JP2005017556A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which failure caused by an increased heat release value is kept to a minimum even when the heat release value increases due to deterioration of a light source of a lighting device. <P>SOLUTION: In the liquid crystal display device 1, the lighting device 4 is arranged between a liquid crystal display plate 2 disposed on the front face and a rear lid 3 disposed on the rear face wherein a linear light source 8 is disposed along an edge of a light guide plate 6 disposed in parallel to the liquid crystal display plate 2. A heat transmission sheet 13 composed of aluminum with high thermal conductivity is stuck to the rear lid 3 in contact with an electrode socket 10 of the linear light source 8 so as to suppress local temperature rise by radiating heat produced from the electrode socket with the heat transmission sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device suitable for application to illumination in a thin liquid crystal display device, and in particular, a liquid crystal display in which heat generated by deterioration of a light source is conducted and diffused by a heat transfer sheet. Relates to the device.
[0002]
[Prior art]
Conventionally, since this type of liquid crystal display device tends to be thinned, an edge light system in which the light source is arranged on the side surface of the light guide is often used. This edge light system is generally used as a light source by arranging linear (tubular) cathode tubes on both sides or one side of a light guide.
[0003]
As such an edge light type liquid crystal display device, for example, there is one disclosed in Patent Document 1 below. FIG. 7 is a diagram showing the configuration of the liquid crystal display device disclosed in Patent Document 1. In FIG. The liquid crystal display device 12 includes a light guide plate 21 disposed in parallel to the liquid crystal display plate 11 behind the liquid crystal display plate 11, a light source 22 disposed at an end of the light guide plate 21, and light in the light guide plate 21. A reflection sheet 23 that reflects toward the liquid crystal display panel 11 is provided, and the liquid crystal display panel 11 is irradiated from behind by the illumination device 12.
[0004]
As the light source 22, a lamp such as a cold cathode tube or a hot cathode tube is used, and is provided at both ends or one end of the light guide plate 21 made of polymethyl methacrylate or the like. In addition, a light source reflector 27 is provided so as to be in close contact with the outer periphery of the light source 22 in order to improve the light incident efficiency on the light incident end face of the light guide plate 21. Further, a structure is generally employed in which a reflection sheet 23 is provided on the back surface of the light guide plate 21 and a diffusion sheet 24 is provided on the light output surface of the front surface of the light guide plate 21 for the purpose of uniform luminance of the irradiated surface.
[0005]
The illuminating device 12 having such a configuration guides the light from the light source 22 to the light guide plate 21 and irradiates the liquid crystal display plate 11 from the rear. A temperature rise occurs. If this heat is transmitted uniformly throughout the light guide plate 21, the temperature distribution of the liquid crystal display plate 11 becomes uniform. However, as the liquid crystal display device is made thinner, the light guide plate 21 is also made thinner, and the heat is increased accordingly. There is a tendency for the conduction to deteriorate and the variation in temperature distribution in the liquid crystal display device to deteriorate.
[0006]
Therefore, when the liquid crystal display device is driven, a so-called white spot phenomenon occurs due to a temperature rise in the entire end portion of the effective display area of the liquid crystal display plate 11 on the side where the light source 22 is provided, and the display quality of this portion is lowered. This is a big problem in the reliability of the liquid crystal display device.
[0007]
Therefore, in the conventional technique shown in Patent Document 1 below, the heat in the vicinity of the light source 22 is conducted to the rear surface of the reflection sheet 23 arranged behind the light guide plate 21 to the light guide plate 21, and the temperature distribution of the light guide plate 21 is made uniform. The heat conductive sheets 25a and 25b are provided. As a result, heat due to a local temperature rise in the vicinity of the light source 22 is efficiently conducted, the temperature distribution of the light guide plate 21 and the liquid crystal display plate 11 is made uniform, and the white spot phenomenon at the end of the effective area of the liquid crystal display plate 11 occurs. Had eased. Further, it is disclosed that the heat conductive sheets 25a and 25b are provided outside the display area on the front surface of the light guide plate 21.
[0008]
As described above, in the conventional liquid crystal display device, the heat generation in the light emitting portion of the light source cannot be ignored, and the occurrence of the white spot phenomenon of the liquid crystal display plate due to the heat generation is avoided by adopting the configuration as described above.
