JP2006235093A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the display quality of a liquid crystal display device having a back light device using an LED light source is caused to decrease under the influence of heat to a peripheral part of an LED. <P>SOLUTION: On an LED mount part, a member for heat radiation in a heat sink shape is adjacently arranged. Even when a current flows to the LED to generate high-temperature heat in constitution like this, the member for heat radiation efficiently radiates the heat, so no influence of the heat is exerted on the LED peripheral part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-self-luminous display device such as a liquid crystal display device used in an electronic device such as a mobile phone. Specifically, the present invention relates to an improvement in display quality of a liquid crystal display device using a backlight.

A conventional liquid crystal display device has been proposed that uses an LED (light emitting diode) as a backlight light source of a liquid crystal display element. LEDs are directional in light, and in particular, in the surface mount type on a film substrate, light is extracted in the front direction, so that there is little loss of light and it is used for a planar light source type backlight light source. As a backlight device that gives illumination light to the rear surface of the liquid crystal display element, the light emitted from the light emitting surface of the LED light source is incident on the light incident surface formed on the end surface of the light guide plate and diffused inside the light guide plate There is a configuration in which light is irradiated from one surface in the thickness direction of a light guide plate toward the rear surface of a liquid crystal display panel (see, for example, Patent Document 1). Such a backlight device includes a printed circuit board on which an LED light source is mounted, an optical sheet that is disposed on one surface of the light guide plate and guides light toward the liquid crystal display panel, and is disposed on the other surface of the light guide plate. It is constituted by a reflection sheet that reflects light and guides it to the liquid crystal display panel side.
JP-A-OLE_LINK12002-75038OLE_LINK1

  In a liquid crystal display device configured with a backlight device using such an LED light source, the LED has a characteristic that it generates heat at a high temperature when a large amount of current is passed. There is a problem that it is easy to receive. That is, in the configuration of the liquid crystal display device using the backlight device configured as in the conventional patent document 1, since heat generated from the light emitting diode is transmitted to the liquid crystal driving IC arranged in the vicinity, originally, As the ambient temperature changes, it affects the temperature compensation circuit built in the liquid crystal drive IC for the purpose of changing the drive characteristics of the liquid crystal display element, and lowers display quality such as gradation inversion during gradation display. I couldn't avoid it. In addition, since a temperature change is caused in the liquid crystal material contained in the liquid crystal panel, there is a problem that a deterioration in display quality such as a decrease in contrast ratio due to a change in temperature characteristics of the liquid crystal material cannot be avoided. It was. Accordingly, an object of the present invention is to realize a liquid crystal display device including a backlight device capable of enhancing the heat dissipation effect of an LED light source while suppressing an increase in cost.

  In the present invention, a heat sink-shaped heat dissipation member is arranged adjacent to the LED mounting portion. By disposing the heat dissipation member in the LED mounting portion in this way, even if a current flows through the LED and heat is generated at a high temperature, the heat dissipation member efficiently dissipates the heat, thus affecting the periphery of the LED. Nothing will happen.

  In the liquid crystal display device of the present invention, since the heat sink-shaped heat dissipation member is disposed adjacent to the LED mounting portion, the heat generated by the light source is effectively radiated and the influence of the heat on the periphery of the light source is avoided. Thus, the temperature rise of the LED can be suppressed, the malfunction of the temperature compensation circuit built in the liquid crystal driving IC is prevented, and the display quality is improved. Further, since the heat radiation means having an extremely simple configuration is used, an increase in cost can be suppressed.

  The display device of the present invention includes a light source, a circuit board on which the light source is mounted, a light guide that emits light from the light source from the irradiation surface, and a heat dissipation provided on the circuit board on the back surface of the surface on which the light source is mounted. A member and a non-self-luminous display element illuminated with light emitted from the light guide are provided. With such a configuration, heat generated by the light source can be effectively radiated.

  Further, a semiconductor element is directly mounted on the display element, and the semiconductor element and the light source are provided on the same side of the display device. As a result, even when the size of the display device is minimized without changing the display area, heat generated by the light source can be prevented from being transmitted to the semiconductor element. Even when the semiconductor element is a liquid crystal driving IC, the temperature compensation function for the liquid crystal of the IC is not affected, so that high display quality can be maintained.

  In addition, a reflection plate that reflects light toward the display element is provided on the back side of the light guide, and the heat dissipation member is also bonded and fixed to the reflection plate.

  Furthermore, even when a liquid crystal display element whose optical characteristics change with temperature is used as the display element, heat from the light source is not transmitted, so that high display quality can be maintained.

  Further, a film substrate is used as the circuit board. Thereby, the heat generated by the light source is efficiently transmitted to the heat radiating member, and the influence of heat can be further suppressed.

