JP2004199045A - Optical film and liquid crystal display using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elliptical polarizing board efficiently manufacturable while having a polarizing layer and a birefractive layer. <P>SOLUTION: This elliptical polarizing board 10 is composed by laminating the polarizing layer 13 converting incident natural light into linear polarized light, an optically rotary layer 12 rotating the linear polarized light converted by the polarizing layer 13, and the birefractive layer 11 converting the linear polarized light into elliptical polarized light. The birefractive layer 11 and polarizing layer 13 are arranged so that a phase lagging axis of the birefractive layer 11 is parallel to an absorption axis of the polarizing layer 13. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an optical film having not only a polarizing layer but also a birefringent layer, and a liquid crystal display device including the same.

  2. Description of the Related Art Liquid crystal display devices are widely used for display screens of personal computers, PDAs, mobile phones, and the like because they are lightweight and thin and feature high contrast, high brightness, and low power consumption. In a liquid crystal display device, in order to further increase the contrast, widen the viewing angle, and increase the brightness of the display, not only a polarizing plate but also various birefringent films on the display surface and means for improving them have been proposed. . For example, as an optical compensator for an STN (Super Twisted Nematic) type liquid crystal display device, prevention of coloring and improvement of contrast have been achieved. In addition, a reflective or semi-transmissive liquid crystal display device having a reflector inside a liquid crystal display panel, regardless of STN, TN, or ECB, utilizes the property of circularly polarized light, so that the front, back, or both surfaces are used. Circularly polarizing plate (optical film) in which a birefringent film having a phase difference of λ / 4 is attached to the polarizing plate of (1). Thus, an elliptically polarizing plate combining such a polarizing plate and a birefringent film is currently used not only in the STN type but also in all liquid crystal display devices.

  By the way, the polarizing plate is composed of three layers of a polarizer having an optical function and a protective film for protecting the polarizer from both sides. Polarizers are usually made by adsorbing iodine or a dichroic dye having a dichroic function on a polyvinyl alcohol (PVA) film formed, cross-linking with a boron compound or the like, and then stretching vertically or uniaxially, such as between rolls. It is configured with The protective film is composed of a film of triacetyl cellulose roll (TAC) or norbornene-based resin having excellent heat stability and moisture barrier properties. The polarizing plate is manufactured as a film in which a protective film is bonded to both surfaces of the polarizer via an adhesive, and the protective film is wound into a roll. Here, since the direction of the absorption axis of the polarizing plate coincides with the stretching direction of the polarizer, it becomes the roll flow direction (MD direction).

  Further, the birefringent film is made of a thermoplastic film such as a polycarbonate-based resin or a norbornene-based resin, which is formed by subjecting a longitudinal stretch such as a roll stretch or a roll stretch or a transverse stretch by a tenter to a roll-shaped film. Manufactured as Here, since the direction of the slow axis of the birefringent film coincides with the stretching direction, it becomes the roll flow direction (MD direction) in the case of longitudinal stretching, and becomes the orthogonal direction (TD direction) in the case of transverse stretching. . The slow axis direction of the birefringent film is a case having a positive optical anisotropy, and the opposite is applied to a substance having a negative optical anisotropy.

  An elliptically polarizing plate obtained by laminating a polarizing plate and a birefringent film can completely obtain the effect of the birefringent film when the absorption axis of the polarizing plate and the slow axis of the birefringent film are parallel or orthogonal. And only functions as a polarizing plate. Therefore, in such an elliptically polarizing plate, the polarizing plate and the birefringent film are bonded so that the absorption axis of the polarizing plate and the slow axis of the birefringent film intersect at an angle other than parallel or orthogonal. Therefore, by performing the roll-to-roll lamination to pull out the polarizing plate and the birefringent film from the roll of the polarizing plate and the roll of the birefringent film wound in a roll shape as described above, respectively, and continuously bond them. An elliptically polarizing plate cannot be manufactured.

  The current method for manufacturing an elliptically polarizing plate is to cut the polarizing plate and the birefringent film drawn from the roll into a sheet shape so that each has a predetermined optical axis angle, and then bond the sheet and the sheet, or In this method, only one of the polarizing plate and the retardation film is pulled out from a roll and cut into sheets, and the sheet is bonded to a film drawn from the other roll. This method has problems that the production efficiency is low and the utilization efficiency of the film is very low.

  It is also conceivable to make a polarizing plate or a birefringent film obliquely stretched. However, since a very complicated force acts, the uniaxiality of the optical axis is poor, and the characteristics of the elliptically polarizing plate are not in-plane. It is conceivable that they become uniform.

Further, Patent Documents 1 and 2 below disclose an optical compensation film in which a polarizing plate, an optical rotation layer, and a birefringent film are sequentially laminated. However, these documents are films that compensate not only for the birefringence of a birefringent liquid crystal display panel such as STN but also for the optical rotation, which is significantly different from the object of the present invention described later. There is no description of the relationship between the axis and the slow axis of the birefringent layer.
JP-A-6-75214 JP-A-6-75221

  An object of the present invention is to provide an optical film that can be efficiently manufactured while having a polarizing layer and a birefringent layer, and a liquid crystal display device including the optical film.

The optical film of the present invention that solves the above-mentioned problems includes a polarizing layer that converts incident natural light into linearly polarized light, an optical rotation layer that rotates the linearly polarized light converted by the polarizing layer, and a linear rotation that is rotated by the optical rotation layer. And a birefringent layer that converts polarized light into elliptically polarized light,
The polarizing layer and the birefringent layer are provided so that the absorption axis of the polarizing layer and the slow axis of the birefringent layer are parallel or perpendicular to each other.

