CN1617661B - Heat spreader for display device - Google Patents

Abstract

A heat spreader (10) for a display device, such as a plasma display panel, a light emitting diode or a liquid crystal display, comprising at least one sheet of compressed particles of exfoliated graphite having a surface area greater than the surface area of that part of the back surface of the display device where a localized region of higher temperature is generated.

Description

Heat sink for display unit

illustrate

We are known to be Timothy Clovesko, US Citizen, 5250 Columbia Ave. Apt. 407 (44070), North Omsted, Ohio; Julian Norley, US Citizen, 17635 Plum Creek Trail, Chagrin Falls, Ohio (44023); A novel and useful "heat sink for display devices" invented by Martin David Smalc, United States Citizen, 5608 Ely Vista Drive (44129), Parma, CA, and JosephPayl Capp, United States Citizen, 10094 Juniper Court (44136), Strongsville, Ohio ".

related application

This application is a co-pending and commonly assigned U.S. Patent entitled "Heat Spreader for Plasma Display Panel" filed October 14, 2003 by Norley, Smalc, Capp, and Clovesko Application Serial No. 10/685,103, and co-pending and commonly assigned, filed May 12, 2004 by Clovesko, Norley, Smalc, and Capp, entitled "Heat Spreader for Emissive Display Devices" Emissive Display Device), the contents of which are hereby incorporated by reference.

technical field

The present invention relates to a heat sink for display devices such as plasma display panels (PDPs), liquid crystal displays (LCDs), light emitting diodes (LEDs), etc., and the unique thermal problems posed by these devices.

Background technique

A plasma display panel is a display device including a plurality of discharge cells, and a display image is constituted by causing a desired discharge cell to emit light by applying a voltage to an electrode discharge cell. A panel device, which is a main part of a plasma display panel, is manufactured by bonding two glass substrates with a plurality of discharge cells interposed therebetween.

In the plasma display panel, discharge cells that cause light to be emitted for image formation generate heat so that each of the discharge cells constitutes a heat source that raises the temperature of the plasma display panel as a whole. Heat generated in the discharge cells is transferred to the glass constituting the substrate, but due to the nature of the glass substrate material, it is difficult to conduct heat in a direction parallel to the panel surface.

In addition, the temperature of the discharge cells that are excited to emit light increases significantly, while the temperature of the discharge cells that are not excited does not increase as much. As a result, the panel surface temperature of the panel of the plasma display panel rises locally in the region where the image is generated. Furthermore, discharge cells activated in the white or brighter color spectrum generate more heat than discharge cells activated in the black or darker color spectrum. Thus, the temperature of the panel surface differs locally depending on the color produced when an image is generated. These local temperature differences accelerate the thermal degradation of the affected discharge cells unless some cooling measures are taken to ameliorate this difference. In addition, when the nature of the image on the display changes, the location of localized heat generation varies with the image.

In addition, due to the high temperature difference between the excited and non-stimulated discharge cells, in fact, the temperature difference between the discharge cells that produce white light and the discharge cells that produce dark light is also high, and the panel components are stressed, resulting in conventional plasma display Boards are prone to cracking and breaking.

When the voltage applied to the electrodes of the discharge cells increases, the brightness of the discharge cells increases, but the heat generated in these cells also increases. Therefore, those cells having a large driving voltage are more prone to thermal degradation and exacerbate the cracking problem of the panel device of the plasma display panel. With regard to heat generation, LEDs have the same problems as PDPs. The same problem exists in display devices other than emissive display devices, such as LCDs, where bright spots can limit the efficiency or lifetime of the device.

SpreaderShield类材料作为这种材料。Morita, Ichiyanagi, Ikeda, Nishiki, Inoue, Komyoji and Kawashima proposed in US Patent No. 5,831,374 a so-called "high orientation graphite film" (high orientation graphite film) as the thermal contact material of the plasma display panel to fill The space between the back of the display board and the heat sink, and the local temperature difference is reduced, however, there is no mention of the use or unique advantages of flexible graphite sheets. In addition, US Patent No. 6,482,520 to Tzeng discloses the use of compressed particle sheets of exfoliated graphite as heat sinks for heat sources such as electronic components (referred to in that patent as thermal interfaces). In fact, eGraf is available from Advanced Energy Technology, Inc. of Lakewood, Ohio

SpreaderShield class material as this material.

Graphite consists of a hexagonal array or network of layered planes of carbon atoms. These hexagonal layered planes of arranged carbon atoms are generally planar and oriented or ordered generally parallel and equidistant from each other. A generally flat, parallel equidistant sheet or layer of carbon atoms, often called a graphene layer or basal plane, bonded or bonded together, the groups of which are arranged into grains. Highly ordered graphite consists of relatively large sized grains that are highly aligned or oriented with respect to each other and has well ordered carbon layers. In other words, highly ordered graphite has a high degree of preferred grain orientation. It should be noted that graphite has an anisotropic structure and thus exhibits or possesses many very directional properties such as thermal and electrical conductivity.

Briefly, graphite is characterized by a carbon layered structure, a structure of stacks or thin layers of carbon atoms held together by weak van der Waals forces. When considering graphite structure, attention is often given to two axes or directions, the "c" axis or direction and the "a" axis or direction. For simplicity, the "c" axis or direction can be assumed to be perpendicular to the carbon layer. The "a" axis or direction is assumed to be a direction parallel to the carbon layer or a direction perpendicular to the "c" direction. Graphite suitable for making flexible graphite sheets has a very high orientation.

As mentioned above, the binding forces holding parallel layers of carbon atoms together are only weak van der Waals forces. Natural graphite can be treated so that the stacked carbon layers or the spacing between the stacks is significantly increased so as to produce a significant expansion in the direction perpendicular to the layers, i.e. the "c" direction, resulting in an expanded graphite structure in which The flake-like nature of the carbon layer is substantially maintained.

In the bonded or integrated sheets of expanded graphite without the use of adhesives, it is possible to form extremely expanded or particularly greatly expanded graphite sheets with a final thickness or "c" dimension of approximately 80 times the original "c" dimension, e.g. Webs, papers, strips, tapes, foils, mats, etc. (commonly referred to as "flexible graphite"). It is believed that due to the mechanical interlocking or agglomeration achieved between a large number of expanded graphite particles, graphite can be expanded to a final thickness or "c" dimension approximately 80 times the original "c" dimension by compression without the use of any bonding material The particles form an integrated flexible sheet.

In addition to flexibility, as mentioned above, it was also found that due to the orientation of the expanded graphite particles due to high pressure and the fact that the graphite layers are substantially parallel to the opposite surfaces of the sheet, heat conduction is highly anisotropic, making the sheet particularly suitable for heat dissipation applications . The produced sheet has excellent flexibility, good strength and high orientation.

