KR100894805B1 - Pressure Sensitive Adhesive Composition - Google Patents

Abstract

The present invention comprises an acrylic monomer, a crosslinking agent, and a solvent, and further comprises 5 to 30 parts by weight of a hydrocarbon resin relative to the acrylic monomer, wherein the pressure-sensitive adhesive composition is coated on one surface of a polyethylene terephthalate film with a thickness of 50 μm. When the adhesive strength is measured by adhering to SUS afterward, the adhesive strength is within 1 to 1.5 times within 1 hour after adhesion in preparation for 20 minutes after adhesion, and after 2 hours after adhesion, it is more than 2 times. The initial adhesive force is low and the late adhesive force provides a pressure-sensitive adhesive composition that increases with time.

Adhesive, adhesive strength

Description

Pressure Sensitive Adhesive Composition

The present invention relates to an adhesive composition.

In general, in order to manufacture a liquid crystal display panel, a liquid crystal cell and a polarizing plate including a liquid crystal are basically required. In order to coalesce it, an appropriate adhesive or adhesive layer should be used. In addition, in order to improve the function of the liquid crystal panel, an additional retardation plate or a light recovery plate may be additionally attached and used.

First, the main structure of the liquid crystal panel; 1) on the basis of a liquid crystal cell composed of a liquid crystal layer, a transparent glass plate including a transparent electrode layer or an acrylic plate-like material, which are constantly arranged; 2) It is generally constructed to include a polarizing plate, a retardation plate, and additional functional film layers having a multilayer structure incorporated into an adhesive layer or an adhesive layer.

The polarizing plate generally includes a iodine or a dichroic polarizing material arranged in a predetermined direction as described above, and is generally configured in a multilayered shape using a protective film on both sides to protect it. The retardation plate has a shape having a unidirectional molecular arrangement. It is expected that each of the films mentioned herein is made of a material having a different molecular structure and composition, and therefore each has different physical properties. In particular, the aging characteristics of the material appearing when the liquid crystal panel is used for a long time, the molecular structure changes over time. For example, 1) the effect of continuous strain stress between the film due to the temperature change due to the difference in the coefficient of linear expansion of the material, and 2) the stress relaxation of materials with unidirectional molecular alignment after a long time. Contraction and the like. In order to produce a liquid crystal panel by incorporating these materials, an adhesive or a pressure-sensitive adhesive must be used.

Conventional techniques for producing pressure-sensitive adhesives used in these optical films include an interface between a glass plate and a polarizing plate by adding a silane coupling agent to improve the durability of the adhesive film under heat and moisture resistance test conditions of a liquid crystal panel with a polarizing plate. The characteristic may be improved effectively. In addition, by using a high molecular weight acrylic resin from which the low molecular weight portion has been removed as an adhesive, the elastic modulus and adhesive properties of the adhesive layer are simultaneously improved to reduce the occurrence of fine bubbles generated between the glass plate and the adhesive layer, and to prevent peeling of the adhesive layer. The purpose was to. In addition, the use of a high molecular weight acrylic pressure-sensitive adhesive was adjusted to improve the high temperature adhesive strength by controlling the crosslinking density in a specific range, and when using a high molecular weight resin, the crosslinking density was severely changed according to the amount of crosslinking agent used. There is a disadvantage in that the adjustment is very difficult, in the case of the pressure-sensitive adhesive prepared by the above technique, all have a high initial adhesive property, there is a problem that it is difficult to re-peel again when the adhesion error.

In the currently used pressure-sensitive adhesive, the glass used in manufacturing the liquid crystal panel is becoming thinner and larger in size, and when a bad product occurs during initial attachment, the pressure-sensitive adhesive is removed from the liquid crystal cell, and the liquid crystal cell is washed. In this case, if the adhesive with high adhesive strength, which is used in the past, is used as it is, it is difficult to remove the adhesive due to its high adhesive force upon re-peeling, and sometimes expensive liquid crystal cells are destroyed. Required.

The present invention is to solve the above problems, not only excellent re-peelability at the time of initial adhesion, but also after the adhesion to the liquid crystal cell increases the adhesive force over time, there is no bubble or peeling phenomenon To provide a composition.

