JPH09145935A - Back lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a back lighting device thin, improve the light utilization efficiency, and obtain high luminance and reduce the power consumption by guiding light, projected on a 1st curved-surface side by a light source, to below a light emission surface by repeating reflection by a 2nd curved surface and a 2nd reflecting member. SOLUTION: A hole is formed in the light guide plate 1 which has a side end surface formed out a light emission surface 1b and 1st curved surface 1c, and the light source 2 is inserted into a lamp house 1d which is positioned nearby the side end surface and has its side end surface side shaped with the 2nd curved surface 1e. A 1st reflecting member 3 which reflects the light from the light source 2 to the light emission surface 1b is provided on the surface facing the light emission surface 1b and the 2nd reflecting member 5 is provided which reflects the light from the light source 2 projected from the side end surface to the inside of the light guide plate 1. And, the light which is projected to the 1st curved surface 1c by the light source 2 is repeatedly reflected by the 2nd curved surface 1e and 2nd reflecting member 5 and guided to below the light emission surface. Consequently, more light can be transmitted, the light utilization efficiency is improved, and a high luminance and low power consumption are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back lighting device for surface lighting, and more particularly to a back lighting device such as a backlight used in a liquid crystal display.

[0002]

2. Description of the Related Art FIG. 11 is a diagram for explaining a conventional back lighting device for surface lighting, which is disclosed in Japanese Patent Laid-Open No. 6-167617. In FIG. 11, reference numeral 1 is a light guide plate having a property of transmitting light, and the light guide plate 1 is made of, for example, a resin such as acrylic. Reference numeral 2 denotes a light source, and the light source 2 is, for example, a rod-shaped hot cathode fluorescent tube or cold cathode fluorescent tube. Reference numeral 3 denotes a reflecting member that reflects the light emitted from the light source 2 and introduced into the light guide plate 1. The reflecting member 3 faces, for example, the light emitting surface 1b (hereinafter referred to as the bottom surface of the light guide plate 1). Is provided with a dot-shaped reflection pattern. Reference numeral 1a is a light introducing portion provided on the side end surface of the light guide plate 1 for introducing light from the light source 2, and the light introducing portion 1a is
For example, it is formed by polishing the end portion of the light guide plate 1 into a mirror surface. The light emitting surface 1b emits light from the surface of the light guide plate 1. The light emitting surface 1b emits light when the light from the light source 2 enters at an angle smaller than the critical angle of the light guide plate.
As a result, the back lighting device illuminates the surface from the light emitting surface.

The light source 2 is installed adjacent to the light introducing portion 1a of the light guide plate 1. Also, the diameter of the light source 2 depends on the light guide plate 1.
Greater than the thickness of. The light incident on the reflecting member 3 is reflected toward the light emitting surface 1b. Since the reflection member 3 is arranged on the bottom surface of the light guide plate 1 with its density changed so that the luminance distribution of the light emitting surface 1b is uniform, it is possible to display an image without unevenness. For example, the above-described function can be realized by arranging the reflection member 3 arranged on the bottom surface of the light guide plate 1 so that the density occupied by the surface of the light guide plate 1 increases as the distance from the light source 2 increases.

Reference numeral 10 denotes a reflecting member. By disposing the reflecting member 10 on the bottom surface of the light guide plate 1, it is possible to return the light emitted from the boundary of the light guide plate 1 to the inside of the light guide plate 1 again. Reference numeral 4 denotes a reflecting member, and the reflecting member 4 is attached to at least the side end surface facing the light introducing portion 1a.
By attaching the reflection member 4, leakage of light from the side end surface of the light guide plate 1 is prevented, and this light is again emitted.
Can be put back inside. Reference numeral 5 denotes a reflecting member, for example, the reflecting member 5 is formed by attaching a tape on which a metal such as silver is vapor-deposited to the end portion of the light guide plate 1 on the side of the light introducing portion 1a so as to cover the light source 2. Reference numeral 6 denotes a lens sheet provided on the light emitting surface 1b of the light guide plate 1. The lens sheet 6 is the light guide plate 1
In order to improve the directivity of the light and improve the brightness in the direction normal to the panel surface, the surface has minute irregularities (not shown), and the surface with this irregularity faces the outside air. ing. Reference numeral 15 is an air layer formed inside the reflection member 5.

