KR101668745B1

KR101668745B1 - Double-sided adhesive sheet having hybrid cross-linking acryl layer

Info

Publication number: KR101668745B1
Application number: KR1020150178370A
Authority: KR
Inventors: 유혁상
Original assignee: 주식회사 진양엠티에스
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2016-10-24

Abstract

The present invention relates to a double-sided pressure-sensitive adhesive sheet comprising an acryl base copolymer layer, an acrylonitrile butadiene block copolymer, a photo-reactive acrylate, a photoinitiator and a thermosetting agent, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a double-sided pressure-sensitive adhesive sheet,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided pressure-sensitive adhesive sheet, and more particularly to a double-sided pressure-sensitive adhesive sheet comprising an acrylic layer bridged by a thermosetting and photo-

In recent years, as the electronic devices such as TVs, PDAs, mobile phone terminals, or car navigation systems have become more sophisticated, the technology has been continuously developed for weight reduction, thinning, low power consumption, high luminance and large screen size.

In particular, a touch screen to be applied to an electronic apparatus having a touch screen or a touch panel switch on an input operation unit is in the form of a tempered glass, and various conductive films and an adhesive film are attached to the lower ends of the tempered glass. In addition, the main body of electronic devices has been introduced not only into various plastics but also metal materials. In this field, double-sided adhesive tapes are needed to adhere the surfaces of different materials, which are necessary for fixing the display module and the liquid crystal module. Such double-sided functional tapes have recently become more and more dependent on the large- As the width of the bezel of the conventional display portion has become narrower to 1 mm or less in recent years, the mounting area of the double-sided tape has also become narrower. There is a demand for a multi-functional double-sided tape capable of performing both of the function of impact resistance and the like in addition to the function of simply fixing the module set of the display panel in spite of the thinning of the attachment area width and the reduced thickness.

Typical examples of such a double-sided tape include an acrylic base layer attached to a polyester film layer and an adhesive layer formed on both sides thereof. Such an acryl base layer is usually cured by light curing as disclosed in Korean Patent No. 10-0813217. For example, as disclosed in Korean Patent No. 10-1406084, a base material which is cured by using an acrylic monomer, an acrylic crosslinking agent and a photoinitiator is used. In order to shorten the curing time, Korean Patent Publication No. 10-2013-0038513 uses a new acrylic compound. In order to improve the elongation, Korean Patent Laid-Open Publication No. 10-2014-0146177 also incorporated polystyrene into an acrylic resin.

Korean Patent No. 10-0813217 Korean Patent No. 10-1406084 Korean Patent Publication No. 10-2013-0038513 Korean Patent Publication No. 10-2014-0146177

The disadvantage of the thermosetting acrylic pressure-sensitive adhesive is that the elongation and elasticity are significantly lowered, and that the cohesion and substrate adhesion properties of the thermosetting crosslinking agent are deteriorated by the use of a single crosslinking agent or crosslinking method. An advantage of ultraviolet curable pressure sensitive adhesive is that it has excellent elasticity, but a major disadvantage is that the thickness of the curable coating film is limited and the internal hardening is insufficient and the adhesion of the substrate is deteriorated.

In order to overcome this problem, a double-sided pressure-sensitive adhesive sheet having excellent substrate adhesion and a highly elastic base layer can be obtained through a hybrid crosslinking method of composite thermosetting and ultraviolet curing.

The base layer of the double-sided pressure-sensitive adhesive sheet of the present invention has improved heat resistance, elasticity, and substrate adhesion as compared with the conventional base layer.

