KR102729810B1 - Flexible sheet for heat dissipation and display part comprising the same - Google Patents

Abstract

The present invention relates to a heat-radiating sheet, and more specifically, the heat-radiating sheet of the present invention comprises a heat-radiating layer formed of a polymer sheet including graphene particles, a first adhesive layer positioned on the upper portion of the heat-radiating layer, a second adhesive layer positioned on the lower portion of the heat-radiating layer, and a first flexible heat-radiating tape positioned on the upper portion of the first adhesive layer, wherein a through hole is formed in the heat-radiating layer, and thus has excellent folding properties and folding durability.

Description

FLEXIBLE SHEET FOR HEAT DISSIPATION AND DISPLAY PART COMPRISING THE SAME

The present invention relates to a heat dissipation sheet, and more specifically, to a flexible heat dissipation sheet having excellent reliability even when folded, and a display component using the same.

As electronic devices become more high-performance and thinner, they must be equipped with heat-dissipating sheets that effectively dissipate internal heat generated from heat sources such as embedded semiconductor components and light-emitting components. As interest in foldable display components has recently increased, heat-dissipating sheets must also have excellent foldability.

Copper foil, copper foil/graphite laminate, graphite sheet, etc. are used as heat-radiating sheets. Copper foil has both heat-radiating properties and electromagnetic shielding properties, but its horizontal thermal conductivity is lower than that of graphite, and its high density limits its weight reduction. In addition, copper foil has insufficient flexibility when its thickness exceeds approximately 50㎛, so it has limitations in applying it to heat-radiating sheets of complex shapes. Therefore, it is necessary to develop a composite heat-radiating sheet that has both a uniform heat-radiating effect and excellent foldability.

Prior art related to the present invention is disclosed in Korean Patent Registration No. 10-1922938, etc.

The present invention has been conceived in consideration of the above points, and has the purpose of providing a heat-dissipating sheet that is thinned and made dense, has excellent durability even when folded, and has excellent heat dissipation properties.

The purposes of the present invention are not limited to those mentioned above, and other purposes not mentioned will be clearly understood by those skilled in the art from the description below.

In order to solve the above-described problem, the heat dissipation sheet of the present invention comprises: a heat dissipation layer formed of a polymer sheet including graphene particles; a first adhesive layer positioned on an upper portion of the heat dissipation layer; a second adhesive layer positioned on a lower portion of the heat dissipation layer; and a first flexible heat dissipation tape positioned on an upper portion of the first adhesive layer; wherein a through hole is formed in the heat dissipation layer.

In addition, the heat-radiating sheet of the present invention may further have a second flexible heat-radiating tape and a third adhesive layer formed under the second adhesive layer.

By means of the above-described solution, the heat dissipation sheet of the present invention has excellent foldability by minimizing stress in the up-down direction and stress in the left-right direction when folded.

The heat-dissipating sheet of the present invention has excellent foldability as no wrinkles and/or lifting occur after folding compared to before folding.

In addition, the composite heat-dissipating sheet of the present invention has excellent thermal conductivity characteristics even after folding, thereby providing excellent heat dissipation effects and uniform heat dissipation effects between the folded and non-folded areas.

FIG. 1 is a cross-sectional view of a heat dissipation sheet according to one embodiment of the present invention.
FIG. 2 is a cross-sectional view of a heat dissipation sheet according to another embodiment of the present invention.

The above-mentioned purposes, features and advantages are described in detail below, so that those with ordinary knowledge in the technical field to which the present invention belongs can easily practice the technical idea of the present invention. In explaining the present invention, if it is judged that a detailed description of a known technology related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, a preferred embodiment according to the present invention will be described in detail.

The present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and the present embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform a person having ordinary skill in the art of the scope of the invention.

Hereinafter, the heat-radiating sheet and its manufacturing method according to the present invention will be described in detail.

When describing a numerical range in this specification, “X to Y” means “X or more and Y or less” (X≤ and ≤Y).

