JP2006330354A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of suppressing a local temperature rise of a display panel. <P>SOLUTION: The display device includes a PDP 50 which has a plurality of pixels arranged like a face and displays an image thereon by controlling the quantity of light emitted in each pixel, a chassis 54 disposed along a rear face of the PDP 50, and a driver IC 56a for executing control. The driver IC 56a and a partial area of a principal face of the chassis 54 are thermally coupled through a sheet-like anisotropic heat-conductive member 55 of which the thermal conductivity in a surface creepage direction is higher than that in a thickness direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device such as a plasma display device, and more particularly to a technique for improving heat dissipation efficiency.

In recent years, plasma display devices and liquid crystal displays (hereinafter referred to as “LCDs”) are rapidly spreading as thin and light display devices used in computers and televisions.
As a common configuration in these display devices, a display panel on which an image is displayed by controlling the amount of emitted light for each pixel and a driver IC that controls the amount of emitted light are provided.

In addition to this driver IC, a large number of electronic components are used. However, the driver IC in which a circuit for performing image processing at high speed is integrated is particularly likely to be at a high temperature.
For this reason, in the display panel, the temperature of the region where the driver IC is disposed tends to be higher than the temperature of the other region.
In the plasma display device, an image is displayed using plasma discharge. When the temperature of the display panel is locally increased, discharge conditions become non-uniform and color reproducibility is deteriorated.

In addition, LCDs tend to have a longer life as the temperature of the display panel increases. If the temperature of the display panel increases locally, the display performance of the high-temperature portion decreases with time, and the color reproducibility is still high. There is a problem of getting worse.
For this reason, various heat dissipation measures are taken in display devices such as plasma display devices and LCDs.

For example, as a general heat dissipation measure, a vent is formed in a housing that houses a display panel and a control circuit, and a cooling fan is disposed in the vicinity of the vent.
As a result, the air heated by the heat generated from the electronic components constituting the display panel and the control circuit can be forcibly discharged from the vents to the outside of the housing by the cooling fan, thus improving the heat dissipation efficiency of the display device. (For example, Patent Document 1).
JP 2000-156581 A

However, in recent years, display devices such as plasma display devices and LCDs have increased in screen size and definition, and the number of pixels has increased dramatically. The load tends to increase.
In addition, due to demands for cost saving and space saving, an attempt has been made to increase the processing capacity of each driver IC, that is, the driving frequency and the electric capacity by two times, and halve the number of driver ICs. Yes.

Since the amount of heat generated by the driver IC is proportional to the product of the electric capacity and the driving frequency, the amount of heat generated per one high-performance driver IC described above increases four times that of the conventional driver IC.
Against this background, the amount of heat generated from the driver IC has increased in recent years, and conventional heat dissipation measures can no longer cope with it, and there has been a problem that a local temperature rise of the display panel cannot be avoided. .

The driver IC is provided with a flexible cable for connecting to the display panel.
In this flexible cable, the length of the flexible cable needs to be as short as possible due to cost and electrical design requirements.
For this reason, there is a positional restriction that the driver IC must be disposed on the lower side of the display panel, making the heat dissipation countermeasure more difficult.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a display device capable of suppressing a local temperature rise of a display panel.

  In order to achieve the above object, a display device according to the present invention includes a display panel in which a plurality of pixels are arranged in a plane, and an image is displayed by controlling the amount of light emitted from each pixel, and the display panel A display device having a heat radiating plate disposed along the back surface of the sheet and a control element for performing the control, wherein the sheet-shaped anisotropic having a thermal conductivity in the creeping direction larger than the thermal conductivity in the thickness direction The control element and a partial region of the main surface of the heat radiating plate are thermally coupled via a heat conductive member.

With the above configuration, the heat generated by the control element is conducted to a partial region of the main surface of the heat sink via the anisotropic heat conducting member. However, since it is mainly performed in the creeping direction rather than the thickness direction, the heat generated from the control element is likely to spread over the entire partial area.
For this reason, the local heat transfer to the said heat sink is avoided, and a local temperature rise is suppressed.

