JP2004117435A - Backlight structure for liquid crystal display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight structure for a liquid crystal display panel with which the liquid crystal display panel is brightly illuminated by guiding light emitted from a light source such as an LED in a light transmission plate without light leakage and, at the same time, breakage and displacement caused by contact between the light transmission plate and the light source are prevented from occurring even when being subjected to vibration, shock and the like. <P>SOLUTION: The backlight structure comprises the LED 27 disposed between a circuit substrate 26 and the light transmission plate 28 and illuminates the liquid crystal display panel 22 by making light emitted from a light emitting surface 32 of the LED 27 incident on a light receiving surface 34 of the light transmission plate 28. The LED 27 is mounted on the circuit substrate 26 via an elastic member 30, and at the same time, the light emitting surface 32 of the LED 27 is tightly stuck to the light receiving surface 34 of the light transmission plate 28. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backlight structure that illuminates a liquid crystal display panel surface with light guided from one end of a light guide plate.
[0002]
[Prior art]
In recent years, display devices using liquid crystal cells are mounted on various electronic devices such as watches, telephones, and personal computers. In such an electronic device, in particular, a watch, a mobile phone, and the like are used even at night or in a dark place, and therefore, are often provided with a backlight device that illuminates the liquid crystal cell.
[0003]
FIG. 4 shows a cross-sectional structure of a liquid crystal display device 1 provided with a conventional backlight device 3. In the liquid crystal display device 1, the backlight device 3 is disposed below a frame body 4, and the liquid crystal display panel 2 is disposed thereon. The liquid crystal display panel 2 includes a liquid crystal cell having a structure in which a liquid crystal material is sandwiched between two glass substrates on which a transparent electrode film is formed, and two polarizing plates disposed on the upper and lower surfaces of the liquid crystal cell. It consists of and. The backlight device 3 includes a light emitting element (LED 7) that is a light source and a light guide plate 8 that guides light emitted from the LED 7. The light guide plate 8 is formed of a transparent acrylic material, and is integrally formed of a light guide main body portion 8a having substantially the same area as the liquid crystal display panel 2 and a light receiving portion 8b protruding from one end thereof. The light receiving portion 8b includes a light receiving surface 9 projecting in parallel from the lower surface of the light guide main body portion 8a, and a reflecting surface 10 having an inclination angle of about 45 degrees from the upper surface of the light guide main body portion 8a. The LED 7 is mounted on the tip of the circuit board 6 on which various ICs and electronic components are mounted, and is fixed with the light emitting surface 13 facing the light receiving surface 9.
[0004]
As shown in FIG. 5, the light emitted from the light emitting surface 13 of the LED 7 is incident on the light receiving surface 9, reflected by the reflecting surface 10 formed to be inclined at a predetermined angle, and guided into the light guide main body 8a. Lighted. The light reflected by the reflecting surface 10 has a small incident angle at the portion a closest to the LED 7, so that the portion near the LED 7 side of the light guide plate 8 is illuminated, and the light reflected by the portion b with a large incident angle is more than that. Even irradiate far away. In this way, the light received and reflected is guided to the entire light guide plate 8 to illuminate the liquid crystal display panel 2 disposed above from the back. A light reflecting sheet 11 is provided on the lower surface of the light guide plate 8, and a light diffusion sheet 12 is provided on the upper surface. The light reflecting sheet 11 reflects the light guided into the light guide plate 8 upward to increase the brightness, and the light diffusion sheet 12 moderately emits light emitted from the surface of the lower light guide plate 8. It works to suppress uneven brightness by diffusing.
