JP2004273185A - Planar lighting device and liquid crystal display device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar lighting device that can prevent deterioration of the luminance due to a gap generated between a light emitting element and a light guide plate by a simple installation method of a member. <P>SOLUTION: In the planar lighting device having the light emitting element 1 and the light guide plate 4, the light emitting surface of the light emitting element 1 and the light incident surface of the light guide plate 4 are adhered with a transparent fixing material. Thereby, since the gap between the light emitting element 1 and the light guide plate 4 becomes small, and the light emitted by the light emitting element 1 is transmitted to the light guide plate 4 without waste, the deterioration of the luminance can be prevented. The light emitting element 1 and the light guide plate 4 can be simply mounted. Further, when impact is inflicted from outside, breakage caused by collision generated by individual movement of the light emitting element 1 and the light guide plate 4 can be prevented since the light emitting element 1 and the light guide plate 4 are integrated by the fixing material. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a planar lighting device, and more particularly, to a planar lighting device used for a backlight of a liquid crystal display device or the like.
[0002]
[Prior art]
The structure of a conventional planar lighting device will be described with reference to the accompanying drawings.
The liquid crystal display device includes an image display unit on which an image is displayed, and a lighting device that irradiates the image display unit with illumination light. As one of the illumination devices, there is a planar illumination device that emits illumination light from the back of the image display unit. FIG. 11 is an exploded perspective view showing a conventional planar lighting device. The spread illuminating apparatus includes a light emitting diode 1 (hereinafter, referred to as “LED”) as a light emitting element serving as a light source, a flexible circuit board 2 (hereinafter, referred to as “FPC”) that transmits an electric signal for causing the LED 1 to emit light, and an LED 1. A light guide plate 4 for transmitting light emitted from the image display unit so that the light is emitted to the image display unit; and a case 3 for storing the FPC 2 and the light guide plate 4. The LED 1 is fixed to the FPC 2 by solder. The case 3 is provided with pins 3a and 3b, and the FPC 2 is fixed to the case 3 by the pins 3a and 3b. The case 3 is provided with a concave portion 3c, and the FPC 2 and the light guide plate 4 are stored in the concave portion 3c. The FPC 2 is provided with holes 2a and 2b. The holes 2a and 2b are reference holes for positioning for inserting the pins 3a and 3b. The light guide plate 4 is a flat plate or a wedge-shaped plate made of a transparent resin such as an acrylic resin, and is fixed by being inserted into a concave portion 3 c provided in the case 3. In the present description, the concave portion means a concave portion in the object, and the hole means a portion in the object where the concave penetrates from one surface to the opposite surface.
[0003]
In JP-A-9-81050, the LED 1 is fixed to the light guide plate 4 by inserting the LED 1 into the concave portion provided in the light guide plate 4, and the light guide plate 4 in which the LED 1 is inserted and the FPC 2 are thermally caulked or fixed. There has been proposed a method of joining with a hook (see Patent Document 1). FIG. 12 shows a partial cross-sectional view of this planar illumination device. In this spread illuminating device, the light guide plate 4 is provided with a recess 4b in advance in order to fix the LED1. In order to sandwich the LED 1 from the side, the recess 4b is provided with a protrusion 4c such that the interval is slightly smaller than the outer size of the LED 1. One recess 4b is provided with three or four protrusions 4c, and the LED 1 is inserted into the recess 4b while crushing these protrusions 4c. This prevents rattling of the LED 1 in the recess 4b. On the other hand, in order to electrically connect the FPC 2 and the LED 1, an anisotropic conductor 11, a conductive paste, or the like is bonded to the FPC 2 in advance. Then, the light guide plate 4 and the FPC 2 are joined by thermal caulking or fixing claws.
