JP2007156234A - Manufacturing method of optical film, optical film, and image display device using the optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently manufacturing an optical film which is excellent even in inclined directions with a high contrast over a wide range and a wide viewing angle; and to provide an optical film, and an image display device. <P>SOLUTION: This manufacturing method of an optical film includes: a step of transferring a first birefringent layer formed on the surface of a base A to the surface of an transparent protective film; a step of stacking a polarizer on this transparent protective film; a step of coating a negative orientation material on the surface of a base B; a step of applying an orientation process to this coated surface; a step of coating a liquid crystal composition on this orientation processed surface; a step of applying an orientation process to the liquid crystal material in this liquid crystal composition to form a second birefringent layer; and a step of transferring this second birefringent layer on the base B surface to the surface of the first birefringent layer. The angle α between the absorption axis of this polarizer and the delay axis of the first birefringent layer has a predetermined relationship against the angle β between the absorption axis of this polarizer and the delay axis of the second birefringent layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical film manufacturing method, an optical film, and an image display device using the optical film. More specifically, the present invention relates to a method for producing a broadband and wide viewing angle optical film with very high production efficiency, which has a small change in the retardation value with time and has excellent characteristics in an oblique direction, and The present invention relates to an optical film obtained by such a method, and an image display device using the optical film.

  Various image display devices such as liquid crystal display devices and electroluminescence (EL) displays generally use various optical films in which a polarizing film and a retardation plate are combined in order to perform optical compensation.

  A circularly polarizing plate which is a kind of the optical film can be usually produced by combining a polarizing film and a λ / 4 plate. However, the λ / 4 plate generally exhibits a characteristic that the phase difference value increases as the wavelength becomes shorter, that is, a so-called “positive wavelength dispersion characteristic”, and generally has a large wavelength dispersion characteristic. Therefore, there is a problem that desired optical characteristics (for example, a function as a λ / 4 plate) cannot be exhibited over a wide wavelength range. In order to avoid such problems, in recent years, as a phase difference plate exhibiting a wavelength dispersion characteristic in which a retardation value increases as the wavelength becomes longer, that is, a so-called “reverse dispersion characteristic”, for example, a modified cellulose film and Modified polycarbonate films have been proposed. However, these films have a problem in terms of cost.

  Therefore, at present, for a λ / 4 plate having positive wavelength dispersion characteristics, for example, by combining a retardation plate whose retardation value increases as it becomes longer wavelength side, or a λ / 2 plate, the above-mentioned λ / 4 plate is used. A method of correcting the wavelength dispersion characteristics of the plate is employed (see, for example, Patent Document 1).

  As described above, when the polarizing film, the λ / 4 plate, and the λ / 2 plate are combined, it is necessary to adjust the respective optical axes, that is, the angles between the absorption axis of the polarizing film and the slow axis of each retardation plate. However, since both the polarizing film and the retardation film made of a stretched film generally have an optical axis that depends on the stretching direction, in order to laminate them so that the absorption axis and the slow axis are at a desired angle, It is necessary to laminate the film after cutting it out according to the direction of the optical axis. Specifically, the absorption axis of the polarizing film is usually parallel to the stretching direction, and the slow axis of the retardation film is also parallel to the stretching direction. For this reason, in order to laminate | stack a polarizing film and a phase difference plate, for example so that the angle of an absorption axis and a slow axis may be 45 degrees, either one film is with respect to a longitudinal direction (stretching direction). It is necessary to cut in the direction of 45 degrees. When pasting after cutting out the film in this way, for example, there is a possibility that the angle of the optical axis varies in each cut out film, and as a result, there is a problem that the quality varies among products. . There is also a problem of cost and time. Furthermore, there is a problem that the waste increases due to the cutting and it is difficult to produce a large film.

  For such problems, for example, a method of adjusting the stretching direction such as stretching a polarizing film or a retardation plate in an oblique direction has been reported (for example, see Patent Document 2), but the adjustment is difficult. There is a problem with it.

Further, the angle between the absorption axis of the polarizing film and the slow axis of each retardation plate is currently adjusted for each product, and no comprehensive optimization means has been found.
Japanese Patent No. 3174367 JP 2003-195037 A

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is to provide an optical film with a wide bandwidth and a wide viewing angle that exhibits excellent contrast and has excellent characteristics in an oblique direction. The present invention provides an optical film obtained by such a method, an image display apparatus using the optical film, and an optical film obtained by such a method.

The method for producing the optical film of the present invention comprises:
A step of performing an alignment treatment on the surface of the substrate A;
Applying a liquid crystal composition to the surface of the substrate A that has been subjected to the alignment treatment;
Aligning the liquid crystal material in the liquid crystal composition according to the alignment direction of the substrate A to form a first birefringent layer;
Transferring the first birefringent layer formed on the surface of the substrate A to the surface of the transparent protective film;
Laminating a polarizer on the transparent protective film;
Applying a negative alignment material to the surface of the substrate B;
Applying an alignment treatment to the surface of the base material B coated with the negative alignment material;
Applying a liquid crystal composition to the surface of the substrate B on which the alignment treatment has been performed;
Aligning the liquid crystal material in the liquid crystal composition according to the alignment direction of the substrate B to form a second birefringent layer;
Transferring the second birefringent layer formed on the surface of the base material B to the surface of the first birefringent layer,
When the angle between the absorption axis of the polarizer and the slow axis of the first birefringent layer is α, and the angle between the absorption axis of the polarizer and the slow axis of the second birefringent layer is β , Angles α and β have the relationship of the following formula (1):
2α + 40 ° <β <2α + 50 ° (1).

  In a preferred embodiment, the polarizer and the transparent protective film to which the first birefringent layer is transferred are both long films. In the step of laminating the polarizer, the polarizer and the transparent protective film Long sides are continuously pasted together.

  In a preferred embodiment, the second birefringent layer formed on the surface of the substrate B is a long film, and in the step of forming the second birefringent layer, the polarizer, the first The transparent protective film to which the birefringent layer is transferred and the long sides of the second birefringent layer are continuously bonded together.

  In a preferred embodiment, the alignment process is at least one selected from the group consisting of a rubbing process, an oblique deposition method, a stretching process, a photo alignment process, a magnetic field alignment process, and an electric field alignment process.

  In a preferred embodiment, the liquid crystal composition includes at least one of a liquid crystal monomer and a liquid crystal polymer.

  In a preferred embodiment, the liquid crystal composition includes a polymerizable monomer and / or a crosslinkable monomer, and the liquid crystal alignment step further includes performing a polymerization treatment and / or a crosslinking treatment.

  In a preferred embodiment, the negative alignment material is at least one selected from a styrene resin, a (meth) acrylic resin, and a vinyl cinnamate resin.

  In a preferred embodiment, the first birefringent layer is a λ / 2 plate.

  In a preferred embodiment, the second birefringent layer is a λ / 4 plate.

  In a preferred embodiment, the method further includes forming a third birefringent layer having a refractive index distribution of nx = ny> nz on the opposite side of the second birefringent layer from the first birefringent layer.

  According to another aspect of the present invention, an optical film is provided. This optical film is manufactured by the above manufacturing method.

  According to another aspect of the present invention, an image display device is provided. The image display device includes the optical film.

  As described above, according to the present invention, since the slow axis of the first birefringent layer can be set in an arbitrary direction in the alignment treatment of the substrate A, the base A is stretched in the longitudinal direction (that is, long A long polarizing film (polarizer) having an absorption axis in the scale direction can be used. That is, the 1st birefringent layer formed on the base material A by which orientation processing was made to make a predetermined angle with respect to the long direction, the long transparent protective film, and the long polarizing film (polarized light Can be continuously bonded together (so-called roll-to-roll) with their respective longitudinal directions aligned. Therefore, an optical film can be obtained with very excellent production efficiency. Furthermore, according to this method, it is not necessary to cut and laminate the film obliquely with respect to the longitudinal direction (stretching direction). As a result, there is no variation in the angle of the optical axis in each cut out film, and as a result, an optical film having no quality variation among products can be obtained. Furthermore, since no waste is generated by cutting, an optical film can be obtained at low cost. In addition, a large polarizing plate can be easily manufactured. In addition, by using a negative orientation material when forming the second birefringent layer, the absorption axis of the polarizer and the first birefringent layer ( The angle α formed by the slow axis of the λ / 2 plate and the angle β formed by the absorption axis of the polarizer and the slow axis of the second birefringent layer (λ / 4 plate) are expressed as 2α + 40 ° <β < A broadband and wide viewing angle optical film or image display device can be obtained that can be optimized in the relationship of 2α + 50 °, exhibits excellent contrast, and has excellent characteristics in an oblique direction. Moreover, since this relationship is comprehensive, it is not necessary to examine the stacking direction by trial and error for each product. That is, in most combinations of a polarizer, a λ / 2 plate, and a λ / 4 plate, a very excellent circular polarization characteristic can be realized by using this relationship. As a result, the optimization of the circular polarization characteristic can be performed very generally and easily. Furthermore, by adopting a method of transferring a long film obtained by forming the second birefringent layer on the substrate B to the surface of the first birefringent layer, the polarizer, the first The transparent protective film to which the birefringent layer has been transferred and the second birefringent layer can be continuously bonded together (so-called roll-to-roll) with their respective longitudinal directions aligned. Therefore, as described above, an optical film can be obtained with very excellent production efficiency.

