JP2003242821A - Surface light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device easy to manufacture and possible to materialize a thinner thickness. <P>SOLUTION: This surface light source device 30 is composed of a light source 40, a sheet laminated body 21 to convert light from the light source 40 to a surface light source by transmitting it, film members 31, 32 to hold the light source 40 and the sheet laminated body 21 from both faces by a sandwiching structure, and the like. The sheet laminated body 21 is composed of a light guiding sheet member 22 to guide the light from the light source 40 to its surface side from its end face, a diffusing sheet 23, two prism sheets 24, 25, a light reflecting sheet 26 and the like. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source device that can be used as a backlight for liquid crystal panels, indicator lamps and the like.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view showing an example of a conventional planar light source device. The planar light source device 1 includes a light source 10 that emits light, a light guide member 2 that guides light from the light source 10 from an end surface to a front surface side, a diffusion sheet 3 disposed on the surface of the light guide member 2, and a diffusion sheet. It is composed of two prism sheets 4 and 5 arranged on the sheet 3, a light reflection sheet 6 arranged on the back side of the light guide member 2, and a metal frame 7 for housing these components. It

The light source 10 is composed of an LED (light emitting diode) unit 11 and a circuit board 14 on which the LED unit 11 is mounted. A lead wire 15 is electrically connected to the circuit board 14. The LED unit 11 has a package having a concave portion that is opened to the side, and the LED chip 12 is fixed to the concave portion by a die bond member or the like, and after fixing the chip, it is sealed with a translucent resin. The LED chip 12 has a flat rectangular parallelepiped shape and is of a surface emitting type that emits light from the upper surface of the chip, and is electrically connected to the lead electrode 13 by wire bonding or the like.

The light guide member 2 is made of a transparent resin or the like,
It has a tapered cross-sectional shape in which the thickness decreases from the light incident end face side toward the light source opposite side. The LED unit 11 is arranged in close contact with the light incident end surface of the light guide member 2, and the thickness of the light incident end surface is set so as to substantially match the height of the LED unit 11. When the light emitted from the light source 10 enters from the light incident end face, the light is repeatedly reflected and scattered while passing through the inside of the light guide member 2 and is emitted from the surface side of the light guide member 2.

The diffusion sheet 3 has a function of equalizing the intensity distribution of the light emitted from the surface side of the light guide member 2.

The prism sheets 4 and 5 are made of a transparent resin or the like having a large number of minute triangular prisms formed on their surfaces.
It has a function of refracting incident light from the back surface in the direction normal to the sheet surface and condensing the light. The prism sheets 4 and 5 are arranged so that the light refraction directions are orthogonal to each other.

The light reflection sheet 6 is made of a synthetic resin or the like having a reflective coating such as Ag or Al formed on its surface, and returns the leaked light from the light source 10 or the light guide member 2 to the light guide member 2 to generate light. It has the function of improving the usage efficiency.

The frame 7 is formed by bending a plate material such as Al or stainless steel into a box shape.
A certain thickness is required to ensure the rigidity of the entire device.

[0009]

When such a surface light source device is mounted on various portable devices such as mobile phones, digital cameras and video cameras, it is required to be small and lightweight and thin.

In the surface light source device 1 shown in FIG. 5, the frame 7 has a thickness of 200 μm, and the light reflection sheet 6 has a thickness of 85.
μm, the maximum thickness of the light guide member 2 is 0.8 mm to 1 mm, L
The height of the ED unit 11 is 1.0 mm, the thickness of the diffusion sheet 3 is 130 μm, and the thickness of each of the prism sheets 4 and 5 is 1.
When the thickness of the circuit board 14 is designed to be 40 μm and the thickness of the circuit board 14 is designed to be 250 μm, the total thickness TP of the device is about 1.5 mm to 2.
It will be about 1 mm.

However, there is an increasing demand for downsizing and weight reduction of portable equipment, and further reduction in thickness of the surface light source device.

An object of the present invention is to provide a planar light source device which is easy to manufacture and can be made thinner.

[0013]

To achieve the above object, a surface light source device according to the present invention comprises a light source, and a light guide sheet member for guiding light from the light source and radiating the light in a surface form. ,
And a film member for sandwiching the light source and the light guide member from both sides.

By sandwiching the light source and the light guide sheet member from both sides by using the film member, the light source and the light guide sheet member can be integrally held, and conventionally, the light source and the light guide sheet member have been used for ensuring the rigidity of the entire apparatus. The metal frame that was used can be omitted. Furthermore, by changing the light guide member from a tapered shape to a sheet shape, the overall thickness of the device can be significantly reduced compared to the conventional one.