  According to such an optical film, since the optical rotation layer is provided between the polarizing layer and the birefringent layer, the absorption axis of the polarizing layer and the slow axis of the birefringent layer are parallel or orthogonal. Nevertheless, the linearly polarized light from the polarizing layer can be rotated by the optical rotation layer and converted into elliptically polarized light by the birefringent layer. Then, such an optical film is continuously drawn out by pulling out a polarizing plate and a birefringent film from a roll of a polarizing plate and a roll of a birefringent film wound in a roll shape, respectively, so that an optical rotation layer is provided therebetween. By performing roll-to-roll bonding in which they are bonded to each other, efficient production can be achieved.

  Here, “elliptically polarized light” includes “circularly polarized light”.

The liquid crystal display device of the present invention using the optical film of the present invention includes a liquid crystal display panel for displaying an image and an optical film provided so as to be laminated on at least one side of the liquid crystal display panel. So,
The optical film, a polarizing layer, an optical rotation layer, and a birefringent layer are laminated, the polarizing layer and the birefringent layer, the absorption axis of the polarizing layer and the slow axis of the birefringent layer. Are provided so as to be parallel or orthogonal.

  According to such a liquid crystal display device, since the optical rotation layer is provided between the polarizing layer and the birefringent layer, the absorption axis of the polarizing layer and the slow axis of the birefringent layer are parallel or orthogonal. However, the linearly polarized light from the polarizing layer can be converted to elliptically polarized light by the birefringent layer.

  In the liquid crystal display device of the present invention, the outer shape of the liquid crystal display panel is rectangular, and the absorption axis of the polarizing layer of the optical film is provided along any one of the sides of the liquid crystal display panel. May be.

  According to such a liquid crystal display device, there is no need to cut a long optical film manufactured by roll-to-roll bonding so as to have an angle with respect to the length direction, which causes waste. In addition, the optical film for each liquid crystal display panel can be cut out. Further, if the roll of the polarizing plate and the roll of the birefringent film are previously slit to match the width of the liquid crystal display panel, and they are roll-to-roll bonded to produce an optical film base, the liquid crystal can be obtained. The optical film can be attached to the display panel by a labeler method, and a liquid crystal display device can be efficiently manufactured.

Another optical film of the present invention that solves the above problems, a polarizing layer that converts incident natural light into linearly polarized light, an intermediate birefringent layer that rotates the linearly polarized light converted by the polarizing layer, and the intermediate birefringent layer An outer birefringent layer that converts linearly polarized light rotated by 楕 円 to elliptically polarized light, and is laminated,
The polarizing layer and the outer birefringent layer are provided such that the absorption axis of the polarizing layer and the slow axis of the outer birefringent layer are parallel or orthogonal to each other. .

  According to such an optical film, since the intermediate birefringent layer is provided between the polarizing layer and the outer birefringent layer, the absorption axis of the polarizing layer is parallel to the slow axis of the outer birefringent layer, or Despite being orthogonal, the linearly polarized light from the polarizing layer can be rotated by the intermediate birefringent layer to be elliptically polarized by the outer birefringent layer. Such an optical film is obtained by drawing a polarizing plate and an outer birefringent film from a roll of a polarizing plate and a roll of an outer birefringent film wound in a roll shape, respectively, and forming an intermediate birefringent film having no stretching axis therebetween. An elliptically polarizing plate capable of producing any elliptically polarized light by sticking a refraction layer can be efficiently manufactured by performing roll-to-roll sticking.

  Here, “elliptically polarized light” includes “circularly polarized light”. The intermediate birefringent layer may have a retardation of a half wavelength of a reference wavelength (a wavelength to be emphasized: 460 nm or 550 nm, for example). Further, the crossing angle θ between the absorption axis of the polarizing layer and the slow axis of the intermediate birefringent layer is 1/1 / α of the angle at which the linearly polarized light converted by the polarizing layer is rotated to the angle at which it is desired to enter the outer birefringent layer. 2 may be set (θ = α / 2).

  In another optical film of the present invention, the intermediate birefringent layer may be formed of a liquid crystal polymer coating layer.

  According to the above configuration, since the liquid crystal polymer is formed using the coating layer, the alignment direction (optical axis direction) of the liquid crystal can be set arbitrarily with respect to the flow direction of the roll, and the roll-to-roll bonding which is the subject of the present application is performed. be able to. Uniaxial liquid crystal (for example, nematic liquid crystal) is preferable as the liquid crystal polymer.

Another liquid crystal display device of the present invention using the other optical film of the present invention, a liquid crystal display panel for image display, and an optical film provided to be laminated on at least one side of the liquid crystal display panel, Provided,
The optical film, a polarizing layer, an intermediate birefringent layer, and an outer birefringent layer are laminated, the polarizing layer and the outer birefringent layer, the absorption axis of the polarizing layer and the outer birefringent layer Are provided so as to be parallel or orthogonal to the slow axis.

  According to such a liquid crystal display device, since the intermediate birefringent layer is provided between the polarizing layer and the outer birefringent layer, the absorption axis of the polarizing layer and the slow axis of the outer birefringent layer are parallel, Alternatively, despite being orthogonal, the linearly polarized light from the polarizing layer can be made elliptically polarized by the outer birefringent layer.

  Here, the intermediate birefringent layer may have a retardation of a half wavelength of a reference wavelength (a wavelength to be emphasized: 460 nm or 550 nm, for example). In addition, the intersection angle θ between the absorption axis of the polarizing layer and the slow axis of the intermediate birefringent layer is 1/1 / the angle α at which the linearly polarized light converted by the polarizing layer is rotated to an angle at which it is desired to enter the outer birefringent layer. 2 may be set (θ = α / 2).

