TWI791843B - Adhesive sheet - Google Patents

Abstract

The object of the present invention is to provide an adhesive sheet for sticking polarizing plates, which has high antistatic performance and durability under harsh conditions, and suppresses uneven color and blanking on the display screen adhesive layer.

In the adhesive sheet for sticking polarizing plates of the present invention, the adhesive layer is composed of an adhesive composition containing an acrylic copolymer (A), a hardener, and an antistatic agent (C); (C) is Compounds containing fluorine or silicon (except for compounds represented by M ⁺ [(FSO ₂ ) ₂ N] ^- in which M is an alkali metal), and 3.5 or more parts relative to 100 parts of (A) and Add in an amount of less than 10 parts; (A) The monomer composition contains more than 15% and less than 50% of the monomer represented by the general formula (1), and contains monomers with reactive functional groups according to 0.01~5 parts; The surface resistance of the adhesive layer is 4.0×10 ⁹ Ω/□ or less.

Description

Adhesive sheet

The present invention relates to an adhesive sheet, which is used for pasting polarizing plates used in optical parts such as liquid crystal units of liquid crystal display devices, and is composed of a release film or release paper and an adhesive layer.

In recent years, since liquid crystal display devices have been reduced in weight and thickness, they are widely used as displays for vehicles, outdoor appliances, and personal computers, or as display devices for televisions, and their demand tends to increase. Accordingly, the use environments of liquid crystal display devices are also diversified, and it is necessary to cope with very severe conditions no matter indoors or outdoors. Here, the liquid crystal display device is attached to the outside of the glass substrate of the liquid crystal cell (the liquid crystal component aligned in a predetermined direction is sandwiched between two glass substrates) through an adhesive layer formed of an optical adhesive composition. A polarizing plate or a laminate of a polarizing plate and a retardation plate (hereinbelow these integrations are referred to as “polarizing plate”).

The above-mentioned polarizing plate generally has a three-layer structure in which both sides of a polarizing plate made of polyvinyl alcohol-based materials are sandwiched by a triacetyl cellulose-based protective film. However, the characteristics of these materials lack dimensional stability. . Also, since the polarizing plate is formed by stretching, it is easy to expand and contract due to heat and humidity. Therefore, in the liquid crystal display device, if the adhesive layer used in the lamination cannot absorb and relax the internal stress generated by the expansion and contraction of the polarizer, the distribution of the residual stress acting on the polarizer will become uneven. Then, if the stress is especially concentrated on the peripheral part, the peripheral part of the display part of the liquid crystal display device will become brighter or darker than the center as a result, and color unevenness and blanking will occur on the liquid crystal display surface.

Also, regarding the adhesive layer that constitutes the polarizing plate, in addition to the above-mentioned technical issues, it is also necessary to peel off the release film or release paper attached to the adhesive surface when pasting, but static electricity is generated during peeling, which has a negative impact on the product. Issues affecting functional materials laminated via an adhesive layer. Specifically, for example, if static electricity is generated when the release film is peeled off from the adhesive layer provided on the polarizing plate, the static electricity will affect the liquid crystal layer inside the liquid crystal cell and cause problems. In addition, in a liquid crystal display device with a touch sensor, it will cause adverse effects such as incorrect operation of the capacitive sensor. There is a method of providing antistatic properties to an adhesive layer as a means for suppressing static electricity generation when peeling off a release film. On the other hand, as described below, in recent years, the required level of antistatic performance has been significantly increased compared with conventional ones.

In order to improve the antistatic performance, an antistatic agent must be added. However, if the amount added is too large, the cohesive force of the adhesive will decrease, and especially under severe durability conditions, peeling or foaming of the adhesive layer will tend to occur. Therefore, it is very difficult to make the formed adhesive layer have satisfactory durability even under severe durability conditions (hereinafter referred to as "durability under severe conditions"), and it is possible to suppress the wear and tear of the display surface of the display device. Uneven color and white space occur, and it is difficult to make it exhibit superior antistatic performance when peeling off the above-mentioned release film. Such an adhesive layer has not been realized so far.

In particular, liquid crystal display devices have been used in a wide range of fields in recent years. Therefore, in vehicle applications such as car navigation, the temperature inside the car, which becomes a closed space, becomes extremely high, and the use environment is also diverse. Durability under tougher conditions of the past. Therefore, there is a problem that the durability of adhesives used in conventional liquid crystal display devices such as TVs mounted at room temperature is insufficient.

Various proposals have been made so far regarding adhesives used in liquid crystal display devices having these problems. For example, Patent Document 1 proposes an adhesive composition, which contains: an unsaturated monomer containing (meth)acrylate and an aromatic ring (2-phenoxyethyl acrylate) and an unsaturated monounsaturated monomer with a polar functional group. A copolymer obtained from a mixture of monomers; an ionic compound (antistatic agent) that is solid at room temperature; and a crosslinking agent. In addition, Patent Document 2 proposes an adhesive composition comprising: a (meth)acrylic polymer comprising an alkyl (meth)acrylate and an aromatic ring-containing alkyl (meth)acrylate as monomer units. substance (A); and alkali metal salt (B). Furthermore, Patent Document 3 proposes an adhesive composition containing an alicyclic structure-containing monomer (a1), an aromatic ring-containing monomer (a2), and an oxyalkylene-containing monomer (a3) A (meth)acrylate copolymer (A) as a monomer unit constituting the polymer; and a crosslinking agent (B).

