KR102547787B1 - A foam sheet having excellent thermal conductivity, and heatsink containing the same - Google Patents

Abstract

The present invention relates to a thermally conductive foam sheet and a heat dissipation sheet including the same, wherein the foam sheet has a structure in which a specific amount of carbon material is dispersed in a hard polyester resin, and is lightweight and exhibits high thermal conductivity, thereby providing heat dissipation and durability. It can be usefully used for electronic devices such as mobile phones, tablet terminals, electronic printers, notebook PCs, etc., or light emitting modules such as LED lights.

Description

Foam sheet with excellent thermal conductivity, heat radiation sheet including the same {A FOAM SHEET HAVING EXCELLENT THERMAL CONDUCTIVITY, AND HEATSINK CONTAINING THE SAME}

The present invention relates to a thermally conductive foam sheet and a heat radiation sheet including the same.

The heat dissipation sheet is installed in a surface contact state where a high heat is generated, such as a heat generating part of a device or system, such as a light emitting module of an LED light, absorbs the heat, and dissipates the absorbed heat into the air with a wide contact area used for a purpose The heat dissipation sheet used for this purpose is to dissipate heat into the air through heat transfer, and conventionally, metal materials have been used, and aluminum materials have been widely used. Aluminum has a light specific gravity of 2.7 and excellent physical properties such as a thermal conductivity of 236 W/mK, and is also the most widely used as a heat dissipation sheet because it is cheap and easy to purchase.

These heat dissipation sheets are manufactured in various forms depending on the purpose and purpose of use. The common feature is that the flat part formed on one side of the body is fixed in contact with a heating member that generates heat, and a plurality of heat dissipation formed on the other side. The asperities are exposed to air. Accordingly, since air circulates in the heat dissipation sheet through gaps formed between the plurality of heat dissipation protrusions, the heat absorbed by the body and the heat dissipation protrusions is exposed to the circulating air and cooled, thereby performing the purpose of dissipating heat in an air-cooled manner.

However, although these conventional heat dissipation sheets use aluminum materials having a small specific gravity and relatively excellent thermal conductivity, in order to dissipate heat from a large lamp, the aluminum heat dissipation sheet must also be large, so it is bulky and heavy, making it difficult to install and malfunctioning. There is a disadvantage in that there is a lot of hassle in replacing the heat radiation sheet due to its heavy weight.

In addition, when a polymer resin is applied to lighten the weight of the heat radiation sheet, metals such as aluminum cannot be completely excluded or the corresponding thermal conductive particles are used in a significantly larger amount than the polymer resin, resulting in a light weight effect when used as a large heat radiation sheet. There is a slight limit, and there is a limit in that the mechanical strength and / or thermal conductivity of the sheet constituting the heat radiation sheet is lowered when they are completely excluded or the amount used is significantly reduced.

Republic of Korea Patent Publication No. 10-2009-0074302 Republic of Korea Patent Publication No. 10-2017-0129149

Accordingly, an object of the present invention is to provide a heat radiation sheet having excellent mechanical strength and thermal conductivity while lightening the weight.

In order to solve the above problems,

In one embodiment, the present invention

It has a structure in which a carbon material is dispersed in a polyester resin,

The content of the carbon material provides a foam sheet, characterized in that 20 to 50 parts by weight relative to the total weight.

In this case, the carbon material may include at least one selected from the group consisting of graphite, carbon black, acetylene black, carbon nanotube, carbon fiber, graphene, and graphite.

In addition, the basis weight of the foam sheet may be 100 g/m 2 to 1,000 g/m 2 , and the average thickness of the foam sheet may be 0.1 mm to 10 mm.

In addition, the foam sheet may have an average foam density of 100 to 600 kg/m3 based on KS M ISO 845:2012.

In addition, the resin forming the polyester foam layer is polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly lactic acid (PLA), polyglycolic acid , PGA), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN) selected from the group consisting of There may be more than one species.

Furthermore, the thermal conductivity of the foam sheet may be 0.1 to 10 W/m·K.

In addition, in one embodiment, the present invention provides a heat dissipation sheet including the foam sheet.

