KR20050036787A - Heat spreader for display device - Google Patents

Abstract

The heat spreader 10 for a display device, such as a plasma display panel (PDP), a light emitting diode (LED) or a liquid crystal display (LCD), has a larger surface area than the surface area of the back portion of the display device where a hotter localized area is created. One or more sheets of compressed particles of exfoliated graphite having regions.

Description

Heat spreader for display devices {HEAT SPREADER FOR DISPLAY DEVICE}

United States Timothy Clovesco of 44200 Ohio, North Olmsted, Columbia Road 5250 Apartment 407, USA; Julian Nolay, an American national, living at Chagrin Greens, Plum Creek Trail 17635, 44023, Ohio; Martin David Smarek, an American national, residing in El Vista Drive 5608, 44129 Ohio, USA; And Joseph Foul Cap, a US national who lives in 44136 Ohio, Strongsville, and Juniper Court 10094, invented a new and useful "heat spreader for display devices."

This application was filed on October 14, 2003, in the name of Nolay, Smarek, Cap and Clovisco, entitled “Thermal Diffuser for Plasma Display Panels” and is commonly assigned and currently pending US Patent Application No. 10 / 685,103 US Patent Application No. 10, filed May 12, 2004, under the names Clovesco, Nolay, Smarek and Cap, entitled “Thermal Diffuser for Light-Emitting Display Devices”; / 844,537, which is part of a series of applications.

The present invention relates to display devices such as plasma display panels (PDPs), liquid crystal displays (LCDs), light emitting diodes (LEDs), and the like and to heat spreaders useful for thermal problems caused by such devices.

A plasma display panel is a display device composed of a plurality of discharge cells, and configured to display an image by supplying a voltage across an electrode discharge cell, thereby causing a desired discharge cell to emit light. The panel unit, which is the main part of the plasma display panel, is manufactured by joining the two glass base plates in such a manner as to sandwich a plurality of discharge cells between the two glass base plates.

In a plasma display panel, each of the discharge cells induced to emit light to form an image generates heat, and thus each constitutes a heat source, which causes the temperature of the plasma display panel to rise as a whole. Heat generated in the discharge cell is transferred to the glass forming the base plate, but due to the properties of the glass base plate material, heat conduction in a direction parallel to the panel plane is difficult.

In addition, the temperature of the discharge cells that are activated for light divergence increases significantly, and the temperature of the discharge cells that are not activated does not increase much. For this reason, the panel surface temperature of the plasma display panel increases locally at the place where the image is generated. In addition, discharge cells that are activated in the white or lighter spectrum produce more heat than are activated in the black or darker spectrum. Thus, the temperature of the panel face depends locally on the color produced when the image is produced. If a device for improving the temperature difference is not considered, this local temperature deviation can accelerate the thermal deterioration of the affected discharge cell. Additionally, as the state of the image on the display changes, the local heat generation location also changes with the image.

In addition, since the temperature difference between the activated discharge cell and the non-activated discharge cell can be large, and the temperature difference between the discharge cell generating white light and the discharge cell generating dark color can also be large, stress is applied to the panel unit. The plasma display panel may be damaged and cracks may be caused.

When the voltage applied to the electrodes of the discharge cells is increased, the brightness of the discharge cells is increased and the amount of heat generated in these cells is also increased. Therefore, such discharge cells, to which a large voltage is applied for activation, tend to be more sensitive to thermal degradation and to exacerbate the problem of breakage of the panel unit of the plasma display panel. Like PDPs, LEDs also have similar problems with heat generation. Similar problems arise with light emitting display devices such as LCDs and other display devices, where hot spots can limit the efficiency and life of the device.

As a thermal interface material for plasma display panels to fill the space between the back of the panel and the heat dissipation device and to equalize the local temperature difference, a so-called "high orientation graphate film" is used. It was proposed in US Pat. Nos. 5,831, 374 by Morita, Ichiyanagi, Ikeda, Nishiki, Inoue, Komsey and Kawashima, but no mention was made of the use or characteristic advantages of flexible graphite sheets. Additionally, U. S. Patent No. 6,482, 520 to Tzeng uses a sheet of compressed particles of graphite peeled off as a heat spreader (referenced in the patent as a thermal interface) for a heat source such as an electrical element. It is starting. Indeed, such materials are commercially available from O'Hare, Lakewood, Advanced Energy Technology INC as the eGraf®700 spreader shield class.

Graphite consists of layer planes of a network structure or hexagonal arrangement of carbon atoms. These layer planes of hexagonally arranged carbon atoms are substantially flat and are oriented or ordered to be substantially parallel and equidistant from each other. Sheets or layers of substantially flat, parallel equidistant carbon atoms, generally referred to as graphene layers or basal planes, are linked or bonded to one another and these groups are arranged in a crystalline state. Well ordered graphite consists of significant sizes of microcrystals, which microcrystals are well aligned or oriented with each other and have a well aligned carbon layer. That is, well aligned graphite has a very preferred microcrystalline direction. It should be noted that graphite has an anisotropic structure and exhibits or has many properties with high directivity such as thermal conductivity and electrical conductivity.

In short, graphite is characterized by a layered structure of carbon, ie the structure consists of an overlapping layer or laminae of carbon atoms bonded to each other by weak van der Waals forces. In view of the graphite structure, two axes or directions are generally mentioned, namely the "c" axis or direction and the "a" axis or direction. Simply, the "c" axis or direction can be considered as a direction perpendicular to the carbon layer. The "a" axis or direction may be considered 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 bonding force that holds the parallel layers of carbon atoms together is only a weak van der Waals force. Natural graphite is an expanded or swollen graphite structure in which the space between the overlapped carbon layers or layers is somewhat open to provide significant expansion in the direction perpendicular to the layer, i.e., the "c" direction, so that the layer properties of the carbon layer are substantially maintained. It can be processed to form.

Highly expanded, more specifically expanded graphate flakes having a final thickness or "c" direction dimension that is at least about 80 times larger than the initial "c" direction dimension can be used without the use of binders, for example, web, paper, It may be formed from an adhesive sheet or an integrated sheet of expanded graphite, such as a strip, tape, foil, mat, etc. (commonly referred to as "flexible graphite"). The formation of graphite particles expanded to a "c" directional dimension or final thickness that is about 80 times larger than the initial "c" directional dimension by an integral flexible sheet by compression without the use of any binding material is expanded to a large volume. It is believed that this is possible due to the mechanical bonding, or adhesion, achieved between the graphite particles.

