JPH039306A - Backlight device - Google Patents

Abstract

PURPOSE:To make a device thin and light in weight and to obtain the device excellent in the uniformity of brightness even when large area is accomplished by disposing a light source on the side surface of a transparent substrate, forming a light irregular reflection layer in a pattern where density gets high in accordance with a distance from the light source and a light diffusion layer on the light irregular reflection layer on the surface of the transpar ent substrate and forming a light mirror surface reflection layer on the back surface of the transparent substrate. CONSTITUTION:The light source 2 is disposed on at least one of four sides of the transparent substrate 1, the light irregular reflection layer 3 is formed in the pattern where the density gets high in accordance with the distance from the light source 2 on the light emitting surface of the surface of the substrate 1 and the light mirror surface reflecotin layer 4 is formed on the back surface of the substrate 1, then the light diffusion layer 5 is provided on the light irregular reflection layer 3. Therefore, the quantity of light radiated from the surface of the substrate 1 is made uniform all over the surface. The light radiated from the surface of the substrate 1 is diffused by the light diffusion layer 5, so that the unevenness of brightness is prevented from occurring between the light irregular reflection layer 3 and a spot other than the pattern where the light irregular reflection layer 3 is not formed. Thus, the device is made thin and light in weight and the excellent uniformity of brightness is obtained in the device even when the large area is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a backlight device that is disposed on the back side of a liquid crystal display (LCD) and illuminates the liquid crystal display.

"Prior Art" In recent years, liquid crystal displays have excellent characteristics such as being thin, lightweight, and low power consumption, and there are great expectations for their use in various products as flat displays that can fully demonstrate these characteristics. It is being However, liquid crystal displays are based on C, which is currently widely used for industrial and consumer purposes.
It is inferior in image quality compared to RT (Cathode RayTube), and a backlight type liquid crystal display has been developed to improve this image quality.

This type of backlight device is desired to be thin and lightweight, and is also required to have uniform brightness over the entire screen area. Various proposals have already been made as techniques for improving the uniformity of brightness in backlight devices. For example, in the device described in JP-A-57-13478, a milky white light scattering body is provided above a linear light source, and the layer thickness is thick at the center of the milky white light scattering body, and becomes thinner toward the ends. This eliminates uneven illumination and allows for a thinner and more compact design. Furthermore, in the one described in JP-A No. 60-264039,
Using a serpentine cold cathode lamp, JP-A-61-21998
The method described in Japanese Patent Application Laid-Open No. 1988-1 utilizes an ultraviolet lamp and a phosphor coating layer disposed around the ultraviolet lamp.

In the device described in JP-A No. 621, a light source is incorporated into the light guide plate, and in the device described in JP-A-62-127717,
Concave and convex lenses are arranged on the upper and lower surfaces of multiple light sources, and
The one described in 3-1.25975 uses a U-shaped lamp, and the one described in JP-A-54105562 uses a light scattering reflector in a transparent substrate with a low concentration on the light source side. Put it in such a way that it becomes more concentrated as it gets farther away.
This is intended to eliminate uneven irradiation and make brightness uniform.

"Problem to be Solved by the Invention" U2 However, the above conventional method has the following problems.

(1) When a light source is disposed on the lower surface of the light scattering body, there is a problem that the entire backlight device becomes thick and expensive.

(2) When a plurality of lamps are provided in order to make the brightness uniform, there is a problem that the larger the area, the more lamps are required, leading to higher costs.

(3) When a serpentine lamp is used, there is a problem in that it is not suitable for mass production when applied to a large area.

(4) When a light scattering body is placed in a transparent substrate, there is a problem in that it is difficult to manufacture the light scattering material with good reproducibility to ensure uniform brightness.

Therefore, the present invention has been made to overcome the problems described in 1-4.・The 2-crite device is a rod (both called U).

