CN106468797B

CN106468797B - Polarizing plate for curved image display panel

Info

Publication number: CN106468797B
Application number: CN201610682019.8A
Authority: CN
Inventors: 名田敬之
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2015-08-18
Filing date: 2016-08-17
Publication date: 2020-04-14
Anticipated expiration: 2036-08-17
Also published as: KR102392232B1; TW201712376A; KR20170021754A; CN106468797A; TWI760310B; JP6825848B2; JP2017126057A

Abstract

The present invention aims to provide a polarizing plate for a curved image display panel, which can suppress peeling and lifting of the display panel from a curved state even after long-term use and/or use in a high-temperature environment. A polarizing plate having a horizontal length L1 in a planar state for a curved image display panel having an average radius of curvature R and a thickness H, wherein the thickness H1(mm) of the polarizing plate on the concave side satisfies the following formula (1) when the polarizing plate is bonded to the curved image display panel: l1(H + H1)/2R is less than or equal to 0.4 (1).

Description

Polarizing plate for curved image display panel

Technical Field

The present invention relates to a polarizing plate for a curved image display panel and a curved image display panel including the same.

Background

Conventionally, as a polarizing plate used for various image display panels such as a liquid crystal display panel and an organic electroluminescence (organic EL) display panel, a polarizing plate having the following structure is known: a protective film such as a triacetyl cellulose film is laminated on one or both surfaces of a polarizing film having a dichroic dye such as iodine or a dichroic dye oriented and adsorbed on a polyvinyl alcohol resin film via an adhesive layer (for example, patent documents 1 to 3). Such a polarizing plate is further bonded to an image display element such as a liquid crystal cell or an organic EL display element in a form in which various optical layers such as a retardation film and an optical compensation film are laminated as necessary, thereby constituting an image display panel.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2010-211196

Patent document 2: japanese laid-open patent publication No. 10-062624

Patent document 3: japanese laid-open patent publication No. H07-134212

Disclosure of Invention

Problems to be solved by the invention

In recent years, from the viewpoint of appearance, studies have been made on image display devices of various shapes. Among them, a feeling of penetration in a screen is obtained because a difference between a distance from a viewer to a center of a screen and a distance from the viewer to a side end is small, and thus attention is being paid to a curved image display device such as a curved liquid crystal television, and various product developments are being performed.

In the curved image display device, the polarizing plate is used similarly to the flat image display device, but when the conventional polarizing plates disclosed in the above patent documents 1 to 3 are used for the curved display panel in order to manufacture the curved image display device, the polarizing plate may be peeled off or lifted from the curved display panel over time. In a curved display panel, peeling and floating of a polarizing plate are likely to occur particularly on the concave side (viewing side), resulting in poor display in the viewing region. In addition, the occurrence of peeling or floating of the polarizing plate from the curved display panel becomes particularly remarkable in a high-temperature environment. Therefore, when the light source is exposed to heat from a light source for a long time due to long-term use or the like, or when the light source is transported in a high-temperature and high-humidity environment, or depending on a region where the light source is used, more serious peeling or floating may occur.

Accordingly, an object of the present invention is to solve the above problems that may occur in a polarizing plate for a curved image display panel, and to provide a polarizing plate for a curved image display panel that can suppress peeling and lifting of a display panel from a curved state even after long-term use and/or use in a high-temperature environment.

Means for solving the problems

The present invention provides the following preferred embodiments [1] to [8 ].

[1] A polarizing plate for a curved image display panel having an average curvature radius R (mm) and a thickness H (mm), the polarizing plate having a horizontal length L1(mm) in a planar state,

when the laminate is bonded to a curved image display panel, the thickness H1(mm) of the polarizing plate on the concave side satisfies the following formula (1):

L1(H+H1)/2R≤0.4 (1)。

[2] the polarizing plate according to [1], wherein the curved image display panel has a thickness H of 0.4mm or more.

[3] The polarizing plate according to the above [1] or [2], wherein a dimensional change rate after 250 hours in a drying environment at 80 ℃ is 3% or less.

[4] The polarizing plate according to any one of the above [1] to [3], wherein the polarizing film in the polarizing plate is a stretched and/or dyed polyvinyl alcohol film.

[5] The polarizing plate according to any one of the above [1] to [4], wherein the curved image display panel has an average curvature radius R of 900 to 7000 mm.

[6] The polarizing plate according to any one of the above [1] to [5], wherein a horizontal length L1 of the polarizing plate in a planar state is 500mm or more.

[7] A curved image display panel comprising a concave-side polarizing plate and a convex-side polarizing plate, wherein the concave-side polarizing plate is the polarizing plate according to any one of [1] to [6 ].

[8] A curved image display panel comprising a concave-side polarizing plate and a convex-side polarizing plate, wherein the concave-side polarizing plate and the convex-side polarizing plate are the polarizing plates described in any one of [1] to [6 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a polarizing plate for a curved image display panel can be provided which can suppress peeling and lifting of the display panel from a curved state even after long-term use and/or use in a high-temperature environment.

Drawings

Fig. 1 is a schematic diagram of a curved image display panel for explaining an average radius of curvature.

Fig. 2 is a cross-sectional view of an image display panel including a curved polarizing plate.

Fig. 3 is a cross-sectional view showing a structure of a polarizing plate and a structure of one embodiment of a curved image display panel.

Fig. 4 shows an example of the absorption axis direction of a polarizing plate in a curved image display device.

Fig. 5 shows an example of the absorption axis direction of a polarizing plate in a curved image display device.

Description of the symbols

1: concave side polarizing plate

2: convex side polarizing plate

3: image display element

10: adhesive layer

11: protective layer

12: polarizing film

13: surface treatment layer

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

In the present invention, the "flat state" refers to a state in which the entire body is flat without including a bent portion. The "curved surface state" is a sum of a state in which the entire curved surface is bent by one arc and a state in which the entire curved surface is formed including a bent portion by one or a plurality of arcs, except for a case specified by a measurement method or the like. In the present invention, the "average radius of curvature" means an average value of the radius of curvature at 3 points at both right and left end portions and a central portion of the display panel. That is, in FIG. 1, the average radius of curvature is represented by (R)_{Left side of}+R_In+R_{Right side}) The calculated value of/3.

The present invention relates to a polarizing plate for a curved image display panel having an average radius of curvature r (mm) and a thickness h (mm). The polarizing plate of the present invention has a horizontal length of L1(mm) in a planar state, and a thickness H1(mm) of the polarizing plate which becomes a concave surface side when the polarizing plate is bonded to the curved image display panel satisfies the following formula (1):

L1(H+H1)/2R≤0.4 (1)。

in the present invention, the concave side means a side corresponding to the viewing side of the curved image display panel, and the convex side means a side facing the concave side.

Here, a polarizing plate having the same horizontal direction length and a thickness H1 was attached to an image display panel having a horizontal direction length of L1 and a thickness H in a planar state, and was curved so as to have an average radius of curvature R (where R is defined as a radius to the center of the panel thickness) (see fig. 2), and at this time, the length of the center portion of the panel was not changed based on the reference. On the other hand, the length of the curved polarizing plate in the horizontal direction (defined as the length of the center position of the thickness of the polarizing plate) can be calculated as the length of an arc having a curvature radius { R- (H + H1)/2 }. The present inventors found that the change from L1 to this length is important for solving the problem of the present invention. Accordingly, in the present invention, in order to suppress peeling and lifting of the polarizing plate, the amount of change, that is, the following formula: it is important that L1-L1{ R- (H + H1)/2}/R is suppressed to a low level, i.e., 0.4 or less, in L1(H + H1)/2R.

The value of L1(H + H1)/2R in formula (1) is 0.40 or less, preferably 0.38 or less, more preferably 0.35 or less, and still more preferably 0.30 or less. When the value of L1(H + H1)/2R in the formula (1) is equal to or less than the upper limit value, the polarizing plate is less likely to be peeled or lifted from the curved image display panel even after long-term use or use in a high-temperature environment. The value of L1(H + H1)/2R in formula (1) is usually 0.01 or more.

The curved image display panel is generally not curved in the vertical direction (vertical direction), but curved in the horizontal direction (horizontal direction) so that a viewer side forms a concave surface and an opposite side (side of a backlight unit or the like) forms a convex surface, and forms a part of a cylinder whose central axis is the vertical direction (vertical direction).

The curved image display panel has a thickness H of preferably 0.4mm or more, more preferably 0.8mm or more, and further preferably 1.0mm or more. When the thickness H of the curved image display panel is equal to or greater than the lower limit value, various materials can be used as a member for the curved image display panel, and the curved image display panel is industrially advantageous because the curved image display panel can be easily handled even when the display panel is increased in size. The thickness H of the curved image display panel is usually 2.0mm or less.

The curved image display panel has an average radius of curvature R of preferably 7000mm or less, more preferably 6600mm or less, further preferably 5000mm or less, further more preferably 4000mm or less, and particularly preferably 3000mm or less. The curved image display panel has an average radius of curvature R of, for example, 300mm or more, preferably 900mm or more, more preferably 1000mm or more, and further preferably 1200mm or more. The curved image display panel has an average radius of curvature R of preferably 900 to 7000mm, more preferably 1000 to 6600 mm. When the average curvature radius R of the curved image display panel is equal to or less than the upper limit value, the difference between the distance from the viewer to the center of the screen and the distance to the edge of the screen becomes smaller, and the feeling of immersion in the screen can be further obtained. When the average radius of curvature R of the curved image display panel is equal to or greater than the lower limit value, peeling and lifting of the polarizing plate from the curved image display panel due to long-term use or use in a high-temperature environment are further suppressed.