Briefly, the manufacturing process of soft, unbonded anisotropic graphite sheets, such as webs, papers, strips, tapes, foils, mats, etc., involves compression or extrusion under predetermined loads and without binders Expanded graphite particles with dimensions in the "c" direction approximately 80 times the original particle size, resulting in a generally flat, flexible integrated graphite sheet. The particles of expanded graphite, usually worm-like or worm-like in shape, once compressed, will remain in the compression set and align with the opposing major surfaces of the flakes. Change the density and thickness of the sheet by controlling the degree of compression. The density of the sheet can range from about 0.04 g/cc to about 2.0 g/c.

Flexible graphite sheets exhibit pronounced anisotropy due to the orientation of the graphite particles parallel to the relatively parallel major surfaces of the flakes, with the degree of anisotropy increasing as sheet compression increases orientation. In an anisotropic sheet under compression, the thickness, ie, the direction perpendicular to the opposing parallel sheet surfaces, includes the "c" direction, and the length and width directions, ie, the directions along or parallel to the opposing major surfaces include the "a" direction, for " For the c" and "a" directions, the thermal or electrical properties of the flakes are very different, and the magnitudes differ by several orders of magnitude.

However, there is a concern in the electronics industry that the common use of graphite-based materials can lead to exfoliation of the graphite particles, with the result that the flakes can interfere mechanically (i.e. in the same way as dust particles) with device operation and function, due to the conductive nature of graphite, graphite flakes Noise electrical interference to emission display devices. While it is believed that these concerns have been shown to be inappropriate, they nonetheless persist.

Furthermore, the use of adhesives to secure graphite heat spreaders to emissive display devices is sometimes disadvantageous. Specifically, when rework is required (i.e. removal and replacement of the heatsink), the adhesive should provide greater structural integrity than the graphite flakes; in this case, it is not always possible to clean the graphite flakes without using scrapers or other tools This is time-consuming and may damage the graphite sheet, the display panel, or both.

Accordingly, there is a need for a lightweight and cost-effective heat sink for an emissive display device, particularly one that prevents graphite particle flakes when used alone, and that can be effectively removed from the device when required. A heat sink is required that equalizes the temperature differential across the area of the device that the heat sink contacts, thereby reducing the thermal stress that would otherwise be experienced on the display panel, and that can be used to reduce hot spots, even if they are The same is true when the position is not fixed.

Contents of the invention

Accordingly, it is an object of the present invention to provide a display device such as a plasma display panel, light emitting diode or liquid crystal display including a heat sink.

Another object of the present invention is to provide a heat sink material that can be used in a display device to improve the temperature difference generated during use.

Yet another object of the present invention is to provide heat sink material for one or more units of a heat source such as a plasma display panel, thereby reducing the temperature between any two locations on the display panel compared to a display panel without the heat sink of the present invention. The difference decreases.

Another object of the present invention is to provide a heat dissipation material that can be applied to a heat source or a group of heat sources such as a plasma display panel or a light emitting diode, and has good thermal contact and bonding between the heat sink and the plasma display panel.

Yet another object of the present invention is to provide a heat spreader material that is isolated to prevent or reduce the possibility of exfoliation of graphite particles.

Yet another object of the present invention is to provide a heat sink that can be adhered to and removed from a heat source with minimal damage to the heat sink or heat source.

Another object of the present invention is to provide a heat sink that can be manufactured in large quantities and in a cost-effective manner.

These and other objects, which will be apparent to those skilled in the art from reading the following description, can be achieved by providing a display device comprising a heat sink comprising at least one sheet of compressed particles from graphite having a surface area of Greater than the surface area of the portion facing the rear surface of the device, such as the discharge cell. The display device may be an emissive display device such as a plasma display panel or a light emitting diode display panel, or another display device such as a liquid crystal display device. More preferably, the surface area of said at least one compressed particle sheet of exfoliated graphite is greater than the surface area of that portion of the plurality of discharge cells facing the rear surface of the device. Advantageously, the heat spreader is a stack comprising a plurality of compressed particle sheets of exfoliated graphite and has a protective coating thereon to prevent the graphite particles from spalling therefrom. In a preferred embodiment, the surface of the heat sink has a veneer, such as aluminum or copper, to further seal the heat sink and facilitate rework.

In a preferred embodiment, the heat sink has an adhesive and a release material thereon, arranged such that the adhesive is sandwiched between the heat sink and the release material. The separation material and the binder are selected such that when the separation material separates at a predetermined speed, it does not cause undesired damage to the heat dissipation material. In practice, the adhesive and release material should produce an average disengagement force of no greater than about 40 grams per centimeter at a separation velocity of about 1 meter per second, preferably no greater than about 10 grams.

In addition, the adhesive preferably achieves a minimum overlap shear bond strength of at least about 125 grams per square centimeter (g/ ^cm2 ), preferably an average overlap shear bond strength of at least about 700 grams per square centimeter. The adhesive should increase the through-thickness thermal resistance of the adhesive/heat dissipating material combination by no more than about 35% compared to the heat dissipating material itself. The thickness of the adhesive should be no greater than about 0.015 millimeters (mm), preferably no greater than about 0.005 mm.

It is to be understood that both the foregoing general description and the following detailed description provide embodiments of the invention, and are intended to provide an overview or framework for understanding, nature and features of the invention as claimed, and the accompanying drawings serve to provide an overview of the invention. It is further understood, and includes and constitutes a part of the specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operations of the invention.

Based on the above objects, the present invention provides a display device comprising a heat sink having two main surfaces, said heat sink comprising at least one sheet of compressed particles of exfoliated graphite, wherein at least one of said heat sinks is The entirety of said major surface is in direct thermal contact with said display device, and wherein said heat sink further comprises a finish layer bonded to one of said at least one compressed particle sheet of said exfoliated graphite on a major surface and disposed between the sheet of compressed particles of the exfoliated graphite and the display.

In other aspects, the finish layer includes metal. The heat spreader includes a laminate including a plurality of compressed particle sheets of the exfoliated graphite. The heat sink includes at least one layer of non-graphite material other than the finish layer. The layer of non-graphite material includes metal, polymer or insulating material. The at least one compressed particle sheet of the exfoliated graphite has edge faces, and at least one of the edge faces is coated with a protective coating sufficient to prevent exfoliation of the graphite particles. The display device includes light emitting diodes. The heat sink also includes an adhesive layer.

The present invention also provides a display device comprising a heat sink having two major surfaces, said heat sink comprising at least one sheet of compressed particles of exfoliated graphite, wherein at least one of said major surfaces of said heat sink All are in direct thermal contact with the display device, wherein at least a portion of the at least one compressed particle sheet of the exfoliated graphite is coated with a protective coating sufficient to prevent exfoliation of the graphite particles.

