KR102596425B1 - Uv curable adhesive composition for micro led display and adhesive sheet using the same - Google Patents

Abstract

The present invention relates to an ultraviolet curable composition for a micro LED display and an adhesive film using the same. The ultraviolet curable composition includes a resin obtained by reacting a methacrylic acid ester polymer containing a hydroxyl group with a monoisocyanate monomer containing an acrylic group, , the methacrylic acid ester polymer containing the hydroxyl group is characterized in that the hydroxyl group value is 10 to 100 mgKOH/g based on solid content.

Description

Ultraviolet curable composition for micro LED displays and adhesive film for micro LED displays using the same. {UV CURABLE ADHESIVE COMPOSITION FOR MICRO LED DISPLAY AND ADHESIVE SHEET USING THE SAME}

The present invention relates to an ultraviolet curable composition for a micro LED display and an adhesive film for a micro LED display using the same. More specifically, an ultraviolet curable composition applicable to an adhesive film used in the micro LED display manufacturing process and adhesive using the same. It's about film.

In the manufacturing process of micro LED displays, various adhesive films such as micro LED wafer fixing film, carrier film, and transfer film are used. These adhesive films are similar to adhesive films for semiconductor processing, but because micro LEDs are smaller than semiconductors, they require better properties than dicing tapes for semiconductor manufacturing processes. That is, the adhesive strength before irradiation with ultraviolet rays is higher than that of the semiconductor dicing tape, and the adhesive strength after irradiation with ultraviolet rays requires lower non-adhesive properties than that of the semiconductor dicing tape.

Republic of Korea Patent Publication No. 10-2001858 discloses an acrylic adhesive composition having non-adhesive properties after UV curing. An aliphatic acrylate oligomer having a multifunctional group is copolymerized with a general acrylic adhesive, and after the copolymerization reaction, toluene and diphenylpentaerythritol hexaacrylate ( A composition of an adhesive that exhibits non-adhesive properties has been proposed by adjusting the weight average molecular weight by adding DPHA). However, these adhesive compositions do not have double bonds in the adhesive itself, so low-molecular-weight acrylic adhesives may remain on the adhesive after UV curing, and there is a problem in that adhesive strength sufficient to be applied to micro LEDs cannot be obtained.

In addition, Republic of Korea Patent Publication No. 10-1138796 also used an acrylic adhesive without double bonds and could be transferred to an adherend using a non-reactive dimethylsiloxane resin, so it is not suitable for use in the micro LED manufacturing process.

In addition, the acrylic adhesive described in Korean Patent Publication No. 10-1019063 has a double bond in the adhesive polymer main chain, so there is no residue problem, but it has low adhesiveness and high adhesiveness after ultraviolet irradiation, so it is not suitable for use in the micro LED manufacturing process.

Republic of Korea Patent Publication No. 10-2001858 Republic of Korea Patent Publication No. 10-1138796 Republic of Korea Patent Publication No. 10-1019063

The present invention was developed in consideration of the above-described prior art, and its purpose is to provide an ultraviolet curable composition that exhibits physical properties applicable to an adhesive film used in the micro LED display manufacturing process.

In particular, the purpose is to provide an ultraviolet curable composition that enables adhesion without residue through the difference in adhesion before and after ultraviolet irradiation, and an adhesive film using the same.

The ultraviolet curable composition for a micro LED display of the present invention to solve the above problems is obtained by reacting a monoisocyanate monomer containing an acrylic group with a methacrylic acid ester polymer containing a hydroxyl group. is characterized by a hydroxyl value of 10 to 100 mgKOH/g based on solid content.

At this time, the monoisocyanate monomer containing the acrylic group is prepared by reacting isophorone diisocyanate (IPDI) and hydroxy ethyl acrylate (HEA), and the NCO content is preferably 11 to 12%. do.

In addition, the adhesive film according to the present invention includes a substrate, an adhesive layer formed on one side of the substrate, and a release film laminated on the adhesive layer, wherein the adhesive layer includes the ultraviolet curable composition, a photoinitiator, and an epoxy curing agent. It is characterized by being made of an adhesive containing.