  In another liquid crystal display device of the present invention, the outer shape of the liquid crystal display panel is rectangular, and the absorption axis of the polarizing layer of the optical film is provided along any one of the sides of the liquid crystal display panel. It may be.

  According to such a liquid crystal display device, there is no need to cut a long optical film manufactured by roll-to-roll bonding so as to have an angle with respect to the length direction, which causes waste. In addition, the optical film for each liquid crystal display panel can be cut out. Further, if the roll of the polarizing plate and the roll of the birefringent film are previously slit to match the width of the liquid crystal display panel, and they are roll-to-roll bonded to produce an optical film base, the liquid crystal can be obtained. The optical film can be attached to the display panel by a labeler method, and a liquid crystal display device can be efficiently manufactured.

  As described above, in the case of the optical film of the present invention, the polarizing plate and the birefringent film are respectively pulled out from the roll of the polarizing plate and the roll of the birefringent film wound in a roll shape, and an optical rotation layer is provided therebetween. By performing roll-to-roll bonding in which they are continuously bonded in such a manner that they can be manufactured efficiently.

  According to another optical film of the present invention, a polarizing plate and an outer birefringent film are respectively drawn from a roll of a polarizing plate and a roll of an outer birefringent film wound in a roll shape, and a stretching axis is provided between them. An elliptically polarizing plate capable of producing arbitrary elliptically polarized light by laminating an intermediate birefringent layer to be produced can be efficiently produced by performing roll-to-roll lamination.

(Embodiment 1)
The elliptically polarizing plate 10 according to the first embodiment of the present invention will be described in detail with reference to the drawings. In the first embodiment, the elliptically polarizing plate 10 is used. However, a circularly polarizing plate may be used.

  FIG. 1 is a cross-sectional view of an elliptically polarizing plate (optical film) 10 according to Embodiment 1 of the present invention. FIG. 2A is a diagram showing the optical axis arrangement of the elliptically polarizing plate 10 (a plan view as viewed from the polarizing layer side).

  The elliptically polarizing plate 10 has a configuration in which a birefringent layer 11, an optical rotation layer 12, and a polarizing layer 13 are sequentially laminated via an adhesive layer 14 (or an adhesive layer).

  The birefringent layer 11 is formed by stretching an unstretched resin film (raw film) made of a thermoplastic resin such as a polycarbonate resin, a norbornene resin, a polysulfone resin, a polyarylate resin, a polyester resin, and a cellulose resin. It is composed of As the raw film, a film produced by a solvent casting method having excellent uniformity such as thickness is usually used. As the stretching method, for example, a stretching method such as a longitudinal uniaxial stretching method between rolls, a tenter horizontal uniaxial stretching method, a longitudinal uniaxial stretching method between rolls is used, but a tenter stretching method capable of high uniform stretching and a stretching method between rolls are preferably used. Can be Further, a biaxial birefringent film which is stretched twice in the longitudinal direction and the transverse direction by these stretching methods may be used.

  The optical rotation layer 12 can be formed by laminating birefringent films as shown in JP-A-10-90521, but is not preferable because the number of layers is increased. As the optical rotation layer 12, it is preferable to use an optical rotation film made of a chiral nematic liquid crystal satisfying Morgan's conditions. As the liquid crystal polymer material satisfying the Morgan condition used for the optical rotation layer 12, a predetermined amount of an optically active substance is blended, or an optically active group is contained in a molecular chain such as a side chain or a main chain of the liquid crystal polymer. It is preferable to use one that has and can easily fix the alignment state. Such an optical rotation film is subjected to a rubbing treatment on a flat thin film substrate formed of polyimide or polyvinyl alcohol, and a solution obtained by dissolving a liquid crystalline polymer in an appropriate solvent on the rubbed substrate is spin-coated. , Roll coating method, flow coating method, printing method, dip coating method, coating method by an appropriate method such as a casting film forming method, and drying it to remove the solvent, or without using a solvent Alternatively, it can be formed by a method in which a liquid crystalline polymer is heated and dissolved in a state exhibiting an isotropic phase, and a thin film is formed while maintaining the temperature. The rubbing treatment is performed by, for example, rubbing the substrate surface with a cloth such as polyester fiber or polyamide fiber. Further, the optical rotation layer 12 may be formed by forming a liquid crystal polymer layer on a birefringent film or a transparent protective film of a polarizing plate described later. Further, a TN type liquid crystal display panel can be used as the optical rotation layer 12, but it is not practical.

  The polarizing layer 13 becomes a protective layer on one or both sides of a polarizer made of a polyvinyl alcohol-based polarizing film or the like containing a dichroic substance via an appropriate adhesive layer, for example, an adhesive made of a vinyl alcohol-based polymer or the like. It consists of a transparent protective film bonded. As the polarizer, for example, a film made of a vinyl alcohol-based polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol may be appropriately dyed with a dichroic substance such as iodine or a dichroic dye, stretched, and cross-linked. Appropriate materials that transmit linearly polarized light when natural light is inclined, such as those applied in an order or manner, can be used. Further, examples of the protective film material serving as a transparent protective layer provided on one or both sides of the polarizer include an acetate resin such as triacetyl cellulose, a norbornene resin, a polycarbonate resin, and an acrylic resin. It is not limited.