A. Optical film A-1. 1 is a schematic cross-sectional view of an optical film according to a preferred embodiment of the present invention. The optical film 10 includes a polarizer 11, a first birefringent layer 12, a second birefringent layer 13, and a third birefringent layer 14 in this order. A first protective layer (transparent protective film) 15 is provided between the polarizer 11 and the first birefringent layer 12, and if necessary, the first protective layer (transparent protective film) 15 of the polarizer. A second protective layer 16 is provided on the opposite side.

  The first birefringent layer 12 can function as a so-called λ / 2 plate. In this specification, the λ / 2 plate refers to converting linearly polarized light having a specific vibration direction into linearly polarized light having a vibration direction orthogonal to the vibration direction of the linearly polarized light, or converting right circularly polarized light to the left circle. It has a function of converting into polarized light (or converting left circularly polarized light into right circularly polarized light). The second birefringent layer 13 can function as a so-called λ / 4 plate. In this specification, the λ / 4 plate refers to a plate having a function of converting linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light).

  FIG. 2 is an exploded perspective view for explaining the optical axis of each layer constituting the optical film according to a preferred embodiment of the present invention (in FIG. 2, the second protective layer 16 is omitted for the sake of clarity). ) The first birefringent layer 12 is laminated such that the slow axis B defines a predetermined angle α with respect to the absorption axis A of the polarizer 11. The second birefringent layer 13 is laminated so that the slow axis C defines a predetermined angle β with respect to the absorption axis A of the polarizer 11. The slow axis refers to the direction in which the in-plane refractive index is maximized.

In the present invention, the angle α and the angle β preferably have the relationship of the following formula (1):
2α + 40 ° <β <2α + 50 ° (1).
The relationship between the angle α and the angle β is more preferably 2α + 42 ° <β <2α + 48 °, particularly preferably 2α + 43 ° <β <2α + 47 °, and most preferably β = 2α + 45 °. When the angle α and the angle β have such a relationship, an optical film having very excellent circular polarization characteristics can be obtained. Moreover, since this relationship is comprehensive, it is not necessary to examine the stacking direction by trial and error for each product. That is, in most combinations of a polarizer, a λ / 2 plate, and a λ / 4 plate, a very excellent circular polarization characteristic can be realized by using this relationship.

  The angle α is preferably + 10 ° to + 23 ° or −10 ° to −23 °, more preferably + 12 ° to + 21 ° or −12 ° to −21 °, and particularly preferably + 14 ° to + 19 °. Or it is -14 degrees--19 degrees. Accordingly, in the most preferred embodiment (β = 2α + 45 °), the angle β is preferably + 65 ° to + 85 ° or −65 ° to −85 °, more preferably + 70 ° to + 85 ° or −70 ° to It is −85 °, particularly preferably + 75 ° to + 85 ° or −75 ° to −85 °. In this specification, “substantially parallel” includes the case of 0 ° ± 3.0 °, preferably 0 ° ± 1.0 °, and more preferably 0 ° ± 0. 5 °. “Substantially orthogonal” includes the case of 90 ° ± 3.0 °, preferably 90 ° ± 1.0 °, and more preferably 90 ° ± 0.5 °.

  The total thickness of the optical film of the present invention is preferably 80 to 250 μm, more preferably 90 to 200 μm, and most preferably 100 to 180 μm. The optical film of the present invention can greatly contribute to thinning of a liquid crystal display device. Hereinafter, the detail of each layer which comprises the optical film of this invention is demonstrated.

A-2. First Birefringent Layer As described above, the first birefringent layer 12 can function as a so-called λ / 2 plate. With the first birefringent layer functioning as a λ / 2 plate, the wavelength dispersion characteristics of the second birefringent layer functioning as a λ / 4 plate (particularly the wavelength range where the phase difference deviates from λ / 4), The phase difference can be adjusted appropriately. The in-plane retardation (Δnd) of the first birefringent layer is preferably 180 to 300 nm, more preferably 200 to 290 nm, and most preferably 230 to 280 nm at a wavelength of 590 nm. The in-plane phase difference (Δnd) is obtained from the equation Δnd = (nx−ny) × d. Here, nx is the refractive index in the direction of the slow axis, ny is the refractive index in the direction of the fast axis (the direction perpendicular to the slow axis in the plane), and d is the first birefringent layer. Is the thickness. Furthermore, the first birefringent layer 12 preferably has a refractive index distribution of nx> ny = nz. nz is the refractive index in the thickness direction. In the present specification, “ny = nz” includes not only the case where ny and nz are exactly equal, but also the case where ny and nz are substantially equal.

  The thickness of the first birefringent layer can be set so as to function most appropriately as a λ / 2 plate. In other words, the thickness can be set so as to obtain a desired in-plane retardation. Specifically, the thickness is preferably 0.5 to 5 μm, more preferably 1 to 4 μm, and most preferably 1.5 to 3 μm.

  As a material for forming the first birefringent layer, any appropriate material can be adopted as long as the above characteristics are obtained. A liquid crystal material is preferable, and a liquid crystal material (nematic liquid crystal) in which the liquid crystal phase is a nematic phase is more preferable. By using a liquid crystal material, the difference between nx and ny of the obtained birefringent layer can be significantly increased compared to a non-liquid crystal material. As a result, the thickness of the birefringent layer for obtaining a desired in-plane retardation can be significantly reduced. As such a liquid crystal material, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal material may exhibit a liquid crystallinity mechanism either lyotropic or thermotropic. The alignment state of the liquid crystal is preferably homogeneous alignment. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

  When the liquid crystal material is a liquid crystal monomer, for example, a polymerizable monomer and / or a crosslinkable monomer is preferable. This is because the alignment state of the liquid crystalline monomer can be fixed by polymerizing or crosslinking the liquid crystalline monomer, as will be described later. After aligning the liquid crystalline monomers, for example, if the liquid crystalline monomers are polymerized or crosslinked, the alignment state can be fixed thereby. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed first birefringent layer, for example, a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change specific to the liquid crystal compound does not occur. As a result, the first birefringent layer is a birefringent layer that is not affected by temperature changes and has extremely high stability.

  Any appropriate liquid crystal monomer can be adopted as the liquid crystal monomer. For example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US52111877), EP66137 (US4388453), WO93 / 22397, EP02661712, DE195504224, DE44081171, and GB2280445 can be used. Specific examples of such a polymerizable mesogenic compound include, for example, the trade name LC242 from BASF, the trade name E7 from Merck, and the trade name LC-Silicon-CC3767 from Wacker-Chem.

  As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable, and specific examples include a monomer represented by the following formula (1). These liquid crystal monomers can be used alone or in combination of two or more.

In the above formula (1), A ¹ and A ² each represent a polymerizable group and may be the same or different. One of A ¹ and A ² may be hydrogen. X is each independently a single bond, —O—, —S—, —C═N—, —O—CO—, —CO—O—, —O—CO—O—, —CO—NR—. , —NR—CO—, —NR—, —O—CO—NR—, —NR—CO—O—, —CH ₂ —O— or —NR—CO—NR, wherein R is H or C _1. -C ₄ alkyl, M represents a mesogen group.

  In the above formula (1), X may be the same or different, but is preferably the same.

Among the monomers of the above formula (1), each A ² is preferably located in the ortho position with respect to A ¹ .

Furthermore, A ¹ and A ² are each independently represented by the following formula ZX- (Sp) _n (2)
And A ¹ and A ² are preferably the same group.

In the above formula (2), Z represents a crosslinkable group, X is as defined in the above formula (1), and Sp is a linear or branched substituent having 1 to 30 carbon atoms or It represents a spacer composed of an unsubstituted alkyl group, and n represents 0 or 1. A carbon chain in Sp may be, for example, oxygen in ether functional group, sulfur in a thioether functional group, it may be interrupted by such alkylimino group nonadjacent imino or C ₁ -C _4.

  In the above formula (2), Z is preferably any one of the atomic groups represented by the following formula. In the following formula, examples of R include groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, and t-butyl.

  In the above formula (2), Sp is preferably any one of the atomic groups represented by the following formula. In the following formula, m is preferably 1 to 3 and p is preferably 1 to 12.

In the above formula (1), M is preferably represented by the following formula (3). In the following formula (3), X is the same as defined in the above formula (1). Q represents, for example, a substituted or unsubstituted linear or branched alkylene or aromatic hydrocarbon group. Q may be, for example, a substituted or unsubstituted linear or branched C ₁ -C ₁₂ alkylene.

  When Q is an aromatic hydrocarbon atomic group, for example, an atomic group represented by the following formula or a substituted analog thereof is preferable.

The substituted analog of the aromatic hydrocarbon group represented by the above formula may have, for example, 1 to 4 substituents per aromatic ring, and may include one aromatic ring or one group. Each may have 1 or 2 substituents. The above substituents may be the same or different. As the substituent, for example, C ₁ -C ₄ alkyl, nitro, F, Cl, Br, a halogen such as I, phenyl, C ₁ -C ₄ alkoxy, and the like.

  Specific examples of the liquid crystal monomer include monomers represented by the following formulas (4) to (19).