1 is an exploded perspective view showing the structure of a pressure-sensitive adhesive sheet of the present invention
2 is a cross-sectional view showing the structure of the pressure-sensitive adhesive sheet of the present invention
3 is a schematic view showing a static force peeling force test method for measuring high temperature heat resistance
Fig. 4 is a photograph (SUS304 (left three specimens), PC (right three specimens)) of the adherend after adhering force measurement after attaching adherend (SUS304, PC)
Fig. 5 is a photograph showing the peeling distance of the tape and the tacky agent transition phenomenon after the static load peeling force test (test condition 85 캜 dry heat condition)

As shown in the exploded perspective view of Fig. 1 and the cross-sectional view of Fig. 2, the double-sided tape according to the present invention comprises a base film layer 10, a composite crosslinked acrylic base layer A first adhesive layer 30 formed on the upper surface of the composite crosslinked acrylic substrate layer 20 and a second adhesive layer 40 formed on the lower surface of the base film layer 10. The base film layer 10 is usually colored or printed in black using a polyester film.

The adhesive layers 30 and 40 may further include a release film layer on and under the adhesive layers 30 and 40, respectively.

The acrylic base layer 20 of the present invention includes an acrylic copolymer, an acrylonitrile butadiene block copolymer, a photo-reactive acrylate, a photoinitiator, and a heat crosslinking agent.

The acrylic copolymer used in the acrylic base layer 20 of the present invention contains alkyl (meth) acrylate as a main component. (Meth) acrylate means acrylate and methacrylate. The alkyl group carbon number of the alkyl (meth) acrylate is 1 to 18, preferably 1 to 9, and may be linear or branched. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl acrylate, isobutyl (Meth) acrylate, n-octyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, etc. These may be used alone or in combination.

Examples of the polymerizable monomer having a carboxyl group used in the copolymer include acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotic acid, itaconic acid, citraconan, cinnamic acid, succinic acid monohydroxy, ethyl (meth) (Meth) acrylate, monohydroxyethyl (meth) acrylate, fumaric acid monohydroxyethyl (meth) acrylate, phthalic acid monohydroxyethyl (meth) acrylate, 1,2- dicarboxycyclohexane monohydroxyethyl (Meth) acrylic acid dimer and w-carboxy-polycaprolactone monoacrylate. Of these, acrylic acid, methacrylic acid and succinic acid monohydroxyethyl (meth) acrylate are preferable, and acrylic acid, Methacrylic acid, and most preferably acrylic acid.

Hydroxy-containing polymerizable monomers used in the copolymer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) Hydroxypropyleneglycol (meth) acrylate, 2-hydroxypropyleneglycol (meth) acrylate, 2-hydroxypropyleneglycol (meth) (Meth) acrylate having 2 to 4 carbon atoms of an acrylene group such as 2-hydroxyethyl (meth) acrylate. Of these, 2-hydroxyethyl (meth) acrylate is preferable.

The composition of the pressure-sensitive adhesive contains the heat-crosslinking agent in the acrylic copolymer. The crosslinking agent can improve the heat resistance and the adhesion to the substrate, and can maintain the reliability at a high temperature.

The cross-linking agent may be an isocyanate-based, epoxy-based, peroxide-based, metal chelating-based, oxazoline-based, or the like, and two or more of them may be used in combination to improve substrate adhesion, heat resistance and reliability. Such a crosslinking agent may be contained in an amount of 0.1 to 15 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer. If the content is less than 0.1 part by weight, the lack of crosslinking may result in a lack of cohesive strength, which may result in deterioration of adhesion durability, heat resistance and cuttability in the post-processing. If the content is more than 15 parts by weight, excessively crosslinking reaction may cause problems in adhesive strength and residual stress relaxation have.

The acrylic base layer of the present invention is a composite curing type, for example, an epoxy crosslinking (thermosetting) isocyanate crosslinking (secondary thermosetting), and ultraviolet curing to obtain a highly elastic acrylic elastomer. Epoxy crosslinking reaction can make excellent cohesion and heat resistance. The pressure-sensitive adhesive having an epoxy group in the polymer can be cured by using an epoxy curing agent such as polyamines (e.g., GMA, CH ₂ = C (CH ₃ ) COOCH ₂ -CH-CH ₂ ) Reaction may be used. In addition, the isocyanate crosslinking reaction makes the adhesion of the base material excellent. Crosslinking of isocyanate proceeds at room temperature and is widely used as a cross-linking agent for acrylic pressure-sensitive adhesives. Those which are mainly used are those of early condensation products of TMP and TDI, and are used as isocyanate systems of non-sulfur substitution. This results in a three-dimensional cross-linking between the -OH group in the pressure-sensitive adhesive and the -NCO in the curing agent.