  The birefringent layer 11 and the polarizing layer 13 are provided such that the slow axis of the birefringent layer 11 and the absorption axis of the polarizing layer 13 are parallel (the slow axis of the birefringent layer 11 and the polarizing layer 13 are parallel to each other). (It may be provided such that the absorption axis is perpendicular to the absorption axis.) As the optical rotation layer 12, for example, an optical rotation film composed of a chiral nematic liquid crystal layer satisfying the Morgan condition is used, and the optical axis (rubbing direction to the film) of the surface on the birefringent layer 11 side is slower than that of the birefringent layer 11. An angle α is formed with respect to the phase axis, and the optical axis of the surface on the polarizing layer 13 side is provided so as to coincide with the absorption axis of the polarizing layer 13 (the optical axis of the surface on the polarizing layer 13 side is polarized light). (It may be provided so as to be orthogonal to the absorption axis of the layer 13). The elliptically polarizing plate 10 transmits only a predetermined linearly polarized light of the light incident from the polarizing layer 13 side through the polarizing layer 13, and rotates the polarization direction of the linearly polarized light through the optical rotation layer 12 by a predetermined angle (rotation). Then, the linearly polarized light is converted into elliptically polarized light by the birefringent layer 11 and emitted.

  As described above, according to the elliptically polarizing plate 10 of the present invention, since the optical rotation layer 12 is provided between the birefringent layer 11 and the polarizing layer 13, the slow axis of the birefringent layer 11 and the absorption of the polarizing layer 13 are prevented. Although the axis is parallel or orthogonal, the linearly polarized light from the polarizing layer 13 can be rotated by the optical rotation layer 12 and emitted as elliptically polarized light by the birefringent layer 11.

  FIG. 3 shows a method for manufacturing such an elliptically polarizing plate 10. Hereinafter, the manufacturing method will be described.

  First, a roll of a polarizing plate, a roll of a birefringent film, and a roll of an optical rotation film wound in a roll shape are prepared. At this time, as the roll of the optical rotation film, a roll whose optical axis (optical axis of the liquid crystal polymer) in contact with the polarizing plate is parallel to or perpendicular to the absorption axis of the polarizing plate is selected. Here, the direction of the absorption axis of the polarizing plate is the flow direction (MD direction) of the roll because it matches the stretching direction of the polarizer. Further, the direction of the slow axis of the birefringent film coincides with the stretching direction, so that the longitudinal direction is the roll flow direction (MD direction) in the case of longitudinal stretching and the orthogonal direction (TD direction) in the case of transverse stretching. The slow axis direction of the birefringent film is a case having a positive optical anisotropy, and the opposite is applied to a substance having a negative optical anisotropy.

  Then, each is pulled out from the roll of the polarizing plate and the roll of the optical rotation film, and they are continuously bonded by a roll-to-roll bonding via an adhesive (or an adhesive). A roll of a polarizing plate provided with 12 is obtained.

  Next, as shown in FIG. 3A, each is pulled out from the roll 23 of the polarizing plate provided with the optical rotation layer 12 and the roll 21 of the birefringent film and roll-to-roll through an adhesive (or an adhesive). A continuous lamination is performed by lamination, and the resultant is wound into a roll to obtain a roll 20 of the long elliptically polarizing plate 10. The roll 20 of the manufactured elliptically polarizing plate 10 has a direction in which the absorption axis of the polarizing layer 13 coincides with the length direction, and in the case where the direction of the slow axis of the birefringent film is longitudinally stretched, the length in the length direction. They coincide (the absorption axis and the slow axis are parallel), and in the case of transverse stretching, they coincide in the width direction (the absorption axis and the slow axis are perpendicular). The optical rotation layer 12 may be provided in advance on the birefringent film as shown in FIG. 3 (b), and the roll 23 of the polarizing plate and the birefringence as shown in FIG. 3 (c). Each of the film roll 21 and the optical rotation film roll 22 may be pulled out and sandwiched between the optical rotation film, and they may be continuously bonded by roll-to-roll bonding.

  Then, the elliptically polarizing plate 10 having a shape according to the intended use is cut out from the roll 20 of the elliptically polarizing plate 10.

  As described above, the elliptically polarizing plate 10 of the present invention draws the polarizing plate and the birefringent film from the roll of the polarizing plate and the roll of the birefringent film, respectively. Can be efficiently manufactured by performing roll-to-roll bonding in which the components are bonded.

  4A to 4C show a liquid crystal display device 30 in which the elliptically polarizing plate 10 as described above is stacked on the display surface side of the liquid crystal display panel 31. Specifically, FIG. 4A shows a liquid crystal display monitor, FIG. 4B shows a mobile phone, and FIG. 4C shows a PDA.

  When the outer shape of the liquid crystal display panel 31 is rectangular as in the liquid crystal display device 30, the elliptically polarizing plate 10 is provided so that the absorption axis of the polarizing layer 13 is along one of the sides of the liquid crystal display panel 31. Is preferred. In this case, since the elliptically polarizing plate 10 is cut out so that the sides are along the length direction of the roll, cuts having an angle with respect to the length direction of the roll 20 of the elliptically polarizing plate 10 are made. Therefore, the elliptically polarizing plate 10 for each liquid crystal display panel 31 can be cut out without waste. Further, the rolls of the polarizing plate 23 and the roll of the birefringent film 21 are previously slit so as to match the width of the liquid crystal display panel 31, and then they are roll-to-roll bonded to manufacture the roll 20 of the elliptically polarizing plate 10. By doing so, the elliptically polarizing plate 10 can be bonded to the liquid crystal display panel 31 by a labeler method, and the liquid crystal display device 30 can be manufactured efficiently.

(Embodiment 2)
An elliptically polarizing plate 10 according to a second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2B is a diagram illustrating an optical axis arrangement (a plan view as viewed from the polarizing layer side) of the elliptically polarizing plate 10 according to Embodiment 2 of the present invention. Since the external configuration of the elliptically polarizing plate 10 and the liquid crystal display device 30 is the same as that of the first embodiment, the configuration will be described with reference to FIGS. 1, 3, and 4A to 4C for convenience. In the second embodiment, the elliptically polarizing plate 10 is used. However, a circularly polarizing plate may be used.

