JP2008209652A - Manufacturing method of elliptical polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method by which an elliptical polarizing plate having superior contrast in an oblique direction, a wide band and a wide visual field angle can be manufactured so as to have uniform optical characteristics at low cost. <P>SOLUTION: The manufacturing method of the elliptical polarizing plate includes a first birefringence layer forming step for forming a first birefringence layer 13, having refractive index characteristics of nz>nx=ny on a protective film 12; an a second birefringence layer forming step for forming a second birefringence layer 14, having refractive index characteristics of nx>ny=nz on the first birefringence layer 13; an a third birefringence layer forming step for forming a third birefringence layer 15, having refractive index characteristics of nx>ny>nz on the second birefringence layer 14; and a polarizer layering step for layering a polarizer 11 on the surface of the protective film 12, where the first birefringence layer is not formed. The second birefringence layer is formed on the surface of a plastic film F, subjected to rubbing treatment by a rubbing roll 4 and a plurality of backup roll 51 positioned directly under the rubbing roll 4 and transferred to the first birefringence layer 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an elliptically polarizing plate, and in particular, to a manufacturing method capable of manufacturing an elliptically polarizing plate that has excellent contrast in a diagonal direction and has a wide bandwidth and a wide viewing angle so as to have uniform optical characteristics at low cost. .

  In various image display devices such as a liquid crystal display device and an electroluminescence (EL) display, an elliptically polarizing plate is generally used for optical compensation. Such an elliptically polarizing plate is usually manufactured by combining a polarizing film and a quarter wave plate.

  However, a quarter-wave plate exhibits a so-called “positive wavelength dispersion characteristic”, which is a characteristic in which a phase difference value increases as the wavelength becomes shorter, and generally has a large wavelength dispersion characteristic. It is. For this reason, there exists a problem that a quarter wavelength plate cannot exhibit a desired optical characteristic (for example, function as a quarter wavelength plate) over a wide wavelength range. In order to avoid such a problem, as a retardation plate showing so-called “reverse dispersion characteristics”, which is a wavelength dispersion characteristic in which the retardation value increases in the longer wavelength side in recent years, 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, by combining a quarter wave plate having a positive wavelength dispersion characteristic with, for example, a phase difference plate whose phase difference value increases as the wavelength becomes longer, or a half wave plate, A method of correcting the wavelength dispersion characteristic of the / 4 wavelength plate is employed (see, for example, Patent Document 1). However, in recent years, image display devices have become higher in definition, and accordingly, further improvements have been demanded with respect to the oblique contrast and viewing angle of the elliptically polarizing plate (first problem).

  On the other hand, conventionally, optical films such as various retardation plates manufactured by applying a liquid crystal material on the surface of a substrate and aligning it are known. In such an optical film manufacturing process, in order to align the liquid crystal material on the substrate surface, it is common to perform a rubbing treatment that rubs the substrate surface in one direction with, for example, a raised cloth. Such rubbing treatment is preferably carried out continuously by a so-called roll-to-roll method using a long plastic film as a substrate from the viewpoint of production efficiency and cost.

  Therefore, conventionally, various methods for continuously rubbing a long film by the roll-to-roll method as described above have been proposed when manufacturing an optical film such as a retardation plate.

  For example, Patent Document 2 is characterized in that a rubbing process is performed on the film surface with a rubbing roll disposed on the conveying belt while conveying a long film by a conveying belt having a mirror-finished metal surface. A rubbing method is proposed.

  Further, in Patent Document 3, a rubbing process is performed on the film surface with the rubbing roll while a long film is continuously conveyed between the rubbing roll and a backup roll disposed to face the rubbing roll. A rubbing method characterized by this has been proposed.

  In manufacturing an optical film, a material having a linear structure, such as a triacetyl cellulose (TAC) film, is generally used as a base material to be rubbed. In addition, liquid crystal molecules having one or more functional groups are used as the liquid crystal material applied to the surface of the base material (film) that has been subjected to the rubbing treatment. Then, the liquid crystal molecules are made into a solution using an appropriate organic solvent, applied to the surface of the film that has been subjected to rubbing treatment, dried, oriented, exposed to appropriate ultraviolet rays, etc., crosslinked, and fixed. Manufactures optical films.

  However, for example, when a long TAC film or the like is used as a base material and the rubbing treatment is continuously performed by a roll-to-roll method, blocking is performed on the base material wound around the roll before the rubbing treatment ( There is a case in which the base materials adhere to each other without having an optical interface).

  In the base material as described above, since the surface state of the part where blocking occurs changes, even if the base material is subjected to rubbing treatment, the orientation characteristics change between the part where blocking occurs and the other part. There is a problem that a uniform alignment state may not be obtained due to the occurrence of domains in liquid crystalline molecules. For example, when the optical film to be manufactured is a phase difference plate used in a liquid crystal display device, uniformity within the screen is important. Therefore, a phase difference plate with a non-uniform orientation as described above has almost no commercial value. Cannot be obtained (second problem).

  In order to obtain uniform alignment characteristics even for a substrate on which blocking has occurred, for example, in the method described in Patent Document 2, it is conceivable to increase the pushing amount of the rubbing roll. However, in the method described in Patent Document 2, since there is no backup roll that supports the lower surface of the conveyance belt, if the amount of pressing is excessively large, the rubbing is performed in a stable state due to the slackness of the conveyance belt and the film. There is a problem that processing cannot be performed.

  In addition, it is considered that even if the amount of rubbing roll pushed in is increased in the method described in Patent Document 3, uniform orientation characteristics may be obtained for the substrate on which blocking has occurred. However, in the method described in Patent Document 3, since only one backup roll that rotates along the film transport direction is disposed, the rotation axis of the rubbing roll is particularly inclined from the direction perpendicular to the film transport direction. When this is done, there is a problem that the rubbing treatment cannot be performed in a stable state due to the influence of the slackness of the film.

In order to solve the above problems, the lower surface of the conveyance belt that supports the film may be supported by a plurality of bar-shaped backup rolls that are arranged substantially parallel to each other and rotate along the conveyance direction of the conveyance belt. Conceivable. However, particularly when the rotation axis of the rubbing roll is tilted from the direction perpendicular to the film transport direction, there remains a problem that the effect of the slack of the transport belt and the film cannot be sufficiently avoided.
Japanese Patent No. 3174367 JP 2004-170454 A JP-A-6-110059

  The present invention has been made to solve the first and second problems in the prior art. An elliptically polarizing plate having excellent contrast in an oblique direction, a wide bandwidth and a wide viewing angle is obtained at a low cost with uniform optical characteristics. It aims at providing the manufacturing method which can be manufactured so that it may have.

In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies and as a result,
(1) A first birefringent layer having a refractive index characteristic of nz> nx = ny is formed on the protective film, and a second having a refractive index characteristic of nx> ny = nz is formed on the first birefringent layer. A birefringent layer is formed, a third birefringent layer having a refractive index characteristic of nx>ny> nz is formed on the second birefringent layer, and the side on which the first birefringent layer of the protective film is not formed It has been found that by laminating a polarizer on the surface, an elliptically polarizing plate with excellent contrast in an oblique direction and a wide band and a wide viewing angle can be produced.

Regarding the second issue,
(2) A plurality of backup rolls along a straight line that is directly under the rubbing roll and substantially parallel to the rotation axis of the rubbing roll, on the lower surface of the conveying belt that supports and conveys the long plastic film during the rubbing treatment. Even if the rotation axis of the rubbing roll is inclined from the direction perpendicular to the film conveyance direction and the pushing amount of the rubbing roll is increased, the flatness of the conveyance belt is improved and the slack is hardly generated. thing,
(3) By configuring each backup roll to rotate along the conveyance direction of the conveyance belt, the rotation of each backup roll does not hinder the movement of the conveyance belt in the conveyance direction and thus the conveyance of the plastic film,
(4) According to the above (2) and (3), it is possible to perform a rubbing process in a stable state, and it is possible to impart uniform orientation characteristics to the plastic film, and consequently, an elliptically polarizing plate having uniform optical characteristics. Can be manufactured,
I found.
The inventors of the present invention have completed the present invention based on the above new findings (1) to (4).

  That is, the present invention provides a first birefringent layer forming step of forming a first birefringent layer having a refractive index characteristic of nz> nx = ny on the protective film, and nx on the first birefringent layer. A second birefringent layer forming step of forming a second birefringent layer having a refractive index characteristic of> ny = nz, and a second birefringent layer forming step having a refractive index characteristic of nx> ny> nz on the second birefringent layer. A third birefringent layer forming step of forming a birefringent layer of 3 and a polarizer laminating step of laminating a polarizer on the surface of the protective film on which the first birefringent layer is not formed, In the second birefringent layer forming step, the rubbing treatment step of rubbing the surface of the long plastic film with a rubbing roll whose rotation axis is inclined from the direction perpendicular to the conveying direction of the plastic film and the rubbing treatment step are performed. Plastic film surface A birefringent layer forming step of applying a liquid crystal molecule, fixing the applied liquid crystal molecule, and forming a second birefringent layer having a refractive index characteristic of nx> ny = nz on the plastic film And a transfer step of transferring the second birefringent layer formed on the plastic film onto the first birefringent layer, and in the rubbing treatment step, the transfer belt having a metal surface is used to transfer the second birefringent layer. Along with supporting and transporting the long plastic film, a backup roll mechanism for supporting the lower surface of the transport belt that supports the plastic film is disposed, and the backup roll mechanism is arranged along the transport direction of the transport belt. A plurality of rotating backup rolls, each of the plurality of backup rolls being directly below the rubbing roll, It is intended to provide a method for producing an elliptically polarizing plate, characterized in that the rotation axis of the Nguroru are arranged along a straight line substantially parallel.

  According to the present invention, the first birefringent layer having a refractive index characteristic of nz> nx = ny is formed on the protective film, and the refractive index characteristic of nx> ny = nz is formed on the first birefringent layer. A second birefringent layer is formed, a third birefringent layer having a refractive index characteristic of nx> ny> nz is formed on the second birefringent layer, and the first birefringent layer of the protective film is formed An elliptically polarizing plate in which a polarizer is laminated on the surface that is not provided is obtained. Such an elliptically polarizing plate is excellent in contrast in an oblique direction, has a wide band and a wide viewing angle. For this reason, by arranging this in various image display devices such as a liquid crystal display device and an electroluminescence (EL) display, the contrast in the oblique direction in the various image display devices can be improved and the viewing angle can be increased. The second birefringent layer is formed on the rubbed plastic film and then transferred from the plastic film to the first birefringent layer. By transferring the second birefringent layer in this manner, the elliptically polarizing plate does not include a rubbed plastic film, and the thickness of the elliptically polarizing plate can be significantly reduced. Therefore, the elliptically polarizing plate manufactured according to the present invention can greatly contribute to thinning of various image display devices.

  In the present invention, “nx” is the refractive index in the direction in which the in-plane refractive index of each layer is maximized (ie, the slow axis direction), and “ny” is the slow axis in the plane of each layer. The refractive index in the vertical direction (that is, the fast axis direction), and “nz” means the refractive index in the thickness direction of each layer. Further, “ny = nz” means not only the case where ny and nz are exactly equal, but also the case where ny and nz are substantially equal. The term “substantially equal” is intended to include the case where ny and nz are different within a range that does not affect the overall optical characteristics of the elliptically polarizing plate.