Next, the operation will be described. The conventional edge lighting type back lighting device is configured as described above, and when a cold cathode fluorescent tube is used as the light source 2, for example, an inverter (not shown) turns on AC light at a frequency of about 40 kHz to emit light. Of the light from the light source 2, the light that directly enters the light introducing portion 1 a is guided to the inside of the light guide plate 1 as direct light. The light that cannot be directly incident on the light introducing portion 1a, that is, the light emitted from the light source toward the reflecting member 5 is also reflected by the reflecting member 5. Since a part of the light reflected from the reflecting member 5 is guided to the light introducing portion 1a, this light is guided into the light guide plate 1 as indirect light. These light introducing sections 1a
The guided light from the light source 2 is transmitted while being repeatedly reflected inside the light guide plate 1. At this time, when the transmitted light is incident on the reflecting member 3, this light is reflected on the light emitting surface side, and when this light is incident on the light emitting surface 1b at an angle smaller than the total reflection angle of the light guide plate 1, the light emitting surface is formed. By further emitting light through the lens sheet 6, the back lighting device illuminates the surface from the light emitting surface 1b. With the above-described operation, the light emitted from the light source 2 can be surface-illuminated from the light emitting surface 1b.

[0006]

In the conventional back lighting device, since the diameter of the light source 2 is larger than the thickness of the light guide plate 1, the thickness of the back lighting device is thinner than the diameter of the light source 2. The problem was that I could not do it. Further, in the conventional back lighting device, although a part of the light which is not directly incident on the light introducing portion 1a is guided into the light guide plate 1 as indirect light, most of the light is reflected by the reflecting member 5 once or plural times. After that, since it is reabsorbed by the light source 2, it is difficult to effectively guide the light to the light introducing portion 1a. Further, there is an air layer 15 between the light guide plate 1 and the light source 2, and some of the light reaching the light introducing portion 1a is also reflected at the boundary surface between the air layer 15 and the light introducing portion 1a. The amount of light that can actually be guided into the light guide plate is about 60% of the total amount of light of the light source 2, which is the light source,
The light utilization efficiency was low. Therefore, when the conventional back lighting device is used for the back lighting of a liquid crystal display or the like, the light source 2 having a brightness value higher than the designed value of the brightness value on the light emitting surface is required, and the power consumption of the light source 2 is high. It was a problem in promoting the power saving of the display unit.

Further, in many cases, the reflection member 5 is simply an adhesive tape formed by vapor-depositing a metal such as silver on the end of the light guide plate 1 so as to cover the light source. Since the positional relationship is not fixed, there are variations in the performance of individual back lighting devices such as the brightness value on the light emitting surface and its uniformity depending on the product.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a thin back lighting device. Another object of the present invention is to improve the light utilization efficiency of the light source 2 and obtain a back lighting device with high brightness and low power consumption. Another object is to reduce the variation of each product such as the brightness value and its uniformity on the light emitting surface by adopting a structure in which the shape of the reflecting member 5 and the positional relationship with the light source 2 are fixed.

[0009]

According to another aspect of the present invention, there is provided a back lighting device comprising a light guide plate having a side surface formed by a light emitting surface and a first curved surface, and a hole formed in the light guide plate. A lamp house located near the side end face and having a shape of the side end face side formed by a second curved surface, a light source to be inserted into this lamp house, and a face opposite to the light emitting surface, emitting light from the light source It is provided with a first reflecting member that reflects toward the surface and a second reflecting member that reflects light from the light source emitted from the side end surface toward the inside of the light guide plate.

According to the second aspect of the present invention, the interior of the lamp house is filled with a substance having a refractive index larger than that of air and smaller than that of the light guide plate.

According to a third aspect of the present invention, there is provided a back lighting device including a light diffusing portion for reflecting the light reflected by the second reflecting member in a part of the periphery of the lamp house.

According to a fourth aspect of the present invention, there is provided a back lighting device comprising a light guide plate having a light emitting surface and a hole formed in the light guide plate.
A lamp house located near the center of the light guide plate, a light source to be inserted into the lamp house, a light blocking member for blocking a part of the light emitted from the light source toward the light emitting surface, and a surface facing the light emitting surface. And a reflecting member that is positioned and reflects the light from the light source toward the light emitting surface.