The elastomer used in the base layer of the present invention is an elastomer which exhibits rubber-like elasticity in order to make it excellent in elasticity and elongation. Examples of the elastomer include natural rubber, NR, graft-NR, isoprene rubber, Butadiene rubber (BR) Natural rubber such as chloroprene rubber (CR), acrylonitrile rubber block copolymer (NBR), styrene butadiene rubber (SBR), butyl rubber (IIR), ethylene propylene rubber (EPDM), polyisobutylene Or synthetic rubber; olefinic elastomers such as ethylene-propylene copolymer, ethylene-propylene-diene prismatic pressure-sensitive adhesive, ethylene-vinyl acetate copolymer, polybutene and chlorinated polyethylene; Styrene-butadiene multiblock copolymer (SBS), styrene-isoprene multi block copolymer (SIS), styrene-ethylene / butylene-styrene multiblock copolymer (SEBS), styrene-ethylene / SEPS), and their hydrogenated styrene elastomers; And silicone-based elastomers. These elastomers may be used alone or in combination of two or more, and the most preferred elastomer is an acrylonitrile butadiene block copolymer elastomer. The amount of the acrylic elastomer to be used is 1 to 20 parts by weight, preferably 5 to 15 parts by weight, based on the total weight of the mixture. If the amount is less than 5 parts by weight, the elasticity and elongation properties of the polymer may deteriorate, and the inherent role of the elastomer may not be realized. If the amount exceeds 15 parts by weight, the adhesion of the base material becomes significantly poor.

The photoreactive monomer may be selected from the group consisting of 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA) , 1,2-ethylene glycol diacrylate, 1,12-dodecanediol acrylate, and ethoxylated trimethylolpropane triacrylate (TMPEOTA). Among these, one or more types of ultraviolet A curing type acrylic elastic resin can be used.

The photoinitiator may be a benzoin ether, an acetophenone, an a-ketol, a photoactive oxime, a benzoin, a benzyl, a benzophenone, a ketal, a thioxanthone, or an acylphosphine oxide. Specific examples of the benzoin ester system include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, 2,2-dimethoxy-1,2-diphenylethan- , Anisole methyl ether, and the like. Examples of the acetophenone-based solvents include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4- -Butyldichloroacetophenone, and the like. Examples of the? -ketol group include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) phenyl] -2-hydroxy-2-methylpropan- . Examples of the optically active oxime system include 1-phenyl-1, 1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like. Examples of the benzoin group include benzoin. Examples of the benzyl group include benzyl. Examples of the benzophenone group include benzophenone, benzoylbenzoic acid, 3,3'-methyl-4-methoxybenzophenone, polyvinylbenzophenone, a-hydroxycyclohexylbenzophenone And the like. As the ketal group, for example, benzyl metal ketal and the like can be mentioned. Examples of the thioxanthone system include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanic acid, 2,4-dichlorotioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like. Examples of the acylphosphine oxide system include diphenyl- (2,4,6-trimethylbenzoyl) phosphine oxide. The photoinitiator may be a mixture of one or two photoinitiators. The amount of the photoinitiator to be used is 0.05 to 1.5 parts by weight, preferably 0.1 to 1 part by weight per 100 parts by weight of the mixture.

The composite crosslinked acrylic base layer of the present invention may also contain elastic micro hollow microparticles. The hollow microparticles use particles having excellent solvent resistance and chemical resistance due to cross-linking of the particle surfaces, so that there is no dissolution phenomenon in the organic solvent during the coating process . The hollow fine particles have a very low specific gravity, so that the impact resistance elastic effect can be realized at a weight of less than 0.1 to 10 parts by weight based on 100 parts by weight of the mixture.

