JPH0782542A - Pressure-sensitive adhesive for polarizing plate or phase plate - Google Patents

Abstract

PURPOSE:To provide a pressure sensitive adhesive used for a polarizing plate or a phase plate used in e.g. a liquid crystal display panel and being excellent in cuttability as well as heat ad humidity resistances. CONSTITUTION:This adhesive comprises a graft or block copolymer which satisfies the requirements that the overall molecular weight is 400000-2000000, there are two Tg peaks, the difference between these Tgs is 70 deg.C or above, and the higher Tg is 50 deg.C or above, and in which the segment component comprises at least one member selected from among homopolymers and copolymers of styrene, acrylonitrile and methyl methacrylate, polyesters and polyamides, the molecular weight of the segment of the higher Tg is within the range of 500-1000000, and this segment accounts for 5-40wt.% of the total weight. This adhesive has both the excellent pressure-sensitive adhesiveness realized by one component and the excellent cuttability realized by the other component of a higher Tg.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive for a polarizing plate or a retardation plate used in a liquid crystal display plate or the like, which is coated on at least one surface of the polarizing plate or the retardation plate and has an adhesive layer. The present invention relates to a pressure-sensitive adhesive suitable for use as a polarizing plate or a retardation plate.

[0002]

2. Description of the Related Art Conventionally, a polarizing plate formed by protecting a polyvinyl alcohol sheet or the like having a polarizing property by adsorbing a polarizing element with a thermoplastic resin film, and protecting the polarizing plate, for example, a liquid crystal cell surface A technique for forming a liquid crystal display panel by stacking on the above is well known. The laminating means is usually performed by forming an adhesive layer on the surface of the polarizing plate and interposing the adhesive layer.

In order to obtain a polarizing plate having an adhesive layer, a predetermined adhesive solution prepared in advance is temporarily attached to a strip-shaped carrier having a release-treated surface, and an adhesive tape is used. It is stored as a long roll, and while being unwound as necessary, it is cut into a predetermined size such as a polarizing plate, and the adhesive layer is then attached to one surface of a separately prepared polarizing plate. It is obtained by transferring or cutting into a predetermined size after the transfer. When laminating on a liquid crystal display panel, the carrier is peeled off and pressed against the liquid crystal cell surface to laminate.

[0004]

The main component of this pressure-sensitive adhesive is an acrylic resin, which has characteristics such as tackiness and transparency. However, the liquid crystal display panel itself is gradually required to have durability in a severe environment. Currently, heat resistance around 85 ℃, 6
Moisture resistance of 90% RH at a temperature of 0 ° C. is required. In other words, it has become necessary to adopt an adhesive that can have the original adhesiveness even under such a harsh environment.

Therefore, a pressure-sensitive adhesive composed of a copolymer containing an acrylic acid alkyl ester as a main component and acrylic acid having a strong polar group and acrylic acid amide as an auxiliary component has been used. However, a polarizing plate or the like having such an adhesive layer is cut in the cutting step, that is, when it is unwound from the roll temporarily attached to the carrier, or after it is laminated on the polarizing plate or the like, If part of the adhesive is not cut and the cutting sheet does not come off and you try to force it apart, the phenomenon that the adhesive stretches and pulls threads (commonly called "gluing"), or the adhesive that stretches after glueing There is a strong tendency that a piece of the adhesive, which is cut and shredded on the cross section of the sheet, remains in the cut surface in a bead shape (commonly called "paste ball"), and there is a problem that the cutting property is deteriorated.

In order to improve only this cuttability, the kind and amount of polar groups in the components constituting the applied pressure-sensitive adhesive component are adjusted, or the glass transition point (Tg) is made high. However, if this is the case, on the contrary, the heat resistance and moisture resistance will decrease, and the original purpose cannot be achieved.

The present invention solves the above-mentioned problems of the prior art and provides a pressure-sensitive adhesive for a polarizing plate or a retardation plate, which is excellent in cuttability without sacrificing performance such as heat resistance and moisture resistance. It was made for the purpose of doing.

[0008]

According to the present invention, "the total molecular weight is in the range of from 400,000 to 2,000,000, two Tg peaks are present, and the difference between both is 70 ° C or higher and the higher Tg is higher. A graft or block copolymer exhibiting a temperature of 50 ° C. or higher, wherein the component of the segment exhibiting a high Tg is one or more selected from the group of styrene, acrylonitrile, methyl methacrylate homopolymers or copolymers, polyesters and polyamides. A pressure-sensitive adhesive for a polarizing plate or a retardation plate, which is characterized in that the molecular weight of the segment is in the range of 500 to 1,000,000 and occupies 5 to 40% by weight of the total weight. It is a summary.

