JP2023118963A - Retardation film with easily adhesive layer, polarizing plate with retardation layer, and method of manufacturing retardation film with easily adhesive layer - Google Patents

Abstract

To provide a retardation film with an easily adhesive layer in which breakage during manufacturing is suppressed and phase difference unevenness is small.SOLUTION: A retardation film with an easily adhesive layer of the present invention includes: a substrate film having an in-plane retardation; and an easily adhesive layer provided on at least one surface of the substrate film. The ratio T1/T2 of the average thickness T1 of the easily adhesive layer to the average thickness T2 of the substrate film is 0.011 or less. The maximum thickness of the easily adhesive layer is 1.20 or less and the minimum thickness is 0.80 or more with respect to the average thickness T1 of the easily adhesive layer.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an easy-adhesion layer-attached retardation film, a retardation layer-attached polarizing plate, and a method for producing an easy-adhesion layer-attached retardation film.

In recent years, with the spread of thin displays, image display devices (organic EL display devices) equipped with organic EL panels have been proposed. Since the organic EL panel has a highly reflective metal layer, problems such as reflection of external light and reflection of the background tend to occur. Therefore, it is known to prevent these problems by providing a polarizing plate with a retardation layer (circularly polarizing plate) on the viewing side. Further, it is known that the viewing angle is improved by providing a polarizing plate with a retardation layer on the viewing side of the liquid crystal display panel. As a general polarizing plate with a retardation layer, a retardation film and a polarizer (substantially, a polarizing plate) are arranged so that the slow axis and the absorption axis are at a predetermined angle (e.g., 45°) according to the application. ) is known. Moreover, as a representative retardation film, there is known a retardation film in which a slow axis is expressed in the stretching direction by stretching a resin film (Patent Document 1). In the production of a polarizing plate with a retardation layer, in order to ensure sufficient adhesion between the polarizing plate and the retardation film, there is a case where a retardation film with an easy-adhesion layer is used in which an easy-adhesion layer is provided on the retardation film. be. However, the easily adhesive layer-attached retardation film often causes retardation unevenness. Furthermore, breakage during stretching poses a problem in the production of a retardation film with an easily adhesive layer.

Japanese Patent No. 3325560

The present invention has been made to solve the above-described conventional problems, and the object thereof is to suppress breakage during production, and to provide a retardation film with an easy-adhesion layer with small retardation unevenness. It is to provide a polarizing plate with a retardation layer provided with a retardation film with an easy-adhesion layer, and a method for producing such a retardation film with an easy-adhesion layer.

A retardation film with an easy-adhesion layer according to an embodiment of the present invention includes a base film having an in-plane retardation; and an easy-adhesion layer provided on at least one surface of the base film. The ratio T ₁ /T ₂ of the average thickness T ₁ of the easy-adhesion layer to the average thickness T ₂ of the base film is 0.011 or less, and the easy-adhesion layer has an average thickness T ₁ of The adhesive layer has a maximum thickness of 1.20 or less and a minimum thickness of 0.80 or more.
In one embodiment, the base film is a stretched polycarbonate-based resin film.
In one embodiment, the easy-adhesion layer-attached retardation film is elongated, and the substrate film is an obliquely stretched polycarbonate-based resin film. In one embodiment, the base film has a slow axis in the direction of 30° to 60° with respect to the longitudinal direction.
In one embodiment, the in-plane retardation Re(550) of the base film is 100 nm to 190 nm.
In one embodiment, the easy-adhesion layer is a solidified layer of a water-based resin coating film. In one embodiment, the water-based resin is a urethane-based resin.
According to another aspect of the present invention, a polarizing plate with a retardation layer is provided. This retardation layer-attached polarizing plate has a polarizing plate and the easy-adhesion layer-attached retardation film bonded to the polarizer via an adhesive layer and the easy-adhesion layer. The base film functions as a retardation layer.
In one embodiment, the adhesive layer is composed of an active energy ray-curable adhesive.
According to still another aspect of the present invention, there is provided a method for producing the retardation film with an easy-adhesion layer. This manufacturing method comprises forming a coating film by applying a coating liquid for forming an easy-adhesion layer to a resin film; drying the coating film; and stretching a laminate of the resin film and the dry coating film. ; and the solid content concentration of the coating liquid for forming an easy-adhesion layer is 0.5% by weight to 3.0% by weight.

According to the embodiment of the present invention, in the retardation film with an easy-adhesion layer, the ratio of the average thickness of the easy-adhesion layer to the average thickness of the base film is set to a predetermined value or less, and the variation in the thickness of the easy-adhesion layer is set to a predetermined value. By setting it within the range, it is possible to suppress breakage during production and to realize a retardation film with an easily adhesive layer with small retardation unevenness.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing explaining the retardation film with an easily bonding layer by one Embodiment of this invention.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols used herein are as follows.
(1) refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and "ny" is the in-plane direction orthogonal to the slow axis (i.e., fast axis direction) and "nz" is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re(λ)” is an in-plane retardation measured at 23° C. with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Thickness direction retardation (Rth)
“Rth(λ)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of λ nm. For example, “Rth(550)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is obtained by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to a reference direction. Thus, for example, "45°" means ±45°.

A. Retardation film with easily adhesive layer A-1. 1. Overall Configuration of Retardation Film with Easily Adhesive Layer FIG. 1 is a schematic cross-sectional view illustrating a retardation film with an easily adhesive layer according to one embodiment of the present invention. The easy-adhesion layer-attached retardation film 10 of the illustrated example includes a base film 11 and an easy-adhesion layer 12 provided on one surface of the base film 11 . Depending on the purpose, the easy-adhesion layer may be provided on both sides of the base film. The base film 11 has an in-plane retardation.

In an embodiment of the present invention, the ratio T ₁ /T ₂ between the average thickness T ₁ of the easy-adhesion layer and the average thickness T ₂ of the base film is 0.011 or less, preferably 0.009 or less. , more preferably 0.008 or less, and still more preferably 0.006 or less. A lower limit for the ratio T ₁ /T ₂ can be, for example, 0.003. If the ratio T ₁ /T ₂ is within such a range, breakage during production of the retardation film with an easily adhesive layer can be suppressed.

Furthermore, in the embodiment of the present invention, the maximum thickness of the easy-adhesion layer is 1.20 or less, preferably 1.15 or less, more preferably 1.15 or less with respect to the average thickness _T1 of the easy-adhesion layer. It is 10 or less, more preferably 1.05 or less. The minimum thickness of the easily bonding layer is 0.80 or more, preferably 0.85 or more, more preferably 0.90 or more, and still more preferably 0.95 or more. If the ratio of the maximum thickness and the minimum thickness to the average thickness of the easy-adhesion layer (that is, the thickness variation of the easy-adhesion layer) is within such a range, it is possible to realize an easy-adhesion layer-attached retardation film with small retardation unevenness. can. In the present specification, the “average thickness” means the average of values measured at intervals of 50 mm along each of the direction of a pair of opposing sides of a 1 m × 1 m size film or membrane and the direction perpendicular to the direction. .

A-2. Base Film The base film has an in-plane retardation as described above. That is, the base film is a retardation film. In one embodiment, the base film (retardation film) can function as a λ/4 plate. In this case, the in-plane retardation Re (550) of the substrate film (retardation film) is preferably 100 nm to 190 nm, more preferably 110 nm to 180 nm, and still more preferably 130 nm to 160 nm.

The base film typically has refractive index properties of nx>ny≧nz. Here, "ny=nz" includes not only the case where ny and nz are completely equal but also the case where they are substantially equal. Therefore, it is possible that ny<nz to the extent that the effects of the present invention are not impaired. The Nz coefficient of the base film is preferably 0.9 to 3.0, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, particularly preferably 0 .9 to 1.3. If the Nz coefficient of the base film is in such a range, the retardation film with an easy-adhesion layer (substantially, the polarizing plate with a retardation layer containing the retardation film with an easy-adhesion layer) to an image display device. When used, very good reflection hues can be achieved.

The base film may exhibit a reverse wavelength dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may well exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes even with the wavelength of the measurement light. In one embodiment, the base film exhibits inverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the base film is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With such a configuration, when the retardation film with an easy-adhesion layer (substantially, a polarizing plate with a retardation layer containing the retardation film with an easy-adhesion layer) is used in an image display device, the Excellent antireflection properties can be achieved.

The thickness (average thickness) of the base film can be appropriately set according to the application and purpose. The average thickness is preferably 15 μm to 60 μm, more preferably 25 μm to 45 μm. If the average thickness of the base film is in such a range, the ratio T ₁ /T ₂ is set to the desired range while setting the average thickness of the base film and the easy adhesion layer to a practically acceptable range. It is easy to do. Further, according to the embodiment of the present invention, for example, for large screen applications, the λ/4 plate can be formed with a thickness smaller than usual. According to the embodiment of the present invention, the effect is remarkable in such a thin retardation film.

The base film is typically made of a stretched resin film. In one embodiment, the stretching process is uniaxial stretching. In this case, the base film has a slow axis in the stretching direction, and the base film (as a result, the retardation film with an easy-adhesion layer) may be in the form of a sheet or a long shape. good. In another embodiment, the stretching process is diagonal stretching. In this case, the base film has a slow axis in a direction oblique to the longitudinal direction. The oblique direction is preferably 30° to 60°, more preferably 40° to 50°, still more preferably 42° to 48°, particularly preferably about 45° with respect to the longitudinal direction of the base film. be. In this case, the substrate film (as a result, the easy-adhesion layer-attached retardation film) is typically elongated. Since the polarizer usually has an absorption axis in the longitudinal direction, with such a configuration, the polarizing plate with the retardation layer can be produced by roll-to-roll, and the production efficiency of the polarizing plate with the retardation layer is remarkably improved. can be improved to

As the resin constituting the base film, any suitable resin can be used as long as the obtained base film satisfies the above properties. Examples include polycarbonate resin, cyclic olefin resin, cellulose resin, polyester resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, acrylic-based resins, and polyester carbonate resins. Among these, polycarbonate resins and polyester carbonate resins can be preferably used. According to the embodiment of the present invention, by providing the easy-adhesion layer to the polycarbonate-based resin film, it is possible to remarkably improve the adhesion between the film and the polarizer or polarizing plate. In this specification, polycarbonate resins and polyester carbonate resins may be collectively referred to as polycarbonate resins.

Any appropriate polycarbonate resin can be used as the polycarbonate resin as long as the effects of the present invention can be obtained. Preferably, the polycarbonate resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, an alicyclic diol, an alicyclic dimethanol, di-, tri- or polyethylene glycol, and an alkylene and a structural unit derived from at least one dihydroxy compound selected from the group consisting of glycols or spiroglycols. Preferably, the polycarbonate resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from an alicyclic dimethanol and/or derived from di-, tri- or polyethylene glycol. more preferably, a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from di-, tri- or polyethylene glycol. The polycarbonate resin may contain structural units derived from other dihydroxy compounds as necessary. Incidentally, the details of the polycarbonate resin, for example, JP-A-2014-10291, JP-A-2014-26266, JP-A-2015-212816, JP-A-2015-212817, JP-A-2015-212818 and the descriptions of these publications are incorporated herein by reference.

（上記一般式（１）中、Ｒ_１～Ｒ_４はそれぞれ独立に、水素原子、置換若しくは無置換の炭素数１～炭素数２０のアルキル基、置換若しくは無置換の炭素数６～炭素数２０のシクロアルキル基、または、置換若しくは無置換の炭素数６～炭素数２０のアリール基を表し、Ｘは置換若しくは無置換の炭素数２～炭素数１０のアルキレン基、置換若しくは無置換の炭素数６～炭素数２０のシクロアルキレン基、または、置換若しくは無置換の炭素数６～炭素数２０のアリーレン基を表し、ｍ及びｎはそれぞれ独立に０～５の整数である。） In one embodiment, a polycarbonate-based resin containing a unit structure derived from a dihydroxy compound represented by the following general formula (1) can be used.

(In the above general formula (1), R ₁ to R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, X is a substituted or unsubstituted alkylene group having 2 to 10 carbon atoms, a substituted or unsubstituted carbon number represents a cycloalkylene group having 6 to 20 carbon atoms, or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, and m and n are each independently an integer of 0 to 5.)

Specific examples of the dihydroxy compound represented by the general formula (1) include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9 - bis(4-hydroxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3- tert-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-( 2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl ) fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9 ,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4 -(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis (4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene and the like.

In addition to the structural unit derived from the dihydroxy compound, the polycarbonate-based resin includes isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), and bisphenols. may contain a structural unit derived from a dihydroxy compound such as

Details of polycarbonate resins containing structural units derived from dihydroxy compounds are described in, for example, Japanese Patent No. 5204200, Japanese Patent Application Laid-Open No. 2012-67300, Japanese Patent No. 3325560, WO2014/061677, and the like. The description of the patent document is incorporated herein by reference.

（上記一般式（２）および上記一般式（３）中、Ｒ_５およびＲ_６はそれぞれ独立に、直接結合、置換若しくは無置換の炭素数１～４のアルキレン基（好ましくは、主鎖上の炭素数が２～３であるアルキレン基）である。Ｒ_７は、直接結合、置換若しくは無置換の炭素数１～４のアルキレン基（好ましくは、主鎖上の炭素数が１～２であるアルキレン基）である。Ｒ_８～Ｒ_１３はそれぞれ独立に、水素原子、置換若しくは無置換の炭素数１～１０（好ましくは１～４、より好ましくは１～２）のアルキル基、置換若しくは無置換の炭素数４～１０（好ましくは４～８、より好ましくは４～７）のアリール基、置換若しくは無置換の炭素数１～１０（好ましくは１～４、より好ましくは１～２）のアシル基、置換若しくは無置換の炭素数１～１０（好ましくは１～４、より好ましくは１～２）のアルコキシ基、置換若しくは無置換の炭素数１～１０（好ましくは１～４、より好ましくは１～２）のアリールオキシ基、置換若しくは無置換の炭素数１～１０（好ましくは１～４、より好ましくは１～２）のアシルオキシ基、置換若しくは無置換のアミノ基、置換若しくは無置換の炭素数１～１０（好ましくは１～４）のビニル基、置換若しくは無置換の炭素数１～１０（好ましくは１～４）のエチニル基、置換基を有する硫黄原子、置換基を有するケイ素原子、ハロゲン原子、ニトロ基、またはシアノ基である。Ｒ_８～Ｒ_１３のうち隣接する少なくとも２つの基が互いに結合して環を形成していてもよい。） In one embodiment, polycarbonate-based resins containing oligofluorene structural units may be used. Polycarbonate resins containing oligofluorene structural units include, for example, resins containing structural units represented by the following general formula (2) and/or structural units represented by the following general formula (3).

(In general formulas (2) and (3) above, R ₅ and R ₆ are each independently a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms (preferably, an alkylene group having 2 to 3 carbon atoms), and R ₇ is a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms (preferably an alkylene group having 1 to 2 carbon atoms on the main chain). Each of R ₈ to R ₁₃ is independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms (preferably 1 to 4, more preferably 1 to 2), a substituted or unsubstituted A substituted or unsubstituted aryl group having 4 to 10 carbon atoms (preferably 4 to 8, more preferably 4 to 7) having 4 to 10 carbon atoms (preferably 1 to 4, more preferably 1 to 2) having 1 to 10 carbon atoms acyl group, substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms (preferably 1 to 4, more preferably 1 to 2), substituted or unsubstituted 1 to 10 carbon atoms (preferably 1 to 4, more preferably is 1 to 2) aryloxy group, substituted or unsubstituted acyloxy group having 1 to 10 carbon atoms (preferably 1 to 4, more preferably 1 to 2), substituted or unsubstituted amino group, substituted or unsubstituted A vinyl group having 1 to 10 carbon atoms (preferably 1 to 4), a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms (preferably 1 to 4), a sulfur atom having a substituent, a silicon having a substituent an atom, a halogen atom, a nitro group, or a cyano group, and at least two adjacent groups among R ₈ to R ₁₃ may bond together to form a ring.)

In one embodiment, the fluorene ring contained in the oligofluorene structural unit has a structure in which all of R ₈ to R ₁₃ are hydrogen atoms, or R ₈ and/or R ₁₃ are halogen atoms or acyl groups. , a nitro group, a cyano group, and a sulfo group, and R ₉ to R ₁₂ are hydrogen atoms.

Details of polycarbonate-based resins containing oligofluorene structural units are described, for example, in JP-A-2015-212816. The description of the publication is incorporated herein by reference.

A-3. Easy-Adhesion Layer The easy-adhesion layer is typically a solidified layer of a water-based resin coating film. A preferred specific example of the water-based resin is a urethane-based resin. Therefore, the easy-adhesion layer may preferably be a solidified layer of a coating film of an aqueous dispersion containing a urethane-based resin (coating liquid for forming an easy-adhesion layer). Water-based systems are more environmentally friendly than solvent-based systems, and can be easier to work with.

A urethane-based resin is typically obtained by reacting a polyol and a polyisocyanate. The polyol is not particularly limited as long as it has two or more hydroxyl groups in the molecule, and any suitable polyol can be adopted. Specific examples include polyacryl polyols, polyester polyols, and polyether polyols. These may be used alone or in combination of two or more.

Examples of polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. , 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate and other aliphatic diisocyanates; isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4′-cyclohexylmethane diisocyanate, 1,4- Alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane; tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′- Aromas such as diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate group diisocyanates; araliphatic diisocyanates such as dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α,α,α,α-tetramethylxylylene diisocyanate, and the like. These may be used alone or in combination of two or more.

The urethane-based resin preferably has a carboxyl group. By having a carboxyl group, it is possible to obtain a retardation film with an easily adhesive layer that is excellent in adhesion to a polarizer (especially at high temperature and high humidity). A urethane-based resin having a carboxyl group can be obtained, for example, by reacting a chain lengthening agent having a free carboxyl group in addition to the above polyol and the above polyisocyanate. Chain lengthening agents having a free carboxyl group include, for example, dihydroxycarboxylic acid and dihydroxysuccinic acid. Dihydroxycarboxylic acids include, for example, dialkylolalkanoic acids such as dimethylolalkanoic acid (eg, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolpentanoic acid). These may be used alone or in combination of two or more.

The number average molecular weight of the urethane resin is preferably 5,000 to 600,000, more preferably 10,000 to 400,000. The acid value of the urethane-based resin is preferably 10 or more, more preferably 10-50, and particularly preferably 20-45. If the acid value is within such a range, the adhesion to the polarizer can be more excellent.

The easy-adhesive layer-forming coating liquid preferably contains a cross-linking agent. Any appropriate cross-linking agent can be employed as the cross-linking agent. Specifically, when the urethane-based resin has a carboxyl group, the cross-linking agent preferably includes a polymer having a group capable of reacting with the carboxyl group. Examples of groups capable of reacting with carboxyl groups include organic amino groups, oxazoline groups, epoxy groups, and carbodiimide groups. Preferably, the crosslinker has an oxazoline group. A cross-linking agent having an oxazoline group has a long pot life at room temperature when mixed with a urethane-based resin, and the cross-linking reaction proceeds by heating, resulting in good workability.

The easy-adhesive layer-forming coating liquid preferably does not contain fine particles. With such a configuration, the easy-adhesion layer having the desired thickness variation can be formed, and as a result, the easy-adhesion layer-attached retardation film with small retardation unevenness can be realized. The easy-adhesive layer-forming coating liquid may contain a leveling agent, if necessary. By including leveling, the smoothness of the coating film can be further improved, and as a result, an easy-adhesion layer with small thickness variations (typically, having the desired thickness variations described above) can be formed. Leveling agents include, for example, isopropyl alcohol (IPA), ethylene glycol, and propylene glycol. The content of the leveling agent in the easy-adhesive layer-forming coating liquid may be, for example, 1.0% by weight to 3.5% by weight.

The easy-adhesive layer-forming coating liquid may further contain any appropriate additive. Additives include, for example, antiblocking agents, dispersion stabilizers, thixotropic agents, antioxidants, ultraviolet absorbers, antifoaming agents, thickeners, dispersants, surfactants, catalysts, fillers, lubricants, antistatic agents, agents. The type, number, combination, blending amount, etc. of additives can be appropriately set according to the purpose.

Details of the urethane-based resin and the coating liquid for forming an easy-adhesive layer are described, for example, in JP-A-2010-055062. The description of the publication is incorporated herein by reference.

The average thickness of the easy-adhesion layer can be set according to the average thickness of the base film so that the desired ratio T ₁ /T ₂ is obtained. The average thickness of the easy adhesion layer is preferably 150 nm to 600 nm, more preferably 200 nm to 500 nm, still more preferably 250 nm to 400 nm. With such a configuration, breakage during production of the retardation film with an easily adhesive layer can be suppressed.

B. Method for producing retardation film with easy-adhesion layer The method for producing the retardation film with an easy-adhesion layer according to the above item A includes forming a coating film by applying a coating liquid for forming an easy-adhesion layer to a resin film; drying the coated film; and stretching the laminate of the resin film and the dried coated film.

Constituent materials of the resin film are as described in section A-2 above regarding the base film. The thickness of the resin film before stretching can be appropriately set according to the thickness of the obtained retardation film (base film), the in-plane retardation, and the like. The thickness of the resin film before stretching may be, for example, 40 μm to 150 μm.

Any appropriate method can be adopted as a method for applying the coating liquid for forming an easy-adhesion layer. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating, etc.).

The solid content concentration of the easily adhesive layer-forming coating liquid is typically 0.5 wt % to 3.0 wt %, preferably 0.5 wt % to 1.5 wt %, more preferably 0.7 wt % to 1.2 wt %, more preferably 0.8 wt % to 1.1 wt %. If the solid content concentration is within such a range, the easy-adhesion layer having the desired thickness variation can be formed, and as a result, an easy-adhesion layer-attached retardation film with small retardation unevenness can be realized. . If the solid content concentration is too low, an easy-adhesion layer may not be formed. If the solid content concentration is too high, the thickness variation may become too large.

The thickness of the coating film can be adjusted so that the easy-adhesion layer to be obtained has the desired average thickness (resulting in the ratio T ₁ /T ₂ ).

The coating film is then dried. The drying temperature can be, for example, 80°C to 95°C. The drying time can be, for example, 1 minute to 3 minutes. Thus, a dry coating film is formed on the resin film.

Next, the laminate of the resin film and the dry coating film obtained above is stretched. By stretching the coating film after drying, a retardation film with an easy-adhesion layer having excellent adhesion between the easy-adhesion layer and the substrate film can be obtained.

In one embodiment, the stretching process is uniaxial stretching (eg, fixed-end uniaxial stretching, free-end uniaxial stretching). A specific example of the fixed-end uniaxial stretching is a method of stretching the laminate in the width direction (horizontal direction) while running the laminate in the longitudinal direction. In this case, the slow axis of the obtained substrate film is expressed in the width direction. Free-end uniaxial stretching includes a method in which the laminate is conveyed between rolls with different peripheral speeds and stretched in the longitudinal direction. In this case, the slow axis of the substrate film to be obtained is expressed in the longitudinal direction. The draw ratio can be appropriately set according to the desired in-plane retardation of the base film. The draw ratio is preferably 1.1 times to 3.5 times.

In another embodiment, the stretching process is diagonal stretching. Specifically, a long laminate is continuously obliquely stretched in a direction at an angle θ with respect to the longitudinal direction. By adopting oblique stretching, a long base film having an orientation angle of angle θ with respect to the longitudinal direction of the film (slow axis in the direction of angle θ) can be obtained. Roll-to-roll is possible during lamination, and the manufacturing process can be simplified. A stretching machine used for diagonal stretching includes, for example, a tenter-type stretching machine capable of applying a feeding force, a pulling force, or a taking-up force at different speeds in the horizontal and/or vertical direction. The tenter-type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, but any suitable stretching machine can be used as long as it can continuously obliquely stretch a long laminate.

The stretching temperature is typically a temperature equal to or higher than the glass transition temperature (Tg) of the resin film. The stretching temperature is preferably (Tg+1)°C to (Tg+10)°C, more preferably (Tg+1)°C to (Tg+5)°C.

As described above, a retardation film with an easily adhesive layer can be produced.

C. Retardation layer-attached polarizing plate The easy-adhesion layer-attached retardation film described in the above items A and B can be applied to an optical member such as a retardation layer-attached polarizing plate. Therefore, an embodiment of the present invention includes a retardation layer-attached polarizing plate having the easily adhesive layer-attached retardation film. A retardation layer-attached polarizing plate according to an embodiment of the present invention includes a polarizing plate and an easy-adhesion layer-attached retardation film bonded to the polarizing plate via an adhesive layer and an easy-adhesion layer. The base film of the retardation film with an easy-adhesion layer functions as a retardation layer. A polarizing plate typically has a polarizer and a protective layer disposed on at least one side of the polarizer. The polarizer is typically an absorptive polarizer. The angle between the slow axis of the base film and the absorption axis of the polarizer can be appropriately set according to the application and purpose. The angle is preferably 30° to 60°, more preferably 40° to 50°, even more preferably 42° to 48°, particularly preferably about 45°.

The adhesive layer is typically composed of an active energy ray-curable adhesive. When the adhesive layer is an active energy ray-curable adhesive, the effect of the easy-adhesion layer is remarkable. Any appropriate adhesive can be used as the active energy ray-curable adhesive as long as it is an adhesive that can be cured by irradiation with an active energy ray. Examples of active energy ray-curable adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Specific examples of the curing type of the active energy ray-curable adhesive include radical curing, cationic curing, anionic curing, and combinations thereof (for example, hybrids of radical curing and cationic curing). Active energy ray-curable adhesives include, for example, adhesives containing compounds (eg, monomers and/or oligomers) having radically polymerizable groups such as (meth)acrylate groups and (meth)acrylamide groups as curing components. mentioned. Specific examples of the active energy ray-curable adhesive and its curing method are described, for example, in JP-A-2012-144690. The description of the publication is incorporated herein by reference.

Any appropriate polarizer can be adopted as the polarizer. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene/vinyl acetate copolymer films. In addition, polyene-based oriented films such as those subjected to dyeing treatment and stretching treatment with dichroic substances such as iodine and dichroic dyes, and dehydrated PVA and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used because of its excellent optical properties.

The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial drawing is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or may be performed while dyeing. Moreover, you may dye after extending|stretching. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only can dirt and anti-blocking agents on the surface of the PVA-based film be washed away, but also the PVA-based film can be swollen to remove uneven dyeing. can be prevented.

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. Details of the method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. These publications are incorporated herein by reference in their entirety.

The thickness of the polarizer is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the polarizer is preferably 1 μm to 25 μm, more preferably 3 μm to 10 μm, particularly preferably 3 μm to 8 μm. If the thickness of the polarizer is within such a range, it is possible to satisfactorily suppress curling during heating, and obtain excellent durability in appearance during heating.

The protective layer is formed of any appropriate protective film that can be used as a film that protects the polarizer. Specific examples of materials that are the main component of the protective film include cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, and polysulfones. transparent resins such as polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Thermosetting resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone, or ultraviolet curable resins may also be used. In addition, for example, a glassy polymer such as a siloxane-based polymer can also be used. Further, polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. Materials for this film include, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in a side chain. can be used, for example, a resin composition comprising an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile/styrene copolymer. The polymer film can be, for example, an extrudate of the resin composition.

The thickness of the protective layer is preferably 10 μm to 100 μm. The protective layer may be laminated on the polarizer via an adhesive layer (specifically, an adhesive layer, a pressure-sensitive adhesive layer), or may be laminated on the polarizer in close contact (without an adhesive layer). good. If necessary, a surface treatment layer such as a hard coat layer, an antiglare layer and an antireflection layer may be formed on the protective layer arranged on the outermost surface of the retardation layer-attached polarizing plate.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. The measurement method and evaluation method for each characteristic are as follows.
(1) Average Thickness and Thickness Variation Measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name: "MCPD-3000"). The average thickness and thickness variation were determined as follows: The easily adhesive layer-attached retardation films obtained in Examples, Comparative Examples, and Reference Examples were cut into 1 m×1 m sizes to obtain measurement samples. The thickness was measured at intervals of 50 mm along each of the direction of a pair of opposing sides of the measurement sample and the direction orthogonal to the direction, and the average was taken as the average thickness. Furthermore, the maximum thickness and the minimum thickness in the measurement were obtained as a ratio to the average thickness, and the range from the minimum thickness to the maximum thickness was defined as the thickness variation.
(2) In-plane retardation Measured using "Axoscan" manufactured by Axometrics. The measurement wavelength was 550 nm and the measurement temperature was 23°C.
(3) Breaking In the production of the retardation films with easily adhesive layers of Examples, Comparative Examples and Reference Examples, the state of the film being fed out from the tenter stretching machine was checked and evaluated according to the following criteria.
○: The film was discharged smoothly, and no cracks or the like occurred in the film △: The film was discharged, but cracks occurred in the film ×: The film was broken and not discharged (4) Retardation Unevenness The retardation films with an easy-adhesion layer obtained in Examples, Comparative Examples, and Reference Examples are laminated to a commercially available polarizing plate via a UV-curable adhesive and an easy-adhesion layer to produce a polarizing plate with a retardation layer. did. This retardation layer-attached polarizing plate was attached to a reflector via an adhesive to obtain a test sample. The state of the test sample was visually confirmed and evaluated according to the following criteria.
○: uniform and no shading was observed △: slight shading was observed, but it was practically no problem ×: shading was remarkable

[Example 1]
1. Preparation of Polycarbonate Resin Film Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 100°C. Bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane (compound 3) 29.60 parts by mass (0.046 mol), ISB 29.21 parts by mass (0.200 mol), SPG 42.28 mass (0.139 mol), 63.77 parts by mass (0.298 mol) of DPC, and 1.19×10 ⁻² parts by mass (6.78×10 ⁻⁵ mol) of calcium acetate monohydrate as a catalyst were charged. After the interior of the reactor was replaced with nitrogen under reduced pressure, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. After 40 minutes from the start of heating, the internal temperature was allowed to reach 220°C, and the pressure was reduced at the same time as controlling to maintain this temperature. Phenol vapor produced as a by-product of the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C and recovered. After nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was brought to 240° C. and the pressure to 0.2 kPa in 50 minutes. After that, polymerization was allowed to proceed until a predetermined stirring power was obtained. When a predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, the polyester carbonate produced was extruded into water, and strands were cut to obtain pellets.
After vacuum drying the obtained polycarbonate resin at 80 ° C. for 5 hours, a single screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), a T die (width 300 mm, set temperature: 250 ° C.), a chill roll ( A polycarbonate-based resin film having a thickness of 100 μm was produced using a film forming apparatus equipped with a set temperature of 120 to 130° C. and a winder.

2. Formation of coating film Polyester urethane (manufactured by Daiichi Kogyo Seiyaku, trade name: Superflex 210, solid content: 33%) 16.8 g, cross-linking agent (oxazoline-containing polymer, manufactured by Nippon Shokubai, trade name: Epocross WS-700, solid Min: 25%) and 2.0 g of 1% by weight ammonia water are mixed, and pure water and isopropyl alcohol (IPA, leveling agent) are added to make the solid content concentration 1% by weight and the IPA concentration to 2%. 0.5% by weight to prepare a coating solution for forming an easy-adhesion layer.

3. Production of Retardation Film with Easily Adhesive Layer 2 above. The coating solution for forming an easy-adhesion layer obtained in 1. above. was applied to the polycarbonate resin film obtained in 1. above using a bar coater (#6). Then, it was dried at 140° C. for about 5 minutes to obtain a laminate of the polycarbonate-based resin film and the dried coating film. This laminate was fixed-end uniaxially stretched by a tenter stretching machine to obtain a retardation film with an easily adhesive layer. The preheating temperature in stretching was 145°C, and the stretching temperature was 143°C (Tg + 3°C). The draw ratio was 2.8 times. In the obtained retardation film with an easy-adhesion layer, the thickness of the base film is 40 μm, the Re (550) of the base film is 140 nm, the thickness of the easy-adhesion layer is 348 nm, and the ratio T ₁ /T ₂ was 0.0087, and the thickness variation was 0.89 to 1.10. The easily adhesive layer-attached retardation film thus obtained was subjected to the above evaluations (3) and (4). Table 1 shows the results.

[Example 2]
A retardation film with an easy-adhesion layer was produced in the same manner as in Example 1, except that the thickness of the coating film was changed to form an easy-adhesion layer having a thickness of 297 nm. The ratio T ₁ /T ₂ was 0.0074 and the thickness variation was 0.81 to 1.20. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Example 3]
A retardation film with an easy-adhesion layer was produced in the same manner as in Example 1, except that the thickness of the coating film was changed to form an easy-adhesion layer having a thickness of 281 nm. The ratio T ₁ /T ₂ was 0.0070, and the thickness variation was 0.93-1.10. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Example 4]
A retardation film with an easy-adhesion layer was produced in the same manner as in Example 1, except that the thickness of the coating film was changed to form an easy-adhesion layer having a thickness of 175 nm. The ratio T ₁ /T ₂ was 0.0044 and the thickness variation was 0.86-1.08. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Example 5]
The thickness of the resin film and the stretching ratio were changed to set the thickness of the base film to 30 μm (in-plane retardation Re (550) = 130 nm), and the thickness of the coating film was changed to create an easy-adhesion layer with a thickness of 306 nm. A retardation film with an easily adhesive layer was produced in the same manner as in Example 1 except that the was formed. The ratio T ₁ /T ₂ was 0.0102, and the thickness variation was 0.85-1.14. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Example 6]
The thickness of the resin film and the stretching ratio were changed to set the thickness of the base film to 25 μm (in-plane retardation Re (550) = 120 nm), to set the stretching temperature to Tg + 1 ° C., and to increase the thickness of the coating film. A retardation film with an easy-adhesion layer was produced in the same manner as in Example 1, except that an easy-adhesion layer having a thickness of 251 nm was formed. The ratio T ₁ /T ₂ was 0.0100, and the thickness variation was 0.80 to 1.03. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Comparative Example 1]
A retardation film with an easy-adhesion layer was produced in the same manner as in Example 1, except that the thickness of the coating film was changed to form an easy-adhesion layer having a thickness of 608 nm. The ratio T ₁ /T ₂ was 0.0152, and the thickness variation was 0.91 to 1.10. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Comparative Example 2]
An easy-adhesion layer was formed in the same manner as in Example 1, except that the solid content concentration of the easy-adhesion layer-forming coating liquid was changed to 8% by weight, and the thickness of the coating film was changed to form an easy-adhesion layer with a thickness of 357 nm. A retardation film with an adhesive layer was produced. The ratio T ₁ /T ₂ was 0.0089, and the thickness variation was 0.80 to 1.24. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Comparative Example 3]
Colloidal silica (Quartron PL-3 manufactured by Fuso Chemical Industry Co., Ltd., solid content: 20% by weight) was added to the coating liquid for forming an easy-adhesion layer used in Example 1 to form an easy-adhesion layer with a silica particle concentration of 0.6% by weight. was prepared. A retardation film with an easy-adhesion layer was obtained in the same manner as in Example 1 except that this easy-adhesion layer-forming coating liquid was used and the thickness of the coating film was changed to form an easy-adhesion layer having a thickness of 387 nm. made. The ratio T ₁ /T ₂ was 0.0097, and the thickness variation was 0.76 to 1.28. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

[Reference example 1]
Using a commercially available cycloolefin resin film instead of a polycarbonate resin film, changing the solid content concentration of the easy adhesion layer forming coating liquid to 10% by weight, setting the stretching temperature to Tg + 5 ° C., and A retardation film with an easy-adhesion layer was produced in the same manner as in Example 1, except that the thickness of the coating film was changed to form an easy-adhesion layer having a thickness of 332 nm. The ratio T ₁ /T ₂ was 0.0083, and the thickness variation was 0.90 to 1.43. The same evaluation as in Example 1 was performed on the obtained retardation film with an easily adhesive layer. Table 1 shows the results.

As is clear from Table 1, the easy-adhesion layer-attached retardation films according to the examples of the present invention are less likely to break during production and have less unevenness in retardation.

The easily adhesive layer-attached retardation film according to the embodiment of the present invention is suitably used for optical members such as a retardation layer-attached polarizing plate, and such an optical member is suitably used for an image display device.

DESCRIPTION OF SYMBOLS 10 Retardation film with easy-adhesion layer 11 Base film 12 Easy-adhesion layer

Claims (10)

a base film having an in-plane retardation; and an easy-adhesion layer provided on at least one surface of the base film;
The ratio T ₁ /T ₂ of the average thickness T ₁ of the easy adhesion layer to the average thickness T ₂ of the base film is 0.011 or less,
The easy-adhesion layer has a maximum thickness of 1.20 or less and a minimum thickness of 0.80 or more relative to the average thickness _T1 of the easy-adhesion layer.
Retardation film with easy adhesion layer. The easily adhesive layer-attached retardation film according to claim 1, wherein the base film is a stretched polycarbonate-based resin film. 3. The easily adhesive layer-attached retardation film according to claim 2, wherein the substrate film is elongated and is an obliquely stretched polycarbonate-based resin film. The easily adhesive layer-attached retardation film according to claim 3, wherein the base film has a slow axis in a direction of 30° to 60° with respect to the longitudinal direction. 5. The easily adhesive layer-attached retardation film according to claim 1, wherein the substrate film has an in-plane retardation Re (550) of 100 nm to 190 nm. The retardation film with an easily adhesive layer according to any one of claims 1 to 5, wherein the easily adhesive layer is a solidified layer of a coating film of a water-based resin. The retardation film with an easily adhesive layer according to claim 6, wherein the water-based resin is a urethane-based resin. A polarizing plate, and the retardation film with an easy-adhesion layer according to any one of claims 1 to 7, which is attached to the polarizing plate via an adhesive layer and the easy-adhesion layer,
The base film functions as a retardation layer,
A polarizing plate with a retardation layer. 9. The retardation layer-attached polarizing plate according to claim 8, wherein the adhesive layer comprises an active energy ray-curable adhesive. A method for producing a retardation film with an easy-adhesion layer according to any one of claims 1 to 7,
Forming a coating film by applying a coating liquid for forming an easy-adhesion layer to a resin film; drying the coating film; and stretching a laminate of the resin film and the dry coating film; The solid content concentration of the adhesive layer-forming coating liquid is 0.5% by weight to 3.0% by weight.
Method.

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