[0009]
[Patent Document 1]
Japanese Utility Model Publication No. 5-21238
[Problems to be solved by the invention]
However, liquid crystal display devices in recent years have tended to be thinner, and the display plates and liquid crystal display devices have inevitably become thinner. For this reason, in the liquid crystal display device, the space around the light source is reduced, and the influence of heat generated from the light source has become a serious problem. In particular, in a thin and small liquid crystal display device, the influence of the amount of heat generated in the lighting device becomes larger and cannot be ignored.
[0011]
In general, thermal design in an electronic device such as a liquid crystal display device is generally performed on the assumption that each component or member satisfies the design conditions. For example, the amount of heat generated by the light source depends on the design conditions of the light source. It is calculated on the assumption that it is used within the range of the lifetime, and based on this calorific value, the temperature simulation of each part in the device is performed to determine the housing material selection and heat dissipation structure, It is intended to provide the user with a safe device that has the display ability.
[0012]
By the way, according to the research by the inventors of the present application, not all light sources used in the liquid crystal display device can be used up to the expected life, and some variations are seen depending on the light sources. And when it was used exceeding the assumed lifetime, or as the assumed lifetime approached, it was confirmed that the deterioration of the electrode part rapidly progresses and the calorific value rapidly increases. One reason for this is that so-called sputtered material accumulates, and the glass tube and the electrode are integrated.
[0013]
In particular, in a light source (fluorescent lamp) having a diameter of 1 to 4 mm used for a thin and small liquid crystal display lighting device, the electrode is also small. The progress was more rapid, and according to the experiments by the inventors, it was confirmed that the temperature of the socket portion provided with the electrode reached 90 ° or more. In addition, it is difficult for the user to determine the deterioration as long as the cathode tube is lit, and there is currently no means for determining the deterioration.
[0014]
For this reason, even if the replacement of the light source, which is a part of the product or its instruction manual, is clearly indicated and recommended to the user, the user must There is no guarantee that the light source will be replaced in accordance with the recommendations, and even under such circumstances, it is required to design the product so that the housing will not ignite or cause a burn to the user.
[0015]
In the liquid crystal display device of Patent Document 1, such a consideration is not made, and the reflection sheet disposed behind the light guide plate is simply not adversely affected by the normal display function. The rear surface has a structure in which heat in the vicinity of the light source is conducted to the light guide plate and a heat conductive sheet for making the temperature distribution of the light guide plate uniform is provided, and heat in the light emitting part of the light source is efficiently conducted to guide the light guide plate and The temperature distribution of the liquid crystal display panel is made uniform, and the white spot phenomenon at the end of the effective area of the liquid crystal display panel is alleviated.
[0016]
Therefore, the liquid crystal display device disclosed in Patent Document 1 has a problem that it cannot cope with an extreme increase in the amount of heat generation at the end of the life of the light source (the life assumed at the time of design) as described above.
[0017]
That is, there is a possibility that the temperature rise due to the increase in the heat generation amount may reach a temperature at which the back cover in contact with the electrode socket portion of the light source can be dissolved beyond the expected range. Since this back cover is formed of a synthetic resin, the melting temperature is not higher than that of a metal. For this reason, not only does the back cover part in contact with the electrode socket part dissolve, but there is also a possibility of causing a fire. In addition, there is a possibility that an accident may occur in which a hand is accidentally touched to cause a burn. Of course, it is conceivable to form the back cover with a material having a high melting temperature, but there are restrictions on forming the back cover with a material other than a synthetic resin from the viewpoint of ease of molding, electrical insulation effect, cost, etc. Is accompanied.
[0018]
The inventor of the present application has conducted various studies in order to solve the above-described problems, and as a result, by providing a heat transfer sheet in contact with the electrode socket portion of the light source, the heat in the vicinity of the electrode portion is conducted and diffused. The present inventors have found that the temperature rise can be stopped to such an extent that the back cover can be melted, ignited, or burned even if the user touches it by hand, and the present invention has been completed.
[0019]
That is, the present invention has an object to solve the above-mentioned problems, and even if the heat generation amount is increased due to deterioration of the light source, the back cover does not melt or ignite due to the increased heat generation amount, and even if touched, there is no burn. An object of the present invention is to provide a liquid crystal display device capable of stopping the temperature rise to a certain extent.
