JP2015117344A - Adhesive composition, polarizer with adhesive, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an adhesive composition having proper tackiness, capable of preventing generation of a void furthermore than hitherto, and preventing generation of a void even when being used for both of a large-sized display panel and a small-sized display panel; and to provide a polarizer with an adhesive.SOLUTION: An adhesive composition contains an acrylic copolymer having a carboxyl group, an isocyanate compound, and a non-functional acrylic copolymer not having a functional group reacting with the isocyanate compound and having a weight average molecular weight of a million to two millions, and the content of the non-functional acrylic copolymer is 1 pt. mass-50 pts. mass to the 100 pts. mass acrylic copolymer having the carboxyl group.

Description

  The present invention relates to an adhesive composition, a polarizing plate with an adhesive, and a display device.

  In recent years, as a display device for displaying an image, such as a liquid crystal display device and organic electroluminescence, devices of various display methods are widely used. Among these, the liquid crystal display device is generally sandwiched between two supporting substrates such as a glass plate and includes a liquid crystal cell including a liquid crystal component oriented in a predetermined direction, a polarizing plate, a retardation film, a brightness enhancement film, and the like. The optical film is bonded to the optical film. An adhesive is used when laminating optical films or sticking an optical film to a liquid crystal cell.

  The polarizing plate used for the liquid crystal display device is disposed so that the stretching axes of the two stretched polarizing films intersect each other. In a severe environment such as high temperature and high humidity, the polarizing film easily undergoes dimensional changes accompanying expansion and contraction, and stress is generated in the polarizing plate. When the generated stress is not relaxed by the adhesive disposed between the polarizing plate and the liquid crystal cell, the residual stress is unevenly generated in the polarizing plate. As a result, the two polarizing plates arranged so that the extension axes of the polarizing film intersect each other on the front and back surfaces of the display panel are shifted in phase, and light is emitted from the four periphery of the display unit of the liquid crystal display device. Unevenness called “white spots” occurs, which leaks and becomes white.

  The occurrence of the white spots described above varies depending on the size of the display panel. In general, in a small display panel, a relatively soft adhesive (soft type adhesive) is used to relieve the generated stress in order to prevent white spots from occurring (see, for example, Patent Document 1). . On the other hand, in a large display panel, in order to prevent the occurrence of white spots, a relatively hard adhesive (hard type adhesive) is used to suppress the generation of stress.

JP-A-10-279907

As mentioned above, hard-type adhesives are said to be suitable for large display panels, but even if the current hard-type adhesives are used for large display panels, the occurrence of white spots is sufficiently prevented. Is difficult. As the display panel becomes larger, the dimensional variation of the polarizing film as the adherend increases, and it becomes difficult to prevent the occurrence of white spots.
Moreover, moderate adhesiveness is calculated | required by the adhesive from the viewpoint of workability.

  Then, the objective of this invention is providing the adhesive composition which has moderate adhesiveness and can prevent generation | occurrence | production of a white spot compared with the past, when it uses for a large sized display panel. Moreover, the objective of this invention is providing the polarizing plate with an adhesive and a display apparatus with which an image with few white spots is displayed.

  In the process leading to the present invention, in addition to the acrylic copolymer having a carboxyl group, by using a non-functional acrylic copolymer having a weight average molecular weight in a specific range not having a functional group such as a carboxyl group, Stress relaxation became high and the knowledge that white spots were effectively improved in a large display panel was obtained, and the present invention was achieved based on such knowledge.

Specific means for achieving the above object are as follows.
<1> an acrylic copolymer having a carboxyl group, an isocyanate compound, a non-functional acrylic copolymer having no functional group that reacts with the isocyanate compound and having a weight average molecular weight of 1,000,000 to 2,000,000; Including,
The pressure-sensitive adhesive composition, wherein the content of the non-functional acrylic copolymer is 1 part by mass to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group.

<2> The pressure-sensitive adhesive composition according to <1>, wherein a difference in solubility parameter between the acrylic copolymer having a carboxyl group and the non-functional acrylic copolymer is 2 or less.

<3> The adhesive according to <1> or <2>, wherein the acrylic copolymer having a carboxyl group contains 0.1% by mass to 5% by mass of a structural unit derived from an acrylic monomer having a carboxyl group. Agent composition.

<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein the isocyanate compound includes a tolylene diisocyanate compound.

<5> In any one of <1> to <4>, the content of the isocyanate compound is 10 parts by mass to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having the carboxyl group. The pressure-sensitive adhesive composition described.

<6> The pressure-sensitive adhesive composition according to any one of <1> to <5>, further including a terpene phenol-based tackifier.

<7> The pressure-sensitive adhesive composition according to <6>, wherein the terpene phenol tackifier has a softening point of 130 ° C to 145 ° C.

<8> The content of the terpene phenol tackifier is 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group, according to <6> or <7>. Adhesive composition.

<9> A polarizer,
An adhesive layer provided on the polarizer and formed by the adhesive composition according to any one of <1> to <8>,
A polarizing plate with an adhesive.

<10> a display panel for displaying images;
The polarizing plate with the adhesive according to <9>, which is disposed on at least one surface of the display panel,
A display device comprising:

  ADVANTAGE OF THE INVENTION According to this invention, when it uses for a large sized display panel which has moderate adhesiveness, the adhesive composition which can prevent generation | occurrence | production of a white spot compared with the past is provided. Moreover, according to this invention, the polarizing plate with an adhesive and display apparatus which can display an image with few white spots are provided.