The pressure-sensitive adhesive component in the present invention must be formed from a graft or block copolymer. Graft copolymers or block copolymers tend to exhibit properties that combine the properties of the monomers or prepolymers that make up the copolymer, so the present invention utilizes this property and The object of the present invention is to provide the required adhesive strength, to have the adhesiveness even under severe temperature and humidity conditions, and to hold the required cutting property by other components.

The segment referred to in the present invention refers to a group of monomers, prepolymers, homopolymers or copolymers constituting a copolymer and exhibiting the same behavior. Homopolymers of styrene, acrylonitrile and methyl methacrylate. Alternatively, it comprises one or more components selected from the group of copolymers, polyesters and polyamides.

Further, as a component required to have strong tackiness, that is, heat resistance and moisture resistance, (meth)
Homopolymers or copolymers of acrylic acid ester can be mentioned, and components necessary for providing excellent cleavability include styrene, acrylonitrile, methyl methacrylate and hydroxyethyl methacrylate.
It is a copolymer which is appropriately combined.

The copolymer obtained by such a combination of segments has two Tg peaks. One is a relatively low Tg of -80 to -10 ° C, which is obtained by the components necessary for providing heat resistance and moisture resistance.
And the other one is a relatively high T of 50 to 150 ° C. obtained by the components necessary for providing excellent cutting property.
It is g. In addition, the component exhibiting this high Tg nevertheless has excellent adhesive performance by itself.

Further, it is necessary to prepare the monomer composition during the polymerization so that the difference between the two Tg is 70 ° C. or more. If it is less than 70 ° C., the balance between the cuttability and the adhesive durability is poor. Become. Moreover, the higher Tg is 5
It must show 0 ° C. or higher, and if it is less than 50 ° C., the desired effect on the cutting property cannot be obtained.

The copolymer constituting the pressure-sensitive adhesive of the present invention must have a total molecular weight in the range of from 400,000 to 2,000,000. If it is less than 400,000, it will be foamed in durability, especially in heat resistance. However, the desired effect cannot be obtained against peeling during moisture resistance, and when it exceeds 2 million, whitening of the pressure-sensitive adhesive and coating failure due to high viscosity occur. Further, the molecular weight of the segment exhibiting a high Tg needs to be in the range of 5 to 1 million, and if it is less than 500, the effect of the segment becomes weak, and if it exceeds 1 million, the effect of the segment becomes too strong. ,
The function of the effect of another segment is not expressed. or,
The content of the segment is required to be 5 to 40% by weight of the whole pressure-sensitive adhesive component, and if it is less than 5% by weight, the effect of improving the cuttability is poor, and if it exceeds 40% by weight, it is difficult to develop the adhesiveness. Becomes

The pressure-sensitive adhesive of the present invention comprises a monomer such as acrylic acid and acrylic acid ester, methacrylic acid and methacrylic acid ester, and a macromonomer such as styrene, acrylonitrile and methacrylic acid ester having a vinyl group at the terminal, and the like. , Azobisisobutyronitrile and other polymerization initiators, and in some cases, other functional group-containing monomers are mixed and heated in an organic solvent such as benzene, toluene, xylene, and methyl ethyl ketone, and solution polymerization is performed. It is obtained by doing.

In order to form a polarizing plate or a retardation plate using the above-mentioned pressure-sensitive adhesive, as described above, the pressure-sensitive adhesive is applied onto a carrier made of a release sheet whose surface has been subjected to a release treatment, and is put in a temporarily attached state. It is preferable to adopt a so-called transfer method in which a certain pressure-sensitive adhesive layer is formed, and then this is cut into a required size and pressed and transferred onto a polarizing plate or the like. The polarizing plate thus obtained can be used as a liquid crystal display plate by simply pressing it on the liquid crystal cell surface.

[0017]

The function of the pressure-sensitive adhesive for polarizing plate or retardation plate of the present invention is
A graft or block copolymer having a total molecular weight in the range of from 4 to 2,000,000, having two types of Tg peaks, having a difference of 70 ° C. or more and having a higher Tg of 50 ° C. or more, The segment component is composed of one or more components selected from the group consisting of styrene, acrylonitrile, methyl methacrylate homopolymer or copolymer, polyester, and polyamide, and the segment having a high Tg has a molecular weight of 5 to 1,000,000. Since it is within the range and occupies 5 to 40% by weight of the total weight, it also has characteristics of the copolymerization component constituting the pressure-sensitive adhesive. That is, the excellent tackiness of one component and the high T of the other component.
It also has excellent cutting performance due to g.

[0018]

EXAMPLES Examples of the present invention will be described in detail below.