  In addition, according to the present invention, it is possible to continuously rub a long plastic film by a roll-to-roll method, so that an elliptically polarizing plate can be manufactured at low cost. Further, according to the present invention, the backup roll mechanism that supports the lower surface of the conveyance belt that supports the plastic film is disposed directly below the rubbing roll and along a straight line that is substantially parallel to the rotation axis of the rubbing roll. Provide multiple backup roles. Therefore, even if the rotating shaft of the rubbing roll is inclined from the direction perpendicular to the conveying direction of the conveying belt, each backup roll is disposed directly below the inclined rubbing roll via the plastic film and the conveying belt. It will be. Furthermore, according to the present invention, each backup roll rotates along the conveyance direction of the conveyance belt (the conveyance direction of the plastic film), so that the rotation of each backup roll moves in the conveyance direction of the conveyance belt and thus the plastic film. There is no hindrance to the transport. Therefore, even if the pushing amount of the rubbing roll is increased while the rotation axis of the rubbing roll is inclined from the direction perpendicular to the conveying direction of the conveying belt, the flatness of the conveying belt is improved and it is difficult to cause looseness and the conveying. The rubbing process can be performed in a stable state without hindering the movement of the belt. As a result, uniform orientation characteristics can be imparted to the plastic film, and it is possible to produce a second birefringent layer having uniform optical characteristics, and thus an elliptically polarizing plate having uniform optical characteristics.

  Preferably, the second birefringent layer functions as a half-wave plate, and the third birefringent layer functions as a quarter-wave plate.

  In the present invention, the “half-wave plate” refers to the in-plane retardation value (= (nx−ny) × d (d: layer thickness) with respect to the wavelength of light (usually the visible light region). (Nm))) is approximately ½, and linearly polarized light having a specific vibration direction is converted into linearly polarized light having a vibration direction orthogonal to the vibration direction of the linearly polarized light, or right circularly polarized light. Is converted into left circularly polarized light (or left circularly polarized light is converted into right circularly polarized light). In the present invention, the “¼ wavelength plate” means that the in-plane retardation value is about 1/4 with respect to the wavelength of light (usually in the visible light region). It has a function of converting linearly polarized light having a wavelength into circularly polarized light (or circularly polarized light into linearly polarized light).

  Preferably, the ratio B / A of the absolute value B of the retardation value Rth [590] in the thickness direction of the first birefringent layer to the absolute value A of the retardation value Rth [590] in the thickness direction of the protective film. However, 1.1 ≦ B / A ≦ 4.0 is satisfied.

  Rth [590] is a retardation value in the thickness direction of the measurement target layer measured with light having a wavelength of 590 nm at 23 ° C. (= (nx−ny) × d (d: thickness of the measurement target layer (nm))) Means. Since the retardation value in the thickness direction of the protective film and the first birefringent layer has such a relationship, the retardation of the protective film can be favorably compensated, and as a result, the contrast in the oblique direction is extremely high. An excellent elliptically polarizing plate can be obtained.

  Preferably, the backup roll mechanism includes a pedestal portion disposed along a straight line substantially parallel to the rotation axis of the rubbing roll, and a shaft support on the pedestal portion so as to be rotatable around a normal line of the surface of the conveyor belt. The plurality of backup rolls are pivotally supported by the plurality of support portions so as to be rotatable along the conveyance direction of the conveyance belt.

  According to such a preferable configuration, even if the rotating shaft of the rubbing roll is inclined from the direction perpendicular to the conveying direction of the conveying belt, the pedestal portion constituting the backup roll mechanism is similarly inclined (that is, the inclined By tilting the pedestal along a straight line that is substantially parallel to the rotation axis of the rubbing roll, the backup is pivotally supported by the support as the conveyor belt moves (by the friction force applied from the lower surface of the conveyor belt). The support portion pivotally supported by the pedestal portion naturally rotates so that the roll is rotated along the conveyance direction of the conveyance belt. In other words, even if the inclination angle of the rubbing roll is not fixed, even if the setting value of the inclination angle is changed, it is only necessary to change the pedestal portion to the same inclination angle as the rubbing roll, so that each backup roll is directly under the rubbing roll. It is possible to arrange and rotate along the conveying direction of the conveying belt.

  More preferably, the backup roll mechanism has the rubbing roll so that when the rotation shaft of the rubbing roll is inclined from a direction perpendicular to the conveying direction of the conveying belt, the pedestal portion is also inclined accordingly. And a connecting mechanism for connecting the pedestal part.

  According to such a preferable configuration, when the rotating shaft of the rubbing roll is inclined from the direction perpendicular to the conveying direction of the conveying belt, the rubbing roll and the pedestal portion are coupled so that the pedestal portion is also inclined accordingly. Since the coupling mechanism is provided, it has an advantage that setting is extremely easy as compared with the configuration in which the rubbing roll and the backup roll mechanism (pedestal part) are individually inclined.

  In addition, it is preferable that the rotating shaft of the rubbing roll is inclined from more than 0 ° to 45 ° or less from the direction perpendicular to the plastic film conveying direction.

  Here, for the plurality of backup rolls, when the distance between the centers of adjacent backup rolls in the rotation axis direction is set to be greater than 200 mm, the flatness of the transport belt is lowered, resulting in uneven orientation. There is a risk of defects. On the other hand, when the center-to-center distance is set to be smaller than 60 mm, the width of the member that supports the backup roll is reduced, and the strength for stably holding the backup roll is reduced. To do. Therefore, in order to avoid the above problems reliably, the distance between the centers of the adjacent backup rolls in the rotation axis direction is preferably set to 60 mm or more and 200 mm or less, and preferably set to 70 mm or more and 150 mm or less. More preferred.

  Further, when the width of the plurality of backup rolls in the rotation axis direction is set to be smaller than 20 mm, there is a possibility that the conveyor belt is damaged by frictional heat. On the other hand, when the width is set to be larger than 150 mm, the backup roll may be disposed immediately below the rubbing roll when the rotation axis of the rubbing roll is inclined from the direction perpendicular to the conveying direction of the plastic film. As a result, the flatness of the conveying belt is lowered, and as a result, alignment unevenness may occur and appearance defects may occur. Therefore, in order to surely avoid the above problems, the width in the rotation axis direction of each of the plurality of backup rolls is preferably set to 20 mm or more and 150 mm or less, and more preferably set to 25 mm or more and 70 mm or less. .

  The production method according to the present invention is particularly effective when the plastic film is a triacetyl cellulose film or a polyethylene terephthalate film.

  It is preferable that a raised cloth is wound around the rubbing roll. As the raised cloth, for example, any one of rayon, cotton, nylon, triacetate and a mixture thereof is preferably used.

  Furthermore, the thickness of the conveyor belt is preferably 0.5 mm to 2.0 mm (more preferably 0.7 to 1.5 mm) in order to impart flexibility while preventing it from being easily slackened. The

  According to the method for producing an elliptically polarizing plate according to the present invention, an elliptically polarizing plate having excellent oblique contrast and a wide band and a wide viewing angle can be obtained. For this reason, by arranging this elliptically polarizing plate in various image display devices, the contrast in the oblique direction in the various image display devices can be improved and the viewing angle can be increased. The second birefringent layer is formed on the rubbed plastic film and then transferred from the plastic film to the first birefringent layer. Since the second birefringent layer is transferred in this manner, the elliptically polarizing plate does not include a rubbed plastic film, and thus the thickness of the elliptically polarizing plate can be significantly reduced. Therefore, the elliptically polarizing plate manufactured according to the present invention can greatly contribute to thinning of various image display devices. Furthermore, even when the rotation axis of the rubbing roll is inclined from the direction perpendicular to the film conveyance direction, it is possible to produce an elliptically polarizing plate having uniform optical characteristics at low cost. Specifically, it is difficult for foreign matters to adhere to the surface, and it is possible to maintain a good appearance of an elliptically polarizing plate. This is because the flatness of the conveyor belt is improved by arranging a plurality of backup rolls directly below the rubbing roll with the center-to-center distance in the rotation axis direction being a predetermined value.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

I. The configuration First of elliptically polarizing plate, a configuration example of the elliptically polarizing plate manufactured by the manufacturing method according to the present invention.

<Overall configuration of elliptically polarizing plate>
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an elliptically polarizing plate manufactured by the manufacturing method according to the present embodiment. As shown in FIG. 1, the elliptically polarizing plate 10 according to the present embodiment is formed on a protective film 12, a first birefringent layer 13 formed on the protective film 12, and a first birefringent layer 13. The second birefringent layer 14, the third birefringent layer 15 formed on the second birefringent layer 14, and the surface of the protective film 12 on the side where the first birefringent layer 13 is not formed. And a stacked polarizer 11. Practically, the elliptically polarizing plate 10 according to this embodiment includes a second protective film 16 laminated on the surface of the polarizer 11 on which the protective film 12 is not laminated.

  The first birefringent layer 13 has a refractive index characteristic of nz> nx = ny. The second birefringent layer 14 has a refractive index characteristic of nx> ny = nz, and the third birefringent layer 15 has a refractive index characteristic of nx> ny> nz. Furthermore, the ratio B / A of the absolute value B of the retardation value Rth [590] in the thickness direction of the first birefringent layer 13 to the absolute value A of the retardation value Rth [590] in the thickness direction of the protective film 12 is The range is preferably 1.1 ≦ B / A ≦ 4.0, more preferably 1.5 ≦ B / A ≦ 3.0. Since the absolute value of the retardation value Rth [590] in the thickness direction between the protective film 12 and the first birefringent layer 13 has such a relationship, the retardation of the protective film 12 can be favorably compensated. As a result, the contrast in the oblique direction of the elliptically polarizing plate 10 is extremely excellent. Rth [590] is a retardation value in the thickness direction of the measurement target layer measured with light having a wavelength of 590 nm at 23 ° C. (= (nx−ny) × d (d: thickness of the measurement target layer (nm))) Means.

  2 is an exploded perspective view for explaining the relationship between the absorption axis and the slow axis of each layer constituting the elliptically polarizing plate 10 shown in FIG. 1 (in FIG. 2, the second protection is shown for the sake of clarity). The film 16 is omitted.). The second birefringent layer 14 is laminated so that the slow axis B forms a predetermined angle α with respect to the absorption axis A of the polarizer 11. The angle α is preferably + 8 ° ≦ α ≦ + 38 ° or −38 ° ≦ α ≦ −8 °, more preferably + 13 ° ≦ α ≦ + 33 ° or −33 ° ≦ α ≦ −13 °, particularly preferably +19. ° ≦ α ≦ + 29 ° or −29 ° ≦ α ≦ −19 °, particularly preferably + 21 ° ≦ α ≦ + 27 ° or −27 ° ≦ α ≦ −21 °, most preferably + 23 ° ≦ α ≦ + 24 ° or −. 24 ° ≦ α ≦ −23 °. Note that the positive and negative values of α are positive in the counterclockwise direction with respect to the absorption axis A and negative in the clockwise direction. The elliptical polarizing plate 10 has very excellent polarization characteristics by being laminated so that the slow axis B of the second birefringent layer 14 and the absorption axis A of the polarizer 11 form such an angle α. become. Further, as shown in FIG. 2, the third birefringent layer 15 is laminated so that its slow axis C is substantially perpendicular to the absorption axis A of the polarizer 11. “Substantially orthogonal” is not limited to being completely orthogonal, preferably 90 ° ± 2.0 °, more preferably 90 ° ± 1.0 °, and most preferably 90 ° ± 0.5 °.