In other aspects, the protective coating comprises a metal or a thermoplastic material. The thickness of the protective coating is no greater than about 0.025 mm. The protective coating is effective to electrically isolate the coated portion of the at least one compressed particle sheet of the exfoliated graphite. The heat sink also includes an adhesive layer. The display device includes an emissive display device, and the at least one compressed particle sheet of the exfoliated graphite has a surface area greater than a surface area of a portion of a discharge cell facing a backside of the emissive display device. The emissive display device is a plasma display panel. At least one of said major surfaces is coated with a protective coating sufficient to prevent exfoliation of graphite particles. The protective coating comprises metal or thermoplastic material. The thickness of the protective coating is no greater than about 0.025 mm. The protective coating is effective to electrically isolate the coated major surface of the at least one compressed particle sheet of the exfoliated graphite. The display device also includes an adhesive layer disposed between the protective coating and the at least one sheet of compressed particles of the exfoliated graphite. The display device includes an emissive display device, and the at least one compressed particle sheet of the exfoliated graphite has a surface area greater than a surface area of a portion of a discharge cell facing a backside of the emissive display device. The emissive display device is a plasma display panel. The display device also includes an adhesive layer disposed between the protective coating and the display device. The display device includes light emitting diodes.

Description of drawings

Figure 1 is a top perspective view, partly broken away, of one embodiment of a heat sink of the present invention.

Figure 2 is a top perspective view, partly broken away, of another embodiment of a heat sink of the present invention.

Fig. 3 is a side view of another embodiment of the radiator of the present invention.

Figure 4 represents a system for continuous production of resin-infused flexible graphite sheets.

Detailed ways

Graphite is a crystalline form of carbon that includes atoms covalently bound into flat layered planes with weaker bonds between the planes. When obtaining the raw material of the flexible graphite sheet described above, graphite particles, such as natural graphite flakes, are usually treated with an intercalator such as a solution of sulfuric acid and nitric acid, wherein the crystal structure of graphite reacts to form a compound of graphite and intercalator. Hereinafter, the treated graphite particles are referred to as "intercalated graphite particles". Once exposed to high temperature, the intercalant in the graphite will decompose and volatilize, so that the particles embedded in the graphite will expand in the "c" direction, that is, in the direction perpendicular to the graphite crystal plane, to about 80 times the original volume or More. The expanded (or otherwise known as exfoliated) graphite particles are worm-like in appearance and are therefore often referred to as spinoids. The spinoids can be compressed together to form flexible sheets, which, unlike pristine graphite flakes, can be constructed and cut into various shapes with small lateral openings formed by deformation mechanical impact.

Graphite raw materials suitable for flexible sheets in the present invention comprise highly graphitic carbonaceous materials capable of intercalating organic and inorganic acids and halogens, which expand upon exposure to heat. These highly graphitic carbonaceous materials preferably have a degree of graphitization of about 1.0. As used in this description, the term "degree of graphitization" means the value g according to the following formula:

$\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 3.45</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 002</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 0.095</span>}}$

where d(002) is the measured spacing between graphitic layers of carbon in the crystal structure, in angstroms. The spacing d between graphite layers is measured by standard X-ray diffraction techniques. The positions of the diffraction peaks corresponding to the (002), (004) and (006) Miller Indices were measured and standard least squares techniques were used to derive the spacing that minimizes the total error for all these peaks. Highly graphitic carbonaceous materials include, for example, natural graphite from various sources, as well as other carbonaceous materials such as graphite prepared by chemical vapor deposition, pyrolysis of polymers, or crystallization from molten metal solutions. Natural graphite is more preferred.

The graphite raw material of the flexible sheet used in the present invention may contain non-graphite components, as long as the crystal structure of the raw material maintains the required degree of graphitization and can be delaminated. In general, any carbonaceous material whose crystal structure has the desired degree of graphitization and which can be exfoliated is suitable for use in the present invention. This graphite preferably has an ash content of less than twenty percent by weight. Preferably, the graphite employed in the present invention has a purity of at least about 94%. In the most preferred embodiment, the graphite employed is at least about 98% pure.

Shane et al. describe a conventional method for making graphite sheets in US Patent No. 3,404,061, the disclosure of which is incorporated herein by reference. In a representative embodiment of the method of Shane et al., by dispersing the flakes in a solution containing, for example, a mixture of nitric acid and sulfuric acid, preferably about 20 to about 300 parts by weight of intercalation solution (pph) per 100 parts by weight of graphite flakes degree, embedded in natural graphite flakes. Intercalation solutions contain oxidizing and other intercalating agents known in the art. Examples include substances containing oxidants and oxidizing mixtures, such as nitric acid, potassium chlorate, chromic acid, potassium permanganate, potassium chromate, potassium dichromate, perchloric acid, etc.; or mixtures, such as concentrated nitric acid with chlorates, chromium Acid and phosphoric acid, sulfuric acid and nitric acid; or mixtures of strong organic acids, such as trifluoroacetic acid, and strong oxidizing agents dissolved in organic acids. Alternatively, an electric potential can be used to oxidize graphite. Chemicals that can be introduced into graphite crystals using electrolytic oxidation include sulfuric acid as well as other acids.

In a preferred embodiment, the intercalating agent is sulfuric acid, or a mixture solution of sulfuric acid and phosphoric acid, and an oxidizing agent, such as nitric acid, perchloric acid, chromic acid, potassium permanganate, hydrogen peroxide, iodic acid, or periodic acid. Although not preferred, the intercalation solution may contain a metal halide such as ferric chloride, and ferric chloride mixed with sulfuric acid, or a halide such as bromine, a solution of bromine and sulfuric acid, or bromine in an organic solvent.

The amount of intercalation solution is about 20 to about 350 pph, preferably about 40 to about 160 pph. After embedding the flakes, excess solution was drained from the flakes, and the flakes were rinsed with water.

Alternatively, the amount of intercalation solution can be limited to between about 10 and about 40 pph, eliminating the need for a rinse step as taught and described in US Patent No. 4,895,713, the disclosure of which is also incorporated herein by reference.

Particles of graphite flakes treated with an intercalation solution, optionally contacted with an organic reducing agent such as by mixing, may be obtained from alcohols, sugars, aldehydes and esters which react with the surface film of the oxidative intercalation solution at temperatures in the range of 25°C to 125°C Choose an organic reducing agent. Suitable specific organic agents include cetyl alcohol, stearyl alcohol, 1-octanol, 2-octanol, decyl alcohol, 1,10 decanediol, decanal, 1-propanol, 1,3 propylene glycol, 1,2 Ethylene Glycol, Polypropylene Glycol, Glucose, Fructose, Lactose, Sucrose, Potato Starch, Ethylene Glycol Monostearate, Diethylene Glycol Dibenzoate, Propylene Glycol Monostearate, Glycerol Monostearate esters, dimethyl oxalate, diethyl oxalate, methyl formate, ethyl formate, ascorbic acid and lignin-derived compounds such as sodium lignosulfonate. The amount of organic reducing agent is suitably about 0.5 to 4% by weight of graphite flake particles.