The ultraviolet curable composition according to the present invention exhibits physical properties that can be applied to the adhesive film used in the micro LED display manufacturing process. In particular, it exhibits the effect of enabling adhesion without residue through the difference in adhesive strength before and after ultraviolet irradiation.

Hereinafter, the present invention will be described in more detail. Terms or words used in this specification and claims should not be construed as limited to their common or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

The ultraviolet curable composition according to the present invention is obtained by reacting a monoisocyanate monomer containing an acrylic group with a methacrylic acid ester polymer containing a hydroxyl group. The methacrylic acid ester polymer containing a hydroxyl group has a hydroxyl value of 10 to 100 mgKOH based on solid content. It is characterized by /g.

If the hydroxyl value is 10 mgKOH/g or less, the double bond content of the adhesive obtained by reacting monoisocyanate monomers is lowered, thereby increasing the adhesive strength after ultraviolet curing. If the hydroxyl value is 100 mgKOH/g or more, the polarity of the adhesive increases and the viscosity increases. This may result in reduced workability and there is a risk of gelation during isocyanate reaction due to high viscosity, so it is preferable to use a methacrylic acid ester polymer that satisfies the range of the above hydroxyl value.

In addition, the acrylic group-containing monoisocyanate monomer is used in an amount of 50 to 90 equivalents based on 100 equivalents of the hydroxy monomer used when polymerizing methacrylic acid ester containing a hydroxyl group. Preferably, 80 equivalents of hydroxy monomer can be reacted. By applying the monoisocyanate monomer containing the acrylic group, the ultraviolet curable composition has high adhesive strength before ultraviolet irradiation, but can exhibit low non-adhesive properties after ultraviolet irradiation, making it suitable for application to adhesive films used in the micro LED display manufacturing process. It will appear.

In other words, in order to remove the residue caused by the adhesive, an acrylic adhesive containing a hydroxyl group is synthesized, and a double bond is introduced into the main chain of the acrylic adhesive through an addition reaction with a monoisocyanate containing an acrylic group, thereby creating a chemical structure that leaves no residue on the adherend. there is. In addition, the chemical structure is designed to allow for a decrease in adhesion after UV curing.

Specifically, the monoisocyanate monomer containing the acrylic group is prepared by reacting isophorone diisocyanate (IPDI) and hydroxy ethyl acrylate (HEA), and the NCO content is preferably 11 to 12%. do.

As the isocyanate monomer, a commercially available compound can be used, for example, VESTANAT EP-DC 1241 from EVONIC.

In addition, other types of monoisocyanates containing acrylic groups may be used or used in combination with the above-mentioned monoisocyanate monomers containing acrylic groups.

Other types of monoisocyanate monomers containing acrylic groups include 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, and 1,1-( Any one of 1,1-(bisacryloyloxymethyl) ethyl isocyanate), 2-(2-Isocyanatoethoxy)ethyl methacrylate, or You could use more than that.

Additionally, a methacrylic acid ester polymer containing a hydroxyl group can be used as the resin constituting the ultraviolet curable composition. The hydroxyl group-containing methacrylic acid ester polymer can be produced by polymerizing acrylic monomers, and these polymers contain a hydroxyl group-containing acrylic monomer as one of the copolymerization monomer components. In one embodiment, a polymerization initiator is added to a mixture of acrylic monomers consisting of 50 to 70 parts by weight of 2-ethylhexyl acrylate, 10 to 20 parts by weight of butyl acrylate, 10 to 20 parts by weight of hydroxyethyl acrylate, and 1 to 5 parts by weight of acrylic acid. The above resin with a hydroxyl value of 48 to 97 mgKOH/g (based on solid content) can be prepared by adding and polymerizing a solvent. Additionally, the solvent may be any one of ethyl acetate, cyclohexane, n-hexane, acetone, dimethyl carbonate, methanol, ethanol, and isopropyl alcohol, or a mixture thereof.