  The total thickness of the elliptically polarizing plate 10 of the present embodiment is preferably 80 to 250 μm, more preferably 110 to 220 μm, and most preferably 140 to 190 μm. This thickness is much thinner than the thickness that can be realized with a conventional elliptically polarizing plate. This is because, as will be described later, the second birefringent layer 14 is formed on the rubbed plastic film and then transferred from the plastic film to the first birefringent layer 13. By transferring the second birefringent layer 14 in this manner, the elliptically polarizing plate 10 does not include a rubbed plastic film, and the thickness of the elliptically polarizing plate 10 can be significantly reduced. As a result, the elliptically polarizing plate 10 according to the present embodiment can greatly contribute to reducing the thickness of the image display device.

<Configuration of first birefringent layer>
As described above, the first birefringent layer 13 has a refractive index distribution of nz> nx = ny. Further, the absolute value B of the thickness direction retardation value Rth [590] of the first birefringent layer 13 is as described above with respect to the absolute value A of the thickness direction retardation value Rth [590] of the protective film 12. By having a desirable ratio, it becomes possible to favorably compensate for the phase difference of the protective film 12, and as a result, the contrast in the oblique direction of the elliptically polarizing plate 10 becomes extremely good.

  The absolute value B of the thickness direction retardation value Rth [590] of the first birefringent layer 13 is set so that the thickness direction retardation of the protective film 12 is well compensated. For example, the absolute value B of the thickness direction retardation value Rth [590] of the first birefringent layer 13 is preferably 50 to 200 nm, more preferably 75 to 150 nm, and most preferably 90 to 120 nm. The thickness of the first birefringent layer 13 from which such an absolute value B can be obtained can vary depending on the material used. For example, the thickness of the first birefringent layer 13 is preferably 0.5 to 10 μm, more preferably 0.5 to 8 μm, and most preferably 0.5 to 5 μm.

  The first birefringent layer 13 is preferably made of a film containing liquid crystalline molecules fixed in homeotropic alignment. The liquid crystal molecule (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Examples of typical liquid crystal compounds include nematic liquid crystal compounds. An outline of such a liquid crystal compound alignment technique is described in, for example, Chemical Review 44 (Surface Modification, Edited by Chemical Society of Japan, pages 156 to 163).

  Moreover, as a liquid crystalline molecule which can form homeotropic alignment, for example, a side chain containing a monomer unit (a) containing a liquid crystalline fragment side chain and a monomer unit (b) containing a non-liquid crystalline fragment side chain Type liquid crystal polymer. Such a side-chain liquid crystal polymer can realize homeotropic alignment without using a vertical alignment agent or a vertical alignment film. This is because, by the action of the monomer unit (b) containing a non-liquid crystalline fragment side chain having an alkyl chain or the like, a liquid crystal state (for example, a nematic liquid crystal phase) is exhibited by, for example, heat treatment without using a vertical alignment film. Thus, it is assumed that homeotropic alignment is realized.

  The monomer unit (a) has a side chain having nematic liquid crystallinity, and examples thereof include a monomer unit represented by the general formula (a).

In the formula (a), R ¹ is a hydrogen atom or a methyl group, a is a positive integer of 1 to 6, X ¹ is a —CO ₂ — group or —OCO— group, and R ² is a cyano group. , An alkoxy group having 1 to 6 carbon atoms, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, and b and c each represent an integer of 1 or 2.

  Moreover, a monomer unit (b) has a linear side chain, for example, the monomer unit represented by General formula (b) is mentioned.

In the formula (b), R ³ is a hydrogen atom or a methyl group, and R ⁴ is an alkyl group having 1 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or a group represented by the general formula (b1) It is.

In the formula (b1), d is a positive integer of 1 to 6, and R ⁵ is an alkyl group having 1 to 6 carbon atoms.

  Moreover, the ratio of the monomer unit (a) and the monomer unit (b) can be appropriately set according to the purpose and the type of the monomer unit. (B) / {(a) + (b)} is preferably 0.01 to 0.8 (molar ratio), more preferably 0.1 to 0.5 (molar ratio). This is because when the proportion of the monomer unit (b) increases, the side chain type liquid crystal polymer often does not exhibit liquid crystal monodomain alignment.

  Further, for example, as the liquid crystalline molecules capable of forming homeotropic alignment, the monomer unit (a) containing the liquid crystalline fragment side chain described above and the monomer unit containing the liquid crystalline fragment side chain having an alicyclic ring structure ( and a side chain type liquid crystal polymer containing c). Such a side-chain liquid crystal polymer can also realize homeotropic alignment without using a vertical alignment agent or a vertical alignment film. This is presumably due to the action of the monomer unit (c), homeotropic alignment is realized by developing a liquid crystal state (for example, nematic liquid crystal phase) by heat treatment, for example, without using a vertical alignment film. .

  A monomer unit (c) has a side chain which has a nematic liquid crystallinity, for example, the monomer unit represented by general formula (c) is mentioned.

In the formula (c), R ⁶ is a hydrogen atom or a methyl group, h is a positive integer of 1 to 6, X ² is a —CO— group or a —OCO— group, and e and g are Each is an integer of 1 or 2, f is an integer of 0 to 2, and R ⁷ is a cyano group or an alkyl group having 1 to 12 carbon atoms.

  Further, the ratio of the monomer unit (a) to the monomer unit (c) can be appropriately set according to the purpose and the type of the monomer unit. (C) / {(a) + (c)} is preferably 0.01 to 0.8 (molar ratio), more preferably 0.1 to 0.6 (molar ratio). This is because as the proportion of the monomer unit (c) increases, the side chain type liquid crystal polymer often does not exhibit liquid crystal monodomain alignment.

  The above monomer unit is merely an example, and it goes without saying that the liquid crystal polymer capable of forming homeotropic alignment is not limited to one having the above monomer unit. In addition, the above exemplified monomer units can be appropriately combined.

  The weight average molecular weight of the side chain type liquid crystal polymer is preferably 2,000 to 100,000. By adjusting the weight average molecular weight to such a range, the performance as a liquid crystal polymer can be satisfactorily exhibited. The weight average molecular weight is more preferably 2,500 to 50,000. If it is such a range, it is excellent in the film formability of an orientation layer, and a uniform orientation state can be formed.

  The above exemplified side chain type liquid crystal polymer can be prepared by copolymerizing an acrylic monomer or a methacrylic monomer corresponding to the monomer unit (a), the monomer unit (b) or the monomer unit (c). The monomer corresponding to the monomer unit (a), the monomer unit (b) or the monomer unit (c) can be synthesized by any appropriate method. The copolymer can be adjusted according to any appropriate polymerization method such as an acrylic monomer (for example, radical polymerization method, cationic polymerization method, anionic polymerization method). In addition, when applying radical polymerization system, various polymerization initiators can be used. Preferred polymerization initiators include azobisisobutyronitrile or benzoyl peroxide. This is because the polymerization can be started with an appropriate mechanism and speed because it can be decomposed at an appropriate temperature (not high or low).

The homeotropic alignment can also be formed from a liquid crystalline composition containing a side chain type liquid crystal polymer. Such a liquid crystal composition may contain a photopolymerizable liquid crystal compound in addition to the liquid crystal polymer. The photopolymerizable liquid crystal compound is a liquid crystal compound having at least one photopolymerizable functional group (for example, an unsaturated double bond such as an acryloyl group or a methacryloyl group). As the liquid crystal composition, those exhibiting nematic liquid crystal properties are preferable. Specific examples of such a photopolymerizable liquid crystal compound include acrylates and methacrylates that can also be used as the monomer unit (a). Further, more preferable photopolymerizable liquid crystal compounds include those having two or more photopolymerizable functional groups. This is because the durability of the resulting film (second birefringent layer 14) can be improved. Examples of the photopolymerizable liquid crystal compound having two or more photopolymerizable functional groups include a crosslinked nematic liquid crystal monomer represented by the following formula. Further, as the photopolymerizable liquid crystal compound, a compound in which “H ₂ C═CR—CO ₂ —” at the terminal in the following formula is substituted with a vinyl ether group or an epoxy group, “— (CH ₂ ) m—” and / or Alternatively, “— (CH ₂ ) n—” is replaced with “— (CH ₂ ) ₃ —C ^* H (CH ₃ ) — (CH ₂ ) ₂ —” or “— (CH ₂ ) ₂ —C ^* H (CH ₃ )”. A compound substituted with “— (CH ₂ ) ₃ —” can be exemplified.

In Formula (d), R ⁸ is a hydrogen atom or a methyl group, A and D are each independently a 1,4-phenylene group or a 1,4-cyclohexylene group, and Y is each independently -COO- group, -OCO- group or -O- group, and B is 1,4-phenylene group, 1,4-cyclohexylene group, 4,4'-biphenylene group or 4,4 ' -Bicyclohexylene group, and m and n each independently represents an integer of 2 to 6.

  The photopolymerizable liquid crystal compound can be brought into a liquid crystal state by heat treatment, for example, to exhibit a nematic liquid crystal phase and to be homeotropically aligned with the side chain liquid crystal polymer. Next, the durability of the first birefringent layer 13 can be further improved by polymerizing or crosslinking the photopolymerizable liquid crystal compound to fix the homeotropic alignment.

  The ratio of the photopolymerizable liquid crystal compound to the side chain type liquid crystal polymer in the liquid crystal composition is determined according to the purpose, the type of the side chain type liquid crystal polymer and the photopolymerizable liquid crystal compound used, and the obtained first birefringent layer 13. It can be appropriately set in consideration of durability. Specifically, the photopolymerizable liquid crystal compound: side chain type liquid crystal polymer (weight ratio) is preferably about 0.1: 1 to 30: 1, more preferably 0.5: 1 to 20: 1, most preferably. Is 1: 1 to 10: 1.

  The liquid crystalline composition may further contain a photopolymerization initiator. Any appropriate photopolymerization initiator can be adopted as the photopolymerization initiator. Specific examples include Irgacure 907, 184, 651, and 369 manufactured by Ciba Specialty Chemicals. The content of the photopolymerization initiator can be adjusted to such an extent that the homeotropic orientation of the liquid crystalline composition is not disturbed in consideration of the type of the photopolymerizable liquid crystal compound, the blending ratio of the liquid crystalline composition, and the like. Typically, the content of the photopolymerization initiator is preferably about 0.5 to 30 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the photopolymerizable liquid crystal compound. The

<Configuration of second birefringent layer>
As described above, the second birefringent layer 14 has a refractive index characteristic of nx> ny = nz. Preferably, the second birefringent layer 14 functions as a so-called half-wave plate. When the second birefringent layer 14 functions as a half-wave plate, the wavelength distribution characteristics of the third birefringent layer 15 functioning as a quarter-wave plate (in particular, the in-plane retardation value is λ / 4). (Λ: a wavelength range outside of the wavelength of light) is appropriately corrected. The in-plane retardation value Re [590] of the second birefringent layer 14 is preferably 200 to 300 nm, more preferably 220 to 280 nm, and most preferably 230 to 270 nm. Re [590] is the in-plane retardation value of the birefringent layer (= (nx−ny) × d (d: thickness of birefringent layer (nm))) measured with light having a wavelength of 590 nm at 23 ° C. means.

