JPH10255531A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a surface light source device lighter in weight and thinner and to enhance the efficiency of optical coupling. SOLUTION: Two transparent films 22 made of a resin are bonded together via light guiding resin layers 24, 25, and a light emitting part 27 is sandwiched between the ends of the transparent films 22 and sealed and fixed by a transparent resin 32. After light emitted from the light emitting part 27 is confined within the light guiding resin layers 24, 25, it is scattered between the light guiding resin layers 24, 25 and emitted to the outside from the transparent films 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a surface light source device. In particular, it relates to a thin integrated surface light source device used for a liquid crystal display device or the like.

[0002]

2. Description of the Related Art A conventional surface light source device is shown in an exploded perspective view of FIG. 1 and a sectional view of FIG. The surface light source device 1 includes a light guide plate 2 for confining light, a light emitting unit 3, a reflection sheet 11, and a reflection plate 4. The light guide plate 2 is formed of a transparent resin having a large refractive index such as a polycarbonate resin or a methacryl resin, and a diffusion pattern 5 is formed on the lower surface of the light guide plate 2 by uneven processing or dot printing of a diffuse reflection ink. . The light emitting unit 3 is a device in which a so-called point light source 7 such as a plurality of light emitting diodes is mounted on a circuit board 6, and faces the side surface (light incident surface 8) of the light guide plate 2.

At both ends of the light guide plate 2 on the light incident surface 8 side, a substrate holding portion 12 for holding the light emitting portion 3 is formed, and both ends of the circuit board 6 are placed in the substrate holding portion 12. By inserting, the light emitting unit 3 can be attached to face the light incident surface 8 of the light guide plate 2.

The reflection sheet 11 is a metal tape or the like, and is attached between the upper surface of the light guide plate 2 on the light incident surface 8 side and the upper surface of the light emitting section 3. The reflection plate 4 is formed of, for example, a white resin sheet having a high reflectance, and both sides are adhered to the lower surface of the light guide plate 2 by the double-sided tape 9.

[0005] As shown in FIG. 2, the light f emitted from the light emitting unit 3 and guided from the light incident surface 8 into the light guide plate 2 is totally reflected inside the light guide plate 2 to be guided. It is confined inside the light plate 2. When the light f inside the light guide plate 2 is incident on the diffusion pattern 5, the light f is diffusely reflected, and the light f reflected at an angle smaller than the critical angle of total reflection toward the light emission surface 10 is extracted to the outside from the light emission surface 10. . The light f emitted obliquely upward from the light emitting unit 3 is reflected by the reflection sheet 11.
And is guided to the light incident surface 8 of the light guide plate 2.
Further, the light f transmitted through a portion of the lower surface of the light guide plate 2 where the diffusion pattern 5 does not exist is reflected by the reflection plate 4 and returns to the inside of the light guide plate 2 again. Therefore, the reflection sheet 11 and the reflection plate 4 prevent a loss of light amount from the light emitting unit 3 and the light guide plate 2.

The above-mentioned surface light source device is used as a backlight of a liquid crystal display device and the like, and is particularly used for a liquid crystal display portion of a highly portable product such as a mobile phone due to its small size and light weight. For this reason, there is a strong demand for a thinner surface light source device, and a surface light source device thinner than the current 0.8 mm thick surface light source device is required.

On the other hand, the size (area) of the surface light source device has been about 2 inches in the surface light source device used in the liquid crystal display section of the portable telephone until now. 2. Description of the Related Art As portable information terminals such as personal computers (PCs) are commercialized, a surface light source device having a light emitting area of 3 to 7 inches is desired with an increase in the size of a display unit.

[0008] However, the thickness of the light guide plate of the resin molded product is set to 0.
When the size was set to 8 mm and the size was set to 3 inches or more, the resin did not spread to every corner during molding of the light guide plate, resulting in a defective product. Further, even if such a light guide plate can be formed, there have been problems that the light guide plate is warped, the molding time and the curing time after the molding are lengthened, and the cost is increased.