"Means for Solving the Problem" The present invention has been made to achieve the above-mentioned Old Testament, and in claim (1), a light source is disposed at at least one place on the back of the four circumferences of the transparent substrate j2, and A light-diffusing reflective layer is formed on the light output surface of the front surface in a pattern that increases in density depending on the distance from the light source, and a light specular reflective layer is formed on the back surface of the transparent substrate.
"And": The backlight device is characterized by having a light diffusing layer provided on the light scattering and reflecting layer. Item 1(2) is characterized by a backlight device in which a light-diffusing reflection layer is formed between the back surface of the transparent substrate and the light specular reflection layer in a pattern that increases in density according to the distance from the light source. It is something to do.

"Function" In the above configuration, the present invention provides that in claim (1), the emitted light from the light source enters the inside from the end face of the transparent substrate, and the optical density difference at the interface between the transparent substrate and the air and the light The light travels through the transparent substrate while being repeatedly reflected due to the presence of the specular reflective layer. During this process, when the light scattering layer on the surface of the transparent substrate is reached,
The light diffuse reflection layer causes diffuse reflection. In areas other than the pattern of the light-diffusing reflection layer on the surface of the transparent substrate, part of the light is reflected and the other part of the light is transmitted. The light diffusely reflected by the above-mentioned diffusely reflecting layer is reflected by the specular reflective layer on the back side of the transparent substrate, reaches the surface of the transparent substrate, and becomes below the critical angle. Since the pattern of the light scattering reflection layer is formed to increase in density according to the distance from the light source, the amount of light emitted from the surface of the transparent substrate is made uniform over the entire surface. The light emitted from the surface of the transparent substrate is diffused by the light diffusing layer, thereby preventing the occurrence of uneven graininess between the light-diffusing reflection layer and a portion other than the pattern where the light-diffusing reflection layer is not formed.

In claim (2), a light-diffusing reflection layer is also formed between the back surface of the transparent substrate and the light specular reflection layer in a pattern that increases in density according to the distance from the light source (21, the light-diffusing reflection layer also has a pattern that increases the density within the transparent substrate). The system diffusely reflects the light introduced into the system, thereby increasing the efficiency of light utilization.

"Example" Below, a hack-cry! according to the present invention will be described. - An embodiment of the device will be described based on FIG. 1i. 1 and 2 show a first embodiment, and numeral 1 in the figures represents a transparent substrate. The transparent substrate 1 is
The thin plate with good light transmittance is made of a transparent plate made of a transparent material or synthetic resin, such as a glass plate, an acrylic resin plate, a polycarbonate resin plate, etc., for example. A light source 2 is disposed on one side of the four circumferences of the transparent substrate 1. On the surface of the transparent substrate 1, a light scattering reflection layer 3 for diffusely reflecting the light emitted from the light source is drawn in a pattern whose density increases in proportion to the distance from the light source 2.

Light scattering reflection N3 uses a volatile curing type or ultraviolet curing type white ink containing white pigments such as titanium oxide and zinc oxide as reflective particles, or colored ink in a color according to the wishes of the user. use. As a method of forming the light scattering reflection N3 on the surface of the transparent substrate 1, known technical means such as screen printing and the Scumbu method are used. When forming the light scattering reflection layer 3 on the surface of the transparent substrate 1, as shown in FIG. 2, the number of dots per unit area is the same, and the diameter of the dots increases as the distance from the light source increases. Then, the diffuse reflection N per unit area of the transparent substrate 1
The occupancy rate of 3 is to be changed. The diameter of the points of the light scattering reflection layer 3 is 1 to 3000μ, preferably 10 to 1000μ.
Set to μ.

On the other hand, a light specular reflection layer N4 is laminated on the entire back surface of the transparent substrate 1. The optical specular reflection layer 4 is made to have a mirror surface with high reflectance.For example, metal such as silver or aluminum may be deposited by vapor deposition or sputtering, or a film with high reflectance such as a polyester film with aluminum vapor deposited may be used. It can also be attached or pasted. Further, in order to prevent the optical specular reflection layer 4 from deteriorating over time, it is also possible to apply a moisture-proof coating to the optical specular reflection layer 4 or to attach a moisture-proof film to the optical specular reflection layer 4. On the light scattering reflection layer 3 of the transparent substrate l, there is a light diffusion layer N5.
will be established. For the light diffusion layer 5, so-called frosted glass or a plastic film with a roughened surface is used, and a polyester film having a light diffusion layer with a roughened surface is preferable from the viewpoint of cost and durability. Furthermore, the light source 2 is a cold cathode tube with a narrow tube diameter, in addition to the generally widely used fluorescent lamp, which reduces the thickness of the entire backlight device and suppresses the influence of temperature on the liquid crystal display (LCD) panel. It is advantageous for use.