Furthermore, as an antistatic agent, an adhesive composition using a specific alkali metal salt represented by M ⁺ [(FSO ₂ ) _{2 N} ] ^- such as KN(FSO ₂ ) 2 as an antistatic agent has been proposed. In the examples, it is described that the surface resistance value of the adhesive sheet using the adhesive composition is 4.0×10 ⁹ Ω/□ or less.

[Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2010-066755

[Patent Document 2] Japanese Patent Laid-Open No. 2016-028287

[Patent Document 3] Japanese Patent Laid-Open No. 2017-134134

[Patent Document 4] Korean Laid-Open Patent No. 10-2010-0018414

However, according to the examination of the inventors of the present application, the adhesive composition proposed in Patent Document 1 cannot form an adhesive layer sufficient to realize the durability under the above-mentioned severe conditions required in recent years, and to impart a high level of safety. Both antistatic properties. Also, although the adhesive composition proposed in Patent Document 2 and the adhesive composition proposed in Patent Document 3 both obtain an adhesive layer with excellent antistatic performance, they do not meet the requirements of the severe applications placed in recent years. "Durability under severe conditions" required by the environment. Although the surface resistance value of the adhesive sheet formed by the adhesive composition described in Patent Document 4 is below 4.0×10 ⁹ Ω/□, its durability effect is still limited at 60°C and 90% relative humidity. After 300 hours of standing in the furnace, the peeling phenomenon, the generation of air bubbles, and the observation of light leakage have not yet achieved the more stringent durability that meets the problem of the present invention.

Therefore, the object of the present invention is to provide an adhesive sheet, which can be used to form an adhesive layer of a polarizing plate that is widely used in a wide range of fields, has a superior antistatic performance that has not been realized so far, and has severe conditions. Lower durability, and can suppress the color unevenness and blanking phenomenon that occur on the display screen. In particular, the present invention aims to provide an adhesive composition for forming an adhesive layer of the above-mentioned useful adhesive sheet.

The above objects are achieved by the present invention described below. That is, the present invention provides the following inventions regarding the adhesive sheet.

[1] An adhesive sheet, which is an adhesive sheet for attaching a polarizing plate with a release film or release paper and an adhesive layer, characterized in that the adhesive layer contains at least acrylic copolymer An adhesive composition composed of a combination (A), a hardener (B), and an antistatic agent (C); the antistatic agent (C) is a compound containing either fluorine or silicon in its structure (wherein, Except for the case of containing a compound represented by M ⁺ [(FSO ₂ ) ₂ N] ^- in which M is an alkali metal), and relative to 100 parts by mass of the above-mentioned acrylic copolymer (A), it is not less than 3.5 parts by mass and less than Add in the range of 10 parts by mass; the monomer composition of the acrylic copolymer (A) is at least 50% by mass and less than 85% by mass of the ethylenically unsaturated monomer (a1) without a reactive functional group. 1 kind, and containing at least 1 kind of monomer (a2) represented by the following general formula (1) of more than 15% by mass and less than 50% by mass; and, relative to the above-mentioned monomer (a1) and the above-mentioned monomer ( The total of 100 parts by mass of a2) is obtained by copolymerizing 0.01 to 5 parts by mass of a monomer containing at least one type of ethylenically unsaturated monomer (a3) having a reactive functional group; the above-mentioned adhesive The surface resistance of the agent layer is below 4.0×10 ⁹ Ω/□;

(In the general formula (1), ^R1 represents a hydrogen atom or a methyl group, ^R2 represents any one of a hydrogen atom, an alkyl group, an aralkyl group or an aryl group, and n represents any integer of 2 to 9.)

As a preferable aspect of this invention, the following are mentioned, for example.

[2] The adhesive sheet according to [1], wherein the reactive functional group of the above-mentioned ethylenically unsaturated monomer (a3) having a reactive functional group is selected from hydroxyl, carboxyl, glycidyl, and nitrogen-containing At least any one of the groups formed by the base.

[3] The adhesive sheet according to [1] or [2], wherein the curing agent (B) contains an isocyanate compound and is used in an amount of It exists in the range of 0.01 mass part or more and 10 mass parts or less.

[4] The adhesive sheet according to any one of [1] to [3], wherein the adhesive composition further contains a silane coupling agent (D).

According to the present invention, an adhesive sheet is provided, which is an adhesive sheet for sticking a polarizing plate having a release film or release paper (hereinafter referred to as "release film, etc.") and an adhesive layer. Forms an adhesive layer that has superior antistatic properties that have not been realized so far, and shows durability under harsh conditions. When used in image display parts, it can suppress the occurrence of uneven color and white space. Also, according to the present invention, an adhesive composition is provided, which can be used to form the above-mentioned adhesive layer with superior performance, and can form a combination of superior antistatic performance and durability under severe conditions that have not been realized so far. adhesive layer.

Next, the preferred forms for implementing the present invention will be enumerated, and the present invention will be described in more detail. Also, the term "(meth)acrylic acid" in the claims of the present invention and the description means both "acrylic acid" and "methacrylic acid"; and the term "(meth)acrylate" means Refers to both "acrylate" and "methacrylate".