An adhesive for an adhesive film can be manufactured by mixing a photoinitiator and an epoxy curing agent in the ultraviolet curable composition.

The adhesive film is composed of a substrate, an adhesive layer formed on one side of the substrate, and a release film laminated on the adhesive layer. The adhesive layer has a thickness of 10 to 100 after drying, considering the performance of the release film. It is desirable to form it to ㎛. More preferably, it is desirable to set it to 20 to 50㎛.

The base material includes a resin selected from polyethylene, polypropylene, polyethylene terephthalate, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyurethane, polystyrene, polycarbonate, fluororesin, and triacetyl cellulose. Film can be used, and polyethylene terephthalate (PET) film is preferred.

Additionally, the release film having release properties can also be made of the same type of material as the substrate. The substrate can generally be appropriately selected from a thickness range of 1 to 188 ㎛, and the thickness of the substrate may vary depending on the material or purpose of the substrate used.

In addition, when forming the adhesive layer, the adhesive is applied to the substrate. At this time, the viscosity is adjusted to a level suitable for the application operation, and then the adhesive layer can be formed by applying it on the substrate and curing. The adhesive layer can be prepared using conventional adhesive sheets such as the bar coat method, reverse roll coat method, knife coat method, roll knife coat method, gravure coat method, doctor blade coat method, slot die coat method, comma coat method, and micro gravure coat method. It can be formed by the method used in manufacturing, and the adhesive layer can be formed by applying the adhesive and then drying and curing it.

The effects according to the present invention will be explained through examples below.

[Mono isocyanate with acrylic group]

a1) Synthesis of monomer represented by formula 1

Add 2.2 g of BHT and 0.02 g of DBTDL to 222 g (1 mol) of IPDI (isophorone diisocyanate), raise the temperature to 70°C while stirring, add 116 g (1 mol) of HEA (hydroxy ethyl acrylate) dropwise, and react completely for 2 to 4 hours. . The NCO content of this product is 11.8%.

a2) Commercially available monomer: VESTANAT EP-DC 1241 from EVONIC (NCO content 11.6%, IPDI content 0.05 wt. %)

[Resin synthesis]

Prepare a reaction device equipped with a stirrer, reflux cooler, nitrogen introduction tube, thermometer, and dropping tank, and add 66 g of 2-Ethyl hexyl acrylate (2-EHA) monomer and n-Butyl acrylate. 100 g of an acrylic mixture consisting of 15 g of n-BA) monomer, 15 g of 2-Hydroxy ethyl acrylate (2-HEA) monomer, and 4 g of acrylic acid (AA) was prepared, and among the prepared acrylic mixture 30g, 0.05g of polymerization initiator (AIBN, Azobis isobutyronitrile) and an appropriate amount of solvent (ethyl acetate) were added to the reactor and heated to 80°C to confirm the start of the reaction. 0.5g of polymerization initiator (AIBN, Azobis isobutyronitrile) and solvent (acetic acid) were added to the reactor. Appropriate amounts of ethyl) and the remaining 70 g of the acrylic mixture were added dropwise for 1 hour each and reacted for 5 hours while maintaining reflux. After the reaction was completed, cooled and mixed with ethyl acetate to obtain a non-volatile content of 30% and a hydroxyl value of 72.5 mgKOH/ g (based on solid content) of methacrylic acid ester polymer was synthesized.

<Examples 1 to 3>

1. Preparation of adhesive composition

For 100 parts by weight of the ethyl acetate solution (non-volatile matter concentration: 30% by weight) of the obtained methacrylic acid ester polymer, 80 equivalents of monoisocyanate with an acrylic group as shown in Table 1 were added to 100 equivalents of 2-hydroxyethyl acrylate units, 0.01 parts by weight of dibutyltin dilaurate was added as a catalyst, and addition reaction was carried out at 50°C for 5 hours to obtain a solution of reactive methacrylic acid ester polymer.