  In addition, when the direction opposite to the emission direction is set as the opposite emission direction, the anisotropic heat conducting member includes a first main surface existing on the emission direction side of the heat radiating plate and a second main surface existing on the side opposite to the emission direction. The control element is disposed in a partial region of the second main surface, and the control element is a third main surface existing on the emission direction side of the anisotropic heat conducting member and a fourth main surface existing on the side opposite to the emission direction. It may be arranged in a partial region of the fourth main surface among the surfaces.

With the above configuration, the control element is arranged in a partial region of the fourth main surface of the anisotropic heat conducting member.
In other words, since the anisotropic heat conducting member conducts heat in the inside and then transmits the heat to the heat sink, the heat generated from the control element is anisotropic with a larger area than the control element. Heat can be diffused in the creeping direction in the heat conducting member.

  Furthermore, the anisotropic heat conducting member is disposed in a partial region of the second main surface of the heat radiating plate, and the heat gently transmitted from the anisotropic heat conducting member is transferred to the anisotropic heat conducting member. Compared to the area where the anisotropic heat conducting member is not disposed, that is, the exposed area, the heat sink is rapidly conducted in the creeping direction, and the heat sink is larger than the area. Heat is transferred between them, and efficient heat dissipation is performed.

That is, by performing stepwise heat conduction and heat transfer, heat is dissipated while expanding the heat transfer range, and local temperature rise is suppressed.
And by arranging an anisotropic heat conduction member and a control element in order on the 2nd principal surface of a heat sink, these total thickness can be suppressed small and space saving can also be aimed at.

Further, the anisotropic heat conducting member has a thickness in the partial region of the fourth main surface and a thickness in the remote region of the fourth main surface that is a predetermined distance away from the partial region of the fourth main surface. The thickness in the remote area may be smaller than the thickness in the partial area of the fourth main surface.
In the heat transfer, when the temperature gradient between the heat media that are thermally coupled, that is, the temperature difference is small, the heat transfer is suppressed.

In the remote region, the amount of heat transfer from the anisotropic heat conducting member to the heat sink gradually decreases, and the temperature gradient tends to be small.
For this reason, in the remote region, heat transfer between the anisotropic heat conducting member and the heat radiating plate tends to be small, but by making the thickness of the remote region thinner than the thickness in the partial region of the fourth main surface, Reduces thermal resistance in the thickness direction, promotes heat conduction in the thickness direction of the anisotropic heat conducting member and heat transfer between the anisotropic heat conducting member and the heat sink, and disperses heat over a wide range be able to.

  On the other hand, for the heat conduction in the creeping direction, the ratio of the heat flow path cross-sectional area to the amount of heat moving in the remote area is equal to the partial area of the fourth main surface, that is, the heat flow path cross-sectional area relative to the heat quantity moving in the vicinity of the control element. Even if the thickness of the remote region of the anisotropic heat conducting member is made thinner than the thickness of the partial region of the fourth main surface, the heat transfer in the creeping direction is greatly affected. Absent.

  In addition, the display device includes a housing that houses the display panel, the heat radiating plate, and the control element, and the control element is in a space sandwiched between a main surface of the heat radiating plate and an inner wall of the housing. Further, any main surface of the control element is disposed at a distance from the main surface of the heat radiating plate and the inner wall of the housing, and the anisotropic heat conducting member is at least in the first region. And in the anisotropic heat conducting member, the first region is joined to a main surface of the control element facing the inner wall, and the second region is a main part of the heat sink. It may be bonded to the partial region of the surface.

With the above configuration, heat generated from the control element can be transmitted to the partial region of the main surface of the heat sink while suppressing heat transfer from the control element to the housing.
In addition, a plurality of the control elements are arranged along the edge of the heat radiating plate, and the anisotropic heat conducting member may be extended in a direction perpendicular to the arrangement direction of the control elements. Good.
Since a plurality of control elements are arranged along the edge of the heat dissipation plate, when transferring heat generated from the control element to the heat dissipation plate, rather than providing a heat conduction path in the arrangement direction where there are many heat sources, As in the above configuration, more efficient heat dissipation is performed by providing the heat conduction path in a direction away from these heat sources, that is, in a direction orthogonal to the arrangement direction.

