CN110383121B9

CN110383121B9 - Adhesive layer-attached single-sided protective polarizing film, image display device, and continuous production method therefor

Info

Publication number: CN110383121B9
Application number: CN201880015654.8A
Authority: CN
Inventors: 森本有; 外山雄祐; 藤田雅人
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-03-29
Filing date: 2018-03-23
Publication date: 2023-02-07
Anticipated expiration: 2038-03-23
Also published as: TWI765012B; JP2018169611A; JP6763102B2; CN110383121B; KR20190128627A; JP2020115228A; JP6688822B2; CN110383121A; TW201843274A

Abstract

The invention aims to provide a single-side protective polarizing film with an adhesive layer, which can inhibit defects caused by a nano slit even if a coating layer is not arranged between a polarizer and the adhesive layer. The one-sided protective polarizing film with an adhesive layer of the present invention comprises a one-sided protective polarizing film having a protective film only on one side of a polarizer, and an adhesive layer on the polarizer side of the one-sided protective polarizing film directly or via a coating layer, wherein the adhesive layer has a storage modulus at-40 ℃ of 7.0X 10 ⁷ Pa or above.

Description

Adhesive layer-attached single-sided protective polarizing film, image display device, and continuous production method therefor

Technical Field

The present invention relates to a one-sided protective polarizing film with an adhesive layer, which has a one-sided protective polarizing film provided with a protective film only on one surface of a polarizer and an adhesive layer. The pressure-sensitive adhesive layer-attached single-sided protective polarizing film may be used alone or in the form of an optical film obtained by laminating them to form an image display device such as a Liquid Crystal Display (LCD) or an organic EL display device.

Background

In a liquid crystal display device, it is essential to dispose polarizing films on both sides of a glass substrate forming a surface of a liquid crystal panel in view of an image forming method. As the polarizing film, a polarizing film is generally used in which a protective film is attached to one surface or both surfaces of a polarizer made of a dichroic material such as a polyvinyl alcohol-based film and iodine with a polyvinyl alcohol-based adhesive or the like.

When the polarizing film is bonded to a liquid crystal cell or the like, an adhesive is generally used. In addition, since there are advantages in that the polarizing film can be instantaneously fixed, a drying process for fixing the polarizing film is not required, and the like, the adhesive may be previously provided on one surface of the polarizing film in the form of an adhesive layer. That is, in the lamination of a polarizing film, a one-side protective polarizing film with an adhesive layer is generally used.

Further, in a polarizing film or a single-sided protective polarizing film with an adhesive layer, there is a problem that cracks (through cracks) are easily generated in the entire absorption axis direction of a polarizer due to a change in shrinkage stress of the polarizer in a severe environment of thermal shock (for example, a thermal shock test in which temperature conditions of-30 ℃ and 80 ℃ are repeated, a test at a high temperature of 100 ℃). That is, the one-side protective polarizing film with an adhesive layer has insufficient durability against thermal shock in the above-mentioned severe environment. In particular, the above-described durability against thermal shock is insufficient for a single-sided protective polarizing film with an adhesive layer using a single-sided protective polarizing film in which a protective film is provided only on one side of a polarizer from the viewpoint of thinning. In addition, the through-crack induced by the thermal shock described above is more easily generated in the case where the size of the polarizing film becomes large.

For example, in order to impart high durability in a high-temperature environment, it has been proposed to use, as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive layer-attached one-side protective polarizing film, a pressure-sensitive adhesive layer having a storage modulus at 23 ℃ of 0.2 to 10MPa and a thickness of 2 μm or more and less than 25 μm (patent document 1). In order to provide excellent durability even in a high-temperature environment, it has been proposed to use, as the pressure-sensitive adhesive layer, an adhesive layer exhibiting a storage modulus of 0.15 to 1MPa in a temperature range of 23 to 80 ℃ in a polarizing plate in which a pressure-sensitive adhesive layer is provided on one surface of a polarizer and a protective layer made of a transparent resin film is provided on the other surface of the polarizer (patent document 2). In order to suppress the occurrence of the through crack, it has been proposed to use, as the pressure-sensitive adhesive layer of the one-side protective polarizing film with a pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer in which the shrinkage force in the direction perpendicular to the absorption axis of the polarizer is controlled to be small and the storage modulus of the pressure-sensitive adhesive layer at 23 ℃ is 0.20MPa or more (patent document 3). Further, a thin polarizer is also used, and for example, a thin polarizer which exhibits high orientation by controlling optical characteristics such as a monomer transmittance and a polarization degree has been proposed (patent document 4).

However, in patent document 1, even if the durability is satisfied, the thickness of the polarizer is as high as 25 μm, and thus the occurrence of through cracks due to the shrinkage stress of the polarizer cannot be prevented. Further, patent documents 1 to 3 have a problem of improving the durability of the one-side protective polarizing film with an adhesive layer, and thus boric acid is used in a polarizer in a relatively large amount. It is also known that: when the amount of boric acid contained in the polarizer is more than a specific value, crosslinking is promoted by boric acid during heating, and the shrinkage stress of the polarizer increases, which is not preferable from the viewpoint of suppressing the occurrence of through cracks. That is, in patent documents 1 to 3, although the occurrence of through cracks can be prevented to some extent by controlling the storage modulus of the pressure-sensitive adhesive layer, it cannot be said that the occurrence of through cracks can be sufficiently suppressed.

On the other hand, the polarizer is also thinned. In the case of a polarizer used in a one-side protective polarizing film with a thin adhesive layer, the change in the shrinkage stress of the polarizer is small. It is thus understood that if a polarizer having a reduced thickness is produced, the occurrence of the through crack can be suppressed.

However, it is known that, in the pressure-sensitive adhesive layer-attached one-side protective polarizing film in which the occurrence of the through crack is suppressed, when the polarizer is thinned while controlling the optical characteristics as in patent document 4 (for example, when the thickness is set to 12 μm or less), when a mechanical impact is applied to the pressure-sensitive adhesive layer-attached one-side protective polarizing film (including when a load by a convex fold is applied to the polarizer side), an extremely fine slit (hereinafter, also referred to as a nano slit) is locally generated in the absorption axis direction of the polarizer. It is also known that the generation of the nano-slit is not related to the size of the polarizing film. It is also known that the above-described nano-slit does not occur when a double-sided protective polarizing film having protective films on both sides of a polarizer is used. In addition, in the case where a through crack is generated in the polarizer, the stress around the through crack is released, and thus the through crack is not generated adjacently, but it is known that the nano-slits are generated not only individually but also adjacently. It is also known that through cracks have progressivity extending along the absorption axis direction of the polarizer in which the cracks have occurred, but the nano slits do not have such progressivity. It is thus understood that the nano-slit is a new problem that occurs when the polarizer is thinned and the optical characteristics are controlled to a predetermined range in a single-sided protective polarizing film in which the occurrence of through-cracks is suppressed, and is a problem caused by a phenomenon different from the conventionally known through-cracks.

In addition, the nano-slits are extremely fine and thus cannot be detected in a normal environment. Therefore, even if a nano-slit is generated in the polarizer, it is difficult to confirm a defect of the one-side protective polarizing film with an adhesive layer from light leakage only by simple observation. That is, in general, a single-sided protective polarizing film is formed into a long film shape, and defect inspection is performed by automatic optical inspection, but it is difficult to detect a nano-slit as a defect by the defect inspection. It is also known that the defects caused by the nano-slits can be detected by the expansion of the nano-slits in the width direction (for example, the presence or absence of the aforementioned light leakage) when the one-side protective polarizing film with an adhesive layer is bonded to a glass substrate or the like of an image display panel and placed in a heated environment.

Therefore, it is expected that the single-sided protective polarizing film with an adhesive layer using a thin polarizer will suppress not only through cracks but also defects due to nano slits. Further, since the one-side protective polarizing film with an adhesive layer is thinner than a polarizing film having a two-side protective structure with protective films on both sides, the polarizing film is easily bent or broken during handling.

In order to suppress the defects caused by the nano-slits, a technique has been proposed in which a transparent layer (coating layer) is provided between a polarizer of a single-sided protective polarizing film with an adhesive layer and the adhesive layer (patent document 5). By providing the transparent layer, the polarizing film is less likely to be deflected when external stress is applied to the polarizing film, and therefore, the occurrence of nano-slits can be suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2010-44211

Patent document 2: japanese patent laid-open No. 2008-197309

Patent document 3: japanese patent laid-open publication No. 2013-72951

Patent document 4: japanese patent No. 4751481 specification

Patent document 5: japanese patent No. 6077618

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a single-side protective polarizing film with an adhesive layer, which can inhibit defects caused by nano slits even if a coating layer is not arranged between a polarizer and the adhesive layer.

Another object of the present invention is to provide an image display device having the pressure-sensitive adhesive layer-attached one-side protective polarizing film, a continuous production method thereof, and a pressure-sensitive adhesive for one-side protective polarizing films.

Means for solving the problems

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by the following pressure-sensitive adhesive layer-attached one-side protective polarizing film and the like, and have completed the present invention.

That is, the present invention relates to a one-sided protective polarizing film with an adhesive layer, which has a one-sided protective polarizing film having a protective film only on one side of a polarizer and has an adhesive layer directly or via a coating layer on the polarizer side of the one-sided protective polarizing film,

wherein the adhesive layer has a storage modulus of 7.0X 10 at-40 deg.C ⁷ Pa or above.

The present inventors have conducted extensive studies on the relationship between the physical properties of the pressure-sensitive adhesive layer provided on the polarizer side of the single-sided protective polarizing film and the number of nano slits formed, and as a result, have found that the pressure-sensitive adhesive layer is low in the thicknessThe storage modulus of the temperature zone is related to the generation amount of the nano slits. In detail, the storage modulus of the pressure-sensitive adhesive layer is generally higher when external stress is applied to the pressure-sensitive adhesive layer at a high speed than when external stress is applied at a low speed. In addition, the adhesive layer has a higher storage modulus in a low temperature region than in a high temperature region. That is, the storage modulus of the pressure-sensitive adhesive layer when an external stress is applied to the pressure-sensitive adhesive layer at a high speed tends to exhibit the same physical properties as the storage modulus of the pressure-sensitive adhesive layer in a low temperature region (a tendency that the storage modulus becomes high). On the other hand, it is considered that external stress is often applied to the pressure-sensitive adhesive layer-attached one-side protective polarizing film at a high speed when a liquid crystal panel is manufactured or when a liquid crystal display device is used, and it is considered that nano-slits are more likely to be generated when the external stress is applied at a high speed than when the external stress is applied to the pressure-sensitive adhesive layer-attached one-side protective polarizing film at a low speed. Therefore, it is considered to investigate the relationship between the storage modulus of the pressure-sensitive adhesive layer and the number of generated nano slits when external stress is applied to the pressure-sensitive adhesive layer at a high speed, but it is difficult to measure the storage modulus of the pressure-sensitive adhesive layer when external stress is applied to the pressure-sensitive adhesive layer at a high speed. Based on this, it was found that the relationship between the storage modulus of the pressure-sensitive adhesive layer in a low temperature region and the number of generated nano-slits when external stress is applied to the one-side protective polarizing film with the pressure-sensitive adhesive layer at a high speed, which is intended to exhibit the same physical properties as the storage modulus of the pressure-sensitive adhesive layer when external stress is applied to the pressure-sensitive adhesive layer at a high speed, and the storage modulus of the pressure-sensitive adhesive layer in a low temperature region, particularly at-40 ℃. Further, it was found that the storage modulus at-40 ℃ was 7.0X 10 ⁷ The pressure-sensitive adhesive layer having Pa or more is provided on the polarizer side of the single-sided protective polarizing film, and generation of a nano slit can be effectively suppressed even without providing a coating layer. In addition, in the case where a coating layer is provided between the polarizer and the adhesive layer, the occurrence of the nano-slits can be more effectively suppressed by the synergistic effect of the adhesive layer and the coating layer.