The foam sheet according to the present invention has a structure in which a specific amount of carbon material is dispersed in a hard polyester resin, so it is light and exhibits high thermal conductivity, so it can be usefully used as a heat dissipation sheet for electronic devices or light emitting modules requiring heat dissipation and durability. can

Since the present invention can have various changes and various embodiments, specific embodiments will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present invention, the term "comprises" or "has" is intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Hereinafter, the present invention will be described in more detail.

foam sheet

In one embodiment, the present invention

It has a structure in which a carbon material is dispersed in a polyester resin,

The content of the carbon material provides a foam sheet, characterized in that 20 to 50 parts by weight relative to the total weight.

A foam sheet according to the present invention is a foam sheet composed of a polymer resin, and has a structure in which a carbon material is dispersed in the polymer resin. At this time, the carbon material is uniformly dispersed in the polymer resin and performs a function of uniformly dispersing heat applied to the foam sheet to the entire surface of the sheet, while performing a role of realizing a heat dissipation effect. To this end, the foam sheet may be included in specific amounts.

Specifically, the carbon material may be included in 20 to 50 parts by weight based on the total weight of the foam sheet, and more specifically, 20 to 45 parts by weight based on the total weight of the foam sheet; 20 to 40 parts by weight; 25 to 50 parts by weight; 30 to 50 parts by weight; 30 to 45 parts by weight; or 30 to 40 parts by weight.

The carbon material of the present invention can prevent the heat dissipation effect of the foam sheet from not being realized due to the low content (less than 20 parts by weight) of the carbon material by adjusting the content of the carbon material to the above range, and at the same time, the high content (50 parts by weight) Excess) of carbon materials can prevent the weight of the foam sheet from becoming heavy and deteriorating economic feasibility.

In addition, the present invention is not particularly limited as long as it is a material composed only of carbon and can implement a heat radiation effect, and can be used as a carbon material. For example, the carbon materials include particulate carbon materials such as graphite, carbon black, and acetylene black; linear carbon materials such as carbon nanotubes and oxygen fibers; and plate-shaped carbon materials such as graphene and graphite, and these may be used alone or in combination of two or more.

Here, the granular carbon material is a particulate material, and is inexpensive and economical, has excellent dispersibility in a resin, and has excellent thermal conductivity and heat dissipation effect.

In addition, the linear carbon material is a fibrous material having a long length compared to the diameter, and is dispersed in a polyester resin to form a network, so that it can exhibit high heat dissipation properties unlike ceramic materials that do not exhibit heat dissipation properties due to low thermal conductivity. there is. In addition, when the linear carbon material is used in combination with the plate-shaped carbon material, it is possible to realize a uniform heat dissipation effect of the foam sheet by inducing uniform dispersion of the plate-shaped carbon material exhibiting a stacking tendency in the resin. Such linear carbon materials may include carbon nanotubes, specifically, single-walled carbon nanotubes, functionalized single-walled carbon nanotubes, double-walled carbon nanotubes, functionalized double-walled carbon nanotubes, multi-walled carbon nanotubes, and It may include at least one of functionalized multi-walled carbon nanotubes.

As an example, the foam sheet of the present invention may use granular graphite, carbon black, or acetylene black alone as a carbon material, or may use the granular carbon material and linear carbon nanotubes in combination.

In addition, the average size of the carbon material may be 10 nm to 5000 nm, specifically 20 nm to 2000 nm, 25 nm to 1500 nm, or 30 nm to 550 nm. More specifically, the carbon material may have an average size of 15 nm to 200 nm or 25 nm to 550 nm. By including the carbon material as described above, it is possible to improve the dispersibility of the carbon material and at the same time improve the thermal conductivity of the foam sheet.

In addition, the foam sheet includes a polyester resin as a main resin constituting the sheet.

Polyester resins having crystallinity, such as polyethylene terephthalate (PET), have excellent mechanical properties, thermal properties, and chemical resistance, compared to polyolefin resins such as polyethylene-based resins and polypropylene-based resins, polystyrene, or polyurethane, and are lightweight and It can be used in various fields requiring high physical properties. In the present invention, high mechanical properties can be implemented in the foam sheet by using the polyester resin as a main component of the foam sheet. Here, the main component may mean that it accounts for 70% by weight or more, 80% by weight or more, or 90% by weight or more of the total foam sheet, and in some cases, it may be 100% by weight.