  Hereinafter, the pressure-sensitive adhesive composition of the present invention, a polarizing plate with a pressure-sensitive adhesive using the same, and a display device will be described in detail.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention has no functional group that does not have a functional group that reacts with an acrylic copolymer having a carboxyl group, an isocyanate compound, and the isocyanate compound, and has a weight average molecular weight of 1,000,000 to 2,000,000. An acrylic copolymer, and the content of the non-functional acrylic copolymer is 1 part by mass to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group.

  In addition to the acrylic copolymer having a carboxyl group, the isocyanate compound, and the non-functional acrylic copolymer, the pressure-sensitive adhesive composition of the present invention may further include other crosslinking agents and silane couplings as necessary. Other components such as an agent may be included.

  In the conventional pressure-sensitive adhesive composition, an acrylic copolymer having a functional group such as a carboxyl group or a hydroxyl group is used so as to reliably crosslink with an isocyanate compound. However, in the present invention, in addition to the acrylic copolymer having a carboxyl group, a non-functional acrylic copolymer having no functional group such as a carboxyl group is used. Since such a non-functional acrylic copolymer is free with respect to the isocyanate compound, even if the polarizing film, which is the adherend, changes its dimensions and stress is generated in the adhesive, the stress is relieved. It is considered capable. Therefore, the pressure-sensitive adhesive composition of the present invention containing a non-functional acrylic copolymer can effectively suppress the occurrence of white spots even in a large display panel that generates a large amount of stress. Since the pressure-sensitive adhesive composition of the present invention is excellent in preventing white spots, it can be suitably used for a large display panel of 19 inches or more (that is, a large display device).

  Moreover, since the nonfunctional acrylic copolymer has wettability with respect to the glass plate, the adhesive property of the pressure-sensitive adhesive composition containing the nonfunctional acrylic copolymer is improved. Furthermore, since the non-functional acrylic copolymer has a weight average molecular weight of 1 million to 2 million, it is excellent in durability.

  In general, the content of the isocyanate compound is suppressed to at most about 5 parts by mass with respect to 100 parts by mass of the acrylic copolymer. However, in the pressure-sensitive adhesive composition of the present invention containing a non-functional acrylic copolymer, the isocyanate compound is contained in a high content of 10 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer. Further, it is possible to obtain a pressure-sensitive adhesive composition that can further prevent white spots from occurring and can prevent white spots from occurring even when used for both a large display panel and a small display panel. By using an isocyanate compound at a higher content than before, the pressure-sensitive adhesive composition becomes harder than before, and not only the white spots of large display panels are improved, but also the generation of stress in small display panels. Can be suppressed.

Moreover, by making the pressure-sensitive adhesive composition of the present invention contain a terpene phenol-based tackifier, the tackiness can be improved and the pressure-sensitive adhesive composition is excellent in workability.
Each component is described in detail below.

(Acrylic copolymer having a carboxyl group)
The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer having a carboxyl group (hereinafter sometimes abbreviated as “acrylic copolymer”). The acrylic copolymer having a carboxyl group has a structural unit derived from an acrylic monomer having a carboxyl group, and may further have a structural unit derived from another monomer.

  Examples of the acrylic monomer having a carboxyl group include acrylic acid (AA), methacrylic acid (MAA), ω-carboxy-polycaprolactone mono (meth) acrylate, succinic acid monohydroxyethyl (meth) acrylate, and maleic acid monohydroxyethyl. (Meth) acrylate, monohydroxyethyl fumarate (meth) acrylate, monohydroxyethyl phthalate (meth) acrylate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate, (meth) acrylic acid dimer, etc. . These may be used alone or in combination of two or more. Among them, acrylic acid is preferable because it has high reactivity with other monomers during the copolymerization reaction and can reduce unreacted monomers.

  The content ratio of the structural unit derived from the acrylic monomer having a carboxyl group in the acrylic copolymer is preferably 0.1% by mass to 5% by mass, more preferably 1% by mass to 5% by mass, and 1% by mass to 3 mass% is still more preferable. When the content ratio is 0.1% by mass or more, crosslinking with an isocyanate described later is effectively performed, and when the content ratio is 5% by mass or less, the pot life can be suppressed from being shortened.

Examples of other monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, Examples thereof include monomers having no functional group such as phenoxyethyl (meth) acrylate and benzyl (meth) acrylate. These may be used alone or in combination of two or more.
Among these, alkyl (meth) acrylates having an alkyl group having 1 to 4 carbon atoms and phenoxyethyl (meth) acrylate are preferable in terms of easy adjustment of cohesive force and adhesive force of the pressure-sensitive adhesive, and those having 1 to 4 carbon atoms. Alkyl acrylates having an alkyl group and phenoxyethyl acrylate are more preferable, and n-butyl acrylate is used as a main component, methyl acrylate and n-butyl acrylate are used in combination, or n-butyl acrylate is used as a main component, and phenoxyethyl is used. It is more preferable to use acrylate and n-butyl acrylate together, or to use methyl acrylate, phenoxyethyl acrylate, and n-butyl acrylate together with n-butyl acrylate as a main component.

  The content of the structural unit derived from n-butyl acrylate (BA) in the acrylic copolymer is preferably 75% by mass to 95% by mass, and more preferably 80% by mass to 95% by mass. 80% by mass to 90% by mass is more preferable.

  As another monomer, when methyl acrylate (MA) and / or phenoxyethyl acrylate (PHEA) and n-butyl acrylate (BA) are used in combination, the mass ratio of MA and / or PHEA to BA ((MA + PHEA) / BA ) Is preferably 0.01 to 1, more preferably 0.1 to 1, and still more preferably 0.1 to 0.7. When the mass ratio of MA and / or PHEA is 0.01 or more, the polarity of the resin is high, and even if a large amount of isocyanate compound is contained, it is easy to mix, and when it is 1 or less, tackiness is easily maintained. There is a tendency.