The average radius of curvature R of the curved image display panel also varies depending on the apparatus used. For example, in the case of a device having a small-sized display such as a personal computer or a mobile device, the average curvature radius R is smaller (curvature is larger) in many cases. In addition, in an apparatus having a large-sized display such as a curved-surface display television, there is a case where it is desired to further improve the feeling of immersion by reducing the average curvature radius R. The polarizing plate of the present invention has an excellent effect of suppressing peeling and lifting of the polarizing plate from the display panel even when used for a long period of time and/or under a high temperature environment in a state where the average radius of curvature R is small, and therefore can be used for a curved image display panel having an average radius of curvature R of 900 to 7000mm, particularly 900 to 5000mm, or even 1000 to 4000mm, for example.

The horizontal direction length L1 of the polarizing plate of the present invention in a planar state is preferably 500mm or more, more preferably 700mm or more, further preferably 1100mm or more, and further more preferably 1400mm or more. When the horizontal direction length L1 of the polarizing plate of the present invention in a planar state is equal to or greater than the above-described lower limit, the horizontal direction length of the applicable curved image display panel increases, and a feeling of penetration into the screen can be further obtained. The horizontal length L1 of the polarizing plate of the present invention in a planar state is usually 2500mm or less. The horizontal direction of the polarizing plate coincides with the horizontal direction of a curved image display device including a curved image display panel, and the vertical direction of the polarizing plate is a direction perpendicular to the horizontal direction. The vertical length of the polarizing plate of the present invention in a planar state is determined by the horizontal length L1 and the aspect ratio of the curved image display panel.

When a conventional polarizing plate is used for manufacturing a curved image display panel, the possibility of peeling or lifting of the polarizing plate from the curved image display panel is increased even in a normal temperature environment and when the polarizing plate is used for a long time, and peeling or lifting of the polarizing plate from the curved image display panel is further promoted over a long time of lighting or use in a high temperature environment. The reason is not limited to a particular theory, but is considered to be due to a strain and a compressive stress in the horizontal direction caused by the curving of the polarizing plate. In order to suppress the strain and the compressive stress, it is considered that the thickness H1 of the polarizing plate is changed in accordance with the average curvature radius R, the thickness H, and the horizontal length L1 of the curved image display panel, which is effective for suppressing the peeling and lifting of the polarizing plate from the curved image display panel. In the present invention, the thickness H1 of the polarizing plate is determined so as to satisfy the above formula (1), thereby achieving suppression of peeling and lifting of the polarizing plate.

The polarizing plate of the present invention preferably has a dimensional change rate of 3.0% or less, more preferably 2.0% or less, and still more preferably 1.5% or less after drying at 80 ℃ for 250 hours. When the above dimensional change rate of the polarizing plate is equal to or less than the above upper limit value, shrinkage and/or expansion of the polarizing plate in a long-term use or high-temperature environment can be suppressed, and therefore, peeling or lifting of the polarizing plate from the image display panel in a curved state is less likely to occur. The above-mentioned dimensional change rate of the polarizing plate is usually 0% or more.

The dimensional change rate can be controlled by suppressing the dimensional change of the polarizing film contributing to the shrinkage and expansion of the polarizing plate. The dimensional change of the polarizing film can be controlled by, for example, changing the production conditions and types such as the stretching ratio of the polarizing film, or increasing the rigidity of the protective layer adjacent to the polarizing film. Specifically, the dimensional change can be controlled by setting the stretch ratio to be preferably 8 times or less, more preferably 7.5 times or less, and further preferably 7 times or less.

It should be noted that the size change rate can be calculated as follows: the polarizing plate was cut into a size of 100mm × 100mm, and the initial size and the size after 250 hours in a dry environment at 80 ℃ were measured and compared without being attached to glass. Of course, the rate of dimensional change when the glass is bonded with the adhesive is smaller than the rate of dimensional change when the glass is not bonded. The dimensional change rate when glass is not bonded is usually about 1/2 to 1/15, depending on the type of adhesive.

The polarizing plate of the present invention is not limited to the structure as long as it has a function generally possessed as a polarizing plate, and for example, a preferable embodiment includes: a polarizing film, a protective layer laminated on one or both surfaces of the polarizing film via an adhesive, an adhesive layer for bonding to an image display element, and an optical layer in some cases.

In one embodiment of the present invention, a polarizing plate is composed of a protective layer, a polarizing film, a protective layer, and an adhesive layer, and an optical layer according to circumstances. Here, the polarizing film and the protective layer are laminated via an adhesive.

In the explanation of the structure of one embodiment of the polarizing plate and the curved image display panel according to the present invention with reference to fig. 3, the polarizing plate according to the present invention is formed by laminating an adhesive layer (10), a protective layer (11), a polarizing film (12), a protective layer (11), and an optical layer (not shown) as needed in this order from a layer adjacent to the image display element (3). The polarizing film (12) and the protective layer (11) are generally laminated via an adhesive. In one embodiment of the present invention, a curved image display panel of the present invention is configured from an image display element (3), and a concave-side polarizing plate (1) and a convex-side polarizing plate (2) which are bonded to the image display element (3) via adhesive layers (10), respectively. In one embodiment of the present invention, the concave-side polarizing plate (1) is composed of an adhesive layer (10), a protective layer (11), a polarizing film (12), a protective layer (11), and, if necessary, a surface treatment layer (13) and/or an optical layer in this order from the layer adjacent to the image display element (3), and the convex-side polarizing plate (2) is composed of an adhesive layer (10), a protective layer (11), a polarizing film (12), a protective layer (11), and, if necessary, an optical layer in this order from the layer adjacent to the image display element (3).

Hereinafter, each constituent component of the polarizing plate of the present invention will be described in detail.

< adhesion layer >

As the adhesive constituting the adhesive layer, conventionally known adhesives can be used without particular limitation, and for example, adhesives containing a base polymer such as acrylic, rubber, urethane, silicone, or polyvinyl ether can be used. Further, an energy ray-curable adhesive, a thermosetting adhesive, or the like may be used. Among them, an acrylic resin excellent in transparency, adhesion, reworkability, weather resistance, heat resistance and the like is suitable as a binder of the base polymer.

The acrylic pressure-sensitive adhesive is not particularly limited, and a (meth) acrylate-based base polymer such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, or a copolymer-based base polymer containing two or more of these (meth) acrylates, is preferably used. In addition, polar monomers are copolymerized in the base polymers of these. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

These acrylic binders may be used alone, but are usually used in combination with a crosslinking agent. As the crosslinking agent, there are exemplified: divalent or polyvalent metal ions capable of forming a metal carboxylate salt with the carboxyl group; polyamine compounds capable of forming an amide bond with a carboxyl group; a polyepoxy compound or a polyol compound which can form an ester bond with a carboxyl group; polyisocyanate compounds capable of forming an amide bond with a carboxyl group, and the like. Among them, polyisocyanate compounds are widely used.

The energy ray-curable adhesive means an adhesive having the following properties: the adhesive has a property of being cured by being irradiated with an energy ray such as an ultraviolet ray or an electron beam, has adhesiveness even before irradiation with an energy ray, adheres to an adherend such as a film, and can be cured by irradiation with an energy ray to adjust the adhesion force. As the energy ray-curable adhesive, an ultraviolet ray-curable adhesive is particularly preferably used. The energy ray-curable adhesive is generally composed mainly of an acrylic adhesive and an energy ray-polymerizable compound. Usually, a crosslinking agent is further blended, and a photopolymerization initiator, a photosensitizer, or the like may be blended as necessary.

The pressure-sensitive adhesive layer may contain, in addition to the base polymer and the crosslinking agent, additives such as natural or synthetic resins, adhesion-imparting resins, antioxidants, antistatic agents, ultraviolet absorbers, dyes, pigments, defoaming agents, corrosive agents, photopolymerization initiators, and thermal polymerization initiators, as necessary, for adjusting the adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, and the like of the pressure-sensitive adhesive. Further, the adhesive layer may contain fine particles to exhibit light scattering properties. The ultraviolet absorber includes: salicylate-based compounds, benzophenone-based compounds, benzotriazole-based compounds, cyanoacrylate-based compounds, nickel complex salt-based compounds, and the like.

In the present invention, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer preferably contains a silane compound, and particularly preferably contains a silane compound in advance in the acrylic resin before the crosslinking agent is blended. Since the silane compound improves the adhesion to glass, the silane compound improves the adhesion between the image display element held between the glass substrate and the adhesive layer, and ensures high adhesion to the display panel, and therefore, the display panel is less likely to peel off or float from the curved display panel even when used for a long period of time and/or under a high temperature environment.

The adhesive layer can be provided, for example, by the following method: the adhesive agent as described above is prepared as an organic solvent solution, and the adhesive layer is applied to a film or a layer (for example, a polarizing film) to be laminated by a die coater, a gravure coater, or the like, and dried. In addition, the setting may be performed by: the sheet-like adhesive formed on the plastic film (also referred to as a separator) subjected to the release treatment is transferred to a film or layer to be laminated. The thickness of the adhesive layer is not particularly limited, but is preferably within a range of 2 to 40 μm, more preferably within a range of 5 to 35 μm, and still more preferably within a range of 10 to 30 μm. When the thickness of the adhesive layer is not less than the lower limit, peeling and lifting due to long-term use and/or use under a high-temperature environment can be further suppressed. When the thickness of the adhesive layer is equal to or less than the upper limit, the increase in thickness of the polarizing plate is suppressed, and as a result, the adhesive layer is less likely to deform in a curved surface state, and peeling and lifting due to long-term use and/or use under a high-temperature environment can be suppressed. Thereby, the degradation of the display function at the periphery of the frame of the image display device can be suppressed.

In a preferred embodiment, the adhesive layer of the polarizing plate of the present invention is composed of an acrylic resin which is a copolymer of butyl acrylate, methyl acrylate, 2-phenoxyethyl acrylate, 2-hydroxyethyl acrylate and acrylic acid, a silane-based compound, and an isocyanate compound which is a crosslinking agent.