Moreover, the said anisotropic heat conductive member is independently arrange | positioned for every control element, It is good also as the non-contact state between the said adjacent anisotropic heat conductive members.
Thereby, the movement of the heat in the direction orthogonal to the arrangement direction is further promoted.

(Embodiment)
(Constitution)
FIG. 1 is an exploded perspective view of the plasma display device according to the present embodiment.
In the plasma display device 10, a plasma display panel (hereinafter referred to as “PDP”) 50 as an example of a display panel and a chassis assembly 49 that dissipates heat are housed in a case 20, and support for supporting the PDP 50. The body 40 extends downward from the lower part of the case 20.

The PDP 50 is a panel in which discharge cells corresponding to a plurality of sub-pixels are arranged in a plane shape, and an image is displayed by controlling the number of discharges for each discharge cell. The front panel 51 and the back panel 52 overlap each other. Further, the peripheral edges are joined together.
Here, the sub-pixel means a pixel corresponding to each color component of the three primary colors of RGB, and the three sub-pixels of RGB constitute one pixel.

A discharge gas is enclosed between the front panel 51 and the back panel 52.
For the sake of convenience, the main surface of each member, which will be described later, constituting the front panel 51, the back panel 52, and the chassis assembly 49 is the front side facing the same direction as the light emission direction contributing to image display. Let us say the main surface, and the main surface facing in the direction opposite to the radial direction will be referred to as the rear main surface.

The front panel 51 includes a display electrode pair (not shown), a dielectric layer (not shown), and a protective layer (not shown) arranged in this order on the front main surface of a glass substrate.
On the other hand, the rear panel 52 has an address electrode (not shown), a dielectric layer (not shown), and barrier ribs (not shown) arranged in this order on the front main surface of the rear glass substrate, and a phosphor layer (not shown) between the barrier ribs. (Not shown) is formed. The phosphor layers are repeatedly arranged in the order of red, green, and blue.

The front panel 51 and the back panel 52 are bonded to each other with a sealing material, and a gap between the two panels is partitioned by a stripe-shaped partition wall to form a discharge space. Discharge gas is enclosed.
With the above configuration, an image is displayed on the image display surface 53 in response to a signal from a control circuit (not shown) provided on the rear main surface of the PDP 50.

The chassis assembly 49 is a member that improves the surface rigidity of the PDP 50 and further promotes heat dissipation by being attached to the back surface of the PDP 50.
The chassis assembly 49 has a rectangular plate shape, and a plurality of anisotropic heat conductive members 55 leave a gap without contacting each other on a lower side portion on a rear main surface of a chassis 54 as an example of a heat sink. The driver ICs 56a are affixed to the lower side portions of the anisotropic heat conductive members 55.

The chassis 54 is a rectangular plate having a thickness of 1.5 mm made of a material having excellent heat conduction performance such as aluminum. The chassis 54 has a heat conduction such as silicon paste on the rear main surface of the rear panel 52 of the PDP 50. It is joined by the adhesive.
The driver IC 56a has a flexible cable 56b extending from the bottom surface to the electrode of the PDP 50.

Since the flexible cable 56b is an expensive cable and there are a plurality of the flexible cables 56b, there is a demand for shortening for the purpose of cost reduction and circuit impedance reduction.
Therefore, the driver IC 56a is affixed in the vicinity of the lower side portion of the chassis 54 near the interface (not shown) on the PDP 50 side.
The interface and driver IC 56a may be provided in the vicinity of the upper part of the PDP 50. However, the temperature of the upper part of the PDP 50 is likely to be higher than that of the lower part due to the effect of natural convection. Therefore, the driver IC 56a is preferably provided in the lower part of the PDP 50. .

For pasting each member, for example, a heat conductive adhesive 57 (not shown) such as silicon paste or ethylene-propylene rubber is used.
The anisotropic heat conductive member 55 is a graphite sheet having a thickness of 0.5 mm and has a heat transfer coefficient in the creeping direction larger than the heat conductivity in the thickness direction.
More specifically, the ratio of thermal conductivity in the thickness direction and the creeping direction is a ratio of about 1:25.