Swelling acids applied before, during or immediately after embedding can also provide improved results. These improvements include lowering the delamination temperature and increasing the expansion volume (also called "spindle volume"). The swelling acid herein is preferably an organic material that is sufficiently soluble in the intercalation solution in order to improve swelling. Further defined, such organic materials containing carbon, hydrogen and oxygen may be preferably but not exclusively employed. Carboxylic acids have been found to be particularly effective. Carboxylic acids suitable for swelling acids can be selected from aromatic, aliphatic or cycloaliphatic, branched or branched, saturated or unsaturated monocarboxylic acids, dicarboxylic acids having at least one carbon atom, preferably up to about 15 carbon atoms Acids and polycarboxylic acids which are dissolved in the intercalation solution in an amount effective to produce a measurable improvement in one or more aspects of delamination. Appropriate organic solvents can be used to increase the solubility of organic swelling acids in intercalation solutions.

Representative examples of saturated aliphatic carboxylic acids are acids such as those of the formula H( _CH2 ) _nCOOH , where n is a number from 0 to about 5, including formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid wait. Instead of carboxylic acids, it is also possible to use anhydrides or activated carboxylic acid derivatives such as alkyl esters. Representative examples of alkyl esters are methyl formate and ethyl formate. Sulfuric acid, nitric acid, and other known water-soluble intercalators break down formic acid, eventually into water and carbon dioxide. For this reason, it is advantageous to expose the flakes to formic acid and other sensitive swelling acids prior to immersion in the water-soluble intercalating agent. Representative dicarboxylic acids are aliphatic dicarboxylic acids having 2 to 12 carbon atoms, especially oxalic acid, fumaric acid, malonic acid, maleic acid, succinic acid, glutaric acid, adipic acid, 1 , 5-pentanedicarboxylic acid, 1,6-hexanedioic acid, 1,10-decanedicarboxylic acid, cyclohexane-1-4-dicarboxylic acid and aromatic dicarboxylic acids such as phthalic acid or terephthalic acid Phthalic acid. Representative alkyl esters are dimethyl oxalate and diethyl oxalate. Representative cycloaliphatic acids are cyclohexane carboxylic acid and aromatic carboxylic acids are benzoic acid, naphthoic acid, anthranilic acid, p-aminobenzoic acid, salicylic acid, o-, m- and p-methylbenzene Formic acid, methoxy and ethoxybenzoic acid, acetoacetamidobenzoic acid, acetamidobenzoic acid, phenylacetic acid, and naphthoic acid. Representative hydroxyaromatic acids are hydroxybenzoic acid, 3-hydroxy-1-naphthoic acid, 3-hydroxy-2-naphthoic acid, 4-hydroxy-2-naphthoic acid, 5-hydroxy-1-naphthoic acid, 5-hydroxy -2-naphthoic acid, 6-hydroxy-2-naphthoic acid and 7-hydroxy-2-naphthoic acid. Among the polycarboxylic acids, citric acid is the main one.

The embedding solution contains water, and preferably contains swelling acid in an amount of about 1% to 10%, which is beneficial to enhance delamination. In this embodiment, wherein the expanding acid contacts the graphite flakes either before or after the graphite flakes are immersed in an aqueous intercalation solution. The expanding acid may be mixed with the graphite by suitable means such as a V-blender, generally in an amount of about 0.2% to about 10% by weight of the graphite.

After embedding the graphite flakes, the embedding graphite flakes are mixed with an organic reducing agent, and then the mixture is placed at a temperature ranging from 25° C. to 125° C. to promote the reaction of the reducing agent with the embedding graphite flakes. The heating period is up to about 20 hours, with shorter heating periods, eg, at least about 10 minutes, for higher temperatures in the above ranges. At higher temperatures, periods of half an hour or less, such as on the order of 10 to 25 minutes, may be used.

The above method of intercalation and delamination of graphite flakes is facilitated by pretreatment of the graphite flakes at the graphitization temperature range of about 3000°C and above, and by the inclusion of lubricious additives in the intercalator.

Pretreatment or annealing of graphite flakes results in significantly increased expansion (ie, expanded volume increases to 300% or greater) when the flakes are subsequently subjected to intercalation and delamination. In practice, expansion is expected to be at least 50% greater than a similar treatment without the annealing step. The temperature used in the annealing step should not be significantly lower than 3000°C, since even a 100°C reduction in temperature will result in a significant reduction in expansion.

The annealing of the present invention is performed for a period of time sufficient to cause increased expansion of the flakes upon intercalation and subsequent delamination. Generally, the time required is 1 hour or longer, preferably 1 to 3 hours, and it is more preferred to process under an inert environment. For maximum benefit, the annealed graphite flakes will also be subjected to other treatments known in the art for increasing the degree of expansion - namely intercalation in the presence of organic reducing agents, intercalation acids such as organic acids, and after intercalation Perform a surfactant rinse. Furthermore, for maximum beneficial effect, the embedding step can be repeated.

The annealing step of the present invention is carried out in an induction furnace or other such equipment known in the graphitization art; temperatures in the range of 3000°C are employed here, at the high end of the temperature range encountered during graphitization.

Since it has been observed that spinites made with pre-embedded annealed graphite can sometimes "clump" together negatively impacting domain weight uniformity, it is highly desirable to facilitate the formation of "no-flow" spinoids additives. Lubricant additives are added to the embedding solution to facilitate the movement of the spirals on the benches of compression equipment (such as the benches of calendering stations traditionally used to compress (or "calend") graphite spirals into flexible graphite sheets) a more even distribution. The resulting flakes have higher areal weight uniformity and greater tensile strength, even when the raw graphite particles are smaller than those conventionally used. Lubricity additives are preferably long chain hydrocarbons. Organic compounds with long chain hydrocarbon groups, even where other functional groups are present, can also be used.

More preferably, the lubricious additive is an oil, most preferably mineral oil, especially given that mineral oil is less prone to rancidity and odor, an important consideration for long-term storage. Note that some of the swelling acids described above also meet the definition of lubricious additives. When using these materials as swelling acids, it is not necessary to include lubricity additives alone in the insert.

The lubricity additive is present in the insert in an amount of at least about 1.4 pph, preferably at least about 1.8 pph. Although the upper limit for lubricant content is less critical than the lower limit, it appears that inclusion of lubricious additives above about 4 pph confers no significant additional benefit.

Such treated graphite particles are sometimes referred to as "intercalated graphite particles". Upon exposure to high temperatures, for example at least about 160°C, especially about 700°C to 1000°C and higher, the intercalated graphite particles pass through a The zigzag expands to about 80 to 1000 times its original volume or more. The expanded or delaminated graphite particles are worm-shaped in appearance and are therefore often referred to as spinoids. The spinoids can be molded together into flexible sheets with small transverse openings that differ from the original graphite sheet, and the separated material can be formed and cut into various shapes as described below.

Alternatively, the flexible graphite sheets of the present invention may utilize reground flexible graphite sheets rather than freshly expanded spinoids. The flakes may be newly formed, recycled, scrap, or any other suitable source.

And the process of the present invention can use a mixture of virgin material and recycled material or all recycled material.

The raw material for the recycled material may be a sheet or a trimmed portion of a sheet that has been molded as described above, or a sheet compressed by a pre-calender roll. In addition, the raw material may be a sheet or a trimmed portion of a sheet that has been infused with resin but not yet cured, or a sheet or trimmed portion of a sheet that has been infused with resin and cured. The raw material can also be recycled flexible graphite PEM fuel cell components such as flow field plates or electrodes. Each of a variety of graphite raw materials can be used, or blended with natural graphite flakes.

