KR20230109460A - Adhesive sheet and antenna structure including the same - Google Patents

Abstract

According to exemplary embodiments, an adhesive sheet, an antenna structure including the same, and an image display device are provided. The pressure-sensitive adhesive sheet includes a dielectric layer having a dielectric loss tangent within a predetermined range, and is formed on the lower and upper surfaces of the dielectric layer, respectively, and includes first and second pressure-sensitive adhesive layers having a dielectric loss tangent and a glass transition temperature within a predetermined range. include Accordingly, a pressure-sensitive adhesive sheet having excellent dielectric properties and folding properties can be provided.

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 specifically, it relates to an adhesive sheet including a dielectric layer 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 the above-described dielectric properties are not considered.

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. A dielectric layer with a dielectric loss tangent greater than zero and less than or equal to 0.007 at 15 GHz; a first pressure-sensitive adhesive layer formed on an upper surface of the dielectric layer, having a dielectric loss tangent greater than 0 and less than or equal to 0.01 at 15 GHz, and having a glass transition temperature of -75 to -50 °C; and a second pressure-sensitive adhesive layer formed on a lower surface of the dielectric layer, having a dielectric loss tangent greater than 0 and less than or equal to 0.01 at 15 GHz, and a glass transition temperature of -75 to -50°C.

2. The pressure-sensitive adhesive sheet according to 1 above, wherein the dielectric layer has a permittivity of 2.0 to 3.6 at 15 GHz.

3. The pressure-sensitive adhesive sheet according to 1 above, wherein the first pressure-sensitive adhesive layer has a dielectric constant of 2.0 to 3.6 at 15 GHz.

4. The pressure-sensitive adhesive sheet according to 1 above, wherein the second pressure-sensitive adhesive layer has a dielectric constant of 2.0 to 3.6 at 15 GHz.

5. The pressure-sensitive adhesive sheet according to 1 above, wherein the dielectric loss tangent at 15 GHz measured at a thickness of 150 μm is greater than 0 and less than or equal to 0.01.

6. The pressure-sensitive adhesive sheet according to 1 above, wherein the dielectric layer has a thickness of 10 to 80 μm.

7. The pressure-sensitive adhesive sheet according to 1 above, wherein the first pressure-sensitive adhesive layer has a thickness of 5 to 50 μm and the second pressure-sensitive adhesive layer has a thickness of 5 to 50 μm.

8. The pressure-sensitive adhesive sheet according to 1 above, having a thickness of 20 to 180 μm.

9. The pressure-sensitive adhesive sheet according to 1 above, further comprising a protective film formed on the upper surface of the first pressure-sensitive adhesive layer or the lower surface of the second pressure-sensitive adhesive layer.

10. Antenna dielectric layer; an antenna electrode layer disposed on an upper surface of the antenna dielectric layer; and the adhesive sheet of 1 above attached on the lower surface of the antenna dielectric layer.

11. display panel; and the antenna structure according to 10 above attached to the display panel.

12. The image display device according to 11 above, wherein the separation distance between the display panel and the antenna electrode layer is 100 μm or more.

An adhesive sheet according to example embodiments may include a dielectric layer having a dielectric loss tangent in a predetermined range. Accordingly, the sheet may gradually have improved folding characteristics, and antenna gain and radiation characteristics due to the adhesive sheet may not be deteriorated.

The pressure-sensitive adhesive sheet according to example embodiments may include a pressure-sensitive adhesive layer having a dielectric loss tangent and a glass transition temperature within a predetermined range. Accordingly, the adhesive sheet has improved folding characteristics and can provide stable flexibility and bending characteristics when applied to a flexible display.

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.

According to example embodiments, the pressure-sensitive adhesive sheet may have a thickness within a predetermined range. Accordingly, for example, signal disturbance and interference between the antenna electrode disposed on the upper surface of the adhesive sheet and the display electrode of the image display device disposed on the lower surface of the adhesive sheet can be suppressed. Accordingly, a flexible display having improved folding characteristics while having excellent antenna gain and radiation characteristics can be provided.

