JP2016038580A - Phase difference film and polarization plate including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference film capable of suppressing the unevenness failure occurring in a manufacturing process.SOLUTION: The full width phase difference of a phase difference film is 5 nm or less, and the dispersion of the full width phase difference is 1.5 nm or less. Using the phase difference film, a polarization plate includes a protective film 110 pasted on one surface of a polarizer 120, the phase difference film 130 pasted on the other surface of the polarizer via an adhesive layer 125, and an adhesive layer 135 pasted on the other surface of the phase difference film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a retardation film and a polarizing plate including the retardation film, and more particularly to a retardation film capable of suppressing unevenness in a manufacturing process and a polarizing plate including the retardation film.

  The retardation film is used for various purposes. Specifically, the liquid crystal display device is used for eliminating coloration of the image or expanding the viewing angle, and the organic light emitting device is used for antireflection or correction of the hue of the polarizing plate. Furthermore, the touch panel is used to improve visibility by reducing external light reflection.

  However, the retardation film may cause uneven spots due to errors or manufacturing defects that occur in the manufacturing process, which may be a problem when evaluating the visibility of the panel.

  However, so far, no method has been known that can effectively suppress the occurrence of unevenness in the retardation film.

Japanese Published Patent No. 10-312166

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a retardation film that can suppress unevenness in the manufacturing process.

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

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

  On the other hand, the present invention provides a retardation film having a full width retardation of 5 nm or less and a dispersion of full width retardation of 1.5 nm or less.

  In one embodiment of the present invention, the retardation film has a partial retardation distribution 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 the retardation film is laminated on a polarizer.

  On the other hand, the present invention provides an image display device comprising the polarizing plate.

  The retardation film which concerns on this invention can suppress the nonuniformity defect which generate | occur | produces in a manufacturing process, and can improve the visibility of a display panel.

It is sectional drawing which shows schematically the polarizing plate which concerns on one embodiment of this invention. It is sectional drawing which shows schematically the polarizing plate which concerns on other embodiment of this invention.

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

  One embodiment of the present invention relates to a retardation film having a full width retardation of 5 nm or less and a dispersion of full width retardation 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 distribution 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 dispersion of partial retardation is 1 nm or less.

  In the present invention, the full width retardation means an in-plane retardation measured with respect to the full width of the retardation film, and the partial retardation means with respect to the left side, center, or right side with respect to the full width. In-plane phase difference measured at 5 locations at intervals of 3 mm in a local area of 15 mm.

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

(Formula 1)
_{Re = (n x -n y)} × d
In the above formula,
n _x is the refractive index of the axis (slow axis) direction showing the maximum refractive index in the plane of the film,
n _y represents a refractive index in the direction perpendicular to the slow axis,
d represents the thickness (nm) of the film.

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

  In one embodiment of the present invention, the full width retardation of the retardation film is 5 nm or less, the dispersion of the full width retardation is 1.5 nm or less, preferably the full width retardation is 2 nm or less, and the full width retardation is 1 nm or less. By adjusting to, nonuniformity defects that occur during the manufacturing process can be suppressed.

  In another embodiment of the present invention, the full width retardation of the retardation film is adjusted to 5 nm or less, the dispersion of the full width retardation is adjusted to 1.5 nm or less, and the dispersion of the partial retardation is adjusted to 1 nm or less. Unevenness defects occurring during the process can be suppressed.

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

  The λ / 4 retardation film means a film that plays a role of giving a phase difference corresponding to ¼ wavelength to linearly polarized light that is polarized while passing through a polarizer, and changing the linearly polarized light into circularly knitted light.

  As a material capable of forming the retardation film according to an embodiment of the present invention, any suitable material can be adopted without any particular limitation as long as it can exhibit the above characteristics. For example, the retardation film can be produced by applying a coating layer-forming composition containing a photoalignable polymer and a reactive liquid crystal compound on a transparent substrate and curing it.

  Examples of the photoalignable polymer include polymers having a photosensitive structure. When a polymer having a photosensitive structure is irradiated with light, the photo-alignable polymer is aligned by isomerization or crosslinking of the photosensitive structure of the irradiated portion, and the force that aligns the liquid crystal component in a certain direction (alignment regulating force) ) Is expressed.

  Examples of the photosensitive structure include an azobenzene structure, a spiropyran structure, a spirobenzopyran structure, a photosensitive structure that is isomerized by light irradiation, such as a fulgide structure, a maleimide structure, a chalcone type structure, a cinnamic acid type structure, Examples thereof include a photosensitive structure that is crosslinked by light irradiation, such as a 2-vinylene structure and a 1,2-acetylene structure.