The present invention for achieving the above object, an acrylic monomer, a crosslinking agent, a solvent, and provides a pressure-sensitive adhesive composition characterized in that it further comprises 5 to 30 parts by weight of a hydrocarbon resin relative to the acrylic monomer.

In addition, when the pressure-sensitive adhesive composition is coated on one side of the polyethylene terephthalate film with a thickness of 50 μm, the adhesive composition is attached to SUS, and the adhesive strength is measured. The adhesive strength is 1 to 1 hour after adhesion in comparison to the adhesive strength of 20 minutes after the adhesion. It is within 1.5 times, and after 24 hours after adhesion provides a pressure-sensitive adhesive composition, characterized in that more than twice.

In addition, the present invention provides a pressure-sensitive adhesive composition comprising a vinyl acetate.

In addition, the acrylic monomer is 2-ethylhexyl acrylate, ethyl acrylate, acrylic acid, 55 to 65 parts by weight of 2-ethylhexyl acrylate, 15 to ethyl acrylate based on 100 parts by weight of the total of the acrylic monomer and the vinyl acetate. 25 parts by weight, acrylic acid 0.1 to 5 parts by weight, vinyl acetate 15 to 20 parts by weight to provide an adhesive composition characterized in that it is included.

In addition, the crosslinking agent is at least one selected from isocyanate, epoxy and melamine, and provides an adhesive composition, characterized in that used 0.1 to 1 parts by weight based on the total amount of the acrylic monomer.

In addition, the solvent provides a pressure-sensitive adhesive composition, characterized in that toluene.

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

The pressure-sensitive adhesive composition according to the present invention includes an acrylic monomer, a crosslinking agent, and a solvent, and further comprises 5 to 30 parts by weight of a hydrocarbon resin relative to the acrylic monomer. In particular, when the pressure-sensitive adhesive composition is coated on one side of the polyethylene terephthalate film with a thickness of 50 μm and then adhered to SUS to measure the adhesive strength, the adhesive strength is within 1.5 times within 2 hours compared to the initial adhesive strength, 18 After time is characterized in that more than twice.

The acrylic monomers may be used to select all of the acrylic monomers known in the art of the present invention, it is included in the present invention. For example, alkyl acrylates such as ethyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, and butyl methacrylate, 2-ethylhexyl meta Methacrylic acid alkyl esters such as methacrylate, cyclohexyl methacrylate, benzyl methacrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, glycidylamide, hydroxyethyl (meth) acrylate, 2- Acrylic monomers containing a functional group such as hydroxypropyl (meth) acrylate, N-methylol acrylamide and the like can be used alone or in combination.

However, the difference between the initial adhesive strength and the adhesive strength after a predetermined time varies depending on which one is selected as the acrylic monomer, however, the inventors have derived a desirable choice through easy effort. That is, more preferably, the acrylic monomer may be used by selecting 2-ethylhexyl acrylate, ethyl acrylate, acrylic acid.

It is also possible to add more vinyl acetate in addition to the acrylic monomers and be more effective. Although not limited, the preferred composition ratio is 55 to 65 parts by weight of 2-ethylhexyl acrylate, 15 to 25 parts by weight of ethyl acrylate, 0.1 to 5 parts by weight of acrylic acid, and vinyl acetate based on 100 parts by weight of the acrylic monomer and the vinyl acetate in total. It is good to include 15 to 20 parts by weight.

The crosslinking agent is added to be used in an additional crosslinked form to impart cohesive force of the pressure-sensitive adhesive, and is not particularly limited as a crosslinking agent, but isocyanate compound, epoxy compound, aziridine compound, metal chelate compound, metal alkoxide, Metal salts, amine compounds, hydrazine compounds may be used alone or in combination. More preferably, the crosslinking agent is selected from one or more of isocyanate, epoxy and melamine, and it is preferable to use 0.1 to 1 parts by weight based on the total amount of the acrylic monomers so as to significantly increase the late adhesive strength compared to the initial adhesive strength.

The solvent can be used to select a solvent used in the art, preferably a solvent which is inert to the reactants and products, does not adversely affect the reaction, ethyl acetate, and ethyl acetate or heptane, toluene and In isopropyl alcohol can be used alone or in combination, in particular, it is preferable to use toluene in order to significantly increase the late adhesion compared to the initial adhesion.