In recent years, in a liquid crystal display device using a glass substrate, a plastic film liquid crystal display panel using a plastic film instead of the glass substrate has been put to practical use. Such a plastic film liquid crystal display panel has features such as lightness, no breakage, thinness, display of a curved surface, and formation of a different shape. However, in order to take advantage of the characteristics of such a plastic film liquid crystal display panel, the light guide plate also has features such as lightness, non-breakability, thinness, display of a curved surface, and possible formation of a different shape. You need to use lights.

[0010]

Considering the above-mentioned problems with respect to the light guide plate of the resin molded product, it is conceivable to use a resin film as the light guide plate. If the film is used as a light guide plate, the thickness of the light guide plate can be reduced, and for example, a light guide plate having a thickness of 0.4 mm can be used. Further, according to the surface light source device using the resin film as the light guide plate, it is possible to obtain a backlight that can make use of the features of the plastic film liquid crystal display panel.

However, as shown in FIG. 3, the point light source 7 provided in the light emitting section 3 is formed by sealing a light emitting diode 13 mounted on a circuit board 6 with a transparent resin 14, so that a film is used. Even if the thickness of the light guide plate 15 can be reduced to about 0.4 mm by using, the size of the light emitting unit 3 becomes larger than the thickness of the light guide plate 15. For example, the distance from the upper end of the circuit board 6 to the light emitting diode 13 is required to be 0.6 mm, and the size of the light emitting diode 13 is also 0.3 mm.
mm. For this reason, the size of the point light source 7 is
5 is larger than the light incident surface 8, and especially the light emitting diode 1.
The position of 3 is greatly shifted obliquely below the light incident surface 8. As a result, as shown in FIG.
Out of the light f emitted from the light receiving surface 8
Further, the light f that has entered the light guide plate 15 from the lower surface of the light guide plate 15 is reflected by the reflective seal 11 on the upper surface and immediately exits from the lower surface of the light guide plate 15, and the point light source 7 and the light guide plate The optical coupling efficiency with No. 15 was too bad.

When the light guide plate 15 made of a thin film is used, the light emitting unit 3 and the light guide plate 15 are connected only by the reflective seal 11 bonded between the upper surface of the light guide plate 15 and the upper surface of the light emitting unit 3. Therefore, the assembly of the light emitting unit 3 and the light guide plate 15 becomes unstable, and the surface light source device is immediately disassembled.

Therefore, as shown in FIG. 4, a holder 16 made of white resin is extended from above and below the circuit board 6 so as to cover the point light source 7, and a light guide plate 15 made of a film is provided in a gap between the holders 16. Insert the end into the holder 16
A point light source 7 is placed on the end face of the light guide plate 15 so as to be sandwiched between the light sources.
The surface light source device 17 to which is attached was prototyped. According to such a structure, the point light source 7 can be opposed to the light incident surface 8 of the light guide plate 15, but since the thickness of the light guide plate 15 is thin, only a small amount of light is used in such a structure.
5 and the optical coupling efficiency was low. In addition, it is necessary to allow for a manufacturing error of at least about 0.1 mm in the mounting position and dimensions of the point light source 7 and the holder 16 on the circuit board 6. There has been a problem that the coupling efficiency is immediately reduced due to the deviation.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object of the present invention is to provide a surface light source device having high optical coupling efficiency. Another object of the present invention is to provide a light and very thin surface light source device.

[0015]

SUMMARY OF THE INVENTION The surface light source device according to the first aspect comprises two transparent substrates, a transparent resin layer for bonding the two transparent substrates together, and a light emitting portion sandwiched between the transparent substrates. It is characterized by becoming.

In this surface light source device, a light-emitting portion is sandwiched between two transparent substrates, and light emitted from the light-emitting portion is introduced into the two transparent substrates and the transparent resin layer, and the light is emitted therefrom. Can be confined. Since the light emitting portion for emitting light is sandwiched between the transparent substrates, the light emitted from the light emitting portion is unlikely to leak to the outside, and the light between the light emitting portion and the light guide region formed of the transparent substrate and the transparent resin layer. The coupling efficiency can be very high.

