JP2006195424A - Elliptical polarization plate, manufacturing method thereof and image display device using elliptical polarization plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elliptical polarization plate which is extremely thin and has a wide band and a wide viewing field angle, to provide a manufacturing method of the elliptical polarization plate and to provide an image display device using the elliptical polarization plate. <P>SOLUTION: The elliptical polarization plate includes: a polarizer; a protection layer formed on one side of the polarizer; a first doubly refracting layer functioning as a λ/2 plate; and a second doubly refracting layer functioning as a λ/4 plate, wherein the first doubly refracting layer and the second doubly refracting layer are formed by using liquid crystal material. It is preferable that the first doubly refracting layer has a thickness of 0.5 to 5 μm and the second doubly refracting layer has a thickness of 0.3 to 3 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an elliptically polarizing plate, a manufacturing method thereof, and an image display device using the elliptically polarizing plate. More particularly, the present invention relates to an extremely thin, wide-band, wide viewing angle elliptically polarizing plate, a simple manufacturing method thereof, and an image display device using the elliptically polarizing plate.

  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, for example, a norbornene-based film and a modified film as a retardation 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”. 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 °. 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.

Furthermore, in recent years, there has been an increasing demand for thinner image display devices. Along with this, there is an increasing demand for thinner optical discs and other optical films.
Japanese Patent No. 3174367 JP 2003-195037 A

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to use an extremely thin, wide-band, wide-viewing-angle elliptical polarizing plate, a simple manufacturing method thereof, and an elliptical polarizing plate. Another object of the present invention is to provide an image display apparatus.

  As a result of intensive studies on the characteristics of the elliptically polarizing plate, the present inventors applied a liquid crystal material to a specific substrate, transferred the formed birefringent layer, and achieved extremely thin and excellent optical characteristics. It has been found that the above object can be achieved by forming a λ / 4 plate having the present invention, and the present invention has been completed.

  The elliptically polarizing plate of the present invention includes a polarizer, a protective layer formed on one side of the polarizer, a first birefringent layer functioning as a λ / 2 plate, and a second functioning as a λ / 4 plate. A birefringent layer is provided in this order, and the first birefringent layer and the second birefringent layer are formed using a liquid crystal material.

  In a preferred embodiment, the thickness of the first birefringent layer is 0.5 to 5 μm. The thickness of the second birefringent layer is 0.3 to 3 μm.

  In a preferred embodiment, the slow axis of the first birefringent layer defines an angle of + 8 ° to + 38 ° or −8 ° to −38 ° with respect to the absorption axis of the polarizer. In a preferred embodiment, the absorption axis of the polarizer and the slow axis of the second birefringent layer are substantially orthogonal.

  According to another aspect of the present invention, a method for producing an elliptically polarizing plate is provided. This manufacturing method includes a step of performing an alignment treatment on the surface of the transparent protective film (T); a step of forming a first birefringent layer on the surface of the transparent protective film (T) subjected to the alignment treatment; Laminating a polarizer on the surface of the film (T), wherein the polarizer and the first birefringent layer are disposed on opposite sides of each other through the transparent protective film (T), and the first A step of laminating a second birefringent layer on the surface of the birefringent layer.

  In preferable embodiment, the said transparent protective film (T), the said 1st birefringent layer, the said polarizer, and the said 2nd birefringent layer are elongate films, and those long sides are bonded together and laminated | stacked. . In a preferred embodiment, the step of forming the first birefringent layer includes a step of applying a coating liquid containing a liquid crystal material, and the liquid crystal material exhibits a liquid crystal phase. And a step of aligning by processing at a temperature. In a more preferred embodiment, the liquid crystal material includes a polymerizable monomer and / or a crosslinkable monomer, and the alignment step of the liquid crystal material further includes performing a polymerization process and / or a crosslinking process. In a more preferred embodiment, the polymerization treatment and / or crosslinking treatment is performed by heating or light irradiation.

  In a preferred embodiment, the step of laminating the second birefringent layer includes a step of applying a coating liquid containing a liquid crystal material to a substrate, and the liquid crystal material is a liquid crystal. A step of forming a second birefringent layer on the substrate by treatment at a temperature showing a phase; and the surface of the first birefringent layer on the second birefringent layer formed on the substrate. And the step of transferring to. In preferable embodiment, the said base material is a elongate film, and has an orientation axis in the width direction. In a more preferred embodiment, the variation of the orientation axis of the substrate is within ± 1 ° with respect to the average direction of the orientation axis. In a more preferred embodiment, the base material is a polyethylene terephthalate film obtained by performing a stretching treatment and a recrystallization treatment. In preferable embodiment, the said base material is used for the coating process of the said coating liquid, without performing the orientation process with respect to this base material surface.

  According to still another aspect of the present invention, an image display device is provided. This image display device includes the elliptically polarizing plate.

  As described above, according to the present invention, the first birefringent layer and the second birefringent layer are formed of a liquid crystal material, and nx and ny are compared with the case where they are formed of a polymer stretched film. The difference can be greatly increased. As a result, the thickness capable of obtaining a desired in-plane retardation for functioning the first birefringent layer as a λ / 2 plate can be remarkably reduced as compared with the prior art, and the second birefringent layer can be obtained. The thickness at which a desired in-plane retardation for functioning as a λ / 4 plate can be obtained can be made much thinner than in the past. Therefore, the elliptically polarizing plate of the present invention is much thinner than the conventional elliptically polarizing plate, and can greatly contribute to the thinning of the image display device. In addition, the elliptically polarizing plate of the present invention has an alignment fixed by polymerizing or cross-linking the liquid crystal materials of the first birefringent layer and the second birefringent layer. Excellent heat resistance. As a result, it has a special effect that the optical characteristics do not deteriorate even in a high temperature environment (for example, in-vehicle use).

