KR20230049859A - Adhesive sheet and antenna structure including the same - Google Patents

Abstract

Embodiments of the present invention provide an adhesive sheet, an antenna structure including the same, and an image display device including the same. The adhesive sheet includes an adhesive layer, which has a dielectric loss tangent at 28 GHz measured at a thickness of 100㎛ greater than 0 and less than or equal to 0.01, a storage modulus at 25℃ of 10 to 50 kPa, a first modulus ratio of 1.5 to 4.0, and a second modulus ratio of 1.0 to 3.5.

Description

Adhesive sheet and antenna structure including the same {ADHESIVE SHEET AND ANTENNA STRUCTURE INCLUDING THE SAME}

The present invention relates to an adhesive sheet and an antenna structure including the same. More particularly, it relates to a pressure-sensitive adhesive sheet including an acrylic copolymer and an antenna structure including the same.

Recently, various information processing functions have been combined with image display devices combined with communication functions, such as smart phones. Accordingly, structures such as a touch panel and an antenna may be included in one image display device along with an optical layer (eg, a polarizer, a retardation plate, etc.) for implementing an image.

Therefore, an adhesive layer or adhesive sheet is used to laminate the above-described optical layer and structures on the display panel. For example, an adhesive sheet may be used to attach the antenna to the display panel.

Recently, as high-frequency or ultra-high frequency antennas are employed in image display devices, antenna radiation characteristics can be easily disturbed by dielectric characteristics around the antenna. For example, when the dielectric constant of the adhesive sheet is high, dielectric loss or signal loss of the antenna may occur, and impedance characteristics of the set antenna may be disturbed.

In addition, as flexible displays that can be folded or bent have recently been developed, an adhesive layer or adhesive sheet applied to an image display device also needs to be designed to have improved flexibility.

Therefore, it is necessary to develop an adhesive sheet that can be applied to a flexible display and has dielectric properties suitable for high frequency/ultra high frequency communication.

For example, Korean Patent Publication No. 10-2021-0102035 discloses a pressure-sensitive adhesive composition for an optical film containing a (meth)acrylic acid ester copolymer, but does not consider the above-described dielectric properties.

Korean Patent Publication No. 10-2021-0102035

One object of the present invention is to provide a pressure-sensitive adhesive sheet having improved dielectric properties and flexibility.

One object of the present invention is to provide an antenna structure including an adhesive sheet having improved dielectric properties and flexibility.

One object of the present invention is to provide an image display device to which the pressure-sensitive adhesive sheet is applied.

1. The dielectric loss tangent at 28 GHz measured at a thickness of 150 μm is greater than 0 and less than or equal to 0.01, and the storage modulus at 25 ° C is 10 to 50 kPa;

A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer having a first modulus ratio defined by the following formula 1 of 1.5 to 4.0 and a second modulus ratio defined by the following formula 2 of 1.0 to 3.5:

[Equation 1]

First modulus ratio = A/B

[Equation 2]

Second modulus ratio = B/C

(In formulas 1 and 2, A is the storage modulus at -20 ° C of the pressure-sensitive adhesive layer, B is the storage modulus at 25 ° C of the pressure-sensitive adhesive layer, C is the storage modulus at 80 ° C of the pressure-sensitive adhesive layer).

2. The pressure-sensitive adhesive sheet according to 1 above, wherein the pressure-sensitive adhesive layer includes an acrylic copolymer polymerized from a monomer blend including a first acrylate-based monomer having less than 18 carbon atoms and a second acrylate-based monomer having 18 or more carbon atoms.

3. The pressure-sensitive adhesive sheet according to 2 above, wherein the ratio of the weight of the second acrylate-based monomer to the weight of the first acrylate-based monomer in the monomer blend is 0.2 to 9.

4. The pressure-sensitive adhesive sheet according to 2 above, wherein the monomer blend further includes a polar monomer containing a carboxyl group or an amide group.