The adhesive sheet of the present invention is used for affixing polarizing plates to optical parts such as liquid crystal units of liquid crystal display devices. The adhesive layer constituting the adhesive sheet is composed of at least acrylic copolymer (A), hardener (B) and an antistatic agent (C) as constituents, and an adhesive composition containing a silane coupling agent (D) if necessary. Furthermore, the adhesive sheet of the present invention is composed of monomers of the acrylic copolymer (A) contained in the adhesive composition for forming the adhesive layer, and the monomer represented by the above general formula (1) is contained in a specific range. In the case of the specified unique monomer (a2), the adhesive layer formed from the adhesive composition exhibits a surface resistance value of less than 5.0×10 ⁹ Ω/□, and further 4.0×10 ⁹ Ω/□, which has not been achieved so far. Superior antistatic performance (hereinafter referred to as "superior antistatic performance"), and shows durability under harsh conditions, achieving superior performance that cannot be achieved by conventional technologies. These components constituting the present invention will be described respectively below.

[Acrylic copolymer (A)]

The monomer composition of the acrylic copolymer (A) is composed of at least one type of ethylenically unsaturated monomer (a1) having no reactive functional group in an amount of 50 mass % or more and less than 85 mass %, and contains the following general formula: (1) A copolymer of at least one monomer (a2) having a composition within a range of more than 15% by mass and 50% by mass or less. Furthermore, it contains the ethylenic non-reactive functional group in the range of 0.01 mass part or more and 5 mass parts or more with respect to 100 mass parts of monomer (a1) and monomer (a2) total. An acrylic copolymer obtained by copolymerizing at least one monomer composition of a saturated monomer (a3).

(In the general formula (1), ^R1 represents a hydrogen atom or a methyl group, ^R2 represents any one of a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group, and n represents any integer of 2 to 9.)

(monomer (a1))

Ethylenically unsaturated monomer (a1) without reactive functional group (hereinafter also referred to as "component (a1)") is a component of monomer (a1) and monomer (a2) of acrylic copolymer (A). In the monomer composition, it is used at a ratio of 50% by mass or more and less than 85% by mass. If the proportion of the component (a1) is less than 50% by mass, when the adhesive layer is formed, the adhesiveness to the base material or the flexibility of the adhesive layer will decrease, peeling or floating from the base material will occur, and it will not be possible to obtain full durability. On the other hand, when the proportion of the component (a1) is 85% by mass or more, the adhesiveness to the substrate is insufficient, and foaming of the adhesive layer occurs under severe durability conditions. In addition, the antistatic performance is also insufficient.

As (a1) component, the (meth)acrylate monomer of carbon number 1-18 is mentioned, for example. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, (meth)acrylic acid Alkyl (meth)acrylates such as 2-ethylhexyl, octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and lauryl (meth)acrylate. These can be used individually by 1 type or in combination of 2 or more types.

(monomer (a2))

The acrylic copolymer (A) is based on the monomer composition of the monomer (a1) and the monomer (a2), and contains the monomer (a2) represented by the following general formula (1) (hereinafter also abbreviated as "( a2) Component ") synthesized at a ratio of more than 15% by mass and 50% by mass or less. By containing the component (a2) in the above monomer composition within the above range, in the adhesive layer formed by using the antistatic agent (C) described later, it is possible to take into account the durability under severe conditions that cannot be achieved by the conventional technology Sexuality and superior antistatic properties. That is, if the component (a2) is outside the above range, it will be difficult for the formed adhesive layer to achieve both excellent antistatic performance and durability under severe conditions.

(In the general formula (1), ^R1 represents a hydrogen atom or a methyl group, ^R2 represents any one of a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group, and n represents any integer of 2 to 9.)

Specific examples of the component (a2) include phenoxydiethylene glycol acrylic acid, phenoxy triethylene glycol acrylic acid, and nonylphenoxy polyethylene glycol acrylate. These can be used individually by 1 type or in combination of 2 or more types.

(monomer (a3))

The monomer composition of the synthetic acrylic copolymer (A) is 0.01 parts by mass or more based on 100 parts by mass of the total of the components (a1) and (a2) in addition to the above-mentioned components (a1) and (a2) And it is comprised by adding the ethylenically unsaturated monomer (a3) (it abbreviates to "(a3) component" hereafter) which has a reactive functional group in the quantity of 5 mass parts or less. More preferably, it is 0.01 mass part or more and 3 mass parts or less. The film-forming resin constituting the adhesive composition of the present invention can form an adhesive layer more excellent in durability by containing the component (a3) that reacts with the hardener within the above range. The reactive functional group may, for example, be a hydroxyl group, a glycidyl group or an amide group, among which an ethylenically unsaturated monomer having a carboxyl group is preferably used. In the monomer composition of the acrylic copolymer (A), if the component (a3) is less than the above-mentioned range with respect to the total of 100 parts by mass of the component (a1) and the component (a2), the cohesive force of the adhesive layer will decrease. Under the severe durability condition which is the subject of the present invention, foaming of the adhesive layer occurs; if it exceeds the above range, the adhesiveness of the adhesive layer to the substrate will be damaged, and peeling may occur.

Component (a3) includes, for example, hydroxyl-containing (meth)acrylate monomers such as hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, (meth)acrylic acid, (meth) Carboxyl-containing monomers such as β-carboxyethyl acrylate, glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, etc., glycidyl-containing monomers, (meth) Amide-based monomers such as acrylamide and dimethylaminopropyl (meth)acrylamide. These can be used individually by 1 type or in combination of 2 or more types.