A. Elliptical polarizing plate A-1. 1 is a schematic sectional view of an elliptically polarizing plate according to a preferred embodiment of the present invention. FIG. 2 is an exploded perspective view for explaining the optical axis of each layer constituting the elliptically polarizing plate of FIG. As shown in FIG. 1, the elliptically polarizing plate 10 includes a polarizer 11, a protective layer (transparent protective film) 12, a first birefringent layer (optical compensation layer) 13, and a second birefringent layer (optical compensation layer). 14). Practically, the elliptically polarizing plate of the present invention may have a second protective layer (transparent protective film) 15 on the side where the protective layer (transparent protective film) 12 of the polarizer is not laminated.

  The first birefringent layer 13 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 14 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 elliptically polarizing plate according to a preferred embodiment of the present invention (in FIG. 2, the second protective layer 15 is omitted for the sake of clarity). ing). The first birefringent layer 13 is laminated so that the slow axis B defines a predetermined angle α with respect to the absorption axis A of the polarizer 11. The angle α is preferably + 8 ° to + 38 ° or −8 ° to −38 °, more preferably + 13 ° to + 33 ° or −13 ° to −33 °, and particularly preferably + 19 ° to + 29 °. It is −19 ° to −29 °, particularly preferably + 21 ° to + 27 ° or −21 ° to −27 °, and most preferably + 23 ° to + 24 ° or −23 ° to −24 °. By laminating the first birefringent layer and the polarizer so as to form such an angle α, a polarizing plate having very excellent circular polarization characteristics can be obtained. Further, as shown in FIG. 2, the second birefringent layer 14 is laminated so that the slow axis C thereof is substantially perpendicular to the absorption axis A of the polarizer 11. In the present specification, “substantially orthogonal” includes a case of 90 ° ± 2.0 °, preferably 90 ° ± 1.0 °, more preferably 90 ° ± 0.5 °. It is.

  The total thickness of the elliptically polarizing plate of the present invention is preferably 80 to 200 μm, more preferably 90 to 130 μm, and most preferably 100 to 120 μm. According to the present invention, by forming the first birefringent layer and the second birefringent layer from a liquid crystal material (described later), the thickness for allowing the first birefringent layer to function as a λ / 2 plate is conventionally increased. The thickness for making the second birefringent layer function as a λ / 4 plate can be made much thinner than in the prior art. As a result, the elliptically polarizing plate of the present invention can be made as thin as about a quarter of the total thickness as compared with the conventional elliptically polarizing plate, and can greatly contribute to the thinning of the liquid crystal display device. Hereinafter, details of each layer constituting the elliptically polarizing plate of the present invention will be described.

A-2. First Birefringent Layer As described above, the first birefringent layer 13 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 185 to 305 nm, more preferably 205 to 285 nm, and most preferably 220 to 270 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 in which the in-plane refractive index is maximum (that is, the slow axis direction), and ny is the refractive index in the direction perpendicular to the slow axis in the plane. d is the thickness of the first birefringent layer. Further, the first birefringent layer 13 preferably has a refractive index distribution of nx> ny = nz. In this 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. In the present specification, “substantially equal” is intended to include the case where nx and ny are different within a range that does not practically affect the overall polarization characteristics of the elliptically polarizing plate.

  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. 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.

  When the liquid crystal material is a liquid crystal monomer, for example, a polymerizable monomer or a crosslinkable monomer is preferable. This is because the alignment state of the liquid crystal material can be fixed by polymerizing or crosslinking a polymerizable monomer or a crosslinkable monomer, as will be described later. After aligning the liquid crystal monomer, for example, if the liquid crystal monomers (polymerizable monomer or crosslinkable monomer) are polymerized or cross-linked, 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 is extremely stable.

  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 14 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 the second birefringent layer is preferably 60 to 180 nm, more preferably 80 to 160 nm, and most preferably 100 to 140 nm at a wavelength of 590 nm. Further, the second birefringent layer 14 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 0.3 to 3 μm, more preferably 0.5 to 2.5 μm, and most preferably 0.8 to 2 μm. The realization of such a very thin second birefringent layer (λ / 4 plate) is one of the features of the present invention. For example, the thickness of a λ / 4 plate by a conventional stretched film is about 60 μm, whereas the elliptical polarizing plate of the present invention has a λ / 4 plate having a thickness of about 1/20 to 1/200. (Second birefringent layer) can be realized.

  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 preferred. Since the difference between nx and ny can be significantly increased compared to conventional polymer stretched films (for example, norbornene-based resins and polycarbonate resins), the thickness for obtaining the in-plane retardation desired for the λ / 4 plate is greatly increased. This is because it can be made thinner. As the liquid crystal material, the same material as that used for the first birefringent layer can be used. The details of the liquid crystal material are as described in the above section A-2.

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 protective layer 12 and the 2nd protective layer 15 consist of arbitrary appropriate films which can be used as a protective film of a polarizing plate. A transparent protective film is preferred. 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, and TAC is more preferable.

  The protective layer is preferably transparent and has no color. Specifically, the thickness direction retardation value Rth is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and most preferably −70 nm to +70 nm. The thickness direction retardation Rth is obtained by the formula: Rth = {(nx + ny) / 2−nz} × d, where d (nm) is the thickness of the film (layer).

  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 15 opposite to the polarizer (that is, the outermost part of the elliptically polarizing plate) is subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, an antiglare treatment, etc. as necessary. obtain.