5. In the above 4, the monomer blend is based on 100 parts by weight of the monomer blend, 10 to 75 parts by weight of the first acrylate-based monomer, 20 to 85 parts by weight of the second acrylate-based monomer, and 0.5 parts by weight of the polar monomer to 10 parts by weight, the pressure-sensitive adhesive sheet.

6. The pressure-sensitive adhesive sheet according to 5 above, wherein the amount of the hydroxyl group-containing monomer is 2 parts by weight or less based on 100 parts by weight of the monomer blend.

7. In the above 2, the second acrylate-based monomer is 2-decyl-1-tetradecanyl (meth) acrylate (2-decyl-1-tetradecanyl (meth) acrylate) or stearyl (meth) acrylate A pressure-sensitive adhesive sheet comprising a.

8. The pressure-sensitive adhesive sheet according to 1 above, wherein the dielectric loss tangent of the pressure-sensitive adhesive layer is 0.005 or less.

9. The pressure-sensitive adhesive sheet according to 1 above, wherein the pressure-sensitive adhesive layer has a storage modulus at 25° C. of 20 to 40 kPa.

10. The pressure-sensitive adhesive sheet according to 1 above, further comprising a protective film formed on at least one surface of the pressure-sensitive adhesive layer.

11. Antenna dielectric layer; an antenna electrode layer disposed on an upper surface of the antenna dielectric layer; and the adhesive sheet of the above-described embodiments attached on the lower surface of the antenna dielectric layer.

12. display panel; and an antenna structure according to the above-described embodiments attached on the display panel.

The pressure-sensitive adhesive sheet according to embodiments of the present invention may have a room temperature modulus within a predetermined range and a modulus ratio according to temperature. Accordingly, the adhesive sheet has improved folding characteristics and can provide stable flexibility and bending characteristics when applied to a flexible display.

According to example embodiments, the pressure-sensitive adhesive sheet may have a dielectric loss tangent within a predetermined range. Accordingly, while having improved folding characteristics, antenna gain and radiation characteristics due to the adhesive sheet may not be deteriorated.

Accordingly, an antenna structure or flexible display having improved flexibility while maintaining high frequency/ultra high frequency antenna radiation reliability may be implemented through the adhesive sheet.

In example embodiments, the pressure-sensitive adhesive sheet includes a copolymer of an acrylic monomer, and the acrylic monomer may include both an acrylate monomer having 18 or more carbon atoms and an acrylate monomer having less than 18 carbon atoms.

Accordingly, as described above, it is possible to effectively implement improved flexibility while reducing dielectric loss of the adhesive sheet.

1 is a schematic cross-sectional view illustrating an adhesive sheet according to exemplary embodiments.
2 and 3 are schematic cross-sectional and plan views illustrating an antenna structure and an image display device according to exemplary embodiments, respectively.

Embodiments of the present invention provide a pressure-sensitive adhesive sheet having predetermined dielectric and modulus characteristics.

In addition, embodiments of the present invention provide an antenna structure and an image display device to which the adhesive sheet is applied.

Hereinafter, embodiments of the present invention will be described in detail.

<Adhesive Sheet>

1 is a schematic cross-sectional view illustrating an adhesive sheet according to exemplary embodiments.

Referring to FIG. 1 , the pressure-sensitive adhesive sheet 100 may include a pressure-sensitive adhesive layer 110 . The adhesive sheet 100 may further include a protective film formed on at least one surface of the adhesive layer 110 .

According to exemplary embodiments, a dielectric loss tangent (dielectric loss or loss tangent; Df) value measured at a thickness of 150 μm and 28 GHz of the pressure-sensitive adhesive layer 110 may be 0.01 or less. For example, the dielectric loss tangent of the adhesive layer 110 may exceed 0 and be 0.01 or less.

As the dielectric loss of the adhesive layer 110 is suppressed within the above range, the dielectric characteristics of the dielectric layer of the antenna due to the adhesive layer 110 may not be varied or disturbed.

Preferably, the dielectric loss tangent of the pressure-sensitive adhesive layer 110 may exceed 0 and be 0.005 or less, more preferably 0.003 or less, and still more preferably 0.002 or less.

