KR20200095134A - Adhesive composition with oligomer blocking property and film comprising same - Google Patents

Abstract

An adhesive composition according to the present invention can have oligomer barrier properties by increasing the curing density by adjusting the content of a reactive group and the content of a curing agent in an adhesive resin. As a result, a film having an adhesive layer formed from the adhesive composition can block oligomers precipitated from a substrate layer at high temperature and maintain adhesive strength. Accordingly, the film according to the present invention can provide excellent adhesion while preventing oligomer precipitation at a high temperature even without special treatment for blocking oligomers on a conventional PET film as a base layer.

Description

An oligomer barrier adhesive composition and a film comprising the same TECHNICAL FIELD [0002] Adhesion composition with OLIGOMER BLOCKING PROPERTY AND FILM COMPRISING SAME

The present invention relates to an oligomeric barrier adhesive composition and a film comprising the same. More specifically, the present invention relates to a heat-resistant protective film based on a polyethylene terephthalate (PET) film.

A liquid crystal display (LCD) is one of the flat panel displays that are currently widely used, and as the use of liquid crystal displays increases in recent years, the use of materials constituting the liquid crystal display is also increasing. Among them, various transparent plastic materials are widely used in areas requiring particularly high transparency while replacing materials such as metal and glass. In addition, since the panel surface of the liquid crystal display is exposed to the outside, a film for protecting the panel from various external stimuli is applied.

As a film applied to such a display, a polyethylene terephthalate (PET) film having excellent optical properties and heat resistance is mainly used. However, when the PET film is heat-treated at a high temperature (eg, 150°C or higher), oligomers present in the PET film are precipitated, thereby reducing physical properties and excessively increasing adhesion. In addition, when oligomers are precipitated from the adhesive layer, the adherend is deformed, and the deformed adherend becomes heat-set, causing product defects. In order to solve this, it is known to use a PET film of a low oligomer type, or to form a primer layer or a hard coating layer for blocking oligomers on the PET film.

In addition, Korean Laid-Open Patent Publication No. 2011-0095915 discloses modifying a part of the film surface by exposing it to ultraviolet rays in order to prevent precipitation of oligomers on the surface of the hard coat film. However, the modified film has a problem in that optical properties such as light transmittance and haze are poor.

Korean Patent Application Publication No. 2011-0095915

In general, in the display manufacturing process, high-temperature heat treatment is performed together with an optical film or a protective film, but the PET film used for this is protected in a post-process by deteriorating the physical properties of the optical film or excessively increasing the adhesive strength due to the precipitation of oligomers at high temperature. There was a problem that it was difficult to remove the film.

For this reason, conventionally, referring to FIG. 2, a hard coating layer 220 for blocking oligomers and an adhesive layer 230 for application to a product are formed together on the surface of the PET film 210, but such a film configuration There was a problem of increasing the cost through many process steps.

Accordingly, as a result of research by the present inventors, by adjusting the content of the reactive group of the adhesive polymer resin and the content of the curing agent to increase the curing density, it was possible to develop a pressure-sensitive adhesive composition having adhesiveness with oligomer barrier properties.

Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive composition for forming an adhesive layer capable of blocking oligomers at high temperature and maintaining an appropriate adhesive strength.

Another object of the present invention is to provide a film comprising the adhesive layer to block oligomers precipitated from the substrate layer at high temperature and maintain proper adhesiveness.

According to the above object, the present invention 100 parts by weight of a pressure-sensitive adhesive resin having a hydroxyl value (OHV) of 10 to 18 mgKOH / g; And it provides a pressure-sensitive adhesive composition comprising 5 to 12 parts by weight of a curing agent.

According to the other object, the present invention is a base layer; And an adhesive layer formed on one side of the base layer, wherein the adhesive layer is formed from the adhesive composition.

The pressure-sensitive adhesive composition according to the present invention may have oligomer barrier properties by increasing the curing density by adjusting the content of the reactive group and the curing agent in the pressure-sensitive adhesive resin.

As a result, a film having an adhesive layer formed from the adhesive composition can block oligomers precipitated from the substrate layer at high temperature and maintain adhesive strength.

Accordingly, the film according to the present invention can provide excellent adhesion while preventing oligomer precipitation at high temperature even without special treatment to block oligomers on a conventional PET film as a base layer.

1 shows an example of a cross-sectional view of the film of the present invention.
Figure 2 shows an example of a cross-sectional view of a conventional hard coating film.

Hereinafter, the present invention will be described in more detail.