In the one-side protective polarizing film with an adhesive layer, the peak of loss modulus of the adhesive layer is preferably-45 ℃ or higher.

In the one-side protective polarizing film with an adhesive layer, the adhesive layer preferably has a storage modulus at 85 ℃ of 5.5 × 10 ⁴ Pa or more and 1.4X 10 ⁵ Pa or less.

In the one-side protective polarizing film with an adhesive layer, it is preferable that the adhesive layer contains a (meth) acrylic polymer as a base polymer, and the (meth) acrylic polymer contains, as a monomer unit:

(meth) acrylic acid alkyl ester (A) having a homopolymer glass transition temperature of less than 0 ℃ in an amount of 50% by weight or more, and

0.1 to 20 wt% of at least one high Tg monomer (B) selected from an alkyl (meth) acrylate (B1) having a homopolymer glass transition temperature of 0 ℃ or higher and a (meth) acryloyl group-containing monomer (B2) having a homopolymer glass transition temperature of 0 ℃ or higher and a heterocycle.

Further, it is preferable that the (meth) acrylic polymer further contains a polar monomer other than the (meth) acryloyl group-containing monomer (b 2), and the polar monomer is at least one selected from the group consisting of a nitrogen-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer.

The nitrogen-containing monomer is preferably a vinyl-based monomer having a lactam ring. Preferably, the vinyl monomer having a lactam ring is a vinylpyrrolidone monomer. Further, it is preferable that the vinylpyrrolidone monomer is N-vinylpyrrolidone.

The (meth) acrylic polymer preferably contains 0.1 to 5% by weight of the nitrogen-containing monomer, preferably 0.01 to 3% by weight of the carboxyl-containing monomer, and preferably 0.01 to 1% by weight of the hydroxyl-containing monomer as a monomer unit.

In the pressure-sensitive adhesive layer-attached one-side protective polarizing film, the thickness of the polarizer is preferably 12 μm or less.

In the pressure-sensitive adhesive layer-attached one-side protective polarizing film, the polarizer preferably contains a polyvinyl alcohol resin, and is configured such that optical properties represented by a monomer transmittance T and a polarization degree P satisfy the following conditions:

P＞－(10 ^0.929T-42.4 -1) x 100 (wherein T < 42.3), or

P is more than or equal to 99.9 (wherein, T is more than or equal to 42.3).

In the one-side protective polarizing film with an adhesive layer, it is preferable that the polarizer contains boric acid in an amount of 25 wt% or less with respect to the total amount of polarizers.

In addition, a separator may be provided on the pressure-sensitive adhesive layer of the above-described one-side protective polarizing film with a pressure-sensitive adhesive layer. The adhesive layer-equipped single-sided protective polarizing film provided with a separator may be used in the form of a roll.

The present invention also relates to an image display device having the above-described one-side protective polarizing film with an adhesive layer.

Further, the present invention relates to a method for continuously manufacturing an image display device, the method including the steps of: the pressure-sensitive adhesive layer-attached one-side protective polarizing film continuously fed from the roll of pressure-sensitive adhesive layer-attached one-side protective polarizing film and conveyed by the separator is continuously bonded to the surface of the image display panel via the pressure-sensitive adhesive layer.

The present invention also relates to an adhesive for forming an adhesive layer on the polarizer side of a one-sided protective polarizing film having a protective film on only one side of the polarizer,

the adhesive contains at least a (meth) acrylic polymer containing, as a monomer unit two:

In the pressure-sensitive adhesive, the (meth) acrylic polymer preferably further contains a polar monomer other than the (meth) acryloyl group-containing monomer (b 2), and the polar monomer is at least one selected from the group consisting of a nitrogen-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer.

Preferably, the nitrogen-containing monomer is a vinyl monomer having a lactam ring. Preferably, the vinyl monomer having a lactam ring is a vinylpyrrolidone monomer. Further, it is preferable that the vinyl pyrrolidone monomer is N-vinyl pyrrolidone.

In the pressure-sensitive adhesive, the (meth) acrylic polymer preferably contains 0.1 to 5% by weight of the nitrogen-containing monomer, preferably 0.01 to 3% by weight of the carboxyl-containing monomer, and preferably 0.01 to 1% by weight of the hydroxyl-containing monomer as a monomer unit.

ADVANTAGEOUS EFFECTS OF INVENTION

The one-sided protective polarizing film with an adhesive layer of the present invention has a storage modulus at-40 ℃ of 7.0X 10 as provided on the polarizer side of the one-sided protective polarizing film ⁷ Pa or more, and the pressure-sensitive adhesive layer has high elastic properties (high storage modulus in a low temperature region) when an external stress is applied at a high speed, and therefore, the polarizing film is less likely to be deflected when a mechanical impact is applied at a high speed to the polarizing film. As a result, the generation of the nano-slits can be effectively suppressed even without providing the coating layer. In addition, since the one-side protective polarizing film with an adhesive layer of the present invention can omit a step of providing a coating layer, productivity can be improved as compared with a conventional method of providing a coating layer.

Drawings

FIG. 1 is an example of a schematic cross-sectional view of a single-sided protective polarizing film with an adhesive layer according to the present invention.

Fig. 2 is an example of a schematic diagram for comparing a nano-slit and a through-crack generated by a polarizer.

Fig. 3 is a schematic diagram illustrating evaluation items relating to the nano slits of the examples and comparative examples.

Fig. 4 is an example of a photograph showing cracks initiated by the nano-slits involved in the evaluation of the examples and comparative examples.

Fig. 5 is an example of a schematic cross-sectional view of a continuous manufacturing system for an image display device.

Description of the symbols

1. Polarizer

2. Protective film

3. Adhesive layer and the like

4. Adhesive layer

5.5 a, 5b diaphragm

6. 6a, 6b surface protective film

10. Single-sided protective polarizing films

11. Single-sided protective polarizing film with adhesive layer

20a, 20b Single-sided protective polarizing film roll with adhesive layer

21a, 21b Single-sided protective polarizing film with adhesive layer (with surface protective film)

100. Continuous manufacturing system for image display device

101a, 101b polarization film supply unit

151a, 151b continuous discharge portion

152a, 152b cutting part

153a, 153b peeling part

154a, 154b winding part

201a, 201b bonding portion

300. Arrangement replacement part

P image display panel

Conveying part of X image display panel

Detailed Description

Hereinafter, the pressure-sensitive adhesive layer-equipped single-sided protective polarizing film of the present invention will be described with reference to fig. 1. The pressure-sensitive adhesive layer-equipped single-sided protective polarizing film 11 of the present invention includes, for example, a single-sided protective polarizing film 10 and a pressure-sensitive adhesive layer 4. As shown in fig. 1, the one-side protective polarizing film 10 has a protective film 2 only on one side of a polarizer 1. The polarizer 1 and the protective film 2 are laminated via an adhesive layer 3 (and an interlayer such as an adhesive layer and an undercoat layer). Although not shown, the one-side protective polarizing film 10 may be formed with an easy-adhesion layer on the protective film 2, or may be formed by activating the protective film 2 and then laminating the easy-adhesion layer and an adhesive layer. Further, although not shown, a plurality of protective films 2 may be provided. The plurality of protective films 2 may be laminated via an adhesive layer 3 (and an interlayer such as an adhesive layer or an undercoat layer).

As shown in fig. 1, the pressure-sensitive adhesive layer 4 of the pressure-sensitive adhesive layer-attached one-side protective polarizing film 11 of the present invention is provided on the polarizer 1 side of the one-side protective polarizing film 10. Further, although not shown, an application layer may be provided between the polarizer 1 and the adhesive layer 4. The coating layer is not particularly limited, and a known transparent layer described in, for example, japanese patent No. 6077618 can be used. The separator 5 may be provided on the pressure-sensitive adhesive layer 4 of the pressure-sensitive adhesive layer-attached one-side protective polarizing film 11 of the present invention, and the surface protective film 6 may be provided on the opposite side. In the adhesive layer-attached one-side protective polarizing film 11 of fig. 1, a case where both the separator 5 and the surface protective film 6 are provided is shown. The one-side protective polarizing film with an adhesive layer 11 having at least the separator 5 (further, the polarizing film with the surface protective film 6) may be used in the form of a roll, and as described later, for example, a mode (hereinafter, also referred to as a "roll-to-panel mode") in which the one-side protective polarizing film with an adhesive layer 11 continuously fed out from the roll and conveyed by the separator 5 is applied to the surface of the image display panel via the adhesive layer 4 is advantageous in the typical case of referring to japanese patent No. 4406043. From the viewpoints of suppressing the warping of the display panel after bonding, suppressing the generation of nano slits, and the like, the pressure-sensitive adhesive layer-attached single-side protective polarizing film described in fig. 1 is preferably used.

Fig. 2 is a schematic diagram comparing a nanoslit a and a through crack b generated at a polarizer. Fig. 2 (a) shows a nanoslit a produced on the polarizer 1, and fig. 2 (B) shows a through crack B produced on the polarizer 1. The nano-slits a are generated due to mechanical impact, and the nano-slits a locally generated in the absorption axis direction of the polarizer 1 cannot be confirmed at the time of initial generation, but can be confirmed based on expansion in the width direction in a thermal environment (e.g., 80 ℃ or 60 ℃, 90%RH). On the other hand, the nanoslit a is not considered to have a progressivity extending in the absorption axis direction of the polarizer. The generation of the nano-slit a is not related to the size of the polarizing film. The nano-slits a are not only individually generated but also adjacently generated in some cases. On the other hand, the through crack b is generated by thermal shock (e.g., thermal shock test). The through crack has a progressivity extending in the absorption axis direction of the polarizer in which the crack has occurred. When the through crack b is generated, the stress around the through crack b is released, and thus the through crack is not generated adjacently.