When a thermoplastic resin having heat-sealing property or heat-adhesive property such as shrink wrap for packaging is used as the film member, the optical member is covered with the film member from both sides and then thermocompression-bonded. By this, it is possible to firmly seal. In addition, while the optical member is covered from both sides and suction-adhered, the peripheral edges of the film member may be bonded with an adhesive or the like.

By applying the film packaging technique in place of the metal frame in this manner, the manufacturing can be facilitated, the cost can be reduced, and the device can be made thin.

Further, in the present invention, the light source has a rectangular substrate having a plurality of cutouts formed along the longitudinal direction and a light emitting element provided at the bottom of the cutouts, and the light source is a light guide. It is preferable that the light sheet member is arranged close to the end surface.

Regarding the structure of the light source, a plurality of cutouts are formed along the longitudinal direction of the rectangular substrate, and light emitting elements such as LED chips are arranged at the bottom of the cutouts. By directly mounting the light emitting element on the substrate in this manner, the housing member of the LED unit can be omitted as in the conventional case, and thus the overall thickness of the device can be significantly reduced. Further, since the chips are directly mounted, the arrangement pitch of the light emitting elements can be shortened, so that the integration degree of the light emitting elements is improved and unevenness of the illumination intensity can be suppressed.

In this case, the light emitting element is preferably a lateral light emitting type LED chip which emits light substantially parallel to the substrate,
The entire light source can be made thinner than the surface-emitting type LED chip shown in FIG.

By arranging the light source thus obtained in the vicinity of the end face of the light guide sheet member, the amount of light entering the light guide sheet member from the light emitting element increases, and the light utilization efficiency can be improved.

Further, in the present invention, it is preferable that a light diffusing portion for diffusing light from the light guide sheet member is provided at least on the light emitting surface side.

Most of the light emitted from the light source is repeatedly reflected and scattered while passing through the light guide sheet member, and is emitted from the front surface side of the light guide sheet member. At this time, by providing the light diffusing portion on the light emitting surface side, the intensity distribution of the light emitted on the light emitting surface side can be equalized. Such a light diffusing portion may be provided as a separate dedicated member like a conventional diffusing sheet, but by forming it integrally with any member from the light guide sheet member to the film member, a dedicated diffusing member can be provided. The use of can be omitted, and the device can be made thinner.

Further, in the present invention, it is preferable that a prism portion for refracting light from the light guide sheet member is provided at least on the light emitting surface side.

Most of the light emitted from the light source is repeatedly reflected and scattered while passing through the light guide sheet member, and is emitted from the front surface side of the light guide sheet member. At this time, by providing the prism portion on the light emitting surface side, incident light from the back surface can be refracted in the surface normal direction and condensed. Such a prism portion may be provided as a separate dedicated member like a conventional prism sheet, but by integrally forming it as any member from the light guide sheet member to the film member, The use can be omitted, and the device can be made thinner.

Further, in the present invention, it is preferable that a light reflecting portion for reflecting the light from the light guide sheet member is provided on the side opposite to the light emitting surface.

Most of the light emitted from the light source is repeatedly reflected and scattered while passing through the light guide sheet member, and is emitted from the front surface side of the light guide sheet member. At this time, by providing the light reflecting portion on the side opposite to the light emitting surface, it is possible to return the leaked light from the light source or the light guide sheet member to the light guide sheet member and improve the light utilization efficiency. Such a light-reflecting portion may be provided as a separate dedicated member like a conventional light-reflecting sheet, but by integrally forming it also as any member from the light guide sheet member to the back-side film member. ,
The use of a member for exclusive use of light reflection can be omitted, and the thickness can be further reduced.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 (a) and 1 (b) are exploded perspective views showing an embodiment of the planar light source device according to the present invention.
FIG. 2 is a sectional view thereof. The planar light source device 30 sandwiches the light source 40 that generates light, the sheet laminated body 21 that transmits the light from the light source 40 and converts it into a surface light source, and the light source 40 and the sheet laminated body 21 in a sandwich structure from both sides. The film members 31 and 32 for

The sheet laminated body 21 includes a light guide sheet member 22 which guides light from the light source 40 from the end face to the front surface side, a diffusion sheet 23 arranged on the surface of the light guide sheet member 22, and a diffusion sheet 23. Two prism sheets 2 arranged in
4, 25 and a light reflection sheet 26 arranged on the back side of the light guide sheet member 22, and the like. The light reflection sheet 26, the light guide sheet member 22, the diffusion sheet 23, and the prism sheets 24 and 25 are arranged in this order from the bottom. Are stacked in.

The light source 40 is an elongated bar-shaped light source that emits light on the end face side, and is placed on the light reflection sheet 26 so as to be close to the end face of the sheet laminate 21, particularly the light incident end face of the light guide sheet member 22. Will be placed. The light reflection sheet 27 is also provided on the upper surface of the light source 40.