  The thickness of the second birefringent layer 14 can be set so that it can function most appropriately as a half-wave plate. In other words, the thickness of the second birefringent layer 14 may be set so as to obtain a desired in-plane retardation value. Specifically, the thickness of the second birefringent layer 14 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 second birefringent layer 14, liquid crystal molecules are used. The liquid crystal phase is preferably a liquid crystal molecule having a nematic phase. By using liquid crystal molecules, the difference between nx and ny of the second birefringent layer 14 can be made significantly larger than that of non-liquid crystal molecules. As a result, the thickness of the second birefringent layer 14 for obtaining a desired in-plane retardation value can be significantly reduced. As such a liquid crystalline molecule, a liquid crystal polymer, a liquid crystal prepolymer, a liquid crystal monomer, or the like is appropriately used. You may use combining these. The lyotropic or thermotropic mechanism of liquid crystal molecules may be used. The alignment state of the liquid crystal is preferably homogeneous alignment.

  When the liquid crystal molecule forming the second birefringent layer 14 is a liquid crystal monomer, for example, it is preferably a polymerizable monomer or a crosslinkable monomer. This is because the alignment state of the liquid crystalline molecules can be fixed by polymerizing or crosslinking the polymerizable monomer or the crosslinkable monomer. If the liquid crystal monomers (polymerizable monomer or crosslinkable monomer) are polymerized or crosslinked after the liquid crystal monomer is aligned, the alignment state can be fixed. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed second birefringent layer 14 does not cause a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change, which is characteristic of a liquid crystal compound. As a result, the second birefringent layer 14 is a birefringent layer that is extremely stable and not affected by temperature changes. The polymerizable monomer and the crosslinkable monomer may be used in combination.

As the liquid crystal monomer, for example, a monomer represented by any of the following chemical formulas (1) to (16) can be selected.

<Configuration of third birefringent layer>
As described above, the third birefringent layer 15 has a refractive index characteristic of nx>ny> nz. Preferably, the third birefringent layer 15 functions as a so-called quarter wavelength plate. By correcting the wavelength dispersion characteristics of the third birefringent layer 15 functioning as a quarter-wave plate by the optical characteristics of the second birefringent layer 14 functioning as a half-wave plate, the elliptically polarizing plate 10 The circular polarization function in a wide wavelength range can be exhibited. The in-plane retardation value Re [590] of the third birefringent layer 15 is preferably 90 to 160 nm, more preferably 100 to 150 nm, and most preferably 110 to 140 nm. The Nz coefficient (= (nx−nz) / (nx−ny)) of the third birefringent layer 15 is preferably 1.0 to 2.2, more preferably 1.2 to 2.0, most preferably 1.4 to 1.8. The “Nz coefficient” is obtained by Nz = (nx−ny) / (nx−ny) using refractive indexes nx, ny and nz measured with light having a wavelength of 590 nm at 23 ° C.

  The thickness of the third birefringent layer 15 can be set so that it can function most appropriately as a quarter-wave plate. In other words, the thickness of the third birefringent layer 15 may be set so as to obtain a desired in-plane retardation value. Specifically, the thickness of the third birefringent layer 15 is preferably 10 to 100 μm, more preferably 20 to 80 μm, and most preferably 40 to 70 μm.

  The third birefringent layer 15 can typically be formed by stretching a polymer film. For example, by appropriately selecting the type of polymer, stretching conditions (for example, stretching temperature, stretching ratio, stretching direction), stretching method, and the like, desired optical characteristics (for example, refractive index distribution, in-plane retardation value Re [ 590], the thickness direction retardation value Rth [590], and the Nz coefficient), the third birefringent layer 15 is obtained. More specifically, the stretching temperature is preferably 120 to 180 ° C, more preferably 140 to 170 ° C. The draw ratio is preferably 1.05 to 2.0 times, more preferably 1.3 to 1.6 times. Examples of the stretching method include lateral uniaxial stretching. The stretching direction is preferably a direction substantially perpendicular to the absorption axis A of the polarizer 11 (the width direction of the polymer film, that is, the direction perpendicular to the longitudinal direction).

  Any appropriate polymer can be adopted as the polymer constituting the polymer film. Specific examples include positive birefringent films such as polycarbonate-based polymers, norbornene-based polymers, cellulose-based polymers, polyvinyl alcohol-based polymers, and polysulfone-based polymers. Among these, polycarbonate-based polymers and norbornene-based polymers are preferable.

<Configuration of polarizer>
Any appropriate polarizer may be used 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 a polyene-based oriented film such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product or 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 obtained by uniaxially stretching iodine by adsorbing iodine to a polyvinyl alcohol film is prepared by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it 3 to 7 times the original length. Can do. 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 the polyvinyl alcohol film can also be swollen to prevent unevenness such as uneven coloring. can get. Stretching may be performed after dyeing with iodine, may be stretched while dyeing, or may be dyed with iodine after stretching. It can be stretched in an aqueous solution such as boric acid or potassium iodide or in an aqueous solution.

<Configuration of protective film and second protective film>
Moreover, the protective film 12 and the 2nd protective film 16 can use arbitrary appropriate films which can be used as a protective film of the polarizer 11. Preferably, the protective film 12 and the second protective film 16 are transparent protective films.

  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 of this polymer film, for example, a resin 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 The composition can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film may be obtained by, for example, extruding the resin composition. As a material of the protective film 12 and the second protective film 16, TAC, polyimide resin, polyvinyl alcohol resin, and glassy polymer are preferable, and TAC is more preferable.

  The protective film 12 and the second protective film 16 are preferably transparent and have no color. Specifically, the thickness direction retardation value Rth [550] is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and most preferably −70 nm to +70 nm.

  As thickness of the protective film 12 and the 2nd protective film 16, as long as said preferable thickness direction retardation value is obtained, it can be set as arbitrary appropriate thickness. Specifically, the thickness of the protective film 12 and the second protective film 16 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 protective film 12 and the second protective film 16 may be the same or different. The protective film 12 and the second protective film 16 are subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, an antiglare treatment, and the like as necessary.

<Other components of elliptical polarizing plate>
The elliptically polarizing plate 10 according to the present embodiment may be configured to further include another optical layer. As such another optical layer, any appropriate optical layer may be employed depending on the purpose and the type of image display device such as a liquid crystal display device to be applied. Specific examples include a liquid crystal film, a light scattering film, a diffraction film, and a birefringence layer (retardation film) other than the first to third birefringence layers 13, 14, and 15 described above.

  The elliptically polarizing plate 10 according to this embodiment may be configured to further include a pressure-sensitive adhesive layer or an adhesive layer as an outermost layer on at least one side. Thus, by providing a pressure-sensitive adhesive layer or an adhesive layer as the outermost layer, for example, lamination with another member (for example, a liquid crystal cell) becomes easy, and the elliptically polarizing plate 10 is peeled off from the other member. Can be prevented. Any appropriate material can be used as a material for forming the pressure-sensitive adhesive layer and the adhesive layer. 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 above-mentioned pressure-sensitive adhesive layer or adhesive layer is covered with any appropriate separator until the elliptically polarizing plate 10 is actually used, and contamination is prevented. The separator is 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.

  Each layer constituting the elliptically polarizing plate 10 has an 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 given.

II. Method for producing an elliptically polarizing plate Next, a method for manufacturing the elliptically polarizing plate 10 having the configuration described above.

  The manufacturing method of the elliptically polarizing plate 10 according to the present embodiment includes a first birefringent layer forming step of forming a first birefringent layer 13 having a refractive index characteristic of nz> nx = ny on the protective film 12, and A second birefringent layer forming step of forming a second birefringent layer 14 having a refractive index characteristic of nx> ny = nz on the first birefringent layer 13; and nx on the second birefringent layer 14. A third birefringent layer forming step for forming the third birefringent layer 15 having a refractive index characteristic of> ny> nz, and a polarizer on the surface of the protective film 12 on which the first birefringent layer 13 is not formed. 11 includes laminating a polarizer 11 and laminating a second protective film 16 on the surface of the polarizer 11 on which the protective film 12 is not formed. In addition, the order of each said process can be changed suitably. Hereinafter, details of each process will be described in detail.

<First birefringent layer forming step>
In the first birefringent layer forming step, the first birefringent layer 13 is formed on one surface of the protective film 12. As a typical method for forming the first birefringent layer 13 on one surface of the protective film 12, a liquid crystal molecule (a liquid crystal monomer or a liquid crystal polymer) and / or a liquid crystal composition is applied on one surface of the protective film 12. There is a method in which these are applied in a homeotropic orientation in a state where they exhibit a liquid crystal phase, and these are fixed in a state where the orientation is maintained. Below, this typical formation method is demonstrated. In addition, although description is abbreviate | omitted below, as another method of forming the 1st birefringent layer 13 on one surface of the protective film 12, for example, the homeotropic orientation fixed film formed on the board | substrate is used for the protective film 12 The method of transferring to is mentioned.

  As a method for applying a liquid crystal molecule (liquid crystal monomer or liquid crystal polymer) or a liquid crystal composition on the protective film 12, a solution coating method using a solution in which a liquid crystal molecule or a liquid crystal composition is dissolved in a solvent, or And a melt coating method in which a functional molecule or a liquid crystal composition is melted and melt-coated. Of these methods, the solution coating method is a preferred method. This is because homeotropic alignment can be realized precisely and easily.

  Any appropriate solvent capable of dissolving the liquid crystalline molecules or the liquid crystalline composition can be adopted as the solvent used when adjusting the solution coating solution. Specific examples include halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, phenols such as phenol and parachlorophenol, benzene, toluene, xylene, methoxybenzene, 1,2- Aromatic hydrocarbons such as dimethoxybenzene, acetone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol dimethyl ether, ethyl cellosolve, butyl cellosolve, 2- Pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylamine Toamido, dimethyl sulfoxide, acetonitrile, butyronitrile, carbon disulfide, and cyclohexanone. The concentration of the solution can vary depending on the type (solubility) of the liquid crystal molecule or liquid crystal composition to be used, the thickness of the first birefringent layer 13 intended, and the like. Specifically, the concentration of the solution is preferably 3 to 50% by weight, more preferably 7 to 30% by weight.

  Examples of the method for applying the above solution to the protective film 12 include a roll coating method, a gravure coating method, a spin coating method, and a bar coating method. Among these, a gravure coating method and a bar coating method that are easy to uniformly coat a large area are preferable methods.