(physical properties)

The acrylic copolymer (A) containing the above components (a1) to (a3) in the monomer composition preferably has a weight average molecular weight (measured by GPC, converted to standard polyethylene) of not less than 1 million and not more than 2.5 million. A more preferable weight average molecular weight is in the range of 1.2 million to 2.2 million. If the weight average molecular weight is less than 1 million, when the adhesive composition is used as an adhesive layer of a polarizing plate, the durability of the adhesive layer tends to be insufficient. On the other hand, when the weight average molecular weight exceeds 2,500,000, the viscosity of the acrylic copolymer becomes very high, and the applicability also deteriorates, which is not preferable.

The acrylic copolymer (A) satisfying the above conditions can usually be produced by solution polymerization, block polymerization, emulsion polymerization or suspension polymerization. Particularly preferred is the production of the acrylic copolymer (A) by solution polymerization obtained as a solution. That is, by obtaining the acrylic copolymer (A) as a solution, it can be used for manufacture of the adhesive composition of this embodiment as it is. Examples of the solvent used in this solution polymerization include organic solvents such as ethyl acetate, toluene, n-hexane, acetone, and methyl ethyl ketone.

(polymerization initiator)

As the polymerization initiator used when copolymerizing the above-mentioned monomers containing the components (a1) to (a3), conventionally known ones can be used. For example, peroxides such as benzoyl peroxide and lauryl peroxide; azobis compounds such as azobisisobutyronitrile and azobisvaleronitrile; polymer azo polymerization initiators, etc.; or in combination. Moreover, in order to adjust the molecular weight of the synthesized acrylic copolymer (A), a well-known chain transfer agent can also be used suitably.

[hardening agent (B)]

系化合物及三聚氰胺系化合物。此時此等之使用量係相對於上述丙烯酸系共聚合體(A)100質量份，較佳為0.1質量份以上且15質量份以下之範圍內，更佳係0.1~10質量份之範圍內。本發明所使用之構成黏著劑組成物的硬化劑(B)之使用量，係配合屬於上述丙烯酸系共聚合體(A)之原料之具反應性官能基之乙烯性不飽和單體(a3)的調配量或種類而適當決定即可。使用量若少於上述範圍，則黏著劑層之凝集力降低，在本發明課題之嚴苛耐久性條件下，有發生黏著劑層之發泡之虞；另一方面，若超過上述範圍，則黏著劑組成物之凝集力變得過多，有成為所貼黏之偏光板之剝離原因之虞，故不佳。 The curing agent (B) constituting the adhesive composition used in the present invention contains an isocyanate-based compound, and its usage is preferably 0.01 parts by mass or more based on 100 parts by mass of the above-mentioned acrylic copolymer (A). Within the range of 10 parts by mass or less, more preferably within the range of 0.01 to 4.00 parts by mass. In the present invention, conventionally known curing agents listed below may be used in combination with the above as needed. For example, metal chimeras, epoxy compounds, acridine

Compounds and melamine compounds. At this time, the usage-amount thereof is preferably in the range of 0.1 to 15 parts by mass, more preferably in the range of 0.1 to 10 parts by mass, based on 100 parts by mass of the above-mentioned acrylic copolymer (A). The usage amount of the curing agent (B) constituting the adhesive composition used in the present invention is the ratio of the ethylenically unsaturated monomer (a3) with reactive functional groups which is the raw material of the above-mentioned acrylic copolymer (A). What is necessary is just to decide suitably according to the compounding quantity or kind. If the amount used is less than the above range, the cohesive force of the adhesive layer will decrease, and there is a possibility of foaming of the adhesive layer under the severe durability conditions of the subject of the present invention; on the other hand, if it exceeds the above range, then The cohesive force of the adhesive composition becomes excessive, which may cause peeling of the attached polarizing plate, so it is not preferable.

The isocyanate-based compound is preferably a polyisocyanate compound having two or more isocyanate groups in one molecule, such as hexamethylene diisocyanate, imyl diisocyanate, cresyl diisocyanate, isophor Adducts of ketone diisocyanate, etc., and trimethylolpropane, etc., trimeric isocyanate compounds, biuret-type compounds, etc. Preferable compounds are cresyl diisocyanate and imyl diisocyanate, which can be used alone or in combination.

系化合物、三聚氰胺系化合物。 Specific examples of the curing agent that can be used in combination with the above-mentioned isocyanate-based compound and can be used if necessary include the following. Examples of metal complexes include aluminum complexes, zirconium complexes, titanium complexes, and the like. Examples of the epoxy compound include bisphenol-type compounds, aliphatic glycidyl ether compounds, biphenyl-type compounds, and epoxy-based resins having two or more epoxy groups in the molecule. Also, other crosslinking agents such as acridine can also be used

series compounds, melamine series compounds.

[Antistatic agent (C)]

The adhesive layer constituting the adhesive sheet of the present invention is composed of an adhesive composition containing an antistatic agent (C) as a constituent together with the above-mentioned acrylic copolymer (A) and curing agent (B). By containing the antistatic agent (C) in the adhesive composition, the formed adhesive layer exhibits durability under harsh conditions, and at the same time shows that its surface resistance value is less than 5.0×10 ⁹ Ω/□, and further 4.0× 10 ⁹ Ω/□ or below the superior antistatic performance that cannot be achieved by the conventional technology.

