WO2008047442A1

WO2008047442A1 - Surface light source device

Info

Publication number: WO2008047442A1
Application number: PCT/JP2006/320898
Authority: WO
Inventors: Yukihiro Hyobu; Nobuyuki Kasama
Original assignee: Miraial Co., Ltd.
Priority date: 2006-10-20
Filing date: 2006-10-20
Publication date: 2008-04-24

Abstract

In a surface light source device, a light incoming section (14) is arranged at least on the front surface or the rear surface of a light guide plate (11), close to the periphery of a region not overlapping a light outputting surface section (12). Light incoming section prism groups (15, 15') for having light entered from a light source (13) travel in a direction for total reflection at a light guide section (16) are arranged at least on a light incoming surface of the light incoming section (14) or a surface on the rear side of the light incoming surface by being formed of the light guide plate (11) itself. As a result, even when the light guide plate (11) is formed extremely thin, light of a sufficient quantity can be inputted to the light guide plate (11) from an external light source (13).

Description

Surface light source device

Technical field

The present invention relates to a surface light source device used for a backlight of a liquid crystal display device.

Background art

[0002] In a surface light source device used for a backlight of a liquid crystal display device, etc., it is a surface where light intensity is distributed uniformly, such as a plurality of LEDs (light emitting diodes). It needs to be converted to a light source.

[0003] Such surface light source devices include a direct illumination type and a side light type (also referred to as side emitting type). The direct type generally has a large number of light sources arranged between a transparent plate on which a scattering pattern or the like is formed and a flat reflecting sheet arranged opposite to the back surface, and the surface of the transparent plate is the surface. It becomes a light source (for example, Patent Document 1).

[0004] The sidelight type generally has a light source disposed facing a thin end surface perpendicular to the surface of a transparent light guide plate or the like, and light that has entered a thin end surface force into the light guide plate is guided. After being totally reflected and propagated in the optical plate, the light exit surface force on which a scattering pattern or the like is formed is emitted outward (for example, Patent Document 2).

Patent Document 1: JP-A-2006-228698 (P2006-228698A)

Patent Document 2: JP 2006-154292 (P2006-154292A)

Disclosure of the invention

Problems to be solved by the invention

[0005] The direct type surface light source device has the advantage that it can be easily brightened by increasing the number of light sources, and is suitable for use in a large-screen liquid crystal display device or the like. However, since the light source is arranged in the gap between the transparent plate and the reflective sheet, it is inevitable that the thickness will increase. Therefore, the direct-type surface light source device is suitable as a surface light source for devices that are required to be as thin as possible, such as an image display device of a digital camera!

[0006] On the other hand, a sidelight type surface light source device can be configured to be very thin as compared to a direct type surface light source device. However, the thinner the light guide plate, the more light source to light guide plate When light is incident on the light guide, the amount of light leaking increases and the amount of light entering the light guide plate decreases. Therefore, it is practically difficult to make the thickness of the sidelight type surface light source device as thin as a certain level.

[0007] An object of the present invention is to allow a sufficient amount of light to be incident on the light guide plate of the external light source even if the thickness of the light guide plate is very thin. As a result, the thickness of the device can be reduced. It is an object of the present invention to provide a surface light source device that can be made thinner than the sidelight type devices described above.

Means for solving the problem

[0008] In order to achieve the above object, a surface light source device of the present invention includes a light incident part (14) for causing one or a plurality of light sources (13) to emit emitted light, and a light incident part ( 14) Force Light guiding part (16) for propagating the incident light by totally reflecting it on the uniform flat inner surface, and light emission for emitting the light that has passed through the light guiding part (16) to the outside In the surface light source device having the transparent flat light guide plate (11) formed with the surface portion (12), the light incident portion (14) is at least one of the front and back surfaces of the light guide plate (11). Light incident on the light source (13) near the edge of the area that does not overlap the light exit surface (12) to allow the light incident on the light source (13) to be totally reflected by the light guide (16) Partial prism group (15, 15 ′) force The light guide plate (11) itself is formed and arranged on at least one of the light incident surface and the back surface of the light incident portion (14).

[0009] The light incident portion prism group (15) may be formed so as to protrude from the surface of the light guide plate (11) in the surrounding area. It is also possible to form a recess against the surface of the light guide plate (11) in the surrounding area!

[0010] The light source (13) force is emitted even if the light incident part prism group (15) may be disposed only on the surface where the emitted light is incident on the light guide plate (11). The light incident portion prism group (15 ^) may be disposed only on the surface behind the surface on which the incident light enters the light guide plate (11). Alternatively, even if the light incident portion prism groups (15, 15 ′) are arranged on both the surface on the side where the light emitted from the light source (13) is incident on the light guide plate (11) and the surface on the back side thereof, Good.