B. Manufacturing method of elliptically polarizing plate The manufacturing method of the elliptically polarizing plate in a preferred embodiment of the present invention includes a step of performing an alignment treatment on the surface of the transparent protective film (T); and the alignment treatment of the transparent protective film (T). Forming a first birefringent layer on the surface; and laminating a polarizer on the surface of the transparent protective film (T), wherein the polarizer and the first birefringent layer are transparent to each other. A step of laminating a second birefringent layer on the surface of the first birefringent layer, disposed on the opposite side via (T). According to such a manufacturing method, for example, an elliptically polarizing plate as shown in FIGS. 1 and 2 is obtained. The order of the above steps and / or the film subjected to the orientation treatment can be appropriately changed depending on the purpose. For example, the polarizer lamination step may be performed after any birefringent layer forming step or lamination step. Further, for example, the orientation treatment may be applied to the transparent protective film or may be applied to any appropriate base material. When the substrate is subjected to orientation treatment, the film (specifically, the first birefringent layer) formed on the substrate is in an appropriate order according to the desired laminated structure of the elliptically polarizing plate. It can be transferred (laminated). Details of each step will be described below.

B-1. By subjecting the surface of the transparent protective film (T) (which will eventually become the protective layer 12) to an orientation treatment and coating the surface with a coating liquid containing a predetermined liquid crystal material, 2, the first birefringent layer 13 having the slow axis B that forms an angle α with respect to the absorption axis of the polarizer 11 can be formed (step of forming the first birefringent layer). Will be described later).

  Arbitrary appropriate orientation processing may be employ | adopted as orientation processing to the said transparent protective film (T). Specific examples include rubbing, oblique vapor deposition, stretching, photo-alignment, magnetic field alignment, and electric field alignment. A rubbing process is preferred. In addition, arbitrary appropriate conditions may be employ | adopted for the process conditions of various orientation processes according to the objective.

  The orientation direction of the orientation treatment is a direction that forms a predetermined angle with the absorption axis of the polarizer when the transparent protective film (T) and the polarizer are laminated. As will be described later, this orientation direction is substantially the same as the direction of the slow axis B of the first birefringent layer 13 to be formed. Therefore, the predetermined angle is preferably + 8 ° to + 38 ° or −8 ° to −38 °, more preferably + 13 ° to + 33 ° or −13 ° to −33 °, and particularly preferably + 19 °. ~ + 29 ° or -19 ° to -29 °, particularly preferably + 21 ° to + 27 ° or -21 ° to -27 °, most preferably + 23 ° to + 24 ° or -23 ° to -24 °. is there.

  As the orientation treatment capable of defining the predetermined angle as described above with respect to the long transparent protective film (T), the treatment is performed in the longitudinal direction of the long transparent protective film (T), and the long length The transparent protective film (T) may be treated in a diagonal direction (specifically, a direction that defines a predetermined angle as described above) with respect to the longitudinal direction or the vertical direction (width direction) of the transparent protective film (T). The polarizer is produced by stretching a polymer film dyed with a dichroic substance as described above, and has an absorption axis in the stretching direction. And when mass-producing a polarizer, the elongate polymer film is prepared and the extending | stretching is performed continuously in the longitudinal direction. Therefore, when bonding a long polarizer and a long transparent protective film (T), the longitudinal direction of both becomes the absorption axis of the polarizer. For this reason, in order to align in a direction which makes a predetermined angle with respect to the absorption axis of the polarizer, it is desirable to perform an alignment process in an oblique direction. Since the direction of the absorption axis of the polarizer and the longitudinal direction of the long film (polarizer and transparent protective film (T)) substantially coincide, the direction of the orientation treatment makes the predetermined angle with respect to the longitudinal direction. Just go in the direction. On the other hand, when processing in the longitudinal direction or the width direction of a transparent protective film, it is necessary to laminate | stack, after cutting out a transparent protective film in the diagonal direction. As a result, there may be variations in the angle of the optical axis in each cut out film, resulting in variations in quality between products, cost and time, increasing waste, making it difficult to manufacture large films It becomes.

  The alignment treatment may be performed directly on the surface of the transparent protective film (T), or any suitable alignment layer (typically, a polyimide layer or a polyvinyl alcohol layer) may be formed and applied to the alignment layer.

B-2. Step of coating liquid crystal material for forming first birefringent layer Next, a coating liquid containing the liquid crystal material as described in the above section A-2 on the surface of the transparent protective film (T) subjected to the alignment treatment. And then the liquid crystal material is oriented to form a first birefringent layer. Specifically, a coating solution in which a liquid crystal material is dissolved or dispersed in an appropriate solvent is prepared, and this coating solution may be applied to the surface of the transparent protective film (T) that has been subjected to the alignment treatment. The alignment process of the liquid crystal material will be described in the section B-3 below.

  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 (polymerizable monomer or crosslinkable 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 per area (100 cm ² ) of the transparent protective film (T). 0.05 to 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-3. Step of Aligning Liquid Crystal Material Forming First Birefringent Layer Next, the liquid crystal material forming the first birefringent layer is aligned according to the alignment direction of the surface of the transparent protective film (T). 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 transparent protective film (T). Thereby, birefringence is generated in the layer formed by coating, and the first 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.

  Further, when the liquid crystal monomer (polymerizable monomer and crosslinkable monomer) described in the above section A-2 is used as the liquid crystal material, the layer formed by the coating is further subjected to polymerization treatment or crosslinking treatment. It is preferable. 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 crosslinking the liquid crystal monomer is “non-liquid crystalline”. Therefore, in the formed first birefringent layer, for example, transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change specific to liquid crystal molecules does not occur. As a result, it is possible to obtain a first birefringent layer having very excellent stability that is not affected by temperature.