Examples 1-2 and Comparative Example 1

The raw materials were mixed in a weight ratio shown in the following Table 1 and solution polymerization was carried out to prepare an acrylic copolymer.

2-ethylhexyl acrylate 29.2 n-butyl acrylate 6 Acrylic acid 2.8 2-hydroxyethyl (meth) acrylate 2 Ethyl acetate 60 100

(Silicone-treated TESA-7475 tape peel strength: 30 gf / 25.4 mm) was coated on the silicon-treated surface with a composition as shown in the following Table 2 to obtain a film thickness of 20 μm at 130 ° C. After heat curing for a minute, UV hardening 500 mj / cm 2 followed by delamination Silicone-treated release film 50 μm (silicone treated surface TESA-7475 tape peeling strength 10 gf / 25.4 mm) .

Example 1 Example 2 Comparative Example 1 A-1 92 92 92 Acrylonitrile butadiene copolymer One 6 18 Trimethylpropane triacrylate (TMPTA) 0.3 0.3 0.3 Photoinitiator 1-Hydroxy-cyclohexyl-phenyl-ketone 0.1 0.1 0.1 Epoxy hardener 0.3 0.3 0.3 TDI (isocyanate reactive curing agent) 0.5 0.5 0.5

Then, in order to measure the adhesion of the substrate, a polyester film having a film thickness of 20 μm was coated on the corona-treated polyester film in the same manner as in the following Table 2, followed by thermosetting at 130 ° C. for 5 minutes, ultraviolet curing after 500 mj / The silicone-treated side of the release film 50 占 퐉 (silicon-treated side TESA-7475 tape peeling strength 10 gf / 25.4 mm) was joined and aged for one day at 60 占 폚 again.

After aging, delamination The silicone-treated release film was peeled off to a thickness of 50 mu m, and the intermediate release silicone release film was peeled to 50 mu m to measure the elongation percentage of the adhesive layer to 20 mu m in the following manner. The coated sample on the corona- And the adhesion was measured. The measurement method is as follows, and the results are shown in Table 3.

Elongation (%) = (L1-L0) / L0 * 100

Substrate Adhesion: 100 cells are made by 10 coatings at 1mm intervals in the horizontal and vertical directions, and tesa7475 is attached at 2kg / ㎠.

Example 1 Example 2 Comparative Example 1 Elongation (%) 58 480 985 Substrate adhesion Great Great Bad

Test Example 1

On the polyester base film printed in 20 탆 black with the composition of Example 2, the coating film was thermally cured at 130 캜 for 5 minutes in the same manner as the experimental procedure of the above Examples and Comparative Examples, and then crosslinked by ultraviolet curing at 500 mj / cm 2. A pressure-sensitive adhesive to which a heat-resistant tackifier resin was applied on the upper surface of the elastic layer coated on the base film and a pressure-sensitive adhesive to which the heat-resistant tackifier resin was added was coated on both sides with a coating film thickness of 20 탆 and thermally crosslinked at 130 캜 for 5 minutes to form a base film layer, A crosslinked acrylic layer and a double-sided pressure-sensitive adhesive layer A sample having a total thickness of 80 μm was prepared and aged at 60 ° C. for 1 day.

The test of each physical property was carried out as follows. Table 4 shows the test results of the double-sided pressure-sensitive adhesive sheet (Comparative Example 2) using a commercially available thermosetting acrylic base layer and the double-sided pressure-sensitive adhesive sheet using the photocurable acrylic base layer (Comparative Example 3).

180 ° Adhesion (180 Peel strength)

1. Cut the specimen to be tested to 1 inch width using a 1 "Razor Cutter. (The length of the specimen is 100 mm.)

2. Wash the PC panel to be used with IPA (1 time) and heptane (3 times). After cleaning, make sure that there is no smudge on the surface of the PC panel, and if there is smudge, clean again.

