JP2006018171A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device which can make temperature distribution of a panel uniform over the interior of the face of the panel while maintaining a compact and flat structure. <P>SOLUTION: In the panel 1, self-luminous optical elements are arrayed as pixels for displaying an image and is accompanied by heat generation at the time of emitting light. Heat-transfer materials A, B and C have high thermal conductivity to transfer the heat generated in the panel 1 to a chassis 2. The chassis 2 cools the panel 1 by radiating the heat transferred via the heat-transfer materials A, B and C to the outside. The panel 1 has a deviation in the temperature distribution in the surface and is relatively divided into a high-temperature area and a low-temperature area. Heat-transfer materials A, B and C have high thermal conductivity in the portion corresponding to high-temperature area of the panel 1 and are low in the the thermal conductivity in the portion corresponding to the low-temperature area of the panel 1 and negate the deviation of the temperature distribution of the panel 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image display device comprising a display panel, a heat radiation chassis disposed on the back surface of the display panel, and a heat transfer material interposed therebetween. More specifically, the present invention relates to a technique for uniformizing the surface temperature distribution of a panel that generates heat during display.

  Flat panel displays are widely used in products such as computer displays, portable terminals, and televisions. Currently, liquid crystal display panels are mainly used, but the narrow viewing angle and slow response speed continue to be pointed out. On the other hand, an organic EL display formed of a self-luminous element can overcome the above-mentioned viewing angle and responsiveness problems, and can achieve a thin form, high brightness, and high contrast that do not require a backlight. It is expected as an alternative next-generation display device.

  By the way, it is generally known that a light emitting element in an organic EL display has a characteristic that the light emitting element deteriorates in proportion to the amount of light emission and time. At the same time, the deterioration rate varies depending on the temperature of the element itself. It is also known that it is a big problem. Since the organic EL light emitting element is a self-luminous type, it generates heat during operation and generates a higher amount of current as it achieves higher luminance, and generates heat at a higher temperature. It is also known that the higher the temperature, the faster the deterioration.

  On the other hand, flat panel displays always have the following two temperature irregularities. This is not due to the display pattern, but due to the shape and arrangement. The first is a temperature decrease due to conduction of heat transmitted from the outer peripheral light emitting portion to the adjacent frame non-light emitting portion outside. Since there is no light emitting element in the frame portion, the temperature is always equal to or lower than the light emitting portion, and the temperature of the outer peripheral light emitting portion can be lowered by conducting heat there. This was confirmed by measurement that an area of about 20 mm from the outer periphery was most affected in an organic EL display panel using glass.

  The second is a temperature drop caused by cooling the lower part of the light emitting part by air convection. A flat panel display is generally used in an upright position as the size increases, and air convection tends to occur near the light emitting portion. At the lower end, air at a temperature close to the surrounding environment convects, so that the temperature of the light emitting section is lowered. However, since the air convection in the vicinity of the light emitting part is warmed by the heat of the light emitting part as it goes upward, the temperature of the light emitting part cannot be lowered beyond a certain distance. This was also confirmed by measurement to be most affected in an area of about 200 mm from the lower end.

  That is, in the light emitting surface formed by the light emitting element of the display panel, even if light is emitted uniformly with the same gradation data, the temperature unevenness due to the above-mentioned causes occurs, and the temperature is high. As a result of the difference in deterioration rate between the low and high areas, and the brightness decrease rapidly in the high temperature area, the same area as the temperature unevenness appears as uneven brightness lifetime deterioration (fixed brightness unevenness). Therefore, it was necessary to make the temperature distribution in the light emitting surface as uniform as possible.

As conventional techniques for making the temperature distribution in the light emitting surface as uniform as possible, there are the following Patent Documents 1 to 4.
JP 2003-295776 JP 2001-147644 A JP 2000-081843 A JP2003-036032

  Patent Document 1 controls the temperature controller based on the temperature detected from the light emitting element and the information that assumes the transition of the temperature rise, and warms or cools the regionized portion to make the temperature within the light emitting surface uniform. Adjust to. This can actually detect the temperature and control the temperature to be constant, but it is necessary to provide a temperature detection structure and a temperature adjustment structure, which makes the structure complicated and leads to an increase in cost. There was a problem.