  When the solution is applied to the protective film 12, the solvent is then removed from the solution to form a liquid crystalline molecular layer or a liquid crystalline composition layer on the protective film 12. The conditions for removing the solvent are not particularly limited, as long as the solvent can be substantially removed and the liquid crystalline molecular layer or the liquid crystalline composition layer does not flow or even flows down. The removal of the solvent is usually performed using drying at room temperature, drying in a drying furnace, heating on a hot plate, or the like.

  Next, the liquid crystalline molecules (liquid crystalline molecular layer) and / or the liquid crystalline composition (liquid crystalline composition layer) coated on one surface of the protective film 12 as described above are homeotropically aligned. As a method for homeotropic alignment, there is a method in which the liquid crystalline molecules or the liquid crystalline composition are subjected to a heat treatment so that the liquid crystalline molecules or the liquid crystalline composition exhibit a liquid crystalline state, and the liquid crystalline molecules or the liquid crystalline composition is homeotropically aligned in the liquid crystalline state. It is done. The heat treatment can be performed by the same method as the above drying method. The heat treatment temperature and the heat treatment time can vary depending on the type of liquid crystal molecules or liquid crystal composition used and the protective film 12. The heat treatment temperature is preferably 60 to 300 ° C, more preferably 70 to 200 ° C, and most preferably 80 to 150 ° C. On the other hand, the heat treatment time is preferably 10 seconds to 2 hours, more preferably 20 seconds to 30 minutes, and most preferably 30 seconds to 10 minutes. The preferable time is 10 seconds to 2 hours. If the heat treatment time is shorter than 10 seconds, the homeotropic alignment formation may not proceed sufficiently, and if the heat treatment time exceeds 2 hours, the homeotropic alignment formation is reduced. This is because there are many cases where the above does not proceed, which is not preferable in terms of workability and mass productivity.

  After the heat treatment is completed, a cooling operation is performed. Examples of the cooling operation include taking out the homeotropic alignment liquid crystal layer after the heat treatment from the heating atmosphere in the heat treatment operation to room temperature, or performing forced cooling such as air cooling or water cooling. When the homeotropic alignment liquid crystal layer is cooled below the glass transition temperature by the cooling operation, the alignment of the homeotropic alignment liquid crystal layer is fixed.

When the liquid crystalline composition is applied on the protective film 12, as a method for fixing the holotropically aligned liquid crystalline composition, there is a method of irradiating the liquid crystalline composition with light irradiation or ultraviolet irradiation. . When the liquid crystalline composition is irradiated with light or ultraviolet light, the photopolymerizable liquid crystal compound contained in the liquid crystalline composition is polymerized or cross-linked, and the photopolymerizable liquid crystal compound is fixed, thereby further improving durability. Can be improved. The ultraviolet irradiation conditions are preferably in an inert gas atmosphere in order to sufficiently accelerate the polymerization or the crosslinking reaction. As the ultraviolet irradiation means, a high-pressure mercury ultraviolet lamp having an illuminance of about 80 to 160 mW / cm ² can be used. In addition, other types of lamps such as metal halide UV lamps and incandescent tubes can be used. In addition, it is preferable to adjust the temperature so that the surface temperature of the liquid crystalline composition during ultraviolet irradiation is in a temperature range exhibiting a liquid crystal state. Examples of temperature control methods include cold mirrors, water cooling and other cooling processes, or increasing the line speed.

  As described above, the protective film 12 is obtained by coating the liquid crystalline molecules or the liquid crystalline composition on the protective film 12 and homeotropically orienting the liquid crystalline molecules or the liquid crystalline composition to fix the alignment state. A first birefringent layer 13 having homeotropic orientation is formed thereon.

<Second birefringent layer forming step>
The second birefringent layer forming step includes a rubbing treatment step in which the surface of a long plastic film is rubbed with a rubbing roll having a rotation axis inclined from a direction perpendicular to the conveying direction of the plastic film, and the plastic that has undergone the rubbing treatment step A liquid crystal molecule is applied on the surface of the film, the applied liquid crystal molecule is fixed, and a second birefringent layer 14 having a refractive index characteristic of nx> ny = nz is formed on the plastic film. A refraction layer forming step, and a transfer step of transferring the second birefringent layer 14 formed on the plastic film onto the first birefringent layer 13.

(Rubbing process)
FIG. 3 is a front view showing a schematic configuration of a rubbing processing apparatus for performing the rubbing processing step. 4 is a diagram showing a schematic configuration of the backup roll mechanism shown in FIG. 3. FIG. 4 (a) is a plan view, FIG. 4 (b) is a perspective view in the vicinity of the backup roll, and FIG. The figure seen from the conveyance direction of a long plastic film is shown, respectively. As shown in FIG. 3, the rubbing treatment apparatus 100 according to the present embodiment has an endless track that is installed between the driving rolls 1 and 2 and the driving rolls 1 and 2 and supports and transports a long plastic film F. A conveyor belt 3, a rubbing roll 4 disposed above and below the conveyor belt 3 so as to be movable up and down, and a backup roll mechanism 5 that supports the lower surface of the conveyor belt 3 that supports the long plastic film F are provided. ing. In addition, before and after the rubbing apparatus 100, an appropriate static eliminator or dust remover may be installed as necessary.

  The conveyor belt 3 is a metal surface (the entire conveyor belt 3 may be made of metal) having a mirror-finished surface that supports the plastic film F. As the metal, various metal materials such as copper and steel can be used, but it is preferable to use stainless steel from the viewpoint of strength, hardness and durability. In order to ensure adhesion with the plastic film F, the surface finish (Ra) is preferably 0.02 μm or less, more preferably 0.01 μm or less as the degree of mirror finish. In order to prevent the plastic film F from slackening, it is necessary to prevent the conveyance belt 3 that supports the plastic film F from slackening. In view of the fact that it is necessary to provide a certain degree of flexibility in order to prevent the conveyor belt 3 from slacking and to be installed between the drive rolls 1 and 2, the thickness of the conveyor belt 3 is 0.5 mm to 2 mm. The thickness is preferably 0 mm, more preferably 0.7 mm to 1.5 mm. In addition, the tension applied to the conveyor belt 3 is preferably 0.5 to 20 kgf / mm 2, more preferably, considering the tension strength of the conveyor belt 3 while preventing slack of the conveyor belt 3. 2 to 15 kg weight / mm 2.

  The rubbing roll 4 has a brushed cloth 4a wound around its outer peripheral surface. What is necessary is just to select suitably the material, shape, etc. of a raising cloth according to the material of the plastic film F to which the rubbing process is performed. In general, rayon, cotton, nylon, triacetate, or a mixture thereof can be applied as the raised cloth 4a. The rotation axis of the rubbing roll 4 according to the present embodiment is inclined from a direction perpendicular to the conveyance direction of the plastic film F (the direction indicated by the arrow A in FIG. 3) (for example, the inclination angle exceeds 0 ° and is 45 ° or less). ), That is, an arbitrary axial angle with respect to the long side of the plastic film F can be set. Moreover, the rotation direction of the rubbing roll 4 can be appropriately selected according to the conditions of the rubbing treatment. The outer diameter of the rubbing roll 4 (including the raised cloth 4a) is preferably set to 130 mm to 170 mm (more preferably 140 mm to 160 mm).

  The rubbing direction (orientation direction) of the plastic film F by the rubbing roll 4 is set to a predetermined angle θ with respect to the absorption axis A (see FIG. 2) of the polarizer 11 when the plastic film F and the polarizer 11 are laminated. It is assumed to be the direction to be formed. The rubbing direction of the plastic film F is substantially the same as the direction of the slow axis B (see FIG. 2) of the second birefringent layer 14 formed on the surface of the plastic film F. Therefore, the predetermined angle θ formed by the rubbing direction of the plastic film F and the absorption axis A of the polarizer 11 is preferably + 8 ° ≦ θ ≦, similarly to the angle α formed by the slow axis B and the absorption axis A. + 38 ° or −38 ° ≦ θ ≦ −8 °, more preferably + 13 ° ≦ θ ≦ + 33 ° or −33 ° ≦ θ ≦ −13 °, particularly preferably + 19 ° ≦ θ ≦ + 29 ° or −29 ° ≦ θ ≦ −19 °, particularly preferably + 21 ° ≦ θ ≦ + 27 ° or −27 ° ≦ θ ≦ −21 °, and most preferably + 23 ° ≦ θ ≦ + 24 ° or −24 ° ≦ θ ≦ −23 °.

  When the polarizer 11 is obtained by uniaxially stretching a polymer film on which a dichroic substance is adsorbed, the stretching direction coincides with the direction of the absorption axis A. And when mass-producing the polarizer 11, it is common to prepare a long polymer film and to perform a extending | stretching process continuously in the longitudinal direction. For this reason, when laminating the long polarizer 11 and the second birefringent layer 14 formed on the surface of the long plastic film F, the longitudinal direction of both is the absorption axis A of the polarizer 11. Substantially coincides with the direction. Therefore, the angle θ formed between the rubbing direction of the plastic film F and the absorption axis A of the polarizer 11 substantially coincides with the angle formed between the rubbing direction of the plastic film F and the longitudinal direction of the plastic film F. What is necessary is just to set the inclination-angle of the rotating shaft of the rubbing roll 4 so that the rubbing direction of F and the longitudinal direction of the plastic film F may form the said predetermined angle (theta).

  As shown in FIG. 4, the backup roll mechanism 5 includes a plurality of backup rolls 51 that respectively rotate along the conveyance direction of the conveyance belt 3 (the direction indicated by the arrow A in FIG. 4A). Each backup roll 51 is disposed directly below the rubbing roll 4 and along a straight line substantially parallel to the rotation axis of the rubbing roll 4.

  As described above, the backup roll mechanism 5 that supports the lower surface of the conveyance belt 3 that supports the plastic film F is disposed directly below the rubbing roll 4 and along a straight line that is substantially parallel to the rotation axis of the rubbing roll 4. Since the plurality of backup rolls 51 are provided, the rotation axis of the rubbing roll 4 is inclined from the direction perpendicular to the conveying direction of the conveying belt 3 (for example, the straight line C1 in FIG. Even in the case of a rotating shaft, each backup roll 51 is disposed directly under the inclined rubbing roll 4 via the plastic film F and the conveyor belt 3. Furthermore, since each backup roll 51 rotates along the conveyance direction of the conveyance belt 3 (the conveyance direction of the plastic film F), the rotation of each backup roll 51 moves in the conveyance direction of the conveyance belt 3 and consequently the plastic film F. There is no hindrance to the transport. Therefore, even if the pushing amount of the rubbing roll 4 is increased in a state where the rotation axis of the rubbing roll 4 is inclined from the direction perpendicular to the conveying direction of the conveying belt 3, the flatness of the conveying belt 3 is improved and the slack is reduced. The rubbing process can be performed in a stable state without being easily generated and without disturbing the movement of the conveyor belt 3. As a result, uniform orientation characteristics can be imparted to the plastic film F, and thus the second birefringent layer 14 having uniform optical characteristics, and thus the elliptically polarizing plate 10 having uniform optical characteristics can be manufactured. It is.