The hydrocarbon resin is added as an essential component for lowering the initial adhesive strength of the pressure-sensitive adhesive used in the present invention, increasing the late adhesive strength, the addition amount of the hydrocarbon resin is an important parameter for determining the adhesive properties, 5 ~ 30 compared to the acrylic monomer It is preferable to add a weight part. Although not limited, in particular 10 to 20% is good.

If the content is less than 5 parts by weight, the effect of lowering the adhesive strength is insignificant, and if it is used more than 30 parts by weight, the late adhesion is poor, and the increase in adhesive strength due to time and heat is insufficient to meet the object of the present invention.

The general definition of hydrocarbon resin is given in ISO 472 (but not limited to, all of which are referred to in the art as hydrocarbons are included in the present invention). That is, a product produced by polymerization from coal tar, petroleum, turpentine feedstock and the like. Petroleum distillates, resins and the like are preferred. Although the feedstocks can be used directly, it is also possible to use products derived from the above hydrodesulfurization process, i.e. feedstocks containing a reduced sulfur content, for example in the range up to 500 ppm, preferably up to 300 ppm.

The hydrocarbon resin may be a low molecular weight thermoplastic prepared through thermal or catalytic polymerization. This resin can be derived from several different monomer sources. Monomer sources include assorted petroleum distillates from oil refining, terpentin fractions (such as terpenes from natural product distillation), paper mill by-product streams, coultar and various pure olefinic monomers.

The hydrocarbon resin can range from a viscous liquid to a hard, brittle solid, depending on the monomers used and the specific reaction conditions, and the colors range from clear colors like water to pale yellow, tan or dark brown.

As an example of the said hydrocarbon resin, C9 monomer resin, C5 monomer resin, etc. are mentioned. In addition, the hydrocarbon may be composed of each or a combination of aliphatic and aromatic hydrocarbons.

Examples of the hydrocarbon resins also include pure monomeric hydrocarbon resins, such as Friedel, such as Lewis acids (e.g., boron trifluoride (BF3), complexes of boron trifluoride, aluminum trichloride (AlCl3), alkyl aluminum chloride) It can be prepared by cationic polymerization of styrene-based monomers such as styrene, alpha-methyl styrene, vinyl toluene and other alkyl substituted styrenes using a Friedel-Crafts polymerization catalyst.

Examples of such hydrocarbon resins also include aliphatic C5 hydrocarbon resins, which may be prepared by cationic polymerization of a fractionated petroleum feed containing C5 and C6 paraffins, olefins and diolefins, also referred to as "C5 monomers." have. These monomer streams, together with cyclopentene, pentene, 2-methyl-2-butene, 2-methyl-2-pentene, cyclopentadiene and dicyclopentadiene, are cationic polymerizable monomers such as 1,3-pentadiene as the main reactive component. Is made of. In addition to the reactive component, the nonpolymerizable component in the feed may include saturated hydrocarbons that may be co-distilled with unsaturated components such as pentane, cyclopentane or 2-methylpentane. This monomer feed may be copolymerized with C4 or C5 olefins or dimers as chain transfer agents.

As an example of the hydrocarbon resin, there may also be mentioned an aromatic C9 hydrocarbon resin, wherein the aromatic C9 hydrocarbon resin is derived from petroleum distillates produced from naphtha fractionation and aromatic C8, C9 and / or C10 unsaturated, referred to as "C9 monomer". It may be prepared by cationic polymerization of the monomer. These monomer streams consist of cationic polymerizable monomers such as styrene, alpha-methyl styrene, beta-methyl styrene, vinyl toluene, indene, dicyclopentadiene, divinylbenzene, and other alkyl substituted derivatives of these components. In addition to the reactive component, the non-polymerizable component can include aromatic hydrocarbons such as xylene, ethyl benzene, cumene, ethyl toluene, indane, methylindane, naphthalene and other similar compounds. These nonpolymerizable components of the feed stream can be incorporated into the resin via alkylation reactions.

Although the molecular weight of the hydrocarbon resin is not limited, the weight average molecular weight is preferably 500 to 3000, and the glass transition temperature is not limited but may be 35 to 150 degrees.

In this configuration, an initiator may be further added.