In addition to flexibility, the sheet materials described above are particularly useful in thermal diffusion applications because they have large anisotropy for thermal conductivity due to the orientation of the graphite layer substantially parallel to the opposite surface of the expanded graphite particles and the site resulting from the large compression. Known. The sheet material so produced has excellent flexibility, good strength and high orientation.

In short, the process for producing flexible, binderless anisotropic graphite sheet materials, such as, for example, webs, paper, strips, tapes, foils, mats, etc., is intended to form a substantially flat, flexible integral graphite sheet. Compressing expanded graphite particles having a "c" directional dimension that is at least about 80 times greater than the "c" directional dimension of the initial particles without a binder under a predetermined load. Expanded graphite particles, which are generally worm-shaped in appearance, once compressed, remain compacted and aligned with the opposite major surface of the sheet. The density and thickness of the sheet material can be varied by controlling the degree of compression. The density of the sheet material may be in the range of about 0.04 g / cc to about 2.0 g / cc.

Flexible graphite sheet materials exhibit a significant degree of anisotropy due to the alignment of the graphite particles parallel to the opposite and parallel major surfaces of the sheet, the degree of anisotropy increasing upon compression of the sheet material to increase the orientation. In the compressed anisotropic sheet material, the thickness, ie the direction perpendicular to the opposing and parallel sheet surfaces, represents the "c" direction and is along the length and width, i.e. along the opposing major surfaces or parallel to the opposing major surfaces. Represents the "a" direction, and the thermal and electrical properties of the sheet differ by magnitude for the "c" and "a" directions.

In general, however, in the electronics industry, graphite particles can fall off when using graphite based materials, which can mechanically limit the operation and function of the device (ie in the same way as dust particles), More specifically, it has been known that graphite fragments can interfere with the operation of an electroluminescent display device due to the conductive properties of graphite. Although these ideas have been proven wrong, they still exist.

In addition, the use of an adhesive for attaching a graphite heat spreader to a light emitting display device may sometimes not be useful. More specifically, when reworking (removal or removal of the heat spreader) is required, the adhesive bond can be stronger than the structural bond of the graphite sheet; In this case, since the graphite sheet cannot be cleanly separated from the panel without using a tool such as a scraper, this is time consuming and can potentially cause damage to the graphite sheet, the panel, or both.

Accordingly, there is a need for a light weight and cost effective heat spreader for light emitting display devices, particularly a heat spreader that is insulated to prevent graphite particles from falling off and that can be efficiently removed from the device when needed. The required diffuser must be able to balance the temperature difference across the area of the device that is in contact by the diffuser, otherwise it must be able to reduce the thermal stress occurring where the panel is exposed, and the hot spot location is not fixed. It should be possible to perform a function that can reduce hot spots even in places.

Summary of the Invention

It is therefore an object of the present invention to provide a heat spreader for a display device such as a plasma display panel, a light emitting diode or a liquid crystal display.

It is another object of the present invention to provide a heat spreading material that can be used in a display device to improve the temperature difference that occurs during use.

It is a further object of the present invention to provide a heat spreading material in a heat source, such as one or more cells of a plasma display panel, so as to provide a heat spreading material between any two positions on the panel as compared to a panel without the heat spreader according to the invention. It is to reduce the temperature difference.

It is another object of the present invention to provide a heat spreading material which can be applied to a heat source assembly or heat source such as a plasma display panel or a light emitting diode, and can provide a good thermal contact between the heat spreader and the apparatus.

It is yet another object of the present invention to provide a heat spreading material that is insulated to prevent or reduce the chance of graphite particles falling into pieces.

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

It is an object of the present invention to provide a heat spreader having sufficient volume and being able to produce effectively even in the cost part.

The above objects which are apparent to those skilled in the art upon reading the following description are heat spreaders for display devices comprising at least one sheet of compressed particles of exfoliated graphite having a surface area larger than the surface area of the discharge cell portion facing the back of the display device. Can be achieved by providing The display device may be a light emitting display device such as a plasma display panel or a light emitting diode panel and another type of display device such as a liquid crystal display device. More specifically, at least one sheet of compressed particles of exfoliated graphite has a larger surface area than the surface area of the plurality of discharge cell portions facing the back of the device. Preferably, the heat spreader comprises a plurality of sheets of compressed particles of exfoliated graphite and has a protective coating thereon to prevent fragmentation of the graphite particles therefrom. In a preferred embodiment, for ease of sealing and reworking of the heat spreader, the surface of the heat spreader has an opposing sheet such as an aluminum or copper sheet thereon.

In a preferred embodiment, the heat spreader has an adhesive and a removal material, the adhesive is positioned to be inserted between the heat spreader and the removal material. The removal material and adhesive are selected to allow a predetermined removal rate of the removal material that does not cause undesirable damage to the heat spreader. In practice, the adhesive and removal material provide an average removal load of less than about 40 grams per centimeter at a removal rate of one meter per second, and more preferably less than about 10 grams per centimeter at a removal rate of one meter per second.

Additionally, the adhesive preferably achieves a minimum wrap shear adhesive strength of at least about 125 grams per square centimeter, and more preferably achieves a minimum wrap shear adhesive strength of at least about 700 grams per square centimeter. The adhesive results in an increase in the overall thickness heat resistance of the adhesive / heat spreading material that is less than about 35% when compared to the heat spreader itself. The thickness of the adhesive should be about 0.015 millimeters (mm) or less, more preferably 0.005 mm or less.

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

Graphite is a crystalline structure of carbon that contains atoms covalently bonded in a flat layer plane with weak bonds between planes. When obtaining raw materials such as flexible sheets of graphite, graphite particles such as natural graphite flakes are generally treated with an intercalant of, for example, a solution of sulfuric acid and nitric acid, so that the crystal structure of graphite React to form a compound. Particles of treated graphite are referred to as "intercalated graphite particles". When the intercalant in graphite is exposed to high temperatures, the organic agent decomposes and vaporizes so that the intercalated graphite particles are less than their initial dimensions in accordion form in the "c" direction, ie perpendicular to the crystal plane of the graphite. Expands to 80 times larger dimensions. Expanded (otherwise referred to as exfoliated) graphite particles are commonly referred to as worms because they are worm-shaped in appearance. The worm may be compressed in a flexible sheet, and unlike earlier graphite flakes, may be formed and cut in various forms and may have small transverse openings by deformed mechanical impact.