  As a preferable configuration, the backup roll mechanism 5 according to the present embodiment can rotate around a pedestal portion 52 disposed along a straight line substantially parallel to the rotation axis of the rubbing roll 4 and the normal line of the surface of the conveyor belt 3. A plurality of support portions 53 pivotally supported on the pedestal portion 52 are further provided, and each backup roll 51 is pivotally supported by each support portion 53 so as to be rotatable along the transport direction of the transport belt 3. If it demonstrates more concretely, the support part 53 which concerns on this embodiment is pivotally supported by the base part 52 with the shaft member 54, and the periphery of the shaft member 54 is made rotatable. Further, the backup roll 51 according to the present embodiment is pivotally supported on the support portion 53 by the shaft member 55 and is rotatable around the shaft member 55.

  According to such a preferable configuration, the backup roll mechanism 5 is configured even if the rotation axis of the rubbing roll 4 is inclined from the direction perpendicular to the conveying direction of the conveying belt 3 (the direction of the straight line C0 in FIG. 4A). By tilting the pedestal 52 in the same manner (that is, tilting the pedestal 52 along a straight line substantially parallel to the rotation axis of the tilted rubbing roll 4), Support supported by the pedestal 52 so that the backup roll 51 supported by the support 53 is rotated along the direction of conveyance of the conveyance belt 3 (by a frictional force applied from the lower surface of the conveyance belt 3). The part 53 rotates naturally. In other words, even if the inclination angle of the rubbing roll 4 is not fixed, and the setting value of the inclination angle is changed, the backup roll 51 is rubbed only by changing the pedestal 52 to the same inclination angle as the rubbing roll 4. It is possible to make a state of being arranged immediately below the roll 4 and rotating along the conveying direction of the conveying belt 3.

  Further, as shown in FIG. 4C, the backup roll mechanism 5 according to the present embodiment has a preferable configuration in which the rotation axis of the rubbing roll 4 is inclined from the direction perpendicular to the conveyance direction of the conveyance belt 3. In addition, a coupling mechanism 56 that couples the rubbing roll 4 and the pedestal portion 52 so as to incline the pedestal portion 52 accordingly. More specifically, the coupling mechanism 56 according to the present embodiment supports the rubbing roll 4 so as to be rotatable around the rotation axis and to be vertically movable, and to support the pedestal 52. The frame is shaped like a letter, and can be rotated in the direction of the arrow B in FIG. 4C by a motor M attached to the top of the frame. When the coupling mechanism 56 is rotated in the direction of the arrow B in FIG. 4C by the motor M, the rubbing roll 4 and the pedestal portion 52 supported by the coupling mechanism 56 are rotated (inclined) by the same angle in the same direction. ). Therefore, the setting becomes extremely easy as compared with the configuration in which the rubbing roll 4 and the pedestal portion 52 are individually inclined. In the present embodiment, the configuration in which the coupling mechanism 56 is automatically rotated using the motor M has been described. However, the present invention is not limited to this, and a configuration in which the coupling mechanism 56 is manually rotated is employed. Is also possible.

  In the present embodiment, as a preferable configuration, the distance L1 between the centers of adjacent backup rolls 51 in the rotation axis direction (see FIG. 4A) is 60 mm or more and 200 mm or less (more preferably, 70 mm or more and 150 mm or less). Set to Further, the width L2 (see FIG. 4A) of each backup roll 51 in the rotation axis direction is set to 20 mm to 150 mm (more preferably 25 mm to 70 mm). In addition, the separation distance L3 (see FIG. 4A) between the adjacent backup rolls 51 is 40 mm or more and 60 mm or less (more preferably 45 mm or more and 55 mm or less), and the outer diameter of each backup roll 51 is 70 mm or more and 110 mm or less ( More preferably, the length of the pedestal portion 52 is set to 1500 mm or more and 2500 mm or less (however, a value larger than the width of the conveyor belt 3).

  When the rubbing process is performed on the plastic film F using the rubbing apparatus 100 having the above-described configuration, the end of the long plastic film F wound around a predetermined roll (not shown) has a plurality of transports. It is supplied onto the conveyor belt 3 via a roll (not shown). Then, by driving the drive rolls 1 and 2 to rotate, the conveyance belt 3 moves in the direction indicated by the arrow C in FIG. 3, and accordingly, the plastic film F is also conveyed together with the conveyance belt 3 and rubbed by the rubbing roll 4. Processing will be performed. In this manner, by using the rubbing apparatus 100, the rubbing process can be performed by roll-to-rotation, and thus the rubbing process can be performed with high manufacturing efficiency and at low cost.

  In addition, as the plastic film F to which the manufacturing method according to the present embodiment is applied, liquid crystal molecules applied to the surface by rubbing the surface or by rubbing the alignment film formed on the surface. As long as a function capable of orienting is provided, the material is not particularly limited. As the material of the plastic film F, the materials described as specific examples of the protective film 12 and the second protective film 16 in the configuration of the protective film 12 and the second protective film 16 described above can be used. The plastic film F is preferably transparent and has no color. Specifically, the thickness direction retardation value Rth [590] is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and most preferably −70 nm to +70 nm. Moreover, the thickness of the plastic film F can be set to any appropriate thickness as long as the preferable retardation value in the thickness direction can be obtained. Specifically, it 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. Furthermore, the plastic film F may be the same material as the protective film 12 and the second protective film 16, or may be different. The plastic film F is subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, an antiglare treatment, or the like as necessary.

  Examples of the alignment film formed on the surface of the plastic film F include polyvinyl alcohol, polyimide, and polyamide. Examples of the method for forming the alignment film include spin coating, bar coating, slot die coating, and dip coating.

  In general, the conveying speed of the plastic film F is 1 to 50 m / min, preferably 1 to 10 m / min, and the rotation speed of the rubbing roll 4 is 1 to 3000 rpm, Is in the range of 500 to 2000 rpm, and the pushing amount of the rubbing roll 4 is 100 to 2000 μm, preferably 100 to 1000 μm. The “pushing amount of the rubbing roll 4” means that when the position of the rubbing roll 4 is changed with respect to the surface of the plastic film F, the bristles of the raised cloth wound around the rubbing roll 4 are the plastic film first. The position in contact with the F surface is defined as the origin (0 point), which means the amount of pressing of the rubbing roll 4 from the origin toward the plastic film F (position variation).

(Birefringent layer forming process)
Liquid crystal molecules are applied to the surface of the plastic film F or the alignment film surface that has been subjected to the rubbing treatment as described above, and the second birefringence is obtained by curing or solidifying the applied liquid crystal molecules. Layer 14 is formed.

  When applying liquid crystal molecules, a solution in which a liquid crystal compound is dissolved is generally used. As the liquid crystal molecules contained in the solution, as described above, a liquid crystal polymer, a liquid crystal prepolymer, a liquid crystal monomer, and the like are appropriately used.

  When using the liquid crystal polymer, after applying the liquid crystal polymer solution to the surface of the plastic film F or the alignment film surface, heating until it reaches the temperature range showing the liquid crystal phase and drying it, the liquid crystal phase remains in the state showing By rapidly cooling to room temperature, a liquid crystal state exhibiting optical anisotropy can be fixed.

  When using a liquid crystal prepolymer or a liquid crystal monomer, these solutions are applied to the surface of the plastic film F or the surface of the alignment film, and then heated until the temperature is higher than the temperature range showing the liquid crystal phase, and then dried to show the liquid crystal phase. It is possible to fix the liquid crystal state exhibiting optical anisotropy by cooling to a state temperature and crosslinking by exposing to ultraviolet rays or the like.

  When a liquid crystal polymer is used as the liquid crystal molecule, the liquid crystal monomer solution preferably contains a polymerization agent and a crosslinking agent. These polymerizing agent and crosslinking agent are not particularly limited, and for example, the following can be used. Examples of the polymerization agent include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking. An agent can be used. Any one of these may be used, or two or more may be used in combination.

  The liquid crystal monomer solution coating solution can be prepared, for example, by dissolving and dispersing the liquid crystal monomer represented by any one of the above-described chemical formulas (1) to (16) in an appropriate solvent. Examples of the solvent include, but are not limited to, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenol, and p-chlorophenol. , Phenols such as o-chlorophenol, m-cresol, o-cresol, p-cresol, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, methoxybenzene, 1,2-dimethoxybenzene, acetone, methyl ethyl ketone (MEK), ketone solvents such as methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone, ethyl acetate, butyl acetate, acetic acid pro Ester solvents such as benzene, alcohols 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 Solvents, amide solvents such as dimethylformamide and dimethylacetamide, 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 acetate cellosolve and the like can be used. Among these, toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl acetate cellosolve are preferable. These solvents may be, for example, one kind or a mixture of two or more kinds.

  The coating liquid may be flow-deployed by a conventionally known method such as a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, a spray coating method, Among these, the spin coat method and the extrusion method are preferable from the viewpoint of coating efficiency.

  The temperature condition of the heat treatment after the coating liquid of the liquid crystal monomer solution is applied to the surface of the plastic film F or the alignment film is, for example, the type of the liquid crystal monomer to be used, specifically the temperature at which the liquid crystal monomer exhibits liquid crystallinity. Although it can determine suitably according to it, it is the range of 40-120 degreeC normally, Preferably it is the range of 50-100 degreeC, More preferably, it is the range of 60-90 degreeC. If the temperature is 40 ° C. or higher, the liquid crystal monomer can usually be sufficiently aligned, and if the temperature is 120 ° C. or lower, for example, the choice of the plastic film F is widened in terms of heat resistance. .

  The liquid crystal compound to be dissolved is not particularly limited as long as it can be applied. For example, a rod-like liquid crystal compound, a flat liquid crystal compound, or a polymer thereof is used. More specifically, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, Liquid crystal compounds such as phenyldioxanes, tolanes, alkenylcyclohexylbenzonitriles, and polymers thereof are preferably used.

  As described above, the liquid crystal molecules are applied to the surface of the plastic film F or the alignment film surface, and the applied liquid crystal molecules are cured or solidified, whereby liquid crystals are aligned along the rubbing direction of the plastic film F. Since the sex molecules are oriented, the direction of the slow axis B (see FIG. 2) of the formed second birefringent layer 14 is substantially the same as the rubbing direction of the plastic film F.

(Transfer process)
The second birefringent layer 14 formed on the surface of the plastic film F as described above is transferred to the surface of the first birefringent layer 13 formed on the protective film 12. The transfer method is not particularly limited. For example, the first birefringent layer 14 formed on the surface of the plastic film F is formed on the protective film 12 via an adhesive or an adhesive. Bonding with the birefringent layer 13 can be performed by peeling the plastic film F from the second birefringent layer 14. A typical example of the pressure-sensitive adhesive is an acrylic pressure-sensitive 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 urethane resin, epoxy resin, isocyanate resin, and polyimide resin. Specific examples of the moisture curable adhesive include isocyanate resin-based moisture curable adhesive. 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 hardening, the 1st and 2nd birefringent layers 13 and 14 are not heated at the time of bonding (adhesion). For this reason, there is no risk of heat shrinkage, and even when the first and second birefringent layers 13 and 14 are extremely thin, it is possible to remarkably prevent cracks and the like from occurring during bonding. is there. The isocyanate resin adhesive is a general term for polyisocyanate adhesives and polyurethane resin adhesives.