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.

A pressure-sensitive adhesive sheet according to embodiments of the present invention includes a dielectric layer, a first pressure-sensitive adhesive layer formed on an upper surface of the dielectric layer, and a second pressure-sensitive adhesive layer formed on a lower surface of the dielectric layer. The dielectric layer may have a dielectric dissipation factor value within a predetermined range. In addition, each of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have predetermined dielectric properties and glass transition temperatures.

In addition, the antenna structure and the image display device according to embodiments of the present invention include the adhesive sheet.

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 includes a dielectric layer 110, a first pressure-sensitive adhesive layer 120 formed on the top surface of the dielectric layer 110, and a second pressure-sensitive adhesive layer 120 formed on the bottom surface of the dielectric layer 110. An adhesive layer 130 may be included. The pressure-sensitive adhesive sheet 100 may further include protective films 140 and 150 formed on the top surface of the first pressure-sensitive adhesive layer 120 or the bottom surface of the second pressure-sensitive adhesive layer 130 .

According to example embodiments, a dielectric loss tangent (dielectric loss or loss tangent; Df) value measured at a thickness of 40 μm and 15 GHz of the dielectric layer 110 may be 0.007 or less. For example, the dielectric loss tangent of the dielectric layer 110 may exceed 0 and may be 0.007 or less.

As the dielectric loss of the dielectric layer 110 is suppressed within the above range, the dielectric characteristics of the antenna dielectric layer 110 by the adhesive sheet 100 may not be varied or disturbed.

Preferably, the dielectric loss tangent of the dielectric layer 110 may exceed 0 and be 0.005 or less, more preferably 0.003 or less, and even more preferably 0.002 or less.

According to exemplary embodiments, the permittivity of the dielectric layer 110 measured at a frequency of 15 GHz may be 2.0 to 3.6, preferably 2.0 to 3.0. Within the above range, for example, when applied to an antenna structure, direct influence on the radiation characteristics and gain characteristics of the antenna can be avoided or suppressed.

In some embodiments, the dielectric layer 110 may have a thickness of 10 μm to 80 μm.

Within the above range, both the dielectric and folding characteristics of the dielectric layer 110 may be excellent, and for example, the antenna gain and radiation characteristics of the adhesive sheet 100 may not deteriorate while having improved folding characteristics. Accordingly, an antenna structure or flexible display having improved flexibility while maintaining high frequency/ultra high frequency antenna radiation reliability may be implemented.

In some embodiments, the dielectric layer 110 may be a transparent film having the dielectric characteristics described above. For example, the dielectric layer 110 may be a polyester-based resin such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, or polybutylene terephthalate; polycarbonate-based resin; styrenic resins such as polystyrene and acrylonitrile-styrene copolymer; polyolefin-based resins such as polyethylene, polypropylene, polyolefins having a cyclo-based or norbornene structure, and ethylene-propylene copolymers; vinyl chloride-based resins; amide resins such as nylon and aromatic polyamide; imide-based resins; polyethersulfone-based resins; sulfone-based resins; polyether ether ketone-based resins; sulfurized polyphenylene-based resins; vinyl alcohol-based resin; vinylidene chloride-based resins; vinyl butyral-based resins; allylate-based resins; polyoxymethylene-based resin; thermoplastic resins such as epoxy resins; A thermosetting resin or an ultraviolet curable resin such as an acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, or a silicone resin may be included. These may be used alone or in combination of two or more.

According to example embodiments, the dielectric loss tangent of the first adhesive layer 120 measured at 15 GHz may be 0.01 or less. For example, the dielectric loss tangent measured at a thickness of 50 μm of the first pressure-sensitive adhesive layer 120 may exceed 0 and be 0.01 or less.