  The temperature range in which the liquid crystal monomer exhibits liquid crystal properties varies depending on the type. Specifically, the temperature range is preferably 40 to 120 ° C, more preferably 50 to 100 ° C, and most preferably 60 to 90 ° C.

A-3. Second Birefringent Layer As described above, the second birefringent layer 13 can function as a so-called λ / 4 plate. According to the present invention, the wavelength dispersion characteristic of the second birefringent layer functioning as a λ / 4 plate is corrected by the optical characteristics of the first birefringent layer functioning as the λ / 2 plate, thereby obtaining a wide wavelength range. The circular polarization function in a range can be exhibited. The in-plane retardation (Δnd) of such a second birefringent layer is preferably 90 to 180 nm, more preferably 90 to 160 nm, and most preferably 100 to 150 nm at a wavelength of 550 nm. The second birefringent layer 13 preferably has a refractive index distribution of nx> ny = nz.

  The thickness of the second birefringent layer can be set so as to function most appropriately as a λ / 4 plate. In other words, the thickness can be set so as to obtain a desired in-plane retardation. Specifically, the thickness is preferably 0.5 to 3.0 μm, more preferably 0.7 to 2.0 μm, and most preferably 1.0 to 1.6 μm.

  As a material for forming the second birefringent layer, any appropriate material can be adopted as long as the above characteristics are obtained. A liquid crystal material is preferable, and a liquid crystal material (nematic liquid crystal) in which the liquid crystal phase is a nematic phase is more preferable. By using a liquid crystal material, the difference between nx and ny of the obtained birefringent layer can be significantly increased compared to a non-liquid crystal material. As a result, the thickness of the birefringent layer for obtaining a desired in-plane retardation can be significantly reduced. As such a liquid crystal material, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal material may exhibit a liquid crystallinity mechanism either lyotropic or thermotropic. The alignment state of the liquid crystal is preferably homogeneous alignment. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

  The liquid crystal polymer or liquid crystal monomer as the liquid crystal material forming the second birefringent layer is the same as the liquid crystal polymer or liquid crystal monomer as the liquid crystal material forming the first birefringent layer.

A-4. Polarizer Any appropriate polarizer may be employed as the polarizer 11 depending on the purpose. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferable because of its high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

  A polarizer uniaxially stretched by adsorbing iodine to a polyvinyl alcohol film can be produced by, for example, dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. . If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, or may be immersed in an aqueous solution such as potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing.

  By washing the polyvinyl alcohol film with water, not only can the surface of the polyvinyl alcohol film be cleaned and the anti-blocking agent can be washed, but also the effect of preventing unevenness such as uneven dyeing can be obtained by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

A-5. Protective layer The said 1st protective layer (transparent protective film) 15 and the 2nd protective layer 16 consist of arbitrary appropriate films which can be used as a protective film of a polarizing plate. Specific examples of the material that is the main component of such a film include cellulose resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, Examples thereof include transparent resins such as polysulfone, polystyrene, polynorbornene, polyolefin, acrylic, and acetate. In addition, thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition. TAC, polyimide resin, polyvinyl alcohol resin, and glassy polymer are preferable.

  The protective layer is preferably transparent and has no color. Specifically, the thickness direction retardation value is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and most preferably −70 nm to +70 nm.

  As the thickness of the protective layer, any appropriate thickness can be adopted as long as the preferable thickness direction retardation is obtained. Specifically, the thickness of the protective layer is preferably 5 mm or less, more preferably 1 mm or less, particularly preferably 1 to 500 μm, and most preferably 5 to 150 μm.

  The surface of the second protective layer opposite to the polarizer (that is, the outermost part of the polarizing plate) may be subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, an antiglare treatment, or the like as necessary.

A-6. Third Birefringent Layer In the present invention, as described above, the third birefringent layer 14 may be formed on the opposite side of the second birefringent layer from the first birefringent layer. The third birefringent layer has a refractive index profile of nx = ny> nz and can function as a so-called negative C plate. When the third birefringent layer has such a refractive index distribution, the birefringence of the liquid crystal layer of the VA mode liquid crystal cell can be particularly favorably compensated. That is, the third birefringent layer eliminates the cause of deterioration in viewing angle characteristics due to the collapse of the isotropic property of liquid crystal molecules when viewed from an oblique direction in a VA mode (vertical alignment mode) liquid crystal display device. Is for. As a result, a liquid crystal display device with significantly improved viewing angle characteristics can be obtained.

  In the present specification, “nx = ny” includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal, so that the third birefringent layer has an in-plane retardation Δnd. And may have a slow axis. The in-plane retardation Δnd that is practically acceptable for the negative C plate is 0 to 20 nm, preferably 0 to 10 nm, and more preferably 0 to 5 nm.

  The thickness direction retardation Rth of the third birefringent layer is 30 to 300 nm, preferably 60 to 180 nm, more preferably 80 to 150 nm, and still more preferably 100 to 120 nm. The thickness of the third birefringent layer from which such a thickness direction retardation Rth can be obtained can vary depending on the material used.

  The thickness of the third birefringent layer is preferably 1 to 100 μm, more preferably 1 to 50 μm, and still more preferably 1 to 10 μm.

  Examples of the material for forming the third birefringent layer include any appropriate polymer film, a film obtained by curing a liquid crystalline material exhibiting a cholesteric liquid crystal phase, a discotic liquid crystalline compound and a cured film, and an inorganic layered compound. Can be mentioned.

  Specific examples of the polymer film forming the third birefringent layer include cellulose resins such as diacetyl cellulose and triacetyl cellulose, acrylic resins such as polymethyl methacrylate, polycarbonate resins, and the like. Also, cycloolefin resin, norbornene resin, polyethylene resin, polyolefin resin such as polypropylene, ethylene / propylene copolymer, vinyl chloride resin, amide resin such as nylon and aromatic polyamide, aromatic polyimide, polyimide amide, etc. Imide resin, sulfone resin, polyether sulfone resin, polyether ether ketone resin, polyphenylene sulfide resin, vinyl alcohol resin, vinylidene chloride resin, vinyl butyral resin, arylate resin, polyoxymethylene resin And epoxy resins. Moreover, the polymer film which consists of a blend of the said resin, etc. are mentioned.

  The polymer film used as the third birefringent layer can be obtained by forming a film by a casting method, or can be obtained by stretching by any appropriate stretching method. Examples of the stretching method include a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and a longitudinal and transverse sequential biaxial stretching method. The said extending | stretching processing method can be performed using suitable extending machines, such as a roll extending machine, a tenter, and a biaxial stretching machine, for example. Moreover, the said extending | stretching can also be performed in 2 steps or 3 steps or more. The direction in which the polymer film is stretched may be the film length direction (MD direction) or the width direction (TD direction).

  Preferably, the material for forming the third birefringent layer includes a polyimide film described in JP-A-2003-287750, a nematic liquid crystal monomer described in JP-A-2003-287623, and a polymerizable chiral agent. Examples thereof include a film obtained by curing a liquid crystalline material exhibiting a cholesteric liquid crystal phase, and a negative C plate described in JP-A No. 2004-326089. Moreover, the film which apply | coated and dried on the base material the discotic liquid crystal non-orientation layer as described in Unexamined-Japanese-Patent No. 7-281028, and the water-swellable inorganic layered compound as described in Unexamined-Japanese-Patent No. 9-80233 are mentioned. . Among the above materials, a polyimide film described in JP-A No. 2003-287750 and a liquid crystalline material exhibiting a cholesteric liquid crystal phase including a nematic liquid crystal monomer and a polymerizable chiral agent described in JP-A No. 2003-287623. A cured film is particularly preferred.

B. Manufacturing method of optical film The manufacturing method of the optical film of the present invention includes:
A step of performing an alignment treatment on the surface of the substrate A;
Applying a liquid crystal composition to the surface of the substrate A that has been subjected to the alignment treatment;
Aligning the liquid crystal material in the liquid crystal composition according to the alignment direction of the substrate A to form a first birefringent layer;
Transferring the first birefringent layer formed on the surface of the substrate A to the surface of the transparent protective film;
Laminating a polarizer on the transparent protective film;
Applying a negative alignment material to the surface of the substrate B;
Applying an alignment treatment to the surface of the base material B coated with the negative alignment material;
Applying a liquid crystal composition to the surface of the substrate B on which the alignment treatment has been performed;
Aligning the liquid crystal material in the liquid crystal composition according to the alignment direction of the substrate B to form a second birefringent layer;
Transferring the second birefringent layer formed on the surface of the base material B to the surface of the first birefringent layer,
When the angle between the absorption axis of the polarizer and the slow axis of the first birefringent layer is α, and the angle between the absorption axis of the polarizer and the slow axis of the second birefringent layer is β , Angles α and β have the relationship of the following formula (1):
2α + 40 ° <β <2α + 50 ° (1).

  The order of the above steps and / or the film subjected to the orientation treatment can be appropriately changed according to the laminated structure of the target optical film. For example, the polarizer lamination step may be performed after any birefringent layer forming step or lamination step. Details of each step will be described below.

B-1. Step of forming first birefringent layer

  A first birefringent layer is formed on the surface of the transparent protective film. The detailed procedure of the process of forming the first birefringent layer is as follows.

First, a liquid crystal composition (liquid crystal material-containing coating solution) is applied to the base material A whose surface has been subjected to orientation treatment.