The antistatic agent (C) is not particularly limited, and conventionally known ones can be used. Among them, a compound containing either fluorine or silicon is preferable in its structure (alkali metal salt is not included). Examples of the alkali metal salt include compounds represented by M ⁺ [(FSO ₂ ) ₂ N] ^- such as KN(FSO ₂ ) ₂ . Specific examples include ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide, ethylmethylimidazolium bis(fluorosulfonyl)imide, 4-methyl-1-octylpyridine Onium bis(trifluoromethanesulfonyl)imide, 4-methyl-1-octylpyridinium bis(fluorosulfonyl)imide, tributylmethylammonium bis(trifluoromethanesulfonyl)imide Imine, tributylbenzyl ammonium bis(fluorosulfonyl)imide, lauryltrimethylammonium bis(fluorosulfonyl)imide, 1-octyl-4-methylpyridinium hexafluoro Phosphate etc.

The amount of the above-mentioned antistatic agent (C) is preferably added in a range of more than 0.01 parts by mass and less than 10 parts by mass relative to 100 parts by mass of the acrylic copolymer (A) with a specific composition specified in the present invention. More preferably, the usage amount of the antistatic agent (C) is 0.1-8 parts by mass. By setting the amount of the antistatic agent (C) within the above-mentioned range, an adhesive sheet having an adhesive layer having excellent antistatic performance and durability under severe conditions can be obtained. If it is less than the above range, the desired superior antistatic performance cannot be imparted; if it is more than the above range, the cohesive force of the formed adhesive layer will decrease, which may affect durability, which is not preferable.

[other ingredients]

The adhesive composition constituting the adhesive sheet of the present invention may further contain a silane coupling agent (D). As the silane coupling agent (D) to be used, any of known silane coupling agents in the field of adhesives can be used. The usage-amount of a silane coupling agent (D) is preferably in the range of 0.01-5 mass parts with respect to 100 mass parts of acrylic-type copolymers (A).

The adhesive composition constituting the adhesive sheet of the present invention may further contain various additives within the range not impairing the effect of the present invention in accordance with the purpose of adjusting the adhesive force and other required properties. For example, it may contain terpene-based, terpene-phenol-based, lavone-indene-based, styrene-based, rosin-based, xylene-based, phenol-based, or petroleum-based adhesive-imparting resins, antioxidants, ultraviolet absorbers, and fillers , pigments, etc.

[Surface resistance value of the adhesive layer of the adhesive sheet]

The adhesive sheet of the present invention is characterized in that the surface resistance value of the adhesive layer formed by the adhesive composition having the above-mentioned constitution is less than 5.0×10 ⁹ Ω/□, further 4.0×10 ⁹ Ω/□ or less Unprecedented low value of . It is preferably below 2.0×10 ⁹ Ω/□. When forming an adhesive layer with a conventional adhesive composition, it is necessary to use a large amount of antistatic agent in order to make the surface resistance less than 5.0×10 ⁹ Ω/□. On the other hand, if the antistatic agent increases, the cohesive force will decrease, so there is a problem of deterioration in durability under severe environmental conditions such as high temperature (105°C or 115°C) or high temperature and high humidity. On the other hand, the adhesive layer constituting the adhesive sheet of the present invention is composed of the component (a2) specified by the general formula (1) as the monomer of the acrylic copolymer (A) in a specific ratio, and even in Under the above-mentioned severe durability conditions, no peeling or foaming will occur, and the influence of static electricity on polarizing films can be reduced, and the surface resistance value can be less than 5.0×10 ⁹ Ω/□, and further 4.0×10 ⁹ Ω / □ Amazing effects below.

The surface resistance value specified in the present invention is a value measured using a high resistance meter (trade name: Hiresta-UX MCP-HT450) manufactured by Mitsubishi Chemical Analytech. Specifically, an evaluation sample is made by forming an adhesive layer with a thickness of 20 μm on the release film, cut into a size for measurement, peeled off the release film, and placed in a constant temperature of 23±2°C and humidity of 50±5%RH. Humid chamber, the value measured using a high resistance meter.

[polarizer]

The adhesive sheet of the present invention having the adhesive layer formed by the above adhesive composition is used for adhering polarizing plates. The form of the adhesive sheet of the present invention is not particularly limited as long as it has a release film or the like and an adhesive layer. Generally, it is the state before forming an adhesive layer on a release film, etc., and sticking to a polarizing plate. One of the remarkable effects of the present invention can be obtained under the following conditions: from the state where one of the adhesive layers of the above-mentioned adhesive layer is laminated on the polarizing plate, and a release film or the like is layered on the other adhesive surface, the release film, etc. It peels off and sticks to the outer surface of a glass substrate, for example, and uses it. That is, the adhesive sheet of the present invention has excellent antistatic performance, so under the above conditions, the amount of static electricity generated when the release film is peeled off from the adhesive layer can be suppressed. As a result, adverse effects on liquid crystal display devices caused by static electricity generation can be reduced.