According to example embodiments, a dielectric loss tangent of the second pressure-sensitive adhesive layer 130 measured at 15 GHz may be 0.01 or less. For example, the dielectric loss tangent measured at a thickness of 50 μm of the second pressure-sensitive adhesive layer 130 may exceed 0 and be 0.01 or less.

As the loss tangent of the first adhesive layer 120 or the second adhesive layer 130 is adjusted within the above range, the dielectric of the antenna dielectric layer 110 by the first adhesive layer 120 and the second adhesive layer 130 The characteristics may not fluctuate or be disturbed, and for example, a high-gain antenna structure may be provided.

Preferably, both the first adhesive layer 120 and the second adhesive layer 130 may have a dielectric loss tangent of 0.01 or less.

In some embodiments, the dielectric constant of the first pressure-sensitive adhesive layer 120 measured at 15 GHz may be 3.6 or less. For example, the dielectric constant of the first pressure-sensitive adhesive layer 120 measured at 15 GHz may be 2.0 to 3.6.

In some embodiments, the dielectric constant of the second pressure-sensitive adhesive layer 130 measured at 15 GHz may be 3.6 or less. For example, the dielectric constant of the second pressure-sensitive adhesive layer 130 measured at 15 GHz may be 2.0 to 3.6.

As the permittivity of the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 is adjusted within the above range, it is possible to prevent a decrease in sensitivity to electrical signals of the display panel due to the pressure-sensitive adhesive layer. In addition, for example, since the pressure-sensitive adhesive layer adjacent to the antenna electrode layer has a low permittivity, high-gain radiation characteristics can be implemented at high frequencies/ultra-high frequencies.

Preferably, both the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 may have a dielectric constant of 3.6 or less.

According to exemplary embodiments, the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 may each have a glass transition temperature of -75 to -50 °C.

Within the above range, the flexibility and bending characteristics of the pressure-sensitive adhesive layer may be excellent, and for example, even when the thickness of the pressure-sensitive adhesive layer increases, mechanical defects such as cracks and peeling may be suppressed during folding/bending. Accordingly, defects such as cracks may not be caused even under harsh bending conditions while maintaining sufficient mechanical strength and impact resistance of the adhesive sheet 100 .

For example, since the thickness of the first adhesive layer 120 and the second adhesive layer 130 can be increased while maintaining excellent bending characteristics of the adhesive sheet 100, the overall thickness of the adhesive sheet 100 can increase Therefore, the distance between the antenna dielectric layer 110 and the electrode of the image display device can be increased, and signal interference and disturbance between adjacent electrodes can be prevented. In this case, an antenna structure having excellent gain in an ultra-high frequency band may be provided.

For example, the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 may not be cracked or peeled even when they are bent 10,000 times or more at a rate of 25 times per minute with a radius of curvature of 2 mm at -20°C.

In some embodiments, each of the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 may have a thickness of 5 to 50 μm. Since the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 have the above-described glass transition temperature, excellent bending/bending properties can be maintained, and flexibility of the pressure-sensitive adhesive sheet 100 even when the thickness of the pressure-sensitive adhesive layer increases. And flexible properties may be excellent.

According to exemplary embodiments, the thickness of the adhesive sheet 100 may be 20 to 180 μm.

In one embodiment, the thickness of the adhesive sheet 100 may be 50 μm or more. For example, the thickness of the pressure-sensitive adhesive sheet 100 may be 50 to 180 μm, specifically 100 to 180 μm.

When the thickness of the adhesive sheet 100 is less than 50 μm, for example, the separation distance between the antenna electrode layer and the electrode of the image display device may be reduced. Accordingly, signal interference and disturbance may occur between electrodes disposed adjacent to each other, and antenna gain and radiation characteristics may be deteriorated.

The adhesive sheet 100 according to exemplary embodiments may have a dielectric loss tangent greater than 0 and less than 0.01 at 15 GHz measured at a thickness of 150 μm. Deterioration of antenna gain and radiation characteristics due to the adhesive sheet 100 within the above range can be prevented. Preferably, a dielectric loss tangent at 15 GHz measured at a thickness of 150 μm of the adhesive sheet 100 may be greater than 0 and less than 0.005.