Graphite initial materials for flexible sheets suitable for use in the present invention are highly graphitic carbonaceous materials that can intercalate not only halides but also organic and inorganic acids and expand when exposed to heat. Include. These highly graphite carbonaceous materials most preferably have a degree of graphitization of about 1.0. As used herein, the term “graphitization degree” refers to the value g according to g = [[3.45-d (002)] / 0.095], where d (002) is in the crystal structure measured in Angstrom units. The distance between graphite layers of carbon. The distance between the graphite layers is measured by standard X-ray diffraction techniques. The location of the diffraction peaks corresponding to the (002), (004) and (006) Miller indices is measured, and standard least squares techniques are used to derive the distance that minimizes the overall error for all these peaks. Examples of highly graphite carbonaceous materials include natural graphite from various sources, as well as other carbonaceous materials such as graphite prepared by chemical vapor deposition, high temperature pyrolysis of polymers, or crystallization from molten metal solutions or the like. Natural graphite is most preferred.

The graphite initial material for the flexible sheet used in the present invention may contain a non-graphite component as long as the crystal structure of the initial material maintains the required degree of graphitization and the initial material can be peeled off. In general, carbon-containing materials capable of peeling and possessing the degree of graphitization required for the crystal structure are suitable for use in the present invention. Such graphite preferably has an ash content of 20% by weight or less. More preferably, the graphite used in the present invention will have a purity of at least about 94%. In the most preferred embodiment, the graphite used will have a purity of at least about 98%.

Methods of making graphite sheets are disclosed in US Pat. No. 3,404, 061, which is incorporated herein by reference to Shane et al. In the practice of the method of the patent granted to Shane et al., Natural graphite flakes are advantageously contained in a solution containing, for example, a mixture of nitric acid and sulfuric acid in an amount of about 20 to about 300 parts by weight of an organic agent per 100 parts by weight of graphite flake (pph). It is intercalated by dispersing the flakes into levels. Intercalation solutions contain oxidizing agents and other intercalating agents known in the art. Examples are for example mixtures of concentrated nitric acid and chlorate, chromic acid and phosphoric acid, sulfuric acid and nitric acid, or mixtures of strong organic acids such as trifluoroacetic acid or nitric acid, potassium chlorate, chromic acid, potassium permanganate, potassium chromate And solutions containing potassium dichromate, perchloric acid and the like and oxidizing agents such as strong oxidants and oxidizing mixtures which are soluble in organic acids. Alternatively, electrical potential can be used to cause oxidation of the graphite. Chemical species that can be introduced into graphite crystals using electrolyte oxidation include sulfuric acid as well as other acids.

In a preferred embodiment, the intercalating material is sulfuric acid, or a mixed solution of sulfuric acid with phosphoric acid and an oxidizing agent, ie nitric acid, perchloric acid, chromic acid, potassium permanganate, hydrogen peroxide, iodic acid or peroxoic acid and the like. Although less preferred, intercalation solutions are metal halides such as ferric chloride and ferric chloride mixed with sulfuric acid, or bromine as bromine solution and halides such as sulfuric acid or bromine in organic solvents. It may contain.

The amount of intercalation solution may range from about 20 to about 350 pph and more generally from about 40 to about 160 pph. After the flakes are intercalated, excess solution flows out of the flakes and the flakes are washed.

Alternatively, the amount of intercalation solution may be limited in the range of about 10 to about 40 pph, which may eliminate the washing step as disclosed and described in US Pat. No. 4,895,713, which is referenced herein.

The graphite flake particles treated with the intercalation solution are optionally selected by mixing with an organic reducing agent selected from alcohols, sugars, aldehydes and esters, which react with the surface film of the oxidative intercalating solution, for example, at temperatures ranging from 25 ° C. to 125 ° C. Can be contacted. Suitable specific organic agents include hexadecanol, octadecanol, 1-octanol, 2-octanol, decyl alcohol, 1,10 decandiol, decylaldehyde, 1-propanol, 1,3 propanediol, ethylene glycol, polypropylene Glycol, dextrose, fructose, lactose, sucrose, potato starch, ethylene glycol monostearate, diethylene glycol dibenzoate, propylene glycol monostearate, glycerol monostearate, dimethyl oxylate, diethyl oxylate, Ligrin derivatives such as methyl formate, ethyl formate, ascorbic acid and sodium lignosulfate. The amount of organic reducing agent is suitably about 0.5 to 4 weight percent of the graphite flake particles.

The use of inflation aids applied before, during or immediately after intercalation can also provide improvements. With these improvements the peel temperature can be reduced and the expanded volume (also referred to as the "worm volume") can be increased. The expansion aid herein is advantageously an organic material that is sufficiently soluble in the intercalation solution to achieve expansion improvement. More narrowly, organic materials of this type containing carbon, hydrogen and oxygen may preferably be used exclusively. Carboxylic acids are known to be particularly effective. Carboxylic acids useful as expansion aids include aromatic, aliphatic or cycloaliphatic, straight or branched, saturated and unsaturated monocarboxylic acids, dicarboxylic acids and one or more carbon atoms, preferably up to about 15 carbon atoms and It may be selected from polycarboxylic acids and is soluble in the intercalation solution in an amount effective to provide an improvement in one or more aspects of exfoliation. Suitable organic solvents can be used to improve the solubility of the organic expansion aid in the intercalation solution.

Representative examples of saturated aliphatic carboxylic acids are acids such as the formula H (CH ₂ ) _n COOH and include formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, and the like, where n is a number from 0 to about 5 to be. Instead of carboxylic acids, reactive carboxylic acid derivatives such as anhydrides or alkyl esters may also be used. Representative examples of alkyl esters are methyl formate and ethyl formate. Sulfuric acid, nitric acid and other known water soluble organic agents can ultimately break down formic acid into water and carbon dioxide. For this reason, formic acid and other sensitive expansion aids are preferably contacted with the graphite flakes before injecting the flakes into the water-soluble organic agent. Representative dicarboxylic acids are aliphatic dicarboxylic acids having 2-12 carbon atoms, in particular oxalic acid, fumaric acid, malonic acid, maleic acid, succinic acid, glutaric acid, adipic acid, 1,5-pentanedicarboxylic acid, 1,6-hexanedicarboxylic acid, 1,10-decanedicarboxylic acid, cyclohexane-1,4-dicarboxylic acid and aromatic dicarboxylic acid such as phthalic acid or terephthalic acid. Representative alkyl esters are dimethyl oxylate and diethyl oxylate. Representative alicyclic acids are cyclohexane carboxylic acids and representative aromatic carboxylic acids are benzoic acid, naphthoic acid, anthranilic acid, p-aminobenzoic acid, salicylic acid, o-, m-, and p-toryl acid, methoxy and o Oxy benzoic acid, acetoacetamidobenzoic acid and acetamidobenzoic acid, phenylacetic acid and naphthoic acid. Representative hydroxy aromatic acids are hydroxy benzoic 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. Citric acid is typical among polycarboxylic acids.