  As the substrate A, any appropriate substrate is used as long as the appropriate first birefringent layer in the present invention is obtained. Any appropriate substrate can be adopted as the substrate A. Specific examples include a glass substrate, a metal foil, a plastic sheet, or a plastic film. In addition, although the orientation film may be provided on the base material A, it does not need to be provided. Any appropriate film can be adopted as the plastic film. Specific examples include films made of transparent polymers such as polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, and acrylic polymers such as polymethyl methacrylate. It is done. Also, styrene polymers such as polystyrene and acrylonitrile / styrene copolymers, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, nylon and aromatic polyamides. Examples thereof include a film made of a transparent polymer such as an amide polymer. Furthermore, imide polymer, sulfone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene Examples thereof include films made of transparent polymers such as epoxy polymers, epoxy polymers and blends thereof. Among these, a polyethylene terephthalate (PET) film is preferable.

  The thickness of the substrate A is preferably 20 to 100 μm, more preferably 30 to 90 μm, and most preferably 30 to 80 μm. By having a thickness in such a range, the strength to favorably support the very thin first birefringent layer in the laminating process is given, and the operability such as slipping property and roll running property is appropriately maintained. Is done.

  As the alignment treatment of the surface of the substrate A, any appropriate alignment treatment is used as long as the appropriate first birefringent layer in the present invention is obtained. Examples include rubbing treatment, oblique vapor deposition method, stretching treatment, photo-alignment treatment, magnetic field orientation treatment, and electric field orientation treatment, and rubbing treatment is preferable.

  The orientation direction of the orientation treatment is a direction that forms a predetermined angle with the absorption axis of the polarizer when the polarizers are stacked. This orientation direction is substantially the same as the direction of the slow axis of the first birefringent layer 12 to be formed. Therefore, the predetermined angle is preferably + 10 ° to + 23 ° or −10 ° to −23 °, more preferably + 12 ° to + 21 ° or −12 ° to the longitudinal direction of the transparent protective film. It is −21 °, particularly preferably + 14 ° to + 19 ° or −14 ° to −19 °.

  The liquid crystal composition forming the first birefringent layer is applied to the surface of the substrate A that has been subjected to the alignment treatment, and the liquid crystal material is aligned on the substrate A. The alignment of the liquid crystal material is performed by processing at a temperature showing a liquid crystal phase according to the type of the liquid crystal material used. By performing such a temperature treatment, the liquid crystal material takes a liquid crystal state, and the liquid crystal material is aligned according to the alignment direction of the surface of the substrate A. Thereby, birefringence is generated in the layer formed by coating, and the first birefringent layer is formed.

  The liquid crystal composition is prepared by dissolving or dispersing a liquid crystal material in an appropriate solvent.

  As the solvent, any suitable solvent that can dissolve or disperse the liquid crystal material can be adopted. The type of solvent used can be appropriately selected according to the type of liquid crystal material and the like. Specific examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenol, p-chlorophenol, and o-chlorophenol. , M-cresol, o-cresol, p-cresol and other phenols, benzene, toluene, xylene, mesitylene, methoxybenzene, 1,2-dimethoxybenzene and other aromatic hydrocarbons, acetone, methyl ethyl ketone (MEK), methyl Ketone solvents such as isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone and N-methyl-2-pyrrolidone, ester solvents such as ethyl acetate, butyl acetate and propyl acetate Alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, dimethylformamide, dimethyl Amide solvents such as acetamide, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, or carbon disulfide, ethyl cellosolve, butyl cellosolve, ethyl cellosolve, etc. It is done. Preferred are toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl cellosolve. These solvents may be used alone or in combination of two or more.

  The content of the liquid crystal material in the coating liquid can be appropriately set according to the type of the liquid crystal material, the target layer thickness, and the like. Specifically, the content of the liquid crystal material is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and most preferably 15 to 30% by weight.

  The said coating liquid can further contain arbitrary appropriate additives as needed. Specific examples of the additive include a polymerization initiator and a crosslinking agent. These are particularly preferably used when a liquid crystal monomer is used as the liquid crystal material. Specific examples of the polymerization agent include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Specific examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, and the like. These may be used alone or in combination of two or more. Specific examples of other additives include anti-aging agents, modifiers, surfactants, dyes, pigments, anti-discoloring agents, and ultraviolet absorbers. These can also be used alone or in combination of two or more. Examples of the anti-aging agent include phenol compounds, amine compounds, organic sulfur compounds, and phosphine compounds. Examples of the modifier include glycols, silicones, and alcohols. The surfactant is used, for example, to smooth the surface of the optical film, and specific examples include silicone-based, acrylic-based, and fluorine-based surfactants.

The coating amount of the coating solution can be appropriately set according to the concentration of the coating solution, the target layer thickness, and the like. For example, when the liquid crystal material concentration of the coating liquid is 20% by weight, the coating amount is preferably 0.03 to 0.17 ml, more preferably 0.05 per area (100 cm ² ) of the base material A. ˜0.15 ml, most preferably 0.08 to 0.12 ml.

  Any appropriate method can be adopted as the coating method. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, and a spray coating method.

  Next, the liquid crystal material forming the first birefringent layer is aligned according to the alignment direction of the surface of the substrate A. The alignment of the liquid crystal material is performed by processing at a temperature showing a liquid crystal phase according to the type of the liquid crystal material used. By performing such a temperature treatment, the liquid crystal material takes a liquid crystal state, and the liquid crystal material is aligned according to the alignment direction of the surface of the substrate A. Thereby, birefringence is generated in the layer formed by coating, and the first birefringent layer is formed.

  The processing temperature can be appropriately determined according to the type of liquid crystal material. Specifically, processing temperature becomes like this. Preferably it is 40-120 degreeC, More preferably, it is 50-100 degreeC, Most preferably, it is 60-90 degreeC. The treatment time is preferably 30 seconds or longer, more preferably 1 minute or longer, particularly preferably 2 minutes or longer, and most preferably 4 minutes or longer. When the treatment time is less than 30 seconds, the liquid crystal material may not take a sufficient liquid crystal state. On the other hand, the treatment time is preferably 10 minutes or less, more preferably 8 minutes or less, and most preferably 7 minutes or less. When processing time exceeds 10 minutes, there exists a possibility that an additive may sublime.

  Moreover, when using the said liquid-crystal monomer as a liquid-crystal material, it is preferable to give a polymerization process or a crosslinking process further to the layer formed by the said coating. By performing the polymerization treatment, the liquid crystal monomer is polymerized, and the liquid crystal monomer is fixed as a repeating unit of the polymer molecule. Further, by performing the crosslinking treatment, the liquid crystal monomer forms a three-dimensional network structure, and the liquid crystal monomer is fixed as a part of the crosslinked structure. As a result, the alignment state of the liquid crystal material is fixed. The polymer or three-dimensional network structure formed by polymerizing or cross-linking the liquid crystal monomer is “non-liquid crystalline”. Therefore, the formed first birefringent layer has, for example, a temperature change peculiar to liquid crystal molecules. No transition to liquid crystal phase, glass phase, or crystal phase occurs due to.

  The specific procedure of the above-mentioned polymerization treatment or crosslinking treatment can be appropriately selected depending on the kind of polymerization initiator and crosslinking agent used. For example, light irradiation may be performed when a photopolymerization initiator or a photocrosslinking agent is used, and ultraviolet irradiation may be performed when an ultraviolet polymerization initiator or an ultraviolet crosslinking agent is used. Light or ultraviolet irradiation time, irradiation intensity, total irradiation amount, etc. are set appropriately according to the type of liquid crystal material, the type of base material A and the type of alignment treatment, the characteristics desired for the first birefringent layer, etc. Can be done.

  Next, the first birefringent layer formed on the substrate A is transferred to the surface of the transparent protective film. The transfer method is not particularly limited. For example, the transfer is performed by attaching the first birefringent layer supported by the substrate A to the transparent protective film via an adhesive. By adopting the method of transfer, an optical film having excellent production efficiency and excellent adhesion between films (layers) can be obtained.

  A typical example of the adhesive is a curable adhesive. Typical examples of the curable adhesive include a photocurable adhesive such as an ultraviolet curable adhesive, a moisture curable adhesive, and a thermosetting adhesive. Specific examples of the thermosetting adhesive include thermosetting resin adhesives such as epoxy resins, isocyanate resins, and polyimide resins. Specific examples of the moisture curable adhesive include isocyanate resin-based moisture curable adhesive. A moisture curable adhesive (especially an isocyanate resin-based moisture curable adhesive) is preferred. Moisture curable adhesives cure by reacting with moisture in the air, adsorbed water on the surface of the adherend, active hydrogen groups such as hydroxyl groups and carboxyl groups, and so on. It can be cured and has excellent operability. Furthermore, since it is not necessary to heat for curing, the first birefringent layer and the transparent protective film are not heated at the time of bonding (adhesion). As a result, since there is no concern about heat shrinkage, even when the first birefringent layer and the transparent protective film are very thin as in the present invention, cracks during lamination can be remarkably prevented. The isocyanate resin adhesive is a general term for polyisocyanate adhesives and polyurethane resin adhesives.