In addition, 90% or more of the cells of the foam sheet may include closed cells (DIN ISO4590) in order to realize a high heat dissipation effect. This may mean that 90% or more of the cells measured according to DIN ISO4590 of the foam sheet are closed cells. For example, the number of closed cells in the foam sheet may be 90 to 100% or 95 to 100%.

In addition, the average foam density of the foam sheet may be 100 to 600 kg / m 3 based on KS M ISO 845: 2012, specifically 100 to 500 kg / m 3, 100 to 400 kg / m 3 based on KS M ISO 845: 2012 , 100 to 300 kg/m3, 100 to 200 kg/m3, 200 to 600 kg/m3, 300 to 600 kg/m3, 400 to 600 kg/m3, or 500 to 600 kg/m3.

The foam sheet according to the present invention has closed cells with the foaming density as described above, thereby realizing excellent thermal conductivity and heat dissipation characteristics along with high mechanical properties, and through this, electrical appliances and lighting devices requiring heat dissipation of the foam sheet It can be easily used as a heat dissipation sheet, etc.

As an example, the foam sheet has excellent thermal conductivity and may exhibit a thermal conductivity of 0.1 to 10 W/m K, specifically 0.1 to 5 W/m K, 0.1 to 3 W/m K, 0.1 to 2 W/m K, 0.5 to 5 W/m K, 0.5 to 3 W/m K, 0.5 to 2 W/m K¸1 to 10 W/m K, 1 to 5 W/ m·K, 1 to 3 W/m·K, 2 to 5 W/m·K, or 1.5 to 3.5 W/m·K.

Furthermore, the foam sheet according to the present invention has a structure in which a specific amount of carbon material is dispersed in a polyester resin, so as described above, it has the advantage of being lightweight while exhibiting high thermal conductivity and mechanical properties. Specifically, the foam sheet according to the present invention may have a small basis weight representing weight per unit area. More specifically, the basis weight of the foam sheet may be 100 g/m2 to 1,000 g/m2, specifically 100 g/m2 to 900 g/m2, 200 g/m2 to 800 g/m2, 300 g/m2 to 700 g/m2, 300 g/m2 to 650 g/m2, 300 g/m2 to 500 g/m2, 300 g/m2 to 450 g/m2, 350 g/m2 to 700 g/m2, 400 g/m2 to 700 g/m2, 500 g/m2 to 700 g/m2, 450 g/m2 to 650 g/m2, 500 g/m2 to 650 g/m2 or 350 g/m2 to 550 g/m2.

At this time, the average thickness of the foam sheet may be 0.1 to 10.0 mm, specifically, 0.1 mm to 2.0 mm, 0.1 mm to 1.0 mm, 0.5 mm to 4.5 mm, 1.0 mm to 3.0 mm, 1.0 mm to 2.5 mm, 1.0 mm to 1.8 mm, 1.5 mm to 2.0 mm, 1.0 mm to 4.0 mm, 1.5 mm to 4.5 mm, 2.0 mm to 5.0 mm, 1.5 mm to 2.5 mm, 2.0 mm to 2.5 mm, 1.0 mm to 2.0 mm or 5.0 mm to 7.0 mm.

The present invention can reduce the weight of the foam sheet by having the above configuration, and at the same time, not only can the mechanical properties of the foam sheet be improved, but also the heat dissipation effect of the foam sheet can be increased.

Meanwhile, the polyester resin included in the foam sheet may be prepared from raw materials commonly used in the art. Specifically, the polyester resin may be obtained by reacting a dicarboxylic acid component and a glycol component or reacting a hydroxycarboxylic acid component.

Here, as the dicarboxylic acid component, at least one selected from the group consisting of terephthalic acid, naphthalene dicarboxylic acid, and adipic acid may be used.

In addition, as the glycol component, 1 selected from the group consisting of ethylene glycol, butylene glycol and 2-methyl-1,3-propanediol More than one species can be used.

In addition, as the hydroxycarboxylic acid component, at least one selected from the group consisting of lactic acid and glycolic acid may be used, but is not limited thereto.

As an example, the polyester resin used in the present invention may be polyethylene terephthalate (PET) obtained by reacting terephthalic acid with ethylene glycol.