  The total content of structural units derived from MA and / or PHEA and BA in the acrylic copolymer is preferably 95% by mass to 99.9% by mass, more preferably 95% by mass to 99% by mass, A mass% to 98 mass% is more preferable.

As another monomer, it is preferable to further use a monomer having a functional group other than a carboxyl group. Further, other monomers having a functional group other than a carboxyl group that can be used in combination include monomers having a hydroxyl group such as 2-hydroxyethyl acrylate (2HEA) and 4-hydroxybutyl acrylate (4HBA), N, N-dimethylacrylamide (DMAA). Monomers having an amide group such as 4-hydroxybutyl acrylate glycidyl ether (4HBAGE), monomers having an epoxy group such as glycidyl methacrylate (GMA), and the like. Monomers having a hydroxyl group are preferred from the viewpoint of cohesive strength. 2-hydroxyethyl acrylate is preferred.
In the acrylic copolymer, the total amount of structural units derived from other monomers having a functional group other than a carboxyl group is preferably 1% by mass or less, more preferably 0.5% by mass or less, More preferably, it is 0.2 mass% or less.

  A particularly preferred acrylic copolymer is a copolymer containing at least a structural unit derived from acrylic acid, n-butyl acrylate, methyl acrylate and / or phenoxyethyl acrylate, specifically, AA / BA / MA copolymer, AA / BA / MA / 2HEA copolymer, AA / BA / PHEA copolymer, AA / BA / 2HEA / PHEA copolymer, AA / BA / MA / 2HEA / PHEA A copolymer is mentioned.

  The weight average molecular weight of the acrylic copolymer is preferably 300,000 to 2,000,000, more preferably 500,000 to 2,000,000, and 700,000 to 1,800,000. More preferably, it is 000.

In the present specification, the weight average molecular weight (Mw) of the acrylic copolymer is a value measured by the following method. That is, it is measured according to the following (1) to (3).
(1) An acrylic copolymer solution is coated on a release sheet (release sheet) and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The film-like acrylic copolymer obtained in (1) is dissolved in tetrahydrofuran so that the solid content is 0.2% by mass.
(3) Under the following conditions, the weight average molecular weight (Mw) of the (meth) acrylic copolymer is measured using gel permeation chromatography (GPC).
<Conditions>
・ GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
・ Column: TSK-GEL GMHXL (4 used)
-Mobile phase solvent: Tetrahydrofuran-Standard sample: Standard polystyrene-Flow rate: 0.6 ml / min
-Column temperature: 40 ° C

  The glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of −50 ° C. to −30 ° C., more preferably in the range of −48 ° C. to −40 ° C. When the Tg is −50 ° C. or higher, the elastic modulus can be adjusted, and the durability and the whiteout property are excellent. Moreover, when Tg is −30 ° C. or lower, the tackiness and bonding suitability are excellent without significantly impairing the viscosity.

In this specification, the glass transition temperature (Tg) of the acrylic copolymer is a molar average glass transition temperature determined by the following calculation. _{Tg 1,} Tg 2 of the following formulas, ... and Tg _n, the components 1, the glass transition temperature of the components 2, ... and component n respectively homopolymers, absolute temperature (° K). m ₁ , m ₂ ,... and _mn are the mole fractions of the respective components.

[Calculation formula of glass transition temperature (Tg)]

  The “glass transition temperature (Tg) of the homopolymer” referred to herein includes L.P. E. The glass transition temperature of the monomer described in Nielsen, translated by Shigeharu Onoki, “Mechanical properties of polymers”, pages 11 to 35, is applied.

  The content of the acrylic copolymer in the pressure-sensitive adhesive composition is preferably in the range of 50% by mass to 74% by mass and more preferably in the range of 54% by mass to 69% by mass with respect to the total solid content. When the content of the acrylic copolymer is within the above range, the pressure-sensitive adhesive is given hardness, the generation of stress is suppressed, and the occurrence of white spots is effectively suppressed.

  The polymerization method of the acrylic copolymer in the present invention is not particularly limited, and methods such as solution polymerization, emulsion polymerization, and suspension polymerization can be applied. Solution polymerization is preferred because the treatment process is relatively simple and can be performed in a short time.

  In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, and the number is stirred in a nitrogen stream or under reflux of the organic solvent. The reaction is heated for an hour. The polymerization initiator is not particularly limited, and for example, an azo compound can be used.

(Isocyanate compound)
The pressure-sensitive adhesive composition of the present invention contains at least one isocyanate compound.
A preferred example of the isocyanate compound is a tolylene diisocyanate compound. As the tolylene diisocyanate compound, a tolylene diisocyanate compound derived from tolylene diisocyanate such as tolylene diisocyanate dimer or trimer, or an adduct of tolylene diisocyanate and a polyol such as trimethylolpropane may be used. it can. These may be used alone or in combination of two or more.

  As the tolylene diisocyanate compound, a commercially available product may be used. As an example of a commercially available product, “Coronate L” (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd. can be suitably used.

  The content of the isocyanate compound is not particularly limited. From the viewpoint of preventing white spots regardless of the size of the display panel, the isocyanate compound may be contained in an amount of 10 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group. It is preferably 15 to 50 parts by mass, more preferably 20 to 45 parts by mass, and particularly preferably 30 to 40 parts by mass.