  As the curable adhesive, for example, a commercially available adhesive may be used, or the above various curable resins may be dissolved or dispersed in a solvent to prepare a curable resin adhesive solution (or dispersion). Good. When preparing a solution (or dispersion liquid), the content of the curable resin in the solution is preferably 10 to 80% by weight, more preferably 20 to 65% by weight, and particularly preferably the solid content weight. It is 25 to 65% by weight, and most preferably 30 to 50% by weight. As a solvent to be used, any appropriate solvent can be adopted depending on the type of curable resin. Specific examples include ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene and the like. These may be used alone or in combination of two or more.

The coating amount of the adhesive can be appropriately set according to the purpose. For example, the coating amount is preferably 0.3 to 3 ml, more preferably 0.5 to ² ml, most preferably 1 to 1 per area (cm ² ) of the first birefringent layer or the transparent protective film. 2 ml. After coating, the solvent contained in the adhesive is volatilized by natural drying or heat drying as necessary. The thickness of the adhesive layer thus obtained is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, and most preferably 1 μm to 10 μm. The indentation hardness (Microhardness) of the adhesive layer is preferably 0.1 to 0.5 GPa, more preferably 0.2 to 0.5 GPa, and most preferably 0.3 to 0.4 GPa. . In addition, since the indentation hardness has a known correlation with Vickers hardness, it can also be converted into Vickers hardness. The indentation hardness can be calculated from the indentation depth and the indentation load using, for example, a thin film hardness meter (for example, trade name MH4000, trade name MHA-400) manufactured by NEC Corporation.

  Finally, if the base material A is peeled from the first birefringent layer, the lamination of the first birefringent layer and the transparent protective film is completed.

B-2. Polarizer Laminating Step Further, a polarizer is laminated on the surface of the transparent protective film opposite to the first birefringent layer. As described above, the lamination of the polarizer can be performed at any appropriate point in the production method of the present invention. For example, a polarizer may be previously laminated on a transparent protective film, may be laminated after forming the first birefringent layer, or may be laminated after forming the second birefringent layer.

  Any appropriate laminating method (for example, adhesion) can be adopted as a laminating method of the transparent protective film and the polarizer. Adhesion can be performed using any suitable adhesive or adhesive. The type of adhesive or pressure-sensitive adhesive can be appropriately selected depending on the type of adherend (that is, the transparent protective film and the polarizer). Specific examples of the adhesive include polymer adhesives such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, and polyether, isocyanate adhesives, rubber adhesives, and the like. Specific examples of the pressure sensitive adhesive include acrylic, vinyl alcohol, silicone, polyester, polyurethane, polyether, isocyanate, and rubber pressure sensitive adhesives.

  The thickness of the adhesive or pressure-sensitive adhesive is not particularly limited, but is preferably 10 to 200 nm, more preferably 15 to 180 nm, and most preferably 20 to 150 nm.

  According to the production method of the present invention, since the slow axis of the first birefringent layer can be set in the orientation treatment of the transparent protective film, it is stretched in the longitudinal direction (that is, the absorption axis is set in the longitudinal direction). A long polarizing film (polarizer) can be used. That is, a long transparent protective film that has been subjected to an orientation treatment so as to form a predetermined angle with respect to the long direction and a long polarizing film (polarizer) are continuously aligned in the long direction. Can be pasted together. Therefore, an optical film can be obtained with very excellent production efficiency. Furthermore, according to this method, it is not necessary to cut and laminate the film obliquely with respect to the longitudinal direction (stretching direction). As a result, there is no variation in the angle of the optical axis in each cut out film, and as a result, an optical film having no quality variation among products can be obtained. Furthermore, since no waste is generated by cutting, an optical film can be obtained at low cost. In addition, a large polarizing plate can be easily manufactured. In addition, the direction of the absorption axis of the polarizer is substantially parallel to the long direction of the long film.

B-3. Step of forming second birefringent layer: orientation treatment of substrate B Further, a second birefringent layer is formed on the surface of the first birefringent layer. First, a step of applying a negative alignment material to the surface of the substrate B and a step of applying an alignment treatment to the surface of the substrate B coated with the negative alignment material are performed.

  As the base material B, any appropriate base material can be adopted as long as the appropriate second birefringent layer in the present invention is obtained. Specific examples include a glass substrate, a metal foil, a plastic sheet, or a plastic film. In addition, although the orientation film may be provided on the base material B, it does not need to be provided. Any appropriate film can be adopted as the plastic film. Specific examples include films made of transparent polymers such as polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, and acrylic polymers such as polymethyl methacrylate. It is done. Also, styrene polymers such as polystyrene and acrylonitrile / styrene copolymers, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, nylon and aromatic polyamides. Examples thereof include a film made of a transparent polymer such as an amide polymer. Furthermore, imide polymer, sulfone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene Examples thereof include films made of transparent polymers such as epoxy polymers, epoxy polymers and blends thereof. Among these, a polyethylene terephthalate (PET) film is preferable. These films may be subjected to an easy adhesion treatment.

  The thickness of the base material B is preferably 20 to 100 μm, more preferably 30 to 90 μm, and most preferably 30 to 80 μm. By having a thickness in such a range, the strength to favorably support the very thin second birefringent layer in the laminating process is given, and the operability such as slipping property and roll running property is appropriately maintained. Is done.

  In the present invention, a negative alignment material is applied to the surface of the substrate B. Preferably, the negative alignment material is dissolved in a solvent and applied to the surface of the substrate B. The concentration of the negative alignment material in the solvent may be any appropriate concentration as long as the effect of the present invention is not impaired, but is preferably 1 to 50% by weight, more preferably 2 to 40% by weight, and still more preferably Is 3 to 30% by weight.

  Any appropriate negative alignment material can be adopted as the negative alignment material. Preferably, it is at least one selected from styrene resins, (meth) acrylic resins, and vinyl cinnamate resins. Specific examples of the styrene resin include polystyrene and a styrene-maleic anhydride copolymer. Specific examples of the (meth) acrylic resin include benzyl methacrylate resin. Specific examples of the vinyl cinnamate resin include polyvinyl cinnamate.

  Any appropriate solvent can be adopted as a solvent for dissolving the negative alignment material. Specific examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenol, p-chlorophenol, and o-chlorophenol. , M-cresol, o-cresol, p-cresol and other phenols, benzene, toluene, xylene, mesitylene, methoxybenzene, 1,2-dimethoxybenzene and other aromatic hydrocarbons, acetone, methyl ethyl ketone (MEK), methyl Ketone solvents such as isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone and N-methyl-2-pyrrolidone, ester solvents such as ethyl acetate, butyl acetate and propyl acetate Alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, dimethylformamide, dimethyl Amide solvents such as acetamide, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, or carbon disulfide, ethyl cellosolve, butyl cellosolve, ethyl cellosolve, etc. It is done. Preferred are toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl cellosolve. These solvents may be used alone or in combination of two or more.

  The coating amount of the coating liquid obtained by dissolving the negative alignment material in a solvent can be appropriately set according to the concentration of the coating liquid, the thickness of the target layer, and the like.

  Any appropriate method can be adopted as a coating method of the coating solution. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, and a spray coating method.

  The thickness (after drying) of the coating solution is preferably 0.1 to 10 μm, more preferably 0.3 to 5 μm, and still more preferably 0.5 to 3 μm.

  Next, an orientation treatment is performed on the surface of the obtained base material B on which the negative orientation material is applied. As the alignment treatment of the surface of the substrate B, any appropriate alignment treatment is used as long as the appropriate second birefringent layer in the present invention is obtained. Examples include rubbing treatment, oblique vapor deposition method, stretching treatment, photo-alignment treatment, magnetic field orientation treatment, and electric field orientation treatment, and rubbing treatment is preferable.

  Since the alignment treatment is performed on the surface coated with the negative alignment material, the direction of the slow axis of the formed second birefringent layer 13 and the alignment direction of the alignment treatment are substantially orthogonal. Make a relationship. Therefore, the angle α (the angle formed between the absorption axis of the polarizer and the orientation direction of the transparent protective film) and the angle β formed between the absorption axis of the polarizer and the slow axis of the second birefringent layer are expressed by the above formula ( 1) In order to have the relationship (2α + 40 ° <β <2α + 50), the orientation direction of the surface of the base material B coated with the negative orientation material is in the longitudinal direction of the base material B. And is preferably + 5 ° to + 25 ° or −5 ° to −25 °, more preferably + 5 ° to + 20 ° or −5 ° to −20 °, and particularly preferably + 5 ° to + 15 ° or −5. ° to -15 °.

B-4. Step of forming second birefringent layer: Coating step of liquid crystal material for forming second birefringent layer Next, the liquid crystal as described in the above section A-2 on the surface of the base material B subjected to the alignment treatment A coating liquid (liquid crystal composition) containing the material is applied, and then the liquid crystal material in the coating liquid is aligned to form a second birefringent layer. Specifically, a coating liquid in which a liquid crystal material is dissolved or dispersed in a suitable solvent is prepared, and this coating liquid may be applied to the surface of the base material B subjected to the alignment treatment. The alignment process of the liquid crystal material will be described in the section B-5 described later.