In addition, the polyester resin may be introduced in the form of pellets, granules, beads, chips, powder, etc., and in some cases may be introduced in a molten state. may be

As an example, the polyester resin may be introduced into an extruder in the form of a chip and extruded and foamed. In this case, the resin chip is melted at a temperature of 260 ° C to 300 ° C to melt the resin chip. It may go through a melting process.

In addition, in the step of manufacturing the foam sheet, various types of additives may be introduced into the fluid connection line or during the foaming process as needed when introducing the polyester resin into the extruder for functionalization of the foam sheet.

Specifically, the additives may impart barrier performance, hydrophilic function, or waterproof function to the foam sheet, and may include a thickener, a surfactant, a hydrophilic agent, a heat stabilizer, a waterproofing agent, a cell size expander, an infrared attenuator, a plasticizer, It may include at least one selected from the group consisting of fire retardant chemicals, pigments, elastomers, extrusion aids, antioxidants, nucleating agents, antistatic agents, and UV absorbers.

As an example, the foam sheet of the present invention may include one or more of a thickener, a nucleating agent, a heat stabilizer, and a foaming agent, and may further include one or more of the functional additives listed above.

Here, the thickener is not particularly limited, but in the present invention, for example, pyromellitic dianhydride (PMDA) may be used.

In addition, the thermal stabilizer may be an organic or inorganic phosphorus compound. Such an organic or inorganic phosphorus compound may be, for example, phosphoric acid and its organic esters, phosphorous acid and its organic esters. For example, the heat stabilizer is a commercially available material, and may be phosphoric acid, alkyl phosphate, or aryl phosphate, and more specifically, triphenyl phosphate, but is not limited thereto.

In addition, examples of the blowing agent include nitrogen (N ₂ ), carbon dioxide (CO ₂ ), Freon, butane, pentane, neopentane, hexane, isohexane, heptane, isoheptane, physical blowing agents such as methyl chloride, or azodicarbon Amide (azodicarbonamide) compound, p,p'-oxybis (benzenesulfonylhydrazide) [p,p'-oxy bis (benzene sulfonyl hydrazide)] compound, N,N'-dinitrosopentamethylenetetra There is a chemical blowing agent such as an amine (N,N'-dinitroso pentamethylene tetramine)-based compound, and specifically, carbon dioxide (CO ₂ ) may be used in the present invention.

heat radiation sheet

In addition, the present invention, in one embodiment, provides a heat radiation sheet comprising the foam sheet according to the present invention.

The heat dissipation sheet according to the present invention is not only light in weight because it does not include a metal layer made of aluminum or a large amount of thermally conductive particles, including the above-described foam sheet, but also exhibits excellent thermal conductivity and mechanical properties, so it can be used for mobile phones, It can be usefully used for a heat dissipation sheet used in electronic devices such as tablet-type terminals, electronic screeners, and notebook-type PCs, or light-emitting modules such as LED lights.

In this case, the heat dissipation sheet may refer to the foam sheet itself of the present invention, and in some cases may further include a separate layer excluding the metal layer on one side or both sides of the foam sheet.

Hereinafter, the present invention will be described in more detail by examples and experimental examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited to the following Examples and Experimental Examples.

Examples 1 to 4 and Comparative Examples 1 to 3.

Terephthalic acid, ethylene glycol, and carbon black and/or carbon nanotubes having an average particle size of 30 nm were introduced into an ester reactor, and a conventional polymerization reaction was performed at 258° C. to prepare a PET resin. At this time, the average size and content of carbon black and carbon nanotubes are as shown in Table 1 below. At this time, the content is a polyester resin, that is, terephthalic acid and ethylene glycol, which are the main components of the foam sheet. Weight ratio (parts by weight) to the total weight indicated by

100 parts by weight of the prepared PET resin was dried at 130° C. to remove water, and 100 parts by weight of the water-removed PET resin, 1 part by weight of pyromellitic dianhydride (PMDA), and 0.5 part by weight of calcium carbonate (CaCO ₃ ) were removed in the first extruder. , 0.1 part by weight of Irganox (IRG 1010) was mixed and heated to 280° C. to prepare a resin melt. Then, butane gas was mixed as a foaming agent in the first extruder, and the resin melt was sent to the second extruder and cooled to 220°C. The cooled resin melt passed through a die to form a PET foam sheet (average thickness: 1.0±0.1 mm). At this time, after taking samples of each manufactured foam sheet with a width of 2 cm × length of 2 cm, the foam density was measured with an underwater electron density meter (EW300SG, MIRAGE Co.), and the foam density of the measured foam sheet is shown in Table 1 below. shown in