The modulus of elasticity of the pressure-sensitive adhesive layer 110 may be designed in consideration of folding stability of an antenna structure or an image display device including the pressure-sensitive adhesive layer 110 .

According to exemplary embodiments, the storage modulus of the pressure-sensitive adhesive layer 110 at 25° C. may be 10 to 50 kPa. Mechanical stability may be maintained while imparting sufficient folding characteristics through the pressure-sensitive adhesive layer 110 within the above range.

In one embodiment, the storage modulus of the pressure-sensitive adhesive layer 110 at 25° C. may be 20 to 40 kPa, preferably 20 to 30 kPa.

According to exemplary embodiments, the first modulus ratio defined by Equation 1 below of the pressure-sensitive adhesive layer 110 may be 1.5 to 4.0.

[Equation 1]

First modulus ratio = A/B

In Equation 1, A is the storage modulus of the pressure-sensitive adhesive layer 110 at -20 ° C, and B is the storage modulus of the pressure-sensitive adhesive layer 110 at 25 ° C.

According to exemplary embodiments, the second modulus ratio defined by Equation 2 below of the pressure-sensitive adhesive layer 110 may be 1.0 to 3.5.

[Equation 2]

Second modulus ratio = B/C

In Equation 1, B is the storage modulus of the pressure-sensitive adhesive layer 110 at 25 ° C, and C is the storage modulus of the pressure-sensitive adhesive layer 110 at 80 ° C.

As the pressure-sensitive adhesive layer 110 is formed to satisfy the ranges of the first and second modulus ratios, sufficient flexibility and folding characteristics are maintained over a wide temperature range, and mechanical defects such as cracks and peeling are suppressed during folding/bending. can do. Therefore, while maintaining sufficient mechanical strength and impact resistance of the pressure-sensitive adhesive layer 110, defects such as cracks may not be caused even under harsh bending conditions.

For example, the pressure-sensitive adhesive layer 110 may not be cracked or peeled even when it is bent 10,000 times or more at a rate of 25 times per minute with a radius of curvature of 2 mm at -30°C.

In one embodiment, the first modulus ratio of the pressure-sensitive adhesive layer 110 may be 2 to 3.5, preferably 2.4 to 3.3. In one embodiment, the second modulus ratio of the pressure-sensitive adhesive layer 110 may be 1.5 to 3.0, preferably 1.8 to 2.5.

The pressure-sensitive adhesive layer 110 may include an acrylic copolymer. For example, the pressure-sensitive adhesive layer 110 may be formed using a pressure-sensitive adhesive composition containing the acrylic copolymer.

The acrylic copolymer may be prepared from a monomer blend or monomer syrup in which a plurality of monomers are mixed.

The monomer blend may include a first acrylate-based monomer having less than 18 carbon atoms and a second acrylate-based monomer having 18 or more carbon atoms.

As non-limiting examples of the first acrylate-based monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth )acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (metha)acrylate ) Acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isobornyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate rate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-pentafluorooctyl acrylate, 2-ethylhexyldiglycol acrylate and the like. These may be used alone or in combination of two or more.

As a non-limiting example of the second acrylate-based monomer, 2-decyl-1-tetradecanyl (meth)acrylate, stearyl (meth)acrylate, etc. can be heard These may be used alone or in combination of two or more.

As used herein, the term "(meth)acryl-" is used to encompass both "acryl-" and "methacryl-".

According to exemplary embodiments, as the second acrylate-based monomer having a relatively large number of carbon atoms and a large molecular length is used, polarization characteristics of the pressure-sensitive adhesive layer 110 may be reduced. Accordingly, it is possible to effectively reduce the dielectric loss tangent while lowering the dielectric constant of the pressure-sensitive adhesive layer 110 .

In addition, as the first acrylate-based monomer is used together with the second acrylate-based monomer, the polarity in the monomer blend is increased to improve cohesion. Accordingly, the folding characteristics of the pressure-sensitive adhesive layer 110 may be supplemented or enhanced.

The contents of the first acrylate-based monomer and the second acrylate-based monomer may be controlled by considering the aforementioned dielectric properties and folding properties together.