According to the fifth aspect of the present invention, the interior of the lamp house is filled with a substance having a refractive index larger than that of air and smaller than that of the light guide plate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a diagram showing the configuration of the back lighting device of the first embodiment and is a cross-sectional view perpendicular to the light emitting surface. In FIG. 1, the components having the same reference numerals as those of the conventional back lighting device are the same as or equivalent to those of the conventional one. In FIG. 1, reference numeral 1 denotes a light guide plate having a property of transmitting light, and the light guide plate 1 is made of a transparent resin such as acrylic. Reference numeral 2 denotes a light source, which is a light source such as a rod-shaped hot cathode fluorescent tube or cold cathode fluorescent tube in the first embodiment, and the outer diameter thereof is smaller than the thickness of the light guide plate. In the first embodiment, the outer diameter of the light source 2 has a size of, for example, about 3 mm, and the thickness of the light guide plate 1 is larger than this. Reference numeral 3 denotes a reflecting member that reflects the light emitted from the light source 2. The reflecting member 3 that is the first reflecting member faces, for example, the light emitting surface 1b (hereinafter referred to as the bottom surface of the light guide plate 1). Is provided with a dot-shaped reflection pattern. A light emitting surface 1b emits light from the surface of the light guide plate 1, and emits light emitted from the light source 2 from the light emitting surface 1b. As a result, the back lighting device illuminates the surface from the light emitting surface 1b. Reference numeral 1c denotes a curved surface portion in which the side end surface of the light guide plate 1 is formed into a curved surface by polishing or the like. The shape of the cross section of the curved surface portion 1c, that is, the cross section perpendicular to the light emitting surface 1b has a curved line such as an arc, a parabola, or an ellipse.

Reference numeral 1d denotes a hollow lamp house formed by forming a hole or the like near the side end surface of the light guide plate 1 on the side of the curved surface 1c which is the first curved surface. Air exists inside the lamp house 1d. The size of the lamp house 1d is large enough to insert the light source 2. Reference numeral 1e denotes a boundary surface on the curved surface portion 1c side of the light guide plate 1 of the lamp house 1d, which is a curved surface portion formed to have a curved shape. The cross section of the curved surface portion 1e which is the second curved surface, that is, the shape of the cross section perpendicular to the light emitting surface 1b is 2 such as an arc, an ellipse, or a parabola.
It has a quadratic curve. Reference numeral 1a is a boundary surface between the lamp house 1d and the light guide plate 1, and is a light introducing portion having a flat boundary surface. The cross section of the light introducing portion 1a, that is, the cross section perpendicular to the light emitting surface 1b has a straight line shape.

In the first embodiment, the light introducing portion 1a is formed by, for example, polishing the boundary surface between the light guide plate 1 and the lamp house 1d into a mirror surface. The light source 2 is inserted inside the lamp house 1d and is installed adjacent to the light introducing portion 1a.

Since the reflecting member 3 is arranged on the bottom surface of the light guide plate 1 with its density varied so that the luminance distribution of the light emitting surface 1b becomes uniform, it is possible to display a uniform image. For example, the reflection member 3 disposed on the bottom surface of the light guide plate 1.
By arranging so that the density occupied on the surface of the light guide plate 1 increases as the distance from the light source 2 increases, the above-described function can be realized.

Reference numeral 10 is a reflecting member, and a plate-like member is used in the first embodiment. By attaching the reflection member 10 to the bottom surface of the light guide plate 1, it is possible to return the light emitted from the bottom surface of the light guide plate 1 to the inside of the light guide plate 1 again.
Further, when the reflection member 10 is attached to the bottom surface of the light guide plate 1, a thin air layer (not shown) is formed between the reflection member 10 and the light guide plate 1. Reference numeral 5 is a reflection member that serves as a second reflection member. For example, the reflection member 5 that is the second reflection member is attached to the end of the light guide plate 1 so as to cover the curved surface portion 1c with a tape or the like on which a metal such as silver is deposited. It is pasted. Reference numeral 6 denotes a lens sheet provided on the light emitting surface 1b of the light guide plate 1. The lens sheet 6 has minute unevenness (not shown) on the surface in order to improve the directivity of light of the light guide plate 1 and improve the brightness in the direction normal to the panel surface. It is attached so that it faces the outside air.

In the back lighting device of the first embodiment, since the lamp house 1d is formed inside the light guide plate 1, the back lighting device can be thinner than the conventional back lighting device.