Once the raw material of the flexible graphite flakes is obtained, it can be pulverized by known processes or devices such as jet milling, air milling, mixers, etc. to produce particles. Preferably, the majority of the particles will have a diameter in excess of 20 U.S. mesh; more preferably a substantial fraction (greater than about 20%, more preferably greater than about 50%) will not exceed 80 U.S. mesh. Most preferably, the particles have a particle size of no greater than about 20 mesh.

The size of the ground particles can be chosen such that the balance of machinability and ease of formability of the graphite particles is balanced with the desired thermal properties. Thus, smaller particles will result in graphite articles that are easier to process and/or form, while larger particles will result in graphite articles with higher anisotropy and thus higher in-plane electrical and thermal conductivity.

Once the raw material is ground, any resin is removed if necessary and then re-expanded. Re-expansion can be performed using the embedding and exfoliation process described above and in US Patent 3,404,061 to Shane et al. and US Patent 4,895,713 to Greinke et al.

Typically, the particles are delaminated after embedding by heating the intercalated particles in a furnace. During this delamination step, intercalated natural graphite flakes can be added to the regenerated intercalated particles. Preferably, during the re-expansion step, the particles expand to have a certain volume in the range of at least about 100 cc/g to about 350 cc/g or greater. Finally, after the re-expansion step, the re-expanded particles are compressed into flexible sheets, as described above.

Flexible graphite and foils are condensed to have good processing strength and are compressed, for example by compression molding, to a thickness of about 0.025 mm to 3.75 mm, typically with a density of about 0.1 to 1.5 grams per cubic centimeter (g/cc). Although not always preferred, it is sometimes advantageous to treat the flexible graphite sheet with a resin, and after curing, the adsorbed resin enhances the moisture resistance and processing strength of the flexible graphite sheet i.e. hardness, as well as "fixes" the morphology of the sheet . When used, a suitable resin content is preferably at least about 5% by weight, more preferably from about 10% to 35% by weight, suitably up to 60% by weight. Resins found to be particularly useful in the practice of this invention include acrylic, epoxy and phenolic based resin systems, or mixtures thereof. Suitable epoxy resin systems include diglycidyl ether or bisphenol A (DGEBA) based resins and other multifunctional resin systems; phenolic resins that may be employed include resoles and novolacs.

Referring to FIG. 4 , a system for continuous manufacture of resin-embedded flexible graphite sheets is disclosed, wherein a reactor 104 is filled with graphite flakes and a liquid intercalator. More specifically, container 101 is used to contain a liquid intercalator. The container 101 is suitably made of stainless steel and is continuously replenished with liquid intercalation agent through a conduit 106 . Vessel 102 contains graphite flakes, which are introduced into reactor 104 together with the intercalant from vessel 101 . The respective speeds at which the intercalant and graphite flakes are fed into the reactor 4 are controlled, such as via valves 108 , 107 . Graphite flakes in vessel 102 can be continuously replenished via conduit 109 . Additives, such as intercalation enhancers such as traces of acid, and organic chemicals may be added through a dispenser 110 metered through a valve 111 at the output of the dispenser 110 .

The resulting embedded graphite particles are wetted and acid coated and directed (such as through conduit 112) to a flush tank 114 where the particles are rinsed, preferably with water entering and exiting the flush tank 114 at reference numerals 116, 118 . The rinsed embedded graphite flakes then pass to a drying chamber 122 such as via conduit 120 . Additives such as buffers, antioxidants, decontamination chemicals can be added from container 119 to the liquid flow of embedded graphite flakes in order to modify the surface chemistry of delamination during expansion and to utilize and modify gaseous emissions causing expansion.

The embedded graphite flakes are dried in dryer 122, preferably at a temperature of about 75°C to about 150°C, generally avoiding any swelling or expansion of the embedded graphite flakes. After drying, the embedded graphite flakes are fed continuously into collection barrel 124 as a fluid stream into flame 200 by, for example, using conduit 126 , and then as fluid stream into flame 200 in expansion vessel 128 as indicated by reference numeral 2 . Additives such as soaked quartz glass fibers, carbon and graphite fibers, ceramic fiber particles composed of zirconia, boron nitride, corundum and magnesia fibers, naturally occurring mineral fibers such as calcium metasilicate fibers, calcium aluminum silicate fibers, Alumina fibers or the like may be added from vessel 129 to the stream of embedded graphite particles propelled by entrainment without introduction of reactive gas at 127 .

The embedded graphite particles 2, after passing through the flame 200 in the expansion chamber 201, expand more than 80 times in the "c" direction and assume a "worm-like" expanded form 5; The additives mixed with the stream are substantially unaffected when passing through the flame 200. The expanded graphite particles 5 may pass through a gravity separator 130 , wherein heavier ash-like natural mineral particles are separated from the expanded graphite particles, and then enter a wider truncated funnel 132 . Separator 130 can be bypassed when not needed.

The expanded or exfoliated graphite particles 5 are in free fall along with any additives in the hopper 132 and are dispersed at will, for example through the trough 134 and into the compression station 136 . The compression station 136 comprises separate opposing, convergingly moving porous belts 157 , 158 to receive the delaminated expanded graphite particles 5 . As the space between the oppositely moving belts 157, 158 decreases, the delaminated expanded graphite particles are compressed into a flexible graphite mat shown at reference numeral 148, the thickness of which is from, for example, about 25.4 to 0.075 mm, especially from about 25.4 mm. to 2.5 mm, and the density is from about 0.08 to about 2.0 g/cm ³ . Gas emanating from the expansion chamber 201 and funnel 132 may be removed and cleaned using a gas scrubber 149 .

The pad 148 is passed through the container 150 and injected with liquid resin from the spray nozzle 138, the resin is preferably "pulled through the pad" using a vacuum chamber 139, and the resin is then preferably dried in a drier 160, reducing the viscosity of the resin, and thereafter in the calender Infused resin pad 143 is thickened into rolled flexible graphite sheet 147 at 170 . Gases and fumes from vessel 150 and dryer 160 are preferably collected and cleaned in scrubber 165 .

After thickening, the resin in the flexible graphite sheet 147 is at least partially cured in the curing oven 180 . Alternatively, partial curing may be performed prior to thickening, although curing after thickening is preferred.

However, in one embodiment of the invention, the flexible graphite sheet is not embedded in resin, in which case container 150, dryer 160 and curing oven 180 may be omitted.

Plasma display panels are now manufactured with dimensions above 1 meter (measured corner to corner). Consequently, the heat sink plate used to cool and improve the hot spot effect on such display panels also needs to be relatively large, on the order of about 270 mm by about 500 microns, or on the order of about 800 microns by 500 microns or larger. In the plasma display panel, as described above, there are thousands of cells each containing plasma gas. When a voltage is applied to each cell, the plasma gas reacts with the phosphors in each cell to produce colored light. Plasma displays can be very hot due to the considerable energy required to ionize the gas to create the plasma. Furthermore, depending on the color in a particular area of the display panel, hot spots are created on the screen, which can lead to premature failure of the phosphors, shorten display life, and create thermal stress on the display panel itself. Thus, heat sinks are needed to reduce the effects of these hot spots.