[0011] The light incident portion prism group (15, 15 ') may be composed of one or a plurality of horizontally long prisms that cross the light guide plate (11). , 15 ') Each prism force constituting the light source (13) force may be formed in an arc shape centered on the position where the optical axis of the emitted light beam passes and arranged concentrically. [0012] Further, the light incident portion prism group (15, 15 ') may be composed of a large number of independent microprisms arranged with a space between each other. (13) At a position far from the light source (13), the distance between the light sources (13) may be narrower than the position closer to the light source.

In addition, a light reflection sheet (19) may be disposed near the light incident part (14) so as to face the surface on which light emitted from the light source (13) is incident. (13) Force The light reflecting sheet (18) may be disposed so as to face the surface on the back side of the surface on which the emitted light is incident. The invention's effect

[0014] According to the present invention, the light incident part is provided in the vicinity of the edge of the region that is at least one of the front and back surfaces of the light guide plate and does not overlap the light emission surface part, and guides the light incident from the light source. The light incident part prism group for making it advance in the direction of total reflection at the part is formed and arranged by the light guide plate itself on at least one of the light incident surface and the back side of the light incident part. Even if the thickness of the light guide plate is very thin, a sufficient amount of light can be incident on the light guide plate in addition to the external light source power. As a result, the thickness of the surface light source device can be reduced to the existing sidelight. It can be made thinner than the mold type device.

Brief Description of Drawings

FIG. 1 is an exploded perspective view schematically showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a side sectional view schematically showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a side sectional view of the surface light source device according to the embodiment of the present invention.

FIG. 4 is a perspective view of a modified example near the light source of the surface light source device according to the embodiment of the present invention.

FIG. 5 is a side sectional view of various modifications of the light incident portion prism group according to the embodiment of the present invention.

FIG. 6 is a side sectional view of another modification of the light incident section prism group according to the embodiment of the present invention.

FIG. 7 is a side sectional view of another modification of the light incident section prism group according to the embodiment of the present invention.

FIG. 8 is a side sectional view of another modification of the light incident section prism group according to the embodiment of the present invention. FIG. 9 is a front view of another modification of the light incident section prism group according to the embodiment of the present invention.

FIG. 10 is a front view of another modification of the light incident section prism group according to the embodiment of the present invention.

FIG. 11 is a rear view of various modifications of the light emission surface portion according to the embodiment of the present invention. Explanation of symbols

[0016] 10 surface light source device

11 Light guide plate

12 Light exit surface

13 Light source

14 Light receiving part

15 Light entrance prism group (for incident)

15 'Light incident part prism group (for reflection)

16 Light guide

18 Backside reflective sheet

19 Front reflective sheet

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are an exploded perspective view and a side sectional view schematically showing a liquid crystal display device using the surface light source device 10 of the present invention. 1 and 2, the upper side is the front side of the liquid crystal display device, and the lower side is the back side. The surface light source device 10 of the present invention may be used for devices other than the liquid crystal display device.

The entire liquid crystal display device is supported by the support frame 1, and the liquid crystal panel 2 is disposed on the surface portion. A pair of prism sheets 3 and 4 for refracting light coming from the back side of the liquid crystal panel 2 so that the liquid crystal panel 2 faces the direction perpendicular to the surface of the liquid crystal panel 2 are arranged at positions facing the back surface of the liquid crystal panel 2. Yes. The pair of prism sheets are arranged in a state in which the directions of a large number of prism rows formed in parallel with each other are 90 ° different from each other!

The surface light source device 10 is arranged at the back side position of such a pair of prism sheets 3 and 4. 11 is a rectangular light guide plate made of a transparent plastic material such as polycarbonate resin, acrylic resin, or cyclic olefin resin, and is formed into a thin flat plate as a whole. Note that it is preferable to use an optical plastic material having a large refractive index because light leakage is reduced.

[0020] Of the entire surface of the light guide plate 11, the surface facing the back surface of the prism sheets 3 and 4 (for example, an area of about 70 to 90% of the entire surface) is directed toward the prism sheets 3 and 4 to transmit light. It is a planar light exit surface 12 that emits light. In FIG. 1, a region surrounded by a broken line is the light emission surface portion 12.

[0021] Then, the light incident part 14 for allowing the light emitted from the light source 13 arranged outside to enter the light guide plate 11 is an area where the light emission surface part 12 near the edge of the light guide plate 11 does not overlap. It is provided on the front side.