The intercalation solution is water soluble and preferably contains about 1 to 10% expansion aid, and this amount is effective to enhance exfoliation. In embodiments in which the dilation aid is contacted with the graphite flakes before or after infusion into the aqueous intercalation solution, the dilation aid is generally associated with the V-blender in an amount ranging from about 0.2% to about 10% by weight of the graphite flake. It may be mixed with graphite by such suitable means.

After intercalating the graphite flakes and then mixing the intercalated graphite flakes with the organic reducing agent, the mixture is exposed to a temperature in the range of 25 ° C. to 125 ° C. to promote the reaction of the reducing agent and the intercalated graphite flakes. You can. The heating period is up to about 20 hours, with shorter heating periods, for example at least about 10 minutes, for temperatures above the aforementioned range. A time of up to 30 minutes, for example on the order of 10 to 25 minutes can be used at higher temperatures.

The aforementioned method of intercalating and exfoliating graphite flakes may be advantageously improved by pretreatment of the graphite flakes at a graphitization temperature, ie, in the range of about 3000 ° C. and by the inclusion of flexible additives in the organic agent.

Pretreatment, or annealing, of graphite flakes results in significantly increased expansion (ie, an increase in expansion volume of up to 300% or more) when the flakes are subsequently intercalated and peeled off. In fact, preferably, the increase in expansion is at least about 50% compared to similar processing without the annealing step. The temperature used in the annealing step should not be significantly lower than 3000 ° C., since it results in substantially reduced expansion even at temperatures lower than 100 ° C.

Annealing of the present invention is carried out for a time sufficient to cause flakes with an improved degree of swelling upon intercalation and subsequent exfoliation. Generally the required time is at least 1 hour, preferably 1 to 3 hours, most preferably in an inert atmosphere. For maximum beneficial results, annealed graphite flakes may be prepared by other processes known in the art to improve the degree of expansion, namely organic reducing agents, intercalation aids such as organic acids, and surfactant cleaning agents after intercalation. Will undergo intercalation in the presence of Moreover, for maximum benefit, the intercalation step may be repeated.

The annealing step of the present invention is carried out in induction furnaces or other similar apparatuses known and recognized in the field of graphitization, where the temperature used is in the 3000 ° C. range and the high range of temperatures that can occur in the graphitization process.

Worms produced using graphite after preliminary intercalation annealing were often observed to “clump”, adversely affecting impact area weight uniformity, so additives that assisted in the formation of “free flowing” worms were Very preferred. Adding a flexible additive to the intercalation solution results in more uniformity of the worm across the bed of the compression device (such as the bed of the calendar station commonly used to compress (or “calender”) the graphite worm into a flexible graphite sheet). One distribution is easy. The resulting sheet therefore has greater area weight uniformity and tensile strength, even when the initial graphite particles are smaller than those previously used. The flexible additive is preferably a long chain hydrocarbon. While other functional groups are present, other organic compounds having long chain hydrocarbon groups can also be used.

More preferably, the flexible additive is an oil and is most preferred given the fact that mineral oil is less odor and odor which is an important consideration especially for long term storage. Note that any of the aforementioned expansion aids meet the definition of the flexible additive. When these materials are used as expansion aids, there is no need to include a separate flexible additive in the organic agent.

The flexible additive is present in the organicating agent in an amount of at least about 1.4 pph, more preferably at least about 1.8 pph. Although the upper limit of the content of the flexible additive is not more important than the lower limit, the inclusion of the flexible additive of about 4 pph or more does not have a significant additional advantage.

Graphite particles thus treated are often referred to as "intercarated graphite". When exposed to high temperatures, such as at least about 160 ° C. and particularly at temperatures of about 700 ° C. to 1000 ° C. or higher, the particles of intercalated graphite are in the “c” direction, ie the direction perpendicular to the crystal plane of the component graphite particles And expands in an accordion form about 80 to 1000 times more than the initial volume. Expanded, ie exfoliated, graphite particles are commonly referred to as worms because they are worm-shaped in appearance. The worms may be compression molded into flexible sheets with small transverse openings that can be formed and cut into various shapes as described above, unlike the initial graphite flakes.

Alternatively, the flexible graphite sheet of the present invention may utilize flexible graphite sheet particles that are regrounded rather than newly expanded worms. The sheet may be a newly formed sheet material, recycled sheet material, scrap sheet material, or any other suitable source.

The method of the present invention may also utilize a mixture of initial and recycled materials, or both recycled materials.

The source material of the recycled material may be a press-formed sheet or finish of the sheet, as described above, or a sheet compressed with a pre-calendering roll, for example. Furthermore, the source material may be a finish of a sheet or sheet that has been permeated with resin but not yet cured, or a finish of a sheet or sheet that has been permeated with resin and cured. The source material may be a recycled flexible graphite PEM fuel cell component such as a flow field plate or electrode. Each of the various graphite sources may be used as is or mixed with natural graphite flakes.

If the source material of the flexible graphite sheet is available, it can be connected with known processes or devices such as jet mills, air mills, blenders, etc. to produce particles. Preferably, most of the particles are 20 U.S. Pass through the mesh and more preferably the majority (at least about 20%, more preferably at least about 50%) are 80 U.S. It has a diameter that does not pass through the mesh. Most preferably the particles have a particle size of about 20 mesh or less.

The size of the ground particles may be chosen to balance the required thermal properties with the machinability and formability of the graphite particles. Therefore, smaller particles will result in graphite particles that facilitate machining and / or forming, while larger particles will result in greater anisotropy and greater in-plane electrical and thermal conductivity. .

When the source material is ground and the desired resin is removed if necessary, it is re-expanded. Re-expansion can be performed using the intercalation and exfoliation process and the disclosures in US Pat. No. 4,895,713 to Greinke et al. And US Pat. No. 3,404,061 to Shane.

Generally, the particles after intercalation are peeled off by heating the intercalated particles in the furnace. During this exfoliation step, intercalated natural graphite flakes may be added to the recycled and intercalated particles. Preferably, during the re-expansion step the particles are expanded to have a specific volume in the range of at least about 100 cc / g and up to about 350 cc / g or more. Finally, after the re-expansion step, the re-expanded particles may be compressed into a flexible sheet as described above.

