Patent Application
20050046618
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for PLASMA DISPLAY MODULE earlier filed in the Korean Intellectual Property Office on 1 Sep. 2003 and there duly assigned Serial No. 2003-60744.
1. Field of the Invention
The present invention relates to a plasma display module, and more particularly, to a structurally improved plasma display module that has a uniform temperature distribution profile and a higher heat transfer efficiency.
2. Description of the Related Art
A plasma display module (PDM) is a flat panel display device for displaying pictures by using a discharge effect. Because of its very good performances and characteristics such as high display capacity, brightness, contrast, latent image, viewing angle, and thin and large screen size, the PDM is considered to be one of the next generation display devices.
Generally, a PDM includes a plasma display panel having a front panel and a rear panel and a chassis base having a circuit board for driving the plasma display panel on the back side the chassis base. Since the PDM uses a discharge effect for displaying pictures on the plasma display panel, a large amount of heat is generated from the plasma display panel. Therefore, a heat dissipating member is disposed between the plasma display panel and the chassis base to conduct the heat to the chassis base.
A heat dissipating member may be formed of a resin compound filled with a heat conductive material. The heat dissipating member formed is directly attached to a surface of the plasma display panel. One problem with such a design is that the heat transfer effect of the heat dissipating member is low because the materials used for manufacturing the heat dissipating member have a low thermal conductivity coefficient of about 1 W/m·K. In such a scenario, when there is a local temperature increase due to a poor heat transfer performance of the plasma display panel in a plane direction (i.e., in a direction parallel to the surface), the light emission efficiency of the phosphor layers in the discharge cells at the locally high temperatures can be reduced. As a result, a bright latent image (i.e., the difference in intensity between different cells) can occur, resulting in an overall brightness reduction. This problem then results in an increase in the discharge strength to achieve a bright image which results in yet more heat generated from the plasma display panel, causing the bright latent image problem to be even more severe. Also, the local temperature increase in the plasma display panel can generate an internal heat stress that can cause a crack of the plasma display panel which is usually made of glass.
The concept of employing a high conductivity heat dissipating member formed of high-orientation graphite to improve the temperature non-uniformity in a plasma display panel to increase the heat transfer efficiency is disclosed in U.S. Pat. No. 5,831,374 to Morita et al. However, the heat transfer performance in Morita '374 is still not sufficient because of pores generated in the heat dissipating member when attaching the heat dissipating member between the plasma display panel and the chassis base. The surface covered by the heat dissipating member is practically about 10˜15% due to the pores. Also, the high conductivity heat dissipating member is hard to attach to and detach from the plasma display panel. Especially, when removing the heat dissipating member, remaining portions of the heat dissipating member must be manually removed from the plasma display panel with a sharp object.
It is therefore an object of the present invention to provide a design for a plasma display module that can provide improved temperature uniformity on a plasma display panel.
It is further an object of the present invention to provide a design for a plasma display panel where the heat dissipating member can easily be attached to and detached from the plasma display panel.
It is also an object of the present invention to provide a design for a plasma display module that has an improved heat transfer performance.
These and other objects may be achieved with a plasma display module (PDM) made up of a plasma display panel (PDP) on which a picture is displayed, a chassis base disposed facing the PDP, a circuit board driving the plasma display panel formed on the chassis base, a heat dissipating member sandwiched in between the PDP and the chassis base, and a plate structure contacting a surface of heat dissipating member and facing the plasma display panel and a surface of heat dissipating member facing the chassis base. The plate structure is preferably made of a material that is strong enough to resist the tensile strength caused by removing the heat dissipating member from the PDP.
Preferably, the heat dissipating member is made out of a material with a very high thermal conductivity, such as high-orientation graphite. This graphite allows for superb thermal conductivity, especially in a planar direction, thus providing better temperature uniformity across the PDP and reducing or eliminating any temperature gradients across the PDP. The plate structure, preferably made out of a metal like aluminum, is disposed between the graphite and the PDP so the graphite does not directly contact the PDP. This plate structure allows for easy attachment and detachment of the graphite to the PDP, improves temperature uniformity across the PDP, and better draws heat away from the PDP. The plate structure can also be formed between the graphite and the chassis base.
The plate structure may be in a form of a flat plate, or instead may be a sealing member that completely surrounds and seals the heat dissipating member. When the plate structure is a sealing member, the heat dissipating member can be a liquid heat transfer material, or a powder type conductive material filled in the plate structure.