  Patent Document 2 adopts a structure in which a heat-dissipating chassis is fixed to the back side of the non-display area portion from the display area of the panel by using an adhesive, so that the chassis can be provided even if there is uneven temperature on the outer periphery of the panel. By uniformly conducting heat, the temperature difference between the non-display area and the display area is reduced. This is a relatively simple structure, and it is good to reduce the temperature unevenness, but it does not completely correct the temperature unevenness of the outer periphery, and when using the panel upright, the lower part is caused by air convection. Since the whole including the heat radiating chassis is affected with respect to the temperature drop caused by cooling, there is a problem that the correction effect is hardly obtained.

  In Patent Document 3, a special air tray structure is provided on the back surface of the panel so that the cooling air is evenly distributed in the surface, thereby reducing temperature and reducing temperature unevenness. Although this can realize temperature rise suppression and temperature unevenness reduction, there is a problem in that it requires a blower structure such as a fan for sending cooling air, resulting in noise and cost increase.

  In Patent Document 4, the heat dissipation chassis is brought into contact only at the upper and lower portions of the back of the panel, so that the heat of the upper portion is transferred to the lower portion, and at the same time, an air reservoir portion with poor air heat dissipation efficiency is provided at the lower portion. The air reservoir is warmed by the heat transmitted to the lower part through the air and prevents the lower temperature from being lowered. Although it is effective to transfer the heat of the upper part to the lower part and make the temperature uniform, in fact, the entire structure cannot avoid the influence of air convection. In addition to the limitation of the effect of transmitting to the air, the air accumulation part is made using the thickness of the backlight of the liquid crystal and needs a certain amount of thickness, which is as thin as an organic EL display. There was a problem that it was not suitable for the emphasis form.

  In other words, the conventional configuration in which the back of the panel is covered with a heat transfer material or heat dissipation material with high thermal conductivity is a simple structure, but when the panel is used upright, the heat transfer material, heat dissipation There was a problem that the temperature difference between the upper and lower sides could not be completely removed due to the influence of air convection including the materials. In addition, when the heat of the upper part is transmitted to the lower part, a special space, a cooling structure by blowing air, or a heat pipe is used, the structure for realizing the contents will increase the cost. In addition, all of them require a certain amount of thickness and space, and there is a problem that they are not very suitable for use in a flat panel such as an organic EL display that emphasizes thinness.

  SUMMARY OF THE INVENTION In view of the above-described problems of the prior art, an object of the present invention is to provide an image display device that can make the temperature distribution of a panel uniform in a plane while maintaining a compact and flat structure.

  In order to achieve this purpose, the following measures were taken. That is, the present invention is an image display device comprising a display panel, a heat radiating chassis disposed on the back surface of the display panel, and a heat transfer material interposed therebetween, wherein the panel is a pixel for displaying an image. Self-luminous elements are arranged, each self-luminous element generates heat when it emits light by itself, and the heat transfer material has thermal conductivity that transmits heat generated in the panel to the chassis, and the thermal conductivity is The chassis is locally different in the plane of the panel, and the chassis dissipates heat transferred through the heat transfer material to cool the panel.

  Specifically, the panel has a biased temperature distribution in the plane and is relatively divided into a high temperature region and a low temperature region, and the heat transfer material has a thermal conductivity of a portion corresponding to the high temperature region of the panel. The thermal conductivity of the portion corresponding to the low temperature portion of the panel is low and the temperature distribution of the panel is canceled out. For example, the inner side of the panel is a high temperature part and the outer side surrounding the panel is a low temperature part. Correspondingly, the heat transfer material has high inner heat conductivity and lower outer heat conductivity. . Depending on the application, the panel is placed upright, with the upper part being a high temperature part and the lower part being a low temperature part. Correspondingly, the heat transfer material has a high thermal conductivity on the upper side and a low thermal conductivity on the lower side. It has become.