Flexible graphite sheets and foils are adhered to good handling strength and are preferably compression molded, for example at a typical density of about 0.1 to 1.5 grams per cubic centimeter (g / cc) and a thickness of about 0.025 mm to 3.75 mm Is compressed by Although not always preferred, flexible graphite sheets may also be desirable to be sometimes handled with resins and absorbed resins, and the moisture resistance and handling of flexible graphite sheets, as well as tissue "fixing" of the sheets after curing. Strength, that is, rigidity is improved. When used, suitable resin contents are preferably about 5% or more by weight, more preferably about 10% to 35% of the weight, and preferably up to about 60% of the weight. Resins deemed particularly useful in the embodiments of the present invention are resin systems based on acrylic-, epoxy- and phenol, or mixtures thereof. Suitable epoxy resin systems include those based on diglycidyl ether or bisphenol A (DGEBA) and other multifunctional resin systems; Phenolic resins that may be applied include lithopoules and novolak phenols.

Referring to FIG. 4, the system is disclosed for the continuous production of resin impregnated flexible graphite sheets, in which graphite flakes and liquid insertable material are filled into reactor 104. More specifically, a container 101 is provided to contain a liquid insertable substance. The container 101, preferably made of stainless steel, can be supplied with a liquid organizing agent via the conduit 106 continuously. The vessel 102 contains graphite flakes that are guided into the reactor 104 with insertable material from the vessel 101. Each input ratio of insertable material and graphite flakes into the reactor 104 is controlled by valves 108 and 107. The graphite flakes in the vessel 102 may be supplied via the conduit 109 continuously. Additives such as, for example, intercalation enhancers such as trace acids, and organic chemicals may be added via dispenser 110 measured at its outlet by valve 111.

As a result, the intercalated graphite particles are soaked, acid coated, and preferably enter (through conduit 112) wash tank 114 where the particles are washed with water entering and exiting the wash tanks at 116, 118. . The washed and intercalated graphite flake then passes through drying chamber 122 through conduit 120. In order to control surface chemistry such as exfoliation during use and swelling, and to control gas evolution causing swelling, additives such as buffers, antioxidants, pollution reducing chemicals, etc. ) May be added.

Intercalated graphite flakes are dried in dryer 122, preferably at a temperature of about 75 ° C. to about 150 ° C., to avoid swelling or swelling of generally intercalated graphite flakes. After drying, the intercalated graphite flake is fed as a stream into the flame 200, for example by feeding it continuously to the collection vessel 124 via a conduit 126, and then expanding as indicated in 2. It is supplied as a stream into the flame 200 in the vessel 128. Ceramic fever particles formed from decomposed quart glass fever, carbon and graphite fever, zirconia, boron nitride, silicon carbide and magnesia fever, and naturally occurring inorganic fever additives such as Calcium metasilicate fever, calcium aluminum silicate fever, and aluminum oxide fever It can be added from the vessel 129 into a stream of intercalated graphite particles that are driven by inflow in the non-reactive gas guided at 127.

In the path through the flame 200 in the expansion chamber 201, the intercalated graphite particles 2 expand more than 80 times in the "c" direction and have an "inworm shape" expanded shape (5). do; Additives guided from 129 and mixed in the stream of intercalated graphite particles are essentially unaffected by the path through flame 200. Expanded graphite particles 5 may pass through gravity separator 130, where heavy ash natural mineral particles are separated from expanded graphite particles and then enter into wide upper hopper 132. Separator 130 may be omitted when not needed.

The expanded, ie exfoliated graphite particles 5 freely fall off with the other additives in the hopper 132 and scatter freely and pass through the passage 134 into the compression station 136. Compression station 136 includes exfoliated, oppositely converging moving porous belts 157, 158 to receive expanded graphite particles 5. Due to the converging space between the opposing moving belts 157 and 158, the exfoliated and expanded graphite particles are for example thick from about 25.4 to 0.075 mm, particularly from about 25.4 to 2.5 mm and from about 0.08 to 2.0 g Compressed to a mat of flexible graphite, indicated at 148, with a density of / cm < 3 >. The gas scrubber 149 can be used to remove and purge the gas emanating from the expansion chamber 201 and the hopper 132.

The mat 148 passes through the container 150 and seeps into the liquid resin from the spray nozzle 138, which is preferably " pulled through the mat " by the vacuum chamber 139, The resin is then dried in the dryer 160 to reduce the residue of the resin, after which the mat 143 into which the resin is soaked is densified with the rolled flexible graphite sheet 147 in the calender mill 170. Gas and smoke from the vessel 150 and dryer 160 are preferably gathered and purified in gas scrubber 165.

After the densification process, the resin in the flexible graphite sheet 147 is at least partially cured in the drying oven 180. Alternatively, partial curing may have an effect before the densification process, although after the densification process is preferred.

However, in a preferred embodiment, the flexible graphite sheet is free of resin, in which case the container 150, dryer 160 and drying oven 180 may be omitted.

Plasma display panels are currently being produced in sizes of 1 m and more (from corner to edge). Accordingly, the heat spreader used to improve and cool the effect of hot spots in such panels is also required relatively large in size of about 270 mm by about 500 mm, or as large as about 800 mm by 500 mm, or more. Greatly required. In the plasma display panel discussed above, there are tens of thousands of cells, each containing a plasma gas. When a voltage is applied to each cell, the plasma gas reacts with the phosphor to produce colored light in each cell. Plasma displays tend to be very hot because sufficient power is needed to ionize the gas to produce the plasma. In addition, depending on the color in a particular area of the panel, hot spots in the screen can be created that not only cause thermal stress in the panel itself, but also cause premature failure of the phosphor, which shortens the life of the display. Therefore, heat spreaders need to reduce the effects of these hot spots.

It has been found that sheets composed of compressed particles of exfoliated graphite, especially stacks of sheets of compressed particles of exfoliated graphite, can be specifically used as heat spreaders for display devices such as plasma display panels. More specifically, one or more sheets of compressed particles of exfoliated graphite, referred to herein as flexible graphite sheets, are placed in thermal contact with the back side of the plasma display panel, with the result that the flexible graphite sheets are plural in the panel. Two heat sources (ie, discharge cells). In other words, the surface area of the flexible graphite sheet area is larger than the surface area of the discharge cell at the back of the plasma display panel; In practice, the surface area of the flexible graphite sheet is larger than the surface area of the plurality of discharge cells on the back of the plasma display panel. Therefore, due to the nature of the flexible graphite material on which the heat spreader is formed according to the invention, when the image displayed by the panel changes, heat will spread from hot spots occurring at other locations on the plasma display panel.