Further, as the light source 2, an aperture type lamp may be used. A housing 6 surrounds the light source 2 and a portion other than the light-emitting surface side of the transparent substrate 1 on which the light-diffusing reflection N3 and the light specular reflection layer 4 are formed and the light-diffusing reflection layer 5 is attached to the surface. The housing 6 is made of metal or resin with a high light reflectance treatment on its inner surface, and has the function of returning light leaked from the transparent substrate 1 and light source 2 into the transparent substrate 1, and preventing light from coming from other than the light emitting surface. It has a function of preventing light leakage and a function of dissipating heat generated from the light source 2.

In order to effectively perform such functions, the housing 6
An aluminum case whose inner surface is coated with a white paint with high light reflectance or an aluminum case which has been subjected to vapor deposition treatment with high reflection efficiency is suitable.

It is also useful to cover the periphery of the transparent substrate 1 other than the light source 2 side with a reflective tape 7 or the like to prevent light from leaking from the periphery.

In the first embodiment, when the emitted light from the light source 2 enters the inside of the transparent substrate 1 from the end surface, it is reflected depending on the large optical angle due to the optical density difference at the interface between the surface of the transparent substrate and the air. The light travels through the transparent substrate 1 while being sequentially subjected to specular reflection by the light specular reflection layer 4. When the light reaches the light-diffusing reflection layer 3 in the middle of this progress, it is diffusely reflected by the reflective particles in the light-diffusing reflection layer 3, and this diffusely reflected light is once specularly reflected on the light specular reflection layer 4, but it does not reach the surface of the transparent substrate 1. becomes less than the critical angle, and a part of the diffusely reflected light is radiated to the outside from gaps other than the pattern of the diffusely reflected layer 3. Since the light scattering reflection layer 3 is drawn in a pattern that becomes denser as the distance from the light source 2 increases, this emitted light has uniform brightness over the entire light emitting surface of the surface of the transparent substrate 1. Become. In other words,
Emitted light with uniform brightness can be obtained not only in the vicinity of the light source 2, but also in the farthest position from the light source 2, and even in intermediate positions. The emitted light enters the light diffusion N5 and is diffused, and then enters the LCD panel,
The light diffusing layer 5 eliminates a change in the amount of light that occurs between the light-diffusing reflection layer 3 and an area other than the pattern of the light-diffuse reflection N3, that is, "occurrence of shadows" due to the presence of the light-diffuse reflection N3, and obtains illumination light without uneven brightness.

3 and 4 show a second embodiment, in which light sources 2a and 2b are provided on both the left and right sides of a transparent substrate 1. On the other hand, light scattering reflective layers 8a and 8b are formed on both the front and back surfaces of the transparent substrate 1. The light scattering reflection FIR3°8b is formed by screen printing or Nukumbu printing using white ink or colored ink containing reflective fine particles such as titanium oxide, as in the first embodiment. As shown, only the number of points is changed by the light source 23. without changing the diameter of the points.
21) is depicted in a pattern that increases in proportion to the distance from In other words, the light scattering reflection layers 8a and 8b are the light sources 2a and 2b.
The pattern is formed such that the density is highest at the center of the transparent substrate 1, which is farthest from the light sources 2a and 2b, and the density becomes lower as it approaches the light sources 2a and 2b. A light scattering reflection layer 8 is provided on the entire back surface of the transparent substrate 1.
A light specular reflection layer 4 is formed by overlaying the layer a. The optical specular reflection layer 4 is formed of the same material and by the same method as in the first embodiment. A light diffusing layer 5 as in the first embodiment is provided in the light emitting region of the surface of the transparent substrate 1. Moreover, the light sources 2a, 2
b is surrounded by a lamp housing 9 whose inner surface is treated to have high reflectance. The lamp housing 9 reflects the emitted light from the light sources 2a and 2b and radiates heat, and is made of a material with a high reflectance, such as the Hau::2 ring 5(7) of the first embodiment. suitable.