In this specification, “upper” and “lower” are defined based on the viewpoint viewed from the drawing.

Unless otherwise specified in this specification, various properties were measured at room temperature, for example, 20°C to 30°C.

Among the terms used in the present invention, “film” or “tape” is used to mean not only a film or tape of a specific thickness as defined in the art, but also a sheet that is generally thicker than a film or tape.

Below, the heat dissipation sheet according to the present invention is described in more detail.

[Heat dissipation sheet]

The inventor of the present invention has provided a heat dissipation sheet which provides excellent foldability by minimizing stress in the up-down direction and stress in the left-right direction during folding, and has an excellent appearance compared to before folding even when folded under harsh folding conditions, and when applied to a display device, does not exhibit wrinkles or a phenomenon that impairs the surface quality on both sides of the display device when folded under harsh folding conditions, and provides excellent heat dissipation performance and a uniform heat dissipation effect between the folding area and the non-folding area.

Referring to FIG. 1, a heat dissipation sheet (100) of the present invention includes a heat dissipation layer (10) formed of a polymer sheet including graphene particles; a first adhesive layer (20) positioned on top of the heat dissipation layer (10); a second adhesive layer (30) positioned on a lower portion of the heat dissipation layer (10); and a first flexible heat dissipation tape (40) positioned on top of the first adhesive layer (20); and a through hole is formed in the heat dissipation layer (10).

First, the heat dissipation layer (10) will be described. The polymer resin included in the heat dissipation layer (10) may be a polymer resin that functions as a matrix for dispersing the graphene particles and prevents the graphene particles from detaching.

The above polymer resin includes at least one of nitrile-butadiene rubber (NBR), an acrylic resin, an epoxy resin, a phenoxy resin, a urethane resin, and a silicone resin. More preferably, the above polymer resin can use nitrile-butadiene rubber (NBR).

In addition, the graphene particles used in the present invention are not particularly limited as long as they are particles of graphene component with excellent thermal conductivity. Graphene particles having various shapes can be used, and any particle containing a graphene component can be used.

It is preferable that the graphene particles are contained in an amount of 230 parts by weight or more based on 100 parts by weight of the polymer resin. If the graphene particles are contained in an amount of less than 230 parts by weight based on 100 parts by weight of the polymer resin, the thermal conductivity properties of the heat-radiating sheet may deteriorate. Preferably, the graphene particles may be contained in an amount of 1800 parts by weight or less based on 100 parts by weight of the polymer resin.

In summary, the heat dissipation layer may include 230 parts by weight or more and 1,800 parts by weight or less of the graphene particles relative to 100 parts by weight of a matrix resin including at least one of nitrile-butadiene rubber (NBR), an acrylic resin, an epoxy resin, a phenoxy resin, a urethane resin, and a silicone resin.

In addition, the particle size of the graphene particles may preferably be 10 ㎛ to 40 ㎛. If the particle size of the graphene particles is less than 10 ㎛, the thermal conductivity characteristics of the heat dissipation sheet may deteriorate, and if the particle size of the graphene particles exceeds 40 ㎛, the processability of the heat dissipation sheet may deteriorate.

As described above, the heat dissipation layer (10) can be formed of a polymer sheet including 230 parts by weight or more of the graphene particles with respect to 100 parts by weight of a polymer resin including nitrile-butadiene rubber (NBR).

Next, the adhesive layer is explained.

The heat dissipation sheet (100) of the present invention includes a first adhesive layer (20) and a second adhesive layer (30).

The above adhesive layers must have excellent elongation, cohesion and adhesive strength to prevent the heat dissipation layer (10) constituting the heat dissipation sheet and the flexible heat dissipation tape (40) from separating from each other even when the heat dissipation sheet is repeatedly folded and/or repeatedly folded under harsh conditions.

The first adhesive layer (20) and the second adhesive layer (30) according to the present invention may have an elongation of 600% or more, preferably 600% to 800%. In the above range, when the heat-radiating sheet is folded, the individual components are not separated from each other, so that the folding performance and folding durability can be excellent.