In some embodiments, the ratio of the weight of the second acrylate-based monomer to the weight of the first acrylate-based monomer may be about 0.2 to 9.

Preferably, in consideration of implementing sufficient mechanical stability during folding of the pressure-sensitive adhesive layer 110, the ratio of the weight of the second acrylate-based monomer to the weight of the first acrylate-based monomer is 0.2 to 1, preferably 0.3 or more. and less than 1.

In some embodiments, the monomer blend may further include a polar monomer containing a carboxyl group or an amide group. The polar monomer is added to further enhance the cohesive strength of the copolymer, and mechanical stability of the adhesive layer 110 may be additionally improved upon folding.

Examples of the polar monomer containing a carboxyl group include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, isocrotonic acid, maleic acid, itaconic acid, and fumaric acid.

Examples of polar monomers containing an amide group include (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxy methyl (meth)acrylamide, N-part Toxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, etc. are mentioned.

In some embodiments, in 100 parts by weight of the monomer blend, 10 to 75 parts by weight of the first acrylate-based monomer, 20 to 85 parts by weight of the second acrylate-based monomer, and 0.5 to 10 parts by weight of the polar monomer. can be included

In some embodiments, increasing the amount of hydroxyl groups in a monomer may increase permittivity or dielectric loss according to an increase in polarization. Therefore, the amount of the hydroxyl group-containing monomer in 100 parts by weight of the monomer blend may be reduced to 2 parts by weight or less, preferably 1 part by weight or less.

In one embodiment, a hydroxyl group-containing monomer may not be included in the monomer blend.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. Acrylates, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methylacrylate, etc. can be heard

The pressure-sensitive adhesive composition may further include a photopolymerization initiator or a thermal curing agent for improving crosslinkability or curability.

The photopolymerization initiator is, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, 1-hydroxycyclohexyl -1-phenylmethanone, hydroxydimethylacetophenone, dimethylaminoacetophenone, dimethoxy-2-phenylacetophenone, 3-methylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2- Diethoxy-2-phenylacetophenone, 4-chlorocetophenone, 4,4-dimethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-hydroxycyclophenylketone , 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, oligo[2-hydroxy-2-methyl-1 -(4-(1-methylvinyl)phenyl)propanone], 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4 ,4-diaminobenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone Quinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, diphenylketonebenzyl Dimethylketal, acetophenonedimethylketal, p-dimethylaminobenzoic acid ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO), fluorene, triphenylamine, carbazole, azobisisobutyronitrile (AIBN ) and the like. These can be used individually or in combination of 2 or more types.

In some embodiments, the photopolymerization initiator may be included in an amount of 0.01 to 3 parts by weight, preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer.

The thermal curing agent may, for example, enhance the cohesive force of the pressure-sensitive adhesive composition by appropriately crosslinking the acrylic copolymer, and may include, for example, an isocyanate-based crosslinking agent.

The isocyanate-based crosslinking agent is, for example, tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, isophorone diisocyanate, tetra Methyl xylene diisocyanate, naphthalene diisocyanate, isocyanurate trimer, etc. are mentioned.

The heat curing agent may be included in an amount of 0.1 to 1 part by weight, preferably 0.1 to 0.5 part by weight, based on 100 parts by weight of the acrylic copolymer.

In some embodiments, the pressure-sensitive adhesive composition may include antioxidants, corrosion inhibitors, leveling agents, surface lubricants, antifoaming agents, fillers, plasticizers, light stabilizers, You may further contain additives, such as a reaction initiator and a solvent.

Referring back to FIG. 1 , the pressure-sensitive adhesive sheet 100 may further include a protective film formed on the surface of the pressure-sensitive adhesive layer 110 .

For example, the pressure-sensitive adhesive sheet 110 may include a first protective film 120 and a second protective film 130 respectively formed on the lower and upper surfaces of the pressure-sensitive adhesive layer 110 .

The first protective film 120 may be provided as a base film for forming the pressure-sensitive adhesive layer 110 . The second protective film 130 may be provided as a release film for attaching the pressure-sensitive adhesive layer 110 to an object.