  As described above, the second birefringent layer 14 is formed on the rubbed plastic film F, and then transferred from the plastic film F to the first birefringent layer 13, so that the elliptically polarizing plate is obtained. 10 does not include the rubbed plastic film F. Thus, since the circularly polarizing plate 10 does not include the rubbed plastic film F, according to the manufacturing method of this embodiment, the thickness of the elliptically polarizing plate 10 can be significantly reduced.

<Polarizer and second protective film lamination step>
Lamination of the polarizer 11 on the surface of the protective film 12 where the first birefringent layer 13 is not formed and the second protective film 16 on the surface of the polarizer 11 where the protective film 12 is not formed is performed in this embodiment. It can be carried out at any appropriate time in the method of manufacturing the elliptically polarizing plate 10 according to the embodiment. For example, lamination | stacking of the polarizer 11 and the 2nd protective film 16 can be implemented at the time of following (1)-(3).
(1) Before the first birefringent layer forming step The polarizer 11 and the second protective film 16 are laminated in advance on the protective film 12 (before the first birefringent layer 13 is transferred to the protective film 12). deep. In this case, the first birefringent layer 13 is transferred to the surface on the protective film 12 side of the laminate composed of the protective film 12 / polarizer 11 / second protective film 16.
(2) Between the first birefringent layer forming step and the second birefringent layer forming step After transferring the first birefringent layer 13 to the protective film 12, the first birefringent layer 13 of the protective film 12 The polarizer 11 and the second protective film 16 are laminated on the surface on which no is formed. In this case, the second birefringent layer 14 is transferred to the first birefringent layer 13 side surface of the laminate composed of the first birefringent layer 13 / protective film 12 / polarizer 11 / second protective film 16. Will do.
(3) Between the second birefringent layer forming step and the third birefringent layer forming step After the second birefringent layer 14 is transferred to the first birefringent layer 13, the first birefringent layer of the protective film 12 is transferred. The polarizer 11 and the second protective film 16 are laminated on the surface on which the refractive layer 13 is not formed. In this case, the second birefringent layer 14 side of the laminate composed of the second birefringent layer 14 / first birefringent layer 13 / protective film 12 / polarizer 11 / second protective film 16 is arranged on the second birefringent layer 14 side. 3 birefringent layers 15 are laminated.
(4) After the third birefringent layer forming step After forming a laminate composed of the third birefringent layer 15 / the second birefringent layer 14 / the first birefringent layer 13 / the protective film 12, The polarizer 11 and the second protective film 16 are laminated on the surface of the laminate on the protective film 12 side.

  As a method for laminating the polarizer 11 and the second protective film 16 to the protective film 12, any suitable laminating method (for example, adhesion) can be used. Adhesion is performed using any suitable adhesive or adhesive. The type of adhesive or pressure-sensitive adhesive can be appropriately selected according to the type of adherend (that is, the polarizer 11, the protective film 12, and the second protective film 16). 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.

  According to the manufacturing method according to the present embodiment, as described above, the slow axis B of the second birefringent layer 14 is adjusted by adjusting the inclination angle of the rubbing roll 4 in the rubbing treatment process of the plastic film F. Since it can set, the polarizer 11 can use the elongate polarizing film extended | stretched to the longitudinal direction (namely, which has the absorption axis A in a longitudinal direction). That is, the long plastic film F and the long polarizer 11 that are rubbed so that the rubbing direction (orientation direction) forms a predetermined angle with respect to the longitudinal direction are aligned in the longitudinal direction. Can be continuously bonded in a roll-to-roll manner. Therefore, the elliptically polarizing plate 10 can be obtained with extremely excellent production efficiency. Furthermore, according to the manufacturing method which concerns on this embodiment, it is not necessary to cut out and laminate | stack the plastic film F and the polarizer 11 in which the 2nd birefringent layer 14 was formed in the diagonal direction with respect to the longitudinal direction. For this reason, in each cut-out film, it is hard to produce dispersion | variation in the orientation direction and the direction of an absorption axis, and the elliptically polarizing plate 10 with few dispersion | variation in quality between products as a result is obtained. Furthermore, since no waste is produced by cutting out, the elliptically polarizing plate 10 can be obtained at low cost, and the manufacture of the large elliptically polarizing plate 10 is facilitated.

<Third birefringent layer forming step>
In this step, the third birefringent layer 15 is formed on the surface of the second birefringent layer 14 transferred onto the first birefringent layer 13. The third birefringent layer 15 is formed by laminating a polymer film on the surface of the second birefringent layer 14. Preferably, the polymer film is a stretched film. More specifically, the polymer film is a film stretched in the width direction. Since such a stretched film has a slow axis in the width direction, when such a stretched film is laminated on the second birefringent layer 14, the slow axis of the third birefringent layer 15 is the polarizer 11. It is substantially orthogonal to the absorption axis (longitudinal direction). The laminating method is not particularly limited, and any appropriate adhesive or pressure-sensitive adhesive (for example, as described above, the adhesive or pressure-sensitive adhesive that can be used for laminating the protective film 12 and the polarizer 11) is used. It can be carried out. As described above, the elliptically polarizing plate 10 of the present embodiment is obtained.

III. Next, the use of the elliptically polarizing plate 10 will be described.

<Use of elliptical polarizing plate>
The elliptically polarizing plate 10 is 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 10 is used in a liquid crystal display device, it is useful for viewing angle compensation, for example. The elliptically polarizing plate 10 is used in, for example, a circular polarization mode liquid crystal display device, and is particularly suitable for 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. Useful. Moreover, when using the elliptically polarizing plate of this invention for EL display, it is useful for electrode reflection prevention, for example.

<Image display device>
A liquid crystal display device will be specifically described as an example of an image display device to which the elliptically polarizing plate 10 according to the present embodiment is applied. Here, only the configuration of the liquid crystal panel included in the liquid crystal display device will be described, but any other appropriate configuration may be adopted depending on the purpose for other configurations included in the liquid crystal display device. FIG. 5 is a schematic cross-sectional view of the liquid crystal panel. As shown in FIG. 5, the liquid crystal panel 300 is disposed on the outside of the liquid crystal cell 20, the retardation plates 30 and 30 ′ disposed on both sides of the liquid crystal cell 20, and the respective retardation plates 30 and 30 ′. And polarizing plates 10 and 10 '. As the retardation plates 30 and 30 ', any appropriate retardation plate is 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 an elliptically polarizing plate according to this embodiment. The polarizing plate 10 ′ is any appropriate polarizing plate. The polarizing plates 10, 10 ′ are typically arranged so that their absorption axes are orthogonal to each other. As shown in FIG. 5, in the liquid crystal panel 300, the elliptically polarizing plate 10 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 21 and 21 ′. 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 switching 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.

  Hereinafter, the features of the present invention will be further clarified by showing examples and comparative examples.

<Example 1>
(1) Production of Laminate Consisting of First Birefringent Layer / Protective Film The following chemical formula (numbers 65 and 35 in the formula indicate the mol% of the monomer unit and are represented by a block polymer for convenience: weight average 20 parts by weight of a side chain type liquid crystal polymer having a molecular weight of 5000), 80 parts by weight of a polymerizable liquid crystal having a nematic liquid crystal phase (manufactured by BASF: trade name Palicolor LC242) and a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name) Irgagua 907) 5 parts by weight was dissolved in 400 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. And after applying the said coating liquid to a TAC film (Fuji Photo Film company make, thickness 40 micrometers: It becomes a protective film) with a bar coater, the liquid crystal was orientated by heat-drying at 90 degreeC for 2 minutes. The liquid crystal layer was irradiated with ultraviolet light to cure the liquid crystal layer, thereby preparing a first birefringent layer / protective film laminate. The in-plane retardation value Re [590] of the first birefringent layer was substantially zero, the retardation value Rth [590] in the thickness direction was −68 nm, and the thickness was 0.7 μm. The thickness direction retardation value Rth [590] of the protective film was 59 μm. In addition, the spectrophotometer: MCPD2000 made from Otsuka Electronics was used for the thickness measurement of a protective film and a 1st birefringent layer. The in-plane retardation value Re [590] of the first birefringent layer and the retardation value Rth [590] in the thickness direction of the first birefringent layer and the protective film are calculated using an automatic birefringence measuring device (Oji Scientific Instruments). (Manufactured by company: automatic birefringence meter KOBRA31PR) at a measurement temperature of 23 ° C. and a measurement wavelength of 590 nm.

(2) Production of a rubbed plastic film A polyethylene terephthalate film is used as a plastic film, and a film in which polyvinyl alcohol (PVA) having a thickness of 1.0 μm is formed as an alignment film on the plastic film surface is shown in FIGS. The rubbing process was performed using the rubbing apparatus 100 shown in FIG. The mirror finish on the surface of the transport belt 3 is Ra = 0.01 μm, the outer diameters of the drive rolls 1 and 2 are 550 mm, the transport speed of the film is 5 m / min, and the outer diameters of the backup rolls 51 are all 90 mm. The center-to-center distance L1 in the rotation axis direction of the backup rolls 51 is 80 mm, and the width L2 in the rotation axis direction of each backup roll 51 is 30 mm. The radius of the rubbing roll 4 (including the raised cloth 4a) was 76.89 mm, and a roll of a rayon raised cloth was used. The rotation axis of the rubbing roll 4 is inclined 22.5 ° from the direction perpendicular to the film transport direction, and each backup roll 51 is arranged directly below the rubbing roll 4 and along a straight line parallel to the rotation axis. did. The number of rotations of the rubbing roll 4 was 1500 rpm, and the pushing amount was 0.4 mm. For measuring the thickness of the alignment film, a spectrophotometer: MCPD2000 manufactured by Otsuka Electronics was used.

(3) Production of a laminate comprising a second birefringent layer / plastic film 10 g of a polymerizable liquid crystal compound (manufactured by BASF: trade name “Pariocolor LC242”) showing a nematic liquid crystal layer and initiation of photopolymerization for this polymerizable liquid crystal compound 0.5 g of an agent (manufactured by Ciba Specialty Chemicals Co., Ltd .: trade name “Irgacure 907”) was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

And after apply | coating said coating liquid with the bar coater on the orientation film | membrane surface which gave the rubbing process of the plastic film produced as mentioned above, a liquid crystal is orientated by heat-drying for 2 minutes at 90 degreeC. I let you. A positive uniaxial film having a refractive index characteristic of nx> ny = nz by irradiating the liquid crystal layer thus formed with 20 mJ / cm ² of light using a metal halide lamp and curing the liquid crystal layer. A second birefringent layer was formed. The thickness of the second birefringent layer and the in-plane retardation value Re [590] are adjusted by changing the coating amount of the coating liquid, the thickness is 2.2 μm, and the in-plane retardation value Re [590]. Was 250 nm. Note that a spectrophotometer: MCPD2000 manufactured by Otsuka Electronics Co., Ltd. was used for measuring the thickness of the second birefringent layer. The in-plane retardation value Re [590] of the second birefringent layer is measured with an automatic birefringence measuring device (manufactured by Oji Scientific Instruments: automatic birefringence meter KOBRA31PR) at a measurement temperature of 23 ° C. and a measurement wavelength of 590 nm. did.