In a preferred embodiment, the polarizing plate of the present invention includes an adhesive layer. The adhesive layer preferably has an adhesive force to glass (hereinafter sometimes referred to as "adhesive force to glass (flat surface, 23 ℃)") measured in a flat state at 23 ℃ and 50% RH of 1.0N/25mm or more, more preferably 2.0N/25mm or more. When the adhesive force (plane, 23 ℃) of the adhesive layer to glass is 1.0N/25mm or more, peeling and lifting of the polarizing plate from the curved image display panel can be more effectively suppressed in continuous use for a long time, use for a long time and/or under a high temperature environment, movement, storage, and the like. The polarizing plate of the present invention has a glass adhesion (in-plane, 23 ℃) of more preferably 3.0N/25mm or more, and particularly preferably 4.0N/25mm or more.

In the polarizing plate of the present invention, the adhesive strength to glass of the adhesive layer (hereinafter sometimes referred to as "adhesive strength to glass (curved surface, 23 ℃)") measured in a curved surface state is preferably 1.5N/25mm or more, and more preferably 2.5N/25mm or more. The adhesion strength to glass (curved surface, 23 ℃) of the polarizing plate of the present invention is more preferably 3.5N/25mm or more, and still more preferably 4.5N/25mm or more. The adhesion to glass measured in a curved state is not necessarily the same as the adhesion to glass measured in a flat state, and does not change according to a certain rule such as a simple proportional relationship. The polarizing plate of the present invention is used for a curved image display device, and therefore, the adhesion force to glass in a curved state can be controlled to a certain extent, and the adhesion force to an image display element of the polarizing plate can be controlled in a more practical state than in the case where the adhesion force to glass of the polarizing plate is controlled only by the adhesion force to glass in a planar state. In particular, when the adhesion to glass (curved surface, 23 ℃) is 1.5N/25mm or more, and further 2.5N/25mm or more, sufficient adhesion to the image display panel can be secured even in a severe environment such as when the polarizing plate is incorporated into a curved image display panel after long-term use, when the polarizing plate is exposed to heat from a light source for a long time use, or when the polarizing plate is transported in a state where a high-temperature and high-humidity environment is likely to be formed, and peeling or lifting of the polarizing plate from the curved image display panel is unlikely to occur.

From the viewpoint of sufficiently securing the adhesion to the image display panel under a long-term and/or high-temperature environment, the adhesion to glass (planar, 23 ℃) and the adhesion to glass (curved, 23 ℃) of the polarizing plate of the present invention are preferably 2.0N/25mm or more, more preferably 3.0N/25mm or more, and particularly preferably 4.0N/25mm or more.

On the other hand, in the process of manufacturing a curved image display panel, when a polarizing plate is bonded to an image display element or when a failure occurs after bonding, rework may be performed in a flat state (that is, the panel is peeled off and reused) in the same manner as in the process of manufacturing a conventional flat image display panel. When reworking is performed in a curved state, in addition to the compressive stress that has already been applied due to the curved state, a compressive stress is further applied to peel the polarizing plate from the image display panel. Therefore, in the case of rework in a curved state, it is technically difficult to peel the polarizing plate from the curved image display panel as compared with rework in a planar state, and in particular, the higher the adhesive force of the polarizing plate, the greater the compressive stress applied to peel the polarizing plate, and therefore, defects such as breakage of the glass plate constituting the display panel at the time of peeling are likely to occur.

When the adhesion to glass is too high, the image display panel may not be lifted or peeled off from the polarizing plate, but since such reworkability may cause a problem, the adhesion to glass (planar, 23 ℃) measured in a planar state of the polarizing plate of the present invention (planar, 23 ℃) is preferably 20.0N/25mm or less, more preferably 15.0N/25mm or less, still more preferably 10.0N/25mm or less, and particularly preferably 6.0N/25mm or less. The adhesion to glass (curved surface, 23 ℃) is preferably 20.0N/25mm or less, more preferably 15.0N/25mm or less, still more preferably 10.0N/25mm or less, and particularly preferably 6.0N/25mm or less.

When the upper limit of the glass adhesion of each pair is within the above range, the polarizing plate can be easily reworked from the display panel when the sticking of the polarizing plate occurs or is found in the process of manufacturing the curved image display panel. In the present invention, from the viewpoint of reworkability, the adhesion to glass (flat surface, 23 ℃ C.) and the adhesion to glass (curved surface, 23 ℃ C.) are preferably 20.0N/25mm or less.

When the polarizing plate of the present invention includes an adhesive layer, the adhesive strength (planar, 23 ℃) to glass is 20.0N/25mm or less, further 15.0N/25mm or less, particularly 10.0N/25mm, particularly 6.0N/25mm or less, and further particularly 4.0N/25mm or less, and therefore floating and peeling can be suppressed because formula (1) is satisfied.

The above adhesion to glass (planar, 23 ℃) is: a value measured by attaching a polarizing plate cut into a predetermined size to a flat glass substrate via an adhesive layer thereof, subjecting the resulting laminate to autoclave treatment, standing the laminate at 23 ℃ and 50% RH for 24 hours, and then peeling the polarizing plate from the glass substrate at a predetermined speed in a 180 ° direction. The adhesion to glass (curved surface, 23 ℃) was: the polarizing plate was bonded to a glass plate to obtain a test piece, the test piece was fixed so that the test piece was processed over a metal plate having a curvature radius of 2500mm, and the test piece was left to stand at 23 ℃ and 50% RH for 24 hours in this state, and then the polarizing plate was peeled off to measure the value.

The more detailed measurement method of the glass adhesion force (flat surface, 23 ℃) and the glass adhesion force (curved surface, 23 ℃) is as described in the examples below.

In the polarizing plate of the present invention, the adhesive strength to glass of the adhesive layer measured in a planar state after drying at 80 ℃ for 250 hours (hereinafter sometimes referred to as "adhesive strength to glass (planar, 80 ℃)") is preferably 7.0N/25mm or more, more preferably 9.0N/25mm or more, and still more preferably 11.0N/25mm or more. In the polarizing plate of the present invention, the adhesive strength to glass of the adhesive layer (hereinafter sometimes referred to as "adhesive strength to glass (curved surface, 80 ℃)") measured in a curved state after drying at 80 ℃ for 250 hours is preferably 8.0N/25mm or more, more preferably 10.0N/25mm or more, and still more preferably 12.0N/25mm or more. Further, the adhesive force is increased, and the test piece is broken at the time of measurement, and the adhesive force of each pair of glasses described above measured after 250 hours in a dry environment at 80 ℃ may not be measured as a numerical value, which is a particularly preferable embodiment of the present invention.

When the adhesive force of each pair of glasses measured after 250 hours in a dry environment at 80 ℃ is such a value, sufficient adhesive force to the display panel can be secured even in use for a long period of time and/or in a high-temperature environment, and peeling or lifting from the display panel in a curved state is less likely to occur. In the polarizing plate having the above-mentioned adhesion force to glass (plane, 23 ℃), it is particularly advantageous for the polarizing plate of the present invention to set the adhesion force to glass in each pair as measured after 250 hours in a dry environment at 80 ℃.

The glass adhesion (flat surface, 80 ℃) is preferably higher by 5.0N/25mm or more, more preferably higher by 7.0N/25mm or more, and particularly preferably higher by 10.0N/25mm or more than the glass adhesion (flat surface, 23 ℃). The adhesive strength to glass (curved surface, 80 ℃) is preferably 5.0N/25mm or more, more preferably 7.0N/25mm or more, and particularly preferably 10.0N/25mm or more higher than the adhesive strength to glass (curved surface, 23 ℃). In the polarizing plate having the above-mentioned adhesion force to glass (plane, 23 ℃) in a certain range, if the adhesion force to each pair of glasses measured after 250 hours in a dry environment at 80 ℃ is higher by 5.0N/25mm or more than the adhesion force to each pair of glasses measured at 23 ℃ and 50% RH, not only the adhesion force necessary for use in an environment of normal temperature to low temperature for adhesion to an image display element can be secured in the initial state of adhesion after adhesion to the image display element, but also rework can be easily performed. Further, even when the display panel is exposed to heat from a light source for a long period of time, transported in a high-temperature and high-humidity environment, or used for a long period of time and/or in a high-temperature environment, sufficient adhesion to the display panel can be secured, and peeling or lifting from the display panel in a curved state is less likely to occur.

The upper limit of the difference between the glass adhesion (flat surface, 80 ℃) and the glass adhesion (flat surface, 23 ℃) and the difference between the glass adhesion (curved surface, 80 ℃) and the glass adhesion (curved surface, 23 ℃) are not particularly limited, and is usually 20.0N/25mm or less.

The glass adhesion (curved surface, 80 ℃) is preferably higher by 5.0N/25mm or more, more preferably higher by 7.0N/25mm or more, and particularly preferably higher by 10.0N/25mm or more than the glass adhesion (flat surface, 23 ℃). When the difference between the glass adhesion (curved surface, 80 ℃) and the glass adhesion (flat surface, 23 ℃) is within the above range, the bonding and rework in the flat state are easy, and a sufficient adhesion to the display panel can be secured even in use for a long period of time and/or under a high temperature environment after the curved surface is formed, and the peeling and lifting from the display panel in the curved surface state are less likely to occur.

The above-mentioned glass adhesion force (flat surface, 80 ℃) and glass adhesion force (curved surface, 80 ℃) were measured by the same methods as those for the above-mentioned glass adhesion force (flat surface, 23) and glass adhesion force (curved surface, 23 ℃) except that the test piece was left to stand at 80 ℃ for 250 hours in a dry atmosphere.