In addition, the first adhesive layer (20) and the second adhesive layer (30) may have a cohesive force of 3.0 kgf/inch or less, and preferably 2.0 kgf/inch to 2.5 kgf/inch. In the above range, when the heat-radiating sheet is folded, the individual components are not separated from each other, so that the folding performance and folding durability can be excellent.

In addition, the first adhesive layer (20) and the second adhesive layer (30) may have an adhesive strength of 500 gf/inch or more for the adhered components, and preferably 600 gf/inch to 2500 gf/inch. In the above range, when the heat-radiating sheet is folded, the components do not separate from each other, so that the folding performance and folding durability can be excellent.

The first adhesive layer (20) and the second adhesive layer (30) according to the present invention are not particularly limited in type as long as they satisfy the elongation, cohesion, and adhesive strength described above.

Preferably, the first adhesive layer (20) and the second adhesive layer (30) may be formed of an adhesive composition including an acrylic resin, a urethane resin, a silane coupling agent, a fluorine-based surfactant, a curing agent, and a curing accelerator. If necessary, the adhesive composition may further include one or two or more of a moisture-resistant agent, a flame retardant, a thermally conductive filler, and a dispersant.

More preferably, the first adhesive layer (20) and the second adhesive layer (30) may include an acrylic resin, a urethane resin, and an epoxy curing agent.

Next, the first flexible heat-radiating tape (40) included in the heat-radiating sheet (100) of the present invention will be described.

In order to secure better folding performance and folding durability, the heat dissipation sheet (100) according to the present invention has a first flexible heat dissipation tape (40) placed on the upper side of the heat dissipation layer (10).

The first flexible heat-dissipating tape (40) has a heat-dissipating performance to maximize the heat-dissipating effect of the heat-dissipating layer (10), and has a function of supplementing insufficient durability in the folding portion (folding area) of the heat-dissipating sheet and preventing the delamination and tearing of the heat-dissipating layer (10). The first flexible heat-dissipating tape (40) may use a flexible material tape having an elongation of 350% or more and a horizontal thermal conductivity of 9 W/mk or more, and the material is not particularly limited as long as it can satisfy the above-described characteristics. If the elongation of the first flexible heat-dissipating tape (40) is less than 350%, the durability of the heat-dissipating sheet may be reduced, and if the horizontal thermal conductivity of the first flexible heat-dissipating tape (40) is less than 9 W/mk, the thermal diffusion capacity of the heat-dissipating sheet may be reduced.

Preferably, the first flexible heat-dissipating tape (40) may include a urethane-based rubber resin or an acrylic-based rubber resin and may further include a conductive filler. The conductive filler may use conductive particles such as graphite, graphene particles, or carbon black.

As described above, a through hole is formed in the heat dissipation layer (10). The through hole may be formed only in the heat dissipation layer (10), or the through hole may be formed in the entire heat dissipation sheet.

Preferably, the through hole can be formed in a folding area that is folded at an arbitrary angle in the heat dissipation sheet.

In addition, the shape of the above-mentioned through hole is not particularly limited, but may preferably have at least one shape selected from a circle, an oval, a square, a rectangle, an equilateral triangle, a rhombus, a regular pentagon, a regular hexagon, and a star shape.

In addition, it is preferable that the diameter of the through hole is 1 mm to 10 mm, and in this case, when the shape of the through hole has a shape other than circular, the diameter of the through hole may mean the average of the sum of the major and minor axis lengths.

FIG. 2 illustrates a heat dissipation sheet (110) according to another embodiment of the present invention. In the heat dissipation sheet (110) according to another embodiment of the present invention, a second flexible heat dissipation tape (50) and a third adhesive layer (60) may be sequentially positioned below the second adhesive layer (30).

The second flexible heat dissipation tape (50) may be of the same type as the first flexible heat dissipation tape (40) described above. In addition, the third adhesive layer (60) may also be of the same type as the first adhesive layer (20) or the second adhesive layer (30) described above.