  As the solvent, any suitable solvent that can dissolve or disperse the liquid crystal material can be adopted. The type of solvent used can be appropriately selected according to the type of liquid crystal material and the like. Specific examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenol, p-chlorophenol, and o-chlorophenol. , M-cresol, o-cresol, p-cresol and other phenols, benzene, toluene, xylene, mesitylene, methoxybenzene, 1,2-dimethoxybenzene and other aromatic hydrocarbons, acetone, methyl ethyl ketone (MEK), methyl Ketone solvents such as isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone and N-methyl-2-pyrrolidone, ester solvents such as ethyl acetate, butyl acetate and propyl acetate Alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, dimethylformamide, dimethyl Amide solvents such as acetamide, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, or carbon disulfide, ethyl cellosolve, butyl cellosolve, ethyl cellosolve, etc. It is done. Preferred are toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl cellosolve. These solvents may be used alone or in combination of two or more.

  The content of the liquid crystal material in the liquid crystal composition (coating liquid) can be appropriately set according to the type of the liquid crystal material, the thickness of the target layer, and the like. Specifically, the content of the liquid crystal material is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and most preferably 15 to 30% by weight.

  The liquid crystal composition (coating liquid) may further contain any appropriate additive as necessary. Specific examples of the additive include a polymerization initiator and a crosslinking agent. These are particularly preferably used when a liquid crystal monomer is used as the liquid crystal material. Specific examples of the polymerization initiator include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Specific examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, and the like. These may be used alone or in combination of two or more. Specific examples of other additives include anti-aging agents, modifiers, surfactants, dyes, pigments, anti-discoloring agents, and ultraviolet absorbers. These can also be used alone or in combination of two or more. Examples of the anti-aging agent include phenol compounds, amine compounds, organic sulfur compounds, and phosphine compounds. Examples of the modifier include glycols, silicones, and alcohols. The surfactant is used, for example, to smooth the surface of the optical film, and specific examples include silicone-based, acrylic-based, and fluorine-based surfactants.

The coating amount of the coating liquid can be appropriately set according to the concentration of the coating liquid, the thickness of the target layer, and the like. For example, when the concentration of the liquid crystal material in the coating solution is 20% by weight, the coating amount is preferably 0.03 to 0.17 ml, more preferably 0.05 per area (100 cm ² ) of the transparent protective film. ˜0.15 ml, most preferably 0.08 to 0.12 ml.

  Any appropriate method can be adopted as the coating method. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, and a spray coating method.

B-5. Step of forming second birefringent layer: Step of aligning liquid crystal material for forming second birefringent layer Next, a liquid crystal material for forming the second birefringent layer is formed according to the alignment direction of the surface of the base material B. Orient. As described above, since the alignment treatment is performed on the surface coated with the negative alignment material, the direction of the slow axis of the formed second birefringent layer 13 and the alignment direction of the alignment treatment Are substantially orthogonal. The alignment of the liquid crystal material is performed by processing at a temperature showing a liquid crystal phase according to the type of the liquid crystal material used. By performing such temperature treatment, the liquid crystal material takes a liquid crystal state, and the liquid crystal material is aligned according to the alignment direction of the surface of the base material B. As a result, birefringence occurs in the layer formed by coating, and a second birefringent layer is formed.

  As described above, the treatment temperature can be appropriately determined according to the type of the liquid crystal material. Specifically, processing temperature becomes like this. Preferably it is 40-120 degreeC, More preferably, it is 50-100 degreeC, Most preferably, it is 60-90 degreeC. The treatment time is preferably 30 seconds or longer, more preferably 1 minute or longer, particularly preferably 2 minutes or longer, and most preferably 4 minutes or longer. When the treatment time is less than 30 seconds, the liquid crystal material may not take a sufficient liquid crystal state. On the other hand, the treatment time is preferably 10 minutes or less, more preferably 8 minutes or less, and most preferably 7 minutes or less. When processing time exceeds 10 minutes, there exists a possibility that an additive may sublime.

  Moreover, when using the liquid crystal monomer as described in the above section A-2 as the liquid crystal material, it is preferable to further subject the layer formed by the coating to a polymerization treatment or a crosslinking treatment. By performing the polymerization treatment, the liquid crystal monomer is polymerized, and the liquid crystal monomer is fixed as a repeating unit of the polymer molecule. Further, by performing the crosslinking treatment, the liquid crystal monomer forms a three-dimensional network structure, and the liquid crystal monomer is fixed as a part of the crosslinked structure. As a result, the alignment state of the liquid crystal material is fixed. The polymer or three-dimensional network structure formed by polymerizing or cross-linking the liquid crystal monomer is “non-liquid crystalline”. Therefore, the formed first birefringent layer has, for example, a temperature change peculiar to liquid crystal molecules. No transition to liquid crystal phase, glass phase, or crystal phase occurs due to.

  The specific procedure of the above-mentioned polymerization treatment or crosslinking treatment can be appropriately selected depending on the kind of polymerization initiator and crosslinking agent used. For example, light irradiation may be performed when a photopolymerization initiator or a photocrosslinking agent is used, and ultraviolet irradiation may be performed when an ultraviolet polymerization initiator or an ultraviolet crosslinking agent is used. Light or ultraviolet irradiation time, irradiation intensity, total irradiation amount, etc. are appropriately set according to the type of liquid crystal material, the type of transparent protective film, the type of alignment treatment, the characteristics desired for the first birefringent layer, etc. Can be done.

  As described above, since the alignment treatment is performed on the surface coated with the negative alignment material, the direction of the slow axis of the formed second birefringent layer 13 and the alignment direction of the alignment treatment Are substantially orthogonal. Therefore, the angle β between the direction of the slow axis of the second birefringent layer and the absorption axis of the polarizer is preferably + 65 ° to + 85 ° or −65 ° to −85 °, more preferably + 70 ° to It is + 85 ° or −70 ° to −85 °, particularly preferably + 75 ° to + 85 ° or −75 ° to −85 °.

  Next, the second birefringent layer formed on the substrate B is transferred to the surface of the first birefringent layer. The transfer method is not particularly limited. For example, the transfer is performed by bonding the second birefringent layer supported by the base material B to the first birefringent layer via an adhesive. By adopting the method of transfer, an optical film having excellent production efficiency and excellent adhesion between films (layers) can be obtained.

  A typical example of the adhesive is a curable adhesive. Typical examples of the curable adhesive include a photocurable adhesive such as an ultraviolet curable adhesive, a moisture curable adhesive, and a thermosetting adhesive. Specific examples of the thermosetting adhesive include thermosetting resin adhesives such as epoxy resins, isocyanate resins, and polyimide resins. Specific examples of the moisture curable adhesive include isocyanate resin-based moisture curable adhesive. A moisture curable adhesive (especially an isocyanate resin-based moisture curable adhesive) is preferred. Moisture curable adhesives cure by reacting with moisture in the air, adsorbed water on the surface of the adherend, active hydrogen groups such as hydroxyl groups and carboxyl groups, and so on. It can be cured and has excellent operability. Furthermore, since it is not necessary to heat for curing, the first birefringent layer and the second birefringent layer are not heated during bonding (adhesion). As a result, since there is no fear of heat shrinkage, even when the first birefringent layer and the second birefringent layer are very thin as in the present invention, cracks during lamination can be remarkably prevented. The isocyanate resin adhesive is a general term for polyisocyanate adhesives and polyurethane resin adhesives.

  As the curable adhesive, for example, a commercially available adhesive may be used, or the above various curable resins may be dissolved or dispersed in a solvent to prepare a curable resin adhesive solution (or dispersion). Good. When preparing a solution (or dispersion liquid), the content of the curable resin in the solution is preferably 10 to 80% by weight, more preferably 20 to 65% by weight, and particularly preferably the solid content weight. It is 25 to 65% by weight, and most preferably 30 to 50% by weight. As a solvent to be used, any appropriate solvent can be adopted depending on the type of curable resin. Specific examples include ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene and the like. These may be used alone or in combination of two or more.

The coating amount of the adhesive can be appropriately set according to the purpose. For example, the coating amount is preferably 0.3 to 3 ml, more preferably 0.5 to ² ml, most preferably per area (cm ² ) of the first birefringent layer or the second birefringent layer. Is 1-2 ml. After coating, the solvent contained in the adhesive is volatilized by natural drying or heat drying as necessary. The thickness of the adhesive layer thus obtained is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, and most preferably 1 μm to 10 μm. The indentation hardness (Microhardness) of the adhesive layer is preferably 0.1 to 0.5 GPa, more preferably 0.2 to 0.5 GPa, and most preferably 0.3 to 0.4 GPa. . In addition, since the indentation hardness has a known correlation with Vickers hardness, it can also be converted into Vickers hardness. The indentation hardness can be calculated from the indentation depth and the indentation load using, for example, a thin film hardness meter (for example, trade name MH4000, trade name MHA-400) manufactured by NEC Corporation.

  Finally, if the base material B is peeled from the second birefringent layer, the lamination of the second birefringent layer and the first birefringent layer is completed.

B-7. Specific Manufacturing Procedure An example of a specific procedure of the manufacturing method of the present invention will be described with reference to FIGS. 3 to 6, reference numerals 111, 111 ′, 112, 113, 114, 115, and 116 are rolls for winding a film and / or a laminate that form each layer.

  First, a long polymer film as a raw material for a polarizer is prepared, and dyeing, stretching, and the like are performed as described in the above section A-4. Stretching is continuously performed in the longitudinal direction of the long polymer film. As a result, as shown in the perspective view of FIG. 3, a long polarizer 11 having an absorption axis in the long direction (stretching direction: arrow A direction) is obtained.