In some embodiments, the first protective film 120 may also be provided as a release film. In this case, the adhesive sheet 100 may be provided as a double-sided adhesive sheet.

The first protective film 120 and the second protective film 130 may be formed of, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate; polyimide resin; acrylic 　resin; styrene-based resins such as polystyrene and acrylonitrile-styrene; polycarbonate 　 resin; polylactic acid 　resin; polyurethane 　 resin; polyolefins and resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; vinyl-based resins such as polyvinyl chloride and polyvinylidene chloride; polyamide 　 resin; sulfone-based resin; polyether-ether ketone-based resin; An allylate-based resin or the like may be included.

<Antenna structure and image display device>

Embodiments of the present invention provide an antenna structure and an image display device including the above-described adhesive sheet.

2 and 3 are schematic cross-sectional and plan views respectively illustrating an antenna structure and an image display device according to exemplary embodiments.

Referring to FIGS. 2 and 3 , the antenna structure 300 may include an antenna electrode layer 160, an antenna dielectric layer 150, and an adhesive sheet 100 according to the above-described exemplary embodiments.

The antenna electrode layer 160 may be formed on the antenna dielectric layer 150 . As shown in FIG. 3 , the antenna electrode layer 160 may include an antenna unit AU, and a plurality of antenna units AU may be arranged on the antenna dielectric layer 150 .

The antenna unit AU may include a radiator 162 , a transmission line 164 and a signal pad 166 . The signal pad 166 may be connected to the antenna driving IC chip through, for example, a flexible printed circuit board (not shown). Accordingly, power supply and signal transmission may be performed to the radiator 162 through the transmission line 164 .

A pair of ground pads 168 may be disposed around the signal pad 166 with the signal pad 166 interposed therebetween.

According to example embodiments, high-frequency or ultra-high frequency communication may be performed through the radiator 162 , for example, in a band of 5 GHz or more, 10 GHz or more, or 20 GHz or more.

The antenna dielectric layer 150 may include an insulating material having dielectric characteristics for realizing the high frequency/ultra high frequency radiation characteristics.

For example, the adhesive sheet 100 may be attached to the lower surface of the antenna dielectric layer 150 after the first protective film 130 is removed. Accordingly, the adhesive layer 110 may directly contact the lower surface of the antenna dielectric layer 150 .

The image display device 400 may include a display panel 200 and an antenna structure 300 .

The display panel 200 may include a pixel electrode 210, a pixel defining layer 220, a display layer 230, a counter electrode 240, and an encapsulation layer 250 disposed on a panel substrate 205. can

A pixel circuit including a thin film transistor (TFT) may be formed on the panel substrate 205 , and an insulating film covering the pixel circuit may be formed. The pixel electrode 210 may be electrically connected to, for example, a drain electrode of a TFT on the insulating film.

The pixel defining layer 220 may be formed on the insulating layer to expose the pixel electrode 210 to define a pixel area. A display layer 230 is formed on the pixel electrode 210 , and the display layer 230 may include, for example, a liquid crystal layer or an organic emission layer.

A counter electrode 240 may be disposed on the pixel defining layer 220 and the display layer 230 . The counter electrode 240 may be provided as, for example, a common electrode or cathode of an image display device. An encapsulation layer 250 for protecting the display panel 200 may be stacked on the opposite electrode 240 .

The antenna structure 300 may be attached on the display panel 200 through the adhesive sheet 100 . For example, after removing the first protective film 120 , the antenna structure 300 may be attached to the display panel 200 through the adhesive layer 110 .

In some embodiments, the touch sensor layer 260 may be stacked on the display panel 200 . For example, the touch sensor layer 260 may be attached to the encapsulation layer 250 of the display panel 200 through the first adhesive layer 50 .

In some embodiments, a polarization layer 270 may be stacked on the touch sensor layer 260 . For example, the polarization layer 270 may be stacked on the touch sensor layer 260 through the second adhesive layer 60 .