Although the present invention has been described above with reference to implementation examples, these are merely examples and do not limit the implementation examples of the present invention. Those skilled in the art to which the embodiments of the present invention pertain will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present invention. For example, each component specifically shown in the implementation examples of the present invention can be modified and implemented. In addition, differences related to such modifications and applications should be interpreted as being included in the scope of the present invention defined in the appended claims.

<Example>

1. Manufacturing of heat dissipation layer

Based on the composition and conditions of Table 1 below, a B-stage heat-radiating layer was manufactured according to examples and comparative examples. The heat-radiating sheet according to the present invention is based on the examples. MEK was used as the solvent. The B-stage heat-radiating layer is hardened through a curing process to become a heat-radiating layer.

division Matrix resin
(weight%) Matrix resin Graphene particles
(weight%) Average particle diameter of graphene particles
(㎛) Dispersant
(weight%) Hardener
(weight%) Example 1 12.0 Acryl 85 25 2.6 0.5 Example 2 15.8 Acryl 81.5 25 2.4 0.3 Example 3 6.7 Acryl 90 25 2.7 0.5 Example 4 9.9 Acryl 83 25 6.6 0.5 Example 5 12.0 Urethane 85 25 2.6 0.5 Example 6 12.0 NBR 85 25 2.6 0.5 Example 7 13.5 Acryl 85 25 1 0.5 Comparative Example 1 11.0 Acryl 85 25 2.6 1.5 Comparative Example 2 37.4 Acryl 60 25 1.8 0.5 Comparative Example 3 12.0 Acryl 85 270 2.6 0.5 Comparative Example 4 1.7 Acryl 95 25 2.9 0.5 Comparative Example 5 12.0 Acryl 85 10 2.6 0.5 Comparative Example 6 14.5 Acryl 85 25 0.0 0.5 Comparative Example 7 1.8 Acryl 85 25 12.8 0.5

Acrylic resin: polyt-butyl acrylate (AK Chemical)

NBR Resin: Nitrile Butadiene Rubber (ARLANXEO)

Urethane resin: Urethane modified copolyester resin (TOYOBO UR-3500)

Graphene particles: Commercial graphene particles EASCHEM ESG-G2

Dispersant: Copolymer of 2-methoxypropyl acetate and 1-methoxy-2-propyl acetate

Hardener: Diphenylmethane diisocyanate

2. Measurement of the properties of the heat dissipation layer

The test results of the heat dissipation layers manufactured from each example and comparative example of Table 1 above are shown in Table 2.

division durability Processability Horizontal thermal conductivity
W/(mK) Example 1 ○ Above 314.9 Example 2 ○ Above 301.5 Example 3 ○ Above 314.3 Example 4 ○ Above 312.8 Example 5 ○ Above 314.3 Example 6 ○ Above 312.9 Example 7 ○ Above 290.3 Comparative Example 1 X Above 312.8 Comparative Example 2 ○ Above 77.5 Comparative Example 3 △ Down 219.7 Comparative Example 4 X Down 235.3 Comparative Example 5 Unrated Down - Comparative Example 6 ○ Down 280.9 Comparative Example 7 X Down 310.1

* Durability Evaluation Method: The durability evaluation method is by folding test. The manufactured heat-insulating sheet was cut into a rectangle with a length of 10.15 cm and a width of 15 cm to manufacture a specimen. The folding test was evaluated at 25℃ using a Stress Free folder opener (Flexigo, Folding Durability Tester, Foldy-10). The specimen was folded in the length direction of the specimen at a folding speed of 43,000 times per day (30 RPM), a radius of curvature (folding angle) of 1.0 mm, and a folding angle of 0° and 181°.

After the folding evaluation, the evaluation results were visually evaluated for the left fold area of the folding part (folding area), the folding part (folding area), and the right fold area of the folding part (folding area). The evaluation was conducted according to the following evaluation criteria.