[0004]
[Patent Document 1]
JP-A-9-81050
[0005]
[Problems to be solved by the invention]
However, in the conventional technique shown in FIG. 11, a gap is formed between the LED 1 and the light guide plate 4, and there is a problem that the brightness is reduced due to the gap. It is necessary to provide a gap between the LED 1 and the light guide plate 4 in consideration of the following three points, which will be described with reference to FIGS. 11, 13 and 14. FIG. 13 is a partial cross-sectional view taken along the line AA of the spread illuminating apparatus shown in FIG. 11 in an assembled state. FIG. 14 is a partial cross-sectional view taken along line BB of the planar illumination device shown in FIG. 11 in an assembled state. Hereinafter, three points to be considered will be described in order.
[0006]
The first point is the positional accuracy between the reference holes 2a and 2b of the FPC 2 and the LED 1 in the Z direction in FIG. Hereinafter, the dimension (position error) of the position accuracy is referred to as “X1”. The positions of the reference holes 2a and 2b of the FPC 2 and the positions of the LEDs 1 are different between the individual FPCs 2 due to a manufacturing error of each member. That is, assuming that the reference hole 2a and the reference hole 2b are connected by a straight line, the distance between the straight line and the light emitting surface of each LED 1 is not constant. Therefore, it is necessary to consider the position accuracy X1.
[0007]
The second point is a gap caused by the difference between the dimensions of the reference holes 2a and 2b provided in the FPC 2 and the dimensions of the pins 3a and 3b provided in the case 3 (hereinafter, the dimension of this gap is referred to as "X2"). It is. When there is no gap, it is extremely difficult to insert the pins 3a and 3b provided in the case 3 into the reference holes 2a and 2b. Therefore, it is necessary to consider the gap X2.
[0008]
The third point is a gap between the pins 3a and 3b provided in the case 3 and the light guide plate 4 (hereinafter, the dimension of this gap is referred to as “X3”). When there is no gap between the pins 3a and 3b provided in the case 3 and the light guide plate 4, it is extremely difficult to insert the light guide plate 4 into the case 3. Therefore, it is necessary to consider the gap X3.
[0009]
As described above, it is necessary to provide a gap having a dimension of X2 + X3, and it is necessary to consider the positional accuracy X1 between individuals. Therefore, unless the gap of the dimension X1 + X2 + X3 is provided between the LED 1 and the light guide plate 4, the light guide plate 4 cannot be inserted into the case 3 in some cases. Therefore, a gap having a dimension of X1 + X2 + X3 is provided between the LED 1 and the light guide plate 4, as shown in FIG.
[0010]
The gap as described above causes a decrease in luminance in the lighting device. In addition, this may cause a variation in luminance between individual lighting devices. FIG. 15 is a diagram showing the relationship between the gap between the LED 1 and the light guide plate 4 and the luminance ratio. Here, the brightness when the gap is 0.2 mm is set to 1. As shown in FIG. 15, it can be seen that the luminance of the lighting device decreases as the gap increases. Therefore, the prior art shown in FIG. 11 has a problem that the brightness is reduced due to the gap between the LED 1 and the light guide plate 4.
[0011]
Further, in the related art shown in FIG. 12, by inserting the LED 1 into the concave portion 4b of the light guide plate 4, the prevention of a decrease in luminance due to the gap between the LED 1 and the light guide plate 4 is realized. However, there is a dimensional error between the individual LEDs 1, and the shape of the concave portion 4 b differs between the individual light guide plates 4. In addition, since there is a difference in the thermal expansion coefficient between the LED 1 and the light guide plate 4, a dimensional error occurs due to a change in ambient temperature. Therefore, an error may occur in the left and right directions in FIG. 12 between the individual lighting devices, and rattling of the LED 1 may occur in the recess 4 b of the light guide plate 4. When there is such rattling, the light guide plate 4 and the LED 1 may collide with each other and be damaged when receiving an external shock or vibrating. In addition, in FIG. 12, an error may occur in the vertical direction, and the electrical connection between the LED 1 and the FPC 2 may be insufficient, so that sufficient electrical continuity cannot be guaranteed. As described above, in the related art, it is very difficult to attach the LED 1 to the light guide plate 4 so that rattling is prevented and electrical connection is sufficient.
[0012]
Therefore, an object of the present invention is to provide a spread illuminating device in which a light emitting element can be easily attached to a light guide plate and light utilization efficiency is good.