  When the content of the isocyanate compound is 10 parts by mass or more with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group, the occurrence of white spots can be prevented more than before, and a large display panel and a small size can be obtained. Even if it is used for both display panels, white spots can be prevented from occurring. When the content of the isocyanate compound is 50 parts by mass or less, white turbidity caused by carbon dioxide generated by the reaction of the isocyanate is suppressed, and the appearance is improved. In addition, when content of an isocyanate compound is increased, there exists a tendency for tackiness to fall. In this case, it becomes the adhesive composition excellent in tackiness by containing the below-mentioned terpene phenol type tackifier.

  In addition, even if the content of the isocyanate compound is less than 10% by mass, the stress relaxation ability is increased by including the non-functional acrylic copolymer, so that white spots occur in a large display panel. Can be prevented.

(Non-functional acrylic copolymer)
The pressure-sensitive adhesive composition of the present invention contains a nonfunctional acrylic copolymer having no functional group that reacts with an isocyanate compound and having a weight average molecular weight of 1,000,000 to 2,000,000. A non-functional acrylic copolymer is comprised by the structural unit derived from the acrylic monomer which does not have a functional group which reacts with an isocyanate compound. Here, the “functional group that reacts with an isocyanate compound” refers to a carboxyl group, a hydroxyl group, an amino group, a mercapto group, and the like.

  Examples of the acrylic monomer having no functional group that reacts with an isocyanate compound include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and t-butyl (meth). Acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl ( Alkyl (meth) acrylates such as meth) acrylate and stearyl (meth) acrylate; (meth) acrylates having an aromatic ring such as phenoxyethyl (meth) acrylate and benzyl (meth) acrylate; cyclohexyl (meth) Acrylate, isobornyl (meth) having an alicyclic structure such as acrylates (meth) acrylate; 2-methoxyethyl (meth) alkoxyalkyl acrylates such as (meth) acrylate. These are used in combination of two or more. By setting it as the copolymer which combined 2 or more types, compatibility with the acrylic copolymer which has the above-mentioned carboxyl group improves.

  Among them, as an acrylic monomer having no functional group that reacts with an isocyanate compound in terms of easily adjusting the cohesive force and adhesive force of the pressure-sensitive adhesive, an alkyl (meth) acrylate having an alkyl group having 1 to 4 carbon atoms is used. An alkyl acrylate having an alkyl group having 1 to 4 carbon atoms is more preferable, and n-butyl acrylate (BA) is more preferably used as a main component.

  The content of the structural unit derived from n-butyl acrylate (BA) in the non-functional acrylic copolymer is preferably 60% by mass to 99% by mass, and preferably 70% by mass to 90% by mass. More preferably, it is 80 mass%-90 mass%.

  As an acrylic monomer having no functional group that reacts with an isocyanate compound used in combination with n-butyl acrylate, methyl acrylate (MA), phenoxyethyl acrylate (PHEA), 2-methoxyethyl acrylate (2-MTA), t-butyl Examples include acrylate (tBA), lauryl acrylate (LA), isostearyl acrylate (ISTA), cyclohexyl acrylate (CHA), isobornyl acrylate (IBXA), n-octyl acrylate (NOAA), stearyl acrylate (STA), and the like. Among them, methyl acrylate (MA), phenoxyethyl acrylate (PHEA), and 2-methoxyethyl acrylate (2-MTA) are preferable. When these acrylic monomers are used in combination, the resulting non-functional acrylic copolymer is likely to be mixed with the acrylic copolymer having a carboxyl group.

  A particularly preferred non-functional acrylic copolymer is derived from n-butyl acrylate and at least one selected from methyl acrylate, phenoxyethyl acrylate (PHEA) and 2-methoxyethyl acrylate (2-MTA). A copolymer containing at least a unit, specifically, a copolymer of BA / MA, a copolymer of BA / PHEA, a copolymer of BA / MA / PHEA, and a copolymer of BA / 2-MTA Coalescence is mentioned.

  The weight average molecular weight of the non-functional acrylic copolymer is 1 million to 2 million, preferably 1 million to 1.8 million, and more preferably 1.1 million to 1.7 million. If the weight average molecular weight of the non-functional acrylic copolymer is less than 1 million, the durability tends to be inferior, and if it exceeds 2 million, synthesis becomes difficult. The measuring method of the weight average molecular weight of a functional acrylic copolymer is based on the said method.

  The glass transition temperature (Tg) of the non-functional acrylic copolymer is preferably −30 ° C. or lower, more preferably −40 ° C. or lower, from the viewpoint of improving adhesiveness. The method for measuring the glass transition temperature (Tg) of the nonfunctional acrylic copolymer is in accordance with the above method.

The non-functional acrylic copolymer preferably has higher compatibility as the solubility parameter thereof is closer to the solubility parameter of the acrylic copolymer having a carboxyl group. Specifically, the difference between the solubility parameters of each is 2 or less. Is preferably 1 or less, more preferably 0.5 or less, and particularly preferably 0.25 or less.
Moreover, in this specification, the solubility parameter (SP value, unit: (cal / cm ³ ) ^0.5 ) of the acrylic copolymer is calculated based on the molecular attractive constant G of the structural unit constituting the resin. It is what is done. In the case of an acrylic copolymer, the SP value of each homopolymer of each structural unit constituting the resin is calculated by the following formula, and the mole fraction of each structural unit is calculated for each of the SP values. The solubility parameters are calculated by summing the multiplications.
SP value of homopolymer = dΣG / M
Here, d represents the density (g / l) of the homopolymer, ΣG represents the sum of molecular attractive constants in the molecules of the structural unit, and M represents the molecular weight (g / mol) of the structural unit. .