Sheets of compressed particles of exfoliated graphite, especially stacks of sheets of compressed particles of exfoliated graphite, have been found to be particularly useful as heat sinks for displays, such as plasma displays. More specifically, one or more sheets of exfoliated graphite compressed particles, referred to herein as flexible graphite sheets, are placed in thermal contact with the backside of the plasma display panel such that the flexible graphite sheets cover multiple heat sources in the display panel ( That is, the discharge unit). In other words, the surface area of the flexible graphite sheet is larger than the surface area of the discharge cells on the backside of the plasma display panel; in fact, the surface area of the flexible graphite sheet is larger than the surface area of the discharge cells on the backside of the plasma display panel. Thus, due to the nature of the superior graphite material forming the heat sink of the present invention, it can dissipate heat from hot spots created in different locations of the plasma display panel when the image displayed by the display panel changes.

Due to the nature of the flexible graphite sheet material, which is more compliant than other materials, and even other forms of graphite, the contact resistance between the heat sink and the plasma display panel is reduced and compared to using prior art heat sinks. Better thermal contact is obtained than when the same pressure is applied.

The flexible graphite sheet heat spreader of the present invention is used to reduce the thermal difference (ie ΔT) between multiple locations on the display. In other words, by using the flexible graphite heat sink of the present invention, it is possible to reduce the difference between hot spots on the plasma display panel, such as the position where a white image is produced, and the position where a darker image is produced, compared to ΔT when there is no flexible graphite sheet. temperature difference between adjacent locations. Thus, the thermal stress on the plasma display panel under other circumstances is reduced, and the life and utility of the display panel are prolonged. Furthermore, due to the reduction of hot spots (ie heat peaks), the entire part can be operated at higher temperatures resulting in improved images.

In fact, bonding the heat sink to the plasma display panel with a layer of adhesive thereon, especially during the assembly of the plasma display panel, is advantageous for the graphite heat sink to be manufactured. It is therefore necessary to cover the adhesive with a release liner, and sandwiching the adhesive between the release liner and the graphite sheet allows storage and transport of the graphite heat sink prior to bonding to the plasma display panel.

The use of an adhesive-coated graphite sheet (or stack of sheets) with a release liner requires certain requirements to be met when used in a large scale plasma display panel manufacturing process. Specifically, the release liner must be able to be removed from the sheet at high speed without delamination of the graphite. Delamination occurs when the release liner, when removed, actually releases the adhesive and some of the graphite flakes from the flakes, resulting in waste of graphite, damage to the flakes themselves, and the bonding required for the flakes to bond to the plasma display panel The agent is reduced, and the appearance is unsightly and unsightly.

Nonetheless, since the adhesive and release liner must be selected such that the adhesive/graphite sheet can be separated from the release liner without delamination of the graphite, the adhesive must be strong enough to hold the graphite sheet in the plasma display. At the appropriate position on the board, while the display board assumes any of a variety of orientations to ensure good thermal contact between the heat sink and the display board.

Furthermore, the adhesive must not cause a significant degradation of the thermal properties of the heat sink. In other words, an adhesive applied in a thick layer may affect the thermal properties of the heat sink because the adhesive interferes with the conduction of heat from the plasma display panel or other display device to the heat sink.

Thus, the adhesive and release liner combination must be balanced such that they yield no more than about 40 g/cm at a separation velocity of about 1 m/s, as measured on, for example, a ChemInstruments HSR-1000 High Speed Separation Detector, A breakaway load of about 20 g/cm, most preferably about 10 g/cm is preferred. For example, if it is required to remove the release liner at a speed of about 1 m/s so as to comply with the large-scale manufacturing requirements of display devices such as plasma display panels, the average detachment load of the release liner should not be greater than about 40 g/cm, preferably about 20 g /cm, more preferably about 10 g/cm, so that graphite delamination will not be caused when the separation liner is removed at this separation speed. To accomplish this, the thickness of the adhesive is preferably no greater than about 0.015 mm, more preferably no greater than about 0.005 mm.

Another factor that needs to be considered in balance is the bonding strength of the above-mentioned adhesive, which must be sufficient to maintain the heat sink in place on the plasma display panel during the plasma display panel manufacturing process to ensure that the heat sink is compatible with the plasma display. Good thermal contact between boards. To achieve the desired bond, the adhesive must have a minimum overlap shear bond strength of at least about 125 g/ ^cm2 , more preferably an average overlap shear bond strength as measured on a ChemInstruments TT-1000 tensile tester, for example is at least about 700 g/cm ² .

Through all of the above, the adhesive should not substantially affect the thermal properties of the heat sink. This means that the presence of the adhesive will not cause the thermal resistance in the thickness direction of the heat sink to increase by more than 100% compared to the heat dissipation material itself without the adhesive. In fact, in a more preferred embodiment, the adhesive does not increase the thermal resistance by more than about 35% compared to the heat sink material without the adhesive. Therefore, the adhesive must meet the breakaway load requirement and the average overlap shear bond strength requirement while being sufficiently thin to avoid undesirably extreme increases in thermal resistance. In order to meet these requirements, the thickness of the adhesive should not exceed about 0.015 mm, preferably not more than 0.005 mm.

When the heat sink is applied to a display device such as a plasma display panel in a high-volume manufacturing process, in order to achieve the above balance required, the heat sink is not more than about 2.0 mm thick and has a density between about 1.6 to about 1.9 grams per cubic centimeter A compressed particle sheet or stack of sheets of exfoliated graphite, a commercially available pressure sensitive acrylic adhesive of the desired thickness, combined with a release liner made of silicone coated Kraft paper, such as available from Techicote Inc. L2 or L4 release liners, available from the SilTech Division, can achieve the desired results. Accordingly, there is provided a heat sink composite comprising a heat sink material, such as a compressed particle sheet or stack of sheets of exfoliated graphite, with an adhesive thereon of a thickness such that the thermal properties of the heat sink material are substantially will be damaged, the separation layer enables the adhesive to be disposed between the heat dissipation material and the separation material. Then, in use, the release material can be removed from the heat sink/adhesive combination, and the heat dissipation material/adhesive combination is then applied to a display device such as a plasma display panel, so that the adhesive bonds the heat dissipation material to the Plasma display panel. In addition, at least one heat spreader/adhesive combination is applied to each of the plurality of plasma display panels when manufacturing the plurality of plasma display panels.

