction parallel to the end surface 1 (the thickness direction of the paper in FIG. 12). When the light source is provided only on one side of the light guide, the in-plane luminance uniformity is greatly reduced. The unevenness can be reduced by changing the adhesion ratio in three stages.

In the present invention, for example, an acrylic plate having a thickness of about 2 to 20 mm can be used as the light guide.
The distance between the light guide end faces where the light sources are arranged is, for example, 50 to 5
00 mm. When a surface light source element is formed by combining such a light guide and an emission light control plate in such a manner that the ratio of the contact portion becomes uniform over the entire surface, the uniformity (minimum) in the plane of the surface light source element is reduced. Luminance / maximum luminance) is usually 40
%. Here, according to the present invention, for example, for a light guide having a width (length in a direction parallel to the light source) of 250 mm and a distance between both end faces on the light source side of 190 mm, an area extending from the light guide end face to 15 mm. Is 60% of the close contact ratio of the central portion, and the convex portion is in close contact with the emission surface of the light guide such that the close contact ratio of the region from 15 mm to 50 mm is 80% of the close contact ratio of the central portion. By varying the proportion of the portions, the degree of uniformity can be improved to about 80%. Examples of the resin used for molding the light guide include not only acrylic resin but also polycarbonate resin, polystyrene resin and the like having excellent transparency.

The projection on the surface of the emission light control plate is formed by a hot pressing method,
It can be formed by a 2P method using ultraviolet curing, a 2P method using thermal curing, an injection molding method using a female mold, or the like.
The stamper used for producing the emission light control plate is, for example, to coat a negative or positive photosensitive resin on a glass substrate, expose the photosensitive resin through a photomask, and perform electroforming after development. Can be produced. The emission light control plate does not need to be plate-shaped, but may be sheet-shaped. Both the plate shape and the sheet shape are rich in mass productivity, so that they can be manufactured inexpensively and in large quantities. The inclination of the slope of the projection of the emission light control plate does not necessarily have to be symmetrical in the left, right, up and down directions, and the inclination angle may be changed in the left, right, up and down directions.

The above-described surface light source element is used as a backlight, and a transmissive display element provided on an emission surface thereof includes a liquid crystal panel such as an STN, a TFT, and a MINI.

[0020]

According to the present invention, there is provided a surface light source element having high luminance and excellent in-plane luminance uniformity.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one example of a surface light source element of the present invention.

FIG. 2 is a diagram showing an example of a distribution of an area of a contact portion in the surface light source element of the present invention.

FIG. 3 is a schematic configuration diagram of a second example of the surface light source element of the present invention.

FIG. 4 is a diagram showing a second example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 5 is a schematic configuration diagram of a third example of the surface light source element of the present invention.

FIG. 6 is a diagram showing a third example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 7 is a diagram showing another example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 8 is a diagram showing another example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 9 is a schematic configuration diagram of a fourth example of the surface light source element of the present invention.

FIG. 10 is a diagram showing a fourth example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 11 is a schematic configuration diagram of a fifth example of the surface light source element of the present invention.

FIG. 12 is a diagram showing a fifth example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 13 is a schematic configuration diagram of a sixth example of the surface light source element of the present invention.

FIG. 14 is a diagram showing a sixth example of the area distribution of the contact portion in the surface light source element of the present invention.

FIG. 15 is a schematic configuration diagram of a conventional backlight device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide end surface 2 ... Light source 3 ... Light guide 4 ... Outgoing light control plate 5 ... Outgoing light control plate incident surface 6 ... Outgoing light control plate outgoing surface 7 ... Convex part 8 ... Reflector

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoichi Hashimoto 41 Miyukigaoka, Tsukuba, Ibaraki Prefecture Kuraray Co., Ltd. F-term (reference) 2H038 AA55 BA01 BA06

Claims (8)

[Claims] 1. A light source, a reflector, and a light guide into which light from the light source reflected by the reflector is incident from an end face,
An emission light control plate that is provided on the emission surface side of the light guide and directs light from the light guide in the front direction, wherein the emission light control plate has a plurality of projections on a surface facing the light guide. The convex portion is in close contact with the emission surface of the light guide, and the ratio of the convex portion in close contact with the light guide is small in a portion close to the light source, and large in a portion away from the light source. A surface light source element characterized by being changed as follows. 2. The area of a portion where each projection of the emission light control plate is in close contact with the emission surface of the light guide changes so as to be small near the light source and large at a portion away from the light source. The surface light source element according to claim 1, wherein 3. The surface light source device according to claim 1, wherein the number of projections of the emission light control plate changes so as to be small in a portion near the light source and large in a portion far from the light source. 4. The projection of the emission light control plate and the emission surface of the light guide are in close contact with each other via an adhesive layer or an adhesive layer, and the thickness of the adhesive layer or the adhesive layer is small at a portion near the light source, 2. The surface light source device according to claim 1, wherein the surface light source element changes so as to become thicker at a portion away from the light source. 5. The surface light source device according to claim 1, wherein the ratio of the protrusion of the emission light control plate in close contact with the emission surface of the light guide changes stepwise. 6. The surface light source device according to claim 1, wherein the ratio of the protrusion of the emission light control plate in close contact with the emission surface of the light guide changes continuously. 7. A ratio in which the projection of the emission light control plate is in close contact with the emission surface of the light guide changes in a direction parallel to the light source, and the ratio is small in a portion where the luminance of the light source is high. 2. The surface light source device according to claim 1, wherein the ratio is large in a portion where the luminance of the light source is low. 8. A ratio of the convex portion of the emission light control plate in close contact with the emission surface of the light guide in a region near the end surface of the light guide,
2. The surface light source element according to claim 1, wherein the ratio of the protrusion of the emission light control plate in the region farthest from the light source to the emission surface of the light guide is in the range of 30 to 95%.