In particular, if a reflection film is formed on the inner surface of the transparent substrate from the region where the light emitting portion is provided to the region adhered to the transparent resin layer, the light emitted from the light emitting portion passes through the transparent substrate and becomes external. Can be prevented from leaking into
Light use efficiency can be further improved.

In this surface light source device, the surface light source device can be made thin by forming one transparent substrate, preferably both transparent substrates, with a resin sheet.
It is possible to reduce the weight and thickness of the surface light source device. Moreover, in this surface light source device, since the light emitting portion is interposed between the transparent resin sheets, the light coupling efficiency between the resin sheet and the transparent resin layer and the light emitting portion may be deteriorated even if a thin resin sheet is used. Absent.

Further, if the light emitting section is fixed to the transparent substrate with a transparent resin, the light emitting section can be sealed with a resin for fixing the light emitting section. Such a bare chip can be used, and the thickness of the surface light source device can be reduced by downsizing the light emitting portion.

Further, if an air layer is formed between the resin fixing the light emitting portion and the transparent resin layer, when light from the light emitting portion enters the transparent resin layer through the air layer, the transparent substrate Since the light is refracted in a direction parallel to the light emitting portion, the light can be transmitted through the transparent substrate immediately and does not leak to the outside, and can guide the light far from the light emitting portion.

If the thickness of the transparent resin layer is gradually reduced as the distance from the light emitting portion increases, the light in the transparent resin layer is transmitted while being totally reflected by the transparent substrate or the surface of the transparent resin layer. Since the angle of incidence on the surface of the transparent substrate or the transparent resin layer gradually decreases, the light is gradually emitted from the surface light source device to the outside.

Further, if the transparent resin layer is composed of at least two resin layers having different refractive indexes and an uneven pattern for diffusing light is formed at the interface between these resin layers, the transparent resin layer has Is diffused at the interface between the resin layers and gradually emitted to the outside.

Alternatively, even if a concavo-convex pattern for diffusing light is formed on at least one of the inner surface and the outer surface of the transparent substrate, light transmitted through the transparent resin layer diffuses at the interface between the two resin layers and slightly spreads. The light is gradually emitted to the outside.

In addition, since the amount of light guided as the distance from the light emitting portion decreases, the degree of light diffusion increases as the concave / convex pattern moves away from the light source. The luminance distribution in the region can be made uniform.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 5 is a perspective view showing a surface light source device 21 according to an embodiment of the present invention, and FIG. 6 is an enlarged sectional view thereof. The surface light source device 21 includes a pair of front and back transparent films 22 made of PET (polyethylene terephthalate) or the like.
(With a thickness of about 0.1 mm). In the light emitting area 23 of the surface light source device 21,
Between the two, two light guide resin layers 24, 25 are filled, and the transparent film 22 is formed between the two light guide resin layers 24, 25.
Are adhered so as to be substantially parallel. For example, the refractive index of the transparent film 22 is 1.46, the refractive index of the light guide resin layer 24 on the light emission side is 1.55, and the refractive index of the light guide resin layer 25 on the back side is 1.40. In addition, this 2
At the interface between the light guide resin layers 24 and 25 of the layers, a regular or random fine uneven pattern 26 is provided.

At the end between the transparent films 22, the light emitting section 2
7 is sandwiched. The light emitting section 27 is formed by die bonding a light emitting diode chip 30 on a wiring 29 of a circuit board 28, and further connecting a bonding wire 31 to the wiring 29. The light emitting section 27 is fixed between the transparent films 22 by a transparent resin 32, and at the same time, the light emitting diode chip 30 is sealed and protected by the transparent resin 32. An air layer 33 is formed between the transparent resin 32 that fixes the light emitting section 27 and the light guide resin layers 24 and 25 in the light emitting area 23. The air layer 33 and the light guide resin layer 24, The boundary with 25 is an optical coupling end face 34. It is desirable that the optical coupling end face 34 be formed as flat as possible.