When a flexible graphite laminate is used as the heat sink of the present invention, other laminates may also be included to improve the mechanical or thermal properties of the laminate. For example, stacks of thermally conductive metals like aluminum or copper can be interposed between layers of flexible graphite in order to increase the heat dissipation of the stack without sacrificing the low contact resistance exhibited by graphite; other materials such as polymeric objects to enhance or increase the strength of the laminate. Additionally, the graphite material, whether monolithic or stacked, may be provided with a thin plastic sheet or, in an alternative, with a backing layer of a thin dry resin coating to improve handling of the material and/or The damage to the thin sheet during transportation or application to the display device is reduced without impairing the heat dissipation capability of the heat sink of the present invention. Layers of insulating material may also be employed.

Additionally, the surface of the heat sink intended to abut the display device may have a material finish to improve the thermal and/or rework properties of the heat sink of the present invention. Metallic aluminum or copper is preferred, with aluminum being most preferred. While there may be some heat loss in terms of greater contact resistance (since the compliant graphite surface is not in contact with the device surface when a veneer is used), this is compensated by the thermal isotropy of the metal lining. Not only that, however, since the finish is bonded to the surface of the device, it facilitates removal of the heat sink of the present invention for rework or other purposes, since the metal finish is structurally stronger than the bond, allowing quick and non-damaging removal of the heat sink from the display device. Surface removal of heatsinks.

As shown in Figure 1, the flexible graphite sheet or laminate, referenced 10, used in the heat sink of the present invention, once formed, can be cut into desired shapes, in most cases rectangular. The heat sink 10 has two main surfaces 12 and 14, and at least one edge (or side) face, and typically four edge faces 16a, 16b, 16c, 16d if the heat sink 10 is rectangular (obviously, when the heat sink 10 When cut into shapes that are not square, such as circles or more complex shapes, will have a different number of edge faces).

Referring now to FIGS. 1-3, heat spreader 10 advantageously includes a protective coating 20 to prevent graphite particles from spalling from the flexible graphite sheets or laminates making up heat spreader 10, which would otherwise detach. The protective coating 20 also facilitates the effective isolation of the heat sink 10 from electrical interference caused by the inclusion of conductive materials (graphite) in electronic devices. The protective coating 20 may comprise any suitable material sufficient to prevent spalling of the graphite material and/or electrically isolate the graphite, such as thermoplastic materials such as polyethylene, polyester or polyimide, paraffin and/or varnish materials. Indeed, when grounding is required, the protective coating 20 may comprise a metal such as aluminum, as opposed to electrical isolation.

Advantageously, the protective coating 20 should preferably be at least about 0.001 mm thick in order to achieve the desired sheet resistance and/or electrical isolation. Although there is no true maximum thickness for the protective coating 20, the protective coating 20 should be no more than about 0.025 mm thick, preferably no more than about 0.005 mm thick in order to function effectively.

When the heat sink 10 is applied to a display device such as a plasma display panel, the main surface 12 of the heat sink 10 is a surface that effectively contacts the display panel. Also, in many applications, the contact between major surface 12 and the display panel serves to "seal" major surface 12 against graphite spalling, thereby eliminating the need to coat major surface 12 with protective coating 20 . Likewise, it is not necessary to electrically isolate major surface 12 if major surface 14 is electrically isolated from the rest of the electronic device on which heat sink 10 is provided. However, for handling or other considerations, in some embodiments, a protective coating 20 may be applied to both major surfaces 12 and 14 of the heat sink 10, the heat sink 10 being used on the graphite sheet and the major surface 12. Between any adhesives, the adhesive is used to bond the heat sink 10 to a plasma display panel (not shown).

The protective coating 20 can be provided to the heat sink 10 in a number of different ways. For example, once the flexible graphite sheet or stack is cut to the specified size and shape to form the heat sink 10, the material used to form the protective coating 20 can be applied to the individual heat sinks 10 so as to flow completely to the major surface 14 and edge faces, etc., and extend beyond the sides, etc., to form a protective sheet-like border around the heat sink 10, as shown in FIG. 1 . To this end, the protective coating 20 can be applied by various application methods well known to those skilled in the art, such as spraying, rolling and thermal lamination.

In another embodiment, as shown in FIG. 2, a protective coating 20 may be applied to the heat sink 10 to cover one or more of the edge faces 16a, 16b, 16c, 16d (eg, depending on which edge surface exposed, potentially subject to spalling and/or electrical interference). The protective coating 20 can be applied by mechanical mapping and lamination thereto.

In yet another embodiment of the invention, and as shown in FIG. 3 , a protective coating 20 is applied to the heat sink 10 such that only the major surface 14 is coated. A particularly preferred method of manufacturing the heat sink 10 of this embodiment is to coat the flexible graphite sheet or laminate with a protective coating 20, such as by roll coating, lamination with an adhesive, or thermal lamination, and then apply the flexible graphite sheet Or the laminate is cut into the desired shape of the heat sink 10 . In this way, manufacturing efficiency is maximized and waste of protective coating 20 is minimized during the manufacturing process.

聚脂材料和Kapton聚酰亚胺材料(两种都可以从Wilmington Delaware的E.I.du Pont de Nemours and Company购得)，粘合剂层30可以涂覆在散热器10与保护涂层20之间，如图3中所示。适当的粘合剂是便于将保护涂层20粘接到散热器10的粘合剂，如丙烯酸或乳胶粘合剂。粘合剂层30可以涂覆到散热器10与保护涂层20的任何一个上或者涂覆到两者之上。有利的是，粘合剂层30尽可能的薄，同时保护涂层20与散热器10之间依然保持粘接。最好，粘合剂层30的厚度不大于大约0.015mm。In general, the coating process bonds protective coating 20 to heat sink 10 with sufficient strength for most applications. However, if desired, or for a relatively non-stick protective coating 20 such as Mylar

Polyester material and Kapton polyimide material (both can be purchased from EI du Pont de Nemours and Company of Wilmington Delaware), adhesive layer 30 can be coated between heat sink 10 and protective coating 20, as shown in Figure 3. A suitable adhesive is one that facilitates bonding the protective coating 20 to the heat sink 10, such as an acrylic or latex adhesive. Adhesive layer 30 may be applied to either or both of heat sink 10 and protective coating 20 . Advantageously, the adhesive layer 30 is as thin as possible while still maintaining the bond between the protective coating 20 and the heat sink 10 . Preferably, adhesive layer 30 has a thickness no greater than about 0.015 mm.

Furthermore, in another embodiment, the heat sink 10 may include a finish layer interposed between the surface 12 of the heat sink 10 and the surface of the display device. As noted above, the finish layer is preferably a metal, such as aluminum, and may be bonded to surface 12 of heat sink 10 using an adhesive layer applied between surface 12 and the finish layer, as shown in FIG. 1 . Suitable adhesives are acrylic or latex adhesives and may be applied to either or both of the heat sink surface 12 and the finish layer. Of course, the adhesive is applied as thinly as possible while still maintaining a bond between the finish and surface 12, preferably no greater than about 0.015 mm in thickness.

Furthermore, as shown in FIG. 1 , a finish layer may be used together with a protective coating 20 to seal the graphite heat sink 10 between the finish layer and the protective coating 20 . Specifically, if the finish layer extends beyond the edge or the like of the heat sink 10, a protective coating may be applied around the heat sink 10 and the finish layer. Alternatively, a material such as aluminum tape may be used to seal the edge between the finish layer and the protective coating 20, or the like.