The light guide sheet member 22 is made of a flexible transparent resin or the like and has a substantially constant thickness. Light source 4
When the light emitted from 0 is incident from the light incident end surface of the light guide sheet member 22, the light is repeatedly reflected and scattered while passing through the inside of the light guide sheet member 22, and is emitted from the front surface side of the light guide sheet member 22. .

The diffusion sheet 23 is formed of a flexible transparent resin or the like containing diffusion beads and has a function of equalizing the intensity distribution of the light emitted from the surface side of the light guide sheet member 22. .

The prism sheets 24 and 25 are made of a flexible transparent resin or the like having a large number of minute triangular prisms formed on the surfaces thereof, and refract incident light from the back surface in the direction normal to the sheet surface. Has the function of collecting light. The prism sheets 24 and 25 are arranged so that the light refraction directions are orthogonal to each other.

The light reflecting sheet 26 is made of a flexible synthetic resin or the like on the surface of which a reflective coat of Ag, Al, etc. is formed, and emits light leaked from the light source 40 and the light guide sheet member 22. It has a function of returning to the surface side and improving the light utilization efficiency. The light reflection sheet 27 also has a function of reflecting the light emitted from the light source 40 and increasing the light utilization efficiency.

The film members 31 and 32 have a size larger than the planar shape of the light reflection sheet 26 so that the joint portion can be secured in a state where the sheet laminated body 21 and the light source 40 are covered from both sides.

As the film members 31 and 32, a flexible synthetic resin or the like can be used, and the film member 3 on the front surface side can be used.
2 is preferably a transparent resin, but the film member 31 on the back surface side may be a colored resin such as black or an opaque resin.

When the film members 31 and 32 are made of, for example, a thermoplastic resin having thermal adhesiveness or thermal adhesiveness,
After covering the sheet laminate 21 and the light source 40 from both sides,
By thermocompression bonding, strong sealing can be achieved.

When a thermosetting resin is used for the film members 31 and 32, the sheet laminate 21 and the light source 40 are covered from both sides and suction-adhered, and the peripheral edges of the film members are bonded with an adhesive or the like. It can be adhered and firmly sealed.

By thus forming the sheet laminate 21 and the film members 31 and 32 with a flexible material,
Since it exhibits flexibility as a whole, it is possible to relieve stress at the time of dropping or impact and maintain high reliability.

FIG. 3A and FIG. 3B show a light source 40.
It is a perspective view showing an example. The light source 40 is composed of an elongated rectangular mount substrate 41, a spacer substrate 42 in which a plurality of notches 42a are formed along the longitudinal direction, and the like.
The spacer substrate 42 is integrated on the mount substrate 41 by fixing it with an adhesive or the like.

The mount substrate 41 is formed of an electrically insulating material such as a glass epoxy substrate, a conductor pattern 41a is provided on the upper surface, a plurality of LED chips 43 are directly mounted at a predetermined pitch, and the LED chips are formed by wire bonding or the like. 43 and the conductor pattern 41a are electrically connected. Lead wires 45 are electrically connected to both ends of the conductor pattern 41 a, and each LED chip 43 is connected in series between the two lead wires 45.

The spacer substrate 42 is formed of a material having good workability, and protects the LED chip 43 and the conductor pattern 41a during film packaging while securing a mounting space for the LED chip 43 by the notch 42a. Optically, a material that guides the light from the LED chip 43 toward the sheet laminated body 21 is desirable.

The LED chip 43 is preferably a lateral light emitting type which emits light substantially parallel to the mount substrate 41, and the entire light source can be made thinner than the surface emitting type. When used as a white backlight of a liquid crystal panel or the like, it is desirable to mix blue LED chips, green LED chips, red LED chips, or use white LED chips that emit white light in one chip.

Next, the operation will be described. Referring to FIG. 2, 2
When power is supplied from the outside between the lead wires 45 of the book, each LED chip 43 emits light and emits light toward the sheet laminated body 21. The light incident from the end surface of the light guide sheet member 22 is repeatedly reflected and scattered while passing through the inside of the light guide sheet member 22, and is emitted from the front surface side of the light guide sheet member 22. The light that does not directly enter the light guide sheet member 22 is also reflected by the light reflection sheets 26 and 27 and returned to the light guide sheet member 22. The light directly incident on the diffusion sheet 23 and the prism sheets 24 and 25 is also used as illumination light after being repeatedly reflected and scattered.

Light radiated from the front surface side of the light guide sheet member 22 is diffused by the diffusion sheet 23, condensed by the prism sheets 24 and 25 in the surface normal direction, passes through the film member 32, and passes through the surface. It is used as a light source.