< polarizer >

In the present invention, the thickness of the polarizer is preferably 12 μm or less, more preferably 10 μm or less, still more preferably 8 μm or less, yet more preferably 7 μm or less, and particularly preferably 6 μm or less, from the viewpoint of reducing the thickness and suppressing the occurrence of through cracks. On the other hand, the thickness of the polarizer is preferably 1 μm or more. Such a thin polarizer has excellent durability against thermal shock because of small thickness unevenness, excellent visibility, and small dimensional change.

As the polarizer, a polarizer using a polyvinyl alcohol resin can be used. Examples of the polarizer include films obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene-vinyl acetate copolymer partially saponified films, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride desalted products, and the like. Among these, a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine is preferable.

The polarizer obtained by uniaxially stretching a polyvinyl alcohol film dyed with iodine can be produced by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous iodine solution and stretching it to 3 to 7 times the original length. If necessary, boric acid, zinc sulfate, zinc chloride, or the like may be contained, and the film may be immersed in an aqueous solution of potassium iodide or the like. Further, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing, if necessary. By washing the polyvinyl alcohol film with water, dirt and an anti-blocking agent on the surface of the polyvinyl alcohol film can be washed off, and the polyvinyl alcohol film can be swollen to prevent unevenness such as uneven dyeing. The stretching may be performed after the dyeing with iodine, or may be performed while dyeing, or may be performed after the stretching with iodine. Stretching may also be carried out in an aqueous solution or water bath of boric acid, potassium iodide, or the like.

The polarizer preferably contains boric acid from the viewpoint of tensile stability and optical durability. In addition, from the viewpoint of suppressing the occurrence of through cracks and nano slits and suppressing the expansion, the content of boric acid contained in the polarizer is preferably 25 wt% or less, more preferably 20 wt% or less, further preferably 18 wt% or less, and further preferably 16 wt% or less with respect to the total amount of the polarizer. When the boric acid content in the polarizer exceeds 25 wt%, even when the thickness of the polarizer is reduced (for example, 12 μm or less), the shrinkage stress of the polarizer is likely to increase and through cracks are likely to occur, which is not preferable. On the other hand, the boric acid content relative to the total amount of the polarizers is preferably 10% by weight or more, more preferably 12% by weight or more, from the viewpoint of the tensile stability and optical durability of the polarizers.

Typical examples of the thin polarizers include thin polarizers described in japanese patent No. 4751486, japanese patent No. 4751481, japanese patent No. 4815544, japanese patent No. 5048120, japanese patent No. 5587517, international publication No. 2014/077599, and international publication No. 2014/077636, and thin polarizers obtained by the production methods described in these documents.

Preferably, the polarizer is configured such that optical characteristics represented by a single transmittance T and a polarization degree P satisfy the following conditions:

P＞－(10 ^0.929T-42.4 -1) x 100 (wherein T < 42.3), or

P is more than or equal to 99.9 (wherein, T is more than or equal to 42.3).

A polarizer configured to satisfy the above conditions mainly has performance required as a display for a liquid crystal television using a large display element. Specifically, the contrast is 1000 ² The above. For another application, for example, the adhesive sheet can be bonded to the visible side of an organic EL display device.

On the other hand, since the polarizer configured to satisfy the above conditions exhibits a high orientation property, the polarizer is combined with a thin polarizer (for example, 12 μm or less in thickness) and the tensile breaking stress in the direction perpendicular to the absorption axis direction of the polarizer is significantly reduced. As a result, for example, when the polarizing film is exposed to a mechanical impact exceeding the tensile breaking stress in the production process thereof, the nano-slit is highly likely to be generated in the absorption axis direction of the polarizer. Therefore, the present invention is particularly suitable for a single-sided protective polarizing film using the polarizer (or a single-sided protective polarizing film with an adhesive layer using the polarizer).

As the thin polarizer, among the methods of manufacturing a laminate including a step of stretching and a step of dyeing, a thin polarizer obtained by a method of manufacturing a laminate including a step of stretching in an aqueous solution of boric acid as described in japanese patent No. 4751486, japanese patent No. 4751481, and japanese patent No. 4815544 is preferably used from the viewpoint of improving polarization performance by stretching to a high magnification, and particularly preferably a thin polarizer obtained by a method of manufacturing a laminate including a step of performing stretching in an auxiliary gas atmosphere before stretching in an aqueous solution of boric acid as described in japanese patent No. 5147481 and japanese patent No. 4815544. These thin polarizers can be obtained by a production method including a step of stretching a polyvinyl alcohol resin (hereinafter, also referred to as PVA-based resin) layer and a resin base material for stretching in a laminated state, and a step of dyeing. With this production method, even if the PVA-based resin layer is thin, it can be stretched without causing troubles such as breakage due to stretching by being supported by the stretching resin base material.

< protective film >

The material constituting the protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Examples thereof include: polyester polymers such AS polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such AS cellulose diacetate and cellulose triacetate, acrylic polymers such AS polymethyl methacrylate, styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin), and polycarbonate polymers. Examples of the polymer forming the protective film include: examples of the polymer include polyolefin polymers such as polyethylene, polypropylene, cyclic polyolefins having a norbornene structure, and ethylene-propylene copolymers, amide polymers such as vinyl chloride polymers, nylon and aromatic polyamides, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, aromatic ester polymers, polyoxymethylene polymers, epoxy polymers, and blends of the above polymers.

The protective film may contain 1 or more kinds of any appropriate additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the protective film is 50 wt% or less, there is a possibility that high transparency inherent in the thermoplastic resin cannot be sufficiently exhibited.

As the protective film, a retardation film, a brightness enhancement film, a diffusion film, or the like can be used. Examples of the retardation film include a retardation film having a front retardation of 40nm or more and/or a thickness direction retardation of 80nm or more. The front retardation is usually controlled to be in the range of 40 to 200nm, and the thickness direction retardation is usually controlled to be in the range of 80 to 300 nm. When the retardation film is used as the protective film, the retardation film also functions as a polarizer protective film, and therefore, the thickness can be reduced.

Examples of the retardation film include a birefringent film obtained by uniaxially stretching or biaxially stretching a thermoplastic resin film. The temperature and stretch ratio of the stretching can be appropriately set depending on the retardation value, the material and thickness of the film.

The thickness of the protective film may be appropriately determined, but is usually about 1 to 500 μm in view of strength, workability such as handling, and thin layer property. Preferably 1 to 300. Mu.m, more preferably 5 to 200. Mu.m, still more preferably 5 to 150. Mu.m, and particularly preferably 5 to 80 μm.

A functional layer such as a hard coat layer, an antireflection layer, an adhesion prevention layer, a diffusion layer, or an antiglare layer may be provided on the surface of the protective film that is not bonded to the polarizer. The functional layers such as the hard coat layer, the antireflection layer, the adhesion prevention layer, the diffusion layer, and the antiglare layer may be provided as the protective film itself, or may be provided separately from the protective film.

< interlayer >

The protective film and the polarizer may be laminated with an adhesive layer, an undercoat layer (primer layer), or the like interposed therebetween. In this case, it is preferable to stack both layers without an air gap by using an interlayer. The protective film and the polarizer are preferably laminated via an adhesive layer.

The adhesive layer may be formed using an adhesive. The type of the adhesive is not particularly limited, and various adhesives can be used. The adhesive layer is not particularly limited as long as it is an optically transparent layer, and various types of adhesives such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives can be used as the adhesive, but water-based adhesives or active energy ray-curable adhesives are preferable.

Examples of the aqueous adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and aqueous polyesters. The aqueous adhesive is generally used in the form of an adhesive formed from an aqueous solution, and usually contains 0.5 to 60% by weight of a solid content.

The active energy ray-curable adhesive is an adhesive that is cured by an active energy ray such as an electron beam or ultraviolet ray (radical-curable type or cation-curable type), and can be used in the form of, for example, an electron beam-curable type or an ultraviolet-curable type. As the active energy ray-curable adhesive, for example, a radical photo-curable adhesive can be used. When a radical photo-curable active energy ray-curable adhesive is used as the ultraviolet-curable adhesive, the adhesive contains a radical polymerizable compound and a photopolymerization initiator.

The application method of the adhesive can be appropriately selected depending on the viscosity of the adhesive and the target thickness. Examples of the coating method include: reverse coaters, gravure coaters (direct, reverse, or offset), bar reverse coaters, roll coaters, die coaters, wire wound bar coaters, and the like. The coating may be performed by a dipping method or the like.

When an aqueous adhesive or the like is used, the adhesive layer is preferably applied so that the thickness of the adhesive layer to be finally formed is 30 to 300 nm. The thickness of the adhesive layer is more preferably 60 to 250nm. On the other hand, when an active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably set to 0.1 to 200 μm. More preferably 0.5 to 50 μm, and still more preferably 0.5 to 10 μm.

In the case of laminating the polarizer and the protective film, an easy adhesion layer may be provided between the protective film and the adhesive layer. The easy-adhesion layer can be formed using various resins having, for example, a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, silicones, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins may be used alone in 1 kind, or in combination of 2 or more kinds. In addition, other additives may be added to the formation of the easy adhesion layer. Specifically, a thickener, an ultraviolet absorber, an antioxidant, a stabilizer such as a heat stabilizer, and the like can be further used.

Generally, an easy-adhesion layer is provided on a protective film in advance, and the easy-adhesion layer side of the protective film is laminated with a polarizer via an adhesive layer. The easy adhesion layer can be formed by applying a material for forming the easy adhesion layer to the protective film by a known technique and drying the applied material. The material for forming the easy-adhesion layer is usually prepared as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of coating, and the like. The thickness of the easy-adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. In this case, the easy adhesion layer is preferably formed to have a total thickness within the above range.

The adhesive layer is formed of an adhesive. As the binder, various binders can be used, and examples thereof include: rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl pyrrolidone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, and the like. The adhesive base polymer can be selected corresponding to the kind of the above-mentioned adhesive. Among the above-mentioned pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are preferably used because they are excellent in optical transparency, exhibit adhesive properties such as suitable wettability, cohesiveness and adhesiveness, and are excellent in weather resistance, heat resistance and the like.

The undercoat layer (undercoat layer) is formed to improve adhesion between the polarizer and the protective film. The material constituting the undercoat layer is not particularly limited as long as it exerts a certain degree of strong adhesion to both the base film and the polyvinyl alcohol resin layer. For example, a thermoplastic resin or the like excellent in transparency, thermal stability, stretchability, and the like can be used. Examples of the thermoplastic resin include: acrylic resin, polyolefin resin, polyester resin, polyvinyl alcohol resin, or a mixture thereof.