The plate structure may include at least a first extension that extends toward outside of the PDM to allow cooling the plasma display panel by air, and in this case, the first extension may include a cooling fin. The plate structure may also include at least a second extension that extends toward the heat dissipating member, in this case, the second extension may be a protrusion formed on a surface of the plate structure contacting the heat dissipating member. Also, the plate structure may include a connection that connects together the PDP side of the plate structure to the chassis base side of the plate structure. The plate structure is preferably made out of a thermally conductive material such as Al, Cu, Ag, and Ni, and a conductive material may also be coated on the plate structure. The heat dissipating member is preferably made of a high-orientation graphite. The plate structure may be attached to the PDP using an adhesive and the plate structure may be attached to the chassis base using an adhesive. The PDP and the chassis base may be combined together using a double sided adhesive placed at the rim of the PDP and the chassis base, and the plate structure may be fixed therebetween or within the rim.
A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:
The chassis base 60 performs as a heat sink for promoting heat transfer from the PDM 5 and from the circuit board 70. Chassis base 60 is preferably made of a material having a superior thermal conductivity, such as aluminum. A circuit board 70 is disposed on a back surface of the chassis base 60 and includes circuit substrates (not illustrated).
The heat dissipating member 40 sandwiched between the PDP 5 and the chassis base 60 as depicted in
The high-orientation graphite can be formed through an annealing process or carbonization of a particular polymer compound after depositing carbon atoms by a chemical vapor deposition method using hydrocarbon gas. The high-orientation graphite obtained by the carbonization of a particular polymer compound has superior thermal conductivity. The particular polymer compound is preferably polyoxadiazoles(POD), polybenzothiazole(PBT), polybenzo-bis-thiazole(PBBT), polyzooxazole(PBO), polybenzo-bis-oxazole(PBBO), polyimides(PI), polyamides(PA), polyphenylene-benzoimidazole(PBI), polyphenylene-benzo-bisimidazole(PPBI), polythiazole(PT), or polyparaphenylene-vinylene(PPV).
The baking process for carbonizing the polymer compound does not require a specific operating condition but the baking is preferably performed above 2,000° C. because the high-orientation graphite can easily solidify below 2,000° C. A highest carbon orientation can be achieved at a temperature of about 3,000° C.
Baking is preferably performed in the presence of an inert gas atmosphere, and preferably performed under a pressure higher than atmospheric pressure to reduce an effect of process gases generated during baking. If necessary, a rolling process can be performed after the baking process.
The high-orientation graphite can be manufactured in a film type or a bulk type, and the heat dissipating member 40 can be made by stacking a plurality of high-orientation graphite films or by a single high-orientation graphite bulk piece.
The high-orientation graphite has elasticity according to the method of manufacturing. The high-orientation graphite preferably has an elasticity to maintain an adherence force, and to overcome the differences of the thermal expansion coefficient between the plasma display panel 5 and the chassis base 60.
The high thermal conductivity heat dissipating member 40 preferably has a thermal conductivity of more than 150 W/m·K, which is much higher than other heat transfer materials which have a thermal conductivity of about 1 W/m·K. Especially, the high thermal conductivity heat dissipating member 40 has an advantage of promoting the thermal conductivity in a plane direction (i.e., x and y directions) due to the anisotropic thermal conductivity of high-orientation graphite.
The heat dissipating member 40 can be manufactured not only of the high-orientation graphite but also of other various materials. For example, when the plate structure 30 is a sealing member that completely surrounds and encapsulates the heat dissipating member 40 as depicted in
The heat dissipating member 40 manufactured of a liquid heat transfer material or a powder type thermal conductivity material has isotropic thermal conductivity characteristics meaning that the thermal conductivity in the plane direction is equal to the thermal conductivity in the thickness direction.
In the PDM 100 configured as above, the heat dissipating member 40 according to an aspect of the present invention includes the plate structure 30 that contacts at least one of the PDP 5 and the chassis base 60.
The plate structure 30 of
The plate structure 30 of
Turning now to
Turning now to
Accordingly, the use of the above plate structure 34 in a PDM can provide advantages in that the bright latent image is reduced or removed, heat stress due to the local temperature increase can be removed, durability of the plasma display panel is increased, and plasma display panel breakage due to cracking can be prevented. Additionally, when a uniform temperature profile over the PDP 5 is achieved, overall heat transfer efficiency of the PDP 5 is increased since heat transfer from the PDP 5 to the chassis base 60 is also uniformly conducted. When attaching a heat dissipating member 40 that has low adhesion ability to the PDP 5 formed of glass, the attaching force can be increased by disposing a plate structure 34 formed of a metal between the PDP 5 and the high conductivity heat dissipating member 40. Moreover, a thermal fatigue of the components that constitute the PDM 400 can be reduced when rapid heat transfer is achieved, thereby increasing the length of the life of the product and also reducing manufacturing cost by eliminating the need for a cooling fan installed in the PDM 400.