In some embodiments, the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 may include a resin or copolymer that satisfies the dielectric constant, dielectric loss tangent, and glass transition temperature. For example, , acrylic copolymers, siloxane-based copolymers, isobutylene-based copolymers, or styrene-based copolymers.

In one embodiment, the pressure-sensitive adhesive layer may include an acrylic copolymer. For example, the first pressure-sensitive adhesive layer 120 and the second pressure-sensitive adhesive layer 130 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 an alkyl (meth)acrylate monomer having a non-polar hydrocarbon group and a polar monomer having a polar functional group. By including the alkyl (meth)acrylate monomer having the non-polar hydrocarbon group, polarization characteristics of the pressure-sensitive adhesive layer may be reduced, and permittivity and dielectric loss may be reduced. Cohesive strength of the copolymer may be further enhanced by adding the polar monomer, and mechanical stability of the pressure-sensitive adhesive layer may be additionally improved upon folding.

As an example of the alkyl (meth) acrylate monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate rate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate rate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isobornyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, Isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-pentafluorooctyl acrylate, 2-ethylhexyldiglycol acrylate, 2-decyl-1-tetradecyl (meth)acrylate (2-decyl-1-tetradecanyl (meth)acrylate), stearyl (meth)acrylate, and the like. These may be used alone or in combination of two or more.

The polar monomer may include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, or an amide group-containing monomer. These may be used alone or in combination of two or more.

As examples of the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) )Acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methylacrylate etc. can be mentioned.

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

Examples of the amide group-containing monomer 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.

The pressure-sensitive adhesive composition may further include a photopolymerization initiator or a thermal curing agent to improve 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 may be used alone or in combination of two or more.

The amount of the photopolymerization initiator may be 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 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.

In some embodiments, the pressure-sensitive adhesive sheet 100 may further include a protective film formed on a surface of the first pressure-sensitive adhesive layer 120 or the second pressure-sensitive adhesive layer 130 .

For example, the sheet may gradually include a first protective film 140 and a second protective film 150 respectively formed on the top surface of the first pressure-sensitive adhesive layer 120 and the bottom surface of the second pressure-sensitive adhesive layer 130. .

The first protective film 140 may be provided as a release film for attaching the adhesive sheet 100 to an object. The second protective film 150 may be provided as a base film for forming the pressure-sensitive adhesive layer.

In some embodiments, the second protective film 150 may also be provided as a release film. In this case, the adhesive sheet 100 may be provided as a double-sided adhesive sheet 100 .

The first protective film 140 and the second protective film 150 may be formed of, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutyrene 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 resins; 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 170, an antenna dielectric layer 160, and an adhesive sheet 100 according to the above-described exemplary embodiments.

The antenna electrode layer 170 may be formed on the antenna dielectric layer 160 . As shown in FIG. 3 , the antenna electrode layer 170 may include an antenna unit AU, and a plurality of antenna units AU may be arranged on the antenna dielectric layer 160 .

The antenna unit AU may include a radiator 172 , a transmission line 174 and a signal pad 176 . The signal pad 176 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 172 through the transmission line 174 .

A pair of ground pads 178 may be disposed around the signal pad 176 with the signal pad 176 interposed therebetween.

According to exemplary embodiments, high-frequency or ultra-high frequency communication may be performed through the radiator 172 , for example, in a band of 5 GHz or more, 10 GHz or more, or 20 GHz or more.

The antenna dielectric layer 160 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 140 is removed. Accordingly, the first adhesive layer may directly contact the bottom surface of the antenna dielectric layer 160 .

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 second protective film 150 , the antenna structure may be attached to the display panel 200 through the second adhesive layer 130 .

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 second protective film 150 may be removed and the second adhesive layer 130 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 .