[0005]
[Problems to be solved by the invention]
By the way, when it is intended to reduce the size of the backlight device 3 while ensuring a wide view area of the liquid crystal display panel 2, the light from the LED 7 is transmitted to the liquid crystal display panel 2 as in the conventional liquid crystal display device 1 described above. Therefore, it is necessary to take a configuration in which light is guided into the light guide main body portion 8a by the light receiving portion 8b protruding from the light guide. In the backlight device 3 having such a configuration, in order to effectively guide light into the light guide main body portion 8a, it is necessary to increase the amount of light taken into the light receiving portion 8b as much as possible. Ideally, the light-receiving surface 9 of the light-receiving unit 8b and the light-emitting surface 13 of the LED 7 are in close contact with each other without any gap. However, if the light receiving surface 9 and the light emitting surface 13 are kept in close contact with each other, a strong pressing force may be applied due to vibration or impact, and the light receiving surface 9 or the light emitting surface 13 may be damaged. In addition, the vibration or impact may be applied continuously for a long time, or the gap between the light receiving surface 9 and the light emitting surface 13 may gradually increase depending on the usage environment and usage conditions over a long period of time. Such factors may accumulate and cause a decrease in light receiving efficiency and light guiding efficiency.
[0006]
Because of such a problem, a certain gap must be provided between the light receiving surface 9 and the light emitting surface 13 in consideration of durability, safety, etc., even if the light receiving efficiency is somewhat sacrificed. Moreover, in order to provide the said fixed clearance gap, there exists a problem that positioning of the circuit board 6 in which LED7 is mounted, and the light-guide plate 8 must be managed strictly.
[0007]
Therefore, an object of the present invention is to guide light emitted from a light source such as an LED into the light guide plate without omission to illuminate the liquid crystal display panel brightly, and even when vibration or impact is applied, the light guide plate and the light source It is intended to provide a backlight structure of a liquid crystal display panel that can prevent the occurrence of breakage and displacement due to contact with the liquid crystal display.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, a backlight structure of a liquid crystal display panel according to claim 1 of the present invention is configured such that a light emitting element is disposed between a circuit board and a light guide plate and is irradiated from a light emitting surface of the light emitting element. A backlight structure that illuminates a liquid crystal display panel by causing light to enter the light receiving surface of the light guide plate, wherein the light emitting element is mounted on the circuit board via an elastic member, and the light emitting surface of the light emitting element is guided to the light guide. It is characterized by being in close contact with the light receiving surface of the optical plate.
[0009]
According to the present invention, when the light emitting surface of the light emitting element is disposed facing the light receiving surface of the light guide plate, the light emitting element is mounted on the circuit board via the elastic member. Due to the force, the light emitting surface of the light emitting element and the light receiving surface of the light guide plate are always in close contact. For this reason, the light emitted from the light emitting element can be incident on the light receiving surface of the light guide plate without leaking to the surroundings, and the entire light guide plate can be illuminated. Since the light emitting element and the light receiving surface of the light guide plate are sandwiched by an appropriate elastic force of an elastic member, even when vibration or impact is applied, the light is absorbed by the elastic member, and the effect of preventing breakage and displacement is obtained. is there. Further, unlike the prior art, it is not necessary to perform an adjustment operation required for precise positioning so as to maintain a gap between the light guide plate and the light emitting element at a constant interval.
[0010]
Further, by forming an electrode pattern corresponding to the electrode of the light emitting element on the surface of the elastic member, electrical connection with the circuit board can be easily achieved. The light emitting element can be directly mounted on the elastic member on which the electrode pattern is formed, but can also be mounted on the elastic member via an electrode substrate.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a backlight structure of a liquid crystal display panel according to the present invention will be described in detail with reference to the accompanying drawings.
[0012]
FIG. 1 shows a configuration example of a liquid crystal display device 21 having a backlight structure of the present invention. The liquid crystal display device 21 has a structure in which a liquid crystal display panel 22 is stacked above a backlight device 23. The backlight device 23 includes a light guide plate 28, a light emitting element (LED 27) that irradiates light into the light guide plate 28, and a circuit board 26 on which the LED 27 is mounted, and is fixed on the circuit board 26. The LED 27 is contacted and fixed to the lower surface of the light guide plate 28 through an elastic member 30.