  Examples of the photo-alignable polymer include a polymer obtained by radical polymerization of a photosensitive structure and a monomer having one or more radical polymerizable groups (preferably a vinyl group, acryloyl group, or methacryloyl group). A polymer obtained by polymerizing a monomer having a photosensitive structure, two or more amino groups, and a dicarboxylic acid compound; polymerizing a monomer having a photosensitive structure, two or more carboxyl groups, and a diamine compound; The polymer obtained by carrying out chain polymerization such as anionic polymerization and cationic polymerization, coordination polymerization, or ring-opening polymerization of a monomer having a photosensitive structure. Among these, a polymer obtained by radical polymerization of a photosensitive structure and a monomer having one or more radical polymerizable groups is preferable.

  When the photo-alignable polymer is a polymer obtained by radical polymerization of a photosensitive structure and a monomer having one radical polymerizable group, the photosensitive structure and the radical polymerizable group in the monomer are linked via an alkylene group. Are preferably combined. The alkylene group preferably has 3 to 20 carbon atoms, more preferably 5 to 10 carbon atoms. 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 monomers each having a different photosensitive structure. Further, the photo-alignment polymer may include 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 the total constituent component (structural unit) of the photoalignable polymer is preferably 50 to 95 mol%, more Preferably it is 60-90 mol%, More preferably, it is the range of 70-80 mol%.

  Commercially available products may be used as the photoalignable polymer, and specific examples thereof include LR9000 commercially available from BASF. These photo-alignment polymers may be used alone or in combination.

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

  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 involved in the polymerization reaction of the reactive liquid crystal compound. Examples of the polymerizable group include a vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group, and oxetanyl group.

  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 phenyl ring (benzene ring), a cyclohexane ring, a naphthalene ring, a pyrimidine ring, a pyridine ring, and a thiophene ring. Among these, a phenyl ring (benzene ring) and a cyclohexane ring are preferable.

The linking group that links two or more ring _{structures, -CO-O -, - CH} 2 -CH 2 -, - CO-S -, - CO-NH -, - CH = CH -, - N = N- , And -C≡C-, among which -CO-O- is preferable.

  Commercially available products may be used as the reactive liquid crystal compound, and specific examples thereof include Palio Color (registered trademark) LC242 commercially available from BASF. These reactive liquid crystal compounds may be used alone or in combination.

  The coating layer forming composition may contain a polymerization initiator. Examples of the polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator, and a photopolymerization initiator is preferable because a polymerizable liquid crystal compound can be polymerized at a low temperature.

  Examples of the photopolymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts, and sulfonium salts. You may use a commercial item as a photoinitiator. Specifically, Irgacure (registered trademark) 907, Irgacure 184, Irgacure 651, Irgacure 819, Irgacure 250, Irgacure 369 (all of which are manufactured by BASF Japan Ltd.), Sequol (registered trademark) BZ, Sequol Z, Sequol BEE (all of which are manufactured by Seiko Chemical Co., Ltd.), kayacure (registered trademark) BP100 (manufactured by Nippon Kayaku Co., Ltd.), CYRACURE (registered trademark) UVI-6992 (Dow Chemical Co., Ltd.), Adeka optomer SP-152, Adeka optomer SP-170 (all are manufactured by ADEKA Co., Ltd.), TAZ-A, TAZ-PP (all are manufactured by DKSH Japan), TAZ-104 ( Sanwa Chemical Co., Ltd.).

  The coating layer forming composition preferably contains a solvent. The solvent may be any solvent that dissolves the components contained in the coating layer forming composition and is inert to the polymerization reaction of the reactive liquid crystal compound. Specifically, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene Alcohol solvents such as glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, propylene glycol monomethyl ether, phenol; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, ethyl lactate ; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone; pentane, hexane, heptane Aliphatic hydrocarbon solvents: toluene, aromatic hydrocarbon solvents such as xylene; nitriles solvents such as acetonitrile; tetrahydrofuran, ether solvents such as dimethoxyethane; chloroform, chlorinated solvents such as chlorobenzene; include. These solvents may be used alone or in combination of two or more.

  A method for applying the coating layer forming composition is not particularly limited, and specifically, spin coating, roll coating, defending coating, gravure coating, or the like may be used. It is preferable to determine the type and amount of solvent used according to the coating method.

  The solvent contained in the coating layer forming composition is evaporated in the drying process.

  Drying is not particularly limited, and may be performed using a normal 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, preferably 60 to 300 seconds. Further, the drying may be performed under the same temperature condition or may be performed while increasing the temperature stepwise.