The adhesion strength to glass of the adhesive layer varies depending on the kind of the components constituting the adhesive layer, the content ratio thereof, the forming conditions (drying, active energy ray irradiation conditions), the thickness after formation, and the like, and therefore the components constituting the adhesive layer, the content ratio, the forming conditions, the thickness, and the like may be appropriately selected depending on the desired adhesion strength to glass. Specifically, for example, the adhesion of the adhesive layer to glass can be improved by using an acrylic resin as a constituent of the adhesive constituting the adhesive layer, blending a silane compound, and increasing the layer thickness of the adhesive layer. The adhesion to glass can be controlled to a desired value by changing the kind and ratio of the monomers constituting the acrylic resin and the kind and content of the silane compound.

< polarizing film >

The polarizing film that can constitute the polarizing plate of the present invention is a film having a function of extracting linearly polarized light from incident natural light, and for example, a film in which a dichroic dye is oriented and adsorbed on a polyvinyl alcohol resin film can be used. As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film, a polyvinyl acetate resin may be used after saponification. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith (for example, an ethylene-vinyl acetate copolymer). Examples of other monomers copolymerizable with vinyl acetate include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.

The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like modified with aldehydes can be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.

Such a polyvinyl alcohol resin can be used as a raw film for a polarizing film after being formed into a film. The method for forming the film of the polyvinyl alcohol resin is not particularly limited, and the film can be formed by a conventionally known method. The film thickness of the green film containing the polyvinyl alcohol resin is not particularly limited, but is, for example, 10 to 150 μm, preferably 15 to 100 μm, and more preferably 20 to 80 μm, in view of easy stretching.

The polarizing film is generally manufactured through the following processes: a step of uniaxially stretching a polyvinyl alcohol resin film such as a polyvinyl alcohol film; a step of adsorbing a dichroic pigment by dyeing a polyvinyl alcohol resin film with the dichroic pigment; treating the dichroic pigment-adsorbed polyvinyl alcohol resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution. From an industrial viewpoint, the stretched and dyed polyvinyl alcohol film thus produced is preferably used as a polarizing film. The stretched and dyed polyvinyl alcohol film is a stretched polyvinyl alcohol film containing (adsorbing) a dichroic dye, and the stretching ratio is as follows.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing of the dichroic pigment. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or in boric acid treatment. Further, the uniaxial stretching may be performed in the above-mentioned plurality of stages. In the case of uniaxial stretching, stretching may be performed uniaxially between rolls having different peripheral speeds, or stretching may be performed uniaxially using a hot roll. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol resin film is swollen with a solvent. The stretching ratio is preferably 8 times or less, more preferably 7.5 times or less, and still more preferably 7 times or less, from the viewpoint of suppressing deformation of the polarizing film. In addition, the stretch ratio is usually 4.5 times or more from the viewpoint of exhibiting the function as a polarizing film.

As a method for dyeing the polyvinyl alcohol resin film with the dichroic pigment, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic pigment is cited. Iodine or a dichroic dye may be used as the dichroic pigment. Dichroic dyes include, for example: direct RED 39 and the like dichroic direct dyes containing a disazo compound, and dichroic direct dyes containing a trisazo compound, a tetraazo compound, and the like. The polyvinyl alcohol resin film is preferably subjected to a treatment of immersing in water before the dyeing treatment.

When iodine is used as the dichroic dye, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide to dye the film is generally used. The content of iodine in the aqueous solution is usually 0.01 to 1 part by mass per 100 parts by mass of water, and the content of potassium iodide is usually 0.5 to 20 parts by mass per 100 parts by mass of water. When iodine is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ℃, and the immersion time (dyeing time) in the aqueous solution is usually 20 to 1800 seconds.

When a dichroic dye is used as the dichroic pigment, it is generally used inA method for dyeing a polyvinyl alcohol resin film by immersing the film in an aqueous solution containing a water-soluble dichroic dye. The content of the dichroic dye in the aqueous solution is usually 1X 10 per 100 parts by mass of water^-4About 10 parts by mass, preferably about 1X 10^-3About 1 part by mass, more preferably about 1X 10^-3～1×10^-2And (4) parts by mass. The aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. When a dichroic dye is used as the dichroic dye, the temperature of an aqueous dye solution used for dyeing is usually 20 to 80 ℃, and the immersion time (dyeing time) in the aqueous dye solution is usually 10 to 1800 seconds.

The boric acid treatment after dyeing with the dichroic pigment can be performed by immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The amount of boric acid in the aqueous solution containing boric acid is usually 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic pigment, the aqueous solution containing boric acid preferably contains potassium iodide. The amount of potassium iodide in the aqueous solution containing boric acid is usually 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the aqueous solution containing boric acid is usually 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ℃ or higher, preferably 50 to 85 ℃, and more preferably 60 to 80 ℃.

The polyvinyl alcohol resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment is performed by, for example, immersing the boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually 5-40 ℃, and the dipping time is usually 1-120 seconds. After washing with water, the polarizing film was dried. The drying treatment may be carried out by using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually 30 to 100 ℃, preferably 40 to 95 ℃, and more preferably 50 to 90 ℃. The drying time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

In this manner, the polyvinyl alcohol resin film was uniaxially stretched, dyed with a dichroic dye, and subjected to boric acid treatment to obtain a polarizing film. The thickness of the polarizing film may be set to 5 to 40 μm, for example.

Since the coated film polarizing film has a smaller dimensional change rate than a conventionally known polarizing film obtained by stretching a polyvinyl alcohol resin film, the use of the coated film polarizing film can suppress the dimensional change of the polarizing plate during long-term use and/or use in a high-temperature environment. In addition, it can contribute to making the polarizing plate thin, and is preferable in the present invention. As the coating type thin film polarizing film, for example, the coating type thin film polarizing films exemplified in japanese patent laid-open nos. 2012 and 58381, 2013 and 37115, 2012/147633, and 2014/091921 can be used.

< protective layer >

In a preferred embodiment, the polarizing plate of the present invention has a protective layer laminated on one or both surfaces of the polarizing film. The protective layer contributes to, for example, prevention of shrinkage and expansion of the polarizing film, prevention of deterioration of the polarizing film due to temperature, humidity, ultraviolet rays, and the like, and thus it is preferable that the polarizing plate of the present invention has the protective layer.

As a material for forming the protective layer, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. Examples thereof include: polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetylcellulose and triacetylcellulose; acrylic polymers such as polymethyl methacrylate; styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin); a polycarbonate-series polymer. Polyolefin polymers such as polyethylene, polypropylene, ring system or norbornene structure-containing polyolefin, and ethylene-propylene copolymers; a vinyl chloride polymer; amide polymers such as nylon and aromatic polyamide; an imide polymer; a sulfone-based polymer; a polyether sulfone-based polymer; a polyether ether ketone polymer; polyphenylene sulfide-based polymer; a vinyl alcohol polymer; a vinylidene chloride polymer; a vinyl butyral based polymer; an aryl ester polymer; a polyoxymethylene-based polymer; an epoxy polymer; or a mixture of the above polymers, etc. may be given as an example of the polymer forming the protective layer. The protective layer may be a cured layer formed of a thermosetting or ultraviolet-curable resin such as an acrylic, urethane, acrylic urethane, epoxy, or silicone resin. Among these, a material containing a hydroxyl group reactive with an isocyanate crosslinking agent is preferable, and a cellulose-based polymer is particularly preferable. The thickness of the protective layer is not particularly limited, but is usually 500 μm or less, preferably 1 to 300 μm, more preferably 5 to 200 μm, and still more preferably 30 to 100 μm. The protective layer may be formed of a transparent protective film or the like to which an optical compensation function is added. The thickness of the outer protective layer laminated on the back surface side of the polarizing film is preferably the same as the thickness of the inner protective layer laminated on the viewing side of the polarizing film or the outer protective layer is thicker than the inner protective layer. In this way, the outer and inner protective layers are prevented from warping particularly when heat is applied to the polarizing plate, or warping to the lower side of rigidity makes it difficult for peeling or lifting from the display panel to occur. This is particularly preferred for concave side applications.

Since the shrinkage of the polarizing film can be suppressed by increasing the rigidity of the protective layer adjacent to the polarizing film, the dimensional change of the polarizing plate can be suppressed by controlling the rigidity of the protective layer. The rigidity is defined as the rigidity obtained by multiplying the tensile elastic modulus at room temperature (23 ℃) of the film used for the protective layer (hereinafter referred to as the 23 ℃ elastic modulus) by the film thickness, and the rigidity obtained by multiplying the tensile elastic modulus at 80 ℃ of the film (hereinafter referred to as the 80 ℃ elastic modulus) by the film thickness. In particular, by increasing the rigidity obtained by multiplying the elastic modulus at 80 ℃ by the film thickness, the dimensional change of the polarizing plate in a high-temperature environment can be suppressed. For example, cellulose polymers represented by triacetyl cellulose preferably have an elastic modulus at 23 ℃ of 3000 to 5000MPa and an elastic modulus at 80 ℃ of 2000 to 4000MPa, acrylic polymers represented by polymethyl methacrylate preferably have an elastic modulus at 23 ℃ of 2000 to 4000MPa and an elastic modulus at 80 ℃ of 800 to 2500MPa, and polyolefin polymers having a norbornene structure preferably have an elastic modulus at 23 ℃ of 2000 to 4000MPa and an elastic modulus at 80 ℃ of 1500 to 3000 MPa.

The surface of the protective layer that is not adhered to the polarizing film may have a surface treatment layer, and may have, for example: optical layers such as hard coat layers, antireflection layers, antiblocking layers, antiglare layers, or diffusion layers.