[0013]
[Means for Solving the Problems]
A first invention is a planar lighting device that emits light incident from a light incident surface that is a predetermined side surface of a light guide plate as illumination light from a main surface of the light guide plate,
Equipped with a light emitting element serving as a light source,
The light emitting surface of the light emitting element may be bonded to a light incident surface of the light guide plate with a transparent fixing material.
According to the first aspect, the light emitting element and the light guide plate are bonded by the transparent fixing member. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance.
[0014]
In a second aspect based on the first aspect, the light guide plate has a recess or a hole,
The light emitting device is characterized in that the light emitting device is inserted into and bonded to the recess or the hole.
According to the second aspect, similarly to the first aspect, the light emitting element and the light guide plate are bonded by the transparent fixing member. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance.
[0015]
A third invention is characterized in that, in the first invention and the second invention, the light emitting element is a light emitting diode.
According to the third aspect, similarly to the first aspect, the light emitting element and the light guide plate are bonded by the transparent fixing member. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance. In addition, light emission loss is further reduced.
[0016]
In a fourth aspect based on the first to third aspects, the transparent fixing member is a UV adhesive.
According to the fourth aspect, similarly to the first aspect, the light emitting element and the light guide plate are bonded by the transparent fixing member. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance. In addition, it is also possible to prevent luminance unevenness.
[0017]
In a fifth aspect based on the first to third aspects, the transparent fixing member is a transparent double-sided tape.
According to the fifth aspect, similarly to the first aspect, the light emitting element and the light guide plate are bonded by the transparent fixing member. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance.
[0018]
A sixth invention is a planar lighting device that emits light incident from a light incident surface that is a predetermined side surface of a light guide plate as illumination light from a main surface of the light guide plate,
A light emitting element serving as a light source,
A circuit board that transmits an electric signal for causing the light emitting element to emit light,
The surface of the light guide plate other than the light incident surface and the circuit board are bonded by a fixing member having a property of reflecting light.
According to the sixth aspect, the circuit board and the light guide plate are easily bonded by the fixing member having a property of reflecting light. Therefore, leakage of light to the outside is prevented, and rattling does not occur. This can provide a spread illuminating device in which a decrease in luminance is prevented and damage due to impact is prevented.
[0019]
A seventh invention is characterized in that, in the sixth invention, the fixing member is a double-sided tape in which an adhesive layer is provided on both surfaces of a sheet that reflects light.
According to the seventh aspect, similarly to the sixth aspect, the circuit board and the light guide plate are easily bonded by the fixing member having a property of reflecting light. Therefore, leakage of light to the outside is prevented, and rattling does not occur. This can provide a spread illuminating device in which a decrease in luminance is prevented and damage due to impact is prevented.
[0020]
An eighth invention is a liquid crystal display device including any one of the first to seventh planar illumination devices.
According to the eighth aspect, the liquid crystal display device including the planar illumination device in which the light emitting element and the light guide plate can be easily attached without lowering the luminance, and the luminance reduction and damage due to impact are prevented. A liquid crystal display device provided with a spread illuminating device can be provided.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
<1. First Embodiment>
<1.1 Configuration of spread illuminating device>
1 and 2 are perspective views of a spread illuminating apparatus according to a first embodiment of the present invention. Here, FIG. 1 shows a state before the light guide plate 4 is attached to the case 3, and FIG. 2 shows a state after the light guide plate 4 is attached to the case 3. FIG. 3 is a partial sectional view taken along line CC of FIG. The spread illuminating device constitutes a part of a display device such as a liquid crystal display device, and the display device has an image display unit for displaying an image on an irradiation side of light emitted from the spread illuminating device. Is provided. The spread illuminating apparatus includes an LED 1 that is a light emitting element serving as a light source, an FPC 2 that transmits an electric signal for causing the LED 1 to emit light, and a light guide plate 4 that transmits light emitted from the LED 1 so that the image display unit is irradiated. And a case 3 for storing at least the FPC 2 and the light guide plate 4, and an optical sheet 9 for irradiating the image display unit with light passing through the light guide plate 4. Note that the optical sheet is, for example, a lens sheet or a light diffusion sheet.