< adhesive layer >

The adhesive layer in the one-sided protective polarizing film with an adhesive layer of the present invention has a storage modulus at-40 ℃ of 7.0X 10 as described above ⁷ Pa or above. From the viewpoint of more effectively suppressing the generation of the nano-slits, the storage modulus of the pressure-sensitive adhesive layer at-40 ℃ is preferably 8.0 × 10 ⁷ Pa or more, more preferably 1.0X 10 ⁸ Pa or above. On the other hand, the storage modulus of the pressure-sensitive adhesive layer at-40 ℃ is preferably 1.0X 10 from the viewpoint of preventing peeling when dropped at low temperatures ¹⁰ Pa or less.

In addition, the pressure-sensitive adhesive layer preferably has a loss modulus peak of-45 ℃ or higher, more preferably-40 ℃ or higher, and even more preferably-35 ℃ or higher, from the viewpoints of imparting high elastic properties when external stress is applied at high speed, making the polarizing film less likely to deflect, and more effectively suppressing the generation of nano-slits. On the other hand, the peak of the loss modulus of the pressure-sensitive adhesive layer is usually 0 ℃ or less from the viewpoint of preventing the pressure-sensitive adhesive layer from exhibiting no tackiness and being unusable as the pressure-sensitive adhesive layer.

When a liquid crystal display device is used in the production of a liquid crystal panel, external stress may be applied to the one-side protective polarizing film with an adhesive layer at a low speed, and it is preferable that the occurrence of a nano-slit can be suppressed. The present inventors have studied the relationship between the storage modulus in the high-temperature region of the pressure-sensitive adhesive layer and the number of generated nano slits from the same viewpoint as the relationship between the storage modulus in the low-temperature region of the pressure-sensitive adhesive layer and the number of generated nano slits described above, and as a result, have found that the storage modulus of the pressure-sensitive adhesive layer in the high-temperature region, particularly at 85 ℃, is related to the number of generated nano slits when external stress is applied to the one-side protective polarizing film with the pressure-sensitive adhesive layer at a low speed. Further, it was found that the storage modulus at 85 ℃ of the adhesive layer was 5.5X 10 ⁴ Pa or more, it is also possible to suppress the occurrence of the nano-slit when external stress is applied to the one-side protective polarizing film with the pressure-sensitive adhesive layer at a low speed. From the viewpoint of further suppressing the nano-slits, the storage modulus of the pressure-sensitive adhesive layer at 85 ℃ is preferably 6.0 × 10 ⁴ Pa or more, more preferably 7.0X 10 ⁴ Pa or above. On the other hand, if the storage modulus of the pressure-sensitive adhesive layer at 85 ℃ is too high, the pressure-sensitive adhesive layer tends to be easily peeled from the polarizer when the polarizer of the one-side protective polarizing film undergoes a dimensional change due to thermal shrinkage. Therefore, the storage modulus of the adhesive layer at 85 ℃ is preferably 1.4X 10 ⁵ Pa or less, more preferably 1.3X 10 ⁵ Pa or less.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100. Mu.m, preferably about 2 to 50 μm, more preferably about 2 to 40 μm, and still more preferably about 5 to 35 μm.

When the pressure-sensitive adhesive layer is formed, a suitable pressure-sensitive adhesive can be used, and the type thereof is not particularly limited. Examples of the binder include: rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl pyrrolidone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, and the like.

Among these pressure-sensitive adhesives, those excellent in optical transparency, exhibiting suitable adhesive properties such as wettability, cohesiveness and adhesiveness, and also excellent in weather resistance, heat resistance and the like can be preferably used. As the adhesive exhibiting such characteristics, an acrylic adhesive can be preferably used. Hereinafter, a case where an acrylic pressure-sensitive adhesive is used as a material for forming the pressure-sensitive adhesive layer will be described.

As the acrylic pressure-sensitive adhesive, a pressure-sensitive adhesive containing, as a base polymer, a (meth) acrylic polymer having a monomer unit of an alkyl (meth) acrylate as a main skeleton can be used. The term (meth) acrylate refers to acrylate and/or methacrylate, and has the same meaning as (meth) acrylate in the present invention.

The alkyl group of the alkyl (meth) acrylate constituting the main skeleton of the (meth) acrylic polymer has about 1 to 18 carbon atoms, and specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and stearyl (meth) acrylate, and they may be used alone or in combination.

In order to obtain an adhesive layer having peaks of the storage modulus and the loss modulus, the (meth) acrylic polymer preferably contains, as a monomer unit:

50% by weight or more (more preferably 60% by weight or more, further preferably 70% by weight or more, and further preferably 80% by weight or more) of an alkyl (meth) acrylate (a) having a glass transition temperature of a homopolymer of less than 0 ℃ (more preferably-20 ℃ or less, and further preferably-40 ℃ or less); and

0.1 to 20 wt% (more preferably 1 to 15 wt%, further preferably 2.5 to 10 wt%, further preferably 4 wt% or more and less than 10 wt%) of at least one high Tg monomer (B) selected from an alkyl (meth) acrylate (B1) in which the homopolymer has a glass transition temperature of 0 ℃ or more (more preferably 20 ℃ or more, further preferably 40 ℃ or more) and the heterocyclic ring-containing (meth) acryloyl monomer (B2). When the alkyl (meth) acrylate (b 1) and the (meth) acryloyl group-containing monomer (b 2) are used in combination, the total weight% is defined as the total weight%.

Examples of the alkyl (meth) acrylate (a) include: ethyl acrylate (Tg: -24 ℃ C.), n-butyl acrylate (Tg: -50 ℃ C.), n-pentyl methacrylate (Tg: -5 ℃ C.), n-hexyl acrylate (Tg: -57 ℃ C.), n-hexyl methacrylate (Tg: -5 ℃ C.), n-octyl acrylate (Tg: -65 ℃ C.), n-octyl methacrylate (Tg: -20 ℃ C.), n-nonyl acrylate (Tg: -58 ℃ C.), n-lauryl acrylate (Tg: -3 ℃ C.), n-lauryl methacrylate (Tg: -65 ℃ C.), n-tetradecyl methacrylate (Tg: -72 ℃ C.), isopropyl acrylate (Tg: -3 ℃ C.), isobutyl acrylate (Tg: -40 ℃ C.), isooctyl acrylate (Tg: -58 ℃ C.), isooctyl methacrylate (Tg: -45 ℃ C.), 2-ethylhexyl acrylate (Tg-70 ℃ C.), 2-ethylhexyl methacrylate (Tg: -10 ℃ C.), and the like. They may be used alone or in combination. Of these, at least one selected from the group consisting of ethyl acrylate, n-butyl acrylate, n-pentyl methacrylate, n-hexyl acrylate, and 2-ethylhexyl acrylate is preferably used, and n-butyl acrylate is more preferably used. The Tg (glass transition temperature) in each bracket is the Tg of a homopolymer obtained by polymerizing each monomer. The same applies to the following description.

Examples of the alkyl (meth) acrylate (b 1) include: linear alkyl (meth) acrylates such as methyl acrylate (Tg: 8 ℃ C.), methyl methacrylate (Tg: 105 ℃ C.), ethyl methacrylate (Tg: 65 ℃ C.), n-propyl acrylate (Tg: 3 ℃ C.), n-propyl methacrylate (Tg: 35 ℃ C.), n-pentyl acrylate (Tg: 22 ℃ C.), n-tetradecyl acrylate (Tg: 24 ℃ C.), n-hexadecyl acrylate (Tg: 35 ℃ C.), n-hexadecyl methacrylate (Tg: 15 ℃ C.), n-stearyl acrylate (Tg: 30 ℃ C.), and n-stearyl methacrylate (Tg: 38 ℃ C.); branched alkyl (meth) acrylates such as t-butyl acrylate (Tg: 43 ℃ C.), t-butyl methacrylate (Tg: 48 ℃ C.), isopropyl methacrylate (Tg: 81 ℃ C.), and isobutyl methacrylate (Tg: 48 ℃ C.); and cyclic alkyl (meth) acrylates such as cyclohexyl acrylate (Tg: 19 ℃ C.), cyclohexyl methacrylate (Tg: 65 ℃ C.), isobornyl acrylate (Tg: 94 ℃ C.), isobornyl methacrylate (Tg: 180 ℃ C.), and the like. They may be used alone or in combination. Among these, at least one selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl methacrylate, isobornyl acrylate, and isobornyl methacrylate is preferably used, and at least one selected from the group consisting of methyl acrylate, methyl methacrylate, and isobornyl acrylate is more preferably used.

The (meth) acryloyl group-containing monomer (b 2) has a heterocyclic ring. The heterocyclic ring is not particularly limited, and examples thereof include: aliphatic hetero rings such as aziridine ring, azetidine ring, pyrrolidine ring, piperidine ring, piperazine ring and morpholine ringA ring, a pyrrole ring, an imidazole ring, a pyrazole ring,

Azolyl ring, iso

Heteroaromatic rings such as an azole ring, a thiazole ring, an isothiazole ring, a pyridine ring, a pyrimidine ring, a pyridazine ring and a pyrazine ring. The heterocyclic ring may be directly bonded to the (meth) acryloyl group or may be bonded to the (meth) acryloyl group via a linking group. Among these, aliphatic heterocyclic rings are preferable, and morpholine rings are more preferable. Examples of the (meth) acryloyl group-containing monomer (b 2) include N-acryloyl morpholine (Tg: 145 ℃ C.). They may be used alone or in combination. Of these, N-acryloylmorpholine is particularly preferably used.

For the purpose of improving adhesiveness, heat resistance, and the like, one or more of various monomers may be introduced into the (meth) acrylic polymer by copolymerization. Specific examples of such a comonomer (except for the (meth) acryloyl group-containing monomer (b 2)) include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, a nitrogen-containing monomer, and an aromatic group-containing monomer.

Examples of the carboxyl group-containing monomer include: acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and the like. They may be used alone or in combination.

As the hydroxyl group-containing monomer, there may be mentioned: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxydodecyl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl acrylate. They may be used alone or in combination.

Examples of the nitrogen-containing monomer include: vinyl monomers having a lactam ring (e.g., vinyl pyrrolidone monomers such as N-vinyl pyrrolidone and methyl vinyl pyrrolidone), and vinyl monomers having a lactam ringVinyl lactam monomers having a lactam ring such as a β -lactam ring, a δ -lactam ring and an e-lactam ring); maleimide monomers such as maleimide, N-cyclohexylmaleimide and N-phenylmaleimide; (N-substituted) amide monomers such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, and N-methylol propane (meth) acrylamide; aminoalkyl (meth) acrylate monomers such as aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and 3- (3-pyridyl) propyl (meth) acrylate; succinimide monomers such as N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, and N- (meth) acryloyl-8-oxyoctamethylene succinimide; cyano (meth) acrylate monomers such as acrylonitrile and methacrylonitrile; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinylpyridine

Oxazole, vinyl morpholine, N-vinyl carboxylic acid amides, and the like. They may be used alone or in combination.