Furthermore, in addition to the above-mentioned effects, the adhesive sheet of the present invention can also achieve remarkable effects that cannot be achieved by conventional technologies that are superior in durability under harsher environmental conditions. Specifically, even under severe environments of high temperature (105°C or 115°C) or high temperature and high humidity, there will be no peeling of the polarizer from the glass substrate, etc., or foaming of the adhesive layer, which can realize Durability under harsh conditions. Furthermore, it is also possible to suppress the occurrence of blanking on the image display screen, which tends to occur when a liquid crystal display device is used in a harsh environment. The polarizing plate to which the adhesive sheet of the present invention can be used is not particularly limited, and it can be used for pasting conventionally known polarizing plates. Specific examples include general polarizers (using untreated TAC films), polarizers coated with discotic liquid crystals, or uncoated polarizers, or stretched films such as stretched triacetyl cellulose Film, stretched polycycloolefin-based film, or stretched cellulose acetate propionate film is used as a polarizing plate and the like as a base material.

The adhesive sheet of this invention which formed the adhesive layer on a release film etc. can be manufactured by the following procedure. Using a commonly used coating device, such as a roll coater, first, to a release film such as polyethylene terephthalate film (PET film) coated with a release agent such as silicone resin on the surface, The adhesive composition specified in the present invention is applied and dried to form an adhesive layer, thereby facilitating production. Then, the polarizing plate can be bonded immediately to the adhesive layer on the side without the release film, or it can be stored with the release film on both sides of the adhesive layer, and the release film can be peeled off and bonded to polarizer. Also, in any of the above cases, depending on the constituent materials of the adhesive composition, the adhesive layer can be formed by thermal crosslinking or photocuring by ultraviolet light or the like, if necessary.

The adhesive layer constituting the adhesive sheet of the present invention can be formed by the methods listed above using the adhesive composition specified in the present invention. The coating amount of these adhesive compositions is preferably such that the thickness of the adhesive layer after drying becomes about 10 to 50 μm. More preferably, the thickness of the adhesive layer after drying is about 10 to 25 μm. By setting the thickness of the adhesive layer within the above range, it becomes possible to obtain an adhesive sheet with a better balance between durability and antistatic properties. Moreover, as mentioned above, by using the above adhesive sheet of the present invention, for example, a polarizing plate is pasted on the glass substrate of a liquid crystal display device by the usual means, and the remarkable effect of the present invention can be obtained.

[Example]

Next, the present invention will be described more specifically with reference to production examples, examples, and comparative examples. Also, "parts" and "%" in the text are quality standards.

[manufacturing example 1] (Manufacture of Acrylic Copolymer)

In a reaction device equipped with a stirrer, a thermometer, a reflux cooler, and a nitrogen introduction pipe, after enclosing nitrogen gas, 140 parts of ethyl acetate, which is a reaction solvent, is filled with 80 parts of butyl acrylate (BA) as a component (a1), as 20 parts of phenoxydiethylene glycol acrylate (manufactured by Kyoei Corporation, trade name "LIGHT ACRYLATE P2HA") as component (a2), 2 parts of hydroxyethyl acrylate (HEA) as component (a3), and polymerized 0.05 parts of azobisisobutyronitrile as the starter. Stirring this, it was made to react at 55 degreeC in nitrogen stream for 7 hours. After the reaction, it was diluted with ethyl acetate to obtain an acrylic acid copolymer composition solution A1 with a solid content of 15.0% and a weight average molecular weight of 2 million.

[Manufacturing example 2~18]

Except using the (a1)～(a3) components used in Manufacturing Example 1 respectively according to the type and amount recorded in Table 1 (Table 1-1, Table 1-2), all the other are carried out in the same manner as Manufacturing Example 1 to obtain the results obtained in the examples. The acrylic acid copolymer composition solutions A2-A11 used, and the acrylic acid copolymer composition solutions B1-B7 used in the comparative example.

The abbreviations in Table 1 are as follows.

‧BA: Butyl Acrylate

‧MA: methyl acrylate

‧P2HA: Phenoxydiethylene glycol acrylate: manufactured by Kyoeisha, trade name "LIGHT ACRYLATE P2HA"

‧P-300A: Phenoxytriethylene glycol acrylate: manufactured by Kyoeisha, trade name "LIGHT ACRYLATE P-300A"

‧FA-314A: Nonylphenoxy polyethylene glycol acrylate: manufactured by Hitachi Chemical Co., Ltd., trade name "FA-314A"

‧FA-318A: Nonylphenoxy polyethylene glycol acrylate: manufactured by Hitachi Chemical Co., Ltd., trade name "FA-318A"

‧PHEA: Phenoxyethyl Acrylate: manufactured by Kyoeisha, trade name "LIGHT ACRYLATE PO-A"

‧EC-A: Epoxy triethylene glycol acrylate: manufactured by Kyoeisha, trade name "LIGHT ACRYLATE EC-A"

‧FA-400M: Methoxypolyethylene glycol #400 methacrylate: manufactured by Hitachi Chemical Co., Ltd., trade name "FA-400M(100)"

‧HEA: Hydroxyethyl Acrylate

‧4HBA: 4-Hydroxybutyl Acrylate

‧AAC: Acrylic acid

‧β-CEA: β-carboxyethyl acrylate

‧GA: glycidyl acrylate

‧GMA: Glycidyl methacrylate

‧4HBAGE: 4-Hydroxybutyl Acrylate Glycidyl Ether

‧AM: Acrylamide

‧MAM: Methacrylamide

‧DMAPAA: Dimethylaminopropyl Acrylamide

[Example 1] (manufacture of adhesive composition)

With respect to 100 parts of solid content of the acrylic copolymer composition solution A1 obtained above, CORONATE L (trade name, trimethylolpropane adduct of TDI manufactured by Nippon Polyurethane Co., Ltd., solid content concentration 75 %) 0.50 parts based on solid content, 5.0 parts of ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide as an antistatic agent, X-41-1810 (trade name, Shin-Etsu) as a silane coupling agent Chemical Co., Ltd.) 0.8 parts were mixed well to obtain an adhesive composition 1.