Further, by having the curved surface portion 1e, when the light reflected from the reflecting member 5 enters the curved surface portion 1e at an angle larger than the critical angle of the light guide plate 1, the light is reflected by the curved surface portion 1e. It is possible to transmit the light emitted to the curved surface portion 1c side toward the reflecting member 4 side. This will be described with reference to FIG. FIG. 2 is a diagram showing how the light emitted from the light source 2 toward the curved surface portion 1c is transmitted toward the reflecting member 4 side in the back lighting device of the first embodiment. In FIG. 2, reference numeral 2a denotes a path of light emitted from the light source 2 toward the curved surface portion 1c. As shown in FIG. 2, the light emitted from the light source 2 toward the curved surface portion 1c is repeatedly reflected by the reflecting member 5 and the curved surface portion 1e, and then transmitted to the reflecting member 4 side. Therefore, the light that has been re-absorbed by the light source 2 from the reflection member 5 in the related art can be transmitted toward the reflection member 4 side by the reflection member 5 and the curved surface portion 1e, so that the light utilization efficiency is improved.

Further, by making the light introducing portion 1a a plane, all the light introduced into the inside of the light guide plate 1 from this portion is reflected by the bottom surface of the light guide plate 1 or the reflecting member 3.
This will be described with reference to FIG. FIG. 3 shows that in the back lighting device according to the first embodiment, after the light emitted from the light source 2 (not shown) inserted in the lamp house 1d enters the light introducing portion 1a, it travels through the light guide plate 1 and is guided. It is a figure which shows the state which reached the bottom face of the optical board 1. Here, the refractive index n _{1 of} air is 1, and the refractive index of the light guide plate 1 is n ₂ . Further, the incident angle when the light emitted from the light source 2 enters the light introducing portion 1a is θ,
The emission angle is α, and the critical angle when the light traveling in the light guide plate 1 enters the bottom surface of the light guide plate is θ _c .

When the light incident from the light introducing portion 1a reaches the bottom surface of the light guide plate 1 and the incident angle to the bottom surface of the light guide plate 1a becomes the critical angle θ _c , sin (θ _c ) = 1 / n ( 1) n = n ₂ / n ₁ (2). Further, at the boundary surface from the air layer in the lamp house 1d to the light introducing portion 1a, n ₁ × sin (θ) = n ₂ × sin (α) (3) holds, and the refraction angle α and the critical angle θ _{Since c} satisfies α + θ _c = π / 2 (4), between the incident angle θ and the refractive index n, there are equations (1) to (4) and sin ² (θ _c ) + cos ² (θ _{Since c} ) = 1 (5), there is a relationship of sin (θ) = (n ² -1) ^1/2 (6). From this, if acrylic (n ₂ = 1.49) is selected as the material of the light guide plate 1 so that n ² > 2, the light incident from the light introducing portion 1 a is totally reflected on the bottom surface of the light guide plate 1. This allows the light reaching the bottom surface of the light guide plate 1 to be directed to the light emitting surface 1b side, so that the amount of light emitted from the light emitting surface 1b increases and the brightness of the light emitting surface 1b increases.

The cross section of the lamp house 1d has a light source 2
Since there is air (not shown) between the light guide plate 1 and the light source 2, the refraction angle α of the light emitted from the light introducing portion 1a can be made smaller than the incident angle θ. It becomes possible, and the position where the light incident from the light introducing section 1a reaches the bottom surface of the light guide plate 1 can be brought closer to the reflecting member 4 side. Therefore, the light incident from the light introducing portion 1a can reach the bottom surface of the light guide plate 1 closer to the reflecting member 4, so that the brightness of the light emitting surface 1b near the reflecting member 4 is improved and the light emitting surface 1b of the light emitting surface 1b is improved. The brightness becomes uniform. Further, even if a light source having a smaller amount of light than the conventional one is used, the same brightness value as the conventional one can be obtained, and power saving can be realized.