Examples of the aromatic group-containing monomer include: benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like. They may be used alone or in combination.

In addition to the above monomers, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, (meth) sulfopropyl acrylate, and (meth) acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate, and the like. They may be used alone or in combination.

It is also possible to use: vinyl monomers such as vinyl acetate, vinyl propionate, styrene, alpha-methylstyrene and N-vinylcaprolactam; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; polyethylene glycol acrylate monomers such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate; acrylic ester monomers such as tetrahydrofurfuryl (meth) acrylate, fluorine-containing (meth) acrylate, silicone (meth) acrylate, and 2-methoxyethyl acrylate. They may be used alone or in combination.

From the viewpoint of improving the cohesive force of the (meth) acrylic polymer and more effectively suppressing the generation of the nano-slits, it is preferable to introduce at least one polar monomer selected from the group consisting of the carboxyl group-containing monomer, the hydroxyl group-containing monomer, and the nitrogen-containing monomer (excluding the (meth) acryloyl group-containing monomer (b 2)) into the (meth) acrylic polymer by copolymerization, and it is more preferable to introduce the carboxyl group-containing monomer, the hydroxyl group-containing monomer, and the nitrogen-containing monomer into the (meth) acrylic polymer by copolymerization. As the carboxyl group-containing monomer, (meth) acrylic acid is preferable. The hydroxyl group-containing monomer is preferably at least 1 member selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. The nitrogen-containing monomer is preferably a vinyl-based monomer having a lactam ring, more preferably the vinylpyrrolidone-based monomer, and still more preferably N-vinylpyrrolidone. By introducing the nitrogen-containing monomer into the (meth) acrylic polymer by copolymerization, the occurrence of nano-slits can be more effectively suppressed, and the durability (peeling resistance) of the pressure-sensitive adhesive layer at high temperature and/or high humidity can be improved.

The (meth) acrylic polymer preferably contains the carboxyl group-containing monomer in an amount of 0.01 to 3 wt%, more preferably 0.05 to 1 wt%, and still more preferably 0.1 to 0.5 wt% as a monomer unit.

The (meth) acrylic polymer preferably contains the hydroxyl group-containing monomer in an amount of 0.01 to 1% by weight, more preferably 0.05 to 1% by weight, and still more preferably 0.1 to 0.5% by weight as a monomer unit.

The (meth) acrylic polymer preferably contains the nitrogen-containing monomer as a monomer unit in an amount of 0.1 to 5% by weight, more preferably 0.5 to 3% by weight, and still more preferably 1.5 to 3% by weight.

The average molecular weight of the (meth) acrylic polymer is not particularly limited, and is preferably about 50 to 250 ten thousand. The (meth) acrylic polymer can be produced by various known methods, and for example, radical polymerization such as bulk polymerization, solution polymerization, suspension polymerization and the like can be appropriately selected. As the radical polymerization initiator, various known initiators such as azo type and peroxide type initiators can be used. The reaction temperature is usually about 50 to 80 ℃ and the reaction time is usually 1 to 8 hours. Among the above production methods, the solution polymerization method is preferred, and ethyl acetate, toluene, and the like are generally used as a solvent for the (meth) acrylic polymer.

The binder may contain a crosslinking agent. The crosslinking agent improves adhesion and durability, and can achieve reliability at high temperatures and shape retention of the adhesive itself. As the crosslinking agent, isocyanates, epoxies, peroxides, metal chelates, peroxides, etc., can be suitably used,

Oxazolines, and the like. These crosslinking agents may be used in 1 kind or in combination of 2 or more kinds.

Isocyanate compounds can be used as the isocyanate-based crosslinking agent. Examples of the isocyanate compound include isocyanate monomers such as tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate, and adduct-based isocyanate compounds obtained by adding these isocyanate monomers to trimethylolpropane or the like; examples of the isocyanurate and biuret compounds include urethane prepolymer type isocyanates obtained by addition reaction of known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, and the like.

The isocyanate-based crosslinking agent may be used alone or in combination of two or more, and the total content of the isocyanate-based crosslinking agent is preferably 0.01 to 2 parts by weight, more preferably 0.02 to 2 parts by weight, and still more preferably 0.05 to 1.5 parts by weight, based on 100 parts by weight of the base polymer. It may be suitably contained in consideration of cohesive force, resistance to peeling in a durability test, and the like.

Various peroxides are used as the peroxide crosslinking agent. Examples of the peroxide include di (2-ethylhexyl) peroxydicarbonate, di (4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1, 3-tetramethylbutyl peroxyisobutyrate, 1, 3-tetramethylbutyl peroxy2-ethylhexanoate, bis (4-methylbenzoyl) peroxide, dibenzoyl peroxide, and tert-butyl peroxyisobutyrate. Among them, bis (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, and dibenzoyl peroxide, which are excellent in crosslinking reaction efficiency, are particularly preferably used.

The above peroxides may be used singly or in combination of two or more, and the total content of the above peroxides is preferably 0.01 to 2 parts by weight, more preferably 0.04 to 1.5 parts by weight, and still more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the base polymer. Within this range, the processability, reworkability, crosslinking stability, peelability and the like can be suitably selected.

Further, a silane coupling agent may be contained in the binder. By using the silane coupling agent, durability can be improved. As the silane coupling agent, a silane coupling agent having any suitable functional group may be used. Specifically, examples of the functional group include: vinyl, epoxy, amino, mercapto, (meth) acryloyloxy, acetoacetyl, isocyanate, styryl, polysulfide, and the like. Specific examples thereof include: vinyl-containing silane coupling agents such as vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane and vinyltributoxysilane; epoxy group-containing silane coupling agents such as gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane; amino-containing silane coupling agents such as γ -aminopropyltrimethoxysilane, N- β - (aminoethyl) - γ -aminopropylmethyldimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane, γ -triethoxysilyl-N- (1, 3-dimethylbutylidene) propylamine, and N-phenyl- γ -aminopropyltrimethoxysilane; mercapto silane-containing coupling agents such as γ -mercaptopropylmethyldimethoxysilane; styrene-containing silane coupling agents such as p-styryltrimethoxysilane; (meth) acrylic acid-containing silane coupling agents such as gamma-acryloyloxypropyltrimethoxysilane and gamma-methacryloyloxypropyltriethoxysilane; isocyanate-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane; polysulfide-containing silane coupling agents such as bis (triethoxysilylpropyl) tetrasulfide, and the like.

The silane coupling agents may be used alone or in combination of two or more. The total content of the silane coupling agent is preferably 0.001 to 5 parts by weight, more preferably 0.01 to 1 part by weight, even more preferably 0.02 to 1 part by weight, and even more preferably 0.05 to 0.6 part by weight, based on 100 parts by weight of the base polymer.

Further, the binder may contain a rework improving agent from the viewpoint of improving the rework property. The above-mentioned reworking improver is a chemical substance which has a polar group, is likely to interact with a glass interface, and is likely to segregate at the glass interface. Examples of the above-mentioned rework improving agent include: diols having an oxyalkylene group such as EO and PO, oligomers having a perfluoroalkyl group, and polyether compounds having a reactive silyl group. The polyether compound may be, for example, a polyether compound disclosed in jp 2010-275522 a.

Examples of the polyether compound having a reactive silyl group include: MS polymers S203, S303, and S810 manufactured by KANEKA corporation; SILYL EST250, EST280; SAT10, SAT200, SAT220, SAT350, SAT400, EXCESTAR S2410, S2420 or S3430 manufactured by Asahi glass company.

The content of the rework improving agent is preferably 0.001 parts by weight or more, more preferably 0.01 parts by weight or more, further preferably 0.1 parts by weight or more, and further preferably 10 parts by weight or less, more preferably 5 parts by weight or less, further preferably 2 parts by weight or less, and further preferably 1 part by weight or less, relative to 100 parts by weight of the base polymer. When the content of the reworking improver is less than 0.001 parts by weight, the reworkability of the pressure-sensitive adhesive layer is difficult to improve, and when the content is more than 10 parts by weight, the adhesive properties of the pressure-sensitive adhesive layer tend to be lowered.

As a method for forming the pressure-sensitive adhesive layer, the following method can be used: for example, a method in which the pressure-sensitive adhesive is applied to a separator or the like which has been subjected to a peeling treatment, and after a pressure-sensitive adhesive layer is formed by drying and removing a polymerization solvent or the like, the pressure-sensitive adhesive layer is transferred onto the polarizer side (polarizer in the embodiment of fig. 1) of the one-side protective polarizing film; or a method of applying the above adhesive, drying to remove the polymerization solvent and the like, and forming an adhesive layer on the polarizer; and so on. In the case of applying the adhesive, one or more solvents other than the polymerization solvent may be added newly as appropriate.

As the separator subjected to the peeling treatment, a silicone release liner can be preferably used. In the step of forming the pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive of the present invention to such a liner and drying the applied pressure-sensitive adhesive, a suitable method can be appropriately employed according to the purpose as a method for drying the pressure-sensitive adhesive. The method of drying the coating film by heating is preferably used. The heating and drying temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and particularly preferably 70 to 170 ℃. By setting the heating temperature in the above range, an adhesive having excellent adhesive characteristics can be obtained.

The drying time may be suitably employed as appropriate. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

As a method for forming the adhesive layer, various methods can be employed. Specific examples thereof include: roll coating, roll and lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, blade coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, and the like.

When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer can be protected with a sheet (separator) subjected to a peeling treatment until it is actually used.

Examples of the constituent material of the separator include: plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabrics, and suitable sheets such as nets, foamed sheets, metal foils, and laminates thereof, and the like.

The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples thereof include: polyethylene films, polypropylene films, polybutylene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films, and the like.

The thickness of the separator is usually about 5 to 200. Mu.m, preferably about 5 to 100. Mu.m. The separator may be subjected to a mold release and antifouling treatment using a mold release agent such as silicone, fluorine, long-chain alkyl or fatty acid amide, silica powder, or the like, or an antistatic treatment such as a coating type, a mixing type, or a vapor deposition type, as required. In particular, the surface of the separator may be appropriately subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment, thereby further improving the releasability from the pressure-sensitive adhesive layer.

< surface protective film >

A surface protective film may be disposed on the one-side protective polarizing film with the adhesive layer. The surface protective film generally has a base film and an adhesive layer, and protects the polarizer via the adhesive layer.

