KR20220055425A - Polarizing plate and display device - Google Patents

Abstract

[Problem] To provide a polarizing plate excellent in impact resistance even when configured in a thin shape, and a polarizing plate highly compatible with impact resistance and bending resistance.
[Solution] A polarizing plate in which a protective film and a polarizer are laminated, wherein the protective film has a puncture elastic modulus of 200 g/mm or more and 550 g/mm or less, and a thickness of 25 µm or less, and the polarizer comprises polyvinyl alcohol A polarizing plate containing a system resin and boron, the boron content being 4.5 mass% or less, and used for a flexible display device.

Description

Polarizing plate and display device {POLARIZING PLATE AND DISPLAY DEVICE}

The present invention relates to a polarizing plate used for a flexible display device, and further to a flexible display device provided with the same.

BACKGROUND ART As an input device, a display device having a touch sensor function is used in small electronic devices such as smartphones. Since such a display device is used in small electronic devices, it is necessary to reduce the size and thickness of the display device. In addition, data input is performed by touching the display surface with a fingertip or a pen, so that when the display surface is touched by a fingertip or the like, A characteristic such as not to deteriorate becomes necessary. Therefore, the impact resistance of the display apparatus to the extent which can suppress deterioration by the contact of a display surface is calculated|required, and impact resistance is also calculated|required by the member applied to the said display apparatus by this. Moreover, in recent years, the flexible display apparatus in which the said display apparatus can be folded attracts attention. In addition to impact resistance, the member applied to such a flexible display device is required to have a degree of flexibility that can be bent. In patent document 1, it is a laminated body for flexible display devices containing an adhesive layer and an optical film, The storage elastic modulus G' in 25 degreeC of the adhesive layer of the convex-side outermost surface at the time of bending a laminated body is another adhesive A laminate characterized by being substantially equal to or smaller than the storage modulus G' at 25°C of the layer is disclosed.

[Patent Document 1] Japanese Patent Laid-Open No. 2018-028573

As mentioned above, the member (polarizing plate etc.) used for the display apparatus with a touch sensor function used for a small electronic device is calculated|required that it is excellent in impact resistance. In addition, when flexibility of a display device is requested|required, in addition to being thin and easy to bend, the polarizing plate used for the said display device (flexible display device) is calculated|required that it does not deteriorate significantly by bending|flexion of a practical number of times. That is, the polarizing plate which is strong in an impact, and also strong in an impact and bending|flexion by extension is calculated|required. What has a protective film excellent in mechanical strength, such as a tensile elasticity modulus, has been widely used by such a polarizing plate until now. However, the thin polarizing plate (polarizing plate excellent in bending resistance) was not particularly satisfactory in terms of impact resistance. An object of the present invention is to provide a polarizing plate excellent in impact resistance even if configured in a thin shape, particularly a polarizing plate excellent in impact resistance and bending resistance even if configured in a thin shape.

The present inventors have surprisingly found that, in a polarizing plate applied to a flexible display device, if the protective film constituting the polarizing plate has a specific piercing elastic modulus and thickness, in combination with a specific polarizer, excellent impact resistance and resistance It discovered that a flexibility was compatible. Then, the present invention provides the following polarizing plate and flexible display device.

[1] A polarizing plate in which a protective film and a polarizer are laminated,

The protective film has a puncture modulus of 200 g/mm or more and 550 g/mm or less, and a thickness of 25 µm or less,

The said polarizer contains polyvinyl alcohol-type resin and boron, boron content is 4.5 mass % or less, The polarizing plate used for a flexible display device.

[2] The polarizing plate according to [1], wherein the polarizer has a boron content of 3.0 mass% or more.

[3] The polarizing plate according to [1] or [2], wherein the polarizer has a thickness of 12 µm or less.

[4] The polarizing plate according to any one of [1] to [3], wherein the protective film has a water vapor transmission rate of 300 g/(m 2 ·24 hours) or less at a temperature of 40°C and a relative humidity of 92% RH.

[5] The polarizing plate according to any one of [1] to [4], wherein the protective film is made of a (meth)acrylic resin.

[6] The polarizing plate according to any one of [1] to [5], further comprising a retardation body disposed on the side opposite to the protective film side of the polarizer.

[7] The polarizing plate according to [6], wherein the retardation body has a layer formed by curing a polymerizable liquid crystal compound.

[8] The polarizing plate according to any one of [1] to [7], wherein the polarizing plate has a thickness of 40 µm or less.

[9] A display device comprising the polarizing plate according to any one of [1] to [8].

[10] A flexible display device comprising the polarizing plate according to any one of [1] to [8].

ADVANTAGE OF THE INVENTION According to this invention, even if comprised in a thin shape, when comprised with the polarizing plate excellent in impact resistance, and further, when comprised in the thickness enough to be applicable to a flexible display device, the polarizing plate excellent in impact resistance and bending resistance can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows typically one form of the polarizing plate of this invention.
2 is a schematic cross-sectional view schematically showing another embodiment of the polarizing plate of the present invention.
Fig. 3 is a schematic view of a paste-attached base (hereinafter, sometimes referred to as a "stick-attached base") having a void used for measurement of the puncture elastic modulus when viewed from the top.
4 : (a) is a schematic perspective view which shows the principal part at the time of bonding a measurement film to the base|base with glue, (b) is a figure which shows typically the upper part after bonding a measurement film to the base|base with glue.
Fig. 5 is a diagram schematically showing a cross section when a needle is pierced into a sample (hereinafter, sometimes referred to as a "base with a measurement film") after bonding the measurement film to the paste-attached base.
Fig. 6 is a view schematically showing a cross section when the puncture elastic modulus is measured, and (a) and (b) show a state in which the film is deformed by puncturing the film with a needle.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, referring drawings, this invention is not limited to the following embodiment. In all the drawings below, the scales are appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawings does not necessarily coincide with the scale of the actual component.

<Polarizer>

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows typically one form of the polarizing plate of this invention. The polarizing plate 100 illustrated in FIG. 1 includes a protective film 20 and a polarizer 10 . 2 is a schematic cross-sectional view schematically showing another embodiment of the polarizing plate of the present invention. The polarizing plate 200 illustrated in FIG. 2 includes a protective film 20 , a polarizer 10 , an interlayer bonding layer 40 , and a retardation plate 30 . The retardation plate 30 includes the first retardation layer 31 and the second retardation layer 32 in this order from the polarizer 10 side. The structure in which the 1st phase difference layer 31 and the 2nd phase difference layer 32 are joined by the interlayer bonding layer 33 may be sufficient. The polarizing plates 100 and 200 may further include an interlayer bonding layer (not shown) for bonding the respective layers shown in Figs. 1 and 2, and other layers other than those shown in Figs. You may have more.

The polarizing plates 100 and 200 can be highly compatible with impact resistance and flexibility, if the thickness of the protective film 20 is as mentioned later. The polarizing plates 100 and 200 in this case can be bent (henceforth "infold") with the protective film 20 side inside. In this specification, it is assumed that a polarizing plate can be bent, without generating a crack in the polarizer 10 even if it bends by infold with a bending radius of 3 mm that it can bend. As a curved shape of the polarizing plates 100 and 200 , a bending radius is not limited. Further, the bending includes a form of refraction in which the refraction angle of the inner surface is greater than 0° and less than 180°, and a form of folding in which the bending radius of the inner surface is close to zero or the refraction angle of the inner surface is 0°. Since the thickness of the protective film 20 can bend the polarizing plate of this invention as mentioned later and is excellent in flexibility, it is suitable for a flexible display device.

The polarizing plates 100 and 200 may have a rectangular shape, for example, in plan view, preferably a rectangular shape having a long side and a short side, and more preferably a rectangular shape. As for each layer which comprises the polarizing plate 100, a corner part may be R-processed, an edge part may be cut-processed, or the perforation process may be carried out.

The polarizing plates 100 and 200 have a specific thickness of a protective film, and have bending resistance suitable for a flexible display device. Although the range suitable for the thickness of the whole polarizing plate changes with layer structure, Preferably it is 40 micrometers or less, More preferably, it is 30 micrometers or less. When the thickness of the polarizing plates 100 and 200 is 40 μm or less, further thinning of the polarizing plate can be realized, and further thinning of the flexible display device can be realized, and a flexible display device that is strong in bending (excellent in bending resistance) can be realized In addition, the thickness of the whole polarizing plate here is the sum total of the thickness of the polarizer 10 which comprises the said polarizing plate, and the protective film 20, and the sum total of the thickness of the interlayer bonding layer which bonds these together. As a method for realizing the thickness reduction of the polarizing plates 100 and 200, a method of reducing the thickness of each layer (including the interlayer bonding layer), a method of reducing the total number of layers, etc. are mentioned, and specifically, protection Methods, such as making the thickness of the film 20 into 20 micrometers or less, making the thickness of the polarizer 10 into 12 micrometers or less, setting it as the structure which is not equipped with protective films other than the protective film 20 are mentioned .

[Flexibility Resistance]

Hereinafter, the polarizing plate of this invention WHEREIN: In addition to impact resistance, making compatible highly bending resistance suitable for a flexible display device is demonstrated in detail. In order to implement|achieve the flexible display apparatus excellent in bending resistance, the polarizing plate applied to the said flexible display apparatus must also be excellent in bending resistance.

Polarizing plates 100 and 200, when repeated bending is performed with an infold having a bending radius of 3 mm in an environment of a temperature of 25° C., the number of bending times at which cracks are first generated in the polarizing plates 100 and 200 is preferably is 100,000 or more, more preferably 200,000 or more, and still more preferably 300,000 or more. The present inventors acquired the knowledge that a crack is easy to generate|occur|produce in the protective film used as inner side, when bending|flexion was repeated by infold in a polarizing plate. The present inventors provide a polarizing plate having excellent bending resistance by using, as the protective film 20, a resin film that does not generate cracks or has a crack length of 5 mm or less in the bending resistance test described in detail in Examples. confirmed that it is possible. ADVANTAGE OF THE INVENTION According to this invention, in the environment of a temperature of 25 degreeC, even if it bends 100,000 times by infold with a bending radius of 3 mm, the polarizing plate which can suppress generation|occurrence|production of the crack in a polarizing plate can be provided.

[Impact resistance]

The polarizing plates 100 and 200 have excellent impact resistance. ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate excellent in the impact resistance which a crack does not generate|occur|produce in a polarizer in the impact resistance test using the pen for evaluation described in detail in an Example can be provided.

[protective film]

The protective film 20 has a function of protecting the surface of the polarizer 10 . The polarizing plates 100 and 200 can be used by arrange|positioning and using the visual recognition side of a display element in a flexible display device. In the polarizing plates 100 and 200 , the protective film 20 may be disposed and used so as to be on the viewing side rather than the polarizer 10 .

The protective film 20 has a puncture elastic modulus of 200 g/mm or more and 550 g/mm or less. The puncture elastic modulus of the protective film 20 becomes like this. Preferably it is 230 g/mm or more, More preferably, it is 250 g/mm or more, Especially preferably, it is 300 g/mm or more, More preferably, it is 530 g/mm. or less, more preferably 500 g/mm or less, still more preferably 450 g/mm or less, and particularly preferably 400 g/mm or less. By using the protective film having the puncture modulus as described above as the protective film 20 , a polarizing plate having excellent impact resistance and bending resistance can be provided even when a protective film having a thickness of 20 μm or less is used.

Here, although it describes also in an Example, the means for measuring the puncture elastic modulus of a protective film is demonstrated, referring drawings. In the present specification, the puncture elastic modulus is 0.33 cm/ using a measurement sample in which the protective film is joined to a paste-attached base in which the central portion is cut into a square of 30 mm × 30 mm, and a needle having a tip diameter of 1 mm φ 0.5 R At the speed of seconds, the amount of displacement due to the bending in the puncture direction of the protective film measured when the protective film is punctured perpendicularly to the surface of the protective film and fractured is defined as the deformation amount S (mm), and the stress applied to the protective film is As the proportionality constant between the stress F and the strain S (stress F/strain S) when F(g), Equation (1):

Punching modulus A(g/mm) = F(g)/S(mm) (One)

It is a physical property value calculated by . The measurement of the puncture elastic modulus can be performed using a compression tester equipped with a load cell, and examples of the compression tester include a puncture tester "NDG5" manufactured by Katotech Co., Ltd., a handy compression tester "KES-G5", Inc. Shimadzu Corporation's small tabletop tester "EZTest" etc. are mentioned. From the stress-strain curve obtained by using such a compression tester, the stress applied to the film at the time of fracture and the amount of strain generated in the film up to that point can be measured. In addition, the fracture|rupture which generate|occur|produces in a film at the time of pressing a piercing jig|tool includes the case where a through-hole generate|occur|produces in a film by the tip of a jig|tool. Specifically, as described in Examples, the measurement of the puncture elastic modulus is performed using a measurement sample in which a film is bonded to a paste-attached base having a void portion cut out in a square of 30 mm × 30 mm in the center portion, and is located in the void portion. A needle having a tip diameter of 1 mm φ 0.5 R in the approximately center of the film is pierced at a speed of 0.33 cm/sec approximately perpendicular to the surface of the film, and is measured when fracture occurs. The displacement amount is calculated by the above formula (1) from the deformation amount S (mm) and the stress F (g) applied to the film.

A principal part is demonstrated about the measuring means of the puncture elastic modulus at the time of using the puncture test machine "NDG5" by the Katotech Corporation using drawing.

3 : is the schematic diagram which looked at the base|base with glue (the base|base with glue 7) which has a space|gap part for calculating|requiring the puncture elastic modulus of a protective film from upper direction. The paste-attached base 7 is a 30 mm x 30 mm square cutout (gap) that serves as a portion for bonding a protective film used for measurement (hereinafter, also referred to as "measurement film 12") in the central portion. (6)).

4 : is a schematic diagram which shows the principal part at the time of bonding the measurement film 12 to the base|plate 7 with glue, (a) is a perspective view when bonding the measurement film 12 to the base|base 7 with glue. , (b) is the schematic diagram which looked at the mounting plate 1 with a measurement film after bonding the measurement film 12 to the mounting plate 7 with a glue from upper direction (direction A of Fig.4 (a)). The dotted line indicates the outer periphery 8 of the void portion 6 . The position M at which the needle N is pierced, which is located in the approximately central portion of the cavity 6, connects the points R and R' that are opposed in the oblique direction of the outer periphery 8 of the cavity 6 It is the intersection of two straight lines. Fig. 5 schematically shows a cross-sectional view along I-I' (before the needle N is pierced) in the measurement film-attached base 1 .

The needle N is pierced at approximately the center M of the measurement film 12 (eg, the intersection of two diagonal lines connecting R and R' among the vertices of the outer periphery 8 of the void portion of FIG. 4(b) ). In such a puncture, the stress F(g) applied to the needle N is correlated with the amount of deformation S (mm) due to the bending in the puncture direction of the film, and the stress F(g) when the film breaks and From the amount of deformation S (mm), the puncture elastic modulus is calculated according to the above formula (1). When the puncture elastic modulus is calculated, when fracture occurs in a state in which deformation occurs in the film (when fracture occurs in the state of Fig. 6(a)), when fracture occurs in a state in which further deformation occurs in the film (Fig. 6) (b) occurs when fracture occurs), but the elastic modulus of the puncture in the present invention is obtained from the applied stress in the puncture testing machine and the amount of deformation S, and the amount of deformation S is shown in Fig. 6(a) S may be sufficient when fracture occurs in the state of , or S when fracture occurs in the state of FIG. 6(b) may be sufficient. Moreover, since the applied stress changes from an upward tendency to a downward tendency when a fracture|rupture generate|occur|produces in a film, it can be understood that a fracture|rupture generate|occur|produced at this change point.

In the paste-attached base 7, the glue for fixing the measurement film is not particularly limited as long as it can prevent the measurement film from peeling off even partially from the measuring film-attached base during the puncture elastic modulus measurement. You may conduct an appropriate preliminary experiment in order to find the glue of the glue|sticker base 7 used for the puncture elastic modulus measurement.

The protective film 20 has a thickness of 25 µm or less, and preferably 20 µm or less. If the thickness of this protective film 20 is 25 micrometers or less, and the puncture elastic modulus is an above-mentioned range, surprisingly, it becomes the thing excellent in the impact resistance of the polarizing plate obtained. Moreover, in addition to impact resistance as the thickness is 20 micrometers or less, a flexible polarizing plate can be obtained. The lower limit of the thickness of the protective film 20 is, for example, 8 µm or more, preferably 10 µm or more, and particularly preferably 15 µm or more. When the thickness of the protective film 20 is 25 µm or less, the thin polarizing plates 100 and 200 can be easily formed.

As described above, the protective film 20 has a thin thickness and a moisture permeability at a temperature of 40°C and a relative humidity of 92% RH, preferably 300 g/(m 2 ·24 hours) or less, more preferably 250 g /(m²·24 hours) or less. When the moisture permeability of the protective film 20 is in the above-mentioned range, it is difficult to cause displacement of the end position between the polarizer 10 and the protective film 20 even in a moist heat environment, so that a polarizing plate having excellent moisture and heat resistance can be provided. there is.

As the protective film 20, for example, a resin film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, stretchability, and the like may be used. The resin film may be a thermoplastic resin film. As a specific example of such resin, Cellulose-type resin, such as a triacetyl cellulose; polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate; polyether sulfone-based resin; polysulfone-based resin; polycarbonate-based resin; polyamide-based resins such as nylon and aromatic polyamide; polyimide-based resin; polyolefin resins such as polyethylene, polypropylene, and ethylene/propylene copolymer; Cyclic polyolefin resin (also referred to as norbornene resin) having a cyclo-based and norbornene structure; (meth)acrylic resin; polyarylate-based resins; polystyrene-based resin; polyvinyl alcohol-based resins, and mixtures thereof. The protective film 20 of this material is available in the market, and the protective film 20 applied to the present invention by selecting one having a thickness of 20 μm or less from among these commercially available products, and obtaining the puncture elastic modulus by the above method. select In addition, the commercial item of the protective film 20 WHEREIN: The specific value of thickness is about ±10% of thickness precision, Preferably it is a value which allows about ±5%.

As the protective film 20, the protective film which consists of (meth)acrylic-type resin is used suitably from a viewpoint of being easy to obtain the thing of the range mentioned above with respect to water vapor transmission rate while being thin. The protective film which consists of (meth)acrylic-type resin is especially preferable from the point from which the thing of the moderate puncture elastic modulus is obtained while thickness is thin. Such an effect is remarkable when the thickness is 15-25 micrometers in the protective film which consists of (meth)acrylic-type resin.

The protective film 20 may have a protective layer that is an organic material layer or an inorganic material layer. The organic layer may be formed using a composition for forming a protective layer, for example, a (meth)acrylic resin composition, an epoxy resin composition, a polyimide resin composition, or the like. An active energy ray hardening type may be sufficient as the composition for protective layer formation, and a thermosetting type may be sufficient as it. The inorganic layer may be formed of, for example, silicon oxide. When the protective layer is an organic substance layer, the protective layer may be called a hard coat layer. By providing a protective layer in a protective film with high water vapor transmission rate, the water vapor transmission rate of the said protective film can also be reduced. In this way, the protective film in which the protective layer was formed has an effect that it is easy to obtain the thing of the preferable range mentioned above with respect to water vapor transmission rate, although thickness is thin.

When the protective film 20 has a protective layer of an organic material layer, for example, an active energy ray-curable composition for forming a protective layer is applied on a base film, and the protective layer is prepared by curing by irradiation with active energy. can The base film may be left as a component of the protective film 20, or may be peeled off and removed. As a base film, the above-mentioned resin film can be used. As a method of apply|coating the composition for protective layer formation, the spin coating method etc. are mentioned, for example. When the protective film 20 has a protective layer of an inorganic material layer, the protective layer may be formed by, for example, a sputtering method, a vapor deposition method, or the like.

[Polarizer]

The polarizer 10 has a function to selectively transmit linearly polarized light from non-polarized light rays such as natural light. The polarizer 10 included in the polarizing plate 100 or the polarizing plate 200 of the present invention contains a polyvinyl alcohol-based resin and boron. It is preferable that the polarizer 10 is the stretched film which made the dichroic dye adsorb|suck. When the dichroic dye is dispersed in a polymer chain (polyvinyl alcohol-based resin chain) having anisotropy caused by stretching, it may be seen as colored from a certain direction and almost colorless from a direction perpendicular to it. As a dichroic dye, an iodine is used suitably. Moreover, as a stretched film to which the dichroic dye was adsorbed, other than the polarizer obtained by adsorbing and extending|stretching a dichroic dye to the resin film of a single-piece|unit, for example, as described in Unexamined-Japanese-Patent No. 2012-73563, ester type thermoplasticity A polarizer can also be manufactured by forming a polyvinyl alcohol-based resin layer on the same base film (thermoplastic resin film) as a resin base material, stretching this resin layer through the base material, and adsorbing and orienting the dichroic dye. . Hereinafter, the polarizer obtained by such a method may be called "stretched layer". In addition, the general method for manufacturing this stretched layer is mentioned later.

When the polarizer 10 is a stretched layer, as shown above, since it is manufactured using an appropriate base film (thermoplastic resin film), the polarizer as the stretched layer is supported with a base film (thermoplastic resin film). As for the polarizing plates 100 and 200, the structure in which the base film which supports the polarizer 10 becomes the protective film 20 of the polarizer 10 may be sufficient.

The polarizer 10 preferably has a contractile force of 2.4 N/2 mm or less, and more preferably 2.1 N/2 mm or less. If the contractile force of the polarizer 10 is within the above-described numerical range, cracks are unlikely to occur in the polarizer 10 even when subjected to an impact, and a polarizing plate having excellent impact resistance can be provided. Moreover, the shrinkage|contraction of the polarizer 10 in a wet heat environment can be suppressed. The contractile force of the polarizer 10 is 1.0 N/2 mm or more normally. The contraction force of the polarizer 10 is measured by the method described in Examples to be described later. The contractile force of the polarizer 10 can be adjusted by content of boron mentioned later, when the polarizer 10 is a stretched film or a stretched layer manufactured using the polyvinyl alcohol-type resin film (layer). Moreover, it is controllable also with the kind and the quantity of the dichroic dye to be used. When the polarizer 10 is a liquid crystal layer, it can be controlled by the degree of crosslinking of the polymerizable liquid crystal compound constituting the liquid crystal layer. Among these, it is preferable that the polarizer 10 contains polyvinyl alcohol-type resin also from the point which is easy to control a contractile force.

Hereinafter, the polarizer 10 containing a polyvinyl alcohol-type resin is also called "polyvinyl alcohol-type resin containing polarizer." A polyvinyl alcohol-based resin-containing polarizer having a boron content (hereinafter referred to as "boron content") of 4.5 mass % or less is preferable, and it is more preferable in it being 4.3 mass % or less. When the boron content is within the numerical range described above, cracks hardly occur in the polarizer 10 even when subjected to an impact, and a polarizing plate having excellent impact resistance can be provided. Moreover, the shrinkage|contraction of the polarizer 10 in a wet heat environment can be suppressed. The boron content of the polarizer 10 can be made into 2.5 mass % or more, for example, and it is preferable that it is 3.0 mass % or more. The boron content of the polarizer 10 containing this polyvinyl alcohol-type resin is ratio of the mass of the boron to contain with respect to the total mass of a polarizer, and the measuring means is mentioned later.

(A polarizer that is a stretched film or stretched layer to which a dichroic dye is adsorbed)

Here, the manufacturing method of a polyvinyl alcohol-type resin containing polarizer is demonstrated briefly. The polarizer, which is a stretched film to which a dichroic dye is adsorbed, is a step of uniaxially stretching a polyvinyl alcohol-based resin film, dyeing a polyvinyl alcohol-based resin film with a dichroic dye such as iodine, a step of adsorbing the dichroic dye, It can manufacture through the process of treating the polyvinyl alcohol-type resin film to which the dichroic dye has adsorbed with the aqueous boric acid solution, and the process of washing with water after the process with the aqueous boric acid solution. Such a polyvinyl alcohol-based resin film (before uniaxial stretching) is readily available in the market, and as will be described later, a polyvinyl acetate-based resin is produced by a known means, saponified, and polyvinyl alcohol-based resin may be produced and the polyvinyl alcohol-based resin may be formed into a film. In addition, the polyvinyl acetate-based resin may be formed into a film at the stage of the polyvinyl acetate-based resin, and the polyvinyl acetate-based resin contained in the film may be saponified.

The boron content of the polyvinyl alcohol-based resin-containing polarizer is determined by the above-described manufacturing method when the polyvinyl alcohol-based resin-containing polarizer is produced. In particular, the polyvinyl alcohol-based resin film to which the dichroic dye is adsorbed is used as an aqueous solution of boric acid. It can be controlled by adjusting the conditions of the process to be treated. For example, boron content of polyvinyl alcohol-type resin containing polarizer is controllable by changing the density|concentration and usage-amount of the boric acid in the said boric-acid aqueous solution, or changing the temperature of boric-acid aqueous solution. A suitable preliminary experiment can be performed and the conditions from which a polyvinyl alcohol-type resin containing polarizer becomes desired boron content can also be derived|led-out.

The thickness of a polarizer is 30 micrometers or less normally, Preferably it is 18 micrometers or less, More preferably, it is 12 micrometers or less. Making the thickness of the polarizer thin is advantageous for thinning the polarizing plates 100 and 200 . The thickness of the polarizer is usually 1 µm or more, for example, 5 µm or more may be sufficient. The thickness of such a preferable polarizer is controllable from the thickness of the raw material film (before extending|stretching) before setting it as a stretched film, and a draw ratio, when a polarizer is the stretched film to which the dichroic dye was adsorbed. As mentioned later, when a polarizer is the stretched layer to which the dichroic dye was adsorbed, it is controllable from the thickness of the coating film formed on the base material, and a draw ratio.

The thickness of the polarizer can be measured, for example, with a contact-type film thickness meter, as shown in Examples to be described later.

Polyvinyl alcohol-type resin is obtained by saponifying polyvinyl acetate-type resin. As polyvinyl acetate-type resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, the copolymer of vinyl acetate and the other monomer copolymerizable to it is used. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acid-based compounds, olefin-based compounds, vinyl ether-based compounds, unsaturated sulfone-based compounds, and (meth)acrylamide-based compounds having an ammonium group.

The saponification degree of polyvinyl alcohol-type resin is about 85 mol% or more and 100 mol% or less normally, Preferably it is 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may also be used. The polymerization degree of polyvinyl alcohol-type resin is 1000 or more and 10000 or less normally, Preferably they are 1500 or more and 5000 or less.

A polyvinyl alcohol-based resin-containing polarizer, which is a stretched layer to which a dichroic dye is adsorbed, is usually a step of applying a coating liquid containing the polyvinyl alcohol-based resin on a base film to obtain a laminated film, and uniaxially stretching the obtained laminated film process, dyeing the polyvinyl alcohol-based resin layer of the uniaxially stretched laminated film with a dichroic dye, adsorbing the dichroic dye to the resin layer to form a polarizer, treating the resin layer to which the dichroic dye is adsorbed with an aqueous solution of boric acid It can manufacture through the process of doing and the process of washing with water after the process by boric-acid aqueous solution. You may use the base film used in order to form a polarizer as a protective film on a polarizer. You may peel and remove a base film from a polarizer as needed. The material and thickness of a base film may be the same as the material and thickness of the protective film 20 mentioned later. In addition, in the production of a polyvinyl alcohol-based resin-containing polarizer that is a stretched layer to which the dichroic dye is adsorbed, by controlling the amount of boric acid used in the process of treating with an aqueous boric acid solution described later, the boron content of the polarizer 10 is You can do it in any range you want.

Although iodine and organic dye can be used as a dichroic dye, As a dichroic dye used for the polarizer of this invention, an iodine is especially preferable.

In the case of using iodine as a dichroic dye, a polyvinyl alcohol-based resin film or a laminated film including a base film and a polyvinyl alcohol-based resin film is immersed in a dyeing bath containing iodine and potassium iodide normally, Vinyl alcohol-based resin is dyed with iodine. The content of iodine in this dyeing bath may be about 0.003 to 1 parts by mass per 100 parts by mass of water. The content of potassium iodide may be about 0.15 to 20 parts by mass per 100 parts by mass of water. In addition, the temperature of the dyeing bath may be about 10 to 45 ℃.

In the step of treating a polyvinyl alcohol-based resin film to which a dichroic dye, particularly an iodine is adsorbed, or a laminated film including a polyvinyl alcohol-based resin film and a base film with an aqueous boric acid solution, usually polyvinyl to which a dichroic dye is adsorbed The alcohol-based resin film is immersed in an aqueous boric acid solution (crosslinking bath). As the boric acid source contained in the boric acid aqueous solution, a boron compound such as boric acid or borax is used. Moreover, you may use crosslinking agents, such as glyoxal and glutaraldehyde, together with a boron compound. As the solvent of the aqueous boric acid solution, water can be used, but an organic solvent compatible with water may be further included. In order to adjust the boron content of a polarizer, it is preferable that the density|concentration of the boric acid in boric-acid aqueous solution shall be 3-8 mass %, and the immersion time to a crosslinking bath is adjusted suitably, and the density|concentration of boric acid shall be 4-7 mass %. It is more preferable to set it as and to adjust the immersion time to a crosslinking bath suitably.

The aqueous boric acid solution may further include iodide. By addition of iodide, the polarization|polarized-light performance in the plane of the polarizer obtained can be made uniform more. Specific examples of iodide are the same as described above. The density|concentration of the iodide in boric-acid aqueous solution becomes like this. Preferably it is 0.1-20 mass parts.

The crosslinking treatment with an aqueous boric acid solution is usually 40 to 80°C, preferably 50 to 70°C. When the temperature is too low, the progress of the crosslinking reaction tends to be insufficient. On the other hand, when the temperature is too high, the film tends to be cut in the crosslinking treatment bath, and processing stability tends to be remarkably reduced. Moreover, the time of a crosslinking process is 10-600 second normally, Preferably it is 60-420 second, More preferably, it is 90-300 second. The conditions of this crosslinking treatment are adjusted according to the desired boron content, as will be described later.

In addition to being excellent in the impact resistance of the polarizing plates 100 and 200 that the boron content in the polarizer 10 is the above-mentioned range, it is advantageous in the point of the crack resistance improvement of the polarizing plates 100 and 200, and furthermore, a polarizer It can also be advantageous in terms of the optical properties of It is thought that boron in the polarizer exists in a free state as boric acid (H ₃ BO ₃ ), or exists in a state in which boric acid forms a cross-linked structure with a unit of polyvinyl alcohol-based resin. The boron content is the amount of the boron atom (B) itself including those present in the state of the compound in this way.

The boron content in a polarizer quantifies the amount of boron by, for example, after dissolving the said polarizer in pure water, adding mannitol, and performing titration with sodium hydroxide aqueous solution with respect to the obtained solution, the mass of the said polarizer It can be calculated as a mass percentage of the amount of boron with respect to . In addition, the amount of boron in the polarizer can be quantified by high-frequency inductively coupled plasma (ICP) emission spectroscopy, and it can also be calculated as a mass percentage of boron with respect to the mass of the polarizer.

When a flexible display device is an organic electroluminescent (organic electroluminescent) display device, the polarizing plate of this invention can also combine a phase difference plate further, and can also use it as a circularly polarizing plate which is an antireflection plate of an organic electroluminescent display. Hereinafter, this retardation plate is demonstrated.

[Phase difference]

The polarizing plate 200 may have a function as a circularly polarizing plate by providing the polarizer 10 and the retardation plate 30 . Hereinafter, a configuration including the polarizer 10 and the retardation plate 30 is also referred to as a circularly polarizing plate. Incidentally, the retardation plate may also be referred to as a retardation body.

The retardation plate 30 includes a first retardation layer 31 and a second retardation layer 32 . It is preferable that the 1st retardation layer 31 and the 2nd retardation layer 32 are joined by the interlayer bonding layer 33. As shown in FIG. Even if the 1st retardation layer 31 and the 2nd retardation layer 32 have an overcoat layer which protects the surface, and the base film etc. which support the 1st retardation layer 31 and the 2nd retardation layer 32, good. As the first retardation layer 31 and the second retardation layer 32 , for example, a retardation layer (λ/4 layer) imparting a retardation of λ/4, a retardation layer (λ/2 layer) imparting a retardation of λ/2 ) and a positive C layer. The retardation plate 30 preferably includes a λ/4 layer, and more preferably includes at least one of a λ/4 layer, a λ/2 layer, or a positive C layer.

In the retardation plate 30 , a first retardation layer 31 and a second retardation layer 32 are sequentially stacked from the polarizer 10 side. When the retardation plate includes a λ/2 layer, the first retardation layer 31 is a λ/2 layer, and the second retardation layer 32 is a λ/4 layer. When the retardation plate 30 includes a positive C layer, the first retardation layer 31 is a positive C layer, and the second retardation layer 32 is a λ/4 layer, or the first retardation layer 31 This is a λ/4 layer, and the second retardation layer 32 is a positive C layer. The thickness of the retardation plate 30 is, for example, 0.1 µm or more and 50 µm or less, preferably 0.5 µm or more and 30 µm or less, and more preferably 1 µm or more and 10 µm or less.

The first retardation layer 31 and the second retardation layer 32 may be formed from the resin films exemplified as the material for the resin film of the above-described protective film, or may be formed from a layer formed by curing the polymerizable liquid crystal compound. The 1st retardation layer 31 and the 2nd retardation layer 32 may contain the orientation film and the base film in addition to the layer formed by hardening|curing a polymeric liquid crystal compound.

When the first retardation layer 31 and the second retardation layer 32 are formed as a layer formed by curing a polymerizable liquid crystal compound, a composition containing the polymerizable liquid crystal compound is applied to a base film and cured to form. can You may form an orientation film between a base film and an application layer. The material and thickness of the base film may be the same as the material and thickness of the resin film. When the first retardation layer 31 and the second retardation layer 32 are formed as a layer formed by curing a polymerizable liquid crystal compound, they may be incorporated into the laminate in a form having an alignment film and a base film.

The polarizing plate in which the polarizer 10 and the retardation plate 30 are arranged so that the absorption axis of the polarizer 10 and the slow axis of the retardation plate 30 are at a predetermined angle has an antireflection function, that is, it functions as a circular polarizer can do. When the retardation plate 30 includes the λ/4 layer, an angle between the absorption axis of the polarizer 10 and the slow axis of the λ/4 layer may be 45°±10°. The first retardation layer 31 and the second retardation layer 32 may have forward wavelength dispersion or reverse wavelength dispersion. The λ/4 layer preferably has reverse wavelength dispersion. The polarizer 10 and the retardation plate 30 may be joined by the interlayer bonding layer 40 .

[Interlayer bonding layer]

In the polarizing plates 100 and 200, in order to bond two layers together, an interlayer bonding layer can be used between the layers. In FIG. 2 , the interlayer bonding layer 40 is used in order to bond the polarizer 10 and the retardation plate 30 together. Moreover, in the retardation plate 30, in order to bond the 1st retardation layer 31 and the 2nd retardation layer 32, the interlayer bonding layer 33 is used. The interlayer bonding layer can be an adhesive layer or an adhesive layer. The interlayer bonding layer 40 is preferably an adhesive layer, and the interlayer bonding layer 33 is preferably an adhesive layer.

The thickness of the interlayer bonding layer is not particularly limited, but when an adhesive layer is used as the interlayer bonding layer, it is preferably 1 µm or more, may be 5 µm or more, and is usually 50 µm or less, and may be 25 µm or less. When an adhesive layer is used as the interlayer bonding layer, the thickness of the interlayer bonding layer is preferably 0.1 µm or more, may be 0.5 µm or more, preferably 10 µm or less, and may be 5 µm or less.

As used herein, the term "adhesive" refers to a liquid that is in a liquid state after the curing reaction, and can be adhered only by applying a small amount of pressure at room temperature for a short time, for example, also referred to as a pressure-sensitive adhesive. On the other hand, in this specification, "adhesive" refers to an adhesive other than an adhesive (pressure-sensitive adhesive), the state after the curing reaction is solid, and the range of the elastic modulus after curing is 100 MPa or more. One layer may be sufficient as the adhesive layer used for an interlayer bonding layer, or what consists of two or more layers may be sufficient, However, Preferably it is one layer.

The pressure-sensitive adhesive layer may be composed of a pressure-sensitive adhesive composition mainly containing a resin such as (meth)acrylic type, rubber type, urethane type, ester type, silicone type, or polyvinyl ether type. Especially, the adhesive composition which uses the (meth)acrylic-type resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. An active energy ray hardening type or a thermosetting type may be sufficient as an adhesive composition.

As the (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition, for example, (meth) butyl acrylate, (meth) ethyl acrylate, (meth) acrylate isooctyl, (meth) acrylate 2-ethylhexyl The polymer or copolymer which uses 1 type(s) or 2 or more types of acrylic acid ester as a monomer is used suitably. It is preferable to copolymerize a polar monomer with a base polymer. Examples of the polar monomer include (meth)acrylic acid, (meth)acrylic acid 2-hydroxypropyl, (meth)acrylic acid hydroxyethyl, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, glycy The monomer which has a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc. like dil (meth)acrylate is mentioned.

The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. As a crosslinking agent, it is a divalent or more metal ion, Comprising: What forms a carboxylate metal salt between a carboxyl group; A polyamine compound that forms an amide bond between a carboxyl group; It is a polyepoxy compound or a polyol, Comprising: What forms an ester bond between a carboxyl group; As a polyisocyanate compound, what forms an amide bond between a carboxyl group is illustrated. Especially, a polyisocyanate compound is preferable.

The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays or electron beams, has adhesiveness even before active energy ray irradiation, and can be brought into close contact with an adherend such as a film, and can be irradiated with active energy rays It is a pressure-sensitive adhesive composition having a property that can be cured by the adhesion can be adjusted. It is preferable that an active energy ray hardening-type adhesive composition is an ultraviolet curable type. In addition to a base polymer and a crosslinking agent, an active energy ray hardening-type adhesive composition contains an active energy ray polymeric compound further. Moreover, a photoinitiator, a photosensitizer, etc. may be made to contain as needed.

The pressure-sensitive adhesive composition includes fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders and other inorganic powders, etc.), antioxidants, It may contain additives such as ultraviolet absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

An adhesive layer can be formed by apply|coating the organic solvent dilution liquid of the said adhesive composition on a base material, and drying it. When an active energy ray hardening-type adhesive composition is used, it can be set as the hardened|cured material which has a desired degree of hardening by irradiating an active energy ray to the formed adhesive layer.

As an adhesive agent, it can form, for example by combining 1 type(s) or 2 or more types of a water-based adhesive agent, an active-energy-ray-curable adhesive agent, etc. Examples of the water-based adhesive include a polyvinyl alcohol-based resin aqueous solution, a water-based two-part type urethane-based emulsion adhesive, and the like. Active energy ray-curable adhesive is an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, and includes, for example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, a binder resin, and a photoreactive crosslinking agent. and adhesives. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and an oligomer derived from these monomers. As said photoinitiator, the compound containing the substance which irradiates active energy rays, such as an ultraviolet-ray, and generate|occur|produces active species, such as a neutral radical, an anion radical, and a cationic radical, is mentioned.

[Method for producing a polarizing plate]

The polarizing plates 100 and 200 can be manufactured by a method including the process of bonding a polarizer and a protective film together through the interlayer bonding layer formed with a suitable adhesive agent. When bonding layers through an interlayer bonding layer, it is preferable to perform surface activation treatment, such as corona treatment, with respect to one or both surfaces of a bonding surface for the purpose of adjusting adhesive force. The conditions of corona treatment can be set suitably, and the conditions may differ in one surface and the other surface of a bonding surface. Moreover, after performing a process like corona treatment to a protective film, for example, without using an interlayer bonding layer, a corona-treated protective film and a polarizer can also be bonded. Thus, bonding of a polarizer and a protective film can select an optimal thing suitably according to the kind of protective film.

[display device]

The polarizing plate according to the present invention can be used for a display device, and can also be used for a flexible display device. A display device can be set as the structure provided with a display element and the polarizing plate laminated|stacked on the visual recognition side of a display element. A display apparatus is not specifically limited, For example, image display apparatuses, such as an organic electroluminescent display apparatus, an inorganic electroluminescent display apparatus, a liquid crystal display device, and an electroluminescent display apparatus, are mentioned. The display device may have a touch panel function. The polarizing plate is suitable for a flexible display device having flexibility that can be bent or bent. In a display device, a polarizing plate is arrange|positioned so that the protective film 20 may be located on the visual recognition side rather than the polarizer 10 on the visual recognition side of a display element.

The display device according to the present invention can be used as mobile devices such as smartphones and tablets, televisions, digital photo frames, electronic signs, measuring instruments and instruments, office equipment, medical equipment, computer equipment, and the like. It is particularly suitable as a display device mounted on a mobile device that requires

[Example]

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[Measurement of thickness]

The thickness of the polarizer was measured with a contact-type film thickness meter [trade name "DIGIMICRO (registered trademark) MH-15M' manufactured by Nikon Corporation]].

[Polarizer]

(Production of polarizer a)

A polyvinyl alcohol film having a thickness of 20 µm, a degree of polymerization of 2400 and a degree of saponification of 99% or more was uniaxially stretched on a hot roll at a draw ratio of 4.1, and while maintaining the tension state, 0.05 parts by mass of iodine and 5 parts by mass of potassium iodide per 100 parts by mass of water was immersed in a dyeing bath at 28° C. for 60 seconds.

Then, it was immersed in the boric-acid aqueous solution 1 containing 5.5 mass parts of boric acid and 15 mass parts of potassium iodide per 100 mass parts of water at 64 degreeC for 110 second. Then, it was immersed in the boric-acid aqueous solution 2 containing 3.9 mass parts of boric acid and 15 mass parts of potassium iodide per 100 mass parts of water at 67 degreeC for 30 second. Then, it washed with water using 10 degreeC pure water, it was made to dry, and the polarizer a was obtained. The obtained polarizer a had a thickness of 8 µm, a contractile force of 1.8 N/2 mm, and a boron content of 3.6 mass%.

(Production of polarizer b)

Polarizer b was produced by the method similar to the polarizer a except the point which changed boric-acid content of the boric-acid aqueous solution 2 into 2.3 mass parts per 100 mass parts of water. The obtained polarizer b had a thickness of 8 µm, a contractile force of 1.5 N/2 mm, and a boron content of 3.0 mass%.

(Production of polarizer c)

The polarizer c was produced by the method similar to the polarizer a except the point which changed boric-acid content of the boric-acid aqueous solution 2 into 5.5 mass parts per 100 mass parts of water. The obtained polarizer c had a thickness of 8 µm, a contractile force of 2.1 N/2 mm, and a boron content of 4.3 mass%.

(production of polarizer d)

Polarizer d was produced by the method similar to the polarizer a except the point which changed boric-acid content of the boric-acid aqueous solution 2 into 6.8 mass parts per 100 mass parts of water. The obtained polarizer d had a thickness of 8 µm, a contractile force of 2.5 N/2 mm, and a boron content of 5.0 mass%.

(Production of polarizer e)

Polarizer e was produced by the method similar to the polarizer a except the point which changed boric-acid content of the boric-acid aqueous solution 2 into 1.5 mass parts per 100 mass parts of water. The obtained polarizer e had a thickness of 8 µm, a contractile force of 1.2 N/2 mm, and a boron content of 2.5 mass%.

(Measurement of boron content of polarizer)

0.2 g of the polarizer was dissolved in 200 g of a 1.9 mass% mannitol aqueous solution. The obtained aqueous solution was titrated with 1 mol/L NaOH aqueous solution, and the boron content of a polarizer was computed by comparison with the quantity of the NaOH liquid required for neutralization, and a calibration curve.

(Measurement of the contractile force of the polarizer)

The polarizer was cut out with a super cutter (manufactured by Ogino Seiki Seisakusho) into a rectangle of 2 mm short side and 50 mm long side so that the slow axis of the polarizer coincided with the long side, and it was set as the test piece. The contractile force of the test piece was measured using a thermomechanical analyzer (manufactured by SI Nanotechnology Co., Ltd., model TMA/6100). This measurement is carried out in the dimension constant mode (the distance between chucks is 10 mm), and after leaving the test piece in a room at 20°C for a sufficient time, the temperature setting in the room of the sample is increased from 20°C to 80°C in 10 minutes. After the temperature was raised, it was set to maintain the indoor temperature of the sample at 80 °C. After the temperature was raised and left to stand for another 4 hours, the contractile force in the long side direction of the test piece was measured under an environment of 80°C. In this measurement, the static load was set to 0 mN, and a probe made of SUS was used for the jig.

[Preparation of adhesive 1]

To 100 parts by mass of water, 3 parts by mass of carboxyl group-modified polyvinyl alcohol (Kurare, Co., Ltd., trade name "KL-318") is dissolved, and in the aqueous solution, a polyamide epoxy resin additive (Taoka Chemical) A water-based adhesive was prepared by adding 1.5 parts by mass of Kogyo Corporation, trade name "Sumirez Resin (registered trademark) 650 (30), an aqueous solution having a solid content concentration of 30 mass%). Let this water-based adhesive agent be adhesive 1.

[Preparation of adhesive 2]

Polyester urethane (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: SUPERFLEX 210, solid content: 33%) 16.8 g, crosslinking agent (oxazoline-containing polymer, manufactured by Nippon Shokubai, Ltd., trade name: Epocross) (EPOCROS) WS-700, solid content: 25%) 4.2 g, 1 mass% aqueous ammonia 2.0 g, colloidal silica (manufactured by Fuso Chemical Industries, Ltd., Quartron PL-3, solid content: 20 mass%) ) 0.42 g and 76.6 g of pure water were mixed to obtain an adhesive composition. Let this adhesive composition be the adhesive agent 2.

[protective film]

(Preparation of protective film a)

As the protective film a, a film made of triacetyl cellulose (TAC) having a thickness of 20 µm (manufactured by Konica Minolta, Ltd., trade name “KC2CT”) was used.

(Preparation of protective film b)

The pellet of the thermoplastic resin containing a norbornene polymer (glass transition point 137 degreeC) was dried at 100 degreeC for 5 hours. The pellets were fed to an extruder, melted in the extruder, and extruded from a T die into a film on a casting drum through a polymer pipe and a polymer filter. The extruded resin was cooled in a casting drum to obtain a long unstretched film having a thickness of 55 µm and a width of 1500 mm. The thus-obtained unstretched film was stretched in the longitudinal direction at a stretching temperature of 145°C and a draw ratio of 1.5 to obtain a long longitudinally stretched film having a thickness of 45 µm and a width of 1000 mm.

The manufacturing apparatus provided with the tenter extending|stretching apparatus provided with the inner clip chain and the outer clip chain, and the oven which covered this tenter extending|stretching apparatus was prepared. The above-described longitudinally stretched film was continuously supplied as a resin film to the tenter stretching apparatus, and diagonal stretching was performed. The stretching conditions were a draw ratio of 2.0 times, a draw temperature of 142°C, and the tension ratio Tin/Tout×100 of the inner clip chain and the outer clip chain was 105%. Thereby, a long diagonally stretched film having a thickness of 22 µm and a width of 1330 mm was obtained. The acrylic hard coat with a thickness of 3 micrometers was coated on the surface of the obtained stretched film, and the 25-micrometer-thick protective film b was obtained.

(Preparation of protective film c)

The pellets of the thermoplastic resin containing norbornene polymer (glass transition point 137 degreeC) were dried at 100 degreeC for 5 hours. The pellets were fed to an extruder, melted in the extruder, and extruded from a T die into a film on a casting drum through a polymer pipe and a polymer filter. The extruded resin was cooled in a casting drum to obtain a long, unstretched film having a thickness of 50 µm and a width of 1500 mm. The thus-obtained unstretched film was stretched in the longitudinal direction at a stretching temperature of 145°C and a draw ratio of 1.5 to obtain a long, vertically stretched film having a thickness of 40 µm and a width of 1000 mm.

The manufacturing apparatus provided with the tenter extending|stretching apparatus provided with the inner clip chain and the outer clip chain, and the oven which covered this tenter extending|stretching apparatus was prepared. The above-described longitudinally stretched film was continuously supplied as a resin film to the tenter stretching apparatus, and diagonal stretching was performed. The stretching conditions were a draw ratio of 2.1 times, a draw temperature of 142°C, and the tension ratio Tin/Tout×100 of the inner clip chain and the outer clip chain was 105%. Thereby, the protective film c of 18 micrometers in thickness and 1330 mm in width was obtained.

(Preparation of protective film d)

Acrylic resin [glass transition temperature: 135 ° C., melt viscosity: 700 Pa·s (temperature 270 ° C., shear rate 100 (1/sec))] a single screw extruder (φ = 20.0 mm, L/D = 25) And melt-extruded at 280 ° C. using a coat hanger type T die (width 150 mm), and the resin composition in the molten state was discharged to a cooling roll maintained at 110 ° C., to form an acrylic resin film with a thickness of 80 μm. Next, on one surface of the acrylic resin film, the easily-adhesive composition obtained above was applied using a bar coater, and then put into a hot air dryer and dried at 100° C. for 90 seconds. And the said film was uniaxially stretched (draw ratio: 4 times) using the table stretching machine, and the 20-micrometer-thick protective film d was obtained.

(Preparation of protective film e)

The acrylic hard coat with a thickness of 3 micrometers was coated on the surface of the protective film d, and the 23 micrometers thickness protective film e was obtained.

(Measurement of moisture permeability of protective film)

The water vapor transmission rate of the protective film was measured at a temperature of 40°C and a relative humidity of 92% RH by the cup method specified in JIS Z 0208. Table 1 shows the results.

(Measurement of the puncture elastic modulus of the protective film)

A measurement sample is prepared by bonding the protective film to be measured to a base with glue cut out in a square of 30 mm x 30 mm at the center. The central portion of the protective film adhered to the cut-out portion of the paste-attached base was pierced substantially perpendicularly to the surface of the protective film at a speed of 0.33 cm/sec with a needle having a tip diameter of 1 mmφ 0.5 R. Then, the amount of displacement due to the bending in the puncture direction of the protective film measured at the time when the breakage occurred is the deformation amount S (mm), the stress applied to the protective film is F (g), the stress F is divided by the deformation amount S The puncture elastic modulus A (g/mm) was calculated|required. That is, the puncture elastic modulus was calculated|required by the following formula|equation (1). Table 1 shows the results.

Punching modulus A (g/mm) = F (g)/S (mm) (One)

(Test of flex resistance of protective film)

The protective film to be measured was subjected to an evaluation test to confirm durability against bending at a temperature of 25°C using a bending evaluation facility (STS-VRT-500, manufactured by Science Town). The bending axis was determined, the bending radius was 1.5 mm along the bending axis, and the area on both sides of the bending axis was bent until they faced each other so as to be parallel, and then the operation of releasing the bending was repeated 135,000 times. Then, the length of the crack generated along the bending axis was measured. Table 1 shows the results.

[Preparation of the phase body]

(1) Preparation of “alignment layer/first liquid crystal cured layer”

A λ/4 retardation layer (first liquid crystal cured layer), which is a layer formed on the base film, in which the alignment layer and the nematic liquid crystal compound were cured, was prepared. In addition, the total thickness of "alignment layer/1st liquid-crystal hardened layer" was 2 micrometers.

(2) Preparation of “alignment layer/second liquid crystal cured layer”

As a composition for forming an alignment layer, 10.0 parts by mass of polyethylene glycol di(meth)acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-600) and trimethylolpropane triacrylate (Shin-Nakamura Chemical Co., Ltd.) Corporation make, A-TMPT) 10.0 mass part, 10.0 mass part of 1, 6- hexanediol di(meth)acrylate (Shin-Nakamura Chemical Industry Co., Ltd. make, A-HD-N) 10.0 mass part, and a photoinitiator 1.50 mass parts of Gacure 907 (made by BASF, Irg-907) was melt|dissolved in 70.0 mass parts of solvent methyl ethyl ketone, and the coating liquid for orientation layer formation was prepared.

As a base film, an elongate cyclic olefin resin (COP) film (manufactured by Nippon Zeon Corporation) having a thickness of 20 µm was prepared, and a coating solution for forming an alignment layer was applied to one side of the base film with a bar coater.

After the coating layer after coating is heat-treated at a temperature of 80° C. for 60 seconds, ultraviolet (UVB) is irradiated with 220 mJ/cm 2 , the composition for forming an alignment layer is polymerized and cured, and the thickness of 2.3 μm on the base film An alignment layer was formed.

As a composition for forming a retardation layer, 20.0 parts by mass of a photopolymerizable nematic liquid crystal compound (manufactured by Merck, RMM28B) and 1.0 parts by mass of Irgacure 907 (manufactured by BASF, Irg-907) as a photoinitiator, solvent propylene glycol mono It was melt|dissolved in 80.0 mass parts of methyl ether acetate, and the coating liquid for phase difference layer formation was prepared.

On the alignment layer obtained previously, the coating liquid for phase difference layer formation was apply|coated, and the heat treatment for 60 second was performed at the temperature of 80 degreeC to the application layer. Then, 220 mJ/cm 2 of ultraviolet (UVB) was irradiated to polymerize and harden the composition for forming a retardation layer, and a 0.7 µm-thick retardation layer (second liquid crystal cured layer) was formed on the alignment layer. In this way, the "alignment layer/2nd liquid crystal hardened layer" with a total thickness of 3 micrometers was obtained on the base film.

(3) Production of phase difference body

The "alignment layer / 1st liquid crystal cured layer" laminated|stacked on the base film, and the "alignment layer / 2nd liquid crystal cured layer" laminated|stacked on the base film are each liquid crystal with an ultraviolet curing adhesive (thickness 1 micrometer). It was joined so that the hardened layer surface (surface on the opposite side to a base film) might become a bonding surface. Then, ultraviolet ray was irradiated to harden an ultraviolet curable adhesive, and the retardation body containing the liquid crystal hardened layer of 2 layers of a 1st liquid crystal hardened layer and a 2nd liquid crystal hardened layer was produced.

[Examples 1 to 7, Comparative Examples 1 to 2]

The polarizing plate of the structure shown in FIG. 2 was produced using the protective film shown in Table 2, the polarizer shown in Table 2, and the retardation body mentioned above. The obtained polarizing plate had the function of a circularly polarizing plate.

[Impact resistance test]

From the polarizing plate of each Example and Comparative Example, a small piece having a rectangular size of 150 mm long x 70 mm short was cut out using a super cutter. The retardation body side surface of the small piece was bonded to an acrylic plate through an adhesive layer. Then, under an environment of a temperature of 23° C. and a relative humidity of 55% RH, the evaluation pen is placed at a height of 5 cm from the outermost surface of the protective film of the small piece and the pen tip is held downward, and the evaluation pen is maintained from that position. was dropped against the fragment. As the pen for evaluation, a pen having a mass of 11 g and a diameter of a pen tip of 0.7 mm was used. About the small piece after dropping the pen for evaluation, visual observation was performed, and the following reference|standard evaluated. Table 2 shows the evaluation results.

A: There are no cracks and scratches on the polarizer and the protective film.

B: There is no crack in the polarizer, and there is a wound in the protective film.

C: There is a wound in the polarizer.

[Evaluation of bending resistance]

About the bending resistance of the polarizing plate of each Example and a comparative example, the following reference|standard evaluated based on the result of the bending resistance test of the used protective film. Table 2 shows the evaluation results.

A: About a protective film, a crack does not generate|occur|produce in a bending resistance test (crack length is 0 mm).

B: About a protective film, the crack length in a bending resistance test is more than 0 mm and 5 mm or less.

C: About a protective film, the crack length in a flex resistance test is more than 5 mm.

[Moisture and heat resistance test]

From the polarizing plate of each Example and Comparative Example, a small piece having a rectangular size of 140 mm long x 65 mm short was cut out using a super cutter. The phase difference body side surface of the small piece was bonded to the alkali-free glass plate using the hand roller through the adhesive layer. This test piece was put into a constant temperature and humidity chamber with a temperature of 65°C and a relative humidity of 90% RH, and was taken out after standing still for 500 hours. The polarizing plate and the standard polarizing plate of the test piece were arranged in a cross nicol, the vicinity of the corner of the polarizing plate of the test piece was observed with an optical microscope, the iodine loss length from the polarizer end was measured, and the following criteria evaluated. Table 2 shows the evaluation results.

A: Less than 0.3 mm in length of iodine removal at the end

B: 0.3 mm to less than 0.6 mm in length of end iodine extraction

C: 0.6 mm or more in length of end iodine extraction

In addition, in Examples 1 to 3, Examples 5, 7, and Comparative Example 2, the polarizer and the protective film (PMMA) were bonded through the bonding layer formed of the adhesive 2, and in Example 4, the polarizer and the protective film ( TAC) was bonded through the bonding layer formed of Adhesive 1.

In Example 6, when bonding a polarizer and a protective film (COP), the surface of the said protective film was corona-treated and it bonded without passing through the bonding layer.

In Comparative Example 1, when bonding a polarizer and a protective film (COP), the surface of the said protective film was corona-treated and it bonded without passing through the bonding layer.

1: Base with measuring film 6: Gap
7: Attachment of grass 8: Outer perimeter
10: Polarizer 12: Measurement film
20: protective film 30: retardation plate
31: first retardation layer 32: second retardation layer
33, 40: interlayer bonding layer 100, 200: polarizing plate
N: Needle M: Needle (N) piercing position
S: amount of deformation

Claims (10)

A polarizing plate in which a protective film and a polarizer are laminated, the polarizing plate comprising:
The protective film has a piercing elastic modulus of 200 g/mm or more and 550 g/mm or less, and a thickness of 25 µm or less,
The said polarizer contains polyvinyl alcohol-type resin and boron, boron content is 4.5 mass % or less, The polarizing plate used for a flexible display device. The polarizing plate according to claim 1, wherein the polarizer has a boron content of 3.0 mass% or more. The polarizing plate according to claim 1 or 2, wherein the polarizer has a thickness of 12 μm or less. The polarizing plate according to any one of claims 1 to 3, wherein the protective film has a water vapor transmission rate of 300 g/(m 2 ·24 hours) or less at a temperature of 40°C and a relative humidity of 92% RH. The polarizing plate according to any one of claims 1 to 4, wherein the protective film is made of a (meth)acrylic resin. The polarizing plate according to any one of claims 1 to 5, further comprising a retardation body disposed on a side opposite to the protective film side of the polarizer. The polarizing plate according to claim 6, wherein the retardation body has a layer formed by curing a polymerizable liquid crystal compound. The polarizing plate according to any one of claims 1 to 7, wherein the polarizing plate has a thickness of 40 μm or less. A display device provided with the polarizing plate in any one of Claims 1-8. The flexible display device provided with the polarizing plate in any one of Claims 1-8.

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