[0022]
<1.2 Assembly of the planar lighting device>
When assembling the planar lighting device according to the present embodiment, first, the LED 1 is attached to the FPC 2. At that time, in order to obtain uniform surface light emission in the light guide plate 4, the LEDs 1 are arranged on the FPC 2 as shown in FIG. As shown in FIG. 3, the individual LEDs 1 are fixed to the FPC 2 with solder 7. Then, the FPC 2 is fixed to the case 3 so that the light emitted from the LED 1 is incident on one side surface 4 a of the light guide plate 4. After that, the light guide plate 4 is inserted into the case 3. At this time, the LED 1 and the light guide plate 4 are bonded with a transparent fixing material. In the present description, a material that is interposed between the two and fixedly connected to each other is referred to as a fixing material. In the present embodiment, a transparent UV curable resin 5 is used as the fixing material. A transparent UV curable resin 5 is injected between the light emitting surface of the LED 1 and the light incident surface 4a of the light guide plate 4 with a dispenser 8, and the LED 1 and the light guide plate 4 are bonded by irradiating UV light. In this embodiment, the transparent UV curable resin 5 is used for bonding the light emitting surface of the LED 1 and the light incident surface 4 a of the light guide plate 4. However, a transparent fixing material is limited to the UV curable resin 5. Instead, for example, a transparent double-sided tape may be used. As described above, by bonding the LED 1 and the light guide plate 4 with the transparent UV curable resin 5, the gap between the LED 1 and the light guide plate 4 becomes smaller than that of the conventional planar lighting device, and the backlash is also increased. Is also prevented.
[0023]
<1.3 UV curable resin>
Next, the UV curable resin 5 used in the present embodiment will be described from the viewpoint of luminance unevenness in the light guide plate 4. The light passing through the light guide plate 4 is emitted from the front surface of the light guide plate 4 toward the back surface of the image display unit. A state in which the brightness of the emitted light varies depending on the position on the surface of the light guide plate 4 is called uneven brightness. . FIG. 4 is a partial plan view of the vicinity of the LED 1 of the surface illumination device as viewed from above. In this planar illumination device, four LEDs 1 are arranged side by side on the FPC 2 in order to obtain uniform surface light emission in the light guide plate 4. However, since the individual LEDs 1 emit point light, the portion indicated by M in FIG. 4 may be dark. Therefore, it is necessary to emit light from the LED 1 in a wide range. For this reason, in the present embodiment, the UV curable resin 5 having a refractive index of 1.33 or more, more preferably the refractive index of the material of the light guide plate 4 is used. It is assumed that the UV curable resin 5 having the same ratio of about 1.5 is used. Hereinafter, the reason will be described.
[0024]
In general, when light travels from a substance having a refractive index of n1 to a substance having a refractive index of n2, if the incident angle of light at the interface between the two substances is θ1 and the emission angle of light is θ2, the following equation is obtained from Snell's law. (1) holds.
n1 × sin θ1 = n2 × sin θ2 (1)
According to the above equation (1), when θ1 and n2 are constant, θ2 increases as n1 increases. Here, when the UV curable resin 5 having a refractive index smaller than the conventional value of n1 of 1.33 is used, θ2 becomes smaller than before and a dark portion is generated between the LEDs 1. Therefore, the UV curable resin 5 having a refractive index of 1.33 or more is used. In addition, when the UV curable resin 5 whose refractive index is around 1.5 which is the same as the refractive index of the material of the light guide plate 4 is used, θ1 and θ2 in the above equation (1) are close values. That is, the light emitted from the LED 1 enters the light guide plate 4 from the boundary surface while maintaining the emission angle, and the effect of further preventing luminance unevenness can be obtained.
[0025]
On the other hand, when the refractive index of the UV curable resin 5 is set to 1.33 or more, light leaks from the upper surface and the lower surface of the light guide plate 4 in a portion indicated by L in FIG. Therefore, a reflection member is provided in the portion indicated by L. As a result, the light that leaks out without the reflection member is used as light transmitted through the light guide plate 4.