  According to the present invention, a lower temperature portion is used by selecting and using a heat transfer material having a poorer heat conduction characteristic to prevent the thermal cooling effect, thereby obtaining a uniform in-plane temperature distribution while partially raising the temperature. Thus, there is an effect that a difference in deterioration rate of light emitting elements such as an organic EL element can be suppressed and fixed luminance unevenness due to pixel deterioration can be prevented. In addition, it does not require a special space or a structure that impairs thinness, and the temperature unevenness can be partially changed in the area of the thickness of the heat transfer material that has been used in the past. There is an effect that the temperature distribution in the light emitting surface can be made uniform in a thin form. Further, according to the present invention, since the temperature unevenness can be corrected with only a simple heat dissipation structure regardless of the display data signal, there is an effect that the original video display quality is not impaired at all.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of an image display device according to the present invention, and is a longitudinal sectional view and a rear view at a horizontal intermediate position. However, the chassis is removed from the rear view. As shown in the figure, the image display device of the present invention comprises a display panel 1, a heat-dissipating chassis 2 disposed on the back surface thereof, and heat transfer materials A, B, and C interposed therebetween. The panel 1 has self-luminous elements arranged as pixels for displaying an image, and each self-luminous element generates heat when it emits light by itself. The heat transfer materials A, B, and C have thermal conductivity that transfers heat generated in the panel 1 to the chassis 2. The thermal conductivities of the heat transfer materials A, B, and C are different within the plane of the panel 1. The chassis 2 dissipates the heat transmitted through the heat transfer materials A, B, and C to cool the panel 1.

  Specifically, the panel 1 has an uneven temperature distribution in the plane, and is relatively divided into a high temperature region and a low temperature region. In the heat transfer materials A, B, and C, the thermal conductivity of the portion corresponding to the high temperature portion of the panel 1 is high, and the thermal conductivity of the portion corresponding to the low temperature portion of the panel 1 is low. To cancel the bias. In the case of this embodiment, the inside of the panel 1 is a high-temperature part, and the outside surrounding it is a low-temperature part. Correspondingly, the inner heat transfer material A has a high thermal conductivity and the outer heat transfer material B. Has low thermal conductivity. The panel 1 is arranged upright according to the use such as for a television screen, and in this case, the upper side is a high temperature part and the lower side is a low temperature part. Correspondingly, the heat transfer materials A and B on the upper side have high heat conductivity, and the heat transfer material C on the lower side has low heat conductivity. That is, the thermal conductivity of the heat transfer materials A, B, and C is set such that A> B> C.

  A sheet-like heat transfer material is commercially available, and is provided, for example, as a trade name TM sheet from Furukawa Electric Co., Ltd. The heat transfer sheet is a functional material composed mainly of silicon-based, acrylic-based or ethylene-propylene-based rubber, and various fillers added to improve heat dissipation and flame retardancy. Since the heat transfer sheet is flexible and has adhesive strength, the heat transfer sheet can be in close contact with the heat generating component, the heat sink or the heat radiating chassis to efficiently dissipate heat. The heat transfer sheet has a thickness of about 0.5 to 4 mm, and a thermal conductivity (W / mK) of about 0.6 to 2.5. In this embodiment, in order to reduce the thickness of the flat image display device as much as possible, a heat transfer sheet having a thickness of 0.5 mm is used. The thermal conductivity is based on 1 W / mK, and is appropriately selected in the range of 0.6 to 2.5 W / mK depending on the degree of deviation of the temperature distribution of the panel. As described above, heat transfer sheets having different characteristics such as thermal conductivity are commercially available as trade name TM sheets from Furukawa Electric Co., Ltd., and various grades can be selected according to the purpose of use.