  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 to be used. For example, when a photopolymerization initiator or a photocrosslinking agent is used, light irradiation may be performed, and when an ultraviolet polymerization initiator or an ultraviolet crosslinking agent is used, ultraviolet irradiation may be performed. When a cross-linking agent is used, heating may be performed. Light or ultraviolet irradiation time, irradiation intensity, total irradiation amount, etc. depend on the type of liquid crystal material, the type of transparent protective film (T), the type of alignment treatment, the characteristics desired for the first birefringent layer, etc. Can be set appropriately. Similarly, the heating temperature, the heating time, and the like can be set as appropriate.

  By performing the alignment treatment as described above, the liquid crystal material is aligned in accordance with the alignment direction of the transparent protective film (T), so that the slow axis B of the formed first birefringent layer is the transparent protective film. It becomes substantially the same as the orientation direction of the film (T). Therefore, the direction of the slow axis B of the first birefringent layer is preferably + 8 ° to + 38 ° or −8 ° to −38 °, more preferably +13, with respect to the longitudinal direction of the transparent protective film (T). ° to + 33 ° or -13 ° to -33 °, particularly preferably + 19 ° to + 29 ° or -19 ° to -29 °, particularly preferably + 21 ° to + 27 ° or -21 ° to -27 °, most preferably + 23 ° to + 24 ° or −23 ° to −24 °.

B-4. Lamination process of a polarizer A polarizer is laminated | stacked on the surface of the said transparent protective film (T). 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, the polarizer may be laminated in advance on the transparent protective film (T), may be laminated after forming the first birefringent layer, or may be laminated after forming the second birefringent layer. Also good.

  Any appropriate laminating method (for example, adhesion) can be adopted as a laminating method of the transparent protective film (T) 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 (T) 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 30 to 180 nm, and most preferably 50 to 150 nm.

  According to the production method of the present invention, the slow axis of the first birefringent layer can be set in the orientation treatment of the transparent protective film (T), so that it is stretched in the longitudinal direction (that is, the absorption axis in the longitudinal direction). A long polarizing film (polarizer) can be used. That is, a long transparent protective film (T) that has been subjected to an orientation treatment so as to form a predetermined angle with respect to the longitudinal direction and a long polarizing film (polarizer) are aligned in the longitudinal direction (so-called Can be bonded continuously (roll to roll). Therefore, an elliptically polarizing plate 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 elliptically polarizing plate with no quality variation among products is obtained. Furthermore, no waste due to clipping is generated, so that an elliptically polarizing plate can be obtained at low cost. In addition, a large polarizing plate can be easily manufactured.

  The direction of the absorption axis of the polarizer is substantially parallel to the longitudinal direction of the long film. In the present specification, “substantially parallel” means that the angle between the longitudinal direction and the absorption axis direction includes 0 ° ± 10 °, preferably 0 ° ± 5 °, more preferably 0 °. ± 3 °.

B-5. Step of Laminating Second Birefringent Layer Furthermore, a second birefringent layer is laminated on the surface of the first birefringent layer. The detailed procedure of the lamination process of the second birefringent layer is as follows. First, a coating liquid containing a liquid crystal material that forms the second birefringent layer is applied to a substrate, and the liquid crystal material is aligned on the substrate. 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 substrate surface. As a result, birefringence occurs in the layer formed by coating, and a second birefringent layer is formed. Details of the coating of the coating liquid and the alignment treatment of the liquid crystal material are as described in the above sections B-2 and B-3. However, since the thickness of the second birefringent layer is about half that of the first birefringent layer, the coating amount is also about half. Specifically, the coating amount is preferably 0.02 to 0.08 ml, more preferably 0.03 to 0.07 ml, and most preferably 0.04 per area (100 cm ² ) of the base material. ~ 0.06 ml.

  As the base material, any appropriate base material is used as long as the appropriate second birefringent layer in the present invention is obtained. Preferably, the base material is a polyethylene terephthalate (PET) film obtained by performing a stretching process and a recrystallization process. More specifically, a base material is obtained by extrusion film-molding a PET resin, stretching, and then recrystallization. The stretching method is preferably lateral uniaxial stretching or longitudinal / lateral biaxial stretching. In longitudinal and transverse biaxial stretching, it is preferable to make the stretching ratio in the transverse direction larger than the stretching ratio in the longitudinal direction. By such a method, a substrate having an alignment axis in the width direction can be obtained. The substrate may be stretched after forming a polyimide layer or a polyvinyl alcohol layer. The stretching temperature is preferably 120 to 160 ° C. The draw ratio is preferably 2 to 7 times. The stretching direction can be set according to the direction of the slow axis desired for the second birefringent layer. In the present invention, the slow axis of the first birefringent layer can be set to an arbitrary oblique direction with respect to the absorption axis of the polarizer (the longitudinal direction of the long film). Here, when the slow axis of the first birefringent layer is set in the direction of 23 ° to 24 ° with respect to the absorption axis of the polarizer, the slow axis of the second birefringent layer is substantially the same as the absorption axis of the polarizer. It has been found that it is sufficient to make them orthogonal. The direction of the slow axis corresponds to the orientation axis direction of the substrate (the direction in which the liquid crystal material constituting the second birefringent layer is oriented), and the orientation axis direction corresponds to the stretching direction. May be performed in the lateral direction (width direction: direction orthogonal to the longitudinal direction: direction orthogonal to the absorption axis of the polarizer). As a result, it is not necessary to punch in order to match the direction of the slow axis of the second birefringent layer, and bonding by roll-to-roll becomes possible, and manufacturing efficiency is further improved. The recrystallization temperature is preferably 150 to 250 ° C. By performing recrystallization in such a temperature range, the direction of the PET molecules becomes more uniform, and a substrate with extremely small variation in the orientation axis can be obtained. The thickness of a base material becomes like this. Preferably it is 20-100 micrometers, More preferably, it is 30-90 micrometers, Most preferably, it is 30-80 micrometers. 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.