In some embodiments, the antenna structure 300 may be stacked on the polarization layer 270 . For example, the first protective film 120 may be removed and the pressure-sensitive adhesive layer 110 may be attached on the polarization layer 270 .

A cover window 280 may be stacked on the antenna structure 300 . For example, the cover window 280 may be attached to the antenna structure 300 through the third point adhesive layer 70 .

As described above, the antenna structure 300, the polarization layer 270, and the touch sensor layer 260 may be sequentially disposed from the user's viewing side. Alternatively, the antenna structure 300 may be disposed under the touch sensor layer 260 or may be disposed between the polarization layer 270 and the touch sensor layer 260 .

As shown in FIG. 3 , the image display device 400 may include a display area 410 and a peripheral area 420 . The peripheral area 420 may correspond to a bezel area or a light blocking area (non-display area).

The antenna structure 300 may be attached to the image display device 400 using the adhesive sheet 100 so that the radiator 162 overlaps the display area 410 in the form of a patch, for example.

As described above, the adhesive sheet 100 may have reduced dielectric loss and improved folding characteristics. Accordingly, high frequency/ultra high frequency radiation characteristics of the radiator 162 or the antenna unit AU can be promoted and signal loss can be suppressed. In addition, it can be easily inserted in the form of a patch through folding/bending through the peripheral area 420 of the image display device 400 .

Hereinafter, experimental examples including preferred examples and comparative examples are presented to aid understanding of the present invention, but these examples are only illustrative of the present invention and do not limit the scope of the appended claims, and It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and scope of the technical idea, and it is natural that these changes and modifications fall within the scope of the appended claims.

Preparation Example: Preparation of acrylic copolymer

Preparation Example 1

A monomer blend containing 50 parts by weight of 2-ethylhexyl acrylate (2-EHA), 45 parts by weight of 2-decyl-1-tetradecenyl acrylate (DTDA), and 5 parts by weight of acrylic acid (AA) is added to a 1L reactor. After that, 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was purged for 1 hour to remove oxygen, and the temperature was maintained at 80°C. After uniformly mixing the monomer mixture, 0.1 part by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and the reaction was performed for 8 hours to prepare an acrylic copolymer (weight average molecular weight: 950,000, PDI). 4.1)

Preparation Example 2-13

In the same manner as in Preparation Example 1, an acrylic copolymer was prepared by changing the monomer components and contents (parts by weight) as shown in Table 1 below.

primary acrylate second acrylate polar monomer hydroxyl group monomer Molecular Weight
(*10 ⁴ ) EHA EHDG-AT DTDA DTDMA SA AA DMAA 2-HEA 4-HBAs manufacturing example
One 50 - 45 - - 5 - - - 95 Preparation Example 2 - 50 - 45 - 5 - - - 72 Preparation Example 3 - 50 - - 45 5 - - - 82 Production Example 4 50 - 48 - - - - - 2 93 Preparation Example 5 10 - 85 - - 5 - - - 75 Preparation Example 6 - 70 25 - - 5 - - - 77 Preparation Example 7 50 - 45 - - - 5 - - 101 Preparation Example 8 95 - - - 5 - - - 110 Production Example 9 95 - - - - - 5 - 107 Production Example 10 - - 25 70 - 5 - - 76 Preparation Example 11 70 20 - - 5 - 5 - 85 Production Example 12 95 - - - - - - 5 102 Preparation Example 13 - - 95 - - - - - 5 66

The specific components listed in Table 1 are as follows.

EHA: 2-Ethylhexylacrylate (Sigma Aldrich)

EHDG-AT: 2-Ethyl hexyl diglycol acrylate (Kongyeongsa)

DTDA: 2-decyl-1-tetradecanyl acrylate (2-decyl-1-tetradecanyl acrylate, Public Corporation)

DTDMA: 2-decyl-1-tetradecanyl methacrylate (2-decyl-1-tetradecanyl methacrylate, Public Corporation)

SA: stearyl acrylate (Kongyeongsa)

AA: Acrylic acid (Sigma Aldrich)

DMAA: N,N-dimethylacrylamide (Sigma Aldrich)

2-HEA: 2-hydroxyethyl acrylate (Sigma Aldrich)

4-HBA: 4-hydroxybutyl acrylate (Sigma Aldrich)

Experimental example

As shown in Tables 2 and 3 using the acrylic copolymer synthesized in the above Preparation Examples, adhesive compositions according to Examples and Comparative Examples were prepared. The pressure-sensitive adhesive composition was applied on a 50um release film coated with a silicone release agent to a thickness of 100 μm, dried at 110° C. for 5 minutes, and then the release film was laminated to form an adhesive sheet.