  From the viewpoint of increasing the compatibility with the acrylic copolymer having a carboxyl group, the non-functional acrylic copolymer is composed of a main structural unit constituting the non-functional acrylic copolymer and an acrylic copolymer having a carboxyl group. The main structural units constituting the polymer are preferably approximate or the same, and more preferably the same. Specifically, when the structural unit constituting the acrylic copolymer having a carboxyl group mainly contains a structural unit derived from BA and MA, the structural unit constituting the non-functional acrylic copolymer is also BA and MA. It is preferable that the structural unit derived from is mainly included. In the non-functional acrylic copolymer and the acrylic copolymer having a carboxyl group, examples of suitable combinations in the case where the main structural units are similar or the same are shown below.

In the above table, the main component means one whose content exceeds 50% by mass.

  The content of the non-functional acrylic copolymer is in the range of 1 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group, and preferably in the range of 1 to 30 parts by mass. The range of 1 to 20 parts by mass is more preferable, and 5 to 15 parts by mass is even better. When the content of the non-functional acrylic copolymer is less than 1 part by mass, it is difficult to obtain an effect due to the addition of the non-functional acrylic copolymer, and when it exceeds 50 parts by mass, the hardness is impaired and durability is increased. descend.

(Terpene phenolic tackifier)
The pressure-sensitive adhesive composition of the present invention preferably contains a terpene phenol tackifier. The terpene phenol tackifier is a resin obtained by copolymerizing a terpene monomer and a phenol compound. The terpene phenol-based tackifier is easy to mix even in a pressure-sensitive adhesive composition containing more isocyanate compound than before, and can effectively exhibit tackiness.

  The terpene phenol tackifier preferably has a softening point of 130 ° C. to 145 ° C., more preferably 130 ° C. to 140 ° C., from the viewpoint of mixing properties in the pressure-sensitive adhesive composition.

  The softening point of the terpene phenol tackifier is a value measured based on the softening point test method (ring and ball method) defined in JIS K 2207 (2006 version).

  A terpene phenol type tackifier may be used individually by 1 type, and may be used in combination of 2 or more type. Examples of terpene phenol tackifiers include copolymers of monocyclic monoterpenes such as α-pinene, β-pinene and dipentene (limonene) with phenolic compounds such as phenol, cresol and bisphenol A. Can do.

  As the terpene phenol-based tackifier, commercially available products may be used. Examples of commercially available products include “YS Polystar TH130” (trade name, softening point 130 ° C.), “YS Polystar U115” (Yasuhara Chemical Co., Ltd.) Product name, softening point 115 ° C), "YS Polystar T145" (trade name, softening point 145 ° C), "YS Polystar T140" (trade name, softening point 140 ° C), "YS Polystar T130" (trade name, softening point) 130 ° C.), “YS Polystar T115” (trade name, softening point 115 ° C.), “YS Polystar 2130” (trade name, softening point 130 ° C.), “YS Polystar 2115” (trade name, softening point 115 ° C.), “ “YS Polystar S145” (trade name, softening point 145 ° C.), “YS Polystar N125” (trade name, softening point 125 ° C.), “My “IAce G150” (trade name, softening point 150 ° C.), “Mighty Ace G125” (trade name, softening point 125 ° C.), “Mighty Ace K125” (trade name, softening point 125 ° C.), “Arakawa Chemical Industries Ltd.” “Tamanol 901” (trade name, softening point: 130 ° C.) can be preferably used.

  The content of the terpene phenolic tackifier in the pressure-sensitive adhesive composition is preferably 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the total amount of the acrylic copolymer having a carboxyl group. It is more preferable that it is 8 parts by mass. When the content of the terpene phenol tackifier is 10 parts by mass or less, stress suppression tends to be more exhibited.

(Silane coupling agent)
The pressure-sensitive adhesive composition of the present invention may contain a silane coupling agent. When the pressure-sensitive adhesive composition contains a silane coupling agent, even if a display device (for example, a liquid crystal display device) incorporating a polarizing plate is exposed to a high-temperature and high-humidity environment, There is a tendency that the gap is difficult to peel off.

  Examples of the silane coupling agent include polymerizable unsaturated group-containing silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercapto. Mercapto group-containing silane compounds such as propyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, and epoxies such as 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Silane compounds having a structure, such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Amino group-containing silane compound, and tris - (3-trimethoxysilylpropyl) isocyanurate. These may be used alone or in combination of two or more.

  A commercially available silane coupling agent may be used, and “KBM-403” (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. can be suitably used as an example of a commercially available product.

  As content of the silane coupling agent in an adhesive composition, the range of 0.01 mass part-2.0 mass parts is preferable with respect to 100 mass parts of total amounts of an acryl-type copolymer. When the content of the silane coupling agent is within the above range, the durability of the pressure-sensitive adhesive layer can be further improved.

  In addition to the above components, the pressure-sensitive adhesive composition of the present invention may further contain various additives such as ultraviolet absorbers, solvents and the like.

<Polarizing plate with adhesive>
The polarizing plate with the pressure-sensitive adhesive of the present invention has at least a polarizer and a pressure-sensitive adhesive layer provided on the polarizer and formed of the pressure-sensitive adhesive composition of the present invention described above.

  In general, for example, a polyvinyl alcohol (PVA) film is used as the polarizer. The polarizer can be used as a polarizing plate having, for example, a three-layer structure (for example, TAC / polarizer / TAC) held between protective sheets such as triacetyl cellulose (TAC).