  As described above, by performing a combination of the specific stretching process and the recrystallization process, a substrate with extremely small variation in the orientation axis can be obtained. Specifically, the variation of the orientation axis of the obtained base material is preferably within ± 1 ° with respect to the average direction of the orientation axis, and more preferably within ± 0.5 °. By using such a substrate, when applying a liquid crystal material, an alignment treatment (for example, rubbing treatment, oblique vapor deposition method, stretching treatment, photo-alignment treatment, magnetic field alignment treatment, electric field alignment treatment) ) May be omitted. As a result, it is possible to produce a very thin elliptically polarizing plate with extremely excellent production efficiency. One of the major features of the present invention is that the second birefringent layer is formed using a base material that can omit the alignment treatment. Such base materials are available from Toray Industries, Inc. and Mitsubishi Polyester Corporation.

  Next, the second birefringent layer formed on the substrate 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 to the first birefringent layer via an adhesive. 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. Further, since it is not necessary to heat for curing, the first and second birefringent layers are not heated during bonding (adhesion). As a result, since there is no concern about heat shrinkage, even when the first and second birefringent layers 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 2 ml per area (cm ² ) of the first or second birefringent layer. It is. After coating, if necessary, the solvent contained in the adhesive is volatilized by natural drying or heat drying. 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 is peeled from the second birefringent layer, the lamination of the first birefringent layer and the second birefringent layer is completed. In this way, the elliptically polarizing plate of the present invention is obtained.

B-6. 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 7, reference numerals 111, 111 ′, 112, 112 ′ 115, and 116 are rolls for winding the film and / or the laminated body forming 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 a long polymer film. Thus, as shown in the perspective view of FIG. 3, a long polarizer 11 having an absorption axis in the longitudinal direction (stretching direction: arrow A direction) is obtained.

  On the other hand, as shown in the perspective view of FIG. 4A, a long transparent protective film 12 (which will eventually become the first protective layer) is prepared, and one surface thereof is rubbed by a rubbing roll 120. I do. At this time, the rubbing direction is different from the longitudinal direction of the transparent protective film 12, for example, + 23 ° to + 24 ° or −23 ° to −24 °. Next, as shown in the perspective view of FIG. 4B, the first birefringent layer 13 is formed on the transparent protective film 12 subjected to the rubbing treatment as described in the paragraphs B-2 and B-3. Form. In the first birefringent layer 13, the liquid crystal material is aligned along the rubbing direction, so that the slow axis direction is substantially the same direction (arrow B direction) as the rubbing direction of the transparent protective film 12.

  Next, as shown in the schematic diagram of FIG. 5, a transparent protective film (being a second protective layer) 15, a polarizer 11, a transparent protective film (being a protective layer) 12 and a first birefringent layer 13. The laminated body 121 is sent out in the direction of the arrow, and bonded together with an adhesive or the like (not shown) in a state where the respective longitudinal directions are aligned. In addition, in FIG. 5, the code | symbol 122 shows the guide roll for bonding films together (same also in FIG. 6 and FIG. 7).

  Furthermore, as shown in the schematic diagram of FIG. 6A, a long laminated body 125 (the one in which the second birefringent layer 14 is supported on the base material 26) is prepared, and this is laminated with the laminated body 123 (first 2 protective layers (transparent protective film) 15, polarizer 11, protective layer (transparent protective film) 12 and first birefringent layer 13) are sent out in the direction of the arrows, and bonded in a state where their respective longitudinal directions are aligned. Bonding with an agent or the like (not shown). As described above, the direction (angle α) of the slow axis of the first birefringent layer 13 is + 23 ° to + 24 ° or −23 ° to −24 with respect to the longitudinal direction of the film (absorption axis of the polarizer 11). If set to °, the slow axis of the second birefringent layer 14 may be substantially orthogonal to the longitudinal direction of the film (absorption axis of the polarizer 11). By doing in this way, the very thin 1st and 2nd birefringent layer can be bonded together by a roll to roll, and manufacturing efficiency can be improved markedly.

  Finally, as shown in FIG. 6B, the base material 26 is peeled off to obtain the elliptically polarizing plate 10 of the present invention.

  Another example of the specific procedure of the production method of the present invention will be described.

  Similarly to the above, as shown in the perspective view of FIG. 3, a long polarizer 11 is manufactured.

  On the other hand, as shown in the perspective view of FIG. 4A, a long transparent protective film 12 (which will eventually become the first protective layer) is prepared, and one surface thereof is rubbed by a rubbing roll 120. I do. At this time, the rubbing direction is different from the longitudinal direction of the transparent protective film 12, for example, + 23 ° to + 24 ° or −23 ° to −24 °.

  Next, as shown in the schematic diagram of FIG. 7, the second transparent protective film 15 (which becomes the second protective layer), the polarizer 11 and the transparent protective film 12 (which becomes the protective layer) are sent out in the direction of the arrow. Then, they are bonded together with an adhesive or the like (not shown) in a state where the respective longitudinal directions are aligned. At this time, the transparent protective film 12 that has been subjected to the rubbing process is sent out so that the side opposite to the surface that has been subjected to the rubbing process faces the polarizer 11. As a result, a laminate 126 of the second protective layer (transparent protective film) 15 / polarizer 11 / protective layer (transparent protective film) 12 is obtained.