In some embodiments, the separation distance between the antenna electrode layer 170 and the display panel 200 may be greater than or equal to 100 μm. For example, the thickness of the adhesive sheet 100 disposed between the antenna electrode layer 170 and the display panel 200 may be 100 μm or more. In this case, a predetermined separation distance between the electrodes in the display panel 200, for example, the pixel electrode 210 and the counter electrode 240, and the antenna electrode layer 170 may be secured. Accordingly, signal interference and disturbance between electrodes can be prevented, and the antenna unit AU can have high-gain radiation characteristics in a high frequency/ultra high frequency region.

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 pressure-sensitive adhesive composition

Preparation Example 1

After introducing a monomer blend including 95 parts by weight of 2-ethylhexyl acrylate, 2 parts by weight of 2-hydroxyethyl acrylate (HEA), and 3 parts by weight of acrylic acid (AA) into a 1L reactor, 1-hydroxy as a photoinitiator 0.5 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone was added. Thereafter, while measuring the viscosity of the mixture using a viscosity measuring device, ultraviolet rays were irradiated using an ultraviolet irradiation device until the viscosity of the mixture became about 20 Pa·s. In the viscosity measurement, the rotational speed of the rotor of the apparatus was 20 rpm, and the measurement temperature was 30°C. Thus, a prepolymer composition in which a part of the monomer components in the mixture is a partially polymerized product was prepared.

In order to measure the physical properties of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, the composition was coated on a polyethylene terephthalate film (thickness: 75 μm) treated with a coating solution using a bar coater. Thereafter, from the side of the release liner on one side, a black light (manufactured by Philips) was used to irradiate and cure an ultraviolet ray having an illuminance of 8 mW/cm 2 for 200 seconds to prepare an adhesive film having a thickness of 50 μm after curing of the pressure-sensitive adhesive composition. .

The glass transition temperature of the pressure-sensitive adhesive layer was measured using a differential scanning calorimeter (DSC8000, PerkinElmer Inc.) and was measured as -58°C. The dielectric constant and dielectric loss tangent of the pressure-sensitive adhesive layer were measured using a dielectric constant measuring device (Anritus Co., product name MS46522B), and the dielectric constant at a frequency of 15 GHz was 2.7, and the dielectric loss tangent at a frequency of 15 GHz was measured as 0.005.

Preparation Example 2

An adhesive composition was prepared in the same manner as in Preparation Example 1, except that the monomer blend was a monomer composition containing 97 parts by weight of 2-ethylhexyl acrylate (EHA) and 3 parts by weight of acrylic acid (AA).

The glass transition temperature, dielectric constant, and dielectric loss tangent of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition were measured in the same manner as in Preparation Example 1. A pressure-sensitive adhesive layer having a glass transition temperature measured by the above method was -61°C, a dielectric constant of 2.6 at a frequency of 15 GHz, and a dielectric loss tangent of 0.004 at a frequency of 15 GHz was prepared.

Preparation Example 3

A pressure-sensitive adhesive composition was prepared in the same manner as in Preparation Example 1, except that the monomer blend was a monomer composition containing 90 parts by weight of 2-ethylhexyl acrylate (EHA) and 10 parts by weight of 2-hydroxyethyl acrylate (HEA). .

The glass transition temperature, dielectric constant, and dielectric loss tangent of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition were measured in the same manner as in Preparation Example 1. A pressure-sensitive adhesive layer having a glass transition temperature measured by the above method is -61°C, a dielectric constant of 2.6 at a frequency of 15 GHz, and a dielectric loss tangent of 0.012 at a frequency of 15 GHz was prepared.

Production Example 4

An adhesive composition was prepared in the same manner as in Preparation Example 1, except that the monomer blend was a monomer composition containing 95 parts by weight of 2-ethylhexyl acrylate (EHA) and 5 parts by weight of acrylic acid (AA).