In the anisotropic heat conducting member 55, heat moves in the thickness direction from the driver IC 56a side to the chassis 54 side, and approximately 25 times the amount of heat actively moves in the creeping direction. Heat conduction is suppressed.
That is, as the ratio of the thermal conductivity in the creeping direction is larger than the ratio of the thermal conductivity in the thickness direction, the thermal diffusion performance is enhanced and the temperature is made uniform.

In place of the graphite sheet, an aluminum laminate sheet in which resin sheets and aluminum sheets are alternately laminated can be used as the anisotropic heat conducting member 55.
The case 20 includes a resin front case 22 and a rear case 24.
The front case 22 and the rear case 24 are fitted together to form one housing.

A plurality of vent holes 26 (the bottom vent holes are not shown) are formed on the upper and lower surfaces of the front case 22, and a protective panel made of glass for protecting the image display surface 53 of the PDP 50 on the front surface. 30 is disposed.
A plurality of vent holes 26 and 28 are also formed on the upper and lower surfaces of the rear case 24.
The support body 40 is made of, for example, aluminum and includes a pedestal 41 and a pair of support columns 42 extending vertically from both ends of the pedestal 41.

Protruding portions 43, 44, and 45 projecting in the same direction are formed on the support column 42, and these protruding portions 43, 44, and 45 and the chassis 54 are screwed together by screws 3.
Thereby, the support body 40 has a function of supporting the PDP 50 via the chassis 54. In addition, adhesion between the projecting portions 43, 44, 45 of the support 40 and the chassis 54 is enhanced by an elastic member having thermal conductivity such as silicon paste.

By arranging the chassis 54 along the rear main surface of the PDP 50 in this manner, the heat conduction performance in the creeping direction of the rear main surface of the back panel 52 is improved, and the heat distribution in the creeping direction of the PDP 50 is more uniform. And the occurrence of display unevenness can be suppressed.
The dimensional relationship of the chassis assembly 49, the anisotropic heat conducting member 55, and the driver IC 56a and their relative positional relationship are as shown in FIG.

In the present embodiment, the height of the anisotropic heat conductive member 55 is 250 mm, which is the ratio of the thermal conductivity in the thickness direction and the creeping direction of the anisotropic heat conductive member 55, that is, anisotropic. The value varies depending on the thickness of the heat conductive member 55.
In addition, the gap is provided between the adjacent anisotropic heat conducting members 55 in order to positively promote the heat conduction in the vertical direction. This is to prevent conduction as much as possible.
(Evaluation test)
In order to confirm the heat dissipation characteristics of the plasma display device 10 in the present embodiment, the surface temperature of the PDP was measured.

The two objects to be measured are the plasma display device 10 in the present embodiment (hereinafter referred to as “example product”) and the conventional plasma display device (hereinafter referred to as “conventional product”).
About the specification of an Example goods, it is as showing in the description of the structure in this Embodiment, and FIG.

The measurement environment was a room temperature of 25 ° C.
The conventional product is different only in that the driver IC 56a of the embodiment product is directly attached to the chassis 54 without the anisotropic heat conducting member 55 interposed therebetween.
However, since the thermally conductive adhesive 57 is used for the pasting, strictly speaking, as in the case of the driver IC 56a in the present embodiment, the thermal coupling state via the thermally conductive adhesive 57 It has become.
(Measurement point)
As shown in FIG. 3, a reference point facing the center point of the driver IC 56 a is provided on the front main surface of the front panel 51.

For convenience, the measurement point is a position that is advanced from the reference point by a distance L directly above.
More specifically, the measurement points were points at which the distance L was 0, 50, 100, 150, and 200 mm.
As shown in FIG. 4, the temperature at the reference point was 94 ° C., but in the example product, it was 88 ° C., and the surface temperature was reduced by 6 ° C.

This is a result of the heat conducted from the driver IC 56a to the chassis 54 being more widely dispersed in the creeping direction than in the conventional product, which is the only difference in configuration. This is nothing but the difference between the presence or absence of the heat conductive member 55.
In addition, when a visual evaluation test of color reproducibility was performed on the example product and the conventional product, the display unevenness was conspicuous and the design quality was not clear for the conventional product, but the display unevenness was not noticeable for the conventional product. The design quality was cleared.
<Modification 1>
The anisotropic heat conducting member 55 is a graphite sheet having a thickness of 0.5 mm. However, the anisotropic heat conducting member 55 is not a constant thickness as described above, and as shown in FIG. It is desirable to do.