1) Measurement of storage modulus

For each of the pressure-sensitive adhesive sheets of Examples and Comparative Examples, the storage modulus at 25°C was measured using a viscoelasticity measuring device (MCR-301, Anton Paar). Specifically, the size of the pressure-sensitive adhesive sheet was cut to a length of 30 mm × width of 30 mm, the release film attached to one side of the cut pressure-sensitive adhesive sheet was removed, and then bonded to a glass substrate. Then, while attached to the measuring tip, the storage modulus was measured under conditions of a frequency of 1.0 Hz, a strain of 2%, and a heating rate of 5 °C/min in a temperature range of -20 to 100 °C. At this time, the measured values at -20 ° C, 25 ° C and 80 ° C were read, respectively, and the modulus ratios according to Equations 1 and 2 were calculated.

2) Dielectric loss tangent measurement

The dielectric loss tangent of each of the pressure-sensitive adhesive sheets of Examples and Comparative Examples was measured at 25° C. using a permittivity measuring device (Anritus Co., product name MS46522B). Specifically, a 150 μm adhesive sheet from which the release film was removed was laminated between 40 μm COP films (Zeonor), and cut into a size of 30 mm in length × 70 mm in width.

The cut adhesive sheet was put into the probe of the measuring equipment to measure the dielectric loss tangent (Df) value at 28 GHz.

<Evaluation Criteria>

◎: 0.005 or less

○: more than 0.005 and less than 0.01

×: greater than 0.01

3) Evaluation of folding characteristics

The pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples was bonded to 50um PET to prepare a 20mm×100mm sample. The sample was fixed to a flexural evaluation device (COVOTECH, CFT-720C), and folding was evaluated at -30°C under conditions of folding 25 times per minute, holding 0.2 seconds after folding once, and curvature radius of 2 mm. The number of times of folding that causes defects such as breakage, lifting, and peeling at the folding site was measured and the folding characteristics were evaluated as follows.

<Evaluation Criteria>

◎: No defects when folding more than 30,000 times

○: Defect occurs in the range of 10,000 to 30,000 times of folding

×: Defect occurs when the number of folding is less than 10,000 times

The evaluation results are shown in Table 2 and Table 3 below. In Tables 2 and 3, TDI-based Coronate-L (Nippon Urethane) was used as a crosslinking agent.

division Example
One Example
2 Example
3 Example
4 Example
5 Example
6 Example
7 adhesive
Furtherance copolymer type manufacturing example
One manufacturing example
2 manufacturing example
3 manufacturing example
4 manufacturing example
5 manufacturing example
6 manufacturing example
7 parts by weight 100 100 100 100 100 100 100 cross-linking agent parts by weight 0.3 0.3 0.3 0.3 0.3 0.3 0.3 modulus of elasticity 25℃(kPa) 32 34 35 31 22 25 32 first modulus
Ratio (Equation 1) 2.8 3.2 2.9 3.1 2.4 3.3 2.8 Second modulus ratio (Equation 2) 1.8 2.5 1.8 1.9 1.6 2.5 2.4 Dielectric loss tangent (Df) ○ ◎ ○ ○ ◎ ○ ◎ folding characteristics ◎ ◎ ◎ ◎ ○ ◎ ◎