  The panel 1 shown in FIG. 1 is an organic EL display panel, for example. The front substrate 11 which is two glass substrates, and the back substrate 10 are provided, and an organic EL display panel is formed by bonding these together. The front substrate 10 side is a light emitting surface. The heat radiating chassis 2 is made of a metal having good thermal conductivity such as aluminum and has an area covering at least the back substrate 10. In order to dissipate the heat generated in the organic EL display panel 1 by the heat radiating chassis 2, the heat transfer materials A and B having good heat conductivity between the rear glass substrate 10 of the organic EL display panel 1 and the heat radiating chassis 2. , C are in close contact with each other. However, the thermal conductivity of the heat transfer materials A, B, and C is set such that A> B> C corresponding to the surface temperature distribution of the panel 1.

  Here, the surface temperature distribution of the panel will be described. FIG. 2 is a schematic diagram showing the surface temperature distribution of the panel 1. As shown in the drawing, the temperature of the peripheral portion is lower than that of the central portion of the light emitting unit 100, and this is a region where temperature unevenness occurs. Compared to the central portion of the light emitting unit 100, the peripheral portion loses heat due to heat conduction or the like, and thus the temperature is low.

  The temperature distribution of the corner portion of the panel 1 and the portion along the diagonal line (shown by a one-dot chain line) is shown in a graph. This graph shows distance on the horizontal axis and temperature on the vertical axis. As is apparent from the graph, it can be seen that the temperature of the end portion is lower than the center of the light emitting portion over a width of about 20 mm.

  FIG. 3 is another schematic diagram showing the deviation of the temperature distribution of the panel. As shown in the drawing, the light emitting unit 100 is a region where the temperature of the lower part is lower than that of the upper part and temperature unevenness occurs. This is because when the panel 1 is placed upright, the lower part is relatively strongly cooled by the convection of the cooling air. The temperature distribution at the bottom of panel 1 is shown in the graph. As is apparent from the graph, it can be seen that the temperature at the bottom of the panel is lower at a width of about 200 mm than at the top and center of the panel.

  FIG. 4 is a schematic diagram in which the temperature distributions shown in FIGS. 2 and 3 are synthesized. As shown in the drawing, the temperature of the light emitting unit 100 of the panel 1 is lower than that of the central part. Moreover, the temperature of the lower part is also lower than the central part. The temperature distribution along the central vertical line of panel 1 is shown in the graph. As shown in the figure, the temperature is lower in the range where the outer peripheral portion is about 20 mm wide than the center of the panel. Moreover, the temperature of the lower part is lower than the upper part and the central part in the range of about 200 mm in width.

  FIG. 5 is a schematic diagram showing the effect of the present invention. In order to facilitate understanding, the notation corresponds to the graph of FIG. As described above, the heat transfer materials A, B, and C having different thermal conductivities are arranged corresponding to the uneven temperature distribution on the back surface of the panel. As shown in the figure, a normal heat transfer material A is arranged at the center of the rear glass substrate 10 of the panel, and a heat transfer material B having a lower thermal conductivity than the heat transfer material A is arranged around the periphery thereof. Further, a heat transfer material C having a lower thermal conductivity than the heat transfer material B is disposed at the lower part. In this manner, by arranging different heat conductive heat transfer materials corresponding to the temperature distribution of the panel, the temperature unevenness can be corrected.

  The graph is the temperature distribution along the center vertical line of the panel. The dotted line indicates the temperature distribution before correction, and the solid line indicates the temperature distribution after correction. As is apparent from the graph, the temperature unevenness at the outer periphery of the panel is improved. In addition, the temperature unevenness at the bottom of the panel is remarkably improved. As a result, the temperature distribution along the vertical line of the panel is almost flat, and the deviation of the temperature distribution is substantially eliminated.