The base film of the surface protective film may be selected from materials having isotropy or near isotropy from the viewpoints of inspection property, manageability, and the like. Examples of the film material include: transparent polymers such as polyester resins such as polyethylene terephthalate films, cellulose resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Of these, polyester-based resins are preferred. The substrate film may be a laminate of 1 or 2 or more kinds of film materials, or a stretched product of the above film. The thickness of the base film is usually 500 μm or less, preferably 10 to 200. Mu.m.

As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer of the surface protective film, a pressure-sensitive adhesive using a polymer such as a (meth) acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber as a base polymer can be appropriately selected and used. From the viewpoint of transparency, weather resistance, heat resistance and the like, an acrylic adhesive containing an acrylic polymer as a base polymer is preferred. The thickness of the adhesive layer (dry film thickness) may be determined according to the desired adhesive force. Usually about 1 to 100. Mu.m, preferably 5 to 50 μm.

In the surface protective film, a release treated layer may be provided on the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is provided, using a low-adhesion material subjected to a silicone treatment, a long-chain alkyl treatment, a fluorine treatment, or the like.

< other optical layers >

The pressure-sensitive adhesive layer-equipped single-sided protective polarizing film of the present invention can be used in practice as an optical film laminated with other optical layers. The optical layer is not particularly limited, and 1 or 2 or more layers of optical layers, such as a reflective plate, a semi-transmissive plate, a retardation plate (including 1/2 wave plate, 1/4 wave plate, and the like), a viewing angle compensation film, and the like, which are used in the formation of a liquid crystal display device and the like, may be used. In particular, a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a semi-transmissive reflective plate is further laminated on the pressure-sensitive adhesive layer-attached one-side protective polarizing film of the present invention, an elliptical polarizing film or a circular polarizing film in which a phase difference plate is further laminated on the pressure-sensitive adhesive layer-attached one-side protective polarizing film, a wide-angle polarizing film in which a viewing angle compensation film is further laminated on the pressure-sensitive adhesive layer-attached one-side protective polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on the pressure-sensitive adhesive layer-attached one-side protective polarizing film is preferable.

The optical film in which the optical layers are laminated on the pressure-sensitive adhesive layer-attached single-side protective polarizing film may be formed by sequentially laminating the optical layers in the production process of a liquid crystal display device or the like, but when the optical film is laminated in advance to form the optical film, there are advantages in that stability of quality, assembly work, and the like are excellent, and the production process of the liquid crystal display device or the like can be improved. The lamination may be carried out by a suitable bonding means such as an adhesive layer. When the above-mentioned one-side protective polarizing film with an adhesive layer and other optical films are bonded, their optical axes may be set at an appropriate arrangement angle depending on the desired retardation characteristics and the like.

The pressure-sensitive adhesive layer-equipped single-sided protective polarizing film or optical film of the present invention can be preferably used for formation of various image display devices such as liquid crystal display devices and organic EL display devices. The liquid crystal display device can be formed in a conventional manner. That is, the liquid crystal display device can be generally formed by appropriately assembling a liquid crystal cell, a single-sided protective polarizing film or an optical film with a pressure-sensitive adhesive layer, and components such as a lighting system used as needed, and introducing them into a driver circuit, etc., and in the present invention, the liquid crystal display device is not particularly limited except for using the single-sided protective polarizing film or the optical film with a pressure-sensitive adhesive layer of the present invention, and can be formed in a conventional manner. As the liquid crystal cell, any type of liquid crystal cell such as IPS type, VA type, etc. can be used, and IPS type is particularly preferable.

A liquid crystal display device in which a single-sided protective polarizing film or an optical film having a pressure-sensitive adhesive layer is disposed on one side or both sides of a liquid crystal cell, a liquid crystal display device using a backlight or a reflector in an illumination system, or the like can be formed. At this time, the adhesive layer-attached one-side protective polarizing film or optical film of the present invention may be disposed on one side or both sides of the liquid crystal cell. In the case where a single-sided protective polarizing film or optical film with an adhesive layer is provided on both sides, they may be the same material or different materials. Further, in forming a liquid crystal display device, appropriate members such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight may be disposed in appropriate positions in 1 layer or 2 layers or more.

< method for continuously producing image display device >

The above-described image display device is preferably manufactured by a continuous manufacturing method (roll-to-panel) including: the pressure-sensitive adhesive layer-equipped one-side protective polarizing film of the present invention fed continuously from a roll (roll) of the pressure-sensitive adhesive layer-equipped one-side protective polarizing film and conveyed by the separator is continuously bonded to the surface of the image display panel via the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer-attached single-side protective polarizing film of the present invention is a very thin film, and therefore, when a method (also referred to as a "sheet-to-sheet" method ") of cutting (cutting) a single sheet into sheets and attaching the sheets one by one to an image display panel is used, handling at the time of sheet conveyance and attaching the sheets to the display panel is difficult, and in these processes, the risk of the pressure-sensitive adhesive layer-attached single-side protective polarizing film (sheet) being subjected to a large mechanical impact (e.g., deflection due to adsorption) increases. In order to reduce such a risk, it is necessary to take another measure such as using a surface protection film having a substrate film thickness of 50 μm or more. On the other hand, if a roll-to-roll system is used, the pressure-sensitive adhesive layer-attached single-sided protective polarizing film is stably transported from a roll to an image display panel through a continuous separator without being cut (cut into individual sheets) into a sheet shape, and is adhered to the image display panel while maintaining this state. As a result, high-speed continuous production of image display panels in which the occurrence of nano-slits is effectively suppressed can be realized in addition to the relaxation of mechanical impact by the pressure-sensitive adhesive layer controlled such that the film thickness and the storage modulus satisfy the predetermined relational expression.

Fig. 5 is a schematic diagram showing an example of a continuous manufacturing system of a liquid crystal display device using a roll-to-plate (roll-to-plate) method. As shown in fig. 5, a continuous manufacturing system 100 for liquid crystal display devices includes: a series of conveying units X, a 1 st polarizing film supply unit 101a, a 1 st laminating unit 201a, a 2 nd polarizing film supply unit 101b, and a 2 nd laminating unit 201b for conveying the liquid crystal display panel P. As the roll 20a of the 1 st pressure-sensitive adhesive layer-attached one-side protective polarizing film (1 st roll) and the roll 20b of the 2 nd pressure-sensitive adhesive layer-attached one-side protective polarizing film (2 nd roll), rolls of polarizing films having an absorption axis in the longitudinal direction and having the form shown in fig. 1 were used.

(conveying section)

The conveying section X conveys the liquid crystal display panel P. The conveying section X may be configured to include a plurality of conveying rollers, an adsorption plate, and the like. The conveying section X includes an arrangement changing section (for example, by horizontally rotating the liquid crystal display panel P by 90 °) 300 for changing the arrangement relationship between the long side and the short side of the liquid crystal display panel P with respect to the conveying direction of the liquid crystal display panel P between the 1 st bonding section 201a and the 2 nd bonding section 201b. This makes it possible to laminate the 1 st pressure-sensitive adhesive layer-attached one-side protective polarizing film 21a and the 2 nd pressure-sensitive adhesive layer-attached one-side protective polarizing film 21b to the liquid crystal display panel P in a crossed nicols relationship.

(No. 1 polarizing film supply section)

The 1 st polarizing film supply section 101a continuously supplies the 1 st pressure-sensitive adhesive layer-attached single-sided protective polarizing film (with surface protective film) 21a continuously fed from the 1 st roll 20a and conveyed by the separator 5a to the 1 st laminating section 201a. The 1 st polarizing film supply part 101a has: a 1 st continuous feeding section 151a, a 1 st cutting section 152a, a 1 st peeling section 153a, a 1 st winding section 154a, and energy storage sections such as a plurality of transport roller sections and dancer rollers (dancer rollers).

The 1 st continuous feeding unit 151a has a continuous feeding shaft on which the 1 st roll 20a is provided, and continuously feeds the single-side protective polarizing film 21a with the pressure-sensitive adhesive layer in a belt shape on which the separator 5a is provided from the 1 st roll 20 a.

The 1 st cutting unit 152a includes a cutting mechanism such as a cutter or a laser device, and an adsorption mechanism. The 1 st cutting section 152a cuts the 1 st adhesive layer-attached one-side protective polarizing film 21a in a tape shape in the width direction by a given length and leaves the separator 5a. Note that, when a roll of the single-side protective polarizing film 21a (a roll of an optical film with cuts) in which a tape-like pressure-sensitive adhesive layer having a plurality of cuts formed in the width direction at a predetermined length is laminated on the separator 5a is used as the 1 st roll 20a, the 1 st cut unit 152a is not necessary (the same applies to the 2 nd cut unit 152b described later).

The 1 st peel-off part 153a peels the 1 st pressure-sensitive adhesive layer-attached one-side protective polarizing film 21a from the separator 5a by folding back with the separator 5a as the inside. The 1 st peeling section 153a may be a wedge member, a roller, or the like.

The 1 st winding unit 154a winds the separator 5a after peeling the 1 st pressure-sensitive adhesive layer-attached one-side protective polarizing film 21a. The 1 st winding part 154a has a winding shaft provided for winding the roll of the separator 5a.

(1 st attaching part)

The 1 st laminating unit 201a continuously laminates the 1 st pressure-sensitive adhesive layer-attached one-side protective polarizing film 21a peeled by the 1 st peeling unit 153a to the liquid crystal display panel P conveyed by the conveying unit X with the pressure-sensitive adhesive layer of the 1 st pressure-sensitive adhesive layer-attached one-side protective polarizing film 21a interposed therebetween (1 st laminating step). The 1 st bonding section 81 includes a pair of bonding rollers, and at least one of the bonding rollers is a driving roller.

(No. 2 polarizing film supply section)

The 2 nd polarizing film supply unit 101b continuously attaches the 2 nd pressure-sensitive adhesive layer-attached single-sided protective polarizing film (surface-attached protective film) 21b continuously fed from the 2 nd roll 20b and conveyed by the separator 5b to the 2 nd attaching unit 201b. The 2 nd polarizing film supply section 101b has: a 2 nd continuous feeding section 151b, a 2 nd cutting section 152b, a 2 nd peeling section 153b, a 2 nd winding section 154b, a plurality of conveyance roller sections, an energy storage section such as a dancer roller, and the like. The 2 nd continuous feeding unit 151b, the 2 nd cutting unit 152b, the 2 nd peeling unit 153b, and the 2 nd winding unit 154b have the same configurations and functions as the 1 st continuous feeding unit 151a, the 1 st cutting unit 152a, the 1 st peeling unit 153a, and the 1 st winding unit 154a, respectively.

