JP2006343541A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein with respect to a portable type personal computer or the like, light-emitting diodes have come to be used as a back-light light source for a liquid crystal display, a brighter display is required for outdoor use; therefore, the light-emitting diodes are turned into a severe driving state, because they are increased in optical output and this causes intense heat generation, so that it is essential that quick dissipation of this heat be suppressed of the rise in temperature. <P>SOLUTION: A heat-transfer path is formed, by inserting an elastically deformative heat conductive member 71 made of a metal plate having spring properties into a clearance between a wiring substrate 31 mounted with many light-emitting diode chips and a metal case 61, and allowing the member to press against both using the spring elastic restitutive force. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device such as a liquid crystal display used for displaying information on a personal computer or the like, and aims to efficiently diffuse and dissipate heat generated by a backlight light source.

  In recent years, portable personal computers (hereinafter referred to as portable personal computers) have been reduced in weight in order to improve portability. Therefore, the liquid crystal display used for it is also greatly reduced in weight, size and thickness. On the other hand, even if the reduction in thickness and weight is promoted, the brightness of the display cannot be lowered in order to ensure the visibility of the display in consideration of outdoor use. Rather the brightness must be improved.

  In order to make effective use of light from the light source, a number of contrivances have been made to the light guide plate, the reflection film, and the diffusion film.

  In portable use of a portable personal computer, battery driving is a precondition. Therefore, in order to realize longer driving, it is most important to suppress power consumption. However, in order to brighten the display, it is necessary to increase the light output, which is a condition contrary to suppressing power consumption.

  Conventionally, cold cathode ray tubes have been commonly used as display illumination light sources for portable personal computers. However, although the cold cathode ray tube has recently been extended in its life, the brightness is drastically lowered when driven for 10,000 hours or more. Moreover, since it is made of a thin and long glass tube, it has a problem that it is easily broken by an impact during carrying.

  On the other hand, in recent years, brightness improvement and power saving of light-emitting diodes (hereinafter referred to as LEDs) have advanced remarkably and are still under development. In addition, red, green, and blue LEDs, which are the three primary colors of light, are available and the color rendering is improved.

  In recent years, as described above, LED brightness has been improved, color rendering properties have been improved, and costs have been reduced. Therefore, LEDs have been used as illumination light sources such as liquid crystal displays. LED lighting is already common in mobile phones.

  As a backlight light source for a liquid crystal display of a portable personal computer, it is possible to arrange a number of LEDs in a straight line to form a linear light source like a cold cathode ray tube, and to use it as a backlight light source instead of the cold cathode ray tube.

  Even if the temperature of the tube itself rises, the luminous efficiency of the cold cathode ray tube does not decrease, and since the tube is made of glass, there is no need to consider heat dissipation.

  However, since the luminous efficiency of the LED decreases as the temperature of the LED chip increases, it is necessary to suppress the temperature increase as much as possible. When the temperature exceeds 80 ° C., the decrease in luminous efficiency becomes remarkable, so it is essential to suppress the temperature rise to be lower than that.

  The LED is a point light source, and high-density light is emitted from a minute space. For this reason, the temperature of the light source becomes extremely high. Therefore, in order to maintain efficient light emission, it is necessary to quickly dissipate the heat generated by the LED.

  Particularly when LEDs are arranged in various patterns such as a linear arrangement, a square arrangement, and a circular arrangement, and a large number of LEDs are driven, it is necessary to devise heat dissipation so as not to generate heat.

  Therefore, it is conceivable that the heat generated by the LED chip is transferred to the housing (of the portable personal computer) made of a metal such as aluminum or magnesium to dissipate it. An example thereof is disclosed in Patent Document 1.

In Patent Document 1, the heat generated by the light emitter mounted on the mounting substrate is brought into contact with the surface of the mounting substrate opposite to the surface on which the light emitter is mounted using a metal film (or foil). In addition, the other part is brought into contact with the housing, and heat is transferred from the light emitter to the housing via the metal film to radiate heat.
JP 2003-36717 A

  However, in the disclosed example, a metal film is used as a heat transfer body, which is extremely inefficient as a heat transfer path. Further, when the metal film is in contact with the mounting substrate and the housing, the heat transfer resistance at the contact surface is large, and it cannot be said that efficient heat transfer and heat dissipation are performed.