○: No layering occurs

△: Microcracks occur

X: Layering occurs

* Processability Evaluation Method: Processability evaluation is based on the manufacturing ease judgment method. Processability was evaluated based on sheet forming ability, work time efficiency, etc., which are considered when the worker manufactures the heat-dissipating layer.

* Horizontal thermal conductivity evaluation method: Horizontal thermal conductivity was calculated using the thermal diffusivity of the specimen measured using a measuring device (LFA) and the specific heat and density of the specimen measured separately.

It can be confirmed that the heat dissipation layers according to Examples 1 to 7 did not cause delamination during the folding test and also had excellent processability. In addition, it can be confirmed that the heat dissipation layers according to Examples 1 to 7 all had excellent horizontal thermal conductivity of 290 W/(mk) or more.

In comparison, the heat dissipation layer according to Comparative Example 1 was delaminated during the folding evaluation. In addition, Comparative Example 2 had a horizontal thermal conductivity of only 77.5 due to insufficient graphene particle content.

The heat dissipation layer according to Comparative Example 3 had microcracks during the folding evaluation, and was difficult to sheet, resulting in poor processability.

In addition, Comparative Examples 4 to 7 also had poor processability, and in particular, Comparative Examples 4 and 7 showed delamination during folding evaluation.

In this way, it can be confirmed that the heat dissipation layers according to the embodiments of the present invention have excellent durability and processability and also excellent horizontal thermal conductivity, but it can be confirmed that the heat dissipation layers according to the comparative examples have problems such as insufficient durability, insufficient processability, or relatively low horizontal thermal conductivity.

3. Measurement of properties of heat dissipation layer according to hole formation conditions

For the heat dissipation layer manufactured based on the composition of Example 1 of Table 1, a hole was formed according to the conditions of Table 3 below. The hole was formed in the folding area where the heat dissipation layer is folded.

division Hole cross-section shape Through hole diameter Heat dissipation performance evaluation (△T) durability Before folding After folding Before/after performance difference Example A circle 1 45.8 45.7 -0.1 O Example B circle 2 46.2 46.1 -0.1 O Example C circle 4 46.4 46.5 0.1 O Example D circle 5 46.8 46.6 -0.2 O Example E circle 9 47.3 47.1 -0.2 O Example F circle 10 48.4 48.2 -0.2 O Example G Oval 4 47.1 47.5 0.4 O Example H square 4 47.5 47.6 0.1 O Example I equilateral triangle 4 48.4 48.2 -0.2 O Example J Rhombus 4 48.2 48.1 -0.1 O Example K regular pentagon 4 49.2 49.5 0.3 O Example L Star model 4 47.1 46.9 -0.2 O Comparative Example A Unformed - 44.9 46.3 1.4 X Comparative Example B circle 0.5 45.0 48.1 3.1 X Comparative Example C circle 0.8 45.2 48.6 3.4 △ Comparative Example D circle 13 52.3 52.5 0.2 O Comparative Example E circle 15 55.1 55.0 -0.1 O Comparative Example F +Brother 4 52.8 53.1 0.3 O Comparative Example G X type 4 52.0 53.9 1.9 X Comparative Example H Type A 4 51.7 52.9 1.2 △ Comparative Example I N brother 4 50.6 51.8 1.2 X

* Method for evaluating heat dissipation performance: The heat dissipation layer was cut to 15 cm in length and 2.5 cm in width, and double-sided tape was attached. The prepared sample was attached to a heating block, and the temperature of the heating block was increased to 90℃. Next, the heating block was sealed in a box, stabilized for 10 minutes, and the temperature was measured using an IR camera. The highest temperature (hot spot, Th) and the lowest temperature (cold spot, Tc) parts of the heat dissipation layer were measured, and the thermal diffusivity of the heat dissipation layer was measured by obtaining the temperature difference (△T). The lower △T, the better the thermal diffusivity, indicating better heat dissipation performance.

As shown in the results in Table 3 above, it was confirmed that all of the heat dissipation layers according to the embodiments of the present invention have good heat dissipation performance and also good durability.