[0022] In the light incident portion 14 provided along the short side of the light guide plate 11 formed in a rectangular shape, a light incident portion prism group (for incidence) 15 formed by arranging a plurality of horizontally long prisms in parallel. Is placed. Each prism constituting the light incident portion prism group (for incident) 15 is formed in a straight shape that crosses the light guide plate 11 over the entire width in parallel with the short side of the light guide plate 11.

[0023] In addition, a light incident portion prism group (for reflection) 15 'that reflects light incident on the light guide plate 11 from the light incident portion 14 has a full width on the surface on the back side of the light incident portion 14. It is formed in a straight shape that crosses over.

A region between the light incident portion 14 and the light exit surface portion 12 of the light guide plate 11 is a light guide portion 16 that guides light incident from the light incident portion 14 to the light exit surface portion 12. Then, the light power that passes through the light incident portion prism groups 15 and 15 ′ and proceeds in the direction of total reflection at the light guide portion 16 is totally reflected by the uniform planar inner surface of the light guide plate 11. As a result, the light is transmitted toward the light exit surface portion 12 with a direct force.

As the light source 13, a plurality of LEDs are arranged side by side so that light enters the light incident portion 14 obliquely. Each light source 13 is mounted and arranged on a substrate 17 as shown in FIG. As the light source 13, a light source other than LED may be used.

In addition, a thin plate-like back side reflection sheet 18 is disposed so as to face the entire back surface of the light guide plate 11 and reflect light leaked from the light guide plate 11 to the back side and return it to the light guide plate 11. The More In addition, a front-side reflection sheet 19 that also reflects the light leaked to the surface side of the light incident portion 14 and returns it to the light guide plate 11 is disposed to face the surface of the light incident portion 14. With such a configuration, it is possible to reduce a light amount loss due to light leakage from the light guide plate 11. The front reflecting sheet 19 is arranged so that the force of the light incident portion 14 is not exposed to the force light emitting surface portion 12 disposed over the light guide portion 16.

FIG. 3 shows the surface light source device 10 and some optical paths. In this embodiment, all the prisms constituting the light incident portion prism group (incident) 15 arranged in the light incident portion 14 are formed at an apex angle of 90 °. The light emitted obliquely from the light source 13 to the light incident portion 14 is refracted by the light incident portion prism group (for incident) 15 (the light incident at right angles to the prism surface is not refracted), and Most of the light enters the light guide plate 11 at an angle at which the light guide unit 16 totally reflects the light.

[0028] The light incident part prism group (for incident) 15 is integrally formed so as to protrude from the surface of the light guide plate 11 in the surrounding area by the light guide plate 11 itself. By providing multiple small prisms as 15, the height of each prism can be reduced.

[0029] Light entrance prism group (for incidence) Even if it passes through 15, it does not turn in the direction of total reflection within light guide plate 11. The light entrance has a surface inclined with respect to the back surface of light guide plate 11 in the light path. A prism group (for reflection) 15 'is formed and arranged with the light guide plate 11 itself.

The path of the light totally reflected by the light incident part prism group (for reflection) 15 ′ is changed in the direction in which it is totally reflected by the light guide part 16 in the light guide plate 11. Also, a small amount of light leaks out of the light guide plate 11 at the front surface or back surface of the light incident portion 14. Most of such light leakage is reflected by the back-side reflection sheet 18 or the front-side reflection sheet 19 and is guided by the light guide plate. Returned within 11.

[0031] The light exit surface 12 that emits light from within the light guide plate 11 may have any configuration as long as the light that has been propagated by being totally reflected inside the light guide 16 is emitted outward. There is no problem. The light emission surface portion 12 of this embodiment has a configuration in which, for example, a large number of diffuse reflection portions 20 that diffusely reflect light within the light guide plate 11 are formed on the back surface portion of the light guide plate 11 at appropriate intervals. The diffuse reflection section 20 can be configured by forming a reflective coating or the like on a diffusion surface where unevenness is formed. In the surface light source device of this embodiment, the light is repeatedly reflected in the light guide plate 11 in a smaller proportion of the light traveling in the light guide plate 11 in the direction parallel to the surface than in the sidelight type device. The ratio of light that propagates back increases.

[0033] Therefore, by making the region between the diffusely reflecting portions 20 dispersedly arranged a flat total reflection surface, the light emission surface portion 12 partially functions as the light guide portion 16, and thus the light emission surface portion. Although light reaches all 12 regions, such a diffuse reflection part 20 and the like can be arranged more sparsely than in the case of the sidelight type, so that the light guide plate 11 can be easily manufactured and the manufacturing cost can be reduced. it can. In addition, by arranging the diffuse reflection portions 20 closer to a position farther from the light incident portion 14, the density of the emitted light beam can be made uniform even for the entire light exit surface portion 12.