  For example, a polarizing plate with a pressure-sensitive adhesive is provided by providing a pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive composition of the present invention described above to at least one surface of a polarizing plate having a three-layer structure of TAC / polarizer / TAC. Is produced. In this case, the pressure-sensitive adhesive composition may be applied on the polarizing plate, but is preferably applied on a protective sheet (peeling sheet) that is peeled off during use. Specifically, the pressure-sensitive adhesive composition of the present invention is coated on a protective sheet (release sheet), dried, and a pressure-sensitive adhesive layer is formed on the protective sheet to produce a pressure-sensitive adhesive sheet. A pressure-sensitive adhesive-attached polarizing plate is produced by transferring and curing the agent layer on the polarizing plate. The application of the pressure-sensitive adhesive composition can be suitably performed by a coating method such as a dipping method, a coating method, or an ink jet method using a liquid pressure-sensitive adhesive composition. Among these, the application method is preferable.

  The pressure-sensitive adhesive composition applied on the protective sheet (release sheet) is preferably dried at 70 ° C. to 120 ° C. under drying conditions of about 1 minute to 3 minutes using a hot air dryer or the like.

Furthermore, from the viewpoint of protecting the contact surface with the adherend, a protective sheet (peeling sheet) for protecting the exposed surface is provided in close contact with the exposed surface of the adhesive layer provided on the polarizing plate. It is preferable. As this protective sheet, a synthetic resin sheet such as polyester subjected to a release treatment with a release agent such as a fluororesin, paraffin wax, or silicone is suitable so that it can be easily peeled off from the adhesive layer. Used for. When pasting on a glass plate or the like of a display panel, the protective sheet is peeled off, and the exposed surface of the pressure-sensitive adhesive layer is adhered to the glass plate or the like.
Moreover, you may further provide the surface protection sheet which protects the surface (exposed surface) of the side in which the adhesive layer of a polarizing plate is not provided. As the surface protective sheet, a protective film or the like that is adhesively processed on one side of a PET film is preferably used.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably 1 μm to 100 μm, more preferably 5 μm to 50 μm, and still more preferably 15 μm to 30 μm in terms of the thickness after drying.

The polarizing plate with the pressure-sensitive adhesive of the present invention is applicable even when the size of the laminated liquid crystal cell is 19 inches wide (260 mm × 415 mm) or more. When the size of the liquid crystal cell is 19 inches wide (260 mm × 415 mm) or more, expansion and contraction due to the influence of heat and humidity of the polarizing plate are increased. Therefore, in the conventional polarizing plate with an adhesive, since the stress is not sufficiently suppressed when exposed to high temperature and high humidity, it occurs around the bezel when the light source of a large display device (for example, a liquid crystal display device) is turned on. It is difficult to suppress the occurrence of “white spots”. In contrast, the pressure-sensitive adhesive polarizing plate of the present invention has a structure in which the copolymer resin design and the type and amount of the cross-linking agent are appropriate, so that stress suppression is possible even when exposed to high temperature and high humidity. Is enough. It is suitable for a liquid crystal cell having a size of 19 inches wide (260 mm × 415 mm) or larger, and even when applied to a small display device (liquid crystal display device) of less than 19 inches (or less than 10 inches), moderate stress Occurrence of white spots is suppressed due to relaxation.
Moreover, in the adhesive sheet which provided the conventional adhesive composition, the part which is less than the size of one polarizing plate was discarded. On the other hand, since the pressure-sensitive adhesive composition of the present invention does not need to be used depending on the size of the polarizing plate, it is used for a small-size polarizing plate even in a portion that is less than the size of the large-sized polarizing plate. The adhesive sheet can be used without waste.

<Display device>
The display device of the present invention is configured by providing a display panel for displaying an image and the above-described polarizing plate with an adhesive of the present invention disposed on at least one surface of the display panel. Examples of the display panel include a liquid crystal display panel in which a liquid crystal compound is sealed, an organic electroluminescence display panel, and the like.

  As an example of the display device of the present invention, the polarizing plate with the pressure-sensitive adhesive of the present invention is disposed on both surfaces of the liquid crystal display panel so that the pressure-sensitive adhesive layer is in contact with the surface of the liquid crystal display panel (for example, the surface of the glass plate). And a liquid crystal display device having a structure (polarizing plate / adhesive layer / liquid crystal display panel / adhesive layer / polarizing plate structure) in which polarizing plates are bonded to both surfaces of the liquid crystal display panel via an adhesive layer. Can do.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof.

<Manufacture of acrylic copolymer having carboxyl group>
(Production Example B)
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, n-butyl acrylate (BA) 90.25 parts by mass, methyl acrylate (MA) 9.5 parts by mass, 2-hydroxy Ethyl acrylate (2HEA) 0.15 parts by mass, acrylic acid (AA) 0.1 parts by mass, ethyl acetate (EAc) 110 parts by mass, and azobisdimethylvaleronitrile (ABVN) 0.1 parts by mass were mixed. Thereafter, the inside of the reactor was purged with nitrogen. Thereafter, while stirring the obtained mixture, the mixture in the reactor was heated to 65 ° C. and held for 8 hours to carry out the polymerization reaction. After completion of the polymerization reaction, the reaction mixture was diluted with ethyl acetate to adjust the solid content to 27.0% by mass. Thus, a solution of resin B (acrylic copolymer) which is a BA / MA / 2HEA / AA copolymer was obtained.

(Production Examples C to J, A)
A solution of resins C to J (acrylic copolymer) and a solution of resin A for a comparative example were produced in the same manner as in Production Example B, except that the monomer composition and blending ratio were changed as shown in Table 2 below. Got.