[0020]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations. That is, the liquid crystal display device according to claim 1 of the present invention includes a light guide plate arranged in parallel to the liquid crystal display plate on the back side of the liquid crystal display plate, a reflection plate arranged on the back side of the light guide plate, and the light guide plate. In a liquid crystal display device comprising a linear light source arranged at an end and a back cover provided on the back side of the light guide plate, a heat transfer sheet is provided so as to be in contact with the electrode socket part of the linear light source It is characterized by. The heat transfer sheet has a long shape in the direction along the longitudinal direction of the linear light source.
[0021]
By adopting such a configuration, the liquid crystal display device transmits the heat to the light emitting portion side of the linear light source even when the electrode portion becomes high temperature due to the deterioration of the linear light source, so that the temperature rise is partially concentrated. Since the action is suppressed, there is an effect that the member in contact with the electrode socket is not adversely affected. Moreover, since the thickness of the heat transfer sheet is thin, it has an effect that is suitable for thinning the liquid crystal display device.
[0022]
According to a second aspect of the present invention, the heat transfer sheet is made of aluminum. By adopting such a configuration, the heat transfer sheet can be formed of a material having high thermal conductivity and low cost, and therefore, adverse effects due to high temperature on the member in contact with the electrode portion can be efficiently and inexpensively eliminated. .
[0023]
Moreover, according to the aspect of Claim 3 of this invention, the heat-transfer sheet was affixed and provided in the back cover which contact | connects the electrode socket of a linear light source. By adopting such a configuration, the heat transfer sheet diffuses heat on the back cover that is most affected by the high temperature generated in the electrode portion, so that it is possible to efficiently suppress the temperature rise with respect to the back cover. Further, the heat transfer sheet can be provided by a simple operation of simply sticking to a part of the back cover.
[0024]
According to a fourth aspect of the present invention, the heat transfer sheet is made of aluminum, and is provided by being attached to a back cover in contact with the electrode socket of the linear light source. By adopting such a configuration, the heat transfer sheet can be formed of a material having high thermal conductivity and low cost, and therefore, adverse effects due to high temperature on the member in contact with the electrode portion can be efficiently and inexpensively eliminated.
[0025]
Further, since the heat transfer sheet diffuses heat on the back cover that is most affected by the high temperature generated in the electrode portion, it is possible to efficiently suppress the temperature rise with respect to the back cover. Further, the heat transfer sheet can be provided by a simple operation of simply sticking to a part of the back cover.
[0026]
Furthermore, according to the aspect of Claim 5 of this invention, the light-guide plate arrange | positioned in parallel with this liquid crystal display board on the back surface side of a liquid crystal display plate, the reflecting plate arrange | positioned on this light-guide plate back surface side, In a liquid crystal display device comprising a linear light source arranged at an end and a back cover provided on the back side of the light guide plate, the back cover is made of a resin material, and the linear light source of the back cover A heat transfer sheet is provided at a portion in contact with the electrode socket portion.
[0027]
By adopting such a configuration, even if the electrode portion becomes high temperature due to deterioration of the linear light source, the heat is transmitted through the heat transfer sheet and diffused, so that the effect of partially concentrating the temperature rise is suppressed. It is possible to prevent the occurrence of an accident that the back cover of the door melts.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. 1 is a front view showing the surface of a liquid crystal display device to which an example of the embodiment of the present invention is applied, FIG. 2 is a rear view showing the back surface of the liquid crystal display device in FIG. 1, and FIG. FIG. 4 is a rear view showing the portion B in FIG. 2 in an enlarged state with the back cover removed, and FIG. 5 is a cross-sectional view taken along line XX in FIG. FIG. 6 is a cross-sectional view taken along line YY of FIG.
[0029]
1, 2, and 5, the liquid crystal display device 1 includes a liquid crystal display plate 2 disposed on the front surface, a back cover 3 disposed on the back surface, an illumination device 4 provided inside, and a back cover for the illumination device 4. And a middle frame 5 that supports the liquid crystal display plate 2 around the liquid crystal display plate 2 and a metal frame 17 that protects the outer periphery of the liquid crystal display plate 2. For the back cover 3 and the middle frame 5, for example, a resin material such as polycarbonate is used.
[0030]
3-6, the illuminating device 4 forms the reflective surface by arrange | positioning in the back surface of the light guide plate 6 provided between the back cover 3 and the middle frame 5 in parallel with the liquid crystal display plate 2, and the light guide plate 6. In FIG. And a linear light source 8 provided along the end of the light guide plate 6. The linear light source 8 is disposed in the space formed by the middle frame 5 and the back cover 3 at the end of the light guide plate 6.