[0019] Example stirrer, condenser, thermometer, to the polymerization reactor equipped with a nitrogen inlet tube was charged with the following composition, while passing nitrogen gas 6
The temperature was raised to 5 ° C. Butyl acrylate (main component) 90.0 parts by weight Acrylic acid 4.8 parts by weight 2-Hydroxyethyl acrylate 0.2 parts by weight Styrene macromonomer having a vinyl group at the end (molecular weight = about 10,000) 5.0 parts by weight Parts Azobisisobutyronitrile (polymerization initiator) 0.02 parts by weight ethyl acetate (solvent) 100.0 parts by weight

While maintaining the temperature at 65 ° C., the polymerization reaction was continued for 48 hours, and after completion, reprecipitation purification with methanol was carried out to obtain a base polymer. The molecular weight of the copolymer constituting the obtained base polymer was Mn = 350,000, the difference between the two types of Tg was 132 ° C., and the higher Tg was 89 ° C.

This base polymer was blended in the following composition to obtain an adhesive. Base polymer 20.0 parts by weight Coronate L (manufactured by Nitto Polyurethane Company) 0.3 parts by weight 100% aluminum tris (ethylacetonate) 0.5 parts by weight Toluene 80.0 parts by weight

Then, the above adhesive is applied and dried on a carrier obtained by applying a release agent made of silicon on PET having a thickness of 38 μm so that the thickness after drying is 25 μm, and then 150 × It was cut into a size of 150 mm, and was laminated on one surface of a polarizing plate having a thickness of 180 μm and transferred to prepare a polarizing plate with an adhesive layer.

Next, the polarizing plate with the adhesive layer was tested for heat resistance and humidity resistance under the following test conditions.

Heat resistance: left in an environment of 80 ° C. for 500 hours Moisture resistance: left in an environment of 60 ° C., 95% RH for 500 hours As a result of the above-mentioned tests, the phenomenon of foaming of the adhesive layer and the polarizing plate of the adhesive layer No peeling phenomenon was observed.

Next, a cutting test was conducted on the above-prepared polarizing plate with the adhesive layer by the following procedure. That is,
It cut using the super cutter and created 100 pieces of a 10-mm width. As a result, the cut surface was visually observed, but neither glue nor glue balls were observed.

Comparative Example The following composition was charged in the same polymerization reactor as in Example, and 6
The temperature was raised to 5 ° C. Butyl acrylate 94.7 parts by weight Acrylic acid 4.8 parts by weight Acrylic acid 2-hydroxyethyl acrylate 0.3 parts by weight Azobisisobutyronitrile 0.02 parts by weight Ethyl acetate 100.0 parts by weight

Then, an adhesive was obtained in the same manner as in the examples.
The heat resistance and humidity resistance were tested in the same manner as in the examples, but neither the phenomenon of foaming of the adhesive layer nor the phenomenon of peeling from the polarizing plate was observed. However, in the cutting test performed by making 80 pieces using the same cutting machine as in the example, a large number of glues and glue balls were observed, and adhesion of adhesive to the cutting blade was also recognized. It was

[0028]

The polarizing plate or the pressure-sensitive adhesive for retardation plate of the present invention has a total molecular weight in the range of from 400,000 to 2,000,000.
A graft or block copolymer having two kinds of Tg peaks, a difference between both of which is 70 ° C. or higher and a higher Tg of 50 ° C. or higher, wherein the segment component is
It has one or more components selected from the group consisting of styrene, acrylonitrile, a homopolymer or copolymer of methyl methacrylate, polyester and polyamide, and has a high T
Since the molecular weight of the segment showing g is in the range of 5 to 1,000,000 and occupies 5 to 40% by weight in the total weight, it also has the characteristics of the copolymerization component constituting the adhesive. There is. That is, it has both excellent tackiness of one component and excellent cuttability due to high Tg of the other component.

Therefore, a liquid crystal display panel or the like using the same has a long product life and can be adopted in a wider application range.

Claims (1)

[Claims] 1. The overall molecular weight is in the range of 400,000 to 2,000,000, and has two Tg peaks, and the difference between the two is 7
A graft or block copolymer having a higher Tg of 0 ° C. or higher and a higher Tg of 50 ° C. or higher, and the component of the segment having a high Tg is styrene, acrylonitrile,
It is composed of one or more components selected from the group consisting of methyl methacrylate homopolymers or copolymers, polyesters and polyamides, and the segment has a molecular weight of 5 to 10
A pressure-sensitive adhesive for a polarizing plate or a retardation film, which is in the range of 0,000 and occupies 5 to 40% by weight of the total weight.