Although the application has been described with respect to the heat sink applied to plasma display panels, it can be known that the method and heat sink of the present invention can be applied to other emissive display device heat sources, or heat source concentrators (related functions are equivalent to constituting a plasma display The collection of individual discharge cells of the panel), such as light-emitting diodes, and other display devices that generate localized high-temperature regions or hot spots, such as liquid crystal displays.

The following example illustrates the operation and effect of one embodiment of the present invention, but is for illustration only and does not limit the scope and breadth of the claimed invention.

example 1

Thermal properties of a Panasonic plasma TV (model: TH42PA20) using an acrylic heat sink attached to the back side of the plasma display panel were analyzed under different screen conditions as described below. Produces white and black patterns on the display and uses an infrared camera to measure the screen surface temperature. The background is black in all cases. The pattern consisted of: 1) three white lines evenly spaced horizontally across the screen (23.9% screen illuminance) and 2) a 4x3 array of evenly spaced white dots (4% screen illuminance). After testing the device with a conventional acrylic heat sink, the acrylic heat sink was removed and replaced with a flexible graphite heat sink with a thickness of 1.4 mm and an in-plane thermal conductivity of approximately 260 W/m°K. The plasma display was then tested again under the same conditions as above, and the results are listed in Table 1.

Table 1

pattern heat sink Tmax White Pattern T Range environment white line pattern Acrylic 49.3 30 24.1 white line pattern   Flexible Graphite Sheet 48.6 34.4 23.5 White dot array pattern Acrylic 51.8 30.4 24.3 White dot array pattern   Flexible Graphite Sheet 39.3 28.3 23.4

Example 2:

The thermal properties of an NEC plasma display (model: Plasmasync 42” 42XM2 HD) using an aluminum/silicone heat sink attached to the backside of the plasma display panel were analyzed under the different screen conditions described below. White and black are produced on the display pattern, and measured the screen surface temperature using an infrared camera. The background was black in all cases. The pattern consisted of: 1) three white lines evenly spaced horizontally across the screen (23.9% screen illuminance) and 2) evenly spaced white dots 4x3 array (4% screen illumination). After testing a device with a conventional aluminum/silicone heatsink, the aluminum/silicone heatsink was removed and replaced with a thickness of 1.4mm and an in-plane thermal conductivity of approximately 260W/m °K of the flexible graphite heat sink. Then the plasma display was detected again under the same conditions as above, and the results are listed in Table 2.

Table 2

pattern heat sink Tmax White Pattern T Range environment white line pattern aluminum/silicone 61.4 32.9 25.2

white line pattern   Flexible Graphite Sheet 55.1 33.9 24.9

These examples illustrate the benefits of using flexible graphite heat sinks over conventional heat sink technology in terms of maximum observed temperature (Tmax) and temperature range (Trange).

All cited patents and publications mentioned in this application are hereby incorporated by reference.

The invention as described can obviously be varied in many ways. Such changes are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as are obvious to one skilled in the art are intended to be embraced within the scope of the appended claims.

Claims (24)

1. display unit that comprises radiator; Said radiator has two first type surfaces; Said radiator comprises at least one compressed particles sheet of leafing graphite; Whole and the said display unit direct heat of the said first type surface of at least one of wherein said radiator contacts; And the said first type surface of at least one of wherein said radiator also comprises the finish coat on the said first type surface that is attached to said radiator, and said finish coat is predetermined to be abutted said display unit and be arranged between the said compressed particles sheet and said display unit of said leafing graphite, with the thermal property that improves said radiator and/or reprocess character.

2. display unit as claimed in claim 1 is characterized in that said finish coat comprises metal.

3. display unit as claimed in claim 1 is characterized in that said radiator comprises laminate, and said laminate comprises a plurality of compressed particles sheets of said leafing graphite.

4. display unit as claimed in claim 1 is characterized in that, said radiator comprises that one deck at least places the non-graphite material between the said leafing graphite except said finish coat.

5. display unit as claimed in claim 4 is characterized in that, said non-graphite material layer comprises metal, polymer or insulating material.

6. display unit as claimed in claim 1; It is characterized in that; It comprises emission display, and the surface area of said at least one compressed particles sheet of said leafing graphite is greater than that part of surface area of the discharge cell at the back side of facing said emission display.

7. display unit as claimed in claim 6 is characterized in that said emission display is a plasma display panel.

8. display unit as claimed in claim 1 is characterized in that, at least one said first type surface is coated with protective finish, is enough to prevent that graphite particle from peeling off.

9. display unit as claimed in claim 8 is characterized in that said protective finish comprises metal or thermoplastic.

10. display unit as claimed in claim 9 is characterized in that the thickness of said protective finish is not more than 0.025mm.

11. display unit as claimed in claim 8 is characterized in that, said protective finish is effectively isolated the first type surface and the environment electricity of the coating of said at least one compressed particles sheet of said leafing graphite.

12. display unit as claimed in claim 1 is characterized in that, said at least one compressed particles sheet of said leafing graphite has edge surface, and at least one said edge surface is coated with and is enough to the protective finish that prevents that graphite particle from peeling off.

13. display unit as claimed in claim 8 is characterized in that, it also comprises the adhesive phase between said at least one the compressed particles sheet that places said protective finish and said leafing graphite.

14. display unit as claimed in claim 8 is characterized in that, it also comprises the adhesive phase that places between said protective finish and the said display unit.

15. display unit as claimed in claim 1 is characterized in that, said display unit comprises light-emitting diode.

16. display unit as claimed in claim 1 is characterized in that, said radiator also comprises position adhesive phase on it.

17. display unit that comprises radiator; Said radiator has two first type surfaces; Said radiator comprises at least one compressed particles sheet of leafing graphite; Whole and the said display unit direct heat of the said first type surface of at least one of wherein said radiator contacts, and at least a portion of at least one compressed particles sheet of wherein said leafing graphite is coated with protective finish, is enough to prevent that graphite particle from peeling off.

18. display unit as claimed in claim 17 is characterized in that, said protective finish comprises metal or thermoplastic.

19. display unit as claimed in claim 17 is characterized in that, the thickness of said protective finish is not more than 0.025mm.

20. display unit as claimed in claim 17 is characterized in that, said protective finish is effectively isolated the part and the environment electricity of the coating of said at least one compressed particles sheet of said leafing graphite.

21. display unit as claimed in claim 17 is characterized in that, said radiator also comprises position adhesive phase on it.

22. display unit as claimed in claim 17; It is characterized in that; It comprises emission display, and the surface area of said at least one compressed particles sheet of said leafing graphite is greater than that part of surface area of the discharge cell at the back side of facing said emission display.

23. display unit as claimed in claim 22 is characterized in that, said emission display is a plasma display panel.

24. display unit as claimed in claim 17 is characterized in that, said display unit comprises light-emitting diode.

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