  The elliptically polarizing plate 10 has a configuration in which an outer birefringent layer 11, an intermediate birefringent layer 12, and a polarizing layer 13 are sequentially laminated via an adhesive layer 14 (or an adhesive layer).

  The outer birefringent layer 11 is formed by stretching an unstretched resin film (raw film) made of a thermoplastic resin such as a polycarbonate resin, a norbornene resin, a polysulfone resin, a polyarylate resin, a polyester resin, and a cellulose resin. It is composed of a film. As the raw film, a film produced by a solvent casting method having excellent uniformity such as thickness is usually used. As the stretching method, for example, a stretching method such as a longitudinal uniaxial stretching method between rolls, a tenter horizontal uniaxial stretching method, a longitudinal uniaxial stretching method between rolls is used, but a tenter stretching method capable of high uniform stretching and a stretching method between rolls are preferably used. Can be Further, a biaxial birefringent film which is stretched twice in the longitudinal direction and the transverse direction by these stretching methods may be used.

  The intermediate birefringent layer 12 is preferably made of a birefringent film composed of a single uniaxial liquid crystal coating layer having a retardation of λ / 2 nm (λ is the wavelength of light that is most important). The liquid crystal material used for the intermediate birefringent layer 12 is an optically active substance or a liquid crystalline polymer containing no optically active group, for example, a uniaxial liquid crystal (for example, a nematic liquid crystal), and the alignment state thereof is easily fixed. Those which can be used are preferably used. Such a birefringent film is subjected to a rubbing treatment on a flat thin film substrate formed of polyimide or polyvinyl alcohol, and on the rubbed substrate, a solution in which liquid crystal is dissolved in an appropriate solvent is spin-coated, Coating by a suitable method such as a roll coating method, a flow coating method, a printing method, a dip coating method, a casting film forming method, and drying and removing the solvent to form a coating layer. Can be. As described above, if the intermediate birefringent layer 12 is formed of a coating layer of a liquid crystalline polymer, the intermediate birefringent layer 12 can be formed without being stretched. Since the 12 slow axis directions can be arbitrarily set with respect to the roll flow direction, roll-to-roll bonding can be performed. The rubbing treatment is performed by, for example, rubbing the substrate surface with a cloth such as polyester fiber or polyamide fiber. The optical axis of the liquid crystal coating layer is parallel to or perpendicular to the rubbing direction.

  The polarizing layer 13 becomes a protective layer on one or both sides of a polarizer made of a polyvinyl alcohol-based polarizing film or the like containing a dichroic substance via an appropriate adhesive layer, for example, an adhesive made of a vinyl alcohol-based polymer or the like. It consists of a transparent protective film bonded. As the polarizer, for example, a film made of a vinyl alcohol-based polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol may be appropriately dyed with a dichroic substance such as iodine or a dichroic dye, stretched, and cross-linked. Appropriate materials that transmit linearly polarized light when natural light is inclined, such as those applied in an order or manner, can be used. Further, examples of the protective film material serving as a transparent protective layer provided on one or both sides of the polarizer include an acetate resin such as triacetyl cellulose, a norbornene resin, a polycarbonate resin, and an acrylic resin. It is not limited.

  The outer birefringent layer 11 and the polarizing layer 13 are provided such that the slow axis of the outer birefringent layer 11 and the absorption axis of the polarizing layer 13 are parallel (the slow axis of the outer birefringent layer 11 and the polarization The layer 13 may be provided so that the absorption axis is perpendicular to the layer 13). Further, as the intermediate birefringent layer 12, for example, a birefringent film composed of one uniaxial liquid crystal coating layer is used, and the retardation is a half wavelength of a reference wavelength (a wavelength to be emphasized: for example, 460 nm or 550 nm). What is necessary is just to have a retardation of. Further, the intersection angle θ between the absorption axis of the polarizing layer 13 and the slow axis of the intermediate birefringent layer 12 is an angle at which the linearly polarized light converted by the polarizing layer 13 is rotated to an angle at which it is desired to enter the outer birefringent layer 11. It may be set to 1/2 of α (θ = α / 2). The elliptically polarizing plate 10 transmits only a predetermined linearly polarized light of the light incident from the polarizing layer 13 side by the polarizing layer 13, and rotates the polarization direction of the linearly polarized light by the intermediate birefringent layer 12 by a predetermined angle, The linearly polarized light is converted into elliptically polarized light by the outer birefringent layer 11 and emitted.

  As described above, according to the elliptically polarizing plate 10 of the present invention, since the intermediate birefringent layer 12 is provided between the outer birefringent layer 11 and the polarizing layer 13, the slow axis of the outer birefringent layer 11 and the polarization Despite that the absorption axis of the layer 13 is parallel or orthogonal, the linearly polarized light from the polarizing layer 13 is rotated by the intermediate birefringent layer 12 and emitted as elliptically polarized light by the outer birefringent layer 11. Can be.

  Next, a method for manufacturing the elliptically polarizing plate 10 will be described.

  First, a roll of a polarizing plate, a roll of an outer birefringent film, and a roll of an intermediate birefringent film wound in a roll are prepared. At this time, as the roll of the intermediate birefringent film, a roll having a half-wave retardation of a reference wavelength (a wavelength to be emphasized: for example, 460 nm or 550 nm) is used, and an optical axis (optical axis of a liquid crystal polymer) is used. May be set to の of the angle α to be rotated with respect to the absorption axis (or transmission axis) of the polarizing plate. Here, the direction of the absorption axis of the polarizing plate is the flow direction (MD direction) of the roll because it matches the stretching direction of the polarizer. In addition, the direction of the slow axis of the outer birefringent film coincides with the stretching direction, so that it is the roll flow direction (MD direction) in the case of longitudinal stretching and the orthogonal direction (TD direction) in the case of transverse stretching. Note that the slow axis direction of the outer birefringent film has a positive optical anisotropy, and the opposite is true for a substance having a negative optical anomaly.