In contrast, the heat dissipation layers according to the comparative examples have relatively poor heat dissipation performance, and the folding test shows that delamination or microcracks occur, indicating poor durability. In the case of comparative examples D to F, durability is good, but the heat dissipation performance evaluation results show that the temperature is 51℃ or higher both before and after folding, indicating relatively poor heat dissipation performance.

4. Preparation of adhesive

An adhesive composition was prepared by mixing 100 parts by weight of a thermosetting PSA adhesive resin including an acrylic resin (AK Chemical) and a urethane-modified copolyester resin (TOYOBO UR-3500), 1.0 to 1.5 parts by weight of a silane coupling agent (Dow Corning, Z6106), 0.1 to 1.0 parts by weight of a fluorinated surfactant (3M, FC series surfactant), and 0.01 to 1 part by weight of an epoxy curing agent (AK Chemical, X-500) into ethyl acetate, an organic solvent, and stirring the mixture. An adhesive layer was prepared using the prepared adhesive composition, and the elongation and cohesion were evaluated.

The elongation was evaluated using the Tensile Test (ASTM D 638) method, and the elongation was 600%.

Cohesion was evaluated by the ASTM D 903 method and was 2.5 kgf/inch.

Additionally, the adhesion was evaluated using the ASTM D3330 method and was 1500 gf/inch.

5. Manufacturing of flexible heat dissipation tape

A flexible heat dissipation tape having the characteristics shown in Table 4 below was manufactured.

Similarly, the elongation of the flexible thermal tape was evaluated by the Tensile Test (ASTM D 638) method. In addition, the horizontal thermal conductivity was calculated by the thermal diffusivity of the specimen measured using a measuring device (LFA) and the specific heat and density of the specimen measured separately.

　 Types of fillers Filler content Joo Soo Ji Hardener Elongation (%) Horizontal thermal conductivity Type Diameter (D90,㎛) (W/mK) Manufacturing example 1 Graphene 1 25 5 Urethane series Isocyanate series 580 10 Manufacturing example 2 Graphene 1 25 5 Acryl series Epoxy series 530 10 Manufacturing example 3 Carbon Black 10 5 Urethane series Isocyanate series 600 9 Manufacturing example 4 Carbon Black 10 5 Acryl series Epoxy series 550 9 Manufacturing example 5 Graphene 2 10 5 Urethane series Isocyanate series 450 9 Manufacturing example 6 Graphene 2 10 5 Acryl series Epoxy series 390 9 Manufacturing example 7 Graphene 1 25 4 Urethane series Epoxy series 590 8 Manufacturing example 8 Graphene 1 25 3 Urethane series Epoxy series 600 7 Manufacturing example 9 Graphene 3 270 5 Urethane series Isocyanate series 250 12 Manufacturing example 10 Graphene 3 270 5 Acryl series Epoxy series 230 12

6. Manufacturing of heat-insulating sheets

The adhesive composition was applied to the upper and lower parts of the heat dissipation layer manufactured through Example C of Table 3 to laminate the first adhesive layer and the second adhesive layer, respectively.

The flexible heat-radiating tape manufactured in Manufacturing Example 1 was laminated on top of the first adhesive layer, and the spacing of the holes formed in the folding part of the heat-radiating layer was changed to manufacture heat-radiating sheets of Examples 1 to 5.

Next, Examples 6 to 10 were manufactured in the same manner as Example 2, except that Manufacturing Examples 2 to 6 were used as flexible heat-dissipating tapes, respectively.

In addition, Comparative Examples' 1 and 2 were manufactured in the same manner as Example' 2, except that Manufacturing Examples 7 and 8 were used as flexible heat-dissipating tapes, respectively.

In addition, Comparative Examples' 3 to 4 were manufactured in the same manner as Example' 2, except that Manufacturing Examples 9 and 10 were used as flexible heat-dissipating tapes, respectively.