Because of the properties of flexible graphite sheet materials, the contact resistance between the heat spreader and the plasma display panel is reduced in that they are more suitable than other materials, other forms of graphite, and according to the prior art applied with the same applied pressure. Better thermal contact is achieved when using a diffuser.

The flexible graphite sheet heat spreader according to the present invention works to reduce the thermal difference (ie, ΔT) between the areas on the display panel. In other words, the difference in temperature between the hot spots on the panel, such as the area where the white image is created, and the hot spots on the plasma display panel, such as the proximal area, where the dark image is created, ΔT when no flexible graphite sheet is present. Compared with, it can be reduced by using a flexible graphite heat spreader according to the present invention. Thus, otherwise, the thermal stress to which the plasma display panel is exposed is reduced, and the panel life and effect are extended. In addition, since hot spots (i.e. heat spikes) are reduced, the entire unit can operate at higher temperatures, resulting in image enhancement.

In fact, it may be desirable to have a graphite heat spreader manufactured with an adhesive layer that adheres the heat spreader to the plasma display panel, especially during the plasma display panel assembly process. A release liner should be used to cover the adhesive, which is sandwiched between the protective backing paper and the graphite sheet to allow for storage and shipping of the graphite heat spreader before being adhered to the plasma display panel.

The use of graphite sheets (or laminates of sheets) coated with an adhesive with protective backing paper has the requirement to meet practical needs for large scale display device manufacturing processes. More specifically, the protective backing paper should be able to be removed from the sheet at high speed without breaking the graphite into thin layers. Thin layer cracking occurs when the protective backing paper pulls the adhesive and any graphite peeled off the sheet when the protective backing paper is removed causes loss of graphite, damage to the graphite sheet itself, and the need for the adhesive to bond the graphite sheet to the display device. Not only decrease, but also cause unsightly and unpleasant appearance.

However, although adhesives and protective backing papers should be selected to allow removal of the protective backing paper from the adhesive / graphite sheet without breaking the graphite into thin layers, the adhesive does not allow the graphite sheet to be placed in position on the display device with the panel in various orientations. It must be strong enough to maintain and ensure good thermal contact between the heat spreader and the device.

In addition, a significant reduction in the thermal performance of the heat spreader should not be caused by the adhesive. That is, the adhesive applied to a layer of considerable thickness may interfere with the thermal performance of the heat spreader because it interferes with the heat conduction from the plasma display panel or other display device to the heat spreader.

Therefore, the combination of adhesive and protective backing paper is at most about 40 g / cm, more preferably at most about 20 g / cm and most preferably at a removal rate of about 1 m / s as measured, for example, in a ChemInstruments HSR-1000 fast removal tester. Balance must be achieved to provide a removal load of about 10 g / cm or less. For example, if it is desirable to remove the protective backing paper at a speed of about 1 m / s to meet the large manufacturing requirements of display devices such as plasma display devices, the average removal load of the protective backing paper is that the graphite is ground at the removal rate. It should be about 40 g / cm or less, more preferably about 20 g / cm or less, and most preferably about 10 g / cm or less to allow removal of the protective backing paper without causing loss. To achieve this, the thickness of the adhesive should be about 0.015 mm or less, most preferably 0.005 mm or less in thickness.

Another factor that must be balanced is the adhesive strength of the adhesive sufficient to maintain the heat spreader at a location on the display device during the manufacturing process and to ensure good thermal contact between the heat spreader and the device, as described above. In order to achieve the required adhesion, the adhesive should have a minimum lap shear bond strength of at least about 125 g / cm 2, more preferably an average lap shear bond strength of about 700 g / cm 2, as measured, for example, on a ChemInstruments TT-1000 tensile tester. .

As described above, the adhesive should not substantially interfere with the thermal performance of the heat spreader. This means that the presence of the adhesive should not cause an increase in the overall thickness thermal resistance of more than about 100% of the heat spreader compared to the heat spreader itself without the adhesive. In fact, in a more preferred embodiment, the adhesive will not cause an increase in thermal resistance of about 35% or more as compared to the heat spreader material without the adhesive. Therefore, the adhesive must meet the removal load requirements and the average lap shear bond strength requirements while being thin enough to avoid a significant increase in undesirable thermal resistance. For this purpose, the adhesive should be thinner than about 0.015 mm, more preferably about 0.005 mm.

The heat spreader is applied to a display device such as a plasma display panel in a large scale manufacturing process, wherein the heat spreader is a compressed particle sheet of exfoliated graphite or a laminate of sheets having a thickness of about 2.0 mm or less and a density in the range of about 1.6 to about 1.9 g / cc. With protective backing paper made of silicone coated kraft paper, such as L2 or L4 protective backing paper, made and used from Sil Tech, a spray of Technicote Inc., to achieve the balance required for the manufacture of heat spreaders useful for Commercially available pressure sensitive acrylic adhesives manufactured from Ashland Chemical, Inc., of desired thickness, may achieve the desired results. Therefore, the removal layer is positioned so that the adhesive is sandwiched between the heat spreader material and the removal material, and the sheet or sheet of compressed particles of exfoliated graphite has a thickness of adhesive that substantially does not impair the thermal performance of the heat spreader. A heat spreader composite is provided that includes a heat spreader material such as water. During operation, the removal material may be removed from the heat spreader / adhesive combination and the heat spreader / adhesive combination may be applied to a display device such as a plasma display panel such that the adhesive adheres the heat spreader material to the plasma display panel. Moreover, when multiple plasma display panels are manufactured, one or more heat spreader / adhesive combinations are applied to each of the multiple plasma display panels.

When a flexible graphite laminate is employed as the heat spreader according to the invention, other laminate layers may also be included, which improves the mechanical or thermal performance of the laminate. For example, laminate layers of thermally conductive metals, such as aluminum or copper, can be sandwiched between flexible graphite layers to increase the thermal diffusion properties of the laminate without sacrificing the low contact resistance present by graphite. have; Other materials, such as polymers, may also be employed to enhance or enhance the strength of the laminate. Additionally, the graphite material may be a single sheet or laminate, which may reduce damage to the sheet and / or improve material handling during application or shipment to the display device without compromising the heat spreading performance of the heat spreader of the present invention. For example, a back of a thin plastic sheet or, alternatively, a thin coating of dried resin can be provided. Layers of insulating material may also be employed.

