TW201610488A - Retardation film and polarizing plate comprising the same - Google Patents

Abstract

The present invention provides a retardation film with full width phase difference of 5nm or less and dispersion of the full width phase difference of 1.5nm or less. The retardation film of the present invention can suppress unevenness defects produced in the manufacturing process in order to improve visual confirmation of a display panel.

Description

Phase difference film and polarizing plate containing the same

The present invention relates to a retardation film and a polarizing plate comprising the same, and more particularly to a retardation film which can suppress unevenness occurring in a manufacturing step and a polarizing plate including the same.

The retardation film is used for a variety of purposes. Specifically, the liquid crystal display device is used to eliminate the coloration of an image or to enlarge the viewing angle, and is used in an organic light-emitting device for anti-reflection or correction of the hue of the polarizing plate. Further, in the touch panel, it is used to improve visibility by reducing external light reflection.

However, the retardation film described above has a problem that unevenness in the streaks due to an error in manufacturing steps or a manufacturing failure or the like is a problem in the visibility of the evaluation panel.

However, hitherto, there has been no known method for effectively suppressing the unevenness of the generation of the retardation film.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent No. 10-312166

The present invention has been made in order to solve the above problems, and an object thereof is to provide a retardation film which can suppress unevenness occurring in a manufacturing step.

Another object of the present invention is to provide a polarizing plate in which the retardation film is laminated on a polarizing element.

Still another object of the present invention is to provide an image display device comprising the above polarizing plate.

In one aspect, the present invention provides a retardation film having a full-width phase difference of 5 nm or less and a dispersion of a full-width phase difference of 1.5 nm or less.

In one embodiment of the present invention, the phase difference film portion has a phase difference of 1 nm or less.

In one embodiment of the present invention, the retardation film is a λ/4 retardation film.

On the other hand, the present invention provides a polarizing plate in which a phase difference film is laminated on a polarizing element.

Moreover, in another aspect, the present invention provides an image display device comprising the above polarizing plate.

The retardation film of the present invention can suppress unevenness occurring in the production step and improve the visibility of the display panel.

100‧‧‧Polar plate

110‧‧‧Protective film

120‧‧‧Polarized elements

125‧‧‧Adhesive layer

130‧‧‧ phase difference film

135‧‧‧Adhesive layer

200‧‧‧Polar plate

210‧‧‧Protective film

220‧‧‧Polarized components

225‧‧‧Adhesive layer

230‧‧‧ phase difference film

Fig. 1 is a cross-sectional view schematically showing a polarizing plate according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view schematically showing a polarizing plate according to another embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

An embodiment of the present invention relates to a retardation film having a full-width phase difference of 5 nm or less and a dispersion of a full-width phase difference of 1.5 nm or less.

In one embodiment of the present invention, the full-width phase difference may be 2 nm or less, and the dispersion of the full-width phase difference may be 1 nm or less.

The retardation film according to an embodiment of the present invention is characterized in that the partial phase difference is dispersed to be 1 nm or less.

In the present invention, the full-width phase difference means an in-plane phase difference obtained by measuring the full width of the retardation film, and the partial phase difference means that the left side portion, the center portion or the right side portion is 15 mm on the basis of the full width. The in-plane phase difference measured at five locations at intervals of 3 mm was measured in the local portion.

The in-plane phase difference Re is a value defined by the following formula 1.

[Expression 1] Re = (n _{x -} n _y ) × d In the above formula, n _x represents a refractive index in the direction of the axis (late phase axis) showing the maximum refractive index in the plane of the film, and n _y represents the above-mentioned retardation The refractive index in the direction in which the phase axes are orthogonal, and d represents the thickness (nm) of the film.

In the present invention, the method of measuring the in-plane phase difference of the retardation film is not particularly limited, and can be measured, for example, by a method proposed in an experimental example to be described later.

In one embodiment of the present invention, the full-width phase difference of the retardation film is adjusted to 5 nm or less, and the dispersion of the full-width phase difference is adjusted to 1.5 nm or less. Preferably, the full-width phase difference is adjusted to 2 nm or less, and the full-width phase difference is obtained. The dispersion is adjusted to 1 nm or less, whereby unevenness occurring in the manufacturing step can be suppressed.

In another embodiment of the present invention, the full-width phase difference of the retardation film is adjusted to 5 nm or less, the dispersion of the full-width phase difference is adjusted to 1.5 nm or less, and the dispersion of the partial phase difference is adjusted to 1 nm or less. The unevenness that occurs in the manufacturing step can be suppressed.