(Manufacture of Adhesive Sheet 1)

The adhesive composition 1 obtained above was coated on a PET film which is a silicone resin-coated release film, and then dried at 90° C. to remove the solvent to form an adhesive layer with a dry thickness of 20 μm. After laminating the surface forming the adhesive layer to one side of the polarizing film, it was aged at 23°C and 50% RH for 7 days to obtain an adhesive sheet 1 with a release film and an adhesive layer. Optical components as constituent elements.

[Examples 2-20, Comparative Examples 1-9]

In addition to replacing the acrylic acid copolymer composition solution A1 used in Example 1, use the acrylic acid copolymer composition used in the example according to the type and amount recorded in Table 2 (Table 2-1, Table 2-2, Table 2-3) Except for the acrylic acid copolymer composition solutions A1~A11 and the acrylic acid copolymer composition solutions B1~B7 used in the comparative example, the rest were carried out in the same manner as in Example 1 to obtain the adhesive compositions 2~20 used in the examples and the adhesive composition used in the comparative example. Objects 21~29. Then, except for using adhesive compositions 2-29, proceed in the same manner as in Example 1 to obtain adhesive sheets 2-20 of Examples 2-20 and adhesive sheets 21-29 of Comparative Examples 1-19, respectively. .

<Evaluation method> 1. Production of polarizing plates for evaluation samples (adhered body: polarizing film)

Using the respective adhesive compositions produced in Examples and Comparative Examples, an adhesive layer was formed on a polarizing plate by the following method, and a polarizing plate with an adhesive layer, which is a sample for evaluation, was produced. That is, after coating adhesive compositions 1 to 29 on a PET film (release substrate) which is a silicone resin-coated release film, the solvent is removed by drying at 90°C to form a thick 20μm adhesive layer. A polarizing film with a thickness of 110 μm was bonded to the surface on which the adhesive layer was formed, and then aged for 7 days at 23°C and 50% RH to prepare samples for evaluation. The size of the sample for evaluation was set to 80mm×150mm, and the above-mentioned polarizing film used a TAC polarizing plate. Then, using the sample for evaluation of the laminated adhesive layer, release film, and polarizing film produced as described above, each test described later was performed, and evaluation was performed according to each evaluation standard. Then, the results are shown in Table 3. Table 3-1 and Table 3-2 show the results of the evaluation samples of the examples, and Table 3-3 shows the results of the evaluation samples of the comparative examples.

2. Durability (1) Durability at 105°C

Using each sample for evaluation, peel off the release film to expose the adhesive layer, attach it to glass, and leave it in an environment of 105°C (DRY) for 500 hours. After standing, visually observe (a 10x magnifying glass can be used; the same applies below) and confirm the foaming and peeling that occurred in the adhesive layer, and evaluate according to the following criteria, and the evaluation results are shown in Table 3.

(2) Durability at 115°C

Using each sample for evaluation, peel off the release film to expose the adhesive layer, stick it on glass, and leave it in an environment of 115°C (DRY) for 500 hours. After being left to stand, foaming and peeling of the adhesive layer were visually observed and confirmed, and evaluated according to the following criteria, and the evaluation results are shown in Table 3.

(3) Durability at 65°C, 95%RH

After attaching the sample for evaluation to glass, and leaving it in a high-temperature and high-humidity environment at 65°C and 95%RH for 500 hours, visually observe and confirm foaming and peeling, and evaluate according to the following criteria, which are shown in Table 3 Evaluation results.

(evaluation criteria) 1) About foaming

◯: Foaming was not confirmed in the polarizing plate.

△: Although foaming was slightly observed in the polarizing plate, it was practically no problem.

×: Foaming was confirmed in the polarizing plate.

2) Regarding stripping

◯: Peeling was not confirmed in the polarizing plate.

△: Although slight peeling was observed on the polarizing plate, it was at a level where there was no practical problem.

×: Remarkable peeling was confirmed on the polarizing plate.

3. Adhesiveness

The adhesive layer of the evaluation sample was wiped 10 times with fingers, and the adhesiveness was evaluated by the number of times until the polarizing film (TAC polarizing plate) fell off. Also, when peeling occurred 1 to 9 times, the number of times was described, and when peeling did not occur even after wiping 10 times, it was described as ">10".

4. Surface resistance value

Peel off the separator of the sample for evaluation to expose the adhesive layer, and use a high resistance meter (trade name: Hiresta-UX) manufactured by Mitsubishi Chemical Analytech under room temperature conditions of temperature 23±2°C and humidity 50±5%RH MCP-HT450) and measuring electrodes to measure the surface resistance value (Ω/□) of the adhesive layer.