In addition, the surface of the heat spreader, which is intended to be in contact with the display device, may have a facet of material to enhance thermal performance and / or ability to rework the heat spreader of the present invention. Most preferred are metals such as aluminum or copper, of which double aluminum is most suitable. Although there is some thermal loss in terms of greater contact resistance (because such a face does not come into contact with the surface of the device when such face is used), this can be made by the thermal isotropy of the metal face. . However, in addition to this, since this is a surface that is adhered to the surface of the device, it is easy to remove the heat spreader of the present invention for reworking or other operations, and because the structure of the metal surface is stronger than the adhesive bond It is possible to remove the heat spreader quickly and without damage from the display device surface.

As shown in FIG. 1, the flexible graphite sheet or laminate, once formed for use as the heat spreader of the present invention, indicated at 10, can be cut into the required shape, and in most cases is square. If shown (as shown, the heat spreader 10 may be cut into a curved or more complex shape that is different from the square shape, which will have a different number of corner surfaces 16). If is square, the heat spreader 10 has one or more corner surfaces 16, generally four corner surfaces 16a, 16b, 16c, 16d, as well as two major surfaces 12 and 14.

Referring to FIGS. 1-3, the heat spreader 10 also preferably includes a protective coating 20, in which graphite particles are separated from the flexible graphite sheet or laminate that makes the heat spreader 10, or This is to prevent the possibility of separation in other forms. The protective coating 20 also preferably insulates the heat spreader 10 effectively to avoid electrical interference caused by the inclusion of an electrically conductive material (graphite) in the electrical device. The protective coating 20 may comprise a material that is sufficiently suitable to electrically insulate graphite and / or prevent the graphite material from falling off, such as thermoplastic materials such as polyethylene, polyester or polyimide, waxes and / or varnish materials. have. Indeed, when grounding is required as opposed to being electrically insulated, the protective coating 20 may comprise a metal, such as aluminum.

Preferably, in order to achieve the required peel-resistance and / or electrical insulation, the protective coating 20 is preferably at least about 0.001 mm thick. Although this is not the actual maximum thickness for the protective coating 20, the protective coating 20 should be about 0.025 mm or less, preferably about 0.005 mm or less to function effectively.

When the heat spreader 10 is applied to a display device such as a plasma display panel, the major surface 12 of the heat spreader 10 is the side that is in operative contact with the panel. In many embodiments, as such, the contact between the major surface 12 and the panel functions to 'seal' the major surface 12 against graphite exfoliation, resulting in a major surface (in addition to the protective coating 20). Eliminate the need to coat 12). Similarly, it is not necessary to electrically insulate the major surface 14 from the remainder of the electrical device in which the heat spreader 10 is located, which electrically insulates the major surface 12. However, for handling or other considerations, in some embodiments, a protective coating 20 may be used with any adhesive used on the major surface 12 to adhere the heat spreader 10 to a plasma display panel (not shown). It may be coated between both major surfaces 12 and 14 of the heat spreader 10 that enters between the graphite sheets.

Heat spreader 10 may be provided to protective coating 20 by a variety of different processes. For example, once the flexible graphite sheet or laminate is cut to size and shape to form the heat spreader 10, the material from which the protective coating 20 is formed is coated on the individual heat spreader 10, thereby almost predominantly. It flows seamlessly into the surface 14 and the edge surface 16 and the like and extends beyond the edge surface 16 and the like to form a protective peel boundary of the heat spreader 10 almost as shown in FIG. 1. As a result, the protective coating 20 can be applied by various coatings in a manner familiar to those skilled in the art such as spray coating, roller coating and hot lamination presses.

In an alternative embodiment, as shown in FIG. 2, a protective coating 20 is applied to the heat spreader 10 to cause electrical interference and / or potentially peel off (eg, as exposed). One or more corner surfaces 16a, 16b, 16c, 16d).

In another embodiment of the present invention, as shown in FIG. 3, a protective coating 20 can be applied to the heat spreader 10 to coat only the major surface 14. A particular advantage of this embodiment of the manner in which the heat spreader 10 is produced is that the flexible graphite sheet or laminate is coated with a protective coating 20 such as roller coating, lamination with an adhesive, or hot press lamination, It then cuts the flexible graphite sheet or laminate into the shape of the desired heat spreader 10. In this way, manufacturing efficiency is maximized and waste of the protective coating 20 is minimized during the manufacturing process.

In general, the coating process of adhering the protective coating 20 to the heat spreader 10 has sufficient strength in most embodiments. However, if necessary, or relative to the protective coating 20, such as Mylar® polyester material and Hommon polyamide material (commercially available from EI du Pont de Nemours and Company of Wilmington), A layer 30 of can be applied between the heat spreader 10 and the protective coating 20, as shown in FIG. Suitable adhesives are those that can facilitate the adhesion of the protective coating to the heat spreader 10, such as an acrylic or latex adhesive. The layer of adhesive 30 may be coated on either or both of the heat spreader 10 and the protective coating 20. The layer of adhesive 30 is preferably as thin as possible while maintaining adhesion between the protective coating 20 and the heat spreader 10. The layer 30 of adhesive is preferably about 0.015 mm or less in thickness.

Additionally, in other embodiments, the heat spreader 10 may include a surface layer 40 sandwiched between the surface 12 of the heat spreader and the surface of the display device. As discussed above, the face layer 40 is preferably a metal, such as aluminum, which is a layer of adhesive applied between the face layer 40 and the surface 12 of the heat spreader, as shown in FIG. 1. By using 50 it can be adhered to the surface 12. Suitable adhesives are acrylic or latex adhesives, which may be coated on either or both of the cotton layer 40 and the heat spreader surface 12. The adhesive 50 is, of course, applied as thinly as possible while maintaining the adhesion on the surface layer 40 and the surface 12, preferably about 0.015 mm or less in thickness.

Additionally, as shown in FIG. 1, the face layer 40 can be combined with a protective coating 20 for sealing the graphite heat spreader 10 between the face layer 40 and the protective coating 20. More specifically, if the face layer 40 extends beyond the edge 16 of the diffuser 10 or the like, a protective coating can be applied to the heat spreader 10 and the face layer 40 substantially. Alternatively, a material such as aluminum tape may be applied to seal the edges 16 and the like between the cotton layer 40 and the protective coating 20.

Although the present embodiment has been described in terms of applying a heat spreader to a plasma display panel, the inventive method and heat spreader are equally luminescent as well as another display device that generates locally hot spots or hot spots, such as liquid crystal displays. The same applies to other light emitting display device heat sources, or heat source assemblies (such as diodes, which function individually as a set of individual discharge cells that make up a plasma display panel).

The following examples illustrate the operation and effects of the embodiments of the invention, but are for illustration only and do not limit the scope and breadth of the invention claimed.