(4) Production of Laminate Consisting of Second Birefringent Layer / First Birefringent Layer / Protective Film The second birefringent layer formed on the plastic film as described above is passed through an acrylic adhesive. It transferred to the laminated body which consists of a 1st birefringent layer / protective film, and produced the laminated body which consists of a 2nd birefringent layer / first birefringent layer / protective film.

(5) Preparation of laminate comprising second birefringent layer / first birefringent layer / protective film / polarizer / second protective film After polyvinyl alcohol film is dyed in an aqueous solution containing iodine, boron A polarizer was produced by uniaxially stretching six times between rolls having different speed ratios in an aqueous solution containing an acid. This polarizer, a TAC film (thickness 40 μm) as a second protective film, and a laminate composed of the second birefringent layer / first birefringent layer / protective film are laminated using an adhesive ( The absorption axis direction of the polarizer is the longitudinal direction, and the angle formed by the absorption axis of the polarizer and the slow axis of the second birefringent layer is 22.5 ° or -22.5 °), and the second A laminate composed of a birefringent layer / first birefringent layer / protective film / polarizer / second protective film was produced. The first birefringent layer has no in-plane anisotropy and no slow axis. Therefore, polarizers can be stacked at any angle.

(6) Production of elliptically polarizing plate A norbornene-based film (manufactured by Nippon Zeon Co., Ltd., trade name: ZEONOR: thickness 60 μm) is uniaxially stretched 1.5 times at 138 ° C. to obtain a third birefringent layer having a thickness of 39 μm. It was. This birefringent layer had a refractive index distribution of nx>ny> nz, and its in-plane retardation value Re [590] was 120 μm and the Nz coefficient was 1.6. The third birefringent layer is bonded to a laminate composed of the second birefringent layer / first birefringent layer / protective film / polarizer / second protective film via an acrylic pressure-sensitive adhesive. An elliptically polarizing plate comprising a third birefringent layer / second birefringent layer / first birefringent layer / protective film / polarizer / second protective film was produced. Note that a spectrophotometer: MCPD2000 manufactured by Otsuka Electronics Co., Ltd. was used for measuring the thickness of the third birefringent layer. Further, the in-plane retardation value Re [590] and the Nz coefficient of the third birefringent layer are measured with an automatic birefringence measuring device (manufactured by Oji Scientific Instruments: automatic birefringence meter KOBRA31PR) at a measurement temperature of 23 ° C. and a measurement wavelength. Measurements were taken at 590 nm.

<Comparative Example 1>
In the rubbing process, a rubbing apparatus 100A shown in FIG. 6 (a plurality of (five) rod-shaped backup rolls 5A that are arranged substantially parallel to each other on the lower surface of the conveyor belt 3 and rotate in the conveying direction of the conveyor belt 3) An elliptically polarizing plate was prepared in the same manner as in Example 1 except that the structure supported by the above was used.

<Comparative example 2>
The elliptically polarizing plate of Comparative Example 2 was prepared according to Example 1 except that the first birefringent layer was not formed.

<Evaluation results>
(1) Flatness evaluation of conveyance belt About the rubbing processing apparatus used in Example 1 and Comparative Examples 1 and 2, the flatness of the conveyance belt 3 was evaluated. Specifically, the dimension of the gap between the rubbing roll 4 and the conveying belt 3 was sequentially measured at a plurality of locations along the rotation axis direction of the rubbing roll 4 using a gap gauge. Then, the difference between the maximum value and the minimum value of the gap measured along the rotation axis direction of the rubbing roll 4 was evaluated as the flatness of the surface of the conveyor belt 3.

  As a result of the evaluation, the rubbing processing apparatus 100A used in Comparative Example 1 has a flatness of 130 μm, whereas the rubbing processing apparatus 100 used in Example 1 and Comparative Example 2 has a flatness of 50 μm. It was found that the flatness of the conveyor belt 3 is improved when the apparatus 100 is used.

(2) Evaluation of the number of bright spots Lamination made of the second birefringent layer / plastic film produced in Example 1 and Comparative Examples 1 and 2 between two polarizing plates arranged so that their absorption axes are orthogonal to each other It was visible by visually checking the laminated body so that the absorption axis of the polarizing plate on the viewing side and the slow axis of the laminate (the slow axis of the second birefringent layer) were parallel to each other. The number of bright spots was evaluated. The number of bright spots was counted in a 10 cm × 10 cm region on the surface of the laminate, and this number was evaluated by proportionally converting the number per 1 m 2. In addition, the bright spots that were visible for the second birefringent layer / plastic film laminate remained substantially after the second birefringent layer was transferred to the first birefringent layer to produce an elliptically polarizing plate. Confirmed to do.

(3) Evaluation of Contrast About the laminate in which the elliptically polarizing plates of Example 1 are overlapped, the laminate in which the elliptically polarizing plates of Comparative Example 1 are overlapped, and the laminate in which the elliptically polarizing plates of Comparative Example 2 are overlapped, Illuminate the laminate with a backlight to display a white image (absorption axis of the polarizer is parallel) and a black image (absorption axis of the polarizer are orthogonal), and the polarized light on the viewing side by the product name “EZ Contrast 160D” manufactured by ELDIM. The scanning was performed in the direction of 45 ° to 135 ° with respect to the absorption axis of the child and from −60 ° to 60 ° with respect to the normal line. 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.

Table 1 shows the evaluation results of the above (2) and (3).

  As shown in Table 1, the laminate composed of the second birefringent layer / plastic film produced in Example 1 and Comparative Example 2 has a number of bright spots of 5, and the second composite produced in Comparative Example 1 has the number of bright spots. The laminate composed of the refractive layer / plastic film had 15 bright spots. This is considered that the orientation characteristics of the plastic film according to Example 1 and Comparative Example 2 are more uniform than the orientation characteristics of the plastic film according to Comparative Example 1, and the adhesion of foreign matters due to this is reduced. .

  Further, as shown in Table 1, regarding the contrast, each laminated body in which the elliptically polarizing plates according to Example 1 and Comparative Example 1 are stacked has a minimum angle of 40 degrees and a maximum of 50 degrees in all directions with a contrast of 10 or more. The minimum and maximum difference was 10 degrees. An angle with a contrast of 10 or more being at least 40 degrees in all directions is a level that does not cause a problem in practice (Evaluation A). On the other hand, the laminated body on which the elliptically polarizing plates according to Comparative Example 2 were stacked had an angle with a contrast of 10 or more at a minimum of 30 degrees, a maximum of 50 degrees, and a minimum maximum difference of 20 degrees in all directions. An angle with a contrast of 10 or more being a minimum of 30 degrees in all directions is a level not practically used (evaluation B).

  From the above, it was found that the elliptically polarizing plate according to Example 1 has relatively uniform alignment characteristics and has a level of no problem in practical use.

It is sectional drawing which shows schematic structure of the elliptically polarizing plate manufactured by the manufacturing method which concerns on this embodiment. It is a disassembled perspective view explaining the relationship between the absorption axis of each layer which comprises the elliptically polarizing plate shown in FIG. 1, and a slow axis. FIG. 3 is a front view showing a schematic configuration of a rubbing processing apparatus for performing the rubbing processing step. 4 is a diagram showing a schematic configuration of the backup roll mechanism shown in FIG. 3. FIG. 4 (a) is a plan view, FIG. 4 (b) is a perspective view in the vicinity of the backup roll, and FIG. The figure seen from the conveyance direction of a long plastic film is shown, respectively. FIG. 5 is a schematic cross-sectional view of a liquid crystal panel to which an elliptically polarizing plate is applied. FIG. 6 is a perspective view showing a schematic configuration of a rubbing apparatus according to a comparative example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Drive roll 3 ... Conveyor belt 4 ... Rubbing roll 4a ... Raised cloth 5 ... Backup roll mechanism 10 ... Elliptical polarizing plate 11 ... Polarizer 12 ... Protective film 13 ... 1st birefringent layer 14 ... 2nd compound Refractive layer 15 ... third birefringent layer 16 ... second protective film 51 ... backup roll 52 ... pedestal part 53 ... support part 56 ... coupling mechanism 100 ... rubbing device 300 ... liquid crystal panel F ... plastic film M ... motor

Claims (5)

A first birefringent layer forming step of forming a first birefringent layer having a refractive index characteristic of nz> nx = ny on the protective film;
A second birefringent layer forming step of forming a second birefringent layer having a refractive index characteristic of nx> ny = nz on the first birefringent layer;
Forming a third birefringent layer having a refractive index characteristic of nx>ny> nz on the second birefringent layer;
A polarizer laminating step of laminating a polarizer on the surface of the protective film on which the first birefringent layer is not formed,
The second birefringent layer forming step includes:
A rubbing treatment step in which the surface of the long plastic film is rubbed by a rubbing roll having a rotation axis inclined from a direction perpendicular to the plastic film conveyance direction;
A liquid crystal molecule is applied to the surface of the plastic film that has undergone the rubbing treatment step, the applied liquid crystal molecule is fixed, and a second refractive index characteristic of nx> ny = nz is formed on the plastic film. A birefringent layer forming step of forming a birefringent layer;
Transferring the second birefringent layer formed on the plastic film onto the first birefringent layer,
In the rubbing treatment step, the long plastic film is supported and transported by a transport belt having a metal surface, and a backup roll mechanism that supports the lower surface of the transport belt that supports the plastic film is disposed.
The backup roll mechanism includes a plurality of backup rolls that respectively rotate along the conveyance direction of the conveyance belt,
Each of the plurality of backup rolls is disposed directly along a straight line that is directly below the rubbing roll and substantially parallel to the rotation axis of the rubbing roll.   2. The method of manufacturing an elliptically polarizing plate according to claim 1, wherein the second birefringent layer functions as a half-wave plate, and the third birefringent layer functions as a quarter-wave plate. .   The ratio B / A of the absolute value B of the retardation value Rth [590] in the thickness direction of the first birefringent layer to the absolute value A of the retardation value Rth [590] in the thickness direction of the protective film is 1 3. The method for producing an elliptically polarizing plate according to claim 1, wherein 1 ≦ B / A ≦ 4.0 is satisfied. The backup roll mechanism is
A pedestal portion disposed along a straight line substantially parallel to the rotation axis of the rubbing roll;
A plurality of support portions pivotally supported on the pedestal portion so as to be rotatable around a normal line of the surface of the conveyor belt;
4. The elliptically polarized light according to claim 1, wherein each of the plurality of backup rolls is pivotally supported by each of the plurality of support portions so as to be rotatable along a conveyance direction of the conveyance belt. A manufacturing method of a board.   The backup roll mechanism includes the rubbing roll and the pedestal portion so that when the rotation axis of the rubbing roll is inclined from a direction perpendicular to the conveying direction of the conveying belt, the pedestal portion is also inclined accordingly. The manufacturing method of the elliptically polarizing plate of Claim 4 further equipped with the connection mechanism which connects with.