The reason will be described below.
In the vicinity of the far region far from the heat source, the temperature gradient between the anisotropic heat conducting member 55 and the chassis 54 becomes small, and the heat conduction in the anisotropic heat conducting member 55 and the anisotropic heat conducting member 55 and The amount of heat transfer between the chassis 54 is smaller than in the vicinity of the reference point.
Since the thermal resistance in the thickness direction is reduced by making the thickness of the anisotropic heat conducting member 55 near the far region smaller than the thickness near the reference point, the heat conduction in the thickness direction of the anisotropic heat conducting member is reduced. The heat transfer between the anisotropic heat conducting member and the heat radiating plate can be promoted.

  On the other hand, for the heat conduction in the creeping direction in the anisotropic heat conducting member, the ratio of the heat flow path cross-sectional area to the amount of heat moving in the vicinity of the far region is the amount of heat moving in the vicinity of the reference point, that is, in the vicinity of the control element. Even if the thickness of the remote region of the anisotropic heat conducting member is made thinner than the thickness in the vicinity of the control element, the heat transfer in the creeping direction is greatly affected. Absent.

<Modification 2>
In the case of using an aluminum laminate sheet instead of the above graphite sheet, the same concept as described above can be applied.
More specifically, the length of each aluminum sheet to be laminated is shortened stepwise, the ends of each aluminum sheet are aligned at the bottom, and the ends of each aluminum sheet are shifted at the top. Then, an aluminum laminate sheet is formed by laminating via a resin film.

In this way, the thickness of the aluminum laminate sheet near the distant region is thinner than the thickness near the reference point, and the thermal resistance in the thickness direction is reduced. Heat transfer between the heat conductive member and the heat radiating plate can be promoted.
In the present embodiment, the anisotropic heat conductive member 55 only describes that the heat transfer coefficient in the creeping direction is larger than the heat conductivity in the thickness direction, and is in the heat conductivity in the vertical and horizontal directions in the creeping direction. Although not specifically mentioned, it may be possible to set different heat transfer coefficients in the vertical and horizontal directions of the creeping direction.

In this case, for example, the graphite sheet is originally formed by changing the fiber density in both the vertical and horizontal directions, or is formed by equalizing the fiber density in the vertical and horizontal directions at one end and then stretched in either the vertical and horizontal directions. It is possible to reduce the fiber density in one direction.
Thus, by changing the vertical and horizontal fiber density, when the heat transfer coefficient in the vertical and horizontal directions is varied in the creeping direction, when applied as the anisotropic heat conductive member 55 of the present embodiment, That is, it is desirable to set the heat transfer coefficient in the height direction of the PDP 50 to be larger than the heat transfer coefficient in the horizontal direction.

This is because there are a plurality of driver ICs 56a that are heat sources in the lateral direction, and in order to perform efficient heat dissipation, it is necessary to release heat in a direction in which no heat source exists.
In that sense, it is effective to release heat in either the upper or lower direction, but in this embodiment, since the driver IC 56a is located in the vicinity of the lower side of the PDP 50, heat cannot be released downward.

Therefore, the anisotropic heat conducting member 55 is extended upward from the position where the driver IC 56a is disposed to release heat upward.
<Modification 3>
Usually, the inner wall of the resin rear case 24 is close to the rear main surface of the driver IC 56a.

Although the heat-resistant temperature of the rear case 24 depends on the material, it is normally about 100 ° C., so that heat transfer from the driver IC 56a is not preferable.
Therefore, as shown in FIG. 6, a configuration in which the thermal insulation between the driver IC 56 a and the inner wall of the rear case 24 is also used by the anisotropic heat conducting member 55 is conceivable.
More specifically, the driver IC 56a is joined to the chassis 54 via a member 59 having a very low thermal conductivity such as a resinous thin hollow member, and the position thereof is fixed.