[0031]
The linear light source 8 is formed of a cathode tube, and the electrode sockets 10 at both ends of the tube 9 are corner portions of the lighting device 4, and the back cover 3 and the middle at a position where they do not overlap with the liquid crystal display panel 2 in plan view. It is held and fixed to the frame 5. Furthermore, the linear light source 8 and one end of the light guide plate 6 are sandwiched by a flexible reflective sheet 11 bent in a U shape. As the reflection sheet 11, for example, a white resin sheet made of polyethylene terephthalate (PET) is used. Between the tube 9 portion of the linear light source 8 and the reflection sheet 11, 1 to 3 ring-shaped spacing members 12 are interposed. The spacing member 12 is preferably configured to maintain a constant spacing between the linear light source 8 and the reflection sheet 11 in order to increase the reflection efficiency.
[0032]
A heat transfer sheet 13 made of aluminum having high thermal conductivity is attached to the back cover 3 in contact with the electrode socket 10. The heat transfer sheet 13 has a rectangular shape and extends long in the direction of the tube 9 from a portion that is in general contact with the electrode socket 10. That is, the heat transfer sheet 13 has a long shape in the direction along the longitudinal direction of the linear light source 8.
[0033]
The light guide plate 6 is provided with the reflection plate 7 so that the back side thereof becomes a light reflection surface. On the front surface of the light guide plate 6, a light diffusing sheet 14 and a prism sheet 15 are laminated to form a light emission surface.
[0034]
Next, the operation of the liquid crystal illumination device having the configuration according to the embodiment of the present invention will be described.
[0035]
When the electrodes in the electrode sockets 10 formed at both ends of the light source 8 are energized and discharged between them to cause the light source 8 to emit light, this light is reflected by the reflection sheet 11 and from the end of the light guide plate 6 to the inside. To. The light reaching the light guide plate 6 is guided to the front light exit surface by the rear reflection plate 7. The light guided to the light exit surface passes through the light diffusion sheet 14 and the prism sheet 15 and illuminates the liquid crystal display panel 2 from the back side.
[0036]
When the liquid crystal display device 1 is small, the diameter of the tube 9 of the linear light source 8 is extremely thin, for example, about 1 to 4 mm. The linear light source 8 is deteriorated by long-time use. In particular, when the end of the life assumed at the time of design is reached, the deterioration of the electrode portion rapidly proceeds, and the amount of heat generated in the electrode socket 10 portion rapidly increases. Increase.
[0037]
In general, heat generated in the tube 9 portion of the linear light source 8 is easily transmitted uniformly as a whole because there is a relatively large space between the tube 9 portion and the back cover 3 or the inner frame 5. However, the heat generated in the electrode socket 10 is confined in the electrode socket 10 portion of the heat source because the electrode socket 10 is substantially sealed.
[0038]
However, this heat is transmitted to the heat transfer sheet 13 at the position in contact with the electrode socket 10 and is transferred toward the tube 9.
[0039]
When the linear light source 8 further deteriorates, the illuminance decreases and the use of the linear light source 8 stops because it does not serve as a lighting device. Until then, the heat generated from the electrode socket 10 is diffused by the heat transfer sheet 13, and a high temperature portion that melts the back cover 3 does not occur.
[0040]
As a result of the experiment, when the conventional heat transfer sheet 13 was not used, the temperature at the back cover 3 in the electrode socket 10 part was 90 ° or more, but by using the heat transfer sheet 13, The temperature dropped to around 80 °. As a result, even the resin back cover 3 was not dissolved.
[0041]
As described above, according to an example of the embodiment of the present invention, the illuminating device 4 for liquid crystal display is made of a material having high thermal conductivity in the back cover 3 portion in contact with the electrode socket 10 of the linear light source 8. A heat transfer sheet 13 made of aluminum is attached. Therefore, even if the linear light source 8 deteriorates and the amount of heat generated from the electrode socket 10 increases, this heat is diffused by the heat transfer sheet 13 having a relatively large surface area. Therefore, it is possible to prevent the temperature from being concentrated at one point and partially becoming high.
[0042]
In particular, in the case where the liquid crystal display device 1 is small and thin, since the back cover 3 and the electrode socket 10 are in contact with each other with substantially no gap, the heat transfer sheet 13 generates heat. The effect of diffusion is great.