In the following description, in the case where each layer or film is described as being formed on or under another layer or film, both directly or through other constituent elements are included.

In addition, the size of each component in the drawings may be exaggerated for description.

[Adhesive composition]

The pressure-sensitive adhesive composition according to the present invention comprises 100 parts by weight of a pressure-sensitive adhesive resin having a hydroxyl value (OHV) of 10 to 18 mgKOH/g; And 5 to 12 parts by weight of a curing agent.

Adhesive resin

The pressure-sensitive adhesive resin exhibits adhesive properties as a main component of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive resin has a reactive group such as an OH group, and may be cured by reacting with the reactive group of the curing agent.

In the pressure-sensitive adhesive composition according to the present invention, the content of the reactive group of the pressure-sensitive adhesive resin, in particular, the hydroxyl value (OHV) is controlled to improve the curing density.

For example, the hydroxyl value (OHV) of the pressure-sensitive adhesive composition is 10 to 18 mgKOH/g, 10 to 16 mgKOH/g, 10 to 14 mgKOH/g, 12 to 18 mgKOH/g, 14 to 18 mgKOH/g, or It may be from 12 to 16 mgKOH/g. Specifically, the pressure-sensitive adhesive resin may have a hydroxyl value (OHV) of 12 to 16 mgKOH/g.

The pressure-sensitive adhesive resin may include an acrylic pressure-sensitive adhesive resin.

The acrylic polymer may be formed by polymerizing an acrylic monomer.

The acrylic monomers are 2-ethylhexyl acrylate (2-EHA), butyl acrylate (BA), methyl acrylate (MA), vinyl acetate (VAc), acrylic acid (AA), and 2-hydroxyethyl acrylate (2 It may be a resin in which at least two monomers selected from the group consisting of -HEA) are copolymerized.

In addition, the pressure-sensitive adhesive resin may include a pressure-sensitive adhesive (PSA) resin. Specifically, the pressure-sensitive adhesive resin may include an acrylic pressure-sensitive adhesive (PSA) resin.

The weight average molecular weight (Mw) of the pressure-sensitive adhesive resin may be 5,000 to 2,000,000 g/mol, 10,000 to 1,000,000 g/mol, or 50,000 to 500,000 g/mol.

Hardener

The curing agent serves to cure by reacting with a reactive group such as an OH group of the pressure-sensitive adhesive resin. That is, the curing agent contains a group capable of reacting with the reactive group of the pressure-sensitive adhesive resin.

For example, the curing agent may have one or two or more groups selected from the group consisting of an epoxy group, an isocyanate group, a carboxyl group, a hydroxyl group, an acrylic group, a methacrylic group, an acetate group, and a vinyl group.

The curing agent may include a thermosetting agent, a photocuring agent, or a combination thereof.

The thermosetting agent may be an isocyanate-based, epoxy-based, or metal chelate-based compound. The isocyanate compound may be a polyfunctional aromatic or aliphatic isocyanate compound, and the epoxy compound may have one or two or more epoxy groups, and the metal chelate compound may be Zn, Ni, Mn, Fe, Co, Cr, Metal components such as Al, Ti, and Zr may be included.

The photocuring agent may include a multifunctional acrylic compound, and may be, for example, one or more selected from the group consisting of diacrylate and triacrylate. As specific examples of the photocuring agent, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate (HDDA), 1,9-nonanediol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol Diacrylate, trimethylolpropane triacrylate, and pentaerythritol triacrylate.

Subsidy

The pressure-sensitive adhesive composition may have oligomer barrier properties by adjusting the ratio between the curing agent and the reactive group of the pressure-sensitive adhesive resin to increase the curing density. To this end, the content of the curing agent may be adjusted in comparison to the content of the pressure-sensitive adhesive resin.

The curing agent may be included in an amount of 5 to 12 parts by weight, 5 to 10 parts by weight, 5 to 8 parts by weight, 7 to 12 parts by weight, 9 to 12 parts by weight, and 7 to 10 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive resin. Specifically, the curing agent may be included in 6 to 9 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive resin. In this case, the content of the curing agent and the content of the pressure-sensitive adhesive resin may be based on solid content.

In addition, the pressure-sensitive adhesive resin and the curing agent 1:1 to 1:2, 1:1 to 1:1.5, 1:1.1 to 1:1.5, 1:1.1 to 1:1.3, 1:1.3 to 1:1.5, or 1 It may be included in an equivalent ratio of :1 to 1:1.3. Specifically, the pressure-sensitive adhesive resin and the curing agent may be included in an equivalent ratio of 1:1 to 1:1.5. The equivalent ratio may be a molar equivalent ratio between the OH group of the pressure-sensitive adhesive resin and the reactive group of the curing agent.