With such a configuration, the light propagated in the light guide unit 16 is diffusely reflected by the diffuse reflection unit 20 and emitted from the surface of the light guide plate 11. The diffuse reflection portion 20 may be formed on the entire back surface of the light exit surface portion 12.

Further, by providing a transparent light diffusing surface or a prism group or the like instead of the diffusive reflecting portion 20, light is emitted in the back direction of the light guide plate 11, and is further reflected by the back-side reflecting sheet 18. However, it may be emitted through the light guide plate 11 with an upward force.

With such a configuration, in the surface light source device 10 of this embodiment, the light incident portion 14 is provided on the surface portion of the light guide plate 11 at a position that does not overlap the light emission surface portion 12. Therefore, even if the light guide plate 11 is thinly formed, a sufficient amount of light can enter the light guide plate 11 and be emitted from the light emission surface portion 12, and a thin and bright surface light source device can be realized. .

Note that the present invention is not limited to the above-described embodiment. For example, as shown in FIG. 4, the light guide rod 22 having a plurality of light emitting prisms 21 formed side by side on the bottom surface. One or a plurality of light sources 13 may be disposed so as to face the side surface, and the light emitting prism 21 of the light guide rod 22 may be disposed toward the light incident portion 14 of the light guide plate 11.

In such a configuration, the light emitted from the light source 13 travels while being totally reflected in the light guide rod 22, and is directed and radiated from the light emitting prism 21 to the light incident portion 14. . Further, instead of such a configuration, one or a plurality of rod-shaped LEDs or the like may be used as the light source 13.

Further, as shown in FIG. 5, depending on the incident angle of light from the light source 13 to the light incident portion 14, a light incident portion prism group (for reflection) 15 ′ is provided on the back side of the light guide plate 11. Nagu light incident part 14 side The incident light prism group (for incidence) 15 may be provided only on the surface of the light incident portion. In that case, the apex angle of all the prisms may be formed constant at about 90 ° (A), or the apex angle may be formed at about 45 ° (B) or other angles! / ,.

[0040] When the light guide plate 11 has a thickness, the light incident portion prism group (for incident) 15 may be formed in a recessed state with respect to the surface of the light guide plate 11 in the surrounding area. C), (D). With this configuration, the thickness of the light guide plate 11 does not increase as a whole, and manufacturing is easy.

Further, as shown in FIG. 6, by appropriately changing the apex angles of the prisms of the light incident portion prism group (incident) 15 formed in the light incident portion 14, the light incident portion prism group ( (For incidence) It is possible to make the direction in which most or all of the light incident on the light guide plate 11 from 15 is totally reflected in the light guide plate 11.

In addition, as shown in FIG. 7, the light incident portion prism group (for incident) 15 is not formed on the front surface side of the light incident portion 14, and light is incident only on the position corresponding to the back surface of the light incident portion 14. A partial prism group (for reflection) 15 ′ may be formed. The light incident portion prism group (for reflection) 1 is configured by arranging a plurality of horizontally long prisms that cross the light guide plate 11 in parallel. In this case, the surface of the light incident portion 14 is a simple plane.

[0043] In such a configuration, the light emitted from the light source 13 is bent into the light guide plate 11 from the light incident portion 14, and is totally reflected by the light incident portion prism group (for reflection) 15 'on the back surface. The light is reflected and returned into the light guide plate 11, and proceeds through the light guide plate 11 while being totally reflected by the light guide unit 16. Such a configuration is particularly effective when the light guide plate 11 is very thin.

[0044] It should be noted that a non-reflective coating or the like may be formed on the surface of the light incident portion 14 in order to reduce the light amount loss of incident light due to surface reflection. Such an antireflective coating can be formed of a known inductor multilayer film (including a single layer film of a low refractive index material), a subwavelength grating, or the like.

Further, in the present invention, as shown in FIG. 8, the light incident portion 14 on the front side of the light guide plate 11 in which the light incident portion prism group (for reflection) 15 ^ is formed on the rear surface side is incident on the light incident portion 14. As the optical section prism group (for incident) 15, a configuration may be adopted in which a plurality of prisms are arranged with an interval between each other. With such a configuration, the light incident efficiency to the light guide plate 11 may be increased. Further, as shown in FIG. 9, each prism constituting the light incident portion prism group (for incident) 15 has an arc shape centered on the position where the optical axis 23 of the light beam emitted from the light source 13 passes. And may be arranged concentrically.