According to such a surface light source device 21, if the thickness of the transparent film 22 is about 0.1 mm and the total thickness of the two light guide resin layers 24 and 25 is about 0.2 mm, the surface light source The thickness of the light emitting area 23 of the device 21 can be about 0.4 mm. However, the light emitting section 27 is not
Since the thickness of the transparent film 22 is larger than that of the light emitting portion 2, the end portion of the transparent film 22 is curved so as to spread outward.
7 is sandwiched.

On the inner surface of the transparent film 22, a reflection film 35 for regular reflection of the light f is formed from the portion where the light emitting portion 27 is inserted to the end of the transparent resin 32. The reflection film 35 may be a metal deposition film or a vacuum plating film formed on the inner surface of the transparent film 22, or may be a metallic tape attached to the inner surface of the transparent film 22.
Further, a light reflection sheet 36 for regularly reflecting light is provided also on the outer surface side of the lower transparent film 22.
The light reflection sheet 36 may be disposed facing the outer surface of the transparent film 22, or may be a metal deposition film or a vacuum plating film formed on the outer surface of the transparent film 22.

In the surface light source device 21 as described above,
The transparent film 22 and the light guide resin layers 24 and 25 function as a conventional light guide plate, and the light f emitted from the light emitting diode chip 30 of the light emitting unit 27 is, as shown in FIG. Direct light coupling end face 34 through air layer 33
Then, the light enters the light guide resin layers 24 and 25, or is reflected once or several times by the reflection film 35, and then enters the light guide resin layers 24 and 25 from the optical coupling end face 34. Optical coupling end face 34
Is almost perpendicular to the optical axis of the light emitting section 27, so that the light guide angle θ of most of the light incident on the light guide resin layers 24 and 25 from the air layer 33 is If the refractive index of 25 is about 1.40, then | θ | <45 °. Therefore, the incident angle α of light on the interface between the transparent film 22 and the air layer 33 perpendicular to the optical coupling end face 34 is 45 °.
As described above, the light is totally reflected on the outer surface of the transparent film 22. Therefore, even if the light reaches the light emitting region 23 without the reflection film 35, most of the light is confined in the transparent film 22 and the light guide resin layers 24 and 25 and is guided.

However, the light guide resin layer 24 and the light guide resin layer 25
Are formed of materials having different refractive indices, and the uneven pattern 26 is formed at the boundary, when the light f passes through the boundary, the direction of the light is bent at random, and the incident angle to the transparent film 22 is changed. When α becomes smaller than the critical angle of total reflection at the interface between the transparent film 22 and the air, the light is emitted to the outside. However, since the light reflection sheet 36 is present on the surface opposite to the light emission side, the light emitted there is specularly reflected by the light reflection sheet 36 and returned to the light guide resin layers 24 and 25 again.

The unevenness pattern 26 at the interface between the light guide resin layer 24 and the light guide resin layer 25 is such that the density or the degree of light diffusion increases as the distance from the light emitting portion 27 increases, so that Can be made uniform.

According to the surface light source device 21 as described above, the thickness of the light emitting area 23 of the surface light source device 21 is set to, for example, about 0.4.
mm, and a very thin surface light source device 21 can be realized. Moreover, since the light emitting unit 27 is sandwiched between the transparent films 22, there is no displacement between the light emitting unit 27, the transparent film 22, and the light guide resin layers 24 and 25 in principle. Further, even if the light emitting diode is displaced in the thickness direction of the transparent film 22 on the circuit board 28, all light is guided to the light coupling end face 34 by the reflection film 35, so that the coupling efficiency and the luminance distribution in the light emitting area 23 are reduced. Does not affect uniformity.