  Next, each is pulled out from the roll of the polarizing plate and the roll of the intermediate birefringent film, and they are continuously bonded by a roll-to-roll bonding via an adhesive (or an adhesive), and the resultant is wound into a roll. A roll of a polarizing plate provided with an intermediate birefringent layer is obtained.

  Next, as shown in FIG. 3 (a), each is pulled out from the roll 23 of the polarizing plate provided with the intermediate birefringent layer and the roll 21 of the outer birefringent film, and rolled through an adhesive (or an adhesive). The rolls of the long elliptically polarizing plate 10 are obtained by successively bonding the rolls of the elliptically polarizing plate 10 by a roll-to-roll bonding. The roll 20 of the manufactured elliptically polarizing plate 10 has a length direction in which the direction of the absorption axis of the polarizing layer 13 matches the length direction and the direction of the slow axis of the outer birefringent film is longitudinally stretched. (The absorption axis and the slow axis are parallel), and in the case of transverse stretching, the width direction matches (the absorption axis and the slow axis are perpendicular). Note that the slow axis direction of the outer birefringent film has a positive optical anisotropy, and the opposite is true for a substance having a negative optical anisotropy. Further, as shown in FIG. 3B, an intermediate birefringent layer may be provided on the outer birefringent film in advance, and further, as shown in FIG. The rolls 21 of the outer birefringent film and the roll 22 of the outer birefringent film may be pulled out, and the intermediate birefringent films may be sandwiched therebetween so that they are continuously bonded by roll-to-roll bonding.

  Then, the elliptically polarizing plate 10 having a shape according to the intended use is cut out from the roll 20 of the elliptically polarizing plate 10.

  As described above, the elliptically polarizing plate 10 of the present invention draws the polarizing plate and the outer birefringent film from the roll 23 of the polarizing plate and the roll 22 of the outer birefringent film wound in a roll shape, respectively, and extends the stretching axis therebetween. The elliptically polarizing plate 10 capable of producing any elliptically polarized light by laminating an intermediate birefringent film having no elliptically polarized light can be efficiently manufactured by performing roll-to-roll lamination.

  The elliptically polarizing plate 10 as described above is provided so as to be laminated on the display surface side of the liquid crystal display panel 31 of the liquid crystal display device 30 such as the liquid crystal display monitor shown in FIGS. At this time, when the outer shape of the liquid crystal display panel 31 is rectangular, it is preferable that the elliptically polarizing plate 10 be provided so that the absorption axis of the polarizing layer 13 is along one of the sides of the liquid crystal display panel 31. In this case, since the elliptically polarizing plate 10 is cut out so that the sides are along the length direction of the roll, cuts having an angle with respect to the length direction of the roll 20 of the elliptically polarizing plate 10 are made. Therefore, the elliptically polarizing plate 10 for each liquid crystal display panel can be cut out without waste. Further, the rolls of the polarizing plate 23 and the roll of the birefringent film 21 are previously slit so as to match the width of the liquid crystal display panel 31, and then they are roll-to-roll bonded to manufacture the roll 20 of the elliptically polarizing plate 10. By doing so, the elliptically polarizing plate 10 can be bonded to the liquid crystal display panel 31 by a labeler method, and the liquid crystal display device 30 can be manufactured efficiently.

  Hereinafter, specific examples will be described.

(Evaluation sample)
<Example 1 of the present invention>
FIG. 5A is a cross-sectional configuration diagram of the elliptically polarizing plate 10 of Example 1 of the present invention. FIG. 6A is a diagram showing the arrangement of the optical axis. Example 1 of the present invention is an example in which a circularly polarizing plate is used as an example, and a light-rotating layer 12 having a light-rotating angle of 45 degrees is sandwiched between a polarizing layer 13 and a birefringent layer 11 (here, a λλ plate). The rotation angle may be adjusted in accordance with desired characteristics.)

  The elliptically polarizing plate 10 comprises a commonly used general-purpose polarizing plate (trade name: HEG1425DU, manufactured by Nitto Denko Corporation) and a birefringent film comprising a retardation plate having a retardation of 140 nm and uniaxially stretched polycarbonate resin. A polarizing plate, a polarizing layer 13, a polarizing film, a rotating layer 12, a birefringent film, a birefringent layer 11, and a pressure-sensitive adhesive. Represent the respective adhesive layers 14. As the polarizing plate, a 30 cm-sided square plate cut out from the roll of the polarizing plate so that the sides were along the length direction and the width direction was used. As the birefringent film, a birefringent film having a square shape of 30 cm on a side, which was cut out from a roll of the birefringent film so that the sides were along the length direction and the width direction. An acrylic resin-based adhesive was used. The optical rotation film was manufactured as follows. A chiral nematic liquid crystal obtained by mixing an optically active substance with a liquid crystal polymer was mixed and adjusted with a phenol / tetrachloroethane mixed solvent. Rubbing treatment was performed on the triacetyl cellulose (TAC) film 12a in its length direction. After continuously applying and drying the above solution on the TAC film 12a, a heat treatment was performed at 200 ° C. for 30 minutes to complete the alignment treatment, and the resultant was cooled to room temperature.

  When manufacturing the elliptically polarizing plate 10, the polarizing plate and the TAC film of the optical rotation film are set so that the absorption axis of the polarizing plate and the rubbing axis of the optical rotation film (optical axis of the liquid crystal polymer = optical axis of the optical rotation film) are parallel. 12a side was bonded. Further, the side surface of the liquid crystal polymer layer 12b of the optical rotation film and the birefringent film were bonded so that the absorption axis of the polarizing plate was parallel to the slow axis of the retardation plate.