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

  Examples of the light curing include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps. When considering the surface, it is preferable to use a high-pressure mercury lamp or a metal halide lamp.

The illuminance may be in the range of 30 to 300 mW / cm ² , preferably 30 to 250 mW / cm ² , more preferably 30 to 200 mW / cm ² . If the illuminance is less than 30 mW / cm ² , the curing time may be long and productivity may be inferior. If it exceeds 300 mW / cm ² , the film may be thermally damaged by high illuminance and deformed. is there.

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

  As the transparent substrate, a film excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy, and the like may be used. Specific examples include polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; cellulose resins such as diacetyl cellulose and triacetyl cellulose; polycarbonate resins; polymethyl (meth) acrylate, polyethyl Acrylic resins such as (meth) acrylates; Styrenic resins such as polystyrene and acrylonitrile-styrene copolymers; Polyolefin resins such as polyethylene, polypropylene, cyclo- or polyolefins having a norbornene structure, and ethylene-propylene copolymers; Vinyl resins; Amide resins such as nylon and aromatic polyamide; Imido resins; Polyether sulfone resins; Polyether ethers Tone resin; Polyphenylene sulfide resin; Vinyl alcohol resin; Vinylidene chloride resin; Vinyl butyral resin; Arylate resin; Polyoxymethylene resin; Film made of thermoplastic resin such as epoxy resin It's okay. Moreover, you may use the film which consists of thermosetting resins, such as (meth) acrylic-type, urethane type, an acrylic urethane type, an epoxy type, and a silicone type, or ultraviolet curable resin.

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

  The polarizer is an optical film that plays a role of changing incident natural light into a desired single polarization state (linear polarization state), and is not particularly limited as long as it can generally perform a polarization function in the field.

  Specifically, a PVA (polyvinyl alcohol) film is dyed with iodine or a heterochromatic dye and stretched in a certain direction, or a conductive lattice with a fine pattern having a polarizing function on a transparent substrate. In addition, a thin plate polarizing plate in which an insulating layer is coated on valleys and peaks of the lattice may be used.

  Moreover, the polarizing plate may further be provided with a protective film for protecting a mechanically weak polarizer on one or both sides of the polarizer. As the protective film, a film having different moisture permeability depending on the type of resin and having excellent transparency, mechanical strength, thermal stability, moisture shielding property, isotropic property, and the like may be used.

  In addition, the structure and manufacturing method of a polarizing plate should just be generally used in the said field | area, and are not specifically limited.

  In one embodiment of the present invention, the polarizing plate may be laminated so that the absorption axis of the polarizer and the optical axis of the retardation film are within ± 60 °. The angle is preferably within ± 60 ° in order to stably realize circularly polarized light.

  The optical axis means a slow axis or a fast axis, and unless otherwise specified, means a slow axis.

  Referring to FIG. 1, a polarizing plate 100 according to an embodiment of the present invention includes a polarizer 120, a protective film 110 bonded to one surface of the polarizer 120, and the other surface of the polarizer 120. And the pressure-sensitive adhesive layer 125, and the pressure-sensitive adhesive layer 135 bonded to the other surface of the phase-difference film 130.

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

  Referring to FIG. 2, a polarizing plate 200 according to another embodiment of the present invention includes a polarizer 220, a protective film 210 bonded to one surface of the polarizer 220, and the other surface of the polarizer 220. And a retardation film 230 bonded to each other with an adhesive layer 225 interposed therebetween.

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

  The polarizing plate according to the present invention is applicable to image display devices such as liquid crystal display devices and organic light-emitting elements. Therefore, an embodiment of the present invention relates to an image display device including the polarizing plate.

  Hereinafter, the present invention will be described more specifically by way of examples, comparative examples, and experimental examples. It should be apparent to those skilled in the art that these examples, comparative examples, and experimental examples are only for explaining the present invention and that the scope of the present invention is not limited thereto. .

Production Example 1: Production of λ / 4 retardation film Coating layer forming composition comprising LC242 (manufactured by BASF) and LR-9000 (manufactured by BASF) dissolved in toluene on a polyethylene terephthalate (PET) substrate of about 50 μm. The material was applied to a thickness of 15 μm. Thereafter, the solvent was removed by drying at 100 ° C. for 1 minute, and then cured by UV irradiation at 40 mW / cm ² for 1 minute to produce a retardation film.