  On the other hand, as shown in the perspective view of FIG. 4A, a long base material 17 is prepared, and a rubbing process is performed on one surface of the base material 17 by a rubbing roll 120. At this time, the rubbing direction is a direction having a predetermined angle with respect to the longitudinal direction of the substrate 17, for example, preferably + 10 ° to + 23 ° or −10 ° to −23 °, and more preferably + 12 ° to It is + 21 ° or −12 ° to −21 °, particularly preferably + 14 ° to + 19 ° or −14 ° to −19 °. Next, as shown in the perspective view of FIG. 4B, the first birefringent layer 12 is formed on the base material 17 subjected to the rubbing process as described in the section B-1. In the first birefringent layer 12, the liquid crystal material is aligned along the rubbing direction, so that the slow axis direction is substantially the same direction as the rubbing direction of the substrate 17 (arrow B direction).

  Next, as shown in the schematic diagram of FIG. 5A, a transparent protective film (being a second protective layer) 16, a polarizer 11, a transparent protective film (being a protective layer) 15, and a first The birefringent layer 12 and the laminate 121 of the base material 17 are sent out in the directions of the arrows, and bonded together with an adhesive or the like (not shown) in a state in which the respective long directions are aligned to form a laminate 123 ′. Further, as shown in FIG. 5B, the base material 17 is peeled off from the laminate 123 ′, and the laminate 123 (the protective layer 16, the polarizer 11, the protective layer 15, and the first birefringent layer 12) is removed. Form. In addition, in Fig.5 (a), the code | symbol 122 shows the guide roll for bonding films together (same also in FIG. 6).

  Furthermore, as shown in the schematic diagram of FIG. 6A, a laminated body 125 (a substrate 26 on which the second birefringent layer 13 is applied) is prepared, and this is laminated with a laminated body 123 (second The protective layer 16, the polarizer 11, the first protective layer 15, and the first birefringent layer 12) are sent out in the directions of the arrows, and adhesives or the like (not shown) in a state where the respective longitudinal directions are aligned. Paste together. Finally, the base material 26 is peeled from the laminated body bonded as shown in FIG.

  When the optical film of the present invention includes the third birefringent layer 14, the surface of the second birefringent layer 13 of the optical film obtained above is applied by the method described in the above section A-6. The third birefringent layer 14 may be formed.

  As described above, the optical film 10 of the present invention can be obtained.

C. Other components of optical film The optical film of the present invention may further include other optical layers. As such another optical layer, any appropriate optical layer may be employed depending on the purpose and the type of the image display device. Specific examples include a birefringent layer (retardation film), a liquid crystal film, a light scattering film, and a diffraction film.

  The optical film of the present invention may further have an adhesive layer as an outermost layer on at least one side. Thus, by having the adhesion layer as the outermost layer, for example, lamination with other members (for example, liquid crystal cell) becomes easy, and peeling from other members of the optical film can be prevented. Any appropriate material can be adopted as the material of the pressure-sensitive adhesive layer. Specific examples of the pressure-sensitive adhesive include those described in the above section B-2. Preferably, a material excellent in hygroscopicity and heat resistance is used. This is because foaming and peeling due to moisture absorption, deterioration of optical characteristics due to a difference in thermal expansion, and warpage of the liquid crystal cell can be prevented.

  Practically, the surface of the pressure-sensitive adhesive layer can be covered with any appropriate separator until the optical film is actually used to prevent contamination. The separator can be formed by, for example, a method of providing a release coat with a release agent such as silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide, or the like on any appropriate film as necessary.

  Each layer in the optical film of the present invention has been imparted with an ultraviolet absorbing ability, for example, by treatment with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It may be a thing.

D. Use of optical film The optical film of the present invention can be suitably used for various image display devices (for example, liquid crystal display devices, self-luminous display devices). Specific examples of the applicable image display device include a liquid crystal display device, an EL display, a plasma display (PD), and a field emission display (FED). When the optical film of the present invention is used in a liquid crystal display device, it is useful for viewing angle compensation, for example. The optical film of the present invention is used in, for example, a circular polarization mode liquid crystal display device, and is used in a homogeneous alignment type TN liquid crystal display device, a horizontal electrode type (IPS) type liquid crystal display device, a vertical alignment (VA) type liquid crystal display device, and the like. It is particularly useful. Moreover, when using the optical film of this invention for EL display, it is useful for electrode reflection prevention, for example.

D. Image Display Device A liquid crystal display device will be described as an example of the image display device of the present invention. Here, a liquid crystal panel used in a liquid crystal display device will be described. As for other configurations of the liquid crystal display device, any appropriate configuration may be adopted depending on the purpose. FIG. 7 is a schematic cross-sectional view of a liquid crystal panel according to a preferred embodiment of the present invention. The liquid crystal panel 100 includes a liquid crystal cell 20, retardation plates 30 and 30 ′ disposed on both sides of the liquid crystal cell 20, and polarizing plates 10 and 10 ′ disposed on the outer sides of the respective retardation plates. As the retardation plates 30 and 30 ′, any appropriate retardation plate can be adopted depending on the purpose and the alignment mode of the liquid crystal cell. Depending on the purpose and the alignment mode of the liquid crystal cell, one or both of the retardation plates 30 and 30 ′ may be omitted. The polarizing plate 10 is the optical film of the present invention. This polarizing plate (elliptical polarizing plate) 10 is disposed so that the birefringent layers 12 and 13 are between the polarizer 11 and the liquid crystal cell 20. The polarizing plate 10 ′ is any appropriate polarizing plate. The polarizing plates 10, 10 ′ are typically arranged so that the absorption axes of the polarizers are orthogonal to each other. As shown in FIG. 7, in the liquid crystal display device (liquid crystal panel) of the present invention, the optical film 10 of the present invention is preferably arranged on the viewing side (upper side). The liquid crystal cell 20 includes a pair of glass substrates 21 and 21 'and a liquid crystal layer 22 as a display medium disposed between the substrates. One substrate (active matrix substrate) 21 ′ includes a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the active element, and a signal line for supplying a source signal. Are provided (both not shown). The other glass substrate (color filter substrate) 21 is provided with a color filter (not shown). The color filter may be provided on the active matrix substrate 21 ′. The distance (cell gap) between the substrates 21 and 21 'is controlled by a spacer (not shown). An alignment film (not shown) made of polyimide, for example, is provided on the side of the substrates 21, 21 ′ in contact with the liquid crystal layer 22.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples. The measuring method of each characteristic in an Example is as follows.

(1) Retardation measurement Refractive indexes nx, ny and nz of a sample film are measured by an automatic birefringence measuring device (manufactured by Oji Scientific Instruments Co., Ltd., automatic birefringence meter KOBRA21ADH), and in-plane retardation Δnd and thickness direction The phase difference Rth was calculated. The measurement temperature was 23 ° C. and the measurement wavelength was 590 nm.

(2) Measurement of thickness The thickness of the first birefringent layer was measured by an interference film thickness measurement method using MCPD2000 manufactured by Otsuka Electronics. The thicknesses of other various films were measured using a dial gauge.

(3) Measurement and Evaluation of Contrast Ratio With BM-5 manufactured by Topcon Corporation, the white luminance and black luminance of PSP were measured from directly above 50 cm, and the value of white luminance / black luminance was taken as the contrast ratio.

(4) Measurement and evaluation of viewing angle It measured using EZ-Contrast made from ELDIM.

[Example 1]
a. Alignment treatment of substrate A (preparation of alignment substrate)
Using a rubbing cloth, a polyethylene terephthalate (PET) film (Lumirror R41, manufactured by Toray Industries, Inc.) (thickness 50 μm) is angled 17.5 ° with respect to the longitudinal direction (from the longitudinal direction to the counterclockwise direction 17. 5 °) to create an alignment substrate.

b. Production of first birefringent layer First, 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name: Palocolor LC242, liquid crystal transition temperature = 60 ° C.) and a photopolymerization initiator (Ciba Special) for the polymerizable liquid crystal compound. Tea Chemicals Co., Ltd .: 0.5 g of trade name Irgacure 907) was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution). And after apply | coating the said coating liquid with the bar coater on the orientation base material produced as mentioned above, the liquid crystal was orientated by heat-drying for 2 minutes at 90 degreeC. The liquid crystal layer thus formed was irradiated with 300 mJ / cm ² of light using a high-pressure mercury lamp, and the liquid crystal layer was cured to form a first birefringent layer on the substrate A. . The thickness and retardation of the first birefringent layer were adjusted by changing the coating amount of the coating liquid. The thickness of the formed first birefringent layer was 2.5 μm, and the in-plane retardation value Δnd was 270 nm.

c. Production of Second Birefringent Layer A styrene-maleic anhydride copolymer (manufactured by Nova Chemical Co., Ltd., trade name: Dilark D332) was dissolved in methyl ethyl ketone so as to be 15% by weight. This solution was applied to easy-adhesion-treated PET (manufactured by Mitsubishi Polyester Film Co., Ltd., trade name: T600E) using a # 7 wire bar so that the thickness after drying was 1 μm and dried. Next, using a rubbing cloth, rubbing was performed at an angle of −10 ° (10 ° from the long direction to the clockwise direction).