<Comparative Example 1>

The polymer composition of Comparative Example 1 was obtained in the same manner as Example 1.

However, in Comparative Example 2, dipentaerythritol hexaacrylate (DPEHA) was simply added and mixed to the obtained resin to obtain a polymer composition.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 profit 100 100 100 100 100 MOI - - 3.4 4.8 - a1 10.5 - - - - a2 - 10.5 3.14 - - DPEHA - - - - 5

In Table 1, the MOI is 2-isocyanatoethyl methacrylate. a1 is the synthesized monomer (NCO content 11.8%), and a2 is VESTANAT EP-DC 1241 from EVONIC (NCO content 11.6%, IPDI content 0.05 wt. %).

2. Application process of adhesive composition

An adhesive was prepared by adding 1 g of photoinitiator TPO and 0.4 g of 2% epoxy curing agent (N,N,N',-tetraglycidiyl-m-xylenediamine; brand name Tetrad-X) to the polymer obtained in Table 1.

Next, a pressure-sensitive adhesive layer was applied with a knife-type coater to a 100-μm-thick charged polyethylene terephthalate film as an optical film substrate so that the thickness after drying was 20 μm.

Subsequently, drying treatment was performed at 110°C for 1 minute to form an adhesive layer, and then a charged polyethylene terephthalate release film with a thickness of 50 μm as a release film was laminated by closely adhering to the obtained adhesive layer, resulting in substrate/adhesive layer/release. A laminate consisting of a film was obtained. Afterwards, it was aged at 43°C for 48 hours to prepare an adhesive film for the micro LED manufacturing process.

3. Measurement of physical properties

<Adhesion>

Adhesion was measured using UTM equipment according to KS T 1028. A 25 mm wide tape was pressed to a SUS304 adherend using a rubber roller (2.0 kg load) and left at room temperature for 30 minutes, and the 180° Peel value was measured at a speed of 300 mm/min.

<Measurement of adhesion after UV irradiation>

After irradiating with ultraviolet rays at a light quantity of 600 mJ/cm2, the adhesive strength was measured.

<residue>

The presence or absence of residues was determined by observing the adherend (SUS) under a microscope after peeling to determine whether there was an adhesive component in the adherend.

○: There is no adhesive component on the adherend after peeling.

×: After peeling, there is at least some adhesive component in the adherend.

The measurement results are shown in Table 2.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Adhesion (gf/25㎜) 3100 3150 3050 2850 2050 Adhesion after UV irradiation
(gf/25㎜) 2 2 3 15 13 Whether or not residues are generated ○ ○ ○ ○ ×

From the measurement results in Table 2, it was confirmed that the adhesive film to which the ultraviolet curable composition according to the present invention was applied had a large difference in adhesive strength before and after ultraviolet irradiation and no residue was generated, making it suitable for application to the micro LED display manufacturing process.

Although the present invention has been described with reference to preferred embodiments as described above, it is not limited to the above embodiments and various modifications and modifications may be made by those skilled in the art without departing from the spirit of the present invention. Change is possible. Such modifications and variations should be considered to fall within the scope of the present invention and the appended claims.

Claims (3)

It includes a resin obtained by reacting a methacrylic acid ester polymer containing a hydroxyl group with a monoisocyanate monomer containing an acrylic group,
The methacrylic acid ester polymer containing the hydroxyl group has a hydroxyl value of 10 to 100 mgKOH/g based on solid content,
The monoisocyanate monomer containing the acrylic group is produced by reacting isophorone diisocyanate (IPDI) and hydroxy ethyl acrylate (HEA), and is characterized in that the NCO content is 11 to 12%. Ultraviolet curable composition for micro LED display.
delete An adhesive film comprising a substrate, an adhesive layer formed on one side of the substrate, and a release film laminated on the adhesive layer,
The adhesive layer is an adhesive film for a micro LED display, characterized in that it is made of an adhesive containing the ultraviolet curable composition according to claim 1, a photoinitiator, and an epoxy curing agent.