Further, on the end face of the light guide plate 1 to which the light source 2 is attached, as a reflector for reflecting the light from the light source 2 so as to guide the light from the light source 2 to the light emitting surface 1b,
Since the reflecting member 5 is attached so as to cover the curved surface portion 1c, the shape of the reflecting member 5 is fixed to the shape of the curved surface portion 1c, and the relative positional relationship between the reflecting member 5 and the light source 2 is fixed. Therefore, it is possible to suppress variations in performance such as the brightness value of the panel surface or the uniformity thereof depending on the product, as compared with the related art. The reflecting member 5 is formed by adhering a tape on which metal such as silver is vapor-deposited onto the light guide plate 1, but is formed by directly vapor-depositing metal such as silver on the curved surface portion 1c of the light guide plate 1. You may.

Embodiment 2 FIG. 4 is a diagram showing a main part of a back lighting device according to the second embodiment and a main part of a conventional back lighting device, and is a view showing a cross section perpendicular to a light emitting surface. The back lighting device of the second embodiment is characterized in that a flat surface portion parallel to the light emitting surface 1b is formed as a boundary surface of the lamp house 1d. FIG. 4A is a diagram showing a main part of a conventional back lighting device. In FIG. 4A, 2a is a light source 2.
This is the path of the light emitted from toward the reflecting member 5 side.
FIG. 4B is a diagram showing a main part of the back lighting device according to the second embodiment. In FIG. 4B, reference numeral 1f denotes a boundary surface of the lamp house 1d that is close to the light emitting surface 1b, and is a flat surface portion formed by a plane such that the surface is parallel to the light emitting surface 1b. Reference numeral 2b is a path of light emitted from the light source 2 toward the curved surface portion 1c. In the conventional back lighting device shown in FIG. 4A, the light emitted from the light source 2 to the reflecting member 5 side is then reflected by the reflecting member 5, and the reflected light is also reflected by the light source 2. Reabsorbed.

On the other hand, the second embodiment shown in FIG.
The back lighting device of the above is the refractive index of the light guide plate 1 and the lamp house 1d.
The light emitted from the light source 2 due to the difference with the refractive index of the air in the inside is guided to the reflecting member 4 side by repeating the reflection by the reflecting member 5 and the reflection by the boundary surface of the lamp house 1d. become. Also, at this time, the flat portion 1
Of the light incident on f, the incident angle when entering the curved surface portion 1e side is larger than that when the flat surface portion 1f is the curved surface portion 1c, so that it is more likely to be reflected and more light is reflected. It becomes possible to lead to the member 4 side.

As described above, in the back lighting device of the second embodiment, since the air layer is provided inside the lamp house 1d in which the light source 2 is installed, the air enters through the air layer into the light guide plate 1 and the lamp reflecting member 5 again. The light reflected in the direction of the light source 2 is partially totally reflected at the boundary between the light guide plate and the lamp house and transmitted toward the reflection member 3 side inside the light guide plate 1. For example, when acrylic (refractive index n ₂ = 1.49) is used as the material of the light guide plate 1, the critical angle θ _c of total reflection at the acrylic-air interface is _calculated from the equations (1) and (2). θ _c = 42
(Degrees). Therefore, of the reflected light from the reflecting member 5,
When the light enters the curved surface portion 1e or the flat surface portion 1f, the light incident at an angle larger than θ _c is totally reflected by these surfaces and is not reabsorbed by the light source 2.

If a material having a larger refractive index is used as the material of the light guide plate, the critical angle becomes smaller,
More light can be transmitted toward the reflecting member 4 side.

Therefore, in the back lighting device of the second embodiment, as compared with the conventional device, more of the light emitted from the light source 2 is guided to the reflecting member 3 side, so that the light utilization efficiency is improved. The brightness of the light emitting surface 1b is improved. Further, even if a light source having a smaller amount of light than the conventional one is used, the same brightness value as the conventional one can be obtained, and power saving can be realized.

Embodiment 3 In the back lighting device according to the third embodiment, a substance having a refractive index higher than that of air and lower than that of the light guide plate 1 is provided inside the lamp house 1d.
It is characterized by being filled inside. In the third embodiment, matching grease is used as the substance that satisfies the above conditions. FIG. 5 is a diagram for explaining an example of the back lighting device according to the third embodiment, and is a diagram showing a cross section on a light emitting surface. In FIG. 5, 9 is a matching grease filled in the lamp house 1d. The matching grease 9 has a refractive index higher than that of air and equal to or lower than that of the light guide plate 1. By filling the matching grease 9 in the lamp house 1d, it is possible to suppress the light emitted from the light source 2 from being reflected by the light introducing section 1a, and to guide more light from the light introducing section 1a. Become. Further, if the matching grease 9 has the same refractive index as that of the light guide plate 1, it is possible to eliminate reflection at the light introducing portion 1a.