In the surface light source device 30 shown in FIG.
The film members 31 and 32 have a thickness of 100 μm, the light reflection sheets 26 and 27 have a thickness of 40 μm, and the light guide sheet member 22
The thickness of the diffusion sheet 23 is 270 μm, and the thickness of the diffusion sheet 23 is 65 μm.
m, the prism sheets 24 and 25 are designed to have a thickness of 62 μm and the light source 40 is designed to have a height of 250 μm, the total thickness TA of the device is about 0.7 mm, which is significantly thinner than the conventional one. Can be converted.

FIG. 4 is a sectional view showing another embodiment of the planar light source device according to the present invention. This planar light source device 30a
2 is almost the same as the configuration and operation in FIG. 2, except that the light reflecting sheet 26 is omitted and the film member 31 on the back side also has a light reflecting function.

The planar light source device 30a includes a light source 40 for generating light, a sheet laminated body 21 for transmitting the light from the light source 40 and converting it into a surface light source, the light source 40 and the sheet laminated body 21.
It is composed of film members 31, 32, etc. for sandwiching from both sides by a sandwich structure.

The sheet laminated body 21 includes a light guide sheet member 22 that guides light from the light source 40 from the end face to the front surface side, a diffusion sheet 23 disposed on the surface of the light guide sheet member 22, and a diffusion sheet 23. Two prism sheets 2 arranged in
4, 25, etc., the light guide sheet member 22,
The diffusion sheet 23 and the prism sheets 24 and 25 are laminated in this order.

On the inner surface of the film member 31, Ag, Al
And the like, and has a function of returning the leaked light from the light source 40 and the light guide sheet member 22 to the light emitting surface side and increasing the light utilization efficiency.

In the surface light source device 30a shown in FIG. 4, the film member 32 has a thickness of 100 μm, and the film member 31 having a light reflection sheet function has a thickness of 40 μm.
m, the thickness of the light guide sheet member 22 is 270 μm, the thickness of the diffusion sheet 23 is 65 μm, the thickness of each of the prism sheets 24 and 25 is 62 μm, and the height of the light source 40 is 250 μm. The thickness TB is about 0.6 mm, which is significantly thinner than the conventional one.

In FIG. 4, the film member 31 on the back side is
Although the example in which the light reflection function is added to the above, the light diffusion function similar to that of the diffusion sheet 23 is added to the film member 32 on the front surface side, so that the diffusion sheet 23 can be omitted and further thinning is possible. Become. Further, by imparting the same prism function as the prism sheets 24, 25 to the film member 32 on the front surface side, the prism sheets 24, 2
One or both of 5 can be omitted, and the thickness can be further reduced.

As described above, by applying the film packaging technique instead of the metal frame, the manufacturing can be facilitated, the cost can be reduced, and the device can be thinned.

[0054]

As described above in detail, by sandwiching the light source and the light guide sheet member from both sides with the film member, the light source and the light guide sheet member can be integrally held, which is conventionally used. Since the metal frame can be omitted, and the light guide member is formed into a sheet shape, the entire device can be remarkably thinned.

[Brief description of drawings]

FIG. 1A and FIG. 1B are exploded perspective views showing an embodiment of a planar light source device according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a planar light source device according to the present invention.

3 (a) and 3 (b) are perspective views showing an example of a light source 40. FIG.

FIG. 4 is a cross-sectional view showing another embodiment of the planar light source device according to the present invention.

FIG. 5 is a cross-sectional view showing an example of a conventional planar light source device.

[Explanation of symbols]

21 sheet stack 22 Light guide sheet member 23 Diffusion sheet 24,25 prism sheet 26,27 Light reflection sheet 30, 30a planar light source device 31, 32 Film material 40 light source 41 Mount board 41a Conductor pattern 42 Spacer substrate 42a Notch 43 LED chip 45 lead wire

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 6/00 331 G02B 6/00 331 G02F 1/13357 G02F 1/13357 // F21Y 101: 02 F21Y 101: 02 F-term (reference) 2H038 AA55 BA06 2H091 FA14Z FA21Z FA23Z FA32Z FA45Z FD22 LA11

Claims (5)

[Claims] 1. A light source, a light guide sheet member for guiding light from the light source and radiating the light in a plane, and a film member for sandwiching the light source and the light guide member from both sides. Planar light source device. 2. The light source has a rectangular substrate having a plurality of cutouts formed along the longitudinal direction and a light emitting element provided at the bottom of the cutouts, and the light source is a light guide sheet member. The planar light source device according to claim 1, wherein the planar light source device is disposed near an end face of the. 3. The planar light source device according to claim 1, further comprising a light diffusing section that diffuses light from the light guide sheet member at least on the light emitting surface side. 4. The planar light source device according to claim 1, further comprising a prism portion that refracts light from the light guide sheet member at least on the light emitting surface side. 5. The planar light source device according to claim 1, further comprising a light reflecting portion that reflects light from the light guide sheet member on the side opposite to the light emitting surface.