The hard coat layer is formed to prevent scratches and the like on the surface of the polarizing plate, and may be formed by, for example, attaching a cured film having excellent hardness, sliding properties, and the like, which is formed from an ultraviolet-curable resin such as an acrylic resin and a silicone resin, to the surface of the protective layer. The antireflection layer is intended to prevent reflection of external light on the surface of the polarizing plate, and can be formed by forming an antireflection film according to the related art, or the like. In addition, the anti-blocking layer is intended to prevent adhesion to adjacent layers.

The anti-glare layer is formed by imparting a fine uneven structure to the surface of the protective layer by, for example, a sandblasting method, a roughening method by an embossing method, a blending method of transparent fine particles, or the like, in order to prevent external light from reflecting on the surface of the polarizing plate and to prevent the viewing of transmitted light through the polarizing plate. Examples of the fine particles contained to form the fine uneven surface structure include: transparent fine particles such as inorganic fine particles having conductivity and made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle diameter of 0.5 to 50 μm, and organic fine particles made of a crosslinked or uncrosslinked polymer or the like. When the surface fine uneven structure is formed, the content of the fine particles is usually 2 to 50 parts by mass, preferably 5 to 25 parts by mass, per 100 parts by mass of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expansion function or the like) for diffusing light transmitted through the polarizing plate to expand the viewing angle or the like. The protective layer may contain known additives as needed. Examples of additives include: ion scavenger, antioxidant, sensitizing assistant, light stabilizer, tackifier, thermoplastic resin, filler, flow regulator, plasticizer, defoaming agent, pigment, antistatic agent, ultraviolet absorber, etc.

The antireflection layer, the antiblocking layer, the diffusion layer, the antiglare layer, and the like may be provided on the protective layer itself and integrated with each other, or may be provided separately as an optical layer that is not integrated with the protective layer.

< adhesive layer >

The polarizing film and the protective layer are usually bonded via an adhesive. The adhesive for bonding the polarizing film and the protective layer is not particularly limited, and from the viewpoint of thinning the adhesive layer formed, an aqueous adhesive, that is, an adhesive in which an adhesive component is dissolved in water or an adhesive in which an adhesive component is dispersed in water, may be mentioned. For example, an adhesive containing a polyvinyl alcohol resin or a urethane resin can be used as the adhesive component. When the polarizing film has protective layers on both sides, the adhesives used for the bonding may be the same or different.

When the polyvinyl alcohol resin is contained as the adhesive component, the polyvinyl alcohol resin may be a modified polyvinyl alcohol resin such as a carboxyl group-modified polyvinyl alcohol, an acetoacetyl group-modified polyvinyl alcohol, a hydroxymethyl group-modified polyvinyl alcohol, or an amino group-modified polyvinyl alcohol, in addition to a partially saponified polyvinyl alcohol or a completely saponified polyvinyl alcohol. Generally, an adhesive containing a polyvinyl alcohol resin as an adhesive component is prepared as an aqueous solution of the polyvinyl alcohol resin. The concentration of the polyvinyl alcohol resin in the adhesive is usually 1 to 10 parts by mass, preferably 1 to 5 parts by mass, per 100 parts by mass of water.

In the adhesive containing a polyvinyl alcohol resin as an adhesive component, a curable component such as glyoxal or a water-soluble epoxy resin and/or a crosslinking agent is preferably contained in order to improve the adhesiveness. As the water-soluble epoxy resin, for example, there can be suitably used: a polyamidoamine epoxy resin obtained by reacting epichlorohydrin with a polyamidoamine obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid. Commercially available products of the polyamide polyamine epoxy resin include: "Sumirez Resin 650" (manufactured by Sumika Chemtex Co., Ltd.), "Sumirez Resin 675" (manufactured by Sumika Chemtex Co., Ltd.), "WS-525" (manufactured by Nippon PMC Co., Ltd.), and the like. The amount of these curable components and/or crosslinking agents added (in the case of both of them, the total amount thereof) is usually 1 to 100 parts by mass, preferably 1 to 50 parts by mass, based on 100 parts by mass of the polyvinyl alcohol resin. When the amount of the curable component and/or the crosslinking agent added is within the above range, the adhesiveness is improved, and an adhesive layer exhibiting good adhesiveness can be formed.

When the adhesive contains a urethane resin as an adhesive component, it is preferable to use: a mixture of a polyester ionomer urethane resin and a compound having a glycidoxy group. Here, the polyester ionomer urethane resin is a urethane resin having a polyester skeleton and a small amount of ionic components (hydrophilic components) introduced into the skeleton. The ionomer urethane resin is directly emulsified in water to form an emulsion without using an emulsifier, and thus is suitable as an aqueous adhesive. Polyester ionomer urethane resins are known per se, and examples of polymer dispersants for dispersing a phenol resin in an aqueous medium are described in, for example, japanese patent laid-open nos. 7-97504, and 2005-70140 and 2005-208456 disclose a form in which a cycloolefin resin film is bonded to a polarizing film containing a polyvinyl alcohol resin using a mixture of a polyester ionomer urethane resin and a compound having an glycidoxy group as an adhesive.

The application of the adhesive to the polarizing film and/or the protective layer (protective film) attached to the polarizing film can be carried out by a known method, and for example, the following can be used: casting, wire bar coating, gravure coating, comma coater, doctor blade, die coating, dip coating, spraying, and the like. The casting method is a method of spreading a film as an object to be coated by running down an adhesive on the surface of the film while moving the film in a substantially vertical direction, a substantially horizontal direction, or an oblique direction therebetween. After the adhesive is applied, the polarizing film and the protective layer to be bonded to the polarizing film are stacked, and the film is bonded by being sandwiched by a nip roller or the like. The lamination of the film using the nip roller may be, for example: a method of applying an adhesive and then pressing the adhesive with a roller or the like to uniformly spread the adhesive; and a method in which after the adhesive is applied, the adhesive is pressed between rollers to spread the adhesive. In this case, the roller used may be made of metal, rubber, or the like. When the film is extruded and spread between a plurality of rollers, the plurality of rollers may be made of the same material or different materials.

In order to improve the adhesiveness, the surface of the polarizing film to be bonded to the protective layer may be subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, or saponification treatment. The saponification treatment may be carried out by immersing the substrate in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

After the lamination, the adhesive is cured by drying, thereby obtaining a polarizing plate. The drying treatment is carried out by, for example, spraying hot air, and the temperature thereof is usually within a range of 40 to 100 ℃, preferably within a range of 60 to 100 ℃. In addition, the drying time is usually 20 to 1200 seconds.

The thickness of the adhesive layer formed of the dried adhesive is usually 0.001 to 5 μm, preferably 0.01 to 2 μm, and more preferably 0.01 to 1 μm. When the thickness of the adhesive layer is within the above range, sufficient adhesiveness can be secured, and the adhesive layer is also preferable in appearance and can contribute to thinning of the polarizing plate, and thus the polarizing plate of the present invention is suitable.

After the drying, the curing may be performed at a temperature of room temperature or higher for at least half a day, preferably several days or higher, to obtain a sufficient adhesive strength. The curing temperature is preferably in the range of 30 to 50 ℃, and more preferably in the range of 35 to 45 ℃. When the aging temperature is within the above range, so-called "wind-up (wind きまり)" in a roll state is less likely to occur. The humidity during the aging is not particularly limited, and may be in the range of 0 to 70% RH. The curing time is usually 1 to 10 days, preferably 2 to 7 days.

Further, a photocurable adhesive may be used as the adhesive. Examples of the photocurable adhesive include: a mixture of a photocurable epoxy resin and a photocationic polymerization initiator; a mixture of a photocurable acrylic resin and a photo radical polymerization initiator. When a photocurable adhesive is used, the photocurable adhesive is cured by irradiation with active energy rays. The light source of the active energy ray is not particularly limited, and active energy rays having an emission distribution at a wavelength of 400nm or less are preferable, and specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultrahigh-pressure mercury lamps, chemical lamps, black lamps, microwave-excited mercury lamps, metal halide lamps, and the like are preferable.

The irradiation intensity of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited, and the irradiation intensity in a wavelength region effective for activation of the polymerization initiator is preferably 0.1 to 6000mW/cm²More preferably 10 to 1000mW/cm²More preferably 20 to 500mW/cm². When the irradiation intensity is within the above range, the reaction time can be secured, and yellowing of the epoxy resin and deterioration of the polarizing film due to heat radiated from the light source and heat generation of the photocurable adhesive during curing can be suppressed. The light irradiation time of the photocurable adhesive is not particularly limited, and may be appropriately selected depending on the photocurable adhesive to be cured, and the cumulative light amount expressed as the product of the irradiation intensity and the irradiation time is preferably set to 10 to 10000mJ/m²More preferably 50 to 1000mJ/m²More preferably 80 to 500mJ/m². When the cumulative light amount of the photocurable adhesive is within the above range, a sufficient amount of active species derived from the polymerization initiator is generated to more reliably advance the curing reaction, and the irradiation time does not become excessively long, so that good productivity can be maintained.

When the photocurable adhesive is cured by irradiation with an active energy ray, it is preferable to cure the photocurable adhesive under conditions such that various functions of the polarizing plate, for example, the polarization degree, transmittance, and hue of the polarizing film and the transparency of various films constituting the protective layer and the optical layer, are not deteriorated.

< optical layer >

The polarizing plate of the present invention may further include optical layers such as a retardation film, a viewing angle compensation film, and a brightness enhancement film, if necessary.

Examples of the retardation film include: birefringent films obtained by uniaxially or biaxially calendering polymer materials, alignment films of liquid crystal polymers, and retardation films obtained by supporting alignment layers of liquid crystal polymers with films. The stretching treatment can be performed by, for example, a roll stretching method, a long gap stretching method, a tenter stretching method, a tubular stretching method, or the like. The stretching ratio is usually 1.1 to 3 times in the case of uniaxial stretching. The thickness of the retardation film is not particularly limited, but is usually 10 to 200. mu.m, preferably 20 to 100. mu.m.