The glass transition temperature, dielectric constant, and dielectric loss tangent of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition were measured in the same manner as in Preparation Example 1. A pressure-sensitive adhesive layer having a glass transition temperature measured by the above method was -48°C, a dielectric constant of 2.4 at a frequency of 15 GHz, and a dielectric loss tangent of 0.004 at a frequency of 15 GHz was prepared.

Preparation Example 5

An adhesive composition was prepared in the same manner as in Preparation Example 1, except that the monomer blend was a monomer composition containing 95 parts by weight of 2-ethylhexyl diglycol acrylate and 5 parts by weight of acrylic acid (AA).

The glass transition temperature, dielectric constant, and dielectric loss tangent of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition were measured in the same manner as in Preparation Example 1. A pressure-sensitive adhesive layer having a glass transition temperature measured by the above method was -79°C, a dielectric constant of 2.9 at a frequency of 15 GHz, and a dielectric loss tangent of 0.02 at a frequency of 15 GHz was prepared.

Manufacture of adhesive sheet

The lower and upper surfaces of the dielectric layer prepared as shown in Tables 1 and 2 were coated using a bar coater, respectively, using the pressure-sensitive adhesive composition prepared in the above Preparation Examples. Thereafter, each coated surface was irradiated with ultraviolet rays having an illuminance of 8 mW/cm 2 using a black light (manufactured by Philip) for 200 seconds to prepare an adhesive sheet. After curing, the pressure-sensitive adhesive composition was applied so that the thickness of the pressure-sensitive adhesive layer coated on both sides of the dielectric layer was 50 μm.

division Example One 2 3 4 5 1st adhesive layer type Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 1 Preparation Example 2 permittivity 2.7 2.7 2.7 2.7 2.6 dielectric loss tangent 0.005 0.005 0.005 0.005 0.004 Glass transition temperature (℃) -58 -58 -58 -58 -61 dielectric layer type PET LCP COP PI PET thickness 23 40 40 25 23 permittivity 2.8 3.5 2.4 2.9 2.8 dielectric loss tangent 0.0059 0.0021 0.0004 0.0070 0.0059 2nd adhesive layer type manufacturing example
One manufacturing example
One manufacturing example
One manufacturing example
One manufacturing example
2 permittivity 2.7 2.7 2.7 2.7 2.6 dielectric loss tangent 0.005 0.005 0.005 0.005 0.004 Glass transition temperature (℃) -58 -58 -58 -58 -61

division comparative example One 2 3 4 1st adhesive layer type Preparation Example 1 Preparation Example 3 Production Example 4 Preparation Example 5 permittivity 2.7 2.6 2.4 2.9 dielectric loss tangent 0.005 0.012 0.004 0.02 Glass transition temperature (℃) -58 -61 -48 -79 dielectric layer type TAC PET PET PET thickness 40 23 23 23 permittivity 4.0 2.8 2.8 2.8 dielectric loss tangent 0.0308 0.0059 0.0059 0.0059 2nd adhesive layer type Preparation Example 1 Preparation Example 3 Production Example 4 Preparation Example 5 permittivity 2.7 2.6 2.4 2.9 dielectric loss tangent 0.005 0.012 0.004 0.02 Glass transition temperature (℃) -58 -61 -48 -79

Experimental example

(1) Measurement of dielectric loss tangent and permittivity

The dielectric constant and dielectric loss tangent of each of the pressure-sensitive adhesive sheets of Examples and Comparative Examples were measured at 25° C. using a dielectric constant measuring device (Anritus Co., product name MS46522B). Specifically, the adhesive sheet from which the release film was removed was laminated between 40 μm COP films (Zeonor Co.) and cut into a size of 30 mm in length x 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 15 GHz.