  The configuration of the liquid crystal display device of this example is schematically shown in FIG. As shown in the figure, this liquid crystal display device includes a liquid crystal display element in which a liquid crystal driving IC 2 is mounted on a liquid crystal panel 1 and a backlight device. The backlight device includes an LED 6 mounted on a film substrate 7 as a light source, and a light guide 4 for irradiating the liquid crystal display element with light from the LED 6. An optical film 3 and a reflection sheet 5 are disposed on the upper surface of the light guide 4, and a heat sink-like heat dissipation member 8 is disposed on the film substrate 7. Here, the light guide plate 4 is produced by injection molding a transparent resin such as acrylic or polycarbonate, and fine irregularities are formed on the surface thereof. An optical film 3 made of a diffusion sheet, a prism sheet, or the like is disposed on the light guide 4 for the purpose of increasing the front brightness of the LCD. Under the light guide 4, light is efficiently transmitted into the light guide. For the purpose of propagation, a reflector 5 having a surface coated with a highly reflective material such as silver is disposed. An LED 6 is disposed at the end of the light guide 4. The film substrate 7 is configured by applying a copper foil pattern on an insulating material such as polyimide, and the LED 6 is mounted with a material such as solder and connected in a pattern. This film substrate not only serves to supply current to the LED from the outside, but also to hold the light guide and the LED in a relatively appropriate position so that the light from the LED efficiently enters the light guide. It also has a function. On the opposite side of the film substrate 7 to which the LEDs are attached, a heat sink-like heat radiating member 8 is disposed. For example, the heat radiating member 8 is a member having a concavo-convex cross section so as to increase the surface area by processing a metal having high thermal conductivity such as copper or aluminum. The heat radiating member 8 and the film substrate 7 are bonded and fixed with a silicone adhesive or the like having high thermal conductivity.

  In FIG. 1, the liquid crystal driving IC 2 and the LED 6 are provided on the same side of the display device. In other words, the liquid crystal driving IC 2 and the LED 6 are drawn in a positional relationship facing each other. The reason for this configuration is to minimize the size of the entire display device with respect to the display area. This is because if the LED mounting portion and the IC mounting portion that do not contribute to the screen display are provided on different sides, the external dimensions of the display device will increase accordingly.

  As described above, according to the configuration of this embodiment, the heat generated by the current flowing through the LED 6 is mainly transferred to the film substrate 7 and further transferred to the heat radiating member 8 through the adhesive. . That is, the heat generated from the LED is effectively released from the heat radiating member without being trapped in itself. Therefore, heat is not transferred to the liquid crystal driving IC arranged in the vicinity of the LED, so that the post-warm compensation circuit is not affected by heat, and display quality such as inversion phenomenon in gradation display is displayed. It is possible to prevent a decrease in the above. Further, heat is not transferred to the inside of the liquid crystal panel, and deterioration of display quality such as reduction of contrast ratio can be prevented.

  The configuration of the liquid crystal display device of this example is schematically shown in FIG. As shown in the figure, this is an example in which the heat dissipating member is extended to the lower part of the reflector and bonded to the reflector. Since other parts are the same as those in the first embodiment, the duplicate description is omitted.

  According to this structure, since the heat radiation area of the heat radiating member becomes larger, the heat radiation effect is further enhanced. Therefore, the display quality is further stabilized. In addition, since the heat dissipation effect has further increased, it is possible to increase the current that can be passed through the LED and to increase the luminance of the backlight. Furthermore, since the heat radiating member also functions as a support for the reflector and the film substrate, the light guide and the LED hold a relatively appropriate position, and light from the LED is efficiently guided Since it came into the body, it was possible to stabilize the brightness of the backlight.

  In each of the above-described embodiments, a metal member is used as the heat dissipation member. However, the material is not limited to a metal, and may be a material having high thermal conductivity characteristics. As long as the surface area can be obtained, the same effect can be obtained with any shape.

  Since a liquid crystal display device having excellent heat dissipation characteristics can be provided, display quality of a mobile phone or the like can be improved. Furthermore, according to the present invention, since the current flowing through the LEDs can be increased, the number of LEDs can be reduced, which can contribute to cost reduction of the liquid crystal display device.

It is sectional drawing which shows typically the structure of the liquid crystal display device which concerns on 1st Example of this invention. It is sectional drawing which shows typically the structure of the liquid crystal display device which concerns on 2nd Example of this invention.

Explanation of symbols

1 LCD panel 2 LCD driver IC
3 Optical Films 4 Light Guide 5 Reflective Film 6 Light Emitting Diode 7 Film Substrate 8 Heat Dissipation Member

Claims (7)

A display device having a non-self-luminous display element and a lighting device for irradiating the display element with light,
The illuminating device is provided on a back surface of a surface on which the light source of the circuit board is mounted, a light source, a circuit board on which the light source is mounted, a light guide that guides light from the light source to the display element, and A display device comprising a heat radiating member.   The display device according to claim 1, wherein a semiconductor element is directly mounted on the display element, and the semiconductor element and the light source are provided on the same side of the display device.   The backside of the light guide includes a reflection plate that reflects light toward the display element, and the heat dissipation member is also bonded and fixed to the reflection plate. The display device described.   The display device according to claim 1, wherein the display element is a liquid crystal display element whose optical characteristics change with temperature.   The display device according to claim 4, wherein the semiconductor element is a liquid crystal driving IC.   The display device according to claim 1, wherein the light source is an LED element.   The display device according to claim 1, wherein the circuit board is a film substrate.

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