The improved attaching method for PDM 400 of
If the plate structure is a sealing member that seals or encapsulates the heat dissipating member 40, the heat dissipating member 40 can be formed in a liquid phase or a gel type, or an appropriately agglomerated powder having high thermal conductivity such as aluminum or carbon powder. The advantages of the above description will now be described based on the following comparison.
[Exemplary Comparison]
Table 1 illustrates empirical test results of radiating performance of different heat dissipating members. The first column of Table 1 illustrates empirical data for a PDM when the heat dissipating member is formed of silicon with a thickness of 1.5 mm and is disposed between the PDP and the chassis base. The second column of Table 1 illustrates empirical data when the heat dissipating member is made of a high thermal conductivity material with a thickness of 1.5 mm and is disposed between the PDP and the chassis base. The third and last column of Table 1 illustrates the empirical test results for a heat dissipating member made of a high thermal conductivity material with a thickness of 1.5 mm where the heat dissipating member also contains an aluminum thin film, where the entire heat dissipating member is disposed between the plasma display panel and the chassis base.
To compare the heat transfer performances for each case, a bright latent image, a bright latent image time, and a surface temperature of the plasma display panel are measured by emitting light in a manner that a predetermined region A of the PDM was lighted, and ten minutes later, the region A and the remaining region B of the PDM were lighted. In the first row, “bright latent image” means the difference in brightness between regions A and B after the ten minutes where only region A is lit followed immediately by 30 seconds of where both regions A and B are lit. As can be reasoned, the better designed PDM has a higher thermal conductivity resulting in a lower difference in image brightness between regions A and B after the 10 minutes followed by the 30 seconds.
The second row is called “bright latent image time” and is the time required after the ten minutes of lighting region A only where both regions A and B are lit and the difference in brightness between these two regions A and B falls to 7 cd/m2. The better designed PDM would have better thermal conductivity characteristics resulting in less time for region A and B to have a difference in brightness of 7 cd/m2.
The last row is the temperature of the PDP at region A after region A only has been emitting light for 10 minutes. A better designed PDM would have improved thermal conductivity resulting in a lower temperature.
As can be seen from Table 1, the high thermal conductivity heat dissipating member of column 2 outperformed the silicon heat dissipating member of column 1 for all three tests. The heat dissipating member having the thin aluminum foil of column 3 outperformed both the silicon heat dissipating member of column 1 and outperformed the high thermal conductivity heat dissipating member of column 2. From these results, the use of the heat dissipating member formed of the high thermal conductivity material and the thin aluminum foil can quickly reduce the temperature gradient formed on the region A because heat transfer in the plane direction is promoted.
Turning now to
When the first extension 36a is included in the design of the plate structure 36, a portion of heat generated in the PDP 5 is directly cooled by air on the plate structure 36 instead of transferring all the heat to the chassis base 60. In other words, since first extension 36a of plate structure 36 extends into cool air, this cool air on the outside of PDM 600 that contacts first extension 36a and cools first extension 36a, thus reducing the temperature of plate member 36. By such a design, the heat transfer efficiency is improved and less heat is transferred to chassis base 60 from PDP 5 than if first extension 36a were not present. With this reduction in temperature on chassis base 60, the circuit board 70 disposed on the backside of the chassis base 60 is less likely to overheat and malfunction.
Turning now to the PDM 700 illustrated in
Turning now to
Turning now to
As with connection 38d of
The PDMs according to the present invention have the following advantages. By using the above designs for plate structures and heat dissipating members and the above materials for the plate structures and heat dissipating members located between the PDP and the chassis base, a more uniform temperature distribution profile can be achieved across of the PDP. When a plate structure is formed of a high thermal conductivity material and is disposed between a plasma display panel and a heat dissipating member, improved heat transfer in a plane direction across the surface of the PDP is better realized. Also, by using high-orientation graphite for a heat dissipating member, temperature transfer in a plane direction is further accelerated.
By reducing temperature gradients along a surface of the PDP, a bright latent image can be reduced or removed. Also, a breakage of the PDP due to thermal stress caused by local heating can be prevented, thereby extending lifetime of the PDM. When a uniform temperature profile is achieved on the PDP, heat transfer to the chassis base is also uniform, thereby increasing overall heat transfer efficiency.
Second, the heat transfer performance is improved by the tight contact between the PDP of the PDM and the heat dissipating member. The tight contact between the PDP that is formed of glass and a heat dissipating member formed of a high thermal conductivity material that has a low contacting force with glass can be achieved by having a plate structure formed of a metal between the glass PDP and the heat dissipating member.
Third, the use of the plate structure makes it easier to attach and detach the heat dissipating member to the PDP, resulting in reduced process loss and increased production yield. When the heat dissipating member needs to be separated from the PDP for reworking or repairing, the heat dissipating member can be removed as one body since the plate structure can resist the plane tensile force that occurs during detaching.
While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-60744 | Sep 2003 | KR | national |