FIGS. 8A to 8F show the surface light source device 21.
FIG. 3 is a cross-sectional view for describing a method of manufacturing a semiconductor device by a so-called 2P (Photo-Polymerization) method. FIG. 8 (a)
Reference numeral 37 denotes a stamper on which an uneven pattern 26 at the interface between the light guide resin layers 24 and 25 is formed. First, an ultraviolet curable resin for forming the light guide resin layer 24 on the stamper 37 is shown. Potting 38. Next, the transparent film 22 having the reflection film 35 formed in advance at the end of the inner surface is superimposed on the ultraviolet curing resin 38 and the pressing glass 39
The transparent film 22 is pressed, and the ultraviolet curable resin 38 is spread between the transparent film 22 and the stamper 37. Thereafter, as shown in FIG. 8B, the ultraviolet curable resin 38 is irradiated with ultraviolet light through the holding glass 39 and the transparent film 22 to cure the ultraviolet curable resin 38, and the light guide resin layer 24 is formed.
Is molded. When the light guide resin layer 24 is formed, the stamper 37 is separated from the light guide resin layer 24.

On the other hand, as shown in FIG. 8C, a transparent film
Is placed on a glass table 40 with the inner surface facing up, and an ultraviolet curable resin 41 for forming the light guide resin layer 25 is potted on the transparent film 22. Next, FIG.
As shown in (d), the transparent film 22 having the light guide resin layer 24 formed on the inner surface thereof is overlaid on the ultraviolet curable resin 41, and the transparent film 22 and the ultraviolet curable resin are interposed between the holding glass 39 and the glass base 40. The ultraviolet curable resin 41 is pushed and spread while sandwiching the resin 41. After that, the ultraviolet curable resin 41 is irradiated with ultraviolet rays through the glass table 40 and the transparent film 22 to cure the ultraviolet curable resin 41 and form the light guide resin layer 25.

Thereafter, as shown in FIG. 8E, the end of one transparent film 22 is turned up to hold the light emitting section 27 on the other transparent film 22, and the light emitting diode chip 30 of the light emitting section 27 is turned on. The light emitting diode chip 30 is sealed by potting a transparent resin 32 on the surface on the side where is mounted, and furthermore, as shown in FIG. The light emitting section 27 and the transparent film 22 are bonded and integrated by bonding to the resin 32 and curing the transparent resin 32.

As described above, by manufacturing the surface light source device 21 by the 2P method using the ultraviolet curing resins 38 and 41, the curing time after molding is shortened and the surface light source device 2 is efficiently manufactured.
1 can be manufactured.

In FIG. 5, the light emitting diode chip 3
Although 0 is only provided at the center of the end of the surface light source device 21, a linear light source type light emitting unit in which a plurality of light emitting diode chips 30 are arranged on the circuit board 28 at substantially constant intervals may be used. .

(Second Embodiment) FIG. 9 is a schematic sectional view showing a method of manufacturing a surface light source device 21 according to another embodiment of the present invention. This is the surface light source device 21 of the first embodiment.
Is described. That is, in the above manufacturing method, the transparent films 22 are separated from each other by the light guide resin layers 24 and 2.
After bonding with 5, the light-emitting portion 27 is bonded and fixed between the transparent films 22 with the transparent resin 32. In this embodiment, an ultraviolet curing resin 41 for forming the light guide resin layer 25 is applied to the transparent film 22. At this time, the light emitting section 27 is fixed to the transparent film 22 with the ultraviolet curing resin 41 at the same time. According to such a method, the manufacturing procedure can be simplified.

(Third Embodiment) FIG. 10 is a schematic sectional view showing a surface light source device 42 according to another embodiment of the present invention. In this surface light source device 42, both transparent films 2
The spacing between the two varies over the entire length. That is,
The light guide resin layer 43 is formed so as to have a substantially wedge shape. Further, the light guide resin layer 43 is formed by only one layer.

In such a surface light source device 42, light incident on the light coupling end face 34 at a large light guide angle is transmitted to the transparent film 2 at a position relatively close to the light emitting portion 27 in the light emitting area 23.
2 is emitted to the outside. On the other hand, since the two transparent films 22 are inclined, the light incident at a small light guide angle has a smaller incident angle α to the transparent film 22 every time the light is totally reflected by the outer surface of the transparent film 22, and the transparent film 22 2
2 is smaller than the critical angle of total reflection at the interface between the transparent film 22 and the air, the light is emitted to the outside. As a result, the light is emitted to the outside from a location relatively far from the light emitting unit 27.