  Furthermore, since the metal film is deformed by a slight force and is formed of a member whose shape is not fixed, it is considered that a difficult operation is involved in the incorporation into the housing.

  The present invention is for solving the above-described problems, and provides a heat transfer structure with high heat transfer efficiency and easy assembly.

  In order to solve the above problems, a metal material such as a copper alloy having a spring property is used as the heat transfer material. The above-described metal material is processed into a long member having a substantially U-shaped cross section, pushed into the gap between the heating element and the metal housing, and using the spring elastic force that it has, The heat generating body and the metal housing are pressed and contacted to perform heat transfer and heat dissipation.

  Since a metal alloy having a spring property (for example, phosphor bronze plate) is used as a member responsible for thermal bridging between the wiring board on the high temperature side and the metal housing on the heat dissipation side, the metal film is used for thermal coupling. Compared to this, the heat conduction capacity is much larger, and efficient heat dissipation can be achieved. As a result, the temperature rise of the LED chip is kept low, the resin material that seals the LED chip is gradually deteriorated, and the lifetime as a backlight light source is kept long.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an LED light source body 1 in which a large number of LED chips 2 are mounted in series on the surface of a wiring board 3. Each LED chip 2 is potted and sealed with a transparent resin 4. As shown in FIG. 1, if the LED chip 2 is mounted directly on the wiring board 3, the utilization efficiency of the radiated light is extremely low.

  In order to illuminate the display more brightly, it is necessary to introduce as much light emitted from the light source as possible into the light guide plate. For that purpose, it is necessary to guide the light emitted from the LED chip to the light incident portion of the light guide plate as much as possible.

  In addition, as shown in FIG. 1, the light emitted from the LEDs arranged at regular intervals has a so-called “eyeball phenomenon” in which the vicinity of the LED chip is brightly illuminated because the LED is a point light source. To do. In order to reduce this, it is desirable that light is diffused in the LED chip arrangement direction so that it approaches a linear light source such as a cold cathode ray tube.

  Hereinafter, an example for increasing the light utilization efficiency and linearizing the light source will be described.

  FIG. 2 shows the LED series module 21. A plurality of LED chips 23 are mounted on a chip base 22 having a rectangular column shape made of a ceramic (alumina or the like) material. The chip base 22 is formed with a plurality of recesses 24 having inclined surfaces on both sides, and the LED chip 23 is bonded to the bottom of the chip base 22 at the center. A wiring circuit that electrically couples the LED chips 23 is formed on the chip base 22.

  The space of the recess 24 is filled with a transparent resin for sealing the LED chip. A transparent resin having a refractive index of about Nd = 1.55 was used.

  Next, the light emission state of the LED chip 23 configured as described above will be described.

  FIG. 3 is an enlarged view of the recess 24 when the LED series module 21 is viewed from the lateral direction. Since the chip base 22 is made of ceramic made of alumina, it has a white color with high reflectivity. Therefore, the light emitted from the LED chip 23 is reflected by the inner wall of the recess 24 and is dispersedly emitted in each direction as indicated by arrows in FIG. In the figure, arrows indicate typical light rays. When used as a backlight, the light beam incident portion of the light guide plate is positioned in front of the light path, and a large amount of light can be guided to the light guide plate by using the chip base 22 to effectively utilize the light. It can be used. Further, since light is appropriately dispersed in the direction of both wings of the LED chip 23, it approaches a linear light source such as a cold cathode ray tube.

  FIG. 4 is a diagram showing a backlight light source 51 that is a plurality of LED series modules 21 arranged and mounted in a row on a wiring board 31 and is used as a backlight light source for a large-sized liquid crystal display. This is what I intended.

  On the wiring board 31, a drive circuit that controls lighting of the LEDs is also constructed together with a wiring circuit to each LED series module 21. As the base material of the wiring board 31, an aluminum plate having good heat conductivity is used in order to quickly diffuse the heat generated by the LED chip 23.

  FIG. 5 is a cross-sectional view of the liquid crystal display unit 50 according to the first embodiment. The liquid crystal display unit 50 includes a light guide plate 52, a reflection sheet 53, a diffusion sheet 54, and a liquid crystal panel 55 in addition to the backlight light source 51 described above.

  Each of these members is mounted and assembled on a backlight frame (not shown).