[0043]
In the example of the embodiment of the present invention, the heat transfer sheet 13 is attached to the back cover 3, but the object to be attached is not limited to the back cover 3 and is in contact with the electrode socket 10. You may make it stick to the other member which requires.
[0044]
In addition, in one example of the embodiment of the present invention, the heat transfer sheet 13 is attached to the back cover 3, but is attached to another sheet or member without being attached to the back cover 3. Other methods can also be taken.
[0045]
Furthermore, in the example of the embodiment of the present invention, aluminum is used for the heat transfer sheet 13, but it is also possible to use brass, gold, or silver that is a material having high thermal conductivity without being limited thereto. However, aluminum is adopted from a comprehensive viewpoint such as a heat diffusion effect and cost.
[0046]
【The invention's effect】
As described above, according to the liquid crystal display device of the present invention, even if the electrode becomes high temperature due to deterioration of the linear light source, the heat is transferred to the light emitting part side of the linear light source by the heat transfer sheet. The effect of not adversely affecting the member approaching the part due to the high temperature is produced. In addition, since the heat transfer sheet has a small thickness, there is an effect that is suitable for thinning the liquid crystal display device.
[0047]
Here, the heat transfer sheet is preferably formed of aluminum. Since aluminum is an inexpensive material with high thermal conductivity, it has the effect of effectively eliminating the adverse effects of heat generated by the electrode portions with an inexpensive configuration.
[0048]
In addition, the heat transfer sheet is attached to the back cover in contact with the electrode socket of the linear light source, so that heat is diffused on the back cover that is most affected by the high temperature generated in the electrode part, and effective. Further, the temperature rise of the back cover can be suppressed. Further, the heat transfer sheet can be provided by a simple operation of simply sticking to a part of the back cover.
[0049]
Further, the heat transfer sheet is made of aluminum, and is attached to the back cover in contact with the electrode socket of the linear light source. When aluminum is attached to the back cover, the aluminum has a high thermal conductivity and is an inexpensive material. This produces an effect that an adverse effect on the lid can be efficiently and inexpensively eliminated. At the same time, the heat transfer sheet can be provided by a simple operation of simply sticking to a part of the back cover.
[0050]
Furthermore, the liquid crystal display device according to the present invention is particularly suitable for application to a lighting device in which the back cover is made of a resin material, and has the effect of preventing accidents in which the back cover is melted. Play.
[Brief description of the drawings]
FIG. 1 is a front view showing a surface of a liquid crystal display device to which an example of an embodiment of the invention is applied.
2 is a rear view showing a rear surface of the liquid crystal display device in FIG. 1. FIG.
3 is an enlarged rear view of a portion A in FIG. 2 with a back cover removed. FIG.
4 is an enlarged rear view showing a portion B in FIG. 2 with a back cover removed. FIG.
FIG. 5 is a cross-sectional view of FIG. 3 taken along line XX.
6 is a cross-sectional view taken along line YY of FIG.
FIG. 7 is a diagram illustrating a configuration of a conventional liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Liquid crystal display plate 3 ... Back cover 4 ... Illuminating device 5 ... Middle frame 6 ... Light guide plate 7 ... Reflection plate 8 ... Linear light source 9 ... Tube 10 ... Electrode socket 13 ... Heat transfer sheet

Claims (5)

A light guide plate disposed on the back side of the liquid crystal display plate in parallel with the liquid crystal display plate, a reflector disposed on the back side of the light guide plate, a linear light source disposed on an end of the light guide plate, A liquid crystal display device comprising a back cover provided on the back surface side, wherein a heat transfer sheet is provided so as to be in contact with the electrode socket portion of the linear light source. The liquid crystal display device according to claim 1, wherein the heat transfer sheet has a long shape in a direction along a longitudinal direction of the linear light source. The liquid crystal display device according to claim 1, wherein the heat transfer sheet is provided by being attached to the back cover in contact with the electrode socket portion of the linear light source. The liquid crystal display device according to claim 1, wherein the heat transfer sheet is made of aluminum. A light guide plate arranged in parallel with the liquid crystal display plate on the back side of the liquid crystal display plate, a reflection plate arranged on the back side of the light guide plate, a linear light source arranged at an end of the light guide plate, In a liquid crystal display device comprising a back cover provided on the back side,
A liquid crystal display device, wherein the back cover is made of a resin material, and a heat transfer sheet is provided on a portion of the back cover that is in contact with the electrode socket portion of the linear light source.

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