<Manufacture of non-functional acrylic copolymer>
(Production Example 1)
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, n-butyl acrylate (BA) 85 parts by mass, methyl acrylate (MA) 15 parts by mass, ethyl acetate (EAc) 70 parts by mass And 0.1 parts by mass of azobisdimethylvaleronitrile (ABVN) were added and mixed, and then the inside of the reactor was purged with nitrogen. Thereafter, while stirring the obtained mixture, the mixture in the reactor was heated to 65 ° C. and held for 8 hours to carry out the polymerization reaction. After completion of the polymerization reaction, the reaction mixture was diluted with ethyl acetate to adjust the solid content to 15.0% by mass. In this way, a solution of the modified resin B (non-functional acrylic copolymer) which is a BA / MA copolymer was obtained. The weight average molecular weight of the obtained modified resin B was measured according to the following (1) to (3). The weight average molecular weight of the modified resin B is shown in the following Table 3 (in Table 3, simply described as “molecular weight”).

(1) The acrylic copolymer solution was coated on a release sheet (release sheet) and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The film-like acrylic copolymer obtained in (1) was dissolved in tetrahydrofuran so that the solid content was 0.2% by mass.
(3) The weight average molecular weight (Mw) of the (meth) acrylic copolymer was measured using gel permeation chromatography (GPC) under the following conditions.

<Conditions>
・ GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
・ Column: TSK-GEL GMHXL (4 used)
-Mobile phase solvent: Tetrahydrofuran-Standard sample: Standard polystyrene-Flow rate: 0.6 ml / min
-Column temperature: 40 ° C

(Production Examples 2 to 6)
Except having changed the composition and the mixture ratio of the monomer as shown in Table 3 below, the solution for the modified resins C to E (non-functional acrylic copolymer) and the comparative example were the same as in Production Example 1. Solutions of modified resins A and F were obtained.

(Production Examples 7 and 8)
In Production Example 1, the polymerization reaction conditions were changed from 70 parts by mass of ethyl acetate (EAc) to 110 parts by mass of ethyl acetate (EAc) and 60 parts by mass of ethyl acetate (EAc). Thus, a solution of the modified resins H and I (non-functional acrylic copolymer), which are BA / MA copolymers, was obtained.

(Production Examples 9 and 10)
In Production Example 1, the polymerization reaction conditions were changed from 70 parts by mass of ethyl acetate (EAc) to 140 parts by mass of ethyl acetate (EAc) and 40 parts by mass of ethyl acetate (EAc), respectively, as in Production Example 1. As a result, a solution (non-functional acrylic copolymer) of modified resins G and J for comparative example, which is a BA / MA copolymer, was obtained.

Example 1
-Preparation of adhesive composition-
As the acrylic copolymer, 370.4 parts by mass of the resin B solution (100 parts by mass as the solid content of the resin B), which is the BA / MA / 2HEA / AA copolymer obtained in Production Example B, and none As the functional acrylic copolymer, 66.7 parts by mass of the modified resin B solution (10 parts by mass as the solid content of the modified resin), which is the BA / MA copolymer obtained in Production Example 1, and isocyanate 40 parts by mass of Coronate L as a compound (an isocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd., 30 parts by mass as an active ingredient of an isocyanate compound) and YS Polystar TH130 (manufactured by Yashara Chemical Co., Ltd., softening point 130) as a terpene phenol-based tackifier ° C) 5 parts by mass and 0.1 parts by mass of KBM-403 as a silane coupling agent were sufficiently mixed with stirring, To obtain things.

-Production of optical film sample-
The pressure-sensitive adhesive composition was applied to the release agent-treated surface of the release film surface-treated with the silicone-based release agent so that the coating amount after drying was 25 g / cm ² . Next, this was dried at 100 ° C. for 90 seconds with a hot-air circulating dryer to form an adhesive layer on the release film. Subsequently, a polarizing plate (which has a laminated structure of TAC film / PVA film / TAC film by laminating cellulose triacetate (TAC) films on both sides of a polarizer mainly composed of polyvinyl alcohol (PVA) film); thickness of about 190 μm ] And the surface of the pressure-sensitive adhesive layer were overlapped and bonded together, and pressed through a pressure nip roll. After pressure bonding, the film was cured for 10 days under an environmental condition of 23 ° C. and 65% RH, and a pressure-sensitive adhesive polarizing plate having a laminate structure of release film / pressure-sensitive adhesive layer / polarizing plate was produced as an optical film sample.

-Evaluation-
The following evaluation was performed using the polarizing plate with an adhesive produced above. The evaluation results are shown in Table 4 below.

(1) Durability (4.3 inches)
54 mm × 96 mm (long side) test piece (4.3 inches) obtained by cutting the pressure-sensitive adhesive polarizing plate prepared in “Preparation of optical film sample” so that the long side is 45 ° with respect to the absorption axis. Was prepared, and the release film was peeled from the test piece. By sticking the surface of the pressure-sensitive adhesive layer exposed by peeling to one surface of a 0.7 mm-thick alkali-free glass plate (# 1737, manufactured by Corning), the test piece is stacked on the glass plate, and a laminator is used. The laminate was pasted. Next, this laminate was subjected to autoclave treatment (50 ° C., 5 kg / cm ² , 20 minutes), and allowed to stand at 23 ° C. and 65% RH for 24 hours. Then, it was left for 500 hours in a Dry environment (80 ° C., 0% RH) under high temperature and low humidity conditions or a WET environment (60 ° C., 90% RH) under high temperature and high humidity conditions. Alternatively, high / low temperature was repeated (300 cycles of -40 ° C. for 30 minutes and 85 ° C. for 30 minutes as one cycle), and the mixture was put into an H / S environment.
After the standing time had elapsed, the state of foaming, floating and peeling was visually observed and evaluated according to the following evaluation criteria.