  Next, the first birefringent layer 13 is formed on the surface of the protective layer (transparent protective film) 12 that has been subjected to the rubbing treatment as described in the paragraphs B-2 and B-3 (not shown). In the first birefringent layer 13, since the liquid crystal material is aligned along the rubbing direction, the slow axis direction is substantially the same as the rubbing direction of the protective layer (transparent protective film) 12. As a result, a laminate 123 of the second protective layer (transparent protective film) 15 / polarizer 11 / protective layer (transparent protective film) 12 / first birefringent layer 13 is obtained.

  Furthermore, as shown in the schematic diagram of FIG. 6A, a long laminated body 125 (the one in which the second birefringent layer 14 is supported on the base material 26) is prepared, and this is laminated with the laminated body 123 (first 2 protective layers (transparent protective film) 15, polarizer 11, protective layer (transparent protective film) 12 and first birefringent layer 13) are sent out in the direction of the arrows, and bonded in a state where their respective longitudinal directions are aligned. Bonding with an agent or the like (not shown). As described above, the direction (angle α) of the slow axis of the first birefringent layer 13 is + 23 ° to + 24 ° or −23 ° to −24 with respect to the longitudinal direction of the film (absorption axis of the polarizer 11). If set to °, the slow axis of the second birefringent layer 14 may be substantially orthogonal to the longitudinal direction of the film (absorption axis of the polarizer 11).

  Finally, as shown in FIG. 6B, the base material 26 is peeled off to obtain the elliptically polarizing plate 10 of the present invention.

    Another example of the specific procedure of the production method of the present invention will be described.

  Similarly to the above, as shown in the perspective view of FIG. 3, a long polarizer 11 is manufactured.

  Next, as shown in the schematic diagram of FIG. 7, the second transparent protective film 15 (which becomes the second protective layer), the polarizer 11 and the transparent protective film 12 (which becomes the protective layer) are sent out in the direction of the arrow. Then, they are bonded together with an adhesive or the like (not shown) in a state where the respective longitudinal directions are aligned. As a result, a laminate 126 of the second protective layer (transparent protective film) 15 / polarizer 11 / protective layer (transparent protective film) 12 is obtained.

  Next, in the same manner as described above, a rubbing treatment is performed on the surface of one of the transparent protective films 12 (on the side opposite to the polarizer 11) with a rubbing roll (not shown). At this time, the rubbing direction is different from the longitudinal direction of the transparent protective film 12, for example, + 23 ° to + 24 ° or −23 ° to −24 °.

  Next, the first birefringent layer 13 is formed on the surface of the protective layer (transparent protective film) 12 that has been subjected to the rubbing treatment as described in the paragraphs B-2 and B-3 (not shown). In the first birefringent layer 13, since the liquid crystal material is aligned along the rubbing direction, the slow axis direction is substantially the same as the rubbing direction of the protective layer (transparent protective film) 12. As a result, a laminate 123 of the second protective layer (transparent protective film) 15 / polarizer 11 / protective layer (transparent protective film) 12 / first birefringent layer 13 is obtained.

  Furthermore, as shown in the schematic diagram of FIG. 6A, a long laminated body 125 (the one in which the second birefringent layer 14 is supported on the base material 26) is prepared, and this is laminated with the laminated body 123 (first 2 protective layers (transparent protective film) 15, polarizer 11, protective layer (transparent protective film) 12 and first birefringent layer 13) are sent out in the direction of the arrows, and bonded in a state where their respective longitudinal directions are aligned. Bonding with an agent or the like (not shown). As described above, the direction (angle α) of the slow axis of the first birefringent layer 13 is + 23 ° to + 24 ° or −23 ° to −24 with respect to the longitudinal direction of the film (absorption axis of the polarizer 11). If set to °, the slow axis of the second birefringent layer 14 may be substantially orthogonal to the longitudinal direction of the film (absorption axis of the polarizer 11).

  Finally, as shown in FIG. 6B, the base material 26 is peeled off to obtain the elliptically polarizing plate 10 of the present invention.

B-7. Other components of the elliptically polarizing plate The elliptically polarizing plate 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 another birefringent layer (retardation film), a liquid crystal film, a light scattering film, a diffraction film, and the like.

  The elliptically polarizing plate 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 another member (for example, a liquid crystal cell) becomes easy, and peeling from the other member of the elliptically polarizing plate can be prevented. Any appropriate material can be adopted as the material of the pressure-sensitive adhesive layer. Specific examples of the adhesive include those described in the above section B-4. 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 is covered with any appropriate separator until the elliptically polarizing plate is actually used, and contamination can be prevented. 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 elliptically polarizing plate of the present invention imparts ultraviolet absorbing ability by, for example, 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 what you did.

C. Use of elliptically polarizing plate The elliptically polarizing plate of the present invention can be suitably used for various image display devices (for example, liquid crystal display devices and 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 elliptically polarizing plate of the present invention is used in a liquid crystal display device, it is useful for viewing angle compensation, for example. The elliptically polarizing plate of the present invention is used in, for example, a circular polarization mode liquid crystal display device, such as a homogeneous alignment type TN liquid crystal display device, a horizontal electrode type (IPS) type liquid crystal display device, and a vertical alignment (VA) type liquid crystal display device. Is particularly useful. Moreover, when using the elliptically polarizing plate 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. 8 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 elliptically polarizing plate of the present invention described in the A and B terms. This polarizing plate (elliptical polarizing plate) 10 is arranged so that the birefringent layers 13 and 14 are between the polarizer 11 and the liquid crystal cell 20. The polarizing plate 10 ′ is any appropriate polarizing plate (preferably the elliptically polarizing plate of the present invention described in the above A and B terms). The polarizing plates 10, 10 ′ are typically arranged so that their absorption axes are orthogonal to each other. As shown in FIG. 8, in the liquid crystal display device (liquid crystal panel) of the present invention, the elliptically polarizing plate 10 of the present invention is preferably disposed 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 and 21 ′ in contact with the liquid crystal layer 22.