(No. 2 bonding part)

The 2 nd laminating unit 201b continuously laminates the 2 nd pressure-sensitive adhesive layer-attached single-side protective polarizing film 21b peeled by the 2 nd peeling unit 153b to the liquid crystal display panel P conveyed by the conveying unit X with the pressure-sensitive adhesive layer of the 2 nd pressure-sensitive adhesive layer-attached single-side protective polarizing film 21b interposed therebetween (2 nd laminating step). The 2 nd bonding portion 201b is configured to have a pair of bonding rollers, and at least one of the bonding rollers is configured by a driving roller.

Examples

The present invention will be described with reference to examples, but the present invention is not limited to the examples shown below. In each example, parts and% are on a weight basis. Hereinafter, the room temperature conditions not particularly specified were all 23 ℃ and 65% RH.

< preparation of Single-sided protective polarizing film A >

(fabrication of polarizing lens)

One surface of a substrate of an amorphous polyethylene terephthalate isophthalate copolymer (IPA-copolymerized PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ℃ was subjected to corona treatment, and an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl-modified rate 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon synthetic chemical industries, ltd., trade name "GOHSEFIMER Z200") at a ratio of 9.

The resultant laminate was subjected to free-end uniaxial stretching (auxiliary stretching treatment in a gas atmosphere) of 2.0 times in the longitudinal direction (longitudinal direction) in an oven at 120 ℃ between rolls having different peripheral speeds.

Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment).

Next, the polarizing plate was immersed in a dyeing solution at a liquid temperature of 30 ℃ while adjusting the iodine concentration and the immersion time so that the polarizing plate has a predetermined transmittance. In this example, an aqueous iodine solution prepared by adding 0.2 parts by weight of iodine and 1.0 part by weight of potassium iodide to 100 parts by weight of water was immersed for 60 seconds (dyeing treatment).

Subsequently, the substrate was immersed for 30 seconds in a crosslinking bath (aqueous boric acid solution containing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid based on 100 parts by weight of water) at a liquid temperature of 30 ℃ (crosslinking treatment).

Then, the laminate was immersed in an aqueous boric acid solution (an aqueous solution prepared by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70 ℃, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times (stretching treatment in an aqueous solution).

Then, the laminate was immersed in a cleaning bath (aqueous solution prepared by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30 ℃ (cleaning treatment).

By the above operation, an optical film laminate including a polarizer having a thickness of 5 μm and a boric acid content of 16% was obtained. The boric acid content in the polarizer was measured by the following method.

The obtained polarizer was measured for a boric acid peak (665 cm) by attenuated total reflection spectroscopy (ATR) measurement using polarized light as measurement light, using a fourier transform infrared spectrophotometer (FTIR) (product name "spectra 2000" manufactured by Perkin Elmer corporation) ^-1 ) Intensity of (2) and control Peak (2941 cm) ^-1 ) The strength of (2). From the obtained boric acid peak intensity and the control peak intensity, the boric acid amount index was calculated by the following formula, and further the boric acid content (% by weight) was determined from the calculated boric acid amount index by the following formula.

(boric acid amount index) = (boric acid peak 665 cm) ^-1 Intensity of (2)/(control Peak 2941 cm) ^-1 Strength of (2)

(boric acid content (% by weight)) = (boric acid amount index) × 5.54+4.1

(preparation of transparent protective film)

Transparent protective film: the easy-adhesion-treated surface of a (meth) acrylic resin film having a lactone ring structure and having a thickness of 40 μm was subjected to corona treatment and used.

(preparation of adhesive suitable for transparent protective film)

An ultraviolet-curable adhesive was prepared by mixing 40 parts by weight of N-hydroxyethyl acrylamide (HEAA), 60 parts by weight of acryloyl morpholine (ACMO), and 3 parts by weight of a photoinitiator IRGACURE 819 (BASF corporation).

(preparation of Single-sided protective polarizing film A)

The ultraviolet-curable adhesive is applied to the surface of the polarizer of the optical film laminate so that the thickness of the cured adhesive layer becomes 0.5 μm, the transparent protective film is bonded thereto, and then ultraviolet rays are irradiated as active energy rays to cure the adhesive. The ultraviolet irradiation uses a gallium-sealed metal halide lamp and an irradiation device: light HAMMER10 manufactured by Fusion UV Systems, valve: v valve, maximum illumination 1600mW/cm ² Cumulative dose of radiation 1000/mJ/cm ² (wavelength 380 to 440 nm) and the illuminance of ultraviolet light were measured by using Sola-Check system manufactured by Solatell corporation. Next, the amorphous PET substrate was peeled off, and a single-sided protective polarizing film a using a thin polarizer was produced. When the monomer transmittance T and the degree of polarization P of the polarizer were measured by the following methods using the obtained one-side protective polarizing film a, the monomer transmittance T of the polarizer was 42.8%, and the degree of polarization P of the polarizer was 99.99%.

The single transmittance T and the degree of polarization P of the polarizer of the obtained single-sided protective polarizing film a were measured using a spectral transmittance measuring instrument with an integrating sphere (Dot-3 c from mura color technical research institute).

The degree of polarization P was determined by applying the transmittance (parallel transmittance: tp) when 2 identical single-sided protective polarizing films A were stacked so that the transmission axes thereof were parallel to each other and the transmittance (orthogonal transmittance: tc) when the transmission axes thereof were orthogonal to each other to the following equationAnd (6) discharging. Polarization degree P (%) = { (Tp-Tc)/(Tp + Tc) } ^1/2 ×100

Each transmittance is a transmittance represented by a Y value measured in a 2-degree field of view (C light source) according to JIS Z8701 and corrected for visibility, assuming that the fully polarized light obtained after passing through the glan-taylor prism polarizer is 100%.

< preparation of Single-sided protective polarizing film B >

A polyvinyl alcohol film having a thickness of 80 μm was stretched 3-fold while being dyed in a 0.3% iodine solution at 30 ℃ for 1 minute between rolls having different speed ratios. Then, the film was stretched while being immersed in an aqueous solution containing 4% concentration of boric acid and 10% concentration of potassium iodide at 60 ℃ for 0.5 minute so that the total stretching ratio was 6 times. Subsequently, the film was immersed in an aqueous solution containing potassium iodide at a concentration of 1.5% at 30 ℃ for 10 seconds to wash the film, and then dried at 50 ℃ for 4 minutes to obtain a polarizer having a thickness of 20 μm. A saponified 40 μm acrylic resin film (transparent protective film) was bonded to one surface of the polarizer with an adhesive to prepare a single-sided protective polarizing film B.

< formation of adhesive layer >

(preparation of acrylic adhesive A)

A monomer mixture containing 91.8 parts of N-butyl acrylate, 6 parts of methyl methacrylate, 1.5 parts of N-vinylpyrrolidone, 0.2 part of acrylic acid and 0.5 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a condenser. Further, 0.15 part of 2,2' -azobisisobutyronitrile as a polymerization initiator was fed together with ethyl acetate to 100 parts of the above monomer mixture (solid content), nitrogen gas was introduced while slowly stirring to replace nitrogen gas, and then the polymerization reaction was carried out for 7 hours while maintaining the liquid temperature in the flask at about 60 ℃. Then, ethyl acetate was added to the obtained reaction solution to prepare a solution of an acrylic polymer having a weight-average molecular weight of 130 ten thousand and a solid content concentration of 20%.

The weight average molecular weight (Mw) of the acrylic polymer was measured using a GPC apparatus (HLC-8220 GPC) manufactured by Tosoh corporation. The measurement conditions are as follows.

Sample concentration: 0.2% by mass (THF solution)

Sample injection amount: 10 μ l

Eluent: THF

Flow rate: 0.6ml/min

Measuring temperature: 40 deg.C

And (3) chromatographic column: a sample column; TSKguardcolumn SuperHZ-H (1 root) + TSKgel SuperHZM-H (2 roots)

A reference column; TSKgel SuperH-RC (1 root)

A detector: differential Refractometer (RI)

The weight average molecular weight is determined by a polystyrene equivalent.

An acrylic pressure-sensitive adhesive A was prepared by mixing 0.17 parts of an isocyanate-based crosslinking agent (trade name "Takenate D160N", manufactured by Mitsui chemical Co., ltd.), 0.25 parts of a peroxide-based crosslinking agent (trade name "NYPER BMT", manufactured by Nippon fat and oil Co., ltd.) and 0.2 parts of an acetoacetylsilane-containing coupling agent (trade name "A-100", manufactured by Sukko chemical Co., ltd.) with respect to 100 parts of the solid content of the prepared acrylic polymer solution.

(preparation of acrylic Adhesives B to S)

In the preparation of the acrylic adhesive a, a solution of an acrylic polymer was prepared and acrylic adhesives B to S were prepared in the same manner except that the composition of the monomer was changed and the polymerization conditions were adjusted as shown in table 1.

(formation of adhesive layers A to S)

Then, the prepared acrylic adhesives a to S were uniformly applied to the surface of a polyethylene terephthalate film (separator) treated with a silicone-based release agent by a spray coater, and dried in an air circulation type constant temperature oven at 155 ℃ for 1 minute to form adhesive layers a to S having a thickness of 20 μm on the surface of each separator.

[ Table 1]

The compounds in table 1 are as follows.

BA: n-butyl acrylate (Tg: -50 ℃ C.)

MMA: methyl methacrylate (Tg: 105 ℃ C.)

MA: methyl acrylate (Tg: 8 ℃ C.)

IBXA: isobornyl acrylate (Tg: 94 ℃ C.)

ACMO: n-acryloyl morpholine (Tg: 145 ℃ C.)

NVP: n-vinyl pyrrolidone

AA: acrylic acid

4HBA: acrylic acid 4-hydroxybutyl ester

Examples 1 to 18 and comparative examples 1 to 3

< preparation of one-sided protective polarizing film with adhesive layer >

The adhesive layers a to S were bonded to the polarizer sides of the single-sided protective polarizing films a and B, respectively, to prepare single-sided protective polarizing films with adhesive layers.

The pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer-attached single-sided protective polarizing film obtained above were subjected to the following measurement and evaluation. The results are shown in Table 2.

< measurement of peaks of storage modulus and loss modulus >

The adhesive layers A to S prepared by Rheometric corporation were measured for their peaks of storage modulus and loss modulus at40 ℃ and 85 ℃ using a viscoelasticity spectrometer (trade name: RSA-II). The measurement conditions were: the frequency is 1Hz, the thickness of the sample is 2mm, the weight is increased by 100g by pressure adhesion, the temperature rise speed is 5 ℃/min, and the temperature range is-70 ℃ to 150 ℃.

< production inhibition of nano-slit: guitar pick test >

The pressure-sensitive adhesive layer-attached one-side protective polarizing films obtained in examples and comparative examples were cut into a size of 50mm × 150mm (50 mm in the absorption axis direction), and this was taken as sample 11. Sample 11 was used after a surface protection film 6 produced by the following method was bonded to one side of the protection film 2.