[0013]
The light guide plate 28 is formed of a transparent acrylic plate, and has a light guide body portion 28a having substantially the same area as the liquid crystal display panel 22 and a constant thickness, and a light receiving portion 28b provided protruding from the light guide body portion 28a. It is integrally formed with. The light receiving unit 28b includes a light receiving surface 34 that receives light emitted from the LED 27, and a reflective surface 35 that reflects the received light toward the light guide main body 28a. The reflection surface 35 is formed at a predetermined inclination angle in order to guide light to the end of the light guide main body 28a.
[0014]
In the light guide body 28a, an upper diffusion member 36 is disposed on the upper surface, and a reflection member 38 is disposed on the lower surface. The upper diffusing member 36 is formed by forming fine irregularities on the surface of a transparent polyester film having a thickness of about 100 μm. The uneven portion is formed by coating various kinds of beads. The reflection member 38 is a sheet-like member in which silver (Ag), aluminum (Al), or the like having a high reflectance is vapor-deposited, and the light guided into the light guide main body 28a is effectively liquid crystal display panel. It is provided for reflection toward 22.
[0015]
The LED 27 is formed by mounting a light emitting element by die bonding or wire bonding on a substrate on which electrodes are formed, and sealing the periphery thereof with a transparent resin material. The sealed upper surface is a light emitting surface 32, and is formed in a convex lens shape for collecting and emitting light.
[0016]
One end of the circuit board 26 is an installation space in which the LEDs 27 are disposed, and the lower surface of the elastic member 30 is positioned and fixed on the installation space. On the other hand, a small electrode substrate 29 on which an electrode pattern corresponding to the LED 27 is formed is fixed on the upper surface of the elastic member 30, and the LED 27 is mounted on the electrode substrate 29. The elastic member 30 has an elastic force such that when the electrode substrate 29 and the LED 27 are placed and sandwiched between the light receiving surface 34 and the circuit board 26, the light receiving surface 34 and the light emitting surface 32 of the LED 27 are in close contact with each other. And a thickness.
[0017]
Next, the details of the LED 27 mounting form are shown in FIG. As described above, in this mounting form, the electrode surface of the LED 27 is mounted on the electrode substrate 29 and mounted on a predetermined mounting region on the circuit board 26 via the elastic member 30 fixed below the electrode substrate 29. To do. The elastic member 30 is formed of a non-conductive resin material having a predetermined elastic force, such as urethane rubber or silicone rubber, and a non-conductive adhesive or adhesive tape is applied to the electrode substrate 29 and the circuit substrate 26. Are joined through. The LED 27 is provided with an element electrode on the lower surface, and an electrode pattern corresponding to the element electrode is formed on an electrode substrate 29 on which the LED 27 is mounted. Electrical conduction between the electrode substrate 29 and the circuit board 26 is performed via a lead wire 31 provided along the elastic member 30, and an electrode pattern extending from a power supply circuit and a control circuit (not shown) mounted on the circuit board 26. The LED 27 is connected to supply current, and ON / OFF control is performed.
[0018]
FIG. 3 shows a configuration example in which an elastic member 40 having an electrode pattern 41 formed on the side surface is used instead of the non-conductive elastic member 30. The elastic member 40 is a pressure contact type connector made of silicone rubber, and is sandwiched between the electrode substrate 29 and the circuit substrate 26 so that the LED 27 and the circuit substrate 26 are electrically connected.
[0019]
A resin material such as urethane rubber is used for the elastic members 30 and 40, but an elastic metal member such as a coil spring may be used in addition to such a resin material. When such an elastic metal member is used, an insulating member is sandwiched between the electrode substrate 29 and the circuit substrate 26, and the electrode portion of the LED 27 formed on the electrode substrate 29 through an insulation-coated lead wire. And the electrode pattern formed on the circuit board 26 are bonded together.