Example 1

The thermal properties of Panasonic plasma TV model number TH42PA20 using an acrylic heat spreader attached to the back of the plasma display panel are analyzed under the following different screen conditions. White and black patterns are generated on the display and the screen surface temperature is measured using an infrared camera. In all cases the background is black. The pattern consists of 1) three white lines spaced horizontally across the screen (23.9% screen illumination) and 2) a 4 × 3 array of white dots evenly spaced (4% screen illumination). After testing the unit with the conventional acrylic heat spreader, the acrylic diffuser was removed and replaced with a flexible graphite heat spreader having a thickness of 1.4 mm and an in-plane thermal conductivity of about 260 W / m ° K. The plasma display is then retested under the same conditions as described above, and the results are shown in Table 1.

pattern Heat spreader T _max White pattern T range around White line pattern acryl 49.3 30 24.1 White line pattern Flexible Graphite 48.6 34.4 23.5 White dot array pattern acryl 51.8 30.4 24.3 White dot array pattern Flexible Graphite 39.3 28.3 23.4

Example 2

The thermal properties of the NEC plasma display model Plasmasync 42 "42XM2 HD are analyzed under the following different conditions using an aluminum / silicone heat spreader attached to the back of the plasma display panel. White and black patterns are generated on the display and the screen surface. The temperature is measured using an infrared camera, in all cases the background is black The pattern is: 1) three white lines (23.9% screen illumination) that are evenly spaced horizontally across the screen and 2) evenly spaced It consists of a 4 × 3 array of white dots (4% screen illumination) After testing the unit with a conventional aluminum / silicon heat spreader, the aluminum / silicone heat spreader is removed and the thickness is 1.4 mm and the thermal conductivity is about 260 W. replaced with a flexible graphite heat spreader of / m ° K. The display was then retested under the same conditions as described above. And the result is shown in Table 2.

pattern Heat spreader T _max White pattern T range around White line pattern Aluminum / silicone 61.4 32.9 25.2 White line pattern Flexible Graphite 55.1 33.9 24.9

These embodiments illustrate the advantages of using a flexible graphite heat spreader over conventional heat spreader techniques, both at the maximum temperature (T _max ) and the observed temperature range (T _range ).

All cited patents and publications mentioned herein are incorporated herein by reference.

It is therefore evident that the present invention may be modified in various ways, as described. Such modifications, which are not considered to depart from the spirit and scope of the present invention and are apparent to those skilled in the art, are intended to be included in the following claims.

Accordingly, according to the present invention, an object is provided for a heat spreader for a display device such as a plasma display panel, a light emitting diode or a liquid crystal display. The present invention also provides a heat spreader material that can be used in a display device to improve the temperature difference that occurs during use. In addition, according to the present invention, a heat spreader material is provided in a heat source such as one or more cells of the plasma display panel, so that the temperature difference between any two positions on the panel as compared with the panel without the heat spreader according to the present invention is reduced. Will be reduced. According to the present invention, there is also provided a heat spreading material which can be applied to an aggregate or heat source of a heat source such as a plasma display panel or a light emitting diode, and can provide good thermal contact between the heat spreader and the device. The invention also provides an isolated heat spreader material to prevent or reduce the likelihood of graphite particles falling into pieces. Further, according to the present invention, the diffusion diffusion is provided with a heat spreader that can be adhered to and removed from the heat source with minimal damage to the heat source. According to the present invention there is also provided a heat spreader having sufficient volume and being able to produce effectively even at a costly part.

1 is a partial cutaway top schematic view of an embodiment of a heat spreader according to the present invention.

2 is a partial cutaway top schematic view of another embodiment of a heat spreader according to the present invention.

3 is a side view of another embodiment of a heat spreader of the present invention.

4 shows a system for the continuous production of a resin-infused flexible graphite sheet.

Claims (20)

A heat spreader for a display device, the heat spreader having a larger surface area than the surface area of the portion at which a higher temperature localized area of the display device is created and comprising one or more sheets of compressed particles of exfoliated graphite, Heat spreader for display devices. The display device of claim 1, wherein the display device is a light emitting display device, and wherein at least one sheet of compressed particles of exfoliated graphite has a surface area larger than the surface area of the discharge cell portion facing the back of the light emitting display device. Heat spreader for display device provided. The heat spreader of claim 2, wherein the light emitting display device comprises a plasma display panel. 4. The heat spreader of claim 3, wherein the at least one sheet of compressed particles of exfoliated graphite has a larger surface area than the surface area of the plurality of discharge cell portions facing the back of the plasma display panel. The heat spreader of claim 1, wherein the heat spreader comprises a stack including a plurality of sheets of compressed particles of exfoliated graphite. 6. The heat spreader of claim 5, wherein the stack comprises a layer of non-graphite material. The heat spreader of claim 1, wherein the heat spreader comprises an adhesive and a removal material, and the adhesive is inserted between the heat spreader and the removal material. 8. The heat spreader of claim 7, wherein the removal material and the adhesive are selected to allow a predetermined removal rate of the removal material without causing undesirable damage to the heat spreader. The heat spreader of claim 8, wherein the adhesive and the removal material provide an average removal load of less than about 40 grams per centimeter at a removal rate of one meter per second. 10. The heat spreader of claim 9, wherein the adhesive achieves a minimum wrap shear adhesive strength of at least about 125 grams per square centimeter. The heat spreader of claim 10, wherein the adhesive achieves an average wrap shear adhesive strength of at least about 700 grams per square centimeter. The heat spreader of claim 11, wherein the adhesive has a thickness of about 0.015 mm or less. The heat spreader of claim 1, wherein at least one of the major surfaces of the surface area is coated with a protective coating sufficient to prevent delamination of particles of graphite. The heat spreader of claim 13, wherein the protective coating comprises a metal or thermoplastic material. The heat spreader of claim 14, wherein the protective coating has a thickness of about 0.025 mm or less. The heat spreader of claim 15, wherein the protective coating is effective to electrically insulate the coated major surface of at least one sheet of compressed particles of exfoliated graphite. The display device of claim 12, wherein the one or more sheets of extruded graphite compressed particles have edge surfaces, the one or more edge surfaces being coated with a protective coating sufficient to prevent exfoliation of the particles of graphite. Diffuser. 13. The heat spreader of claim 12, further comprising a layer of adhesive interposed between the protective coating and one or more sheets of compressed particles of exfoliated graphite. The heat spreader of claim 1, further comprising a surface layer adhered to the surface area to be inserted between the display device and a sheet of compressed particles of exfoliated graphite. 20. The heat spreader of claim 19, wherein said face layer comprises a metal.