3. Attach the sample piece of 1 inch width to be tested to the center of the cleaned PC panel. The liner of the test specimen is peeled off, and then a 25 탆 PET film is attached.

4. Using the Roll Down Machine, reciprocate the test specimen once at a speed of 300 mm / min with a 4.5 lbs (approx. 2 kg) roller.

5. After roll down, leave at room temperature for 30 minutes and measure the adhesive strength at 180 ° using UTM. The measurement speed is 300 mm / min.

6. The measurement result is calculated as the Integral Average of the values before and 15% of the data before and after the measurement.

retention holding power test

1. Attach the adhered material to SUS_304 with 25mm x 25mm.

2. Using a 2-kg roller, reciprocate once at a speed of 5 mm / sec.

3. Measure the temperature and humidity at 85 ℃, 85% after 30 minutes of rest.

4. Measure after 500g weight load (1 hour check).

5. Measure the fall time from the pushed distance or the adherend after the specified time, use the integer notation in millimeters, and the drop time in integer (min) units.

Peel Holding ( dead load Peel force ) exam

1. Tape a 25 mm wide and 80 mm long tape with a 2 Kg Roller, and leave it at room temperature for 30 minutes.

2. After leaving at room temperature, leave them at 85 ℃ dry heat or 85 ℃ and 85% humidity condition for 10 minutes to equalize the temperature of each material.

3. Apply a load (100 g) as shown in Fig.

4. Measure the distance between the fall of the tape and the tape peeled off after 60 minutes.

Impact resistance exam

1. Sample Preparation PC: 50 mm x 50 mm x 2 mm (w / 10 mm phi center hole), Tempered Glass: 20 mm x 20 mm x 2 mm, Sample Size (Bonding Area) Tape size: 3 mm x 20 mm x ² pcs at 20 N / After pressing, left for 30 minutes at room temperature (23 ° C * 50% RH), and then using Modified Dupon Type Tester, Drop Height: 5/10/15/20/25/30/35/40/45/50 cm, Weight : Prepare 100/110/120/130/140/150/160/170/180/190/200 g and peel off the protective film of the PC specimen and tempered glass specimen, wash the surface with organic solvent and dry. Washing solvent and sequence: IPA (purity 98% or more) Wash once, then wash 3 times with heptane (purity 98% or more).

2. Prepare a sample of the product to be tested with 3 mm width using a cutting machine.

3. Tape sample of 3mm width is attached to both sides of prepared tempered glass specimen of 20mm × 20mm specimen, and then tape sample is cut according to tempered glass specimen width (20mm).

4. Peel off the liner on the opposite side of the Tape Sample and attach it to the cleaned 50mm × 50mm PC specimen. (When attaching to the PC specimen, attach it to the center of the PC specimen center hole. )

5. Press the prepared test specimen using a pressurized equipment. At this time, the pressing condition is 20 N / cm ² , 60 seconds.

6. After pressurization, agitate at room temperature for 30 minutes. Then, prepare the test specimen to be tested in Jig of drop test equipment. Start the test by dropping 100 grams of weight at a height of 5 cm. If the sample fails to break or separate under these conditions, proceed to the next level. Increase the test level until the sample breaks and repeat. Record the condition (drop height / weight) when the sample breaks and check the failure mode of sample specimen.

Test Items Adherend Example 2 Comparative Example 2
N Company ( 908WAX ) Comparative Example 3
Company S (IA- 5308DW ) Tape Thickness ( 탆) 80 80 80
Adhesion ( gf / 25.4 mm)
sus 1691 1120 1551 PC 1969 1030
(Warrior- Substrate adhesion property NG ) 1797 GLASS 1878 1240 1479 retention Measure
(60 ° C * 1hr ) (mm) sus 0.3 0.7 0.5 pc 0.3 NG (23 min) drop 0.5 High temperature heat resistance test
peel holding test
(85 ° C * 1hr ) (cm) SUS

PC 3.1

2.8 NG (16 min) drop

NG (24 min) drop 5.2

6.4 Impact resistance (100 g) PC / GLASS 550 350 450 Substrate adhesion SUS , PC, GLASS Very good Bad (total transition)
( In particular,
Poor substrate adhesion property) Partial transfer
Adhesion of substrate to PC
Partial transfer phenomenon

FIG. 4 is a photograph showing the adhesion of the adherend to the adherend after the adherend (SUS304, PC) was adhered to the adherend after the adhering strength was measured. The left three specimens were SUS304 and the right three specimens were PC face.