Therefore, in this embodiment, the transparent films 22 are inclined so that the distance between the transparent films 22 on the side opposite to the light emitting portion 27 is narrowed, so that the light emitting area 23 The light f can be emitted with substantially uniform brightness from the whole. In such a structure, a glass substrate can be used instead of the transparent film 22.

(Fourth and fifth embodiments) FIG. 11 is a schematic sectional view showing a surface light source device 44 according to one embodiment of the present invention. In the surface light source device 44, an uneven pattern 45 for light diffusion is formed on the outer surface or inner surface of the transparent film 22 on the light emission side, and the density or the degree of light diffusion of the uneven pattern 45 increases as the distance from the light emitting unit 27 increases. The concavo-convex pattern 45 is changed so as to be larger.

The light guided from the light emitting section 27 to the light guide resin layers 24 and 25 is gradually diffused by the concave / convex pattern 45 in the process of being guided from the light emitting section 27 side to the other end, so that the surface light source device is gradually increased. Since the light is emitted from 44 to the outside, the light amount gradually decreases as the distance from the light emitting unit 27 increases. Therefore, by changing the concavo-convex pattern 45 so that the density or the degree of light diffusion increases as the distance from the light-emitting portion 27 increases, the luminance distribution over the entire light-emitting region 23 can be made uniform.

Further, as shown in the surface light source device 46 shown in FIG.
2) UV curable resin 48 on the outer or inner surface
The uneven pattern 49 may be formed by lamination. When two glass plates 47 are used as in this embodiment, they may be opposed to each other in parallel, and the light guide resin layer 43 and the light emitting unit 27 may be interposed therebetween.

(Sixth Embodiment) FIG. 13 is a sectional view showing a surface light source device 50 according to still another embodiment of the present invention. In this embodiment, one is a glass substrate 47 and the other is a transparent film 22. When a very thin glass plate is used, it is difficult to use the glass plate by bending it because of its strength. Therefore, the glass plate is used while being flat, and only the transparent film 22 is bent on the light emitting unit 27 side. Like that.

(Liquid Crystal Display) FIG. 14 is a sectional view showing a liquid crystal display 81 using a surface light source device 80 according to the present invention. Above the surface light source device 80, the liquid crystal display panel 8
3 are provided. The liquid crystal display panel 83 is a plastic film liquid crystal display panel in which a transparent substrate film 84 having a transparent electrode 82 formed on the lower surface and a transparent substrate film 84 having a transparent electrode 82 formed on the upper surface are sandwiched by spacer particles 85. And a liquid crystal material 86
Is sealed, and polarizing plates 87 are arranged above and below.

According to such a liquid crystal display device 81, both the liquid crystal display panel and the surface light source are lightweight, thin, and hard to break.

(Electronic Device Equipped with Liquid Crystal Display Device) The liquid crystal display device according to the present invention is a wireless information transmission device such as a mobile phone or a low-power radio, a portable personal computer, an information processing device such as an electronic organizer or a calculator. It is preferable to use it for devices and the like. FIG. 15 is a perspective view showing a mobile phone 89 provided with a liquid crystal display device 81 as shown in FIG. 14 for display according to the present invention, and FIG. 16 is a functional block diagram thereof. A button switch 90 such as a numeric keypad for dial input is provided on the front of the mobile phone 89, a liquid crystal display device 81 is provided above the switch 90, and an antenna 91 is provided on the upper surface. When a dial or the like is input from the button switch 90, the input dial information or the like is transmitted from the antenna 91 to the base station of the telephone company through the transmission circuit 92. On the other hand, the input dial information and the like are sent to the liquid crystal drive circuit 93, and the liquid crystal display device 81 is driven by the liquid crystal drive circuit 93, and the dial information and the like are displayed on the liquid crystal display device 81.