The pressure-sensitive adhesive using the acrylic monomer is polymerized using a suitable initiator capable of dissolving the monomer selected from the above group in an active organic solvent and thermally or photochemically activated. General initiators added to the pressure-sensitive adhesive may be used, but are not limited. Suitable thermal initiators include azo compounds such as 2,2'-azobis (isobutyronitrile), hydroperoxides such as t-butyl hydroperoxide and peroxides such as benzoin peroxide or cyclohexanone peroxide. Included. Suitable initiators for photochemically activation include benzophenone, benzoin ethyl ether and 2,2-dimethoxy-2-phenyl acetophenone.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, an Example is for illustrating this invention and is not limited only to these.

[ Example ]

Preparation of pressure-sensitive adhesive composition

After diluting 60% by weight of 2-ethylhexyl acrylate, 22 parts by weight of ethyl acrylate, 1 part by weight of acrylic acid, and 17 parts by weight of vinyl acetate with toluene, a hydrocarbon resin (trade name Regalrez 6180 Hydrocarbon Resin, manufactured by EASTMAN) was prepared. A pressure-sensitive adhesive composition was prepared by adding 15 parts by weight to 0.1 parts by weight of the crosslinking agent isocyanate, epoxy, and melamine, compared to the acrylic monomer.

Adhesive Strength Property Test

Adhesion strength over time was tested by measuring the peel strength using a tensile tester (Mecmesin).

In order to measure the adhesive strength, the pressure-sensitive adhesive composition of the embodiment was applied to one surface of a PET (polyethylene terephthalate) film with a thickness of 50 μm, and immediately after it was adhered to an SUS plate, a PI (polyimide), and a PE (polyethylene) substrate. The adhesive strength of and the adhesive strength over time were measured.

The results are shown in Table 1. As shown, it can be seen that the initial adhesion is considerably lower and the adhesion strength increases with time. In particular, when the adhesive strength was measured by sticking to SUS, the adhesive strength was less than 1 ~ 1.5 times within 1 hour after the adhesive in preparation for the adhesive strength of 20 minutes after the adhesive, and it is seen that more than 2 times after 24 hours after the adhesive Can be.

TABLE 1

Board time burglar    SUS Immediately 1211 20min 1230 1hr 1336 2hr 1459 4hr 1675 18hr 2992 24hr 3316 48hr 3328 PI 20min 674 24hr 1120 PE 20min 363 24hr 488

In the case of the pressure-sensitive adhesive composition according to the present invention, it is not only excellent in re-peelability when a defect occurs in a process such as lowering the initial adhesive strength and attaching the polarizing plate to the liquid crystal cell, but also once the adhesive is attached to the polarizing plate, the adhesive force increases over time, resulting in peeling. Provide an effect that does not occur.

Claims (6)

Including an acrylic monomer, a crosslinking agent, a solvent, As the pressure-sensitive adhesive composition, further comprising 5 to 30 parts by weight of the hydrocarbon resin relative to the acrylic monomer, When the pressure-sensitive adhesive composition is coated on one side of the polyethylene terephthalate film with a thickness of 50 μm, the pressure-sensitive adhesive strength is measured by sticking to SUS, and the adhesive strength is 1 to 1.5 times within 1 hour after the adhesion in comparison to the adhesive strength of 20 minutes after the adhesion. The pressure-sensitive adhesive composition, which is within 2 hours or more after 24 hours after adhesion. delete The pressure-sensitive adhesive composition of claim 1, further comprising vinyl acetate. The method of claim 3, wherein the acrylic monomer is 2-ethylhexyl acrylate, ethyl acrylate, acrylic acid, 55 to 65 parts by weight of 2-ethylhexyl acrylate, ethyl based on 100 parts by weight of the total acrylic monomer and the vinyl acetate Pressure-sensitive adhesive composition comprising 15 to 25 parts by weight of acrylate, 0.1 to 5 parts by weight of acrylic acid, and 15 to 20 parts by weight of vinyl acetate. According to claim 1, wherein the crosslinking agent is one or more selected from isocyanate, epoxy and melamine, pressure-sensitive adhesive composition, characterized in that used 0.1 to 1 parts by weight based on the total amount of the acrylic monomer. The pressure-sensitive adhesive composition according to claim 1, wherein the solvent is toluene.