  The reflection sheet 53 and the diffusion sheet 54 are attached so as to abut against the wiring board 31, and the LED series module 21 group is sandwiched between the both. The reflection sheet 53 is made of aluminum vapor deposition (or silver vapor deposition) on the entire surface and finished to a mirror surface, or a white plastic sheet with high reflectivity and good diffusibility is used. The diffusion sheet 54 has a mirror reflecting tape 54a bonded to a region from the light guide plate end surface 52a to the wiring board 31. Note that the specular reflection tape may be omitted.

  The light beam emitted from the LED chip 23 in the vertical direction is reflected directly or by the inner surface of the reflection sheet 53 or the diffusion sheet 54 and enters the light incident end surface 52 a of the light guide plate 52.

  As described above, the liquid crystal display unit 50 having a very simple structure and high light utilization efficiency can be realized by extending the reflection sheet 53 and the diffusion sheet 54 and sandwiching the LED series module 21 group.

  In addition, you may use the LED light source body 1 as a backlight light source.

  FIG. 6 is a cross-sectional view of the liquid crystal display according to the first embodiment. The liquid crystal display unit 50 is an example of the display device of the present invention, and shows a state when the liquid crystal display unit 50 is incorporated in the metal housing 61.

  The metal housing 61 is made of a metal such as aluminum or a magnesium alloy.

  The lower end side of the wiring board 31 is inserted so as to be in contact with the bottom surface of the metal casing 61. A long heat transfer member 71 having a substantially U-shaped cross section as shown in FIG. 7 is elastically deformed and interposed in a space 62 surrounded by the wiring board 31 and the metal casing 61 formed in this manner. Let The heat transfer member 71 is made of metal and has a spring property. When the heat transfer member 71 is pushed into a predetermined position, one side of the U-shaped cross section is pressed against the back surface of the wiring board 31, and the other side is pressed against the inner surface of the metal casing. As a result, a heat conduction path from the wiring board 31 to the metal housing 61 is formed.

  Compared to the conventional heat transfer using a metal film, the heat transfer capacity and the heat radiation efficiency are improved by using a metal plate, so that the LED can be driven with higher brightness than the conventional one.

  Further, after the liquid crystal display unit 50 is inserted into the metal housing 61, a heat conduction path can be constructed simply by elastically deforming and interposing a U-shaped heat transfer member 71 in an elongated space formed by the two. It is extremely easy to assemble.

  Moreover, since the heat transfer member is elastically deformed and interposed, the thermal joining efficiency when attached is high. Furthermore, if an appropriate amount of thermal conductive grease is applied to the U-shaped heat transfer member 71, the thermal joining efficiency when attached is further increased, and the heat dissipation capability is further improved.

  The display device according to the present invention is useful as a portable liquid crystal display or the like using a backlight light source for which power saving, high luminance, impact resistance, and long life are desired.

The figure which shows the LED light source body in which many LED chips were mounted in series on the surface of a wiring board Diagram showing LED series module The figure which expanded and showed the crevice 24 when seeing LED series module 21 from the horizontal direction The figure which shows the backlight light source 51 which arranged and mounted several LED series modules 21 on the wiring board 31, and lengthened it. Sectional drawing of the liquid crystal display unit 50 which concerns on Embodiment 1. FIG. Sectional drawing of the liquid crystal display which concerns on Embodiment 1 Perspective view of heat transfer member 71

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED light source body 2 LED chip 3 Wiring board 4 Transparent resin 21 LED series module 22 Chip base 23 LED chip 24 Recessed part 31 Wiring board 50 Liquid crystal display unit 51 Backlight light source 52 Light guide plate 53 Reflective sheet 54 Diffusion sheet 55 Liquid crystal panel 61 Metal housing 62 Space 71 Heat transfer member

Claims (4)

A wiring board on which a plurality of light emitters are disposed;
A heat sink made of metal housing or metal,
A display device comprising a heat conductive member made of a metal plate having a spring property and interposed between the wiring board and the metal housing or a heat radiator made of metal by elastic compression deformation.   The display device according to claim 1, wherein the electric wiring circuit of the wiring board is formed on a surface of a metal plate such as copper or aluminum.   The display device according to claim 1, wherein the heat conducting member has a substantially U-shaped cross section.   The display device according to claim 1, wherein the light emitter is a light emitting diode chip.

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