carbon black carbon nanotube density size content length content Example 1 30±1 nm 35 parts by weight - - 350±10kg/㎥ Example 2 100±5 nm 35 parts by weight - - 330±10 kg/㎥ Example 3 500±10 nm 35 parts by weight - - 340±10 kg/㎥ Example 4 30±1 nm 10 parts by weight 200±10 nm 25 parts by weight 380±10kg/㎥ Comparative Example 1 - - - - 140±10kg/㎥ Comparative Example 2 30±1 nm 10 parts by weight - - 210±10 kg/㎥ Comparative Example 3 30±1 nm 60 parts by weight - - 370±10kg/㎥

Experimental example 1.

In order to evaluate the performance of the foam sheet according to the present invention, the following experiments were performed on the foam sheets prepared in Examples and Comparative Examples, and the results are shown in Table 2.

A) Thermal conductivity evaluation

The thermal conductivity of the foam sheet according to the hot disk method was measured using a thermal conductivity meter (model name: TPA-501), at which time the thermal conductivity was measured at 23 °C.

B) basis weight evaluation

Each foam sheet was cut into a width of 10 cm × length of 10 cm, and the weight of the cut foam sheet was measured, and then the weight per unit area was calculated.

thermal conductivity basis weight Example 1 1.2±0.05 250±5 Example 2 1.1±0.05 248±5 Example 3 1.1±0.05 254±5 Example 4 1.4±0.05 252±5 Comparative Example 1 0.2±0.05 135±5 Comparative Example 2 0.4±0.05 170±5 Comparative Example 3 1.2±0.05 330±5

As shown in Table 2, it can be seen that the foam sheet according to the present invention has a structure in which a specific amount of carbon material is dispersed in a polyester resin, and thus exhibits excellent mechanical properties as well as light and high heat dissipation characteristics.

Specifically, the foam sheet of Example has a structure in which a specific amount of carbon material is dispersed in a polyester resin, and has a basis weight of 300 g/m or less and exhibits high thermal conductivity of 1.0 W/m·K or more.

On the other hand, the foam sheets of Comparative Examples 1 and 2 do not contain or have a low content of carbon material, so the thermal conductivity is significantly lower than 1.0 W/m K, and the foam sheet of Comparative Example 3 has a basis weight due to an excessive amount of carbon material. was found to be greater than 300 g/m2.

From these results, it can be seen that the foam sheet of the present invention has excellent mechanical properties, and exhibits high heat dissipation characteristics while being lightweight.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art or those having ordinary knowledge in the art do not deviate from the spirit and technical scope of the present invention described in the claims to be described later. It will be understood that the present invention can be variously modified and changed within the scope not specified.

Therefore, the technical scope of the present invention is not limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims (8)

In the foam sheet composed of closed cells,
The foam sheet has a structure in which a granular carbon material is dispersed in a polyester resin,
The content of the granular carbon material is 20 to 50 parts by weight based on the total weight,
The average size of the granular carbon material is 25 nm to 550 nm,
The average foaming density of the foam sheet is 300 to 600 kg / ㎥ based on KS M ISO 845: 2012,
A foam sheet, characterized in that the closed cell of the foam sheet is 90% or more based on DIN ISO4590.
According to claim 1,
The granular carbon material is at least one selected from the group consisting of graphite, carbon black and acetylene black.
According to claim 1,
The foam sheet has a thermal conductivity of 0.1 to 10 W/m K.
delete According to claim 1,
The polyester resin is polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly lactic acid (PLA), polyglycolic acid (PGA), polyethylene adipate (Polyehtylene adipate, PEA), polyhydroxyalkanoate (PHA), polytrimethylene terephthalate (Polytrimethylene Terephthalate, PTT) and polyethylene naphthalate (Polyethylene naphthalate, PEN) At least one foam sheet selected from the group consisting of.
According to claim 1,
The basis weight of the foam sheet is 100 g / m 2 to 1,000 g / m 2 foam sheet.
According to claim 1,
The foam sheet has an average thickness of 0.1 mm to 10 mm.
A heat radiation sheet comprising the foam sheet according to claim 1.