[0026]
As described above, in the present embodiment, the LED and the light guide plate are bonded by the transparent UV curable resin. Therefore, the gap between the LED and the light guide plate is reduced. Furthermore, since the LED and the light guide plate are integrated by being adhered with a UV curable resin, rattling is prevented, and the mounting operation is simple. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate are easily attached without lowering the luminance, and the damage due to the impact is prevented.
[0027]
<2. Second Embodiment>
FIG. 5 is a partial perspective view of the spread illuminating apparatus according to the second embodiment of the present invention. FIG. 6 is a partial sectional view taken along line DD of FIG. In this embodiment, a hole for inserting and bonding the LED 1 is provided in the light guide plate 4. Here, since there is a dimensional error between the individual LEDs 1 and between the individual light guide plates 4, the size of the hole is assumed to be the size of the LED 1 plus the dimensional error. Thus, the LED 1 is easily inserted into the hole.
[0028]
Next, a method of bonding the light guide plate 4 and the LED 1 will be described. In FIG. 5, the surface of the side surface of the hole provided in the light guide plate 4 on which the light emitted from the LED 1 enters the inside of the light guide plate 4 is denoted by reference numeral “4a”. As in the first embodiment, four LEDs 1 are fixed to the FPC 2 with solder. Then, the four LEDs 1 fixed to the FPC 2 are inserted into four holes provided in the light guide plate 4 respectively. A transparent UV curing resin 5 is injected between the light emitting surface of the LED 1 and the light incident surface 4a, and the LED 1 and the light guide plate 4 are bonded by irradiating UV light. Thereafter, the member integrated as described above is inserted into the case 3. Thereby, as shown in FIG. 6, since the LED 1 and the light guide plate 4 are bonded by the UV curing resin 5, the gap between the LED 1 and the light guide plate 4 is small, and a decrease in luminance is prevented. In the present embodiment, the UV curable resin 5 is injected after the LED 1 is inserted into the hole of the light guide plate 4. However, after the UV curable resin 5 is applied to the light incident surface 4 a of the hole of the light guide plate 4, the LED 1 is connected to the hole. It may be inserted into the part. Further, in this embodiment, the transparent UV-curable resin 5 is used to bond and fix the light-emitting surface of the LED 1 and the light-incident surface 4a of the light guide plate 4, but if a transparent fixing material is used, the UV-curable resin is used. For example, a transparent double-sided tape may be used. Further, in the present embodiment, the LED 1 is provided in the hole for inserting the LED 1 into the light guide plate 4, but the light guide plate 4 may be provided with a concave portion.
[0029]
As described above, in the present embodiment, a hole is provided in the light guide plate, and the LED is bonded to the hole with a transparent UV curable resin. Therefore, the gap between the LED and the light guide plate is reduced. Furthermore, since the LED and the light guide plate are integrated by being adhered with a UV curable resin, rattling is prevented, and the mounting operation is simple. As a result, similarly to the first embodiment, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance, and damage due to impact is prevented.
[0030]
<3. Third Embodiment>
FIG. 7 is a partial cross-sectional view of the spread illuminating apparatus according to the third embodiment of the present invention. FIG. 8 is a diagram illustrating a part of a light path in the planar lighting device according to the present embodiment. In the present embodiment, the light guide plate 4 and the FPC 2 are bonded by a fixing member having a property of reflecting light. The LED 1 is fixed to the FPC 2 with solder as in the first embodiment. Further, a double-sided tape 6 with a reflection sheet is attached to the FPC 2. After that, the light guide plate 4 is adhered to the FPC 2 by the double-sided tape 6 with a reflection sheet attached to the FPC 2.