The pressure-sensitive adhesive resin may be included in the range of 35% by weight to 95% by weight based on the weight of the pressure-sensitive adhesive composition. Specifically, the pressure-sensitive adhesive resin is in the range of 40% to 90% by weight, 45% to 85% by weight, 50% to 80% by weight, 60% to 90% by weight based on the weight of the pressure-sensitive adhesive composition , Or may be included in the range of 70% to 90% by weight. In this case, the content of the pressure-sensitive adhesive resin and the weight of the pressure-sensitive adhesive composition may be based on solid content.

Characteristics after curing

The pressure-sensitive adhesive composition may be uncured or cured. That is, the pressure-sensitive adhesive resin in the pressure-sensitive adhesive composition may not react with the curing agent or may exist in a reacted state. Alternatively, the pressure-sensitive adhesive composition may be partially cured.

The pressure-sensitive adhesive composition may have optical properties and adhesive properties required for an optical film or a protective film after curing.

For example, the adhesive force after curing of the pressure-sensitive adhesive composition may be 5 to 40 gf/inch, 5 to 30 gf/inch, 5 to 25 gf/inch, or 10 to 20 gf/inch. Specifically, the pressure-sensitive adhesive composition may have an adhesive strength of 5 to 20 gf/inch after curing. When within the above range, the pressure-sensitive adhesive composition is formed as a protective film and can be easily removed in a post-process while maintaining adhesive strength during a product process. The adhesive force may be measured at room temperature or at room temperature to 60°C, and may be measured for a glass substrate, a polyimide substrate, or the like.

In addition, the transmittance of the pressure-sensitive adhesive composition to light having a wavelength of 550 nm after curing may be 70% or more, 80% or more, 85% or more, or 90% or more.

In addition, the haze after curing of the pressure-sensitive adhesive composition may be 15% or less, 10% or less, 5% or less, 3% or less, or 1% or less.

Specifically, the pressure-sensitive adhesive composition may have a transmittance of 90% to 95% and a haze of 0.1% to 1.5% for light having a wavelength of 550 nm after curing.

When it is within the above range, it is advantageous to use the pressure-sensitive adhesive composition as an optically transparent adhesive (OCA).

After curing, the pressure-sensitive adhesive composition may have a modulus of 10 ⁶ Pa or more, 10 ⁷ Pa or more, or 10 ⁸ Pa or more at a glass transition temperature (Tg). The modulus after curing is a characteristic capable of estimating the curing density (crosslinking density), and is more advantageous in preventing the precipitation of oligomers when the modulus at the glass transition temperature after curing is within the above range. For example, the pressure-sensitive adhesive composition may have a modulus of 10 ⁶ Pa to 10 ¹⁰ Pa, 10 ⁶ Pa to 10 ⁹ Pa, or 10 ⁶ Pa to 10 ⁸ Pa at a glass transition temperature (Tg) after curing.

[film]

1 shows an example of a cross-sectional view of the film of the present invention.

Referring to FIG. 1, the film 100 according to the present invention includes a base layer 110; And an adhesive layer 120 formed on one surface of the base layer 110, wherein the adhesive layer 120 is formed from the adhesive composition.

Base layer

The base layer serves to impart mechanical strength to the film while supporting the adhesive layer.

The base layer may include one or more resins selected from the group consisting of polyester resins, polyurethane resins, and polyolefin resins. Specifically, the base layer may include a polyethylene terephthalate (PET) resin.

The thickness of the base layer may be 5 µm to 1000 µm, 5 µm to 500 µm, 5 µm to 300 µm, 10 µm to 250 µm, 50 µm to 200 µm, or 100 µm to 200 µm.

Adhesive layer

The adhesive layer is formed on one surface of the base layer and serves to impart adhesive force between the film and another object.

The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition, and specifically, is formed by curing the pressure-sensitive adhesive composition. Specifically, the adhesive layer may include a reaction product, that is, a cured product between the adhesive resin and the curing agent.

When the thickness of the adhesive layer is thin, the adhesive strength decreases, and when the thickness of the adhesive layer becomes thick, the adhesive strength may increase after heat treatment. Therefore, controlling the thickness range of the adhesive layer is more advantageous in realizing the desired adhesive force.