In this embodiment, the emitted light from the light sources 2a and 2b enters the interior from both ends of the transparent substrate 1, and there is an optical density difference 1 at the interface between the surface of the transparent substrate 1 and the air, and a light specular reflection layer 4. As a result, the light travels through the transparent substrate 1 while being reflected 17 times. During this process, the light scattering reflection layer 8 on the back side of the transparent substrate 1
The light that has reached point a becomes less than or equal to the pn boundary angle with respect to the surface of the transparent substrate 1, and is radiated to the outside through the interval between the light scattering and reflection layers 81). After reaching the light scattering reflection layer Bbt, specular reflection is applied to the light specular reflection layer 4 as in the first embodiment.
, and later reflected to the outside through gaps other than the pattern of the New Year's Day 1 reflective layer 8b. The light emitted from the transparent substrate 1 is diffused by the light diffusion layer 5 as in the first embodiment, and the light is emitted to the LCD.
In the second embodiment, diffused reflection N8 is provided to the panel on both the front and back surfaces of the transparent substrate 1.
a, 8b and 7, the brightness can be made more uniform compared to the first example h1), and since two light sources 2a and 2b are used, the absolute brightness can be improved. It is something that can increase its value. Moreover, if the light-diffusing reflection layers 8a, 8b are provided on both sides of the transparent substrate 1, each of the light-diffusing reflection layers 8a, 8
The pattern density of b can be kept low compared to the light scattering reflection layer 3 on only one side of the first embodiment, and if kept low, the reproducibility during printing is further improved than that of a high-density pattern7, for example when screen printing. Inconveniences such as contact between points due to so-called "sag" can be prevented, and yield can be improved.

1. In the present invention, the light scattering reflection layer 3.8a.

8b, in addition to the first and second embodiments, there are methods of changing the diameter of the points and the number of points per unit area,
It is also possible to adopt a format in which lines are used to change the thickness of the cotton and the spacing between the cotton.

“Effect of the invention J As described above, according to the backlight device according to the present invention,
Since the light source is arranged not in the thickness direction of the transparent substrate but on the peripheral edge side, the total thickness of the backlight device depends on the thickness of the transparent substrate including the diameter of the light source, the light diffusion layer, the light scattering reflection layer, etc. When attaching this to the housing C4n, there is only a slight amount of clearance, space, and the total thickness of other necessary components such as the housing, and the uniformity of brightness is excellent.
Therefore, it is possible to achieve a thin and lightweight design that was difficult to achieve with conventional technology, and even with a larger area, it is possible to obtain excellent brightness uniformity and property. Since this is formed, it is possible to prevent light from leaking to the rear surface side, and the present invention can provide an ihac light device with high light utilization efficiency. The backlight 1-device of the present invention as described above is a liquid crystal j! Should I install it behind the display (LCD)? Secondly, it is possible to create a thin and easy-to-read screen with no uneven brightness, which greatly contributes to improving the functionality of LCD discs (1°CD) and is useful for various other backlight devices. 7 can also be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the bank light device according to the present invention, and FIG. FIG. 3 is a configuration diagram of a backlight device of the second embodiment, and FIG. 4 is an explanatory diagram of main parts showing a depiction form of the light-scattering reflective layer of FIG. 3. 1...Transparent substrate 2.2a, 2b...Light source 3.8a, 8b...Light scattering reflection layer 4...Light specular reflection layer 5...Light diffusion layer FIG.

Claims (2)

[Claims] (1) A light source is disposed in at least one of the four circumferences of the transparent substrate, and a light-diffusing reflective layer is formed on the light exit surface of the transparent substrate in a pattern that increases in density depending on the distance from the light source, making the transparent substrate transparent. 1. A backlight device comprising: a mirror reflective layer formed on the back surface of a substrate; and a light diffusing layer provided on the diffuse reflective layer. (2) A light scattering reflection layer is formed between the back surface of the transparent substrate and the light specular reflection layer in a pattern that becomes denser depending on the distance from the light source. Backlight device.