[0031]
Next, the double-sided tape 6 with a reflection sheet will be described with reference to FIG. FIG. 9 is an enlarged view of a portion indicated by F in FIG. The double-sided tape with a reflection sheet is composed of a reflection sheet 6a for reflecting light emitted from the LED 1, an adhesive 6b for attaching the light guide plate 4, and an adhesive 6c for attaching the FPC2. I have. An adhesive 6b is applied to the light incident surface side of the reflection sheet 6a, and an adhesive 6c is applied to the opposite surface. The light emitted from the LED 1 passes through the light guide plate 4 and then through the adhesive 6b. Here, when the reflection sheet 6a is not provided, light is transmitted in the direction of 10b and becomes light leakage. However, when the reflection sheet 6a is provided, the light is reflected in the direction of 10a, and is used as effective light for illumination. Since the adhesive 6c does not affect the light incident from the light guide plate 4, it may be transparent or opaque.
[0032]
In this embodiment, the double-sided tape 6 with a reflective sheet is attached to the FPC 2 after fixing the LED 1 to the FPC 2. Good. Further, the light guide plate 4 is adhered to the FPC 2 after the double-sided tape 6 with a reflection sheet is adhered thereto. 6 may be used.
[0033]
As described above, in the present embodiment, the light guide plate and the FPC are bonded by the fixing member having the property of reflecting light. For this reason, leakage of light to the outside is prevented, and rattling does not occur because the light guide plate and the FPC are integrated by bonding. This can provide a spread illuminating device in which a decrease in luminance is prevented and damage due to impact is prevented.
[0034]
<4. Modification 1>
FIG. 10 is a partial cross-sectional view of a planar lighting device according to a modification of the third embodiment. In the third embodiment, the FPC 2 is arranged below the light guide plate 4, but in this modification, the FPC 2 is arranged above the light guide plate 4. For this reason, in the third embodiment, the case 3 is provided with a thickness corresponding to the thickness of the FPC 2, but in this modification, the case 3 does not need a thickness corresponding to the thickness of the FPC 2. Thereby, an effect that the thickness of the planar lighting device can be reduced is obtained.
[0035]
<5. Modification 2>
In the third embodiment, an adhesive made of a transparent material is applied to both surfaces of the reflection sheet. However, in this modification, the upper surface of the reflection sheet, that is, the adhesive 6b in FIG. 9 is made of a milky or translucent material. It is an adhesive made of Therefore, the light 10 that has passed through the light guide plate 4 is scattered by the adhesive 6b. Thereby, the effect of preventing luminance unevenness can be obtained. Further, when an omnidirectional scattering sheet is used as the reflection sheet 6a, the light 10 is scattered in each direction. As a result, a further effect of preventing luminance unevenness can be obtained. The omnidirectional scattering sheet includes, for example, a white sheet.
[0036]
【The invention's effect】
According to the first invention, the light emitting element and the light guide plate are bonded by the transparent fixing material. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance.
[0037]
According to the second invention, similarly to the first invention, the light emitting element and the light guide plate are bonded by the transparent fixing material. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance.
[0038]
According to the third invention, as in the first invention, the light emitting element and the light guide plate are bonded by a transparent fixing material. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance. In addition, light emission loss is further reduced.
[0039]
According to the fourth aspect, as in the first aspect, the light emitting element and the light guide plate are bonded by a transparent fixing material. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. This makes it possible to provide a planar lighting device in which the light emitting element and the light guide plate can be easily attached without lowering the luminance. In addition, it is also possible to prevent luminance unevenness.
[0040]
According to the fifth aspect, as in the first aspect, the light emitting element and the light guide plate are bonded by a transparent fixing material. Therefore, the gap between the light emitting element and the light guide plate is reduced by a simple attaching operation. Accordingly, it is possible to provide a spread illuminating apparatus in which the light emitting element and the light guide plate can be easily attached without lowering the luminance.
[0041]
According to the sixth aspect, the circuit board and the light guide plate are easily bonded to each other by the fixing member having a property of reflecting light. Therefore, leakage of light to the outside is prevented, and rattling does not occur. This can provide a spread illuminating device in which a decrease in luminance is prevented and damage due to impact is prevented.