<Example 2 of the present invention>
FIG. 5B is a cross-sectional configuration diagram of the elliptically polarizing plate 10 of Example 2 of the present invention. FIG. 6B is a diagram showing the arrangement of the optical axis. The present invention example 2 is an example in which a circularly polarizing plate is used as an example, and an intermediate birefringent layer 12 is sandwiched between a polarizing layer 13 and an outer birefringent layer 11 (here, a λλ plate). (The angle of incidence on the outer birefringent layer 11 is 45 degrees with respect to the slow axis (fast axis) of the outer birefringent layer 11 so that the linearly polarized light enters Thus, an example is shown in which the crossing angle between the optical axis of the intermediate birefringent layer 12 and the absorption axis of the polarizing layer 13 is set to 22.5 degrees (this crossing angle is adjusted according to desired characteristics). It is possible.).

  This elliptically polarizing plate 10 is composed of a general-purpose polarizing plate (trade name: HEG1425DU manufactured by Nitto Denko Corporation) and an outer birefringent film composed of a retardation plate having a retardation of 140 nm and uniaxially stretched polycarbonate resin. A monoaxial liquid crystal polymer coating film (the optical axis forms an intersection angle of 22.5 ° with the absorption axis of the polarizing plate at a retardation of 270 nm), and is bonded using an adhesive; The polarizing plate forms the polarizing layer 13, the uniaxial liquid crystal polymer coating film forms the intermediate birefringent layer 12, the birefringent film forms the outer birefringent layer 11, and the adhesive forms the adhesive layer 14. As the polarizing plate, a 30 cm-sided square plate cut out from the roll of the polarizing plate so that the sides were along the length direction and the width direction was used. As the outer birefringent film, a 30 cm-square side cut from the roll of the outer birefringent film so that the side was cut along the length direction and the width direction was used. An acrylic resin-based adhesive was used. In addition, a uniaxial liquid crystal polymer coating film was prepared as follows. A liquid crystal polymer (nematic liquid crystal) was mixed and adjusted with a phenol / tetrachloroethane mixed solvent. Rubbing treatment was performed on the triacetyl cellulose (TAC) film 12a in a direction having a crossing angle of 22.5 ° with the length direction thereof. After continuously applying and drying the above solution on the TAC film 12a, a heat treatment was performed at 200 ° C. for 30 minutes to complete the alignment treatment, and the resultant was cooled to room temperature.

  In manufacturing the elliptically polarizing plate 10, the polarizing plate and the intermediate birefringence are adjusted so that the absorption axis of the polarizing plate and the rubbing axis (optical axis of the liquid crystal polymer) of the uniaxial liquid crystal polymer coating film are 22.5 °. The TAC film 12a side of the film was bonded. Further, the side surface of the liquid crystal polymer layer 12b of the intermediate birefringent film and the outer birefringent film were bonded so that the absorption axis of the polarizing plate was parallel to the slow axis of the retardation plate.

<Conventional example>
FIG. 7 is a cross-sectional configuration diagram of a conventional elliptically polarizing plate 10 ′. FIG. 8 is a diagram showing the arrangement of the optical axes.

  This elliptically polarizing plate 10 ′ is obtained by combining the general-purpose polarizing plate (HEG1425DU) used in the present invention with a birefringent film which is a retardation plate of polycarbonate having a retardation of 140 nm, and the absorption axis of the polarizing plate and the retardation of the birefringent film. It is bonded so that the phase axis intersects at an intersection angle of 45 degrees.

(Evaluation and results)
<Optical characteristics>
Table 1 shows the ellipticity of light emitted from the birefringent layer or the outer birefringent layer when natural light was incident from the polarizing layer side for each of Inventive Example 1, Inventive Example 2, and Conventional Example. The result was.

  In Example 1 of the present invention, ellipticities of light having wavelengths of 400 nm, 500 nm, and 650 nm are 0.49, 0.96, and 0.73, respectively. On the other hand, in the conventional example, the ellipticities are 0.49, 0.96, and 0.72 for light having wavelengths of 400 nm, 500 nm, and 650 nm, respectively. That is, it can be seen that Example 1 of the present invention and the conventional example show almost the same characteristics.

  Further, in Example 2 of the present invention, the ellipticities of light having wavelengths of 400 nm, 500 nm and 650 nm are 0.61, 0.89 and 0.83, respectively. From this, it can be seen that Example 2 of the present invention becomes circularly polarized light in a wide band of wavelengths and is superior to a conventional example as a circularly polarizing plate. This is considered to be because in Example 2 of the present invention, the wavelength dispersion of the intermediate birefringent layer and the wavelength dispersion of the outer birefringent layer cancel each other.

<Utilization rate of polarizing plate and birefringent film>
In Example 1 of the present invention, as shown in FIG. 6, since an optical rotation film is used, the elliptically polarizing plate 10 is formed by stacking a square polarizing plate and a birefringent film, and is stuck tightly without waste. As a result, an elliptically polarizing plate 10 having an area of 900 cm ² was obtained, and the utilization efficiency of the polarizing plate and the birefringent film was 100%.

  Since the intermediate birefringent layer was also provided in Example 2 of the present invention, the utilization efficiency of the polarizing plate and the outer birefringent film was 100%.

On the other hand, in the conventional example, since it was necessary to bond the absorption axis of the polarizing plate and the slow axis of the birefringent film so as to intersect at an intersection angle of 45 degrees, the area of the elliptically polarizing plate 10 was 746 cm ² , The utilization efficiency of the polarizing plate and the birefringent film was 82.9%. That is, about 17% of the polarizing plate and the birefringent film were not used as the elliptically polarizing plate 10 '.