Subsequently, 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name: Paliocolor LC242, liquid crystal transition temperature = 60 ° C.) and a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by Ciba Specialty Chemicals: trade name) 0.5 g of Irgacure 907) was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution). And after apply | coating the said coating liquid with the bar coater on the base material produced as mentioned above, the liquid crystal was orientated by heat-drying at 90 degreeC for 2 minute (s). The liquid crystal layer thus formed is irradiated with light of 300 mJ / cm ² using a high-pressure mercury lamp to cure the liquid crystal layer, thereby forming a second birefringent layer on the PET substrate. did. The angle of the slow axis of the liquid crystal in the obtained second birefringent layer was 80 ° (80 ° from the longitudinal direction to the counterclockwise direction). The thickness and retardation of the second birefringent layer were adjusted by changing the coating amount of the coating liquid. The thickness of the formed second birefringent layer was 1.3 μm, and the in-plane retardation value Δnd was 140 nm.

d. Preparation of Polarizer After a polyvinyl alcohol film (manufactured by Kuraray Co., Ltd.) is dyed in an aqueous solution containing iodine, it is uniaxially stretched about 6 times between rolls having different speed ratios in an aqueous solution containing boric acid. A polarizer was obtained.

e. Preparation of optical film Triacetyl cellulose film (second protective layer 16), polarizer 11 obtained in d above, triacetyl cellulose film (first protective layer 15), first birefringent layer 12 and substrate 17 laminates 121 were laminated by the manufacturing procedure shown in FIGS. 3 to 5, and the base material 17 was peeled off. Furthermore, the laminate 125 of the second birefringent layer 13 and the PET base material 26 obtained in the above c is laminated by the manufacturing procedure shown in FIG. 6, the PET base material 26 is peeled off, and the structure shown in FIG. Such an optical film (elliptical polarizing plate) was obtained. The thickness of the laminate portion of the first protective layer 15 / polarizer 11 / second protective layer 16 is 108 μm, and the adhesive layer used between the first protective layer 15 and the first birefringent layer 12 ( The thickness of the isocyanate-based adhesive) was 4 μm, and the thickness of the adhesive layer (isocyanate-based adhesive) used between the first birefringent layer 12 and the second birefringent layer 13 was 4 μm.

  Furthermore, 90 parts by weight of a nematic liquid crystalline compound represented by the following formula (10), 10 parts by weight of a chiral agent represented by the following formula (38), a photopolymerization initiator (Irgacure 907, manufactured by Ciba Specialty Chemicals) 5 Part by weight and 300 parts by weight of methyl ethyl ketone were uniformly mixed to prepare a liquid crystal coating liquid. This liquid crystal coating solution is coated on the surface of the second birefringent layer 13 of the above optical film (elliptical polarizing plate), heat-treated at 80 ° C. for 3 minutes, and then irradiated with ultraviolet rays for polymerization treatment. The birefringent layer 14 was formed. The thickness of the third birefringent layer 14 was 1.0 μm, the in-plane retardation Δnd was 0 nm, and the thickness direction retardation Rth was 110 nm.

f. Production of liquid crystal panel and liquid crystal display device Take out the liquid crystal cell from the Sony PlayStation Portable, and bond the third birefringent side of the optical film obtained above with an acrylic adhesive (thickness: 20 μm). A liquid crystal panel was obtained. Using the obtained liquid crystal panel, a liquid crystal display device was produced by a normal procedure.

g. Evaluation The contrast and viewing angle were evaluated. The maximum viewing angle showing contrast 50 was a polar angle of 50 ° from the normal direction.

[Example 2]
When producing the second birefringent layer, instead of using a solution in which styrene-maleic anhydride copolymer (manufactured by Nova Chemical Co., Ltd., trade name: Dilark D332) was dissolved in methyl ethyl ketone so as to be 15% by weight, The same procedure as in Example 1 was performed except that a solution in which polystyrene resin (trade name: G590, manufactured by Nippon Polystyrene Co., Ltd.) was dissolved in xylene so as to be 15% by weight was used.

  The contrast and viewing angle were evaluated. The maximum viewing angle showing contrast 50 was a polar angle of 50 ° from the normal direction.

[Comparative Example 1]
A long norbornene-based film (manufactured by Nippon Zeon Co., Ltd., trade name: ZEONOR, thickness 60 μm) is horizontally stretched at a stretching temperature of 140 ° C. at a stretch ratio of 1.5 times, and a film A having a thickness of 40 μm (in-plane retardation Δnd) = 140 nm, thickness direction retardation Rth = 220 nm).

  Triacetyl cellulose film (second protective layer 16), polarizer 11 obtained in d of Example 1, triacetyl cellulose film (first protective layer 15), first birefringent layer 12 and substrate 17 The laminate 121 and the film A were laminated by the production procedure shown in FIGS. 3 to 6 to obtain an optical film (elliptical polarizing plate). The thickness of the laminate portion of the first protective layer 15 / polarizer 11 / second protective layer 16 is 108 μm, and the adhesive layer used between the first protective layer 15 and the first birefringent layer 12 ( The thickness of the pressure-sensitive adhesive layer used between the first birefringent layer 12 and the film A was 12 μm.

  Further, in the same manner as in Example 1, a liquid crystal panel and a liquid crystal display device were produced.

  The contrast and viewing angle were evaluated. The maximum viewing angle showing contrast 50 was 30 ° polar angle from the normal direction.

  The optical film of the present invention can be suitably used for various image display devices (for example, liquid crystal display devices, self-luminous display devices).

It is a schematic sectional drawing of the optical film by preferable embodiment of this invention. 1 is an exploded perspective view of an optical film according to a preferred embodiment of the present invention. It is a perspective view which shows the outline of one process in an example of the manufacturing method of the optical film of this invention. It is a perspective view which shows the outline of another process in an example of the manufacturing method of the optical film of this invention. It is a schematic diagram which shows the outline of another process in an example of the manufacturing method of the optical film of this invention. It is a schematic diagram which shows the outline of another process in an example of the manufacturing method of the optical film of this invention. It is a schematic sectional drawing of the liquid crystal panel used for the liquid crystal display device by preferable embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical film 11 Polarizer 12 1st birefringent layer 13 2nd birefringent layer 14 3rd birefringent layer 15 1st protective layer 16 2nd protective layer 20 Liquid crystal cell 100 Liquid crystal panel

Claims (12)

A step of performing an alignment treatment on the surface of the substrate A;
Applying a liquid crystal composition to the surface of the substrate A that has been subjected to the alignment treatment;
Aligning the liquid crystal material in the liquid crystal composition according to the alignment direction of the substrate A to form a first birefringent layer;
Transferring the first birefringent layer formed on the surface of the substrate A to the surface of the transparent protective film;
Laminating a polarizer on the transparent protective film;
Applying a negative alignment material to the surface of the substrate B;
Applying an alignment treatment to the surface of the base material B coated with the negative alignment material;
Applying a liquid crystal composition to the surface of the substrate B on which the alignment treatment has been performed;
Aligning the liquid crystal material in the liquid crystal composition according to the alignment direction of the substrate B to form a second birefringent layer;
Transferring the second birefringent layer formed on the surface of the base material B to the surface of the first birefringent layer,
When the angle between the absorption axis of the polarizer and the slow axis of the first birefringent layer is α, and the angle between the absorption axis of the polarizer and the slow axis of the second birefringent layer is β , The angles α and β have the relationship of the following formula (1):
Manufacturing method of optical film:
2α + 40 ° <β <2α + 50 ° (1).   The polarizer and the transparent protective film to which the first birefringent layer has been transferred are both long films, and the polarizer and the transparent protective film have continuous long sides in the step of laminating the polarizer. The manufacturing method of Claim 1 bonded together.   The second birefringent layer formed on the surface of the base material B is a long film, and in the step of forming the second birefringent layer, the polarizer and the first birefringent layer are transferred. The manufacturing method according to claim 1 or 2, wherein the transparent protective film and the long sides of the second birefringent layer are continuously bonded to each other.   The alignment process according to any one of claims 1 to 3, wherein the alignment process is at least one selected from the group consisting of a rubbing process, an oblique vapor deposition method, a stretching process, a photo alignment process, a magnetic field alignment process, and an electric field alignment process. The manufacturing method as described.   The manufacturing method according to any one of claims 1 to 4, wherein the liquid crystal composition contains at least one of a liquid crystal monomer and a liquid crystal polymer.   6. The liquid crystal composition according to claim 1, wherein the liquid crystal composition includes a polymerizable monomer and / or a crosslinkable monomer, and the alignment step of the liquid crystal further includes performing a polymerization treatment and / or a crosslinking treatment. Production method.   The manufacturing method according to any one of claims 1 to 6, wherein the negative alignment material is at least one selected from a styrene resin, a (meth) acrylic resin, and a vinyl cinnamate resin.   The manufacturing method according to claim 1, wherein the first birefringent layer is a λ / 2 plate.   The manufacturing method according to claim 1, wherein the second birefringent layer is a λ / 4 plate.   10. The method according to claim 1, further comprising: forming a third birefringent layer having a refractive index distribution of nx = ny> nz on the opposite side of the second birefringent layer from the first birefringent layer. The manufacturing method in any one of.   The optical film manufactured by the manufacturing method in any one of Claim 1-10. An image display device comprising the optical film according to claim 11.

Images