Examples of the polymer material include: polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyphenylene sulfide, polyphenylene ether, polyallyl sulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin having a norbornene structure, polyvinyl chloride, a cellulose polymer, or a binary or ternary copolymer, graft copolymer, or mixture thereof. These polymer materials are stretched to form an oriented product (stretched film).

Examples of the liquid crystal polymer include: various polymers of main chain type or side chain type in which a conjugated linear atomic group (mesogen) for imparting liquid crystal alignment property is introduced into the main chain or side chain of the polymer. Specific examples of the main chain type liquid crystal polymer include: examples of the polymer include a polyester-based liquid crystal polymer, a discotic polymer, and a cholesteric polymer having a structure in which mesogenic groups are bonded to a spacer portion for imparting flexibility. Specific examples of the side chain type liquid crystal polymer include: and side chain type liquid crystal polymers having a polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton and a mesogenic portion including a para-substituted cyclic compound unit as a side chain, which has a nematic orientation imparting property via a spacer portion including a conjugated atomic group. These liquid crystal polymers are treated, for example, as follows: a solution of a liquid crystal polymer is spread on an alignment surface of a material obtained by rubbing a surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, a material obtained by obliquely depositing silicon oxide, or the like, and then heat-treated.

The retardation film may be one having a retardation according to the intended use, such as one for compensating for coloring due to birefringence of various wave plates or liquid crystal layers, or for compensating for a viewing angle, or may be one in which 2 or more kinds of retardation films are laminated to control optical characteristics such as retardation.

The viewing angle compensation film is a film that enlarges the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a direction slightly inclined with respect to the screen. As such a viewing angle compensation film, for example, there are included: a retardation film, an alignment film of a liquid crystal polymer or the like, a film in which an alignment layer of a liquid crystal polymer or the like is supported on a transparent substrate, and the like. While a polymer film having birefringence uniaxially stretched in the in-plane direction is used as a general retardation film, a retardation film used as a viewing angle compensation film uses: a polymer film having birefringence biaxially stretched in a plane direction; biaxially oriented films such as polymer films having birefringence in which the refractive index in the thickness direction is controlled, and obliquely oriented films, which are uniaxially stretched in the plane direction and also stretched in the thickness direction. Examples of the obliquely oriented film include: an obliquely oriented film obtained by bonding a heat-shrinkable film to a polymer film and stretching or/and shrinking the polymer film under the action of a shrinking force generated by heating; and an oblique alignment film for obliquely aligning the liquid crystal polymer. As a raw material polymer of the retardation film, a polymer for the purpose of preventing coloring or the like due to a change in the angle of view due to retardation from a liquid crystal cell, expanding the angle of view with good resolution, or the like, similar to the polymer described in the retardation film can be appropriately selected and used.

In addition, from the viewpoint of achieving a large viewing angle with good resolution, it is preferable to use an alignment layer of a liquid crystal polymer, and particularly preferable to use a viewing angle compensation film in which an optically anisotropic layer composed of an inclined alignment layer of a discotic liquid crystal polymer is supported by a triacetyl cellulose film.

A polarizing plate obtained by bonding a polarizing plate to a brightness enhancement film is generally used by being disposed on the back side of a liquid crystal cell. The brightness enhancement film exhibits a property of reflecting linearly polarized light having a predetermined polarization axis or circularly polarized light having a predetermined direction when natural light is incident due to a backlight of a liquid crystal display device or the like, reflection from the back side, or the like, and transmitting other light, and the polarizing plate obtained by laminating the brightness enhancement film and the polarizing plate obtains transmitted light having a predetermined polarization state by allowing light from a light source such as a backlight to be incident, and light other than the predetermined polarization state is reflected without being transmitted. The light reflected by the brightness enhancement film surface is further inverted by a reflection layer or the like provided on the rear side thereof, and then, the light is again incident on the brightness enhancement film, and a part or all of the light is transmitted as light in a predetermined polarization state, whereby an increase in the amount of light transmitted through the brightness enhancement film is achieved, and the amount of light usable for liquid crystal image display or the like is increased by supplying polarized light which is not easily absorbed by the polarizing film, whereby the luminance can be improved. That is, when light enters from the back side of the liquid crystal cell through the polarizing film without using a brightness enhancement film by a backlight or the like, the light having a polarization direction different from the polarization axis of the polarizing film is almost absorbed by the polarizing film and cannot pass through the polarizing film. That is, although the polarizing film used has different characteristics, about 50% of light is absorbed by the polarizing film, and accordingly, the amount of light available for liquid crystal image display or the like is reduced, and the image becomes dark. The brightness enhancement film is configured such that light having a polarization direction that can be absorbed by the polarizing film is once reflected by the brightness enhancement film without being incident on the polarizing film, and then is inverted by a reflection layer or the like provided on the rear side thereof and is incident on the brightness enhancement film again, and the above-described process is repeated, and only polarized light having a polarization direction that can pass through the polarizing film, which is reflected and inverted between the both, is transmitted and supplied to the polarizing film, whereby light such as backlight can be effectively used for image display of a liquid crystal display device, and a screen can be brightened.

The polarizing plate of the present invention can be produced, for example, as follows: the polarizing film is bonded with a protective layer using an adhesive, and an adhesive layer is formed on the surface of the protective layer on the side bonded with the image display element. When the polarizing plate of the present invention further includes an optical layer, for example, various films constituting the optical layer may be bonded to the protective layer with an adhesive, and an adhesive layer may be formed on the surface opposite to the surface bonded to the protective layer. The polarizing plate obtained by laminating the films and layers constituting the polarizing plate is curved so as to have a desired radius of curvature before being bonded to an image display element, whereby the polarizing plate of the present invention can be obtained. Further, the image display device may be curved after being bonded to the image display element.

For bonding to an image display element, for example, when the polarizing plate is used for a curved liquid crystal display panel, the polarizing plate of the present invention may be bonded to a liquid crystal cell as an image display element via an adhesive layer. In the case of using the polarizing plate for a curved organic EL panel, the polarizing plate of the present invention may be bonded to a viewing-side display surface of an organic EL display element as an image display element via an adhesive layer.

For the curving of the polarizing plate, for example, in the case of a liquid crystal display panel, the following method can be used: a method of fixing the laminate of the image display element and the concave-side and convex-side polarizing plates manufactured as described above to a frame in a state of being bent at a predetermined radius of curvature and placing the laminate on a backlight unit; or a method in which the laminate is placed on a backlight unit curved with a predetermined radius of curvature and then pressed from above with a frame.

The polarizing plate of the present invention can be used as a polarizing plate for a curved image display panel such as a curved liquid crystal panel or a curved organic EL panel, and particularly as a polarizing plate for a curved liquid crystal display panel. In the curved image display panel, a compressive stress is continuously generated due to the bending of the image display panel. It is considered that the compressive stress is greater on the concave surface side (viewing side), and therefore the polarizing plate located on the concave surface side is likely to undergo dimensional change, while the image display element to which the polarizing plate is bonded is generally sandwiched between glass substrates, and therefore dimensional change is unlikely to occur, and a difference in shrinkage ratio is likely to occur between the concave surface side polarizing plate and the image display element. Therefore, the peeling and lifting of the polarizing plate are particularly likely to occur on the concave surface side of the curved image display panel. The polarizing plate of the present invention can be used as either a concave-side polarizing plate or a convex-side polarizing plate constituting a curved image display panel, and has a high effect of suppressing peeling and floating in a curved state, and is therefore particularly suitable as a concave-side polarizing plate to be attached to a concave side of an image display panel. That is, in one embodiment of the present invention, there is provided a curved image display panel including a concave-side polarizing plate and a convex-side polarizing plate, the concave-side polarizing plate being the polarizing plate of the present invention. In addition, in another embodiment of the present invention, there is provided a curved image display panel including a concave-side polarizing plate and a convex-side polarizing plate, the concave-side polarizing plate and the convex-side polarizing plate being the polarizing plate of the present invention.

When the polarizing plate of the present invention is used in a liquid crystal display panel, the convex-side polarizing plate and the concave-side polarizing plate are arranged so that the absorption axis directions (stretching directions) of the respective polarizing films included in these polarizing plates are orthogonal to each other. For example, as shown in fig. 4, when the absorption axis direction of the polarizing film included in the concave-side polarizing plate is the horizontal direction, the absorption axis direction of the polarizing film included in the convex-side polarizing plate is the vertical direction. As shown in fig. 5, when the absorption axis direction of the polarizing film included in the concave-side polarizing plate is the vertical direction, the absorption axis direction of the polarizing film included in the convex-side polarizing plate is the horizontal direction. The absorption axis direction of the polarizing film included in the concave-side polarizing plate may be a vertical direction, may be a horizontal direction, and may be an angular direction of 45 ° with respect to the horizontal direction. In the present invention, it has been found that in most of the products of image display panels, the absorption axis direction of the polarizing film included in the concave-side polarizing plate is the horizontal direction, and in particular, in this case, deformation such as shrinkage of the polarizing plate is likely to occur, and peeling or lifting of the polarizing plate is likely to occur. According to the polarizing plate of the present invention, even if the absorption axis direction is the horizontal direction, scratches on the surface of the polarizing plate can be suppressed, and the above problem can be solved.

In addition, the polarizing plate of the present invention can be suitably used for curved image display panels having various screen sizes. For example, the curved image display panel can be used for a curved image display panel having a screen size of 5 inches (horizontal length: 100 to 150mm), 10 inches (horizontal length: 200 to 250mm), 17 inches (horizontal length: 320 to 400mm), 32 inches (horizontal length: 680 to 720mm), 40 inches (horizontal length: 860 to 910mm), 46 inches (horizontal length: 980 to 1030mm), 55 inches (horizontal length: 1180 to 1230mm), 65 inches (horizontal length: 1400 to 1450mm), 75 inches (horizontal length: 1600 to 1700mm), or 85 inches (horizontal length: 1800 to 1900 mm). The larger the screen size is, the larger the size of each component is, and when the screen is curved, a compressive stress acts on the concave-side polarizing plate, and the sizes of the polarizing plate and the image display element are not matched with each other, so that the peeling and floating of the polarizing plate are particularly likely to occur. In addition, in the image display panel having an aspect ratio of 3: 4 of the screen, peeling and lifting of the polarizing plate are not easily generated, but in the image display panel having a lateral length of 9: 13 to 9: 23 of the screen, preferably 9: 15 or more, more preferably 9: 19 or less, for example 9: 16 or 9: 21, a compression stress acts on the polarizing plate on the concave side during curving, and the sizes of the polarizing plate and the image display element are not uniform, so that peeling and lifting of the polarizing plate are particularly easily generated. The polarizing plate of the present invention has a high effect of suppressing peeling and floating in a curved state, and thus can be suitably used as a polarizing plate for curved image display panels of various screen sizes as described above, particularly large screen sizes or horizontal lengths.

The curved image display panel of the present invention including the polarizing plate of the present invention is excellent in the effect of suppressing peeling and floating of the polarizing plate from the image display panel for a long period of time and/or under a warm environment.

Examples

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

1. Production of polarizing film

A60 μm thick polyvinyl alcohol film (trade name "VF-PE # 6000" manufactured by Kuraray, Ltd.) having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more was immersed in pure water at 30 ℃ and then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30 ℃. Thereafter, the impregnation was carried out at 56.5 ℃ in an aqueous solution having a potassium iodide/boric acid/water mass ratio of 12/5/100. Then, the film was washed with pure water at 8 ℃ and dried at 80 ℃ to obtain a polarizing film with iodine adsorbed and oriented on the polyvinyl alcohol film. The stretching was mainly performed in iodine dyeing and boric acid treatment, and the total stretching magnification was 6.0 times. The thickness of the polarizing film thus obtained was 22 μm.

2. Preparation and preparation of protective layer (protection preparation)

Various protective layers (protective films) were produced or prepared as described below.

(1) Production of acrylic resin (2-A)

A methacrylic resin 70 mass% and a rubber particle 30 mass% were mixed by a high speed mixer, and 100 mass% of the mixture was added with a benzotriazole ultraviolet absorber 2 mass%, and the mixture was melt-kneaded by a twin screw extruder to prepare pellets. Feeding the granules into a reactor

The resulting film was extruded through a T-die having a set temperature of 275 ℃ by a single-screw extruder, and cooled by sandwiching the film between two polishing rolls having mirror surfaces, to obtain an acrylic resin film (2-A) having a thickness of 80 μm.

As the methacrylic resin, a copolymer of methyl methacrylate/methyl acrylate at 96%/4% (mass ratio) was used. The rubber particles used were elastomer particles having a three-layer structure, the innermost layer was composed of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of allyl methacrylate, the intermediate layer was composed of a soft elastomer obtained by polymerizing butyl acrylate as a main component, further styrene and a small amount of allyl methacrylate, and the outermost layer was composed of a hard polymer obtained by polymerizing methyl methacrylate with a small amount of ethyl acrylate, and the average particle diameter of the elastomer particles up to the elastomer serving as the intermediate layer was 240 nm. In the rubber particles, the total mass of the innermost layer and the intermediate layer was 70% of the total mass of the particles.

(2) Acrylic resin film with hard coat layer (2-B)

A hard coat treatment was performed on the acrylic resin film (2-A). The hard coat treatment was carried out by applying a treatment solution (pentaerythritol triacrylate: 42.5 parts by mass, IRGACURE 184: 0.25 parts by mass, silicone (leveling agent): 0.1 parts by mass, silica (average particle diameter 1 μm): 12 parts by mass, surface methacryloyl-modified silica (surface organic component: 4.05X 10)^-3g/m²): 7.5 parts by mass of toluene: 34 parts by mass), and then, the resultant was dried and irradiated with ultraviolet rays using an ultraviolet irradiator. Thus, an acrylic resin film (2-B) having a hard coat layer with a thickness of 5 μm (overall thickness: 85 μm) was obtained.

(3) TAC film (2-C)

A triacetyl cellulose film "KC 6 UAW" (thickness 60 μm) manufactured by Konica Minolta Opto Co., Ltd was used as a TAC film (2-C).

(4) TAC film (2-D)

A hard coat treatment was performed on the TAC film (2-C) in the same manner as in (2-B). Thus, a TAC film (2-D) having a hard coat layer with a thickness of 5 μm (overall thickness: 65 μm) was obtained.

(5) COP production (2-E)

A cyclic polyolefin biaxially stretched resin FILM "ZEONOR FILM ZB 12" (52 μm in thickness) available from Nippon corporation was used as the COP FILM (2-E).

3. Preparation of the adhesive

A solvent-free type ultraviolet curable adhesive obtained by mixing the following compounding ingredients was used as the adhesive. In addition,% represents a content (mass%) of the entire adhesive assuming 100 mass%.

3, 4-epoxycyclohexylmethyl-3 ', 4' -epoxycyclohexene carboxylate ("CELLOXIDE 2021P" manufactured by Daicel chemical Co., Ltd.): 80 percent of

1, 4-butanediol diglycidyl ether: 19 percent of

A photo-cationic polymerization initiator containing triarylsulfonium hexafluorophosphate as a main component (CPI-100P: a 50% propylene carbonate solution containing triarylsulfonium hexafluorophosphate as a main component, available from Sanapro corporation as "CPI-100P"): 1 percent of

4. Preparation of the adhesive

A reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer was charged with 81.8 parts by mass of ethyl acetate, 70.8 parts by mass of butyl acrylate, 20.0 parts by mass of methyl acrylate, 8.0 parts by mass of 2-phenoxyethyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate and 0.6 part by mass of acrylic acid, and the atmosphere in the apparatus was replaced with nitrogen gas to remove oxygen, while the internal temperature was increased to 55 ℃. Thereafter, a solution in which 0.14 parts by mass of azobisisobutyronitrile as a polymerization initiator was dissolved in 10 parts by mass of ethyl acetate was added in its entirety. The temperature was maintained 1 hour after the addition of the polymerization initiator, ethyl acetate was continuously added to the reaction vessel at an addition rate of 17.3 parts by mass/hour while maintaining the internal temperature at 54 to 56 ℃, and the addition of ethyl acetate was stopped when the concentration of the acrylic resin reached 35% by mass. Further, the mixture was kept at this temperature for 12 hours from the start of the addition of ethyl acetate. Finally, ethyl acetate was added thereto, and the concentration of the acrylic resin was adjusted to 20 mass%. This was used as an acrylic resin.

The weight average molecular weight and the number average molecular weight of the obtained acrylic resin were measured by the following methods. In the GPC apparatus, 4 TSKgel XL manufactured by Tosoh corporation and 5 Shodex GPC KF-802 manufactured by Showa Denko and sold by Showa Denko K.K., 5 columns in total were arranged in series, and the measurement was performed in accordance with the standard polystyrene conversion under the conditions of a sample concentration of 5mg/mL, a sample introduction amount of 100. mu.L, a temperature of 40 ℃ and a flow rate of 1 mL/min using tetrahydrofuran as an eluent. The weight-average molecular weight Mw of the obtained acrylic resin was 142 ten thousand, and Mw/Mn was 4.1.

To 100 parts by mass of the solid content of the acrylic resin (20% by mass ethyl acetate solution) prepared above, 0.5 parts by mass of glycidyloxypropyltrimethoxysilane (liquid) (KBM-403, product of shin-Etsu chemical Co., Ltd.) as a silane compound, 0.6 parts by mass of coronoxate r (isocyanurate of hexamethylene diisocyanate, liquid having an effective component of approximately 100% by mass, product of japan polyurethane corporation) as a crosslinking agent, and 3.0 parts by mass of N-octyl-4-methylpyridinium hexafluorophosphate were mixed. Next, ethyl acetate was added so that the solid content concentration became 13 mass% to obtain a binder.

Example 1

The films (2-D) and (2-E) as the protective layers were subjected to corona treatment in advance using a corona treatment machine (manufactured by Chunshi electric Co., Ltd.), and an adhesive was applied thereto and laminated to a polarizing film. After that, the adhesive is cured by irradiating ultraviolet rays with a metal halide lamp. A20 μm layer of the adhesive was formed on the film (2-E) side, and a concave side polarizing plate A having a thickness of 0.17mm (excluding the separator for forming the adhesive layer) was obtained.

In addition, a convex-side polarizing plate B having a thickness of 0.16mm (excluding the separator for forming an adhesive layer) was obtained in the same manner as above, except that the film (2-C) was used instead of the film (2-D).

The polarizing plate a was cut to a size of 1215mm in the horizontal direction (length in the horizontal direction) × 683mm in the vertical direction (length in the vertical direction), and at this time, the polarizing plate a was cut so that the absorption axis direction thereof was the horizontal direction. The polarizing plate B was cut to a size of 1215mm in the horizontal direction × 683mm in the vertical direction, and the polarizing plate B was cut so that the absorption axis direction thereof was vertical. The cut polarizing plate a was attached to the viewing side (concave side) of a glass panel having a thickness of 1215mm × 683mm in the vertical direction and 1.5mm in thickness, and the cut polarizing plate B was attached to the back side (convex side) of the panel. Thereafter, the glass panel was bent so that the average radius of curvature was 4000mm and fixed, and kept at 80 ℃ for 250 hours in a dry environment. After 250 hours, the appearance of the panel was visually observed, and as a result, peeling and lifting of the polarizing plate did not occur. The dimensional change rate measured by the above method was 0.8%. In this case, L1(H + H1)/2R is 0.25.

Example 2

The films (2-B) and (2-E) as the protective layers were subjected to corona treatment in advance using a corona treatment machine (manufactured by Chunshi electric Co., Ltd.), and an adhesive was applied thereto and laminated to a polarizing film. After that, the adhesive is cured by irradiating ultraviolet rays through a metal halide lamp. A20 μm layer of the adhesive was formed on the film (2-E) side, and a concave side polarizing plate C having a thickness of 0.19mm (excluding the separator for forming the adhesive layer) was obtained.

The convex-side polarizing plate D having a thickness of 0.18mm was obtained in the same manner as above except that the film (2-a) was used instead of the film (2-B).

The polarizing plate C was cut to a size of 1215mm in the lateral direction × 683mm in the longitudinal direction, and at this time, the polarizing plate C was cut so that the absorption axis direction thereof was the lateral direction. The polarizing plate D was cut to a size of 1215mm in the horizontal direction × 683mm in the vertical direction, and was cut so that the absorption axis direction of the polarizing plate D was vertical. The cut polarizing plate C was bonded to the viewing side (concave side) of a glass panel having a thickness of 1215mm × 683mm in the vertical direction and 1.5mm in thickness, and the cut polarizing plate D was bonded to the back side (convex side) of the panel. Thereafter, the panel was bent so that the average radius of curvature was 4000mm and fixed, and was maintained in a dry environment at 80 ℃ for 250 hours. After 250 hours, the appearance of the panel was visually observed, and as a result, peeling and lifting of the polarizing plate did not occur. The dimensional change rate measured by the above method was 1.4%. In this case, L1(H + H1)/2R is 0.26.

Example 3

The peeling and floating evaluation of the polarizing plates in the curved panel was performed in the same manner as in example 2 except that the polarizing plates C and D were cut into a size of 1440mm × 810mm in width, and the polarizing plates C and D were bonded to a glass panel having a thickness of 1.5mm and having a size of 1440mm × 810mm in width, and the panel was bent so that the average radius of curvature was 6600mm and fixed. As a result, the polarizing plate was not largely peeled off or lifted. The dimensional change rate measured by the above method was 1.4%. In this case, L1(H + H1)/2R is 0.18.

Comparative example 1

The peeling and lifting evaluation of the polarizing plate in the curved panel was performed in the same manner as in example 2, except that the average curvature radius of the panel was 2500 mm. As a result, the short side of the concave-side polarizing plate C was lifted from the glass by 50mm from the edge end. The dimensional change rate measured by the above method was 1.4%. In this case, L1(H + H1)/2R is 0.41.

Example 4

The same procedure as in example 2 was repeated except that the polarizing plates C and D were cut into a size of 1440mm in width × 810mm in length, and the polarizing plates C and D were bonded to a glass panel having a thickness of 1.5mm in width × 810mm in length, and peeling and lifting of the polarizing plate in the curved panel were evaluated, whereby L1(H + H1)/2R was 0.30, and occurrence of large peeling and lifting of the polarizing plate was suppressed.

Example 5

The same procedure as in example 2 was repeated except that the polarizing plates C and D were cut to a size of 1660mm in width × 934mm in length, and were bonded to a glass panel of 1660mm in width × 934mm in length and 1.5mm in thickness, and when the peeling and lifting of the polarizing plate in the curved panel were evaluated, L1(H + H1)/2R was 0.35, and the occurrence of large peeling and lifting of the polarizing plate was suppressed.

Example 6

The same procedure as in example 2 was repeated except that the dimensions of the polarizing plates C and D were cut to 900mm in width × 506mm in length, the polarizing plates C and D were bonded to a glass panel 900mm in width × 506mm in length and 1.5mm in thickness, and the average radius of curvature of the panel was 2500mm, and when the peeling and lifting of the polarizing plate in the curved panel were evaluated, L1(H + H1)/2R became 0.30, and the occurrence of large peeling and lifting of the polarizing plate was suppressed.

Example 7

The same procedure as in example 2 was repeated except that the polarizing plates C and D were cut to a size of 508mm × 286mm in width, the polarizing plates C and D were bonded to a glass panel having a thickness of 1.5mm and a thickness of 508mm × 286mm in width, and the average radius of curvature of the panel was 2500mm, and when the peeling and lifting of the polarizing plate in the curved panel were evaluated, L1(H + H1)/2R became 0.17, and the occurrence of large peeling and lifting of the polarizing plate was suppressed.

Comparative example 2

In the same manner as in example 4 except that the average radius of curvature of the panel was 2500mm, when the peeling and lifting of the polarizing plate were evaluated in the curved panel, the peeling and lifting of the polarizing plate occurred when L1(H + H1)/2R was 0.49.

Comparative example 3

In the same manner as in example 5 except that the average radius of curvature of the panel was 2500mm, when the peeling and lifting of the polarizing plate were evaluated in the curved panel, the peeling and lifting of the polarizing plate occurred when L1(H + H1)/2R was 0.56.

Comparative example 4

In the same manner as in example 6 except that the average radius of curvature of the panel was set to 1000mm, when the peeling and lifting of the polarizing plate were evaluated in the curved panel, the peeling and lifting of the polarizing plate occurred when L1(H + H1)/2R was 0.76.

Comparative example 5

In the same manner as in example 7 except that the average radius of curvature of the panel was set to 1000mm, when the peeling and lifting of the polarizing plate were evaluated in the curved panel, the peeling and lifting of the polarizing plate occurred when L1(H + H1)/2R was 0.43.

Example 8

The peeling and floating evaluation of the polarizing plate in the curved panel was performed in the same manner as in example 1 except that the polarizing plates a and B were cut into dimensions of 1050mm in width × 600mm in length, and the polarizing plates a and B were bonded to a glass panel of 1050mm in width × 600mm in length and 1.5mm in thickness, and the panel was bent so that the average curvature radius was 2500mm and fixed. As a result, the polarizing plate was not largely peeled off and lifted. The dimensional change rate measured by the above method was 0.8%. In this case, L1(H + H1)/2R is 0.35.

5. Evaluation of adhesion to glass

(1) Measurement of adhesion to glass

(a) Measurement of "adhesion to glass (Flat surface, 23 ℃ C.)" and "adhesion to glass (curved surface, 23 ℃ C.)"

A set of test pieces for measuring glass adhesion force in a flat state and a curved state prepared in examples 1 and 2 was set at 50 ℃ and 5kg/cm²(490.3kPa, gauge pressure) for 20 minutes, followed by autoclaving at 23 ℃ C,The glass panel and the polarizing plate were respectively clamped by an Autograph (AGS-50NX) manufactured by shimadzu corporation after being left standing for 24 hours in an atmosphere of 50% RH, and the polarizing plate was peeled in a direction of 180 ° at a speed of 300 mm/min. The peel strength thus measured was defined as "adhesive force to glass (flat surface, 23 ℃ C.)" and "adhesive force to glass (curved surface, 23 ℃ C.)". The results are shown in Table 1.

(b) Measurement of "adhesion to glass (flat surface, 80 ℃ C.)" and "adhesion to glass (curved surface, 80 ℃ C.)"

The other set of test pieces for measuring the glass adhesion force in the flat state and the curved state prepared in example 1 and example 2 was subjected to 50 ℃ and 5kg/cm²(490.3kPa, gauge pressure) was subjected to autoclave treatment for 20 minutes, and then left to stand in an atmosphere of 23 ℃ and 50% RH for 24 hours, and then left to stand in a dry atmosphere at 80 ℃ for 250 hours, and the glass panel and the polarizing plate were clamped by using Autograph (AGS-50NX) manufactured by Shimadzu corporation, respectively, and the polarizing plate was peeled in the direction of 180 ℃ at a speed of 300 mm/minute. The peel strength thus measured was defined as "adhesive force to glass (flat surface, 80 ℃ C.)" and "adhesive force to glass (curved surface, 80 ℃ C.)". The results are shown in Table 1.

TABLE 1

Claims

1. A polarizing plate used for a curved image display panel having an average curvature radius R and a thickness H, the polarizing plate having a horizontal direction length L1 in a planar state,

when the film is bonded to a curved image display panel, the thickness H1 of the polarizing plate on the concave side satisfies the following formula (1):

L1(H+H1)/2R≤0.4 (1)，

the units of the R, H, L1 and the H1 are both mm.

2. The polarizing plate according to claim 1, wherein the adhesive force to glass measured in a planar state at 23 ℃ and 50% RH is 2.0N/25mm or more.

3. The polarizing plate according to claim 1 or 2, wherein a horizontal direction length L1 of the polarizing plate in a planar state is 500mm or more.

4. The polarizing plate according to claim 1 or 2, wherein the curved image display panel has a thickness H of 0.4mm or more.

5. The polarizing plate according to claim 1 or 2, which has a dimensional change rate of 3% or less after 250 hours in a drying environment at 80 ℃.

6. The polarizing plate according to claim 1 or 2, wherein the polarizing film is a stretched and/or dyed polyvinyl alcohol film.

7. The polarizing plate of claim 1 or 2, the curved image display panel having an average radius of curvature R of 900 to 7000 mm.

8. A curved image display panel comprising a concave-side polarizing plate and a convex-side polarizing plate, wherein the concave-side polarizing plate is the polarizing plate according to any one of claims 1 to 7.

9. A curved image display panel comprising a concave-side polarizing plate and a convex-side polarizing plate, wherein the concave-side polarizing plate and the convex-side polarizing plate are the polarizing plates according to any one of claims 1 to 7.