The retardation film according to an embodiment of the present invention may be a λ/4 retardation film.

The above-mentioned λ/4 retardation film refers to a film that functions as a pair of polarizing elements. Further, the polarized light is polarized to give a phase difference of about 1/4 wavelength, and the linearly polarized light is converted into circularly polarized light.

The material which can form the retardation film according to an embodiment of the present invention is not particularly limited as long as it exhibits the above characteristics, and any preferable material can be selected. For example, the retardation film can be produced by applying a coating layer containing a photo-alignment polymer and a reactive liquid crystal compound to a transparent substrate to form a composition and harden it.

The photo-alignment polymer may, for example, be a polymer having a photosensitive structure. When a polymer having a photosensitive structure is irradiated with light, the photosensitive structure of the irradiated portion is isomerized or crosslinked, whereby the photoalignment polymer is aligned, and the force for aligning the liquid crystal component in a fixed direction is exhibited (alignment) Limiting power).

Examples of the photosensitive structure include a photosensitive structure which is isomerized by light irradiation, such as an azobenzene structure, a spiropyran structure, a spirobenzopyran structure, or a fulgide structure; A photosensitive structure in which an enediamine structure, a chalcone type structure, a cinnamic acid type structure, a 1,2-vinyl structure, a 1,2-acetylene structure, and the like are crosslinked by light irradiation.

Examples of the photo-alignment polymer include a photosensitive structure and one or more radical polymerizable groups (preferably, a vinyl group, an acrylonitrile group, or a methacryl group). a polymer obtained by radical polymerization of a monomer; a polymer obtained by polymerizing a photosensitive structure, a monomer having two or more amine groups, and a dicarboxylic acid compound; A polymer obtained by polymerizing a monomer having two or more carboxyl groups and a diamine compound; obtained by subjecting a monomer having a photosensitive structure to an anionic polymerization, a cationic polymerization or the like, a chain polymerization, a coordination polymerization, or a ring-opening polymerization. The polymer. Among these, a polymer obtained by radical polymerization of a photosensitive structure and a monomer having one or more radical polymerizable groups is preferred.

In the case where the photo-alignment polymer is obtained by radical polymerization of a photosensitive structure and a monomer having one radical polymerizable group, it is preferred to be photosensitive in the monomer. The structure and the radical polymerizable group are bonded via an alkyl group. The carbon number of the alkylene group is preferably in the range of 3 to 20, more preferably in the range of 5 to 10. Further, the photosensitive structure and the radical polymerizable group may be bonded via an ester bond (-CO-O- or -O-CO-) or an ether bond (-O-).

The photo-alignment polymer may be a copolymer obtained by polymerizing two or more kinds of monomers having different photosensitive structures. Further, the photo-alignment polymer may be a constituent component (structural unit) derived from a monomer having no photosensitive structure. In this case, the content of the constituent component (structural unit) derived from the monomer having a photosensitive structure in 100 mol% of all the constituent components (structural units) of the photo-alignment polymer is preferably 50 to 95 mol%, more preferably It is preferably in the range of 60 to 90 mol%, more preferably 70 to 80 mol%.

A commercially available product can also be used as the photo-alignment polymer, and a specific example thereof is LR9000 commercially available from BASF Corporation. These photo-alignment polymers may be used singly or in combination of plural.

The number average molecular weight of the above photo-alignment polymer is preferably from 20,000 to 100,000, more preferably from 25,000 to 80,000, still more preferably from 30,000 to 50,000. When the number average molecular weight is within the above range, the alignment of the liquid crystal component becomes better when the liquid crystal composition is aligned.

The reactive liquid crystal compound is a compound having liquid crystallinity and has one or more polymerizable groups in the molecule. The polymerizable group means a group which participates in the polymerization reaction of the reactive liquid crystal compound. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-cyclovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloxy group, a methacryloxy group, and an oxiran group. And oxetanyl.

The polymerizable liquid crystal compound preferably has two or more ring structures in its molecule, and more preferably has three or more ring structures. Examples of the ring structure include a benzene ring, a cyclohexane ring, a naphthalene ring, a pyrimidine ring, a pyridine ring, and a thiophene ring. Among them, a benzene ring and a cyclohexane ring are preferred. . Examples of the linking group which bonds two or more ring structures include -CO-O-, -CH ₂ -CH ₂ -, -CO-S-, -CO-NH-, -CH=CH-, -N. =N-, and -C≡C-, and among these, -CO-O- is preferred.

A commercially available product can be used as the reactive liquid crystal compound, and a specific example thereof is PALIO COLOR (registered trademark) LC242 commercially available from BASF Corporation. These reactive liquid crystal compounds may be used singly or in combination of plural kinds.

The above coating layer forming composition may contain a polymerization initiator. The polymerization initiator is preferably a photopolymerization initiator, and a photopolymerization initiator is preferably used in the polymerization of the polymerizable liquid crystal compound at a low temperature.

Examples of the photopolymerization initiator include a benzoin compound, a benzophenone compound, a phenylalkyl ketone compound, a fluorenyl phosphine oxide compound, and the like. Compounds, phosphonium salts, and phosphonium salts. As a photopolymerization initiator, a commercially available product can also be used. Specifically, Irgacure (registered trademark) 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all of which are manufactured by BASF Japan), Seikuol (registered trademark) BZ, Seikuol Z, and Seikuol BEE (above, Manufactured by Seiko Chemical Co., Ltd., kayacure (registered trademark) BP100 (manufactured by Nippon Kayaku Co., Ltd.), CYRACURE (registered trademark) UVI-6992 (manufactured by Dow Chemical Co., Ltd.), Adeka Optomer SP-152, Adeka Optomer SP -170 (all of them are manufactured by ADEKA (share)), TAZ-A, TAZ-PP (above, DKSH Japan), TAZ-104 (manufactured by Sanwa Chemical Co., Ltd.), and the like.

The coating layer forming composition preferably contains a solvent. The solvent is not particularly limited as long as it is a solvent which can dissolve the component contained in the coating layer forming composition and is inert to the polymerization reaction of the reactive liquid crystal compound, and specific examples thereof include methanol, ethanol, ethylene glycol, and isopropyl alcohol. Alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, propylene glycol monomethyl ether, phenol and other alcohol solvents; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol An ester solvent such as methyl ether acetate or ethyl lactate; a ketone solvent such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone or methyl isobutyl ketone; pentane, hexane, An aliphatic hydrocarbon solvent such as heptane; an aromatic hydrocarbon solvent such as toluene or xylene; a nitrile solvent such as acetonitrile; tetrahydrofuran, An ether solvent such as methoxyethane; a chlorine solvent such as chloroform or chlorobenzene. These solvents may be used singly or in combination of plural.

The method of forming the composition by coating the coating layer is not particularly limited, and specifically, spin coating, roll coating, dispensing coating, gravure coating, or the like can be used. It is preferred to determine the kind or amount of the solvent according to the coating method.

The solvent contained in the coating layer forming composition is evaporated by a drying step.

The drying is not particularly limited, and it may be carried out by a usual hot air dryer or a far infrared heater. The drying temperature is usually in the range of 30 to 120 ° C, preferably 50 to 100 ° C, and the drying time is usually 30 to 600 seconds. It is preferably in the range of 60 to 300 seconds. Further, the drying may be carried out under the same temperature conditions or may be carried out while gradually increasing the temperature.

After drying, the phase difference coating layer is formed by photocuring by irradiation with light such as ultraviolet rays or by thermal irradiation by heat irradiation or the like.

Examples of the photohardening include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, etc., and when it is considered in terms of economy or output of the metal, it is preferably utilized. High pressure mercury lamp or metal halide lamp.

Illumination may be 30 ~ 300mW / cm ^2, preferably 30 ~ 250mW / cm ^2, more preferably in a range of 30 ~ 200mW / cm ² of. If the illuminance less than 30mW / cm ^2, curing time becomes long, there is the case of poor productivity, if more than 300mW / cm ^2, there is the illumination due to higher thermal damage to the film is applied to the case of film deformation .

The film thickness of the phase difference coating layer is preferably in the range of 10 μm to 50 μm, more preferably in the range of 10 μm to 15 μm.

As the transparent substrate, a film excellent in transparency, mechanical strength, thermal stability, water repellency, isotropy, and the like can be used. As a specific example, a film containing a resin such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, or polybutylene terephthalate may be used. Resin; cellulose resin such as diacetyl cellulose or triacetonitrile cellulose; polycarbonate resin; acrylic resin such as poly(methyl) acrylate or poly(methyl) acrylate; polystyrene , styrene resin such as acrylonitrile-styrene copolymer; polyethylene, polypropylene, with ring system or drop Polyolefin resin such as polyolefin structure or ethylene-propylene copolymer; vinyl chloride resin; guanamine resin such as nylon or aromatic polyamine; quinone imine resin; polyether oxime resin; polyether ether A ketone resin; a polyphenylene sulfide resin; a vinyl alcohol resin; a vinylidene chloride resin; an ethylene butyral resin; an aryl ester resin; a polyoxymethylene resin; and a thermoplastic resin such as an epoxy resin. Further, a film containing a thermosetting resin such as a (meth)acrylic acid, an urethane-based compound, an urethane-based urethane-based compound, an epoxy-based or a polyoxyxene-based resin, or an ultraviolet-curable resin may be used.

An embodiment of the present invention relates to a polarizing plate in which a retardation film is laminated on a polarizing element.

The polarizing element is an optical film that functions to change the incident natural light into a desired single polarization state (linear polarization state), and is not particularly limited as long as it is generally capable of exhibiting a polarizing function in the field.

Specifically, a polarizing element obtained by dyeing an iodine or a heterochromatic dye to a PVA (polyvinyl alcohol) film and extending it in a fixed direction; or a fine pattern having a polarizing function on a transparent substrate can be used. A polarizing plate made of a thin plate coated with an insulating layer in a concave portion and a convex portion of the lattice.

Further, the polarizing plate may be provided with a protective film for protecting the polarizing element which is weak in mechanical direction on one side or both sides of the polarizing element. As the protective film, a film which is excellent in transparency, mechanical strength, thermal stability, water repellency, isotropy, and the like depending on the kind of the resin can be used.

In addition, the constitution or manufacturing method of the polarizing plate is generally required in the field. The user can be used without particular limitation.

In one embodiment of the present invention, the polarizing plate can laminate the absorption axis of the polarizing element and the optical axis of the retardation film within ±60°. It is preferable that the circularly polarized light can be stably realized when the above angle is within ±60°.

The optical axis refers to a slow axis or a fast axis, and unless otherwise specified, refers to a slow phase axis.

Referring to FIG. 1, a polarizing plate 100 according to an embodiment of the present invention includes: a polarizing element 120; a protective film 110 attached to one surface of the polarizing element 120; and a retardation film 130 interposed between the adhesive layer 125. The other surface of the polarizing element 120 is bonded to the surface of the polarizing element 120; and the adhesive layer 135 is bonded to the other surface of the retardation film 130.

The polarizing plate 100 according to an embodiment of the present invention may further include a protective film (not shown) between the polarizing element 120 and the adhesive layer 125.

Referring to FIG. 2, a polarizing plate 200 according to another embodiment of the present invention includes: a polarizing element 220; a protective film 210 attached to one surface of the polarizing element 220; and a retardation film 230 interposed between the adhesive layers. 225 is attached to the other side of the polarizing element 220.

The polarizing plate 200 according to an embodiment of the present invention may further include a protective film (not shown) between the polarizing element 220 and the adhesive layer 225.

The polarizing plate of the present invention can be applied to an image display device such as a liquid crystal display device or an organic light emitting device. Accordingly, an embodiment of the present invention relates to an image display device including the above polarizing plate.

Hereinafter, the present invention will be more specifically described based on examples, comparative examples, and experimental examples. In addition, the embodiments, the comparative examples, and the experimental examples are only intended to illustrate the present invention, and the scope of the present invention is not limited to the examples, comparative examples, and experimental examples.

Production Example 1: Manufacture of λ/4 retardation film

Coating layer formed of LC242 (manufactured by BASF Corporation) and LR-9000 (manufactured by BASF Corporation) dissolved in toluene was coated on a polyethylene terephthalate (PET) substrate of about 50 μm in a thickness of 15 μm. Composition. Thereafter, the solvent was removed by drying at 100 ° C for 1 minute, and then UV (ultraviolet) was irradiated for 1 minute at 40 mW/cm ² to thereby cure the retardation film.

Production Example 2: Fabrication of λ/4 retardation film

This was carried out in the same manner as in Production Example 1, except that the film was dried at 90 ° C for 1 minute, and irradiated with UV at 30 mW/cm ^{2 for} 2 minutes to produce a retardation film.

Production Example 3: Fabrication of λ/4 retardation film

This was carried out in the same manner as in Production Example 1, except that the film was dried at 60 ° C for 1 minute, and irradiated with UV at 30 mW/cm ^{2 for} 2 minutes to produce a retardation film.

Production Example 4: Fabrication of λ/4 retardation film

This was carried out in the same manner as in Production Example 1, except that the coating layer-forming composition was applied to a thickness of 17 μm to produce a retardation film.

Production Example 5: Fabrication of λ/4 retardation film

This was carried out in the same manner as in Production Example 2 except that the coating layer-forming composition was applied to a thickness of 17 μm to produce a retardation film.

Production Example 6: Fabrication of λ/4 retardation film

This was carried out in the same manner as in Production Example 3 except that the coating layer-forming composition was applied to a thickness of 17 μm to produce a retardation film.

Production Example 7: Fabrication of λ/4 retardation film

This was carried out in the same manner as in Production Example 1, except that the coating layer-forming composition was applied to a thickness of 20 μm to produce a retardation film.

Examples 1 to 3 and Comparative Examples 1 to 4: Fabrication of a polarizing plate

After the adhesive layer was bonded to the polarizing element including the protective film on one side, the λ/4 retardation films of Production Examples 1 to 7 were transferred, respectively. A polarizing plate is produced by laminating an adhesive layer on the lower surface of the retardation film.

Experimental Example 1: Assessment of visibility of unevenness

A polarizing plate manufactured according to the examples and the comparative examples was attached to an organic light-emitting device panel, and a phase difference was measured by Axoscan (Axoscan) to evaluate the visibility. The results are shown in Table 1 below.

According to the above Table 1, the polarizing plate of Examples 1 to 3 including the λ/4 retardation film having a full-width phase difference of 5 nm or less and a full-width phase difference of 1.5 nm or less and a full-amplitude phase difference of more than 5 nm The unevenness of the polarizing plates of Comparative Examples 1 to 4 in which the full-width phase difference was spread over a λ/4 retardation film of 1.5 nm was suppressed.

The specifics of the present invention have been described above in detail, but those skilled in the art to which the present invention pertains will be understood to be a preferred embodiment of the present invention. The scope is not limited to such preferred implementations. Various applications and changes can be made within the scope of the present invention based on the above-described contents as long as they have ordinary knowledge in the technical field to which the present invention pertains.

Therefore, the scope of the invention is defined by the scope of the claims and their equivalents.

100‧‧‧Polar plate

110‧‧‧Protective film

120‧‧‧Polarized elements

125‧‧‧Adhesive layer

130‧‧‧ phase difference film

135‧‧‧Adhesive layer

Claims (14)

A retardation film having a full-width phase difference of 5 nm or less and a dispersion of a full-width phase difference of 1.5 nm or less. The retardation film of claim 1, wherein the full-width phase difference is 2 nm or less, and the spread of the full-width phase difference is 1 nm or less. The phase difference film of claim 1, wherein the dispersion of the partial phase difference is 1 nm or less. The retardation film of claim 1, wherein the full-width phase difference is an in-plane phase difference obtained by measuring the full width of the retardation film. In the retardation film of claim 3, the partial phase difference is an in-plane phase difference measured at five places at intervals of 3 mm in a portion of the left side portion, the center portion, or the right side portion in a portion of 15 mm on the basis of the full width. The retardation film of claim 1, wherein the retardation film is a λ/4 retardation film. The retardation film of claim 1, wherein the retardation film is formed by coating a coating layer containing a photo-alignment polymer and a reactive liquid crystal compound on a transparent substrate and hardening the composition. A polarizing plate which is formed by laminating a polarizing element, such as the retardation film of any one of claims 1 to 7. The polarizing plate of claim 8 is obtained by laminating an absorption axis of the polarizing element and an optical axis of the retardation film within ±60°. The polarizing plate of claim 8, comprising a polarizing element, a protective film bonded to one surface of the polarizing element, a retardation film which is adhered to the other surface of the polarizing element via an adhesive layer, and bonded to the above The adhesive layer of the other side of the retardation film is formed. The polarizing plate of claim 10, further comprising a protective film between the polarizing element and the adhesive layer. The polarizing plate of claim 8, comprising a polarizing element, a protective film bonded to one surface of the polarizing element, and a retardation film which is adhered to the other surface of the polarizing element via an adhesive layer. The polarizing plate of claim 12, further comprising a protective film between the polarizing element and the adhesive layer. An image display device comprising the polarizing plate of claim 8.