Manufacture example 2: Manufacture of (lambda) / 4 phase difference film Although implemented by the same method as manufacture example 1, it dried at 90 degreeC for 1 minute and UV-irradiated for 2 minutes at 30 mW / cm < ² >, and manufactured the phase difference film.

Production Example 3: Production of λ / 4 Retardation Film The same method as in Production Example 1 was carried out except that drying was performed at 60 ° C. for 1 minute and UV irradiation was performed at 30 mW / cm ² for 2 minutes to produce a retardation film.

Production Example 4: Production of λ / 4 Retardation Film The same method as in Production Example 1 was carried out except that the coating layer-forming composition was applied to a thickness of 17 μm to produce a retardation film.

Production Example 5: Production of λ / 4 retardation film The same procedure as in Production Example 2 was carried out except that the coating layer-forming composition was applied to a thickness of 17 µm to produce a retardation film.

Production Example 6 Production of λ / 4 Retardation Film The same method as in Production Example 3 was carried out except that the coating layer forming composition was applied to a thickness of 17 μm to produce a retardation film.

Production Example 7 Production of λ / 4 Retardation Film The same method as in Production Example 1 was carried out 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: Production of Polarizing Plates After a pressure-sensitive adhesive layer was bonded to a polarizer including a protective film on one side, the λ / 4 retardation films of Production Examples 1 to 7 were respectively transferred. . A pressure-sensitive adhesive layer was bonded to the lower surface of the retardation film to produce a polarizing plate.

Experimental Example 1: Evaluation of visibility of unevenness A polarizing plate manufactured according to Examples and Comparative Examples was attached to an organic light-emitting element panel, and a phase difference was measured using Axoscan to evaluate visibility. . The results are shown in Table 1 below.

  As can be seen from Table 1, the polarizing plates of Examples 1 to 3 including a λ / 4 retardation film having a full width retardation of 5 nm or less and a dispersion of full width retardation of 1.5 nm or less according to the present invention. The occurrence of unevenness was suppressed as compared with the polarizing plates of Comparative Examples 1 to 4 including a λ / 4 retardation film having a full width retardation larger than 5 nm and a dispersion of full width retardation exceeding 1.5 nm.

  Although specific portions of the present invention have been described in detail above, such specific techniques are merely preferred embodiments for those having ordinary knowledge in the technical field to which the present invention belongs. Obviously, the scope of the present invention is not limited. A person having ordinary knowledge in the technical field to which the present invention pertains can make various applications and modifications within the scope of the present invention based on the above contents.

  Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

100, 200: Polarizing plate 110, 210: Protective film 120, 220: Polarizer 125, 135, 225: Adhesive layer 130, 230: Retardation film

Claims (14)

  A retardation film having a full width retardation of 5 nm or less and a dispersion of full width retardation of 1.5 nm or less.   The retardation film according to claim 1, wherein the full width retardation is 2 nm or less, and the dispersion of the full width retardation is 1 nm or less.   The retardation film according to claim 1, wherein the dispersion of the partial retardation is 1 nm or less.   The retardation film according to claim 1, wherein the full width retardation is an in-plane retardation measured with respect to the entire width of the retardation film.   4. The phase difference according to claim 3, wherein the partial phase difference is an in-plane phase difference measured at five locations at intervals of 3 mm in a local area of 15 mm with respect to the left side, center, or right side with respect to the entire width. the film.   The retardation film according to claim 1, wherein the retardation film is a λ / 4 retardation film.   The retardation film according to claim 1, wherein the retardation film is formed by applying and curing a coating layer forming composition containing a photoalignable polymer and a reactive liquid crystal compound on a transparent substrate.   The polarizing plate formed by laminating | stacking the retardation film in any one of Claims 1-7 on a polarizer.   The polarizing plate according to claim 8, wherein the polarizing plate is laminated so that the absorption axis of the polarizer and the optical axis of the retardation film are within ± 60 °.   The polarizing plate comprises a polarizer, a protective film bonded to one surface of the polarizer, a retardation film bonded to the other surface of the polarizer via an adhesive layer, and the retardation film The polarizing plate according to claim 8, comprising a pressure-sensitive adhesive layer bonded to the other surface.   The polarizing plate according to claim 10, further comprising a protective film between the polarizer and the pressure-sensitive adhesive layer.   The polarizing plate comprises a polarizer, a protective film bonded to one surface of the polarizer, and a retardation film bonded to the other surface of the polarizer via an adhesive layer. The polarizing plate according to claim 8.   The polarizing plate according to claim 12, further comprising a protective film between the polarizer and the pressure-sensitive adhesive layer.   An image display device comprising the polarizing plate according to claim 8.

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