Then, the lower end portion of the main surface on the front direction side of the anisotropic heat conductive member 55 that is vertically long is attached to the rear main surface of the driver IC 56a through the heat conductive adhesive 57, and is anisotropic. The front main surface side of the upper end portion of the heat conducting member 55 is attached to the chassis 54 via the heat conductive adhesive 57.
Here, the affixing refers to fixing using a heat conductive adhesive 57 such as silicon paste or ethylene-propylene rubber.

With the above configuration, heat generated in the driver IC 56a is transferred in the creeping direction, particularly in the upward direction via the anisotropic heat conducting member 55, and a sufficient contact area is secured for the heat that has further moved in the upward direction. Heat can be transferred to the chassis 54 after conducting heat conduction in the thickness direction at the upper end.
Moreover, since the thermal conductivity in the thickness direction of the anisotropic heat conductive member 55 is low even at the lower end portion of the rear main surface of the anisotropic heat conductive member 55 close to the inner wall of the rear case 24, the rear Heat transfer to the inner wall of the case 24 is suppressed, and an increase in the temperature of the inner wall of the rear case 24 can be suppressed.

  The present invention is applicable to display devices used for televisions, computer monitors, and the like.

It is a disassembled perspective view of the plasma display apparatus in this Embodiment. It is a back perspective view of PDP in this Embodiment. It is side sectional drawing of PDP in this Embodiment. It is a figure which shows the test result in this Embodiment. It is a figure explaining the modification 1 of the plasma display apparatus in this Embodiment. It is a figure explaining the modification 3 of the plasma display apparatus in this Embodiment.

Explanation of symbols

3 Screw 10 Plasma display device 20 Case 22 Front case 24 Rear case 26 Vent 30 Protection panel 40 Support body 41 Base 42 Post 43 Projection part 49 Chassis assembly 50 PDP
51 Front Panel 52 Rear Panel 53 Image Display Surface 54 Chassis 54 Rear Chassis 55 Anisotropic Thermal Conductive Member 56a Driver IC
56b Flexible cable 57 Thermally conductive adhesive 59 Member

Claims (6)

A display panel in which a plurality of pixels are arranged in a plane, and an image is displayed by controlling the amount of light emitted from each pixel, a heat sink disposed along the back surface of the display panel, and the control A display device having a control element for performing
The control element and a partial region of the main surface of the heat radiating plate are thermally coupled via a sheet-like anisotropic heat conducting member having a thermal conductivity in the creeping direction larger than that in the thickness direction. A display device. When the direction opposite to the emission direction is the anti-emission direction,
The anisotropic heat conducting member is disposed in a partial region of the second main surface among the first main surface existing on the emission direction side of the heat radiating plate and the second main surface existing on the side opposite to the emission direction. ,
The control element is disposed in a partial region of the fourth main surface among the third main surface existing on the emission direction side of the anisotropic heat conducting member and the fourth main surface existing on the side opposite to the emission direction. The display device according to claim 1, wherein:   The anisotropic heat conducting member has a thickness in the partial region of the fourth main surface and a thickness in a remote region of the fourth main surface that is a predetermined distance away from the partial region of the fourth main surface. The display device according to claim 2, wherein a thickness in the remote area is thinner than a thickness in the partial area of the fourth main surface. The display device includes a housing that houses the display panel, the heat sink, and the control element,
The control element is in a space between the main surface of the heat radiating plate and the inner wall of the housing, and any main surface of the control element includes the main surface of the heat radiating plate and the inner wall of the housing. It is arranged at a position to keep a distance,
The anisotropic heat conducting member has at least a first region and a second region;
In the anisotropic heat conducting member, the first region is joined to the main surface of the control element facing the inner wall, and the second region is joined to the partial region of the main surface of the heat sink. The display device according to claim 1, wherein the display device is a display device. A plurality of the control elements are arranged along the edge of the heat sink,
5. The display device according to claim 1, wherein the anisotropic heat conducting member extends in a direction orthogonal to an arrangement direction of the control element. The anisotropic heat conducting member is disposed independently for each control element,
The display device according to claim 5, wherein the adjacent anisotropic heat conducting members are not in contact with each other.

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