<Evaluation criteria>
A: Foaming, floating, and peeling were not observed at all.
B: Although foaming, floating, and peeling were slightly observed, it was within an allowable range.
C: Foaming, floating, and peeling were noticeable.

(2) White spot (2-1) White spot phenomenon (small size: 7 inches)
Two test pieces were prepared by changing the size of the test piece in “(1) Durability (4.3 inches)” to 88 mm × 156 mm (7.0 inches), and a non-alkali glass plate having a thickness of 0.7 mm. A test sample was prepared by pasting both sides of # 1737 (manufactured by Corning) so that the polarization axes were orthogonal to each other. Next, this test sample was subjected to autoclaving (50 ° C., 5 kg / m ² , 20 minutes), and allowed to stand for 24 hours at 23 ° C. and 50% RH. Then, it was left for 500 hours in a dry environment (70 ° C., 0% RH). After standing, each was placed on the backlight of a liquid crystal monitor under the conditions of 23 ° C. and 50% RH, and the white spots were visually observed.

<Evaluation criteria>
A: No white spots were observed at all.
B: Almost no white spots were observed.
C: Some white spots were recognized, but were within an allowable range.
D: Large white spots were recognized.

(2-2) White spot phenomenon (Large size: 19 inches)
In “(2-1) White spot phenomenon (7 inches)”, except that the size of the test piece obtained by cutting the polarizing plate with adhesive was changed to 240 mm × 427 mm (19 inches), “(2 -1) Evaluation was made in the same manner as the “white spot phenomenon (7 inches)”.

(3) Appearance An autoclave treatment (50 ° C., 5 kg / cm ² , 20 minutes) was applied to the laminate prepared in the same manner as “(1) Durability (4.3 inches)”, and 23 ° C., 65% It was left for 24 hours under the condition of RH. The appearance after standing was visually observed and evaluated according to the following evaluation criteria.

<Evaluation criteria>
A: Whitening was not recognized.
B: Whitening occurred.

(4) Tackiness (probe tack)
Using a probe tack tester TAC-1000 (Resca Co., Ltd.), the test was performed under the conditions of a load of 200 gf / cm ² , a speed of 5 mm / min and a contact time of 0.1 sec.

<Evaluation criteria>
A: 80 (gf) or more and excellent workability.
B: It is less than 80 (gf) and is inferior in workability.

(5) Adhesive force After the polarizing plate with pressure-sensitive adhesive prepared in “Preparation of optical film sample” was cut into 25 mm × 150 mm, this polarizing film piece was made into a thickness manufactured by Corning using a desktop laminating machine. A test sample was prepared by pressure bonding to a non-alkali glass plate “# 1737” of 0.7 mm. This sample was autoclaved (50 ° C., 5 kg / cm ² , 20 minutes). Next, this sample was allowed to stand under conditions of 23 ° C. and 65% RH for 24 hours, and then the adhesive strength at 180 ° peeling (peeling speed: 300 mm / min) was measured.

<Evaluation criteria>
A: It is 1N / inch or more and 30N / inch or less, and has excellent bonding properties.
B: It is less than 1N / inch, and is inferior to pasting property.

(Examples 2-29, Comparative Examples 1-8)
In Example 1, the type of acrylic copolymer, the type of modified resin or its content ratio (parts by mass), the content ratio of isocyanate compounds (parts by mass), or the content ratio of tackifiers (parts by mass) are as follows: Except having changed as shown in Table 4, it carried out similarly to Example 1, and prepared the adhesive composition, produced the polarizing plate with an adhesive using this adhesive composition, and evaluated it. In Table 4, “Unevaluated” indicates that whitening was observed and evaluation was not possible.

  As shown in Table 4, in the examples, regardless of the DRY environment, the WET environment, and the H / S environment, the occurrence of foaming, floating, and peeling was suppressed, and good durability was obtained. Moreover, in the Example, generation | occurrence | production of the white spot of the test piece was suppressed and the favorable adhesive force was shown.

Claims (10)

An acrylic copolymer having a carboxyl group, an isocyanate compound, and a nonfunctional acrylic copolymer having no functional group that reacts with the isocyanate compound and having a weight average molecular weight of 1,000,000 to 2,000,000. ,
The pressure-sensitive adhesive composition, wherein the content of the non-functional acrylic copolymer is 1 part by mass to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group.   The pressure-sensitive adhesive composition according to claim 1, wherein the difference in solubility parameter between the acrylic copolymer having a carboxyl group and the non-functional acrylic copolymer is 2 or less.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the acrylic copolymer having a carboxyl group contains 0.1 mass% to 5 mass% of a structural unit derived from an acrylic monomer having a carboxyl group.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the isocyanate compound contains a tolylene diisocyanate compound.   The pressure-sensitive adhesive according to any one of claims 1 to 4, wherein a content of the isocyanate compound is 10 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having the carboxyl group. Composition.   The pressure-sensitive adhesive composition according to any one of claims 1 to 5, further comprising a terpene phenol tackifier.   The pressure-sensitive adhesive composition according to claim 6, wherein the terpene phenol tackifier has a softening point of 130C to 145C.   The pressure-sensitive adhesive composition according to claim 6 or 7, wherein a content of the terpene phenol tackifier is 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the acrylic copolymer having the carboxyl group. . A polarizer,
An adhesive layer provided on the polarizer and formed by the adhesive composition according to any one of claims 1 to 8,
A polarizing plate with an adhesive. A display panel for displaying images,
The pressure-sensitive adhesive polarizing plate according to claim 9 disposed on at least one surface of the display panel,
A display device comprising: