CN110780373A

CN110780373A - Circular polarizing plate and display device

Info

Publication number: CN110780373A
Application number: CN201910688431.4A
Authority: CN
Inventors: 小川光明
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-07-31
Filing date: 2019-07-26
Publication date: 2020-02-11

Abstract

The invention provides a circular polarizing plate and a display device. When the circularly polarizing plate subjected to the durability test in a high-temperature and high-humidity environment is left at room temperature, the in-plane uniformity of the reflection color tone deteriorates with time. Specifically, there are the following problems: when the circularly polarizing plate is rectangular, the reflection color tone in the vicinity of 4 end edges of the circularly polarizing plate changes to blue or red, respectively. A circularly polarizing plate comprising a polarizing plate and a retardation film laminated thereon, the polarizing plate comprising a polarizing plate and a protective filmThe size shrinkage rate of the circular polarizer is 4.1 × 10 ^‑4mm/hour or less.

Description

Circular polarizing plate and display device

Technical Field

The invention relates to a circularly polarizing plate and a display device.

Background

In recent years, image display devices typified by organic electroluminescence (hereinafter also referred to as organic EL) display devices have rapidly spread. A circularly polarizing plate including a polarizer and a retardation film (λ/4 plate) is mounted on an organic EL display device. By disposing the circularly polarizing plate, reflection of external light can be prevented and visibility of a screen can be improved.

With the increasing demand for thinner image display devices due to the development of organic EL display devices, the circularly polarizing plate is also required to be thinner. A retardation film formed by changing a conventional retardation film formed of a resin film to a retardation film formed of a liquid crystal compound which can be made thinner has been studied (for example, see patent document 1). A retardation film using a polymerizable liquid crystal compound was produced as follows: the polymerizable liquid crystal compound is applied to a substrate to be aligned, and the aligned state is fixed by irradiating light as necessary.

When a circularly polarizing plate subjected to a durability test in a high-temperature and high-humidity environment is left at room temperature, the in-plane uniformity of the reflection color tone deteriorates with time. Specifically, there are the following problems: when the circularly polarizing plate is rectangular, the reflection color tone in the vicinity of 4 edge sides of the circularly polarizing plate changes to blue or red, respectively.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-54093

Disclosure of Invention

Problems to be solved by the invention

The present invention aims to provide a circularly polarizing plate which shows little change in reflection color tone even when placed in a high-temperature and high-humidity environment and then in a room-temperature environment.

Means for solving the problems

[1] A circularly polarizing plate comprising a polarizing plate and a retardation film laminated on each other,

the polarizing plate is provided with a polarizer and a protective film,

the size shrinkage speed of the circular polarizer is 4.1 multiplied by 10 ^-4mm/hr (hr) or less.

[2] The circularly polarizing plate according to [1], wherein the polarizing plate has a protective film disposed between the polarizer and the retardation film.

[3] The circularly polarizing plate according to [1] or [2], wherein the shape of the main surface is substantially rectangular,

the slow axis of the retardation film is parallel to the long side direction of the circularly polarizing plate,

the magnitude of the angle formed by the slow axis of the retardation film and the absorption axis of the polarizing plate was substantially 45 °.

[4] The circularly polarizing plate according to any one of [1] to [3], wherein the retardation film comprises a layer obtained by curing a polymerizable liquid crystal compound,

an adhesive layer is disposed on the side of the retardation film opposite to the polarizing plate side.

[5] The circularly polarizing plate according to any one of [1] to [4], further comprising a display panel.

[6] The circularly polarizing plate according to [5], which is bendable.

[7] The circularly polarizing plate according to [5] or [6], further comprising a touch sensor and a window film (window film), wherein a display panel, the touch sensor, a polarizer, and the window film are sequentially stacked.

[8] The circularly polarizing plate according to [5] or [6], further comprising a touch sensor in which a display panel, a polarizing plate, and the touch sensor are laminated in this order.

[9] The circularly polarizing plate according to [8], further comprising a window film,

which is sequentially laminated with a display panel, a polarizing plate, a touch sensor, and a window film.

[10] A display device, wherein the circularly polarizing plate of any one of [1] to [9] is laminated on a display element via an adhesive layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a circularly polarizing plate can be provided which shows little change in reflection color tone even when placed in a high-temperature and high-humidity environment and then placed in a room-temperature environment.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a layer structure of a circularly polarizing plate.

Fig. 2 is a plan view of the evaluation sample.

Description of the reference numerals

1 polarizing plate

2 phase difference film

5 point

10 polarizing plate

11. 12 protective film

13. 14 adhesive layer

15 adhesive layer

20. 21 layer obtained by curing polymerizable liquid crystal compound

100. 101, 102 circular polarizing plate

Detailed Description

< circularly polarizing plate >

The circularly polarizing plate of the present invention includes a polarizing plate and a retardation film. The polarizing plate and the retardation film may be laminated via an adhesive layer, for example. Examples of the adhesive layer include an adhesive layer and an adhesive layer described later. Examples of the adhesive layer include an aqueous adhesive layer and an active energy ray-curable adhesive layer. In the present invention, the polarizing plate refers to a laminate including a polarizer and a protective film attached to one or both surfaces of the polarizer.

An example of the layer structure of the circularly polarizing plate of the present invention will be described below with reference to fig. 1. In fig. 1, the adhesive layers for bonding the polarizing plate 10 and the

protective films

11 and 12 to each other are not shown.

The circularly polarizing plate 100 shown in fig. 1 (a) has a layer structure in which a polarizing plate 1 having a1 st protective film 11 laminated on one surface of a polarizing plate 10 and a2 nd protective film 12 laminated on the other surface of the polarizing plate 10 and a phase difference film 2 having a layer 20 formed by curing a polymerizable liquid crystal compound are laminated via an adhesive layer 13. That is, the polarizing plate has a protective film 12 disposed between the polarizer 10 and the retardation film 2. The circularly polarizing plate 100 further includes an adhesive layer 14 on the side of the retardation film 2 opposite to the polarizing plate 1. The adhesive layer 14 may be an adhesive layer for bonding to an organic EL display element or the like.

The circularly polarizing plate 101 shown in fig. 1 (b) has a layer structure in which a polarizing plate 1 having a1 st protective film 11 laminated on one surface of a polarizing plate 10 and a2 nd protective film 12 laminated on the other surface of the polarizing plate 10 and a phase difference film 2 are laminated with an adhesive layer 13 interposed therebetween. In the circularly polarizing plate 101, the retardation film 2 has a layer structure in which a layer 20 formed by curing a polymerizable liquid crystal compound and a layer 21 formed by curing a polymerizable liquid crystal compound are laminated with an adhesive layer 15 interposed therebetween. The circularly polarizing plate 101 further includes an adhesive layer 14 on the side of the retardation film 2 opposite to the polarizing plate 1. The adhesive layer 14 may be an adhesive layer for bonding to an organic EL display element or the like.

As shown in fig. 1, the retardation film may have 1 retardation layer or 2 retardation layers. The retardation film may have an alignment film for aligning the polymerizable liquid crystal compound in the production stage thereof.

The circularly polarizing plate may have layers other than those shown in fig. 1. Examples of the circularly polarizing plate that may further include a layer include a front panel, a light-shielding pattern, and a display panel. The front panel may be disposed on a side of the polarizing plate opposite to the side on which the retardation film is laminated.

Examples of the front panel include glass, a touch sensor, and a window film.

Window films typically comprise a hard coat layer on at least one side of a transparent substrate. The touch sensor is a member in which an insulating layer, an electrode layer, and a base material are laminated. The electrode layer has a sensing pattern formed of a transparent electrode and a bridge electrode, and a sensing line. The transparent electrodes, the bridge electrodes and the sensing lines can be made of known materials and methods. The insulating layer and the substrate of the touch sensor can be manufactured by a known method.

The display panel may be a bendable display panel.

Examples of the circularly polarizing plate include:

a circularly polarizing plate further including a display panel (e.g., a bendable display panel);

a circular polarizing plate further comprising a display panel (for example, a bendable display panel), a touch sensor, and a window film, wherein the display panel, the touch sensor, a polarizing plate, and the window film are laminated in this order;

a circular polarizing plate further including a display panel (e.g., a bendable display panel) and a touch sensor, the display panel, a polarizing plate, and the touch sensor being stacked in this order;

and a circular polarizing plate which comprises a display panel (e.g., a bendable display panel) and a window film, and in which the display panel, a polarizing plate, a touch sensor, and the window film are laminated in this order.

The light shielding pattern may be formed on a face of the front panel on the polarizing plate side. The light shielding pattern may be formed at a bezel (non-display area) of the image display device so that the wiring of the image display device cannot be seen by a user.

The shape of the main surface of the circularly polarizing plate may be substantially rectangular. The main surface is a surface having the largest area corresponding to the display surface. Substantially rectangular means: at least 1 of the 4 corners (corners) may be cut to form an obtuse angle or rounded, or may have a concave portion (notch) in which a part of the main surface is recessed in the in-plane direction, or a hole portion hollowed out in a shape such as a circle, an ellipse, a polygon, or a combination thereof.

The size of the circularly polarizing plate is not particularly limited. When the circularly polarizing plate is substantially rectangular, the length of the long side is preferably 6cm or more and 35cm or less, more preferably 10cm or more and 30cm or less, and the length of the short side is preferably 5cm or more and 30cm or less, more preferably 6cm or more and 25cm or less.

In the circularly polarizing plate of the present invention, the angle formed by the slow axis of the retardation film and the absorption axis of the polarizer is preferably substantially 45 °. Substantially 45 means 45 ± 10 °.

When the circularly polarizing plate has a substantially rectangular shape, the slow axis of the retardation film may be parallel to the longitudinal direction or the short direction, and the angle formed by the slow axis of the retardation film and the absorption axis of the polarizer may be substantially 45 °. In the case of such a shaft configuration, the effect of the present invention is remarkable.

The size shrinkage rate of the circular polarizer is 4.1 × 10 ^-4mm/hour (hr.) or less. The size shrinkage speed of the circular polarizer is preferably 3.8 × 10 ^-4mm/hr. or less, more preferably 2.5X 10 ^-4mm/hr. Presumably: by limiting the dimensional change behavior to a range slower than that of the conventional products, stress relaxation applied to the retardation film occurs simultaneously with shrinkage of the circularly polarizing plate, and as a result, variation in retardation can be suppressed.

According to the study of the present inventors, it has been clarified that: the reason for the change in the reflection color tone of the circularly polarizing plate is the change in the phase difference value of the phase difference film. Further, it is clear that: the reason why the change in the retardation value of the retardation film is caused by the change in the size of the circular polarizer due to the entrance and exit of moisture. By setting the size contraction rate of the circular polarizing plate in such a range, it is possible to reduce the change in size of the circular polarizing plate due to the entrance and exit of moisture when the circular polarizing plate is transferred from a high-temperature and high-humidity environment to a room-temperature environment (specifically, contraction due to the release of moisture). As a result, stress generated at the end of the circularly polarizing plate can be reduced, and variation in the phase difference value can be reduced.

The size shrinkage speed of the circular polarizer may be 0.5 × 10 ^-4mm/hr. or more, and may be 1.0X 10 ^-4mm/hr. By setting the size shrinkage rate of the circular polarizer to such a range, appearance defects due to misalignment of the adhesive on the cell (cell) side can also be suppressed.

The size shrinkage speed of the circular polarizer can be measured in the following manner. The circularly polarizing plate was cut into a size of 50mm in the slow axis direction and 50mm in the fast axis direction of the retardation film. The cut circularly polarizing plate was bonded to alkali-free glass (product name: Eagle XG, manufactured by Corning corporation) having a thickness of 0.4mm, and placed in an oven under a high-temperature and high-humidity environment (temperature 60 ℃ C., relative humidity 95%) for 168 hours. The dimensions of the circular polarizer were measured immediately after the sheet was taken out from the oven to room temperature (temperature 23 ℃ C., relative humidity 55%), and then the dimensions of the circular polarizer were measured when the sheet was stored at room temperature for 24 hours. The size shrinkage speed of the circular polarizer was calculated from the slope of the size change. In each of the above measurements, the dimension of the retardation film in the slow axis direction was measured.

The size shrinkage speed of the circular polarization plate can be controlled in the following manner. The control of the size shrinkage speed of the circular polarizer can be controlled by controlling the evaporation speed of moisture from the polarizer having the largest moisture amount. For example, the dimensional shrinkage rate can be controlled by adjusting the moisture permeability of the protective film of the polarizing plate or the thickness of the polarizing plate.

As described later, as the moisture permeability of the protective film of the polarizer is lower, shrinkage of the polarizing plate is suppressed, and as a result, the size shrinkage rate of the circular polarizing plate is likely to be reduced. As the thickness of the polarizing plate is smaller, the entrance and exit of moisture from the polarizing plate is smaller, and thus the size shrinkage rate of the circular polarizing plate is likely to be smaller.

The dimensional shrinkage of the circular polarizer in the fast axis direction of the retardation film is preferably 0.25% or less, more preferably 0.20% or less, and still more preferably 0.15% or less. By making the size change rate satisfy such a range, the change in reflected color tone is further reduced. The lower limit is not particularly limited, and the dimensional shrinkage of the circular polarizer may be 0.0% or more in the fast axis direction of the retardation film.

The dimensional shrinkage of the circular polarizer in the slow axis direction of the retardation film is preferably 0.15% or less, more preferably 0.10% or less, and still more preferably 0.08% or less. By making the size change rate satisfy such a range, the change in reflected color tone is further reduced. The lower limit is not particularly limited, and the dimensional shrinkage of the circular polarizer may be 0.0% or more in the slow axis direction of the retardation film.

The dimensional shrinkage of the circular polarizer can be measured in the following manner. The circularly polarizing plate was cut into a size of 50mm in the slow axis direction and 50mm in the fast axis direction of the retardation film. The cut circularly polarizing plate was bonded to alkali-free glass (product name: Eagle XG, manufactured by Corning corporation) having a thickness of 0.4mm, and placed in an oven under a high-temperature and high-humidity environment (temperature 60 ℃ C., relative humidity 95%) for 168 hours. The dimensions of the circularly polarizing plate (initial dimension) before being charged into the oven and the circularly polarizing plate immediately after being taken out of the oven were measured using a two-dimensional dimension measuring apparatus (apparatus name: VMR-12072 manufactured by Nikon corporation), and the dimensional shrinkage of the circularly polarizing plate was calculated from the following equation.

Size shrinkage (%) of circular polarizer (initial size-size after heating)/initial size × 100

The size shrinkage of the circular polarizer may be controlled in the following manner. The control of the dimensional shrinkage of the polarizer is performed by: first, a shrinkage force of the polarizing plate is suppressed; second, as the protective film of the polarizing plate, a protective film having a small moisture permeability and being less likely to undergo shrinkage or expansion due to moisture is selected.

< polarizing plate >

In the present invention, the polarizing plate refers to a laminate including a polarizer and a protective film attached to one or both surfaces of the polarizer. The protective film provided in the polarizing plate may have a surface treatment layer such as a hard coat layer, an antireflection layer, or an antistatic layer, which will be described later. The polarizing plate and the protective film may be laminated via an adhesive layer or an adhesive layer, for example. Hereinafter, the members provided in the polarizing plate will be described.

(1) Polarizing plate

The shrinkage force of the polarizing plate in the present invention is preferably 3.0N or less in an environment of 80 ℃.

The contraction force referred to herein is a contraction force in the absorption axis direction of the polarizing plate, and means a contraction force per 2mm width. The shrinkage force of the polarizing plate is more preferably 2.10N or less, and still more preferably 1.90N or less. By setting the shrinkage force of the polarizing plate in such a range, it is possible to reduce the dimensional change of the circular polarizing plate due to the entrance and exit of moisture when the polarizing plate is transferred from a high-temperature and high-humidity environment to a room-temperature environment (specifically, shrinkage due to the release of moisture). As a result, it is considered that the stress generated at the end portion of the circularly polarizing plate can be reduced and the variation in the phase difference value can be reduced. The shrinkage force of the polarizing plate may be 0.0N or more, may be 0.1N or more, and may be 1.0N or more. When the shrinkage force of the polarizing plate is in such a range, appropriate polarization performance can be easily provided.

The shrinkage force of the polarizing plate is controlled by, for example, adjusting the thickness of the polarizing plate or adjusting the crosslinking conditions and stretching conditions in the stretching step.

The shrinkage force of the polarizing plate was measured by using a thermomechanical analyzer (apparatus name: TMA/SS7100 manufactured by HITACHI corporation). In this measurement, a polarizing plate cut to have a width of 2mm and a length of 50mm so that the absorption axis direction becomes a long side can be used as a test piece. The measurement was performed in a mode of a predetermined size, and the inter-jig distance was set to 10 mm. After the test piece was left to stand in a room at a temperature of 23 ℃ and a relative humidity of 55% for 24 hours or more, the temperature in the sample room was set as follows: the temperature was raised from 23 ℃ to 80 ℃ in 1 minute, and the temperature in the sample chamber was maintained at 80 ℃ after the temperature rise. After the temperature was raised, the test piece was left for another 4 hours, and then the shrinkage force in the absorption axis direction of the test piece was measured at 80 ℃.

The polarizer included in the polarizing plate may be an absorption polarizer having the following properties: linearly polarized light having a vibration plane parallel to an absorption axis thereof is absorbed, and linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to a transmission axis) is transmitted. As the polarizing plate, a polarizing plate in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film can be suitably used. The polarizing plate can be manufactured by, for example, a method including the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing the polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; a step of treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with a crosslinking liquid such as an aqueous boric acid solution; and a step of washing the treated product with water after the treatment with the crosslinking solution.

As the polyvinyl alcohol resin, a polyvinyl alcohol resin obtained by saponifying a polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

In the present specification, "(meth) acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth) acryloyl group", "meth) acrylate", 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, or the like modified with aldehydes may be used. The polyvinyl alcohol resin has an average polymerization degree of usually 1000 to 10000, preferably 1500 to 5000. The average polymerization degree of the polyvinyl alcohol resin can be determined in accordance with JIS K6726.

A film made of such a polyvinyl alcohol resin is used as a raw material film of a polarizing plate. The method for forming the film from the polyvinyl alcohol resin is not particularly limited, and a known method can be used. The thickness of the polyvinyl alcohol-based material film is not particularly limited, and a material film of 5 to 35 μm is preferably used so that the thickness of the polarizing plate is 15 μm or less. More preferably 20 μm or less.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing of the dichroic dye. In the case where the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the crosslinking treatment. In addition, uniaxial stretching may be performed in a plurality of stages thereof.

In the case of uniaxial stretching, the uniaxial stretching may be performed between rolls having different peripheral speeds, or the uniaxial stretching may be performed using a heat 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 or water. The draw ratio is usually 3 to 6 times.

As a method for dyeing the polyvinyl alcohol resin film with the dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye can be employed. As the dichroic dye, iodine or a dichroic organic dye can be used. The polyvinyl alcohol resin film is preferably subjected to an immersion treatment in water before the dyeing treatment.

As the crosslinking treatment after dyeing with the dichroic dye, a method of immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid is generally employed. In the case of using iodine as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

The thickness of the polarizing plate is usually 20 μm or less, preferably 15 μm or less, more preferably 13 μm or less, still more preferably 10 μm or less, and particularly preferably 8 μm or less.

The thickness of the polarizing plate is usually 2 μm or more, preferably 3 μm or more. According to the study of the present inventors, it has been clarified that: the reason for the change in the reflection color tone of the circularly polarizing plate is the change in the phase difference value of the phase difference film. Further, it is clear that: the change in the retardation value of the retardation film depends on the dimensional shrinkage rate of the circular polarizer due to the entrance and exit of moisture (specifically, shrinkage due to the release of moisture). The dimensional change is caused by the transition from a high temperature and high humidity environment to a room temperature environment. Therefore, from the viewpoint of reducing the influence of shrinkage of the polarizing plate, it is effective to prevent the color tone from changing by setting the thickness of the polarizing plate to 15 μm or less.

As the polarizing plate, for example, a polarizing plate in which a dichroic dye is aligned in a cured film obtained by polymerizing a liquid crystal compound as described in japanese patent application laid-open No. 2016 and 170368 can be used. As the dichroic dye, a dichroic dye having absorption in a wavelength range of 380 to 800nm can be used, and an organic dye is preferably used. Examples of the dichroic dye include azo compounds.

The liquid crystal compound is a liquid crystal compound capable of being polymerized in an aligned state, and may have a polymerizable group in a molecule. Further, as described in the monograph of international publication No. 2011/024891, a polarizing plate may be formed of a dichroic dye having liquid crystallinity.

(2) Protective film

In the circularly polarizing plate of the present invention, the protective film disposed between the polarizer and the retardation film preferably has a coefficient of humidity expansion of 6.5 × 10 ^-5cm/cm/% RH or less, more preferably 5.0X 10 ^-5cm/cm/% RH or less, more preferably 5.0X 10 ^-6cm/cm/% RH or less. The lower limit is not particularly limited, and may be 1.0X 10 ^-6cm/cm/% RH or higher. By setting the coefficient of humidity expansion in such a range, the change in color tone can be further reduced. The humidity expansion coefficient of the protective film may be a value in a direction corresponding to the slow axis direction of the retardation film.

The coefficient of humidity expansion can be determined in the following manner. The protective film was cut into a size of 100mm in the direction corresponding to the slow axis direction of the retardation film provided in the circularly polarizing plate and 100mm in the direction orthogonal to the direction corresponding to the slow axis in the plane, and the length of the protective film at 23 ℃ and 50% RH and at 23 ℃ and 90% RH was measured to measure the coefficient of humidity expansion [ cm/cm/% RH ] according to the following equation.

Coefficient of humidity expansion (L90-L50)/(L50 × Δ H)

Here, L50 is the length (mm) of the protective film in the direction corresponding to the slow axis direction of the retardation film at a temperature of 23 ℃ and a relative humidity of 50% RH, L90 is the length (cm) of the protective film in the direction corresponding to the slow axis direction of the retardation film at a temperature of 23 ℃ and a relative humidity of 90% RH, and Δ H is 40(═ 90 to 50)% RH.

The circularly polarizing plate of the present invention preferably has a protective film on at least one surface of the polarizer, and preferably has a protective film on the surface of the polarizer opposite to the retardation film side. When the circularly polarizing plate is substantially rectangular and the protective film is a stretched film, the stretching direction of the protective film is preferably substantially parallel to the short side direction of the circularly polarizing plate. When the stretching direction and the short-side direction are in such a relationship, the color tone change of the circularly polarizing plate tends to be small regardless of the slow axis direction of the retardation film. It can be considered that: in the case where the stretching direction of the protective film is parallel to the short side, the shrinkage force of the protective film in the stretching direction due to the stretching relaxation of the polarizing plate and the protective film in a high temperature environment is smaller and the change in color tone is smaller than in the case where the stretching direction of the protective film is parallel to the long side.

The fact that the stretching direction of the protective film is substantially parallel to the short side direction of the circularly polarizing plate includes not only the case where both are strictly parallel but also the case where the angle formed by both is 0 ± 10 °. The angle formed by the stretching direction of the protective film and the short side direction of the circularly polarizing plate is preferably 0 ± 5 °.

The protective film to be laminated on the polarizing plate may be a protective film comprising a polyolefin-based resin such as a thermoplastic resin having light transmittance (preferably optically transparent), for example, a chain polyolefin-based resin (polypropylene-based resin, etc.) or a cyclic polyolefin-based resin (norbornene-based resin, etc.); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins such as methyl methacrylate resins; a polystyrene-based resin; a polyvinyl chloride resin; acrylonitrile-butadiene-styrene resins; acrylonitrile-styrene resins; polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; modified polyphenylene ether resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyarylate-based resin; a polyamide imide resin; a film of a polyimide resin or the like. In the present invention, the protective film is preferably a film containing a cellulose-based resin, a polyolefin-based resin, or a (meth) acrylic resin.

Examples of the chain polyolefin resin include: homopolymers of chain olefins such as polyethylene resins (polyethylene resins, which are homopolymers of ethylene, and copolymers mainly composed of ethylene), and polypropylene resins (polypropylene resins, which are homopolymers of propylene, and copolymers mainly composed of propylene); and a copolymer containing 2 or more kinds of chain olefins.

The cyclic polyolefin resin is a general term for resins polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include those described in Japanese patent application laid-open Nos. 1-240517, 3-14882, and 3-122137. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins; addition polymers of cyclic olefins; copolymers (typically random copolymers) of cyclic olefins and chain olefins such as ethylene and propylene, graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides of these. Among them, it is preferable to use: norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins.

The polyester resin is a resin having an ester bond other than the following cellulose ester resins, and generally includes a polycondensate of a polycarboxylic acid or a derivative thereof and a polyol. As the polycarboxylic acid or a derivative thereof, a dicarboxylic acid having a valence of 2 or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a diol having a valence of 2 can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol. A typical example of the polyester resin is polyethylene terephthalate, which is a condensation product of terephthalic acid and ethylene glycol.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example: poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymers; methyl methacrylate-acrylate- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymers (MS resins and the like); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylic acid norbornyl ester copolymer, etc.). Preferably, a poly (meth) acrylic acid C such as poly (methyl (meth) acrylate) is used _1-6The polymer containing an alkyl ester as a main component is preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, copolymers thereof and resins in which a part of the hydroxyl groups is modified with other substituents are exemplified. Among them, cellulose triacetate (triacetyl cellulose) is particularly preferable.

The polycarbonate-based resin is an engineering plastic containing a polymer in which a monomer unit is bonded through a carbonate group.

The thickness of the protective film is usually 1 to 100 μm, and is preferably 5 to 60 μm, more preferably 10 to 55 μm, and still more preferably 15 to 40 μm from the viewpoint of strength, workability, and the like.

The protective film to be attached to one side or both sides of the polarizing plate may contain the same kind of thermoplastic resin, or may contain different kinds of thermoplastic resins. The thicknesses may be the same or different. Further, the retardation film may have the same retardation characteristics or may have different retardation characteristics.

As described above, at least any one of the protective films may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an optical diffusion layer, an antireflection layer, a low refractive index layer, an antistatic layer, and an antifouling layer on its outer surface (surface on the side opposite to the polarizing plate). The thickness of the protective film includes the thickness of the surface treatment layer.

The protective film may be bonded to the polarizing plate via an adhesive layer or an adhesive layer, for example. As the adhesive for forming the adhesive layer, an aqueous adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive can be used, and an aqueous adhesive or an active energy ray-curable adhesive is preferable. As the pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer described later can be used.

Examples of the aqueous adhesive include an adhesive containing a polyvinyl alcohol resin aqueous solution, and an aqueous two-pack polyurethane emulsion adhesive. Among them, an aqueous adhesive containing an aqueous solution of a polyvinyl alcohol resin is suitably used. As the polyvinyl alcohol resin, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, a modified polyvinyl alcohol polymer obtained by modifying a hydroxyl group portion of the copolymer, or the like can be used. The aqueous adhesive may contain a crosslinking agent such as an aldehyde compound (e.g., glyoxal), an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, or a polyvalent metal salt.

When an aqueous adhesive is used, it is preferable to perform a drying step for removing water contained in the aqueous adhesive after the polarizing plate and the protective film are bonded. After the drying step, a curing step of curing at a temperature of, for example, 20 to 45 ℃ may be provided.

The active energy ray-curable adhesive is an adhesive containing a curable compound that is cured by irradiation with an active energy ray such as an ultraviolet ray, visible light, an electron beam, or an X-ray, and is preferably an ultraviolet ray-curable adhesive.

The curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having 1 or 2 or more epoxy groups in a molecule), an oxetane compound (a compound having 1 or 2 or more oxetane rings in a molecule), and a combination thereof. Examples of the radically polymerizable curable compound include a (meth) acrylic compound (a compound having 1 or 2 or more (meth) acryloyloxy groups in the molecule), another vinyl compound having a radically polymerizable double bond, and a combination thereof. The cationically polymerizable curable compound and the radically polymerizable curable compound may be used in combination. The active energy ray-curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

When the polarizing plate and the protective film are bonded, at least either one of the bonding surfaces may be subjected to a surface activation treatment in order to improve the adhesiveness. Examples of the surface activation treatment include: dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment and the like), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet ray treatment, electron ray treatment and the like); such as ultrasonic treatment using a solvent such as water or acetone, saponification treatment, and wet treatment such as anchor coat treatment. These surface activation treatments may be performed alone or in combination of 2 or more.

When protective films are bonded to both surfaces of a polarizing plate, adhesives used for bonding these protective films may be the same type of adhesive or different types of adhesives.

< retardation film >

The circularly polarizing plate of the present invention has a retardation film, and the retardation film includes a retardation layer. The retardation layer may be a stretched film, and the material of the stretched film is used from among the resins exemplified above as the resin forming the protective film. In this case, the retardation layer may be a stretched film containing a polyolefin-based resin or a polycarbonate-based resin. The phase difference layer preferably has: a layer comprising a composition containing a polymerizable liquid crystal compound. Specifically, the layer containing the composition containing the polymerizable liquid crystal compound refers to a layer obtained by curing the polymerizable liquid crystal compound. In the present specification, a layer to which a retardation of λ/2 is given, a layer to which a retardation of λ/4 is given (positive a layer), a positive C layer, and the like may be collectively referred to as a retardation layer. The retardation film may further include an alignment film described later.

The layer for imparting a retardation of lambda/2 is preferably a layer having an in-plane retardation value of 200 to 280nm at a wavelength of 550nm, more preferably a layer having an in-plane retardation value of 215 to 265 nm. The layer for imparting a retardation of lambda/4 is preferably a layer having an in-plane retardation value of 100 to 160nm at a wavelength of 550nm, and more preferably a layer having an in-plane retardation value of 110 to 150 nm. The positive C layer may be a layer exhibiting a correlation of nx ≈ ny < nz in refractive index. The phase difference value in the thickness direction of the positive C layer can be-50 nm to-150 nm at a wavelength of 550nm, and can also be-70 nm to-120 nm. The retardation layer may exhibit positive wavelength dispersibility or may exhibit reverse wavelength dispersibility.

The layer obtained by curing the polymerizable liquid crystal compound is formed on, for example, an alignment film provided on a substrate. The substrate may be a long substrate having a function of supporting the alignment film. The substrate functions as a releasable support and can support a phase difference layer for transfer. Further, it is preferable that the adhesive has such a degree of adhesiveness that the surface thereof can be peeled. The substrate may be a resin film exemplified as a material of the protective film.

The thickness of the substrate is not particularly limited, and is preferably in the range of, for example, 20 μm to 200 μm. If the thickness of the base material is 20 μm or more, strength is imparted. On the other hand, if the thickness is 200 μm or less, increase of machining chips and abrasion of the cutting edge can be suppressed when the base material is cut into individual pieces.

The substrate may be subjected to various anti-blocking treatments. Examples of the anti-blocking treatment include an easy adhesion treatment, a treatment of mixing a filler or the like, and an embossing treatment (knurling treatment). By applying such an anti-blocking treatment to the base material, adhesion between the base materials when the base materials are wound, so-called blocking, can be effectively prevented, and an optical film can be produced with high productivity.

The layer obtained by curing the polymerizable liquid crystal compound is formed on the substrate with the alignment film interposed therebetween. That is, a layer obtained by laminating a substrate and an alignment film in this order and curing a polymerizable liquid crystal compound is laminated on the alignment film.

The alignment film is not limited to a vertical alignment film, and may be an alignment film in which the molecular axis of the polymerizable liquid crystal compound is aligned horizontally or an alignment film in which the molecular axis of the polymerizable liquid crystal compound is aligned obliquely. The alignment film is preferably one having solvent resistance that does not dissolve due to application of a composition containing a polymerizable liquid crystal compound described later and having heat resistance for use in heat treatment for removing the solvent or aligning the liquid crystal compound. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film, and a groove alignment film in which a concave-convex pattern or a plurality of grooves are formed on the surface thereof and the grooves are aligned. The thickness of the alignment film is usually in the range of 10nm to 10000nm, preferably 10nm to 1000nm, more preferably 500nm or less, and still more preferably 10nm to 200 nm.

The resin used for the alignment film is not particularly limited as long as it is a resin used as a material of a known alignment film, and a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth) acrylate monomer in the presence of a polymerization initiator, or the like can be used. Specifically, examples of the (meth) acrylate monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and urethane acrylate. The resin may be a mixture of 1 or more of them.

The type of the polymerizable liquid crystal compound used in the present embodiment is not particularly limited, and the polymerizable liquid crystal compound can be classified into a rod-like type (rod-like liquid crystal compound) and a disk-like type (disk-like liquid crystal compound, discotic liquid crystal compound) in terms of its shape. Further, there are low molecular type and high molecular type, respectively. The term "polymer" generally means a substance having a polymerization degree of 100 or more (polymer physical/phase transition kinetics, Tujing university, p.2, Shibo Shu, 1992).

In the present embodiment, any polymerizable liquid crystal compound may be used. Further, 2 or more kinds of rod-like liquid crystal compounds, 2 or more kinds of discotic liquid crystal compounds, or a mixture of rod-like liquid crystal compounds and discotic liquid crystal compounds may be used.

As the rod-like liquid crystal compound, for example, the rod-like liquid crystal compounds described in claim 1 of Japanese patent application laid-open No. 11-513019 or paragraphs [0026] to [0098] of Japanese patent application laid-open No. 2005-289980 can be suitably used. As the discotic liquid crystal compound, for example, discotic liquid crystal compounds described in paragraphs [0020] to [0067] of Japanese patent application laid-open No. 2007-108732 or paragraphs [0013] to [0108] of Japanese patent application laid-open No. 2010-244038 can be suitably used.

The polymerizable liquid crystal compound may be used in combination of 2 or more. In this case, at least 1 species has 2 or more polymerizable groups in the molecule. That is, the layer formed by curing the polymerizable liquid crystal compound is preferably a layer in which a liquid crystal compound having a polymerizable group is fixed by polymerization. In this case, the liquid crystal does not need to be further exhibited after the layer is formed.

The polymerizable liquid crystal compound has a polymerizable group capable of undergoing a polymerization reaction. The polymerizable group is preferably a functional group capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a cyclopolymerizable group. More specifically, examples of the polymerizable group include a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among them, (meth) acryloyl groups are preferable. The term "meth (acryloyl group" is a concept including both methacryloyl groups and acryloyl groups.

As described later, a layer obtained by curing a polymerizable liquid crystal compound can be formed by applying a composition containing a polymerizable liquid crystal compound to, for example, an alignment film and irradiating an active energy ray, and a component other than the polymerizable liquid crystal compound can be contained in the composition, for example, a polymerization initiator is preferably contained in the composition, and a thermal polymerization initiator or a photopolymerization initiator is selected depending on the form of polymerization reaction, for example, α -carbonyl compound, acyloin ether, α -hydrocarbon-substituted aromatic acyloin compound, polyquinone compound, a combination of triarylimidazole dimer and p-aminophenyl ketone, and the like are given as a photopolymerization initiator, and the amount of the polymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content in the coating liquid.

The composition may contain a polymerizable monomer in terms of uniformity of the coating film and film strength. Examples of the polymerizable monomer include a radically polymerizable or cationically polymerizable compound. Among them, polyfunctional radical polymerizable monomers are preferable.

As the polymerizable monomer, a polymerizable monomer copolymerizable with the polymerizable liquid crystal compound is preferable. The amount of the polymerizable monomer used is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the polymerizable liquid crystal compound.

The composition may contain a surfactant in terms of uniformity of the coating film and film strength. The surfactant may be a conventionally known compound. Among them, fluorine compounds are particularly preferable.

The composition may contain a solvent, and an organic solvent is preferably used.

Examples of the organic solvent include amides (e.g., N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), halogenated alkanes (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1, 2-dimethoxyethane). Among them, halogenated alkanes and ketones are preferable. In addition, 2 or more organic solvents may be used in combination.

The composition may contain a vertical alignment promoter such as a polarizing plate interface side vertical alignment agent or an air interface side vertical alignment agent; and various alignment agents such as a horizontal alignment promoter such as a polarizing plate interface side horizontal alignment agent and an air interface side horizontal alignment agent. The composition may further contain an adhesion improver, a plasticizer, a polymer, and the like in addition to the above components.

The active energy ray includes ultraviolet rays, visible light, electron rays, and X-rays, and preferably ultraviolet rays. Examples of the light source of the active energy ray include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excimer laser, an LED light source emitting light in a wavelength range of 380 to 440nm, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp.

The intensity of ultraviolet light irradiation is usually 100mW/cm ²～3,000mW/cm ². The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activation of the cationic polymerization initiator or the radical polymerization initiator. The time for ultraviolet irradiation is usually 0.1 second to 10 minutes, preferably 0.1 second to 5 minutes, more preferably 0.1 second to 3 minutes, and still more preferably 0.1 second to 1 minute.

In the present embodiment, the thickness of the retardation layer is preferably 0.5 μm or more. The thickness of the retardation layer is preferably 10 μm or less, and more preferably 5 μm or less. The upper limit and the lower limit described above may be arbitrarily combined. When the thickness of the retardation layer is not less than the lower limit, sufficient durability is obtained. If the thickness of the retardation layer is not more than the upper limit, it can contribute to thinning of the circularly polarizing plate. The thickness of the retardation layer can be adjusted so that a desired in-plane retardation value and a retardation value in the thickness direction of the layer to which a retardation of λ/4 is given, the layer to which a retardation of λ/2 is given, or the positive C layer can be obtained.

The retardation film may be one comprising 1 layer of a cured polymerizable liquid crystal compound, or may be one comprising 2 or more layers of a cured polymerizable liquid crystal compound. When the retardation film includes 2 layers of cured polymerizable liquid crystal compound, the 2 layers are preferably a layer giving a retardation of λ/4 and a positive C layer, or a layer giving a retardation of λ/4 and a layer giving a retardation of λ/2. When the retardation film includes 2 cured layers of the polymerizable liquid crystal compound, the retardation film can be produced by forming each cured layer of the polymerizable liquid crystal compound on the alignment film and laminating the two layers with the adhesive layer or the pressure-sensitive adhesive layer interposed therebetween. After laminating the both, the substrate and the alignment film can be peeled off. The thickness of the retardation film in the present invention is preferably 3 to 30 μm, and more preferably 5 to 25 μm.

< adhesive layer >

The pressure-sensitive adhesive layer may contain a pressure-sensitive adhesive composition containing a resin such as a (meth) acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin as a main component. Among them, the pressure-sensitive adhesive composition is suitable for use as a base polymer of a (meth) acrylic resin excellent in transparency, weather resistance, heat resistance and the like. The adhesive composition may be an active energy ray-curable type or a heat-curable type. The thickness of the adhesive layer is usually 3 to 30 μm, preferably 3 to 25 μm.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, a polymer or copolymer containing, as a monomer, 1 or 2 or more kinds of (meth) acrylic esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate is suitably used. It is preferred to copolymerize the polar monomer to the base polymer. 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, hydroxyethyl (meth) acrylate, meth (acrylamide), N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition may be an adhesive composition comprising only the above-mentioned base polymer, and typically further comprises a crosslinking agent. Examples of the crosslinking agent include: a metal ion having a valence of 2 or more, which forms a metal carboxylate with a carboxyl group; polyamine compounds forming amide bonds with carboxyl groups; polyepoxy compounds or polyols which form ester bonds with carboxyl groups; and a polyisocyanate compound forming an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.

< front Panel >

The front panel is disposed on the viewing side of the polarizing plate. The front panel may be laminated to the polarizing plate via an adhesive layer. Examples of the adhesive layer include the aforementioned adhesive layer and adhesive layer. The front panel may be laminated on the protective film 11 of the polarizing plate 1 via an adhesive layer.

Examples of the front panel include glass, and a window film including a hard coat layer on at least one surface of a resin film. As the glass, for example, high-transmittance glass or tempered glass can be used. In particular, when a thin transparent surface material is used, chemically strengthened glass is preferable. The thickness of the glass may be, for example, 100 μm to 5 mm.

A window film comprising a hard coating on at least one side of a resin film may have flexible characteristics, unlike conventional glass, which is hard and brittle. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 to 100 μm.

The resin film may be a resin film made of a cycloolefin derivative having a unit of a cycloolefin-containing monomer such as a norbornene or polycyclic norbornene-based monomer, cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacrylic acid, polyimide, polyamideimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyvinyl acetate, polyvinyl alcohol, polyvinyl, Films made of polymers such as polycarbonate, polyurethane, and epoxy resin. As the resin film, an unstretched film, a uniaxially stretched film or a biaxially stretched film can be used. These polymers may be used alone or in combination of 2 or more. As the resin film, a polyamideimide film or a polyimide film excellent in transparency and heat resistance, a uniaxially or biaxially stretched polyester film, a cycloolefin derivative film excellent in transparency and heat resistance and capable of coping with the increase in size of the film, a polymethyl methacrylate film, and a triacetyl cellulose and isobutyl cellulose film free from transparency and optical anisotropy are preferable. The thickness of the resin film may be 5 to 200 μm, preferably 20 to 100 μm.

The hard coat layer may be formed by curing a hard coat composition containing a reactive material that forms a cross-linked structure by irradiation of light or thermal energy. The hard coat layer can be formed by curing a hard coat composition containing both a photocurable (meth) acrylate monomer or oligomer and a photocurable epoxy monomer or oligomer. The photocurable (meth) acrylate monomer may include 1 or more selected from epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate. The epoxy (meth) acrylate can be obtained by reacting a carboxylic acid having a (meth) acryloyl group with an epoxy compound.

The hard coating composition may further include one or more selected from a solvent, a photoinitiator, and an additive. The additive may contain one or more selected from inorganic nanoparticles, leveling agents, and stabilizers, and may further contain, for example, an antioxidant, a UV absorber, a surfactant, a lubricant, an antifouling agent, and the like as each component generally used in the art.

< light-shielding Pattern >

The light shielding pattern may be provided as at least a portion of a bezel (bezel) or a case of the front panel or the display device to which the front panel is applied. The light blocking pattern may be formed on the display element side of the front panel. The light shielding pattern can shield each wiring of the display device from a user. The color and/or material of the light-shielding pattern is not particularly limited, and may be formed of a resin substance having a plurality of colors such as black, white, gold, and the like.

In one embodiment, the thickness of the light-shielding pattern may be 2 to 50 μm, may be preferably 4 to 30 μm, and may be more preferably 6 to 15 μm. In addition, in order to suppress the mixing of air bubbles due to the difference in height between the light-shielding pattern and the display portion and the visibility of the boundary portion, the light-shielding pattern may be given a shape.

< method for producing circularly polarizing plate >

A method for manufacturing a circularly polarizing plate will be described with reference to a circularly polarizing plate 100 shown in fig. 1 (a). The circularly polarizing plate 100 can be manufactured by laminating the polarizing plate 1 and the retardation film 2 via the adhesive layer 13.

The polarizing plate 1 can be manufactured by laminating the polarizer 10 and the

protective films

11 and 12 with an adhesive layer interposed therebetween. The polarizing plate may be manufactured by preparing a long member, bonding the members to each other in a roll-to-roll manner, and then cutting the member into a predetermined shape, or by cutting the member into a predetermined shape and bonding the member. After the

protective films

11 and 12 are bonded to the polarizing plate 10, a heating step or a humidity conditioning step may be further provided.

The retardation film 2 can be produced, for example, as follows. An alignment film is formed on a substrate, and a coating liquid containing a polymerizable liquid crystal compound is applied on the alignment film. The polymerizable liquid crystal compound is cured by irradiation with an active energy ray in a state in which the polymerizable liquid crystal compound is aligned. The pressure-sensitive adhesive layer 14 formed on the release film is laminated on the layer obtained by curing the polymerizable liquid crystal compound. Subsequently, the substrate and/or the alignment film are peeled. Next, the adhesive layer 13 formed on the release film is laminated on the protective film 12. The retardation film 2 may be produced by preparing a long member, bonding the members to each other by roll-to-roll method, and then cutting the member into a predetermined shape, or by cutting the member into a predetermined shape and bonding the member.

Then, the release film laminated on the pressure-sensitive adhesive layer 13 is peeled off, and the retardation film 2 is bonded to the polarizing plate 1 via the pressure-sensitive adhesive layer 13, whereby the circularly polarizing plate 100 can be produced.

< use >

The circularly polarizing plate can be used in various display devices. A display device is a device having a display element, and includes a light-emitting element or a light-emitting device as a light-emitting source. Examples of the display device include a liquid crystal display device, an organic EL display device, an inorganic electroluminescence (hereinafter also referred to as an inorganic EL) display device, an electron emission display device (for example, a field emission display device (also referred to as an FED), a surface conduction field emission display device (also referred to as an SED)), the circularly polarizing plate is particularly effectively used for an organic EL display device or an inorganic EL display device, and is also useful as a circular polarizing plate.

Examples

(1) Method for measuring film thickness

The measurement was carried out using a digital micrometer MH-15M manufactured by Nikon corporation.

(2) Method for measuring phase difference value

The measurement was performed using a phase difference measuring apparatus KOBRA-WPR (manufactured by Okins measuring instruments Co., Ltd.).

(3) Shrinkage force of polarizing plate

The resultant was cut into a width of 2mm and a length of 50mm by SUPER CUTTER (manufactured by Amaranthus yedoensis K.K.) so that the absorption axis direction became a long side. The resulting short strip-shaped chip (chip) was used as a test piece. The shrinkage force of the test piece was measured by using a thermomechanical analyzer (model TMA/6100, manufactured by SII Nanotechnology Co.). The measurement was performed in a mode of a predetermined size, and the distance between the jigs was set to 10 mm. After the test piece was left in a chamber at 23 ℃ and 55% RH for 24 hours or more, the temperature in the sample chamber was set as follows: the temperature was raised from 23 ℃ to 80 ℃ in 1 minute, and the temperature in the sample chamber was maintained at 80 ℃ after the temperature rise. After the temperature was raised, the test piece was left for another 4 hours, and then the shrinkage force in the longitudinal direction of the test piece was measured at 80 ℃. In this measurement, the static load was set to 0mN, and a SUS probe was used as a holder.

(4) Size shrinkage speed of circular polarizer

The dimensional shrinkage speed of the circular polarizer was measured in the following manner. The circularly polarizing plate was cut into a size of 50mm in the slow axis direction and 50mm in the fast axis direction of the retardation film. The cut circularly polarizing plate was bonded to alkali-free glass (product name: Eagle XG, manufactured by Corning corporation) having a thickness of 0.4mm, and placed in an oven under a high-temperature and high-humidity environment (temperature 60 ℃ C., relative humidity 95%) for 168 hours. The dimensions of the circular polarizer were measured immediately after removal from the oven to room temperature (temperature 23 ℃, relative humidity 55%). After that, the sheet was stored at room temperature for 24 hours, and then the dimensions of the circularly polarizing plate were measured again, and the shrinkage rate in the slow axis direction of the circularly polarizing plate was calculated from the slope of the dimensional change.

(5) Coefficient of humidity expansion of protective film

The coefficient of humidity expansion of the protective film was measured in the following manner. The protective film was cut into a size of 100mm in the direction corresponding to the slow axis direction of the retardation film provided in the circularly polarizing plate and 100mm in the direction orthogonal to the direction corresponding to the slow axis in the plane, and the length of the protective film at 23 ℃ and 50% RH and at 23 ℃ and 90% RH was measured to measure the coefficient of humidity expansion [ cm/cm/% RH ] according to the following equation.

Coefficient of humidity expansion (L90-L50)/(L50 × Δ H)

Here, L50 is the length (cm) of the protective film in the direction corresponding to the slow axis direction of the retardation film at a temperature of 23 ℃ and a relative humidity of 50% RH, L90 is the length (cm) of the protective film in the direction corresponding to the slow axis direction of the retardation film at a temperature of 23 ℃ and a relative humidity of 90% RH, and Δ H is 40(═ 90 to 50)% RH.

(6) Size shrinkage rate of circular polarizer

The dimensional shrinkage of the circular polarizer was measured in the following manner. The circularly polarizing plate was cut into a size of 50mm in the slow axis direction and 50mm in the fast axis direction of the retardation film. The cut circularly polarizing plate was bonded to alkali-free glass (product name: Eagle XG, manufactured by Corning corporation) having a thickness of 0.4mm, and placed in an oven under a high-temperature and high-humidity environment (temperature 60 ℃ C., relative humidity 95%) for 168 hours. The dimensions of the circularly polarizing plate (initial dimensions) before being put into the oven and the dimensions of the circularly polarizing plate immediately after being taken out of the oven in the slow axis direction were measured using a two-dimensional dimension measuring apparatus, and the dimensional shrinkage of the circularly polarizing plate was calculated from the following equation.

[ production of retardation layer A ]

Composition a for forming an alignment film was obtained by mixing 5 parts (weight average molecular weight: 30,000) of a photo-alignment material having the following structure and 95 parts of cyclopentanone (solvent), and stirring the resulting mixture at 80 ℃ for 1 hour.

To 100 parts of a mixture obtained by mixing a polymerizable liquid crystal compound 1 and a polymerizable liquid crystal compound 2 shown below at a mass ratio of 90: 10, 1.0 part of a leveling agent (F-556; manufactured by DIC corporation) and 6 parts of 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one ("Irgacure 369(Irg 369)", manufactured by BASF ja pan) as a polymerization initiator were added.

Further, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration became 13%, and the mixture was stirred at 80 ℃ for 1 hour to obtain a composition A for forming a liquid crystal cured film.

The polymerizable liquid crystal compound 1 is produced by the method described in jp 2010-31223 a. The polymerizable liquid crystal compound 2 is produced by the method described in Japanese patent laid-open No. 2009-173893. The respective molecular structures are shown below.

(polymerizable liquid Crystal Compound 1)

(polymerizable liquid Crystal Compound 2)

[ production of a laminate comprising a substrate, an alignment film, and a layer obtained by curing a polymerizable liquid Crystal Compound ]

A50 μm thick cycloolefin film (trade name "ZF-14-50" manufactured by ZEON Co., Ltd.) as a base material was subjected to corona treatment. The corona-treated surface was coated with the composition a for forming an alignment film by a bar coater. The coated film was dried at 80 ℃ for 1 minute. The dried coating film was irradiated with polarized UV at an axial angle of 45 ℃ using a polarized UV irradiation apparatus (trade name "SPOT CURE SP-9" manufactured by USHIO MOTOR Co., Ltd.) to obtain an alignment film. The polarized UV irradiation was performed so that the cumulative light amount at the wavelength of 313nm became 100mJ/cm 2.

Next, the composition a for forming a liquid crystal cured film was applied on the alignment film using a bar coater.

The coated film was dried at 120 ℃ for 1 minute. A high-pressure mercury lamp (trade name of usio motor corporation: "Unicure VB-15201 BY-A", and the dried coating film was irradiated with ultraviolet light. The ultraviolet irradiation step was carried out so that the cumulative light amount at a wavelength of 365nm became 500mJ/cm ²The method of (1) is carried out under a nitrogen atmosphere. Operated in this way to obtain a packageA laminate comprising a substrate, an alignment film, and a layer (retardation layer A) obtained by curing a polymerizable liquid crystal compound.

(measurement of phase Difference value)

The retardation layer a has Re (450) of 121nm, Re (550) of 142nm, and Re (650) of 146nm as a retardation value Re (λ) at each wavelength. As a result, Re (450)/Re (550) was calculated to be 0.85, and Re (650)/Re (550) was calculated to be 1.03. The retardation layer A is a layer to which a retardation of lambda/4 is imparted.

[ production of retardation layer B ]

The composition was prepared according to the following procedure. 0.1 part of F-556 as a leveling agent and 3 parts of Irgacure 369 as a polymerization initiator were added to 100 parts of Paliocolor LC242 (registered trademark of BASF corporation) as a polymerizable liquid crystal compound. Cyclopentanone was added so that the solid content concentration became 13%, to obtain composition B for forming a liquid crystal cured film. In addition, as composition B for forming an alignment film, sun SE610 manufactured by nippon chemical industries co.

A50 μm thick cycloolefin film (trade name "ZF-14-50" manufactured by ZEON Co., Ltd.) as a base material was subjected to corona treatment. The corona-treated surface was coated with the composition B for forming an alignment film by a bar coater. The coated film was dried at 80 ℃ for 1 minute to obtain an oriented film.

The composition B for forming a liquid crystal cured film was applied to the alignment film by using a bar coater and dried at 90 ℃ for 120 seconds. The coating film was irradiated with ultraviolet light (cumulative light amount at a wavelength of 365nm in a nitrogen atmosphere: 500 mJ/cm) using a high-pressure mercury lamp ("Unicure VB-15201 BY-A", manufactured BY USHIO Motor Co., Ltd.) ²). In this way, a laminate including a substrate, an alignment film, and a layer (retardation layer B) obtained by curing a polymerizable liquid crystal compound was obtained.

(measurement of phase Difference value)

Rth (550) of the retardation layer B was calculated to be-70 nm. The retardation layer B is a positive C plate.

[ production of retardation film C ]

In the preparation of [ phase difference layer A ]]The laminate thus prepared was subjected to corona treatment (800W, 10 m/min) on the retardation layer ABar width 700mm, 1Pass (1 Pass)). The adhesive composition prepared below was applied to the corona-treated surface using a coater (bar coater manufactured by first physico-chemical company) so that the thickness of the adhesive cured layer became 1 μm, thereby forming an adhesive composition layer. The adhesive composition layer formed on the retardation layer A and the above-mentioned [ preparation of retardation layer B ] were combined by using a sticking apparatus ("LPA 3301" manufactured by FUJIPLA Co., Ltd.)]The retardation layer B obtained in (1) was laminated. The adhesive composition was cured by irradiating ultraviolet light from the side of the retardation layer B with an ultraviolet irradiation apparatus with a conveyor belt (lamp "HValve" manufactured by Fusion UV Systems) to obtain a retardation film C. In the UVA region, the irradiation intensity was set to 390mW/cm ²The cumulative light amount was 420mJ/cm ²In the UVB region, the irradiation intensity was set to 400mW/cm ²The cumulative light amount was 400mJ/cm ². The retardation film C is formed by laminating a base material, an alignment film, a retardation layer a, an adhesive layer, a retardation layer B, an alignment film, and a base material in this order.

[ preparation of adhesive layer ]

The following adhesive layer a and adhesive layer B were prepared.

Adhesive layer a: sheet adhesive having a thickness of 5 μm ("NCF # L2" manufactured by LINTEC Co.)

Adhesive layer B: sheet adhesive having a thickness of 25 μm ("P-3132" manufactured by LINTEC Co.)

[ preparation of adhesive composition ]

The following cationically curable components a1 to a3 were mixed, and then the following cationic polymerization initiator and sensitizer were mixed. The resulting mixture was defoamed to prepare a photocurable adhesive composition. The following compounding amounts are based on the solid content.

Cationic curable component a1(70 parts):

3 ', 4' -epoxycyclohexylmethyl-3 ', 4' -epoxycyclohexanecarboxylate (trade name: CEL2021P, manufactured by Dailuo Co., Ltd.)

Cationic curable component a2(20 parts):

neopentyl glycol diglycidyl ether (trade name: EX-211, manufactured by Nagase ChemteX Co., Ltd.)

Cationic curable component a3(10 parts):

2-ethylhexyl glycidyl ether (trade name: EX-121, manufactured by Nagase ChemteX)

Cationic polymerization initiator (2.25 parts (amount of solid component)):

trade name: CPI-100 (manufactured by San-Apro) 50% propylene carbonate solution

Sensitizer (2 parts):

1, 4-diethoxynaphthalenes

[ preparation of protective film ]

The following protective films were prepared. The humidity expansion coefficients of the protective films C to F are shown in table 1 below.

And (3) protecting the film A:

a film having a hard coat layer of 7 μm thickness (trade name "25 KCHC-HC" of letterpress printing) was formed on a triacetyl cellulose film of 25 μm thickness

And (3) a protective film B:

a film having a hard coat layer of 3 μm thickness (trade name "COP 25 ST-HC" manufactured by Japan paper-making Co., Ltd.) was formed on a stretched film of 25 μm thickness comprising a norbornene resin

And (3) a protective film C:

norbornene resin film having positive birefringence (trade name "ZF 14-023", manufactured by ZEON Co., Ltd.) having a thickness of 23 μm

And (3) a protective film D:

norbornene resin film having a thickness of 13 μm and having positive birefringence (trade name "ZF 14-013" manufactured by ZEON Co., Ltd.) (film)

And (3) a protective film E:

as the methacrylic resin, a copolymer of methyl methacrylate/methyl acrylate at 96%/4% (by weight) was prepared. Further, as the rubber particles, elastomer particles having a three-layer structure were prepared, in which the innermost layer included a hard polymer obtained by polymerizing methyl methacrylate with a small amount of allyl methacrylate, the intermediate layer included a soft elastomer obtained by polymerizing butyl acrylate as a main component with styrene and a small amount of allyl methacrylate, and the outermost layer included a hard polymer obtained by polymerizing methyl methacrylate with a small amount of ethyl acrylate, and the average particle diameter up to the elastomer of the intermediate layer was 240 nm. In the rubber particles, the total weight of the innermost layer and the intermediate layer was 70% of the total weight of the particles. The methacrylic resin 70 wt% and the rubber particles 30 wt% were mixed by a super mixer, and melt-kneaded by a twin-screw extruder to prepare pellets. The pellets were put into a single screw extruder of 65mm phi and extruded through a T die set at 275 ℃ and the film was sandwiched between two polishing rolls having mirror surfaces and cooled to obtain a protective film E of a methacrylic resin film having negative birefringence and a thickness of 40 μm.

And (3) protecting the film F:

triacetyl cellulose film having a thickness of 20 μm (trade name "ZRG 20 SL" from Fuji film Co.)

[ Table 1]

	Coefficient of humidity expansion cm/cm/% RH
		Protective film C	2.6×10 ^-6
Protective film D	2.6×10 ^-6
		Protective film E	4.0×10 ^-5
Protective film F	7.0×10 ^-5

[ preparation of polarizing plate A ]

A polyvinyl alcohol film having a thickness of 30 μm (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) was uniaxially stretched to about 4 times by dry stretching, and then immersed in pure water at 40 ℃ for 40 seconds while being kept under tension, and then immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.052/5.7/100 at 28 ℃ for 30 seconds to perform dyeing treatment. Thereafter, the plate was immersed at 70 ℃ for 120 seconds in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 11.0/6.2/100. Subsequently, the substrate was washed with pure water at 8 ℃ for 15 seconds, and then dried at 60 ℃ for 50 seconds and then at 75 ℃ for 20 seconds while maintaining the tension of 300N, thereby obtaining a polarizing plate A having a thickness of 12 μm, in which iodine was adsorbed and oriented on the polyvinyl alcohol film. The contraction force in the absorption axis direction of the polarizing plate A was 2.08N/2 mm.

[ preparation of polarizing plate B ]

A polyvinyl alcohol film (average degree of polymerization: 2400, degree of saponification: 99.9 mol% or more) having a thickness of 20 μm was uniaxially stretched in the machine direction by about 5 times by dry stretching, and then immersed in pure water at 60 ℃ for 1 minute while being kept under tension, and then immersed in an aqueous solution at 28 ℃ for 60 seconds, wherein the weight ratio of iodine/potassium iodide/water was 0.05/5/100. Thereafter, the plate was immersed in an aqueous solution at 72 ℃ for 300 seconds, wherein the weight ratio of potassium iodide/boric acid/water was 8.5/8.5/100. Subsequently, the substrate was washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃ to obtain a polarizing plate B having a thickness of 7 μm and an oriented iodine adsorbed on the polyvinyl alcohol film. The contraction force in the absorption axis direction of the polarizing plate B was 1.58N/2 mm.

[ example 1]

[ production of polarizing plate ]

An aqueous adhesive was applied to one surface of the polarizing plate a, and the protective film a subjected to saponification treatment was attached. The other surface of the polarizing plate a was coated with an aqueous adhesive, and a protective film C subjected to corona treatment was attached. Thereafter, the resulting film was dried to obtain a polarizing plate. The aqueous adhesive is an aqueous adhesive comprising: 3 parts of carboxyl-modified polyvinyl alcohol [ trade name "KL-318" from Coly) were dissolved in 100 parts of water, and 1.5 parts of a polyamide epoxy additive [ trade name "Sumirez Resin 650 (30)" from Taoka chemical industries, Ltd., an aqueous solution having a solid content of 30%) as a water-soluble epoxy Resin was added.

[ production of circularly polarizing plate ]

The protective film C of the polarizing plate was subjected to corona treatment, and then the adhesive layer a was attached. The substrate on the retardation layer a side of the retardation film C was peeled off, and after the exposed retardation layer a was subjected to corona treatment, the pressure-sensitive adhesive layer a was bonded. The substrate on the side of the retardation layer B was peeled off, and after corona treatment was performed on the exposed retardation layer B, the adhesive layer B was attached to produce a circularly polarizing plate. At this time, the slow axis of the retardation layer a was 45 degrees with respect to the absorption axis of the polarizing plate.

The circularly polarizing plate was cut into a rectangular shape of 140mm × 70mm in size so that the slow axis of the retardation film was parallel to the long side. The cut circularly polarizing plate was bonded to a glass plate (model: EAGLE XG (registered trademark) manufactured by Corning corporation) having a thickness of 0.4mm via an adhesive layer B. Thus, a sample for evaluation was prepared.

[ example 2]

A circularly polarizing plate was produced in the same manner as in example 1 except that the protective film C in example 1 was changed to the protective film E, and a sample for evaluation was produced.

[ example 3]

A circularly polarizing plate was produced in the same manner as in example 1 except that the polarizer a, the protective film a, and the protective film C in example 1 were changed to the polarizer B, the protective film B, and the protective film D, respectively, and samples for evaluation were produced.

Comparative example 1

A circularly polarizing plate was produced in the same manner as in example 1 except that the protective film C in example 1 was changed to the protective film F, and a sample for evaluation was produced.

[ evaluation of reflection color tone ]

The prepared sample for evaluation was put into an oven under a high-temperature and high-humidity environment (temperature 60 ℃ C., relative humidity 95%)) for 168 hours. The sample for evaluation was taken out of the oven and left at room temperature (23 ℃ C., 55% relative humidity) for 24 hours. Thereafter, the reflection color tone of the sample for evaluation was measured.

[ method of measuring reflection color tone ]

As the reflector, MIRO (5011GP) manufactured by ALANOD corporation was prepared. The reflecting plate is a specular reflecting plate having a reflecting surface formed by vapor deposition. The sample for evaluation was placed on the reflecting plate. The reflection color tones (a, b) were measured using a spectrocolorimeter (Konica Minolta JAPAN company, trade name: CM-2600 d). The reflection color tone is a value when the light source is D65, and is measured by the SCI method (including regular reflection).

Specifically, point 5 shown in fig. 2 is set as a measurement point. The 9 dots 5 shown in fig. 2 are dots in a region inside 5mm from the end of the circularly polarizing plate, which are present at intervals of about 30mm in the short side direction and at intervals of about 65mm in the long side direction. The evaluation samples prepared in examples 1 to 3 and comparative example 1 were measured for reflection color tone under the measurement conditions described above for the evaluation of reflection color tone, and the absolute value of the color tone change Δ a × b at each point was calculated. The color tone change value of each point was calculated based on the direction of color tone change, and the difference between the maximum value and the minimum value of the color tone change value of each evaluation sample was defined as Δ a × b (MAX-MIN).

Δ a ═ a (after moisture and heat resistance test) — a (before moisture and heat resistance test)

Δ b ═ b (after moisture resistance test) — b ═ b (before moisture resistance test)

Δa*b*＝〔(Δa*) ²+(Δb*) ²〕 ^1/2

Note that, regarding the color tone change value, Δ a × b is assumed when Δ a is 0 or more, and Δ a × b × (-1) is assumed when Δ a is less than 0.

The above results are shown in table 2.

[ Table 2]

Industrial applicability

According to the present invention, a circularly polarizing plate can be provided which shows little change in reflection color tone even when placed in a room temperature environment after being placed in a high temperature and high humidity environment.

Claims

1. A circularly polarizing plate comprising a polarizing plate and a retardation film laminated on each other,

the polarizing plate is provided with a polarizer and a protective film,

the size shrinkage speed of the circular polarizer is 4.1 multiplied by 10 ^-4mm/hour or less.

2. The circularly polarizing plate according to claim 1, wherein the polarizing plate has a protective film disposed between the polarizer and the phase difference film.

3. The circularly polarizing plate of claim 1 or 2, wherein the shape of the main surface is substantially rectangular,

4. The circularly polarizing plate according to any one of claims 1 to 3, wherein the retardation film comprises a layer obtained by curing a polymerizable liquid crystal compound,

5. The circularly polarizing plate according to any one of claims 1 to 4, further comprising a display panel.

6. The circularly polarizing plate of claim 5, which is bendable.

7. The circularly polarizing plate according to claim 5 or 6, further comprising a touch sensor and a window film,

which is sequentially laminated with a display panel, the touch sensor, a polarizing plate, and the window film.

8. The circularly polarizing plate according to claim 5 or 6, further comprising a touch sensor,

the display panel, the polarizing plate and the touch sensor are sequentially stacked.

9. The circularly polarizing plate according to claim 8, further comprising a window film,

10. A display device, wherein the circularly polarizing plate according to any one of claims 1 to 9 is laminated on a display element via an adhesive layer.