  For example, a display mechanism in the VA mode will be described. FIG. 9 is a schematic cross-sectional view illustrating the alignment state of liquid crystal molecules in the VA mode. As shown in FIG. 9A, when no voltage is applied, the liquid crystal molecules are aligned perpendicular to the surfaces of the substrates 21 and 21 '. Such vertical alignment can be realized by arranging a nematic liquid crystal having negative dielectric anisotropy between substrates on which a vertical alignment film (not shown) is formed. In this state, when linearly polarized light that has passed through the polarizing plate 10 ′ is incident on the liquid crystal layer 22 from the surface of the one substrate 21 ′, the incident light is in the direction of the major axis of the vertically aligned liquid crystal molecules. Proceed along. Since birefringence does not occur in the major axis direction of the liquid crystal molecules, incident light travels without changing the polarization direction and is absorbed by the polarizing plate 10 having a polarizing axis perpendicular to the polarizing plate 10 '. This provides a dark display when no voltage is applied (normally black mode). As shown in FIG. 9B, when a voltage is applied between the electrodes, the long axes of the liquid crystal molecules are aligned parallel to the substrate surface. Liquid crystal molecules exhibit birefringence with respect to linearly polarized light incident on the liquid crystal layer 22 in this state, and the polarization state of incident light changes according to the inclination of the liquid crystal molecules. The light passing through the liquid crystal layer 22 when a predetermined maximum voltage is applied becomes, for example, linearly polarized light whose polarization direction is rotated by 90 °, so that the light is transmitted through the polarizing plate 10 and a bright display is obtained. When the voltage is not applied again, the display can be returned to the dark state by the orientation regulating force. Further, gradation display is possible by changing the intensity of transmitted light from the polarizing plate 10 by changing the applied voltage to control the inclination of the liquid crystal molecules.

  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 KOBRA31PR), and in-plane retardation Δnd and thickness direction are measured. 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 and second birefringent layers 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 of transmittance The same elliptically polarizing plates obtained in Example 1 were bonded together. The transmittance of the bonded sample was measured by a trade name DOT-3 (Murakami Color Co., Ltd.).
(4) Measurement of contrast ratio The same elliptical polarizing plates are overlapped and illuminated with a backlight to display a white image (absorption axes of polarizers are parallel) and a black image (absorption axes of polarizers are orthogonal), manufactured by ELDIM The product name “EZ Contrast 160D” was scanned in the direction of 45 ° to 135 ° with respect to the absorption axis of the polarizer on the viewing side and from −60 ° to 60 ° with respect to the normal. Then, the contrast ratio “YW / YB” in the oblique direction was calculated from the Y value (YW) in the white image and the Y value (YB) in the black image.

I. Alignment treatment of transparent protective film (production of alignment substrate)
The transparent protective film was subjected to an alignment treatment to produce an alignment substrate (which eventually becomes the protective layer 12).
Substrates (1) to (8): After forming a PVA film (thickness 0.1 μm) on the surface of the TAC film (thickness 40 μm), the rubbing cloth is used to apply the rubbing angle shown in the table below to the PVA film surface. By rubbing, an alignment substrate was prepared.
Base materials (9) to (10): A TAC film (thickness: 40 μm) was rubbed at a rubbing angle shown in the following table using a rubbing cloth to prepare an alignment base material.
Substrates (11) to (12): After applying a silane coupling agent (trade name KBM-503: manufactured by Shin-Etsu Silicone Co., Ltd.) to the surface of the TAC film (thickness 40 μm), the surface is subjected to the following using a rubbing cloth. Rubbing was carried out at the rubbing angle shown in the table to prepare an alignment substrate.
Substrates (13) to (14): After a PVA film (thickness 0.1 μm) is formed on the surface of a TAC film (thickness 40 μm), the surface of the PVA film is applied at a rubbing angle shown in the following table using a rubbing cloth. By rubbing, an alignment substrate was prepared. The retardation in the thickness direction of the protective layer is also shown in the table below.

II. Preparation of first birefringent layer First, 10 g of a polymerizable liquid crystal (liquid crystal monomer) exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242) and a photopolymerization initiator for the polymerizable liquid crystal compound (Ciba Specialty Chemicals) Product: Irgacure 907) 3 g was dissolved in 40 g of toluene to prepare a liquid crystal coating solution. And after apply | coating the said liquid-crystal 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 is irradiated with light of 1 mJ / cm ² using a metal halide lamp, the polymerizable liquid crystal of the liquid crystal is polymerized, and the orientation of the liquid crystal layer is fixed. (3) was formed. The thickness and retardation of the first birefringent layer were adjusted by changing the coating amount of the liquid crystal coating liquid. The following table shows the thickness and in-plane retardation value (nm) of the formed first birefringent layer.

III. Preparation of second birefringent layer III-a. Preparation of substrate A polyethylene terephthalate roll (width 4 m) having an orientation axis in the width direction and having a variation of the orientation axis within ± 1 ° with respect to the average direction of the orientation axis was prepared.

III-b. Formation of second birefringent layer In the same manner as described in II above, second birefringent layers (21) to (23) were formed. The thickness and retardation of the second birefringent layer were adjusted by changing the coating amount of the liquid crystal coating solution. The following table shows the thickness and in-plane retardation value (nm) of the formed second birefringent layer.