(surface protective film for test)

Into a four-necked flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a condenser, 94 parts by mass of 2-ethylhexyl acrylate (2 EHA), 1 part by mass of N, N-Diethylacrylamide (DEAA), 1 part by mass of ethoxydiglycol acrylate (EDE), 4 parts by mass of 4-hydroxybutyl acrylate (HBA), 0.2 part by mass of 2,2' -azobisisobutyronitrile as a polymerization initiator, and 150 parts by mass of ethyl acetate were charged, and nitrogen was introduced while slowly stirring, and the liquid temperature in the flask was maintained at about 60 ℃ to conduct a polymerization reaction for 5 hours, thereby preparing an acrylic polymer solution (40 mass%). The weight average molecular weight of the acrylic polymer was 57 ten thousand, and the glass transition temperature (Tg) was-68 ℃.

The acrylic polymer solution (40 mass%) was diluted with ethyl acetate to 20 mass%, and to 500 parts by mass (100 parts by mass of solid content) of the solution, 2 parts by mass (2 parts by mass of solid content) of an isocyanurate of hexamethylene diisocyanate (CORONATE HX: C/HX, manufactured by Nippon polyurethane industries, ltd.) and 2 parts by mass (0.02 part by mass of solid content) of dibutyltin dilaurate (1 mass% ethyl acetate solution) as a crosslinking catalyst were added and mixed with stirring to prepare an acrylic adhesive solution.

The acrylic pressure-sensitive adhesive solution was applied to a transparent polyethylene terephthalate (PET) film (polyester film) having a thickness of 38 μm, and heated at 130 ℃ for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 15 μm, thereby forming a surface protective film.

Next, as shown in the schematic view of fig. 3a and the cross-sectional view of fig. 3B, the release sheet (separator) was peeled from sample 11 and adhered to glass plate 20 via exposed adhesive layer 4. Next, a load of 200g was applied to the central portion of sample 11 (surface protective film 6 side) by a guitar pick (model "HP2H (HARD)" manufactured by hitory corporation), and a load of 50 round trips was repeated in a distance of 100mm in the direction orthogonal to the absorption axis of polarizer 1 of sample 11. The load was applied to 1 site. The load is applied at a high speed (5 m/min) and a low speed (1 m/min).

Next, after sample 11 was left to stand at 80 ℃ for 1 hour, the presence or absence of cracks due to light leakage in sample 11 was confirmed by the following criteria.

(high speed case)

Very good: 0 to 10

O: 11 to 15

And (delta): 16 to 30

X: more than 31

(Low speed case)

Excellent: 0 number of

O: 1 to 3

And (delta): 4 to 5

X: more than 6

Fig. 4 is an example of a microscopic photograph of the surface of a polarizing film, showing the following index of a crack (nano slit a) to confirm light leakage in a guitar pick test using the one-side protective polarizing film 11 with an adhesive layer. In fig. 4 (a), cracks of light leakage due to the nano slits a are not confirmed. On the other hand, fig. 4 (B) shows a case where 3 cracks of light leakage due to the nanoslits a are generated in the absorption axis direction of the polarizer by heating. In fig. 4, the sample in which the nano-slit is generated is observed by using a differential interference microscope. When a sample was photographed, a sample in which no nano-slit was generated was placed under a sample in which a nano-slit was generated (on the side of a transmission light source) so as to have an orthogonal nicol relationship, and observation was performed using transmission light.

< evaluation of durability >

The separator of the one-side protective polarizing film (37 inches) having an adhesive layer was peeled off, and bonded to alkali-free glass (EG-XG, manufactured by Corning) having a thickness of 0.7mm using a laminator. Then, the polarizing film was completely adhered to the alkali-free glass by autoclave treatment at 50 ℃ and 0.5MPa for 15 minutes. Then, the polarizing plates were put into a heating oven (heating) at 80 ℃ and a constant temperature and humidity machine (humidifying) at 60 ℃/90% RH, and the presence or absence of peeling of the polarizing plates after 500 hours was evaluated according to the following criteria.

Very good: no peeling was observed at all.

O: peeling was observed to an extent not visually recognized.

And (delta): a small detachment that is identifiable to the naked eye is observed.

X: significant peeling was observed.

As is clear from table 2, the pressure-sensitive adhesive layer-attached one-side protective polarizing films of examples 1 to 18 were less likely to crack both when a load was applied at a high speed and when a load was applied at a low speed, and were excellent in durability (peeling resistance) at high temperature and high humidity. On the other hand, it is found that the one-side protective polarizing films with an adhesive layer of comparative examples 1 to 3 have a large number of cracks both when a load is applied at a high speed and when a load is applied at a low speed. In addition, comparing the pressure-sensitive adhesive layer-attached one-side protective polarizing film of example 14 with the pressure-sensitive adhesive layer-attached one-side protective polarizing film of example 17, it was found that the pressure-sensitive adhesive layer-attached one-side protective polarizing film of example 14, in which the pressure-sensitive adhesive layer was formed using an acrylic polymer containing a nitrogen-containing monomer as a monomer unit, was less likely to cause cracks, and was more excellent in durability (peel resistance) at high temperatures and high humidities. Further, it is understood from examples 14 and 18 that the one-side protective polarizing film with an adhesive layer of the present invention is less likely to cause cracks even when the polarizer is thin or thick.

Industrial applicability

The pressure-sensitive adhesive layer-equipped single-sided protective polarizing film of the present invention can be used alone or in the form of an optical film obtained by laminating the polarizing film in an image display device such as a Liquid Crystal Display (LCD) device or an organic EL display device.

Claims

1. A single-sided protective polarizing film with an adhesive layer, which has a single-sided protective polarizing film having a protective film only on one side of a polarizer and has an adhesive layer directly or via a coating layer on the polarizer side of the single-sided protective polarizing film,

wherein, theThe adhesive layer has a storage modulus of 7.0X 10 at-40 deg.C ⁷ The pressure of the mixture is higher than Pa,

the adhesive layer contains a (meth) acrylic polymer as a base polymer,

the (meth) acrylic polymer contains, as monomer units:

70 wt% or more of (meth) acrylic acid alkyl ester (A) having a homopolymer glass transition temperature of less than 0 ℃;

0.1 to 15 wt% of at least one high Tg monomer (B) selected from an alkyl (meth) acrylate (B1) having a homopolymer glass transition temperature of 0 ℃ or higher and a (meth) acryloyl group-containing monomer (B2) having a homopolymer glass transition temperature of 0 ℃ or higher and a heterocycle; and

a nitrogen-containing monomer, a carboxyl-containing monomer and a hydroxyl-containing monomer as polar monomers other than the (meth) acryloyl-group-containing monomer (b 2),

the alkyl (meth) acrylate (A) is at least one selected from the group consisting of ethyl acrylate, n-butyl acrylate, n-pentyl methacrylate, and n-hexyl acrylate,

the alkyl (meth) acrylate (b 1) is at least one selected from the group consisting of methyl acrylate, methyl methacrylate, and ethyl methacrylate.

2. The adhesive layer-bearing single-sided protective polarizing film according to claim 1,

the peak of loss modulus of the adhesive layer is above-45 ℃.

3. The adhesive layer-bearing single-sided protective polarizing film according to claim 1, wherein the adhesive layer has a storage modulus at 85 ℃ of 5.5 x 10 ⁴ Pa or more and 1.4X 10 ⁵ Pa or less.

4. The adhesive layer-bearing single-sided protective polarizing film according to claim 3,

the nitrogen-containing monomer is a vinyl monomer with a lactam ring.

5. The adhesive layer-bearing single-sided protective polarizing film according to claim 4,

the vinyl monomer with the lactam ring is a vinyl pyrrolidone monomer.

6. The adhesive layer-bearing single-sided protective polarizing film according to claim 5,

the vinyl pyrrolidone monomer is N-vinyl pyrrolidone.

7. The adhesive layer-equipped single-sided protective polarizing film according to any one of claims 4 to 6,

the (meth) acrylic polymer contains 0.1 to 5% by weight of the nitrogen-containing monomer as a monomer unit.

8. The adhesive layer-bearing single-sided protective polarizing film according to any one of claims 4 to 6,

the (meth) acrylic polymer contains 0.01 to 3% by weight of the carboxyl group-containing monomer as a monomer unit.

9. The adhesive layer-equipped single-sided protective polarizing film according to any one of claims 4 to 6,

the (meth) acrylic polymer contains 0.01 to 1% by weight of the hydroxyl group-containing monomer as a monomer unit.

10. The adhesive layer-equipped single-sided protective polarizing film according to any one of claims 1 to 6,

the thickness of the polarizer is less than 12 μm.

11. The pressure-sensitive adhesive layer-equipped one-side protective polarizing film according to any one of claims 1 to 6, wherein the polarizer contains a polyvinyl alcohol-based resin, and is configured so that optical properties represented by a monomer transmittance T and a degree of polarization P satisfy the following conditions:

P＞－(10 ^0.929T-42.4 -1) x 100, wherein T < 42.3; or

P is more than or equal to 99.9, wherein T is more than or equal to 42.3.

12. The adhesive layer-bearing single-sided protective polarizing film according to any one of claims 1 to 6,

the polarizer contains boric acid in an amount of 25 wt% or less based on the total amount of the polarizer.

13. The adhesive layer-bearing single-sided protective polarizing film according to any one of claims 1 to 6,

a separator is disposed on the adhesive layer.

14. The adhesive layer-bearing single-sided protective polarizing film according to claim 13, which is a roll.

15. An image display device having the adhesive layer-attached one-side protective polarizing film of any one of claims 1 to 12.

16. A method for continuously manufacturing an image display device, comprising the steps of:

the pressure-sensitive adhesive layer-attached one-side protective polarizing film continuously fed from the roll of the pressure-sensitive adhesive layer-attached one-side protective polarizing film of claim 14 and conveyed by the separator is continuously bonded to the surface of an image display panel via the pressure-sensitive adhesive layer.

17. An adhesive agent which is a material for forming an adhesive agent layer provided on the polarizer side of a one-side protective polarizing film having a protective film only on one surface of a polarizer,

the adhesive contains at least a (meth) acrylic polymer containing, as monomer units:

18. The adhesive of claim 17, wherein,

the nitrogen-containing monomer is a vinyl monomer with a lactam ring.

19. The adhesive according to claim 18, wherein,

the vinyl monomer with the lactam ring is a vinyl pyrrolidone monomer.

20. The adhesive according to claim 19, wherein,

the vinyl pyrrolidone monomer is N-vinyl pyrrolidone.

21. The adhesive according to any one of claims 17 to 20,

22. The adhesive according to any one of claims 17 to 20,

23. The adhesive according to any one of claims 17 to 20,