With such a configuration, it becomes possible to align the incident angle of light with respect to the prism surface to approximately the target angle, to reduce the incident loss, and the direction of the light toward the light guide unit 16. May be easily aligned in the direction of total reflection, and light leakage may be reduced.

Further, as shown in FIG. 10, the light incident portion prism group (for incident) 15 forces may be constituted by a large number of independent microprisms arranged with a space between each other. With such a configuration, brightness unevenness may be eliminated.

[0049] In addition, a large number of micro-prism forces are arranged at positions far from the light source 13 at a smaller distance from the positions closer to the light source 13, thereby reducing the density of the light beam incident on the light guide plate 11. It may be possible to make it uniform.

[0050] In the present invention, the light source 13 and the light incident portion 14 may be provided on the back side of the light guide plate 11, or may be provided on both the front and back surfaces. Further, as described above, the light exit surface portion 12 may have any appropriate configuration. However, as shown in FIG. 11, the light guide plate 11 is provided in the same manner as the light incident portion prism group (for incident) 15. A prism group that also has a plurality of straight prism forces traversing the entire width may be provided on the back side (E). Then, the interval between the prisms may be made narrower as the position is farther from the light incident portion 14, and the emission density of the light beam may be made uniform (F).

[0051] In addition, a large number of independent microprisms arranged on the light exit surface 12 with a space between each other may be formed on the back surface side (G), and a large number of microprisms may be formed on the light incident portion. It is possible that the distance between them is arranged at a position farther from 14 than the position closer to the light incident portion 14 so that the distance between them is narrowed, and the emission density of the light beam is made uniform (H).

Claims

The scope of the claims

[1] One or more light sources (13) force A light incident part (14) for making the emitted light incident, and the light incident from the light incident part (14) on a uniform planar inner surface A transparent light guide part (16) for propagating the light with total reflection and a light emitting surface part (12) for emitting light that has passed through the light guide part (16) to the outside are formed. In a surface light source device having a flat light guide plate (11),

The light incident part (14) is provided in the vicinity of an edge of a region which is at least one of the front and back surfaces of the light guide plate (11) and does not overlap the light emission surface part (12),

Light incident part prism group (15, 15 ') force to advance the light incident from the light source (13) in the direction of total reflection at the light guiding part (16) Light incident on the light incident part (14) A surface light source device characterized in that the light guide plate (11) itself is formed and arranged on at least one of a surface and a surface on the back side.

[2] The surface light source device according to claim 1, wherein the light incident portion prism group (15) is formed so as to protrude from the surface of the light guide plate (11) in the surrounding area! .

[3] The surface light source device according to claim 1, wherein the light incident portion prism group (15) is formed to be recessed with respect to the surface of the light guide plate (11) in the surrounding area! .

[4] In the surface light source device according to claim 1, the light incident portion prism group (15) is disposed only on the surface on the side where the light emitted from the light source (13) is incident on the light guide plate (11). Surface light source device.

[5] In the surface light source device according to claim 1, the light incident portion prism group (15 ′) is provided only on a surface that is behind the surface on which the light emitted from the light source (13) is incident on the light guide plate (11). ) Is a surface light source device.

[6] The surface light source device according to claim 1, wherein the light incident portion prism is formed on both the surface on the side where the light emitted from the light source (13) is incident on the light guide plate (11) and the surface on the back side. Group (1

5, 15 ') is a surface light source device.

[7] In the surface light source device according to claim 1, the light incident portion prism group (15, 15 ′) includes one or a plurality of prisms having a horizontally long shape that crosses the light guide plate (11). Surface light source device.

[8] In the surface light source device according to claim 1, each prism force constituting the light incident portion prism group (15, 15 ^), the light source (13) force, centered on the position where the optical axis of the emitted light beam passes. A surface light source device formed in a circular arc shape and arranged concentrically.

[9] The surface light source device according to claim 1, wherein the light incident portion prism group (15, 15 ′) is configured by a large number of independent microprisms arranged with a space between each other. Light source device.

[10] In the surface light source device of claim 9, a large number of the microprism forces are arranged far from the light source (13), close to the light source (13) at the position, and narrower than the position. Surface light source device.

[11] In the surface light source device of claim 1, in the vicinity of the light incident part (14), the light reflecting sheet (19) faces the surface on which the light emitted from the light source (13) is incident. Is a surface light source device.

[12] In the surface light source device according to claim 1, a light reflecting sheet is provided in the vicinity of the light incident portion (14) so as to face a surface on the back side of the surface on which the light emitted from the light source (13) is incident. The surface light source device in which (18) is arranged.