[0020]
In the backlight device 23 having the above structure, the light guide plate 28 in which the upper diffusing member 36 and the reflecting member 38 are mounted on the frame 24 and the circuit board 26 on which the LED 27 is mounted are parallel to each other, and the light emitting surface 32 of the LED 27 is received. It is incorporated into the frame 24 in a state of being in close contact with the light receiving surface 34 of the portion 28b. In addition to the LEDs 27, an IC and electronic components for driving and controlling the liquid crystal display panel 22 are mounted on the circuit board 26. In addition, a white paint is applied to the inner wall of the frame 24 in which the backlight device 23 and the liquid crystal display panel 22 are incorporated, or the frame 24 itself is molded with a resin material mixed with a white pigment or dye. Thus, the light emitted from the LED 27 can be received and reflected without leaking to the outside, and the light guide efficiency to the light guide main body 28a can be increased. Further, it is also effective to provide a reflection sheet having a high reflectance such as silver (Ag) or aluminum (Al) vapor deposition sheet between the light guide plate 28 and the frame body 24.
[0021]
As is well known, the liquid crystal display panel 22 is provided with an upper transparent electrode, a lower transparent electrode, an upper alignment film, and a lower alignment film on the inner side of an upper glass substrate and a lower glass substrate that are disposed relative to each other. In this structure, the liquid crystal material is sealed in a certain interval. The liquid crystal display panel 22 is disposed above the backlight device 23 with the lower glass substrate side down.
[0022]
In the liquid crystal display device 21 having the backlight structure configured as described above, since the light emitting surface 32 of the LED 27 is always in close contact with the light receiving surface 34 of the light guide plate 28 without any gap, the light emitted by the LED 27 is The light amount can be directly taken into the light receiving portion 28b from the light receiving surface 34 without being reduced, and can be propagated into the light guide main body 28a while being reflected by the reflecting surface 35. As a result, the brightness was increased by about 20% compared to the conventional backlight device having a certain gap between the light receiving surface and the light emitting surface.
[0023]
【The invention's effect】
As described above, according to the backlight structure of the liquid crystal display panel according to the present invention, the light emitting surface of the light emitting element and the light receiving surface of the light guide plate that receives light emitted from the light emitting element are in close contact with each other. Therefore, the light emitted from the light emitting element can be effectively taken into the light guide plate without leakage.
[0024]
In addition, since the light receiving surface and the light emitting surface are in close contact with each other through an elastic member, sufficient resistance to vibration and impact can be ensured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquid crystal display device having a backlight structure of the present invention.
FIG. 2 is a cross-sectional view of a main part of the backlight structure.
FIG. 3 is a cross-sectional view of an essential part of another configuration example of the backlight structure.
FIG. 4 is a cross-sectional view of a liquid crystal display device having a conventional backlight structure.
FIG. 5 is a cross-sectional view of a main part of the conventional backlight structure.
[Explanation of symbols]
21 Liquid crystal display device 22 Liquid crystal display panel 23 Backlight device 26 Circuit board 27 LED (light source)
28 Light guide plate 28a Light guide body portion 28b Light receiving portion 30, 40 Elastic member 32 Light emitting surface 34 Light receiving surface

Claims (3)

A backlight structure that illuminates a liquid crystal display panel by disposing a light emitting element between a circuit board and a light guide plate and causing light emitted from the light emitting surface of the light emitting element to enter the light receiving surface of the light guide plate,
A backlight structure for a liquid crystal display panel, wherein the light emitting element is mounted on the circuit board via an elastic member, and the light emitting surface of the light emitting element is in close contact with the light receiving surface of the light guide plate. The backlight structure of the liquid crystal display panel according to claim 1, wherein an electrode pattern is formed on the elastic member, and the light emitting element and the circuit board are electrically connected. The backlight structure of the liquid crystal display panel according to claim 1, wherein an electrode substrate is disposed between the light emitting element and the elastic member.

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