In Comparative Example 2 (908WAX), the pressure-sensitive adhesive was completely transferred to SUS304 to the adherend of the left SUS304 material except for Example 2. In Comparative Example 3 (IA-5308DW), the pressure-sensitive adhesive was partially transferred to SUS304. In Comparative Example 2 (908WAX), the pressure-sensitive adhesive was completely transferred to the PC, and in Comparative Example 3 (IA-5308DW), the pressure-sensitive adhesive was partially transferred to SUS304.

In Comparative Example 2, which is a thermosetting base layer, the pressure-sensitive adhesive was entirely transferred due to a difference in cross-linking agent or crosslinking method, and the pressure-sensitive adhesive layer was entirely transferred. Comparative Example 3 (IA-5308DW) The adhesion of the substrate is insufficient to exhibit a partial transfer phenomenon. On the other hand, in the case of Example 2 in which the hybrid curing type was thermally crosslinked and photocured, regardless of the type of the adherend, the adhesion to the substrate was excellent, and it was clearly separated.

The Peel Holding test, a heat resistance test, was carried out under a load of 100 g under a dry condition at a test condition of 85 ° C. The peeling distance of the tape after the test and the adhesive transfer phenomenon are shown in Fig.

The results of FIG. 5 show that Example 2 was not peeled off even at a high temperature of 100 g load test at 85 ° C., but peeling of all the tape-adhered portions was observed in Comparative Example 2. In Comparative Example 3, the adhesive was partially peeled off and some adhesive transfer occurred.

In Comparative Example 2, which is a thermosetting base layer, the adhesive property of the substrate was insufficient due to the difference in the cross-linking agent or the crosslinking method, and the heat resistance was also poor. Comparative Example 3 (IA-5308DW), which is a photocurable base layer, lacks internal hardening due to photo-curing, and thus has poor heat resistance due to insufficient curing degree. Thus, in a 100 g load test at 85 ° C, . On the other hand, in Example 2 in which the hybrid curing type was thermally crosslinked and photocured, the heat resistance and the adhesion to the substrate were excellent, and no shrinking phenomenon was observed.

In conclusion, the block copolymer containing acrylonitrile butadiene elastomer exhibits excellent heat resistance, substrate adhesion, and high elasticity impact resistance than the simple thermo-cross-linkable or photo-curable type in the case of Example 2 in which the hybrid curing type by thermal crosslinking and photo- I could.

Claims

Wherein the thermosetting agent is an isocyanate-based, an epoxy-based, a peroxide-based, a metal-based adhesive, an acrylic-based copolymer, an acrylonitrile-butadiene block copolymer, a photoreactive acrylate, a photoinitiator, A chelating agent, and an oxazoline-based crosslinking agent.

delete

The double-faced pressure-sensitive adhesive sheet according to claim 1, wherein the thermosetting agent is a mixture of isocyanate-based and epoxy-based crosslinking agents.

The method of claim 1, wherein the photoactive acrylate is selected from the group consisting of 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA) Selected from the group consisting of erythritol hexaacrylate (DPHA), 1,2-ethylene glycol diacrylate, 1,12-dodecanediol acrylate and ethoxylated trimethylolpropane triacrylate (TMPEOTA). Sensitive adhesive sheet.

The double-faced pressure-sensitive adhesive sheet according to claim 4, wherein the photoreactive acrylate is trimethylolpropane triacrylate (TMPTA).