For example, the thickness of the adhesive layer may be 5 µm to 1000 µm, 5 µm to 500 µm, 5 µm to 300 µm, 5 µm to 100 µm, 10 µm to 100 µm, or 5 µm to 50 µm. Specifically, the adhesive layer may have a thickness of 5 to 30 μm.

The adhesive layer may have optical properties and adhesive properties required for an optical film or a protective film.

For example, the adhesive force of the adhesive layer may be 5 to 40 gf/inch, 5 to 30 gf/inch, 5 to 25 gf/inch, or 10 to 20 gf/inch. Specifically, the adhesive layer may have an adhesive force of 5 to 20 gf/inch. When within the above range, the adhesive layer is attached to the object to be protected and can be easily removed in a post process while maintaining the adhesive strength during the product process.

In addition, the transmittance of the adhesive layer to light having a wavelength of 550 nm may be 70% or more, 80% or more, 85% or more, or 90% or more. In addition, the haze of the adhesive layer may be 15% or less, 10% or less, 5% or less, 3% or less, or 1% or less. When it is within the above range, it is advantageous for the adhesive layer to be utilized as an optically transparent adhesive (OCA) layer.

In addition, the adhesive layer may have a modulus of 10 ⁶ Pa or more, 10 ⁷ Pa or more, or 10 ⁸ Pa or more at a glass transition temperature (Tg).

The film according to the present invention may block oligomers deposited from the substrate layer at high temperature and maintain adhesive strength by having an adhesive layer in which the content of the reactive group and the curing agent in the adhesive resin is adjusted.

Characteristics of the film at high temperatures

The film can effectively block oligomers precipitated from the substrate layer at high temperatures by the adhesive layer. Due to such characteristics, when the film is used as an optical film, it is possible to prevent oligomers from penetrating the adhesive layer and depositing from the base layer under high temperature conditions during product processing, thereby impairing optical properties.

For example, when the film is heated at 150° C., 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 5 hours to 20 hours, until the oligomer precipitates from the base layer to the adhesive layer, Alternatively, it may take 7 to 15 hours.

Specifically, when the film is heated at 150° C., it may take 5 hours or more for the oligomer to precipitate from the base layer to the adhesive layer.

The film has a small increase in adhesive strength at high temperature, and thus can maintain an appropriate adhesive strength. Due to such characteristics, when the film is used as a protective film, it is possible to prevent the problem of excessively increasing adhesive strength under high temperature conditions during a product process, making it difficult to remove the protective film in a post process.

For example, the adhesive layer may have an adhesive strength of 5 gf/inch to 30 gf/inch, 5 gf/inch to 20 gf/inch, or 5 gf/inch to 15 gf/inch after heat treatment at 150°C for 3 hours have.

In addition, the adhesive layer, after 12 hours heat treatment at 150 ℃, compared to the initial 30 gf/inch or less, 25 gf/inch, less than 20 gf/inch, less than 15 gf/inch, or less than 10 gf/inch Can represent.

Specifically, the adhesive layer may exhibit a change in adhesive force of less than 20 gf/inch compared to the initial period after heat treatment at 150° C. for 12 hours.

[Example]

The present invention will be described in more detail through the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

The pressure-sensitive adhesive resin used in the following Examples and Comparative Examples is as follows:

-Adhesive resin A: acrylate-based adhesive resin, OHV 14 mgKOH/g

-Adhesive resin B: acrylate-based adhesive resin, OHV 9 mgKOH/g, hard type

-Adhesive resin C: acrylate-based adhesive resin, OHV 9 mgKOH/g, soft type

Examples and Comparative Examples

Step 1) Preparation of pressure-sensitive adhesive composition

Each of the pressure-sensitive adhesive compositions was prepared by mixing any one of pressure-sensitive adhesive resins A to C and an isocyanate-based curing agent in the amounts shown in Table 1 below. The molar equivalent ratio between the OH group of the pressure-sensitive adhesive resin and the reactor of the curing agent is also shown in Table 1 below.

Step 2) Preparation of the film

The pressure-sensitive adhesive composition prepared above was coated on a PET film having a thickness of 125 μm and cured at 120° C. for 2 minutes. Afterwards, further curing was performed at 60° C. for 72 hours for a complete curing reaction. As a result, an adhesive layer having a thickness of 10 μm was formed on the PET film.

Test example

The films of the Examples and Comparative Examples were tested as follows, and the results are shown in Table 1.

(1) Modulus

For each adhesive composition cured under the conditions of Examples and Comparative Examples (that is, each adhesive layer prepared in Examples and Comparative Examples), the modulus was increased by increasing the length at the glass transition temperature (Tg) and measuring the corresponding stress. Was calculated.