As described above, by filling the lamp house 1d with a substance having a refractive index higher than that of air and lower than that of the light guide plate 1, the amount of light reflected by the light introducing portion 1a can be reduced. Since more light can be guided from the light introducing portion 1a to the reflecting member 3 side than in the conventional case, the brightness of the light emitting surface 1b is increased. Further, when obtaining the same brightness as that of the conventional device, in the back lighting device of the third embodiment, the brightness of the light source 2 can be suppressed to be lower than that of the conventional device, so that it is possible to save power.

Embodiment 4 FIG. In the back lighting device of the third embodiment, the inside of the lamp house 1d is filled with a substance whose refractive index is larger than that of air and smaller than that of the light guide plate 1. In the configuration as described above, the light emitted from the light source 2 toward the curved surface portion 1c is reflected inside the light guide plate 1 by the reflecting member 5, but the reflected light is curved surface portion 1e.
When the inside of the lamp house 1d is originally air, the reflected light enters the lamp house 1d due to the matching grease 9 with which the lamp house 1d is filled, and is emitted toward the curved surface portion 1c side. There arises a problem that the efficiency of utilizing the emitted light is reduced. Embodiment 4
The back lighting device of is made in order to solve the above-described problem, and in the lamp house 1d, the space near the light introducing portion has a refractive index larger than that of air and less than or equal to that of the light guide plate 1. It is characterized by being filled with the substance.
The back lighting device of the fourth embodiment uses matching grease as an example of the substance.

FIG. 6 is a view for explaining the back lighting device of the fourth embodiment and is a cross-sectional view perpendicular to the light emitting surface.
In FIG. 6, 9 is a matching grease, and the matching grease 9 fills the space on the light introducing portion 1a side in the lamp house 1d of the lamp house, and the space on the reflecting member 5 side is an air layer.

In the back lighting device of the fourth embodiment, the light emitted from the light source 2 to the light emitting surface 1b side of the light guide plate 1 is not reflected at the lamp house 1d and the light introduction part 1a of the light guide plate 1 and is not entirely guided by the light guide plate. Introduced in 1. Further, among the light emitted from the light source 2, the light emitted to the curved surface portion 1c side also enters the light guide plate 1 through the air layer and enters the light guide plate 1 again in the direction of the light source 2 as described in the first embodiment. A part of the light reflected to the inside of the light guide plate 1 is repeatedly reflected at the boundary between the light guide plate 1 and the lamp house 1d so that the inside of the light guide plate 1 emits light.
The light utilization efficiency is improved and the brightness on the light emitting surface 1b is increased as compared with the conventional device. Alternatively, when the same brightness as that of the conventional device is obtained, the brightness of the light source can be suppressed to be lower than that of the conventional device, so that power saving can be achieved.

Embodiment 5 FIG. Of the light emitted from the light source 2, part of the light emitted to the curved surface portion 1c side is repeatedly reflected and then transmitted to the light emitting surface 1b side, but the rest of the light is absorbed by the light source 2 again. The back lighting device of the fifth embodiment is designed to suppress the amount of light absorbed by the light source 2, and is characterized in that a light diffusing section is provided around the lamp house 1d.

FIG. 7 is a diagram for explaining an example of the back lighting device of the fifth embodiment, and is a cross-sectional view perpendicular to the light emitting surface. In FIG. 7, reference numeral 8 is a light diffusion portion. Light diffusing unit 8
Is attached to, for example, the boundary surface of the lamp house 1d and around the curved surface portion 1e, and has a function of reflecting the light traveling from the reflecting member 5 to the curved surface portion 1e into the light guide plate 1 again.

In the back lighting device configured as shown in FIG. 7, since the light diffusing section 8 is provided on the boundary surface of the lamp house 1d in which the light source 2 is installed, the light is emitted from the light source 2 toward the reflecting member 5, Of the light reflected by the reflecting member 5 and returned to the direction of the light source 2, the light incident on the light diffusing section 8 is reflected by the light diffusing section 8 regardless of the incident angle, and the light is emitted inside the light guide plate 1. Since the light is reflected toward the inside of the light guide plate 1 below 1b, this light can be transmitted toward the reflector 4 side. The light utilization efficiency is improved and the brightness on the light emitting surface 1b is increased as compared with the conventional device. Alternatively, when the same brightness as that of the conventional device is obtained, the brightness of the light source can be suppressed to be lower than that of the conventional device, so that power saving can be achieved.