In addition, Comparative Examples' 5 to 7 were manufactured using the flexible heat dissipation tapes of Manufacturing Examples 1, 4, and 5, respectively, and were manufactured in the same manner as Example '2, except that the spacing of the holes formed in the folding portion of the heat dissipation layer was changed.

7. Evaluation of the properties of heat-radiating sheets according to the 'Examples' and 'Comparative Examples'

The physical properties of the heat-dissipating sheets according to the manufactured examples and comparative examples were evaluated as follows, and the results are shown in Table 5 below.

　 Distance between holes in folding part (mm) Thermal diffusivity appearance Th Tc △T Horizontal judgment horizontality
direction Folding area
durability △T(%) Example' 1 2 80.1 43.5 36.6 45.7 ○ ○ Example' 2 4 80.5 43.6 36.9 45.8 ○ ○ Example' 3 6 80.3 43.8 36.5 45.5 ○ ○ Example' 4 8 79.9 44.2 35.7 44.7 ○ ○ Example' 5 10 81.1 44.5 36.6 45.1 ○ ○ Example' 6 4 81.9 42.1 39.8 48.6 ○ ○ Example' 7 4 78.1 41.8 36.3 46.5 ○ ○ Example' 8 4 77.2 40.9 36.3 47 ○ ○ Example' 9 4 82.4 43.9 38.5 46.7 ○ ○ Example' 10 4 82.8 44.1 38.7 46.7 ○ ○ Comparative Example' 1 4 81.5 36.5 45 55.2 X ○ Comparative Example' 2 4 82.7 37.4 45.3 54.8 △ ○ Comparative Example' 3 4 82.1 43.1 39 47.5 ○ X Comparative Example' 4 4 82.5 43.4 39.1 47.4 O X Comparative Example' 5 1 79.8 43.2 36.6 45.9 O X Comparative Example' 6 11 80.6 44.2 36.4 45.2 O △ Comparative Example' 7 12 79.9 44.5 35.4 44.3 O △

(1) Appearance (Folding area durability): The manufactured composite heat-insulating sheet was cut into a rectangle with a length of 10.15 cm and a width of 15 cm to manufacture a specimen. The folding test was evaluated at 25℃ using a Stress Free folder opener (Flexigo, Folding Durability Tester, Foldy-10). The specimen was folded in the length direction of the specimen at a folding speed of 43,000 times per day (30 RPM), a radius of curvature (folding angle) of 1.0 mm, and a folding angle of 0° and 181°, respectively.

After the folding evaluation, the evaluation results were visually evaluated for the left fold area of the folding part (folding area), the folding part (folding area), and the right fold area of the folding part, respectively. The evaluation was conducted according to the following evaluation criteria.

○: No layering occurs

△: Microcracks occur

ⅹ: Layering occurs

(2) Thermal diffusivity: The composite heat-dissipating sheet was cut to 15 cm in length and 2.5 cm in width, and double-sided tape was attached. The prepared sample was attached to a heating block, and the temperature of the heating block was increased to 90℃. Next, the heating block was sealed in a box, stabilized for 10 minutes, and the temperature was measured using an IR camera. The highest temperature (hot spot, Th) and the lowest temperature (cold spot, Tc) parts of the composite sheet were measured, and the thermal diffusivity of the composite sheet was measured by obtaining the temperature difference (△T). The lower △T, the better the thermal diffusivity, indicating better heat dissipation performance. The thermal diffusivity was evaluated according to the following criteria.

○: When the temperature difference △T between Th and Tc is less than 50% of the Th temperature

△: When the temperature difference between Th -Tc △T is 50% or more and less than 55% of the Th temperature

ⅹ: When the temperature difference △T between Th -Tc is 55% or more of the Th temperature

As shown in Table 2 above, it can be seen that the heat dissipation sheet of the present invention has excellent thermal diffusion and also excellent folding area durability.