<Applicability to liquid crystal display panels>
When the elliptically polarizing plate 10 of Example 1 of the present invention is pasted to a liquid crystal display panel having a rectangular outer shape, the elliptically polarizing plate 10 is attached to the polarizing plate because the absorption axis of the polarizing plate is along the side of the elliptically polarizing plate 10. By sticking the liquid crystal display panel so that the absorption axis is along the side of the liquid crystal display panel, it is not necessary to cut the elliptically polarizing plate 10 at an oblique angle. Can be set to a maximum of 100%.

  Similarly, in Example 2 of the present invention, the utilization efficiency of the elliptically polarizing plate 10 can be set to a maximum of 100%.

  On the other hand, when the conventional elliptically polarizing plate 10 'is bonded to a liquid crystal display panel having a rectangular outer shape, the elliptically polarizing plate 10' is not square, and the absorption axis of the polarizing plate is along the side of the liquid crystal display panel. When the elliptically polarizing plate 10 'is to be attached to a liquid crystal display panel, a portion that cannot be used occurs, so that the utilization efficiency of the elliptically polarizing plate 10' becomes less than 100%.

  As described above, the present invention is useful for an optical film having not only a polarizing layer but also a birefringent layer, and a liquid crystal display device having the same.

1 is a cross-sectional view of an elliptically polarizing plate according to Embodiments 1 and 2 of the present invention. FIG. 3 is an explanatory diagram illustrating an optical axis arrangement of the elliptically polarizing plate according to the first embodiment of the present invention. It is an explanatory view showing the optical axis arrangement of the elliptically polarizing plate according to the second embodiment of the present invention. FIG. 3 is an explanatory diagram illustrating a method for manufacturing an elliptically polarizing plate according to Embodiments 1 and 2 of the present invention. FIG. 1 is an explanatory diagram illustrating a liquid crystal display device (liquid crystal display monitor) according to Embodiments 1 and 2 of the present invention. FIG. 1 is an explanatory diagram illustrating a liquid crystal display device (mobile phone) according to Embodiments 1 and 2 of the present invention. FIG. 1 is an explanatory diagram illustrating a liquid crystal display device (PDA) according to Embodiments 1 and 2 of the present invention. FIG. 2 is a cross-sectional view of the elliptically polarizing plate of Example 1 of the present invention. It is sectional drawing of the elliptically polarizing plate of the example 2 of this invention. FIG. 3 is an explanatory diagram showing an arrangement of an optical axis of the elliptically polarizing plate of Example 1 of the present invention. It is explanatory drawing which shows arrangement | positioning of the optical axis of the elliptically polarizing plate of the example 2 of this invention. It is sectional drawing of the elliptically polarizing plate of a conventional example. It is explanatory drawing which shows arrangement | positioning of the optical axis of the conventional elliptically polarizing plate.

Explanation of reference numerals

10, 10 'elliptically polarizing plate 11, 11' birefringent layer, outer birefringent layer 12, optical rotation layer, intermediate birefringent layer 12a TAC film 12b liquid crystal polymer layer 13, 13 'polarizing layer 14, 14' adhesive layer 20 elliptically polarizing plate Roll of polarizing plate 22 Roll of optical rotation film, roll of intermediate birefringent film 23 Roll of birefringent film, roll of outer birefringent film 30 Liquid crystal display device 31 Liquid crystal display panel

Claims (7)

A polarizing layer that converts incident natural light into linearly polarized light, an optical rotation layer that rotates the linearly polarized light converted by the polarizing layer, and a birefringent layer that converts the linearly polarized light that is rotated by the optical rotation layer into elliptically polarized light, Laminated
The optical film, wherein the polarizing layer and the birefringent layer are provided such that the absorption axis of the polarizing layer and the slow axis of the birefringent layer are parallel or orthogonal to each other. . A polarizing layer that converts incident natural light into linearly polarized light, an intermediate birefringent layer that rotates the linearly polarized light converted by the polarizing layer, and an outer bilayer that converts the linearly polarized light rotated by the intermediate birefringent layer into elliptically polarized light. A refraction layer and
The polarizing layer and the outer birefringent layer are provided such that the absorption axis of the polarizing layer and the slow axis of the outer birefringent layer are parallel or orthogonal to each other. Optical film. The optical film according to claim 2,
An optical film, wherein the intermediate birefringent layer is formed of a liquid crystal polymer coating layer. A liquid crystal display device comprising: a liquid crystal display panel for image display; and an optical film provided to be laminated on at least one side of the liquid crystal display panel,
The optical film, a polarizing layer, an optical rotation layer, and a birefringent layer are laminated, the polarizing layer and the birefringent layer, the absorption axis of the polarizing layer and the slow axis of the birefringent layer. Are provided so as to be parallel or orthogonal to each other. A liquid crystal display device comprising: a liquid crystal display panel for image display; and an optical film provided to be laminated on at least one side of the liquid crystal display panel,
The optical film, a polarizing layer, an intermediate birefringent layer, and an outer birefringent layer are laminated, the polarizing layer and the outer birefringent layer, the absorption axis of the polarizing layer and the outer birefringent layer A liquid crystal display device, wherein the liquid crystal display device is provided so that the slow axis is parallel or orthogonal. The liquid crystal display device according to claim 4, wherein
The liquid crystal display panel has a rectangular outer shape,
The liquid crystal display device, wherein the optical film is provided so that an absorption axis of the polarizing layer is along one of sides of the liquid crystal display panel. The liquid crystal display device according to claim 5,
A liquid crystal display, wherein the intermediate birefringent layer is formed of a liquid crystal polymer coating layer.

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