By attaching the light diffusing portion 8 to the portion where the light is easily reabsorbed by the light source 2, the above-mentioned effect can be further enhanced.

Further, as shown in FIG. 8, by providing the light diffusing section 8 in the back lighting device of the third and fourth embodiments,
The light reflected from the reflection member 5 can be prevented from being reabsorbed by the light source 2.

Sixth Embodiment In the back lighting device of the above-described embodiments, the lamp house is formed near the side end of the light guide plate, so that the light source is located near the end of the light guide plate. The back lighting device of the sixth embodiment is characterized in that the lamp house is formed near the center of the light guide plate and the light source is arranged at the center of the light guide plate or on the lower surface near the center.

FIG. 9 is a view for explaining a back lighting device which is an example of the sixth embodiment, and shows a cross section perpendicular to the light emitting surface. Reference numeral 1d denotes a lamp house, the cross section of which has a shape into which the light source 2 can be inserted. In the sixth embodiment, the lamp house 1d has a circular cross section because the light source 2 has a circular cross section. The lamp house 1d is formed in the center of the light guide plate 1. Reference numeral 11 denotes a light shielding member provided on the light emitting surface 1b side of the light source 2. In the sixth embodiment, the light shielding member 11 is a film-shaped member provided to shield the light emitted from the light source 2 and emitted to the light emitting surface 1b. By providing the light blocking member 11, it is possible to suppress the light emitted from the light source 2 directly from the panel surface above the light source 2. Therefore, since the brightness value of the light emitting surface 1b located above the light source 2 is prevented from significantly increasing, it is possible to keep the brightness value of the light emitting surface 1b uniform. Therefore, the light shielding member 11 for reducing the brightness is attached above the light source 2 so as to maintain the uniformity of the brightness in the entire panel. Reference numeral 4 denotes a reflecting member attached to the end portion of the light guide plate 1, and the reflecting member 4 has a metal having a high reflectance such as silver. Further, the reflection member 4 prevents leakage of the light transmitted from the light source 2 to the reflection member 4 and reflects the light again into the light guide plate 1. The reflection member 4 may be attached to the end portion of the light guide plate 1, or a metal having a high reflectance such as silver may be directly deposited on the end portion of the light guide plate 1.

Since the back lighting device of the sixth embodiment can effectively guide the light beams emitted from both side surfaces of the light source 2 into the light guide plate 1, the light utilization efficiency is improved as compared with the conventional device.

Further, as shown in FIG. 10, as the light source 2,
Even when a rod-shaped light source having a quadrangular cross section is used, the same effect as described above can be obtained by providing the shielding member 11 to shield the light directly emitted from the rod-shaped light source 2 to the panel surface.

Further, in the sixth embodiment, the lamp house 1d
Although an example in which the cross section perpendicular to the light emitting surface 1b and the cross section of the light source 2 have the same shape has been described, the lamp house 1d may have any shape as long as the light source 2 can be inserted therein. By filling the matching grease 9 in the air layer formed between the lamp house 1d and the light source 2, it is possible to suppress reflection at the boundary surface between the lamp house 1d and the light guide plate 1.

[0045]

According to the back lighting device of the present invention, a light guide plate having a light emitting surface and a side end face formed of the first curved surface and a hole formed in the light guide plate are provided near the side end face. Is located on the side opposite to the light emitting surface and the light source to be inserted into this lamp house, and the side end surface side shape is formed by the second curved surface, and the light from the light source is directed toward the light emitting surface. Since the first reflecting member for reflecting and the second reflecting member for reflecting the light from the light source emitted from the side end face toward the inside of the light guide plate are provided, the light is emitted from the light source toward the first curved surface side. The reflected light is repeatedly reflected by the second curved surface and the second reflecting member, and is guided to the lower part of the light emitting surface, so that it is possible to transmit more light than in the past, so that the light utilization efficiency is improved. It is possible to obtain a back lighting device which is improved and has high brightness and low power consumption. Further, since the lamp house is formed inside the light guide plate, it is possible to make the device thinner than before.