  As described above, in the present invention, the temperature unevenness of the panel is corrected by mixing a plurality of heat transfer materials having different heat conduction characteristics. First, the heat transfer material B, which is inferior in heat conductivity to the heat transfer material A, is used for preventing the temperature decrease of the outer peripheral light emitting part. As shown in FIG. 5, the places to be pasted are portions where a temperature decrease is observed in the upper, left, and right portions. By doing in this way, compared with the case where only the heat transfer material A is used, heat becomes difficult to be transmitted to the heat radiation chassis, and the cooling effect is suppressed, so that the temperature rises.

  Similarly, the heat transfer material C, which is inferior in heat conduction characteristics to the heat transfer material B, is used for preventing a temperature drop caused by cooling the lower part of the light emitting part by air convection. As shown in FIG. 5, the pasting portion is a portion where a lower temperature drop is recognized. By doing in this way, compared with the case where only the heat-transfer materials A and B are used, heat becomes more difficult to be transmitted to the heat dissipation chassis, and the temperature further increases. Since the lower region has the greatest temperature drop, use the heat transfer material with the worst heat conduction characteristics. As for the area to be pasted, if it is pasted in all the areas where the temperature drop has occurred, in the area where the temperature drop is small, there is a possibility that it will exceed the original highest temperature. It is preferable to apply to a region having a smaller temperature than the recognized region and a larger temperature drop. By adopting such means, it is possible to obtain a uniform temperature distribution to some extent by selecting various materials having different heat conduction characteristics and changing the area to be bonded.

  As described above, according to the present invention, as the temperature is lower, the heat transfer material having a poorer heat conduction property is selected and used, and the heat cooling effect is hindered, so that the temperature is partially increased and the surface is uniform. Temperature distribution can be obtained, the difference in deterioration rate of the organic EL light emitting element can be suppressed, and fixed luminance unevenness due to pixel deterioration can be prevented. In addition, it does not require a special space or a structure that impairs thinness, and the temperature unevenness can be partially changed in the area of the thickness of the heat transfer material that has been used in the past. There is an effect that the temperature distribution in the light emitting surface can be made uniform in a thin form. Further, according to the present invention, since the temperature unevenness can be corrected with only a simple heat dissipation structure regardless of the display data signal, there is an effect that the original video display quality is not impaired at all.

  FIG. 6 is a block diagram showing a configuration of the organic EL display panel shown in FIG. The display panel 1 includes a pixel array unit 100 in which pixel circuits (PXLC) 101 are arranged in an m × n matrix, a horizontal selector (HSEL) 103, a write scanner (WSCN) 104, a drive scanner (DSCN) 105, a horizontal The signal lines DTL101 to DTL10n selected by the selector 103 and supplied with signals according to luminance information, the scanning lines WSL101 to WSL10m selectively driven by the write scanner 104, and the scanning lines DSL101 to DSL10m selectively driven by the drive scanner 105 are displayed. Have. The pixel array unit 100 is a screen and a light emitting unit.

  FIG. 7 is a circuit diagram showing a configuration example of the pixel circuit shown in FIG. As shown in the figure, the pixel circuit 101 is basically composed of a p-channel thin film field effect transistor (hereinafter referred to as TFT). That is, the pixel circuit 101 includes a drive TFT 111, a switching TFT 112, a sampling TFT 115, an organic EL element 117, and a storage capacitor C111. The pixel circuit 101 having such a configuration is arranged at an intersection between the signal line DTL101 and the scanning lines WSL101 and DSL101. The signal line DTL101 is connected to the drain of the sampling TFT 115, the scanning line WSL101 is connected to the gate of the sampling TFT 115, and the other scanning line DSL101 is connected to the gate of the switching TFT 112.

  The drive TFT 111, the switching TFT 112, and the organic EL element 117 are connected in series between the power supply potential Vcc and the ground potential GND. That is, the source of the drive transistor 111 is connected to the power supply potential Vcc, while the cathode of the organic EL element (light emitting element) 117 is connected to the ground potential GND. In general, the organic EL element 117 is represented by a diode symbol because of its rectifying property. On the other hand, the sampling TFT 115 and the storage capacitor C111 are connected to the gate of the drive TFT111. The gate-source voltage of the drive TFT 111 is represented by Vgs.