[0042]
According to the seventh aspect, similarly to the sixth aspect, the circuit board and the light guide plate are easily bonded by the fixing member having a characteristic of reflecting light. Therefore, leakage of light to the outside is prevented, and rattling does not occur. This can provide a spread illuminating device in which a decrease in luminance is prevented and damage due to impact is prevented.
[0043]
According to the eighth aspect, the liquid crystal display device including the planar illumination device in which the light emitting element and the light guide plate can be easily attached without lowering the luminance, and the planar shape in which the luminance is reduced and damage due to impact is prevented. A liquid crystal display device including a lighting device can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a state of a spread illuminating apparatus according to a first embodiment of the present invention before a light guide plate is attached to a case.
FIG. 2 is a perspective view showing a state of the spread illuminating apparatus according to the first embodiment of the present invention after a light guide plate is attached to a case.
FIG. 3 is a partial sectional view taken along line CC of FIG. 2;
FIG. 4 is a partial plan view of the vicinity of the LED of the spread illuminating apparatus according to the first embodiment of the present invention as viewed from above.
FIG. 5 is a partial perspective view of a spread illuminating apparatus according to a second embodiment of the present invention.
FIG. 6 is a partial sectional view taken along line DD of FIG. 5;
FIG. 7 is a partial sectional view of a spread illuminating apparatus according to a third embodiment of the present invention.
FIG. 8 is a diagram illustrating a part of a light path of a spread illuminating apparatus according to a third embodiment of the present invention.
FIG. 9 is a partially enlarged view of a spread illuminating apparatus according to a third embodiment of the present invention.
FIG. 10 is a partial cross-sectional view of a surface illumination device according to a modification of the third embodiment of the present invention.
FIG. 11 is an exploded perspective view showing a conventional planar lighting device.
FIG. 12 is a partial cross-sectional view of a conventional planar illumination device.
13 is a partial cross-sectional view taken along line AA of the spread illuminating apparatus shown in FIG. 11 in an assembled state.
14 is a partial cross-sectional view taken along line BB of the planar lighting device shown in FIG. 11 in an assembled state.
FIG. 15 is a diagram illustrating a relationship between a gap between an LED and a light guide plate and a luminance ratio.
[Explanation of symbols]
1: Light-emitting element (LED)
2. Flexible circuit board (FPC)
3… Case
4: Light guide plate
4a: Light incident surface on the light guide plate
5 UV curing resin
6 ... Double-sided tape with reflective sheet
6a: Reflective sheet
6b ... adhesive
6c ... Adhesive
7 ... Solder
9 Optical sheet
10. Light passing through the light guide plate
10a: Light reflected by the reflection sheet
10b: Light leaking from the light guide plate to the outside

Claims (8)

A planar lighting device that emits light incident from a light incident surface that is a predetermined side surface of a light guide plate as illumination light from a main surface of the light guide plate,
Equipped with a light emitting element serving as a light source,
A planar lighting device, wherein a light emitting surface of the light emitting element is bonded to a light incident surface of the light guide plate with a transparent fixing material. The light guide plate has a recess or a hole,
The spread illuminating apparatus according to claim 1, wherein the light emitting element is inserted into and bonded to the recess or the hole. The planar lighting device according to claim 1, wherein the light emitting element is a light emitting diode. The spread illuminating device according to claim 1, wherein the transparent fixing member is a UV adhesive. The spread illuminating device according to any one of claims 1 to 3, wherein the transparent fixing member is a transparent double-sided tape. A planar lighting device that emits light incident from a light incident surface that is a predetermined side surface of a light guide plate as illumination light from a main surface of the light guide plate,
A light emitting element serving as a light source,
A circuit board that transmits an electric signal for causing the light emitting element to emit light,
A surface illumination device, wherein a surface of the light guide plate other than the light incident surface and the circuit board are bonded by a fixing member having a property of reflecting light. The spread illuminating apparatus according to claim 6, wherein the fixing member is a double-sided tape in which an adhesive layer is provided on both sides of a sheet that reflects light. A liquid crystal display device comprising the planar illumination device according to any one of claims 1 to 7.

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