<Evaluation Criteria>

◎: 0.005 or less

○: more than 0.005 and less than 0.01

×: greater than 0.01

(2) Evaluation of folding characteristics

Each of the pressure-sensitive adhesive sheets of Examples and Comparative Examples was bonded to 50 μm PET to prepare a 20 mm × 100 mm sample. The sample was fixed to a flexural evaluation device (COVOTECH, CFT-720C), and folding was evaluated at -20°C under conditions of folding 25 times per minute, holding 0.2 seconds after folding once, and curvature radius of 2 mm. The folding characteristics were evaluated as follows by measuring the number of times of initial folding at which defects such as breakage, lifting, and peeling occurred at the folding site.

<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

division Example 1 Example 2 Example 3 Example 4 Example 5 Dielectric loss tangent (Df) ○ ◎ ◎ ○ ◎ folding characteristics ◎ ○ ○ ◎ ◎ division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 - Dielectric loss tangent (Df) × × ○ × - folding characteristics ○ ○ × ○ -

Referring to Tables 1 to 3, the pressure-sensitive adhesive sheet according to the exemplary embodiments satisfies the above-described glass transition temperature range while having a low dielectric loss tangent in the dielectric layer and the pressure-sensitive adhesive layer. Therefore, excellent durability was provided even when folded at severe low temperatures, and the adhesive sheet could have a low dielectric loss tangent as a whole.

However, since the dielectric layer and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to Comparative Examples have a high dielectric loss tangent, it can be confirmed that the dielectric properties of the pressure-sensitive adhesive sheet are deteriorated. In addition, it can be confirmed that the adhesive layer has a high glass transition temperature and thus defects occur during repeated folding.

100: adhesive sheet 110: dielectric layer
120: first adhesive layer 130: second adhesive layer
140: first protective film 150: second protective film
160: antenna dielectric layer 170: antenna electrode layer
172 emitter 174 transmission line
176: signal pad 200: display panel
260: touch sensor layer 270: polarization layer
280: cover window 300: antenna structure
400: image display device

Claims (12)

a dielectric layer having a dielectric loss tangent greater than 0 and less than or equal to 0.007 at 15 GHz;
a first pressure-sensitive adhesive layer formed on an upper surface of the dielectric layer, having a dielectric loss tangent greater than 0 and less than or equal to 0.01 at 15 GHz, and having a glass transition temperature of -75 to -50 °C; and
A pressure-sensitive adhesive sheet comprising a second pressure-sensitive adhesive layer formed on a lower surface of the dielectric layer, having a dielectric loss tangent greater than 0 and less than or equal to 0.01 at 15 GHz, and having a glass transition temperature of -75 to -50 ° C.
The pressure-sensitive adhesive sheet according to claim 1, wherein the dielectric layer has a permittivity of 2.0 to 3.6 at 15 GHz.
The pressure-sensitive adhesive sheet according to claim 1, wherein the first pressure-sensitive adhesive layer has a dielectric constant of 2.0 to 3.6 at 15 GHz.
The pressure-sensitive adhesive sheet according to claim 1, wherein the second pressure-sensitive adhesive layer has a dielectric constant of 2.0 to 3.6 at 15 GHz.
The adhesive sheet according to claim 1, wherein the dielectric loss tangent at 15 GHz measured at a thickness of 150 μm is greater than 0 and less than or equal to 0.01.
The pressure-sensitive adhesive sheet according to claim 1, wherein the dielectric layer has a thickness of 10 to 80 μm.
The pressure-sensitive adhesive sheet of claim 1 , wherein the first pressure-sensitive adhesive layer has a thickness of 5 to 50 μm and the second pressure-sensitive adhesive layer has a thickness of 5 to 50 μm.
The pressure-sensitive adhesive sheet according to claim 1, having a thickness of 20 to 180 μm.
The pressure-sensitive adhesive sheet of claim 1, further comprising a protective film formed on an upper surface of the first pressure-sensitive adhesive layer or a lower surface of the second 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 10 attached to the display panel.
The image display device according to claim 11 , wherein the separation distance between the display panel and the antenna electrode layer is 100 μm or more.