  The operation of the pixel circuit 101 is as follows. First, when the scanning line WSL101 is in a selected state (here, low level) and a signal is applied to the signal line DTL101, the sampling TFT 115 is turned on and the signal is written into the storage capacitor C111. The signal potential written in the storage capacitor C111 becomes the gate potential of the drive transistor 111. Subsequently, when the scanning line WSL101 is in a non-selected state (here, high level), the signal line DTL101 and the drive TFT 111 are electrically disconnected, but the gate potential Vgs of the drive TFT 111 is stably held by the holding capacitor C111. . Subsequently, when another scanning line DSL101 is selected (here, at a low level), the switching TFT 112 becomes conductive, and a drive current flows through the TFT 111, TFT 112, and the light emitting element 117 from the power supply potential Vcc toward the ground potential GND. When the DSL 101 is in a non-selected state, the switching transistor 112 is turned off and the driving current does not flow. The switching TFT 112 is inserted to control the light emission time of the light emitting element 117.

  The current flowing through the TFT 111 and the light emitting element 117 has a value corresponding to the gate-source voltage Vgs of the TFT 111, and the light emitting element 117 continues to emit light with a luminance corresponding to the current value. As described above, the operation of selecting the scanning line WSL101 and transmitting the signal applied to the signal line DTL101 to the inside of the pixel circuit 101 is referred to as “writing”. As described above, once a signal is written, the light emitting element 117 continues to emit light at a constant luminance until the next rewriting. At that time, heat is generated, and the temperature distribution of the light emitting unit 100 is uneven due to the uneven heat dissipation.

It is the typical longitudinal cross-sectional view and back view which show the image display apparatus which concerns on this invention. It is a schematic diagram which shows the temperature distribution of a panel. It is a schematic diagram which shows the temperature distribution of a panel. It is a schematic diagram which shows the temperature distribution of a panel. It is a schematic diagram which shows the temperature distribution of the panel of the image display apparatus which concerns on this invention. It is a block diagram which shows the structural example of the panel contained in an image display apparatus. It is a circuit diagram which shows the structural example of the panel contained in an image display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Panel, 2 ... Radiation chassis, 10 ... Back glass substrate, 11 ... Front glass substrate, 100 ... Light emission part, A ... Heat transfer material, B ... Heat transfer Material, C ... Heat transfer material

Claims (4)

An image display device comprising a display panel, a heat-dissipating chassis disposed on the back surface thereof, and a heat transfer material interposed between the two,
In the panel, self-light-emitting elements are arranged as pixels for displaying an image, and each self-light-emitting element generates heat when it emits light by itself,
The heat transfer material has thermal conductivity that transfers heat generated in the panel to the chassis, and the thermal conductivity is locally different in the plane of the panel;
The image display device, wherein the chassis dissipates heat transmitted through the heat transfer material to cool the panel. The panel has an uneven temperature distribution in the plane and is relatively divided into a high temperature region and a low temperature region,
The heat transfer material has a high thermal conductivity in a portion corresponding to a high temperature portion of the panel, and a low thermal conductivity in a portion corresponding to a low temperature portion of the panel,
The image display apparatus according to claim 1, wherein the uneven temperature distribution of the panel is canceled.   The panel has a high-temperature part on the inside and a low-temperature part on the outside, and correspondingly, the heat transfer material has high heat conductivity on the inside and low heat conductivity on the outside. The image display device according to claim 2, characterized in that:   The panel is placed upright, the upper side is a high temperature part and the lower side is a low temperature part, and the heat transfer material has a high thermal conductivity on the upper side and a lower thermal conductivity corresponding to this. The image display device according to claim 2.

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