FIG. 17 is a diagram showing an example of FIG.
And a portable information terminal 9 such as an electronic organizer or a portable personal computer having a liquid crystal display device 81 as shown in FIG.
4 is a perspective view, and FIG. 18 is a functional block diagram thereof.
When the cover 95 is opened, the portable information terminal 94 includes a key input section 96 and a liquid crystal display device 81. Inside the portable information terminal 94, a liquid crystal driving circuit 93, an arithmetic processing circuit 97, and the like are provided.
Thus, for example, when a ten key, a kana key, or the like is input from the key input unit 96, the input information is sent to the liquid crystal drive circuit 93 and displayed on the liquid crystal display device 81. Next, when a control key such as a calculation key is pressed, predetermined processing and calculation are executed in the calculation processing circuit 97, and the result is sent to the liquid crystal drive circuit 93 and displayed on the liquid crystal display device 81.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a conventional surface light source device.

FIG. 2 is a cross-sectional view of the surface light source device.

FIG. 3 is an enlarged partially sectional view showing a surface light source device using a film as a light guide plate.

FIG. 4 is an enlarged partially sectional view showing another surface light source device using a film as a light guide plate.

FIG. 5 is a perspective view showing a surface light source device according to an embodiment of the present invention.

FIG. 6 is a partially broken sectional view showing the surface light source device of the above.

FIG. 7 is an operation explanatory view of the surface light source device of the above.

FIGS. 8A to 8F are cross-sectional views illustrating a method of manufacturing the surface light source device according to the first embodiment.

FIG. 9 is a schematic sectional view showing another method for manufacturing the surface light source device according to another embodiment of the present invention.

FIG. 10 is a schematic sectional view showing a surface light source device according to another embodiment of the present invention.

FIG. 11 is a schematic sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 12 is a schematic sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 13 is a schematic sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 14 is a cross-sectional view of a liquid crystal display device using the surface light source device of the present invention.

FIG. 15 is a perspective view showing a mobile phone provided with a liquid crystal display device according to the present invention for a display.

FIG. 16 is a block diagram showing a configuration for driving a liquid crystal display device in the above mobile phone.

FIG. 17 is a perspective view showing a portable information terminal such as an electronic organizer provided with a liquid crystal display device according to the present invention for a display.

FIG. 18 is a block diagram showing a configuration for driving a liquid crystal display device in the portable information terminal of the above.

[Explanation of symbols]

 Reference Signs List 22 transparent film 24, 25 light-guiding resin layer 26 uneven pattern 27 light-emitting unit 32 transparent resin 33 air layer 35 reflection film 47 glass substrate

Claims (9)

[Claims] 1. A surface light source device comprising: two transparent substrates; a transparent resin layer for bonding the two transparent substrates to each other; and a light emitting unit sandwiched between the transparent substrates. 2. A reflection film is formed on an inner surface of the transparent substrate from a region where a light emitting portion is provided to a region adhered to a transparent resin layer.
The surface light source device according to claim 1. 3. The surface light source device according to claim 1, wherein at least one of the two transparent substrates is a transparent resin sheet. 4. The surface light source device according to claim 1, wherein the light emitting unit is fixed between the transparent substrates by a transparent resin. 5. The surface light source device according to claim 4, wherein an air layer is formed between the resin fixing the light emitting unit and the transparent resin layer. 6. The surface light source device according to claim 1, wherein the thickness of the transparent resin layer gradually decreases as the distance from the light emitting unit increases. 7. The transparent resin layer is composed of at least two resin layers having different refractive indexes, and an uneven pattern for diffusing light is formed at an interface between these resin layers. The surface light source device according to claim 1. 8. The surface light source device according to claim 1, wherein an uneven pattern for diffusing light is formed on at least one of an inner surface and an outer surface of the transparent substrate. 9. The surface light source device according to claim 8, wherein the degree of light diffusion of the uneven pattern increases as the distance from the light emitting unit increases.