5. Leave blank

After attaching the sample for evaluation to glass, leave it for 500 hours in a high-temperature and high-humidity environment at 65°C 95%RH (also, it can also be the latter in a durability test at 65°C 95%RH) The top and bottom of the liquid crystal panel are bonded together as crossed polarizers. Light up the backlight of the LCD screen, observe the state of the blank space visually, and evaluate according to the following criteria.

[evaluation criteria]

◯: Blank space is not observed in the polarizing plate.

Δ: Slight white space is observed on the polarizing plate.

×: Blank space was observed on the polarizing plate.

6. Overall evaluation

The overall evaluation was performed based on the following criteria.

[evaluation criteria]

A: The evaluation of durability is ○ under all environmental conditions, the evaluation of tightness is ≧8, the surface resistance value of the adhesive layer is 4.0×10 ⁹ Ω/□ or less, and the evaluation of blank space is ○ Condition.

B: The evaluation of durability is based on any one of the environmental conditions. Slight foaming and/or peeling were confirmed on the polarizing plate. The evaluation of tight adhesion was ≧8, and the surface resistance value of the adhesive layer was 4.0×10 ⁹ Ω/□ or less, and the evaluation of blank space is ○.

C: The evaluation of durability is based on any one of the environmental conditions. Slight foaming and/or peeling were confirmed on the polarizing plate. The evaluation of tight adhesion was ≧8, and the surface resistance value of the adhesive layer exceeded 4.0×10 ⁹ Ω/□ and less than 5.0×10 ⁹ Ω/□, and the evaluation of blank space was ○.

D: The evaluation of durability refers to the confirmation of foaming and/or peeling on the polarizing plate in any one of the environmental conditions, the evaluation of tightness is <8 and ≧6, and the surface resistance value of the adhesive layer is less than 5.0 ×10 ⁹ Ω/□, and the evaluation of blank space is △ or ×.

E: The evaluation of durability is based on the confirmation of foaming and/or peeling on the polarizing plate in any one of the environmental conditions, the evaluation of the tightness is <6, and the surface resistance value of the adhesive layer is 5.0×10 ⁹ Ω /□The above situation.

As shown in Table 3-1 and Table 3-2, the adhesive layer formed by the adhesive composition constituting the adhesive sheet of the embodiment is obtained by using the characteristic (a2) component in a specified amount according to the present invention as The monomer composition of the acrylic acid copolymer (A), as clarified by comparison with Comparative Examples 1~6, 8, and 9, confirmed that it can achieve superior durability under severe conditions that cannot be achieved by conventional technology, In addition, the surface resistance value is less than 5.0×10 ⁹ Ω/□, less than 4.0×10 ⁹ Ω/□ in most of the examples, and even less than 3.0×10 ⁹ Ω/□, which has not been achieved until now. In addition, the adhesive layer constituting the adhesive sheet of the embodiment of the present invention has a very high practical value because it achieves sufficient adhesion and suppresses the occurrence of white space, which is an important characteristic of the polarizing plate.

Claims (5)

An adhesive sheet, which is an adhesive sheet for polarizing plates with a release film or release paper and an adhesive layer, is characterized in that the adhesive layer contains at least an acrylic copolymer (A ), hardener (B), and antistatic agent (C); the antistatic agent (C) is a compound containing any one of fluorine or silicon in its structure (wherein, it contains M Except for the compound represented by M ⁺ [(FSO ₂ ) ₂ N] ^- of an alkali metal), and relative to 100 parts by mass of the above-mentioned acrylic copolymer (A), it is not less than 3.5 parts by mass and less than 10 parts by mass The above-mentioned acrylic copolymer (A)-based monomer composition contains at least 1 of the (meth)acrylate monomer (a1) with 1 to 18 carbon atoms in an amount of at least 50% by mass and less than 85% by mass. species, and contain more than 15 mass% and 50 mass% or less of at least one monomer (a2) represented by the following general formula (1); and, relative to the above-mentioned monomer (a1) and the above-mentioned monomer (a2 ) in a total of 100 parts by mass, obtained by copolymerizing 0.01 to 5 parts by mass of monomers containing at least one type of ethylenically unsaturated monomer (a3) having a reactive functional group; the above-mentioned adhesive The surface resistance value of the layer is 4.0×10 ⁹ Ω/□ or less;

(In the general formula (1), ^R1 represents a hydrogen atom or a methyl group, ^R2 represents any one of a hydrogen atom, an alkyl group, an aralkyl group or an aryl group, and n represents any integer of 2 to 9). The adhesive sheet according to claim 1, wherein the reactive functional group of the above-mentioned ethylenically unsaturated monomer (a3) having a reactive functional group is selected from the group consisting of hydroxyl, carboxyl, and glycidyl and at least any one of the group consisting of nitrogen-containing groups. The adhesive sheet according to claim 1 or 2, wherein the curing agent (B) contains an isocyanate compound, and the amount used is 0.01 parts by mass or more with respect to 100 parts by mass of the acrylic copolymer (A) and Within the range of 10 parts by mass or less. The adhesive sheet according to claim 1 or 2, wherein the adhesive composition further contains a silane coupling agent (D). The adhesive sheet according to claim 1 or 2, wherein the above-mentioned adhesive composition further contains a silane coupling agent (D); the above-mentioned hardener (B) contains an isocyanate compound, and its usage is relative to the above-mentioned acrylic acid It exists in the range of 0.01 mass part or more and 10 mass parts or less per 100 mass parts of copolymers (A).