IV. Preparation of Elliptical Polarizing Plate A polyvinyl alcohol film was dyed in an aqueous solution containing iodine, and then uniaxially stretched 6 times between rolls having different speed ratios in an aqueous solution containing boric acid to obtain a polarizer. A protective layer, a first birefringent layer, and a second birefringent layer were used in combinations as shown in the following table. The polarizer, the protective layer, the first birefringent layer, and the second birefringent layer are laminated by the manufacturing procedure shown in FIGS. 3 to 7 to obtain elliptically polarizing plates A01 to A18 as shown in FIG. It was.

  The contrast ratio was measured by overlapping the elliptically polarizing plates A03. According to this elliptically polarizing plate, the angle of contrast 10 is 40 degrees minimum, 50 degrees maximum in all directions, and the maximum minimum difference is 10 degrees. It was a practically preferable level that the angle of the contrast 10 was a minimum of 40 degrees in all directions. Furthermore, since the difference between the maximum and minimum is as small as 10 degrees, the visual characteristics are well balanced, which is also a very favorable level for practical use.

  The contrast ratio was measured by superimposing the elliptical polarizing plates A09. According to this elliptically polarizing plate, the angle of contrast 10 was 40 degrees minimum, 60 degrees maximum in all directions, and the maximum minimum difference was 20 degrees. It was a practically preferable level that the angle of the contrast 10 was a minimum of 40 degrees in all directions.

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

1 is a schematic cross-sectional view of an elliptically polarizing plate according to a preferred embodiment of the present invention. 1 is an exploded perspective view of an elliptically polarizing plate 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 elliptically polarizing plate of this invention. It is a perspective view which shows the outline of another process in an example of the manufacturing method of the elliptically polarizing plate of this invention. It is a schematic diagram which shows the outline of another process in an example of the manufacturing method of the elliptically polarizing plate of this invention. It is a schematic diagram which shows the outline of another process in an example of the manufacturing method of the elliptically polarizing plate of this invention. It is a schematic diagram which shows the outline of another process in an example of the manufacturing method of the elliptically polarizing plate 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. It is a schematic sectional drawing explaining the orientation state of the liquid crystal molecule in VA mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Elliptical polarizing plate 11 Polarizer 12 Protective layer 13 1st birefringent layer 14 2nd birefringent layer 15 2nd protective layer 20 Liquid crystal cell 100 Liquid crystal panel

Claims (16)

  A polarizer; a protective layer formed on one side of the polarizer; a first birefringent layer that functions as a λ / 2 plate; and a second birefringent layer that functions as a λ / 4 plate in this order. An elliptically polarizing plate in which the first birefringent layer and the second birefringent layer are formed using a liquid crystal material.   The elliptically polarizing plate according to claim 1, wherein the first birefringent layer has a thickness of 0.5 to 5 μm.   The elliptically polarizing plate according to claim 1 or 2, wherein the thickness of the second birefringent layer is 0.3 to 3 µm.   The slow axis of the first birefringent layer defines an angle of + 8 ° to + 38 ° or -8 ° to -38 ° with respect to the absorption axis of the polarizer. The elliptically polarizing plate described in 1.   The elliptically polarizing plate according to claim 1, wherein an absorption axis of the polarizer and a slow axis of the second birefringent layer are substantially orthogonal to each other. Applying an alignment treatment to the surface of the transparent protective film (T);
Forming a first birefringent layer on the surface of the transparent protective film (T) subjected to the orientation treatment;
Laminating a polarizer on the surface of the transparent protective film (T),
The polarizer and the first birefringent layer are disposed on opposite sides of each other via a transparent protective film (T),
A method for producing an elliptically polarizing plate, comprising a step of laminating a second birefringent layer on the surface of the first birefringent layer.   The said transparent protective film (T), a said 1st birefringent layer, the said polarizer, and a said 2nd birefringent layer are elongate films, the long sides are bonded together and laminated | stacked. Manufacturing method.   The step of forming the first birefringent layer includes a step of applying a coating liquid containing a liquid crystal material, and the applied liquid crystal material is processed and aligned at a temperature at which the liquid crystal material exhibits a liquid crystal phase. The manufacturing method of Claim 6 or 7 including the process to make.   The manufacturing method according to claim 8, wherein the liquid crystal material includes a polymerizable monomer and / or a crosslinkable monomer, and the alignment step of the liquid crystal material further includes performing a polymerization treatment and / or a crosslinking treatment.   The production method according to claim 9, wherein the polymerization treatment and / or crosslinking treatment is performed by heating or light irradiation.   The step of laminating the second birefringent layer includes a step of applying a coating liquid containing a liquid crystal material to a substrate, and the applied liquid crystal material is processed at a temperature at which the liquid crystal material exhibits a liquid crystal phase. Forming a second birefringent layer on the substrate, and transferring the second birefringent layer formed on the substrate to the surface of the first birefringent layer. The manufacturing method in any one of Claim 6 to 10 containing.   The manufacturing method according to claim 11, wherein the substrate is a long film and has an orientation axis in a width direction thereof.   The manufacturing method according to claim 11 or 12, wherein the variation of the orientation axis of the substrate is within ± 1 ° with respect to the average direction of the orientation axis.   The manufacturing method in any one of Claim 11 to 13 whose said base material is a polyethylene terephthalate film obtained by performing a extending | stretching process and a recrystallization process.   The manufacturing method according to any one of claims 11 to 14, wherein the base material is used in a coating step of the coating liquid without performing an alignment treatment on the surface of the base material.   An image display device comprising the elliptically polarizing plate according to claim 1.

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