As a result, in the case of the pressure-sensitive adhesive composition cured under the conditions of Examples 1 to 3, it was measured to have a modulus of 10 ⁶ Pa or more at the glass transition temperature, and in the case of the pressure-sensitive adhesive composition cured under the conditions of Comparative Examples 1 and 2, the glass transition It was determined to have a modulus of 10 ⁴ Pa or less at temperature.

From this, it can be seen that the pressure-sensitive adhesive composition cured under the conditions of Examples 1 to 3 has a higher curing density (crosslinking density) than in Comparative Examples 1 and 2.

(2) Oligomer precipitation time

While the film sample was heat-treated in an oven at 150° C., the oligomer deposited on the surface of the adhesive layer was observed under a microscope, and the time at which the oligomer began to be discovered was measured.

(3) adhesion

The 180° peeling strength of the film sample was measured according to JIS K6854-2. In addition, the film sample was heat-treated in an oven at 150° C. every 3 hours, and the peel strength was measured in the same manner as before.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 adhesive
Suzy Kinds Suzy A Suzy A Suzy A Suzy B Resin C OHV
(mgKOH/g) 14 14 14 9 9 content
(Parts by weight) Adhesive resin 100 100 100 100 100 Hardener 7.0 8.5 10.0 7.0 7.0 Equivalent ratio Adhesive resin: hardener 1: 1 1: 1.2 1: 1.4 1: 1.4 1: 1.4 Oligomer
Precipitation (hr) 150℃
During heat treatment 9 10 12 3 0.5 150℃
After heat treatment
Change in adhesion
(gf/25mm) 0 hours 5.5 5.9 7.3 6.7 7.4 3 hours 7.6 10.1 12.2 25.9 43.2 6 hours 10.5 11.9 22.2 43.9 70.3 9 hours 11.7 15.2 22.6 66.0 72.8 12 hours 11.5 16.6 26.1 53.2 71.0

As shown in Table 1, in the films of Examples 1 to 3, the content of the reactive group and the curing agent in the pressure-sensitive adhesive resin was adjusted to a preferable range, so that oligomer precipitation was suppressed under high temperature conditions, and the change in adhesion was not large.

On the other hand, in the films of Comparative Examples 1 and 2, the content of the reactive group and the curing agent in the pressure-sensitive adhesive resin was out of the preferred range, so that oligomer precipitation was increased under high temperature conditions, and the adhesive strength was also significantly changed.

100: a film according to an example of the present invention, 110: a base layer,
120: oligomer barrier adhesive layer, 200: conventional hard coating film,
210: PET film, 220: hard coating layer (oligomer blocking layer),
230: adhesive layer.

Claims (14)

100 parts by weight of an adhesive resin having a hydroxyl value (OHV) of 10 to 18 mgKOH/g; And
A pressure-sensitive adhesive composition comprising 5 to 12 parts by weight of a curing agent.
The method of claim 1,
The curing agent is contained in an amount of 6 to 9 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive resin.
The method of claim 1,
The pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive resin has a hydroxyl value (OHV) of 12 to 16 mgKOH/g.
The method of claim 1,
After curing the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition has an adhesive strength of 5 to 20 gf/inch.
The method of claim 1,
After the pressure-sensitive adhesive composition is cured
Transmittance of 90% to 95% for light of 550 nm wavelength, and
Having a haze of 0.1% to 1.5%, the pressure-sensitive adhesive composition.
The method of claim 1,
After curing the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition has a modulus of 10 ⁶ Pa or more at a glass transition temperature (Tg).
The method of claim 1,
The pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive resin comprises an acrylic pressure-sensitive adhesive (PSA) resin.
The method of claim 1,
The pressure-sensitive adhesive composition and the curing agent is contained in an equivalent ratio of 1:1 to 1:1.5.
Base layer; And
Including an adhesive layer formed on one side of the base layer,
The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition of claim 1, a film.
The method of claim 9,
The adhesive layer has an adhesive force of 5 to 20 gf / inch, a film.
The method of claim 10,
The adhesive layer, after 12 hours heat treatment at 150 °C, showing a change in adhesive force of less than 20 gf / inch compared to the initial film.
The method of claim 9,
When the film is heated at 150° C., it takes 5 hours or more for the oligomer to precipitate from the base layer to the adhesive layer.
The method of claim 9,
The adhesive layer has a thickness of 5 to 30 ㎛, film.
The method of claim 9,
The base layer is a film comprising a polyethylene terephthalate (PET) resin.

Images