In the back lighting device according to the second aspect, since the interior of the lamp house is filled with a substance having a refractive index higher than that of air and lower than that of the light guide plate, the boundary between the lamp house and the light guide plate is filled. Since the reflection on the surface can be suppressed, the light utilization efficiency is improved, and it becomes possible to obtain a back lighting device with light brightness and low power consumption.

In the back lighting device according to the third aspect, since the light diffusing portion for reflecting the light reflected by the second reflecting member is provided in a part of the periphery of the lamp house, the second reflecting member is used. Since the amount of light that enters the lamp house after being reflected is reduced, it is possible to increase the amount of light that is transmitted to the lower part of the light emitting surface, improving the light utilization efficiency, high brightness and low power consumption back lighting. The device can be obtained. .

In the back lighting device according to the fourth aspect, since the lamp house is located near the center of the light guide plate, the light from the light source can be efficiently used. Further, since the light shielding member for shielding a part of the light emitted from the light source toward the light emitting surface is provided, it is possible to make the luminance of the light emitting surface uniform. In addition, since the lamp house is formed inside the light guide plate, the device can be made thinner than before.

In the back lighting device according to the fifth aspect, since the interior of the lamp house is filled with a substance having a refractive index higher than that of air and lower than that of the light guide plate, the boundary between the lamp house and the light guide plate is filled. It is possible to suppress reflection on the surface.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an example of a back lighting device according to a first embodiment.

FIG. 2 is a diagram illustrating a light source 2 in the back lighting device according to the first embodiment.
It is a figure for demonstrating the course of the light radiate | emitted from the curved surface part 1c side.

FIG. 3 is a diagram for explaining progress of light incident from a light introducing unit 1a in the back lighting device of the first embodiment.

FIG. 4 is a diagram for explaining an example of a back lighting device according to a second embodiment and a conventional back lighting device.

FIG. 5 is a diagram for explaining an example of a back lighting device according to a third embodiment.

FIG. 6 is a diagram for explaining an example of a back lighting device according to a fourth embodiment.

FIG. 7 is a diagram for explaining an example of a back lighting device according to a fifth embodiment.

FIG. 8 is a diagram for explaining an example when the back lighting device of the fifth embodiment is applied to the back lighting device of the third and fourth embodiments.

FIG. 9 is a diagram for explaining an example of a back lighting device according to a sixth embodiment.

FIG. 10 is a diagram for explaining another example of the back lighting device according to the sixth embodiment.

FIG. 11 is a diagram for explaining a conventional back lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide plate 1a Light introduction part 1b Light emitting surface 1c Curved part 1d Lamp house 1e Curved part 1f Flat part 2 Light source 3 Reflecting member 4 Reflecting member 5 Reflecting member 6 Lens sheet 8 Light diffusing part 9 Matching grease 10 Reflecting member

Continued on the front page (72) Inventor Masaaki Tanaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (5)

[Claims] 1. A light guide plate having a light emitting surface and a side end face formed of a first curved surface, and a hole formed in the light guide plate, which is located near the side end face and has a shape on the side end face side. A lamp house formed by a second curved surface, a light source to be inserted into the lamp house, and a first reflection that is located on a surface facing the light emitting surface and reflects light from the light source toward the light emitting surface. A back lighting device comprising: a member; and a second reflecting member that reflects light from the light source emitted from the side end surface toward the inside of the light guide plate. 2. The back lighting device according to claim 1, wherein the inside of the lamp house is filled with a substance having a refractive index higher than that of air and lower than that of the light guide plate. 3. The back lighting according to claim 1, further comprising a light diffusing section that reflects the light reflected by the second reflecting member in a part of the periphery of the lamp house. apparatus. 4. A light guide plate having a light emitting surface, a lamp house formed in the light guide plate near the center of the light guide plate, a light source to be inserted into the lamp house, and a light source from the light source. A light shielding member that shields a part of the light emitted toward the light emitting surface, and a reflecting member that is located on a surface facing the light emitting surface and that reflects light from the light source toward the light emitting surface are provided. A back lighting device characterized by the above. 5. The back lighting device according to claim 4, wherein the inside of the lamp house is filled with a substance having a refractive index higher than that of air and lower than that of the light guide plate.