On the other hand, the comparative examples having different properties of the flexible heat dissipation tape compared to the examples had the following problems. First, Comparative Examples 1 and 2 had poor thermal diffusivity because the horizontal thermal conductivity of the heat dissipation tape was less than 9 (see Table 4). Next, Comparative Examples 3 and 4 had poor elongation of the heat dissipation tape because the elongation of the heat dissipation tape was less than 350, which confirmed that the durability of the folding area was poor. In addition, Comparative Examples 5, 6, and 7 had relatively poor durability in the folding area because the distance between the holes in the folding area of the heat dissipation layer was relatively wide. More specifically, when the distance between the holes is 1 mm or less, the folding area cannot withstand repeated folding tests because there are too many holes in the folding area, and delamination occurs in the folding area. In addition, when the distance between the holes exceeds 10 mm, the flexibility of the folding area is reduced because there are too few holes in the folding area, and microcracks occur in the folding area during repeated folding tests.

Although the present invention has been described as above, it is obvious that the present invention is not limited to the embodiments disclosed in this specification, and various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention. In addition, even if the effects according to the configuration of the present invention were not explicitly described while describing the embodiments of the present invention, it is natural that the effects that can be predicted by the corresponding configuration should also be recognized.

10: Heat dissipation layer
20: First adhesive layer
30: Second adhesive layer
40: 1st flexible heat dissipation tape
50: 2nd flexible heat dissipation tape
60: Third adhesive layer
100, 110 : Heat dissipation sheet

Claims (14)

A heat dissipation layer formed of a polymer sheet containing graphene particles;
A first adhesive layer positioned on the upper part of the heat dissipation layer;
a second adhesive layer located below the heat dissipation layer; and
A first flexible heat dissipation tape positioned on the upper part of the first adhesive layer;
A through hole is formed in the above heat dissipation layer,
The above first flexible heat dissipation tape
The elongation is 350% or more and the horizontal thermal conductivity is 9 W/mk or more.
Heat dissipation sheet.
In the first paragraph,
Below the second adhesive layer
A second flexible heat dissipation tape and a third adhesive layer are further formed.
Heat dissipation sheet.
In the first paragraph,
The above heat dissipation layer is a polymer sheet including 230 to 1,800 parts by weight of the graphene particles relative to 100 parts by weight of a matrix resin including at least one of nitrile-butadiene rubber (NBR), an acrylic resin, an epoxy resin, a phenoxy resin, a urethane resin, and a silicone resin.
heat dissipation sheet
In the first paragraph,
The above graphene particles have a particle size of 10 μm to 40 μm.
heat dissipation sheet
In the first paragraph,
The above first adhesive layer and second adhesive layer
Containing acrylic resin, urethane resin and epoxy curing agent
Heat dissipation sheet.
In the first paragraph,
The above first flexible heat dissipation tape
Urethane rubber resin or acrylic rubber resin and
Containing conductive filler
Heat dissipation sheet.
In the second paragraph,
The above second flexible heat dissipation tape
Urethane rubber resin or acrylic rubber resin and
Containing a conductive filler,
The third adhesive layer above
Containing acrylic resin, urethane resin and epoxy curing agent
Heat dissipation sheet.
delete In the second paragraph,
The above second flexible heat dissipation tape
The elongation is 350% or more and the horizontal thermal conductivity is 9 W/mk or more.
Heat dissipation sheet.
In the first paragraph,
The above heat dissipation sheet
Having a folding area that can be folded at any angle
Heat dissipation sheet. In Article 10,
The above through hole
formed in the above folding area
Heat dissipation sheet.
In the first paragraph,
The above through hole
Having at least one shape selected from a circle, an oval, a square, a rectangle, an equilateral triangle, a rhombus, a regular pentagon, a regular hexagon, and a star shape.
Heat dissipation sheet.
In the first paragraph,
The diameter of the above through hole is 1 mm to 10 mm,
If the shape of the above through hole has a shape other than circular, the diameter of the above through hole is the average of the sum of the major and minor axis lengths.
Heat dissipation sheet.
A display component comprising a heat dissipation sheet according to any one of claims 1 to 7 and claims 9 to 13.