division comparative example
One comparative example
2 comparative example
3 comparative example
4 comparative example
5 comparative example
6 comparative example
7 adhesive
Furtherance copolymer type manufacturing example
8 manufacturing example
9 manufacturing example
10 manufacturing example
11 manufacturing example
9 manufacturing example
12 manufacturing example
13 parts by weight 100 100 100 100 100 100 100 cross-linking agent parts by weight 0.3 0.3 0.3 0.3 3.0 3.0 0.3 modulus of elasticity 25℃(kPa) 35 32 51 27 31 30 9 first modulus
Ratio (Equation 1) 3.2 2.8 4.3 3.9 1.4 1.6 2.5 Second modulus ratio (Equation 2) 2.2 2.0 3.2 3.6 1.1 0.9 2.1 Dielectric loss tangent (Df) × × ◎ ○ × × ○ folding characteristics ◎ ◎ × × × × ×

Referring to Tables 2 and 3, in the case of the adhesive sheets of the examples, the yarns having a low dielectric loss tangent satisfies the ranges of the storage modulus and modulus ratio described above. Accordingly, excellent durability was provided even in folding at severe low temperatures.

100: adhesive sheet 110: adhesive layer
120: first protective film 130: second protective film
150: antenna dielectric layer 160: antenna electrode layer
162 emitter 164 transmission line
166: signal pad 200: display panel
260: touch sensor layer 270: polarization layer
280: cover window 300: antenna structure
400: image display device

Claims (12)

The dielectric loss tangent at 28 GHz measured at a thickness of 150 μm is greater than 0 and less than 0.01,
The storage modulus at 25 ° C is 10 to 50 kPa,
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer having a first modulus ratio defined by the following formula 1 of 1.5 to 4.0 and a second modulus ratio defined by the following formula 2 of 1.0 to 3.5:
[Equation 1]
First modulus ratio = A/B
[Equation 2]
Second modulus ratio = B/C
(In formulas 1 and 2, A is the storage modulus at -20 ° C of the pressure-sensitive adhesive layer, B is the storage modulus at 25 ° C of the pressure-sensitive adhesive layer, C is the storage modulus at 80 ° C of the pressure-sensitive adhesive layer).
The pressure-sensitive adhesive sheet of claim 1, wherein the pressure-sensitive adhesive layer comprises an acrylic copolymer polymerized from a monomer blend including a first acrylate-based monomer having less than 18 carbon atoms and a second acrylate-based monomer having 18 or more carbon atoms.
The pressure-sensitive adhesive sheet of claim 2, wherein a ratio of the weight of the second acrylate-based monomer to the weight of the first acrylate-based monomer in the monomer blend is 0.2 to 9.
The pressure-sensitive adhesive sheet according to claim 2, wherein the monomer blend further comprises a polar monomer containing a carboxyl group or an amide group.
The method according to claim 4, wherein the monomer blend comprises 10 to 75 parts by weight of the first acrylate-based monomer, 20 to 85 parts by weight of the second acrylate-based monomer, and 0.5 to 10 parts by weight of the polar monomer in 100 parts by weight of the monomer blend. A pressure-sensitive adhesive sheet containing parts by weight.
The pressure-sensitive adhesive sheet according to claim 5, wherein the amount of the hydroxyl group-containing monomer is 2 parts by weight or less in 100 parts by weight of the monomer blend.
The method according to claim 2, wherein the second acrylate-based monomer comprises 2-decyl-1-tetradecanyl (meth) acrylate (2-decyl-1-tetradecanyl (meth) acrylate) or stearyl (meth) acrylate To do, an adhesive sheet.
The pressure-sensitive adhesive sheet according to claim 1, wherein the dielectric loss tangent of the pressure-sensitive adhesive layer is 0.005 or less.
The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a storage modulus at 25°C of 20 to 40 kPa.
The pressure-sensitive adhesive sheet according to claim 1, further comprising a protective film formed on at least one surface of the pressure-sensitive adhesive layer.
antenna dielectric layer;
an antenna electrode layer disposed on an upper surface of the antenna dielectric layer; and
An antenna structure comprising the adhesive sheet of claim 1 attached on the lower surface of the antenna dielectric layer.
display panel; and
An image display device comprising the antenna structure according to claim 11 attached to the display panel.

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