JP2008139625A - Elliptically polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an elliptically polarizing plate, in which a linearly polarizing plate and a liquid crystalline optical compensation plate having no support substrate are laminated, to evade the breaking of a liquid crystalline optical compensation plate upon handling without impairing the feature of thin wall and light weight. <P>SOLUTION: The elliptically polarizing plate is prepared by stacking a protective film 1, the linearly polarizing plate 2 and the liquid crystalline optical compensation plate 3 having no support substrate in the order, wherein the protective film 1 has a thickness of 50 to 500 μm. By using the protective film 1 having a thickness larger than the thickness of the conventional one, the bending resilience of the elliptically polarizing plate is improved and the bending and distortion upon the handling can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an elliptically polarizing plate that uses a liquid crystalline optical compensator and is thin and easy to handle.

  In recent years, the display market for portable terminal devices that can take advantage of the thin and light weight characteristic of a liquid crystal display device has greatly expanded. In mobile terminal devices, there is a strong demand for reduction in overall thickness and weight, and in particular, reduction in thickness and weight of displays is an important issue. Due to the strong demand of users to reduce the thickness and weight, it is necessary to reduce the thickness of each member. Therefore, for example, in Japanese Patent Application Laid-Open No. 8-278491 (Patent Document 1), a film-like layer made of a liquid crystalline polymer aligned on an alignment substrate is bonded to a removable substrate through an adhesive. Thereafter, it is disclosed that the alignment substrate is peeled off, the liquid crystalline polymer film-like layer is transferred to the releasable substrate, and then the releasable substrate is peeled off. Thereby, it can be set as the structure except the orientation board | substrate used as the support body of a liquid crystalline optical compensation board, and can achieve thickness reduction.

  Japanese Patent Laid-Open No. 2003-75636 (Patent Document 2) discloses an ellipse composed of a linearly polarizing plate and an optical anisotropic element composed of an alignment fixed layer of a liquid crystalline substance, and a stress blocking layer provided thereon. A polarizing plate is disclosed.

JP-A-8-278491 JP 2003-75636 A

  By the way, in an elliptical polarizing plate in which a linear polarizing plate and a liquid crystalline optical compensator are laminated, if the support substrate is peeled off from the liquid crystalline optical compensator in order to reduce the weight of the thin film, it occurs when handling the elliptical polarizing plate. Due to the influence of bending and strain, there is a problem that the liquid crystalline optical compensation plate is likely to be finely deformed or cracked. The introduction of the stress blocking layer as disclosed in Patent Document 2 facilitates handling, but the flexibility is not greatly improved, and the liquid crystal optical compensator is cracked depending on how it is handled. There was a risk of doing.

  Accordingly, an object of the present invention is an elliptically polarizing plate in which a linearly polarizing plate and a liquid crystalline optical compensator without a supporting substrate are laminated, and the liquid crystalline optical compensation during handling without impairing the thin and lightweight characteristics. An object of the present invention is to provide an elliptically polarizing plate that can avoid occurrence of cracks in the plate.

  As a result of intensive studies to solve such problems, the present inventors have found that an elliptical polarizing plate in which a linear polarizing plate and a liquid crystalline optical compensator having no support substrate are laminated, the outer side of the linear polarizing plate Furthermore, the inventors have found that by attaching a protective film having a predetermined thickness, it is possible to effectively suppress the occurrence of cracks when handling the elliptically polarizing plate, and the present invention has been achieved.

  That is, according to the present invention, a protective film, a linearly polarizing plate, and a liquid crystalline optical compensator having no support substrate are laminated in this order, and the protective film has an elliptical polarizing plate having a thickness of 50 μm to 500 μm. Is provided.

  By using a thick protective film as described above, it is possible to increase the bending resilience of an elliptically polarizing plate in which a liquid crystalline optical compensator having no support substrate is bonded to a linear polarizing plate. Therefore, when this elliptical polarizing plate is handled, it is less susceptible to distortion and bending, and the liquid crystal display device can be produced efficiently.

  Hereinafter, the present invention will be described in detail. In FIG. 1, the example of the elliptically polarizing plate based on this invention was shown with the cross-sectional schematic diagram. Referring to FIG. 1, an elliptical polarizing plate 10 of the present invention includes a protective film 1, a linear polarizing plate 2, and a liquid crystal optical compensation plate 3 laminated in this order, and the thickness of the protective film 1 is 50 μm to 50 μm. The thickness is 500 μm. The space between the protective film 1 and the linearly polarizing plate 2 and between the linearly polarizing plate 2 and the liquid crystalline optical compensator 3 are usually attached via adhesive layers 5 and 6. In many cases, an adhesive layer 20 for bonding to the liquid crystal cell is provided outside the liquid crystal optical compensation plate 3, and in this case, a separator 21 is provided to protect the surface.

  The protective film 1 is generally composed of a resin, and a material excellent in transparency, smoothness, mechanical strength, and the like is preferably used. Examples thereof include polyester-based, acrylic-based, polyolefin-based, polyamide-based, polyethersulfone-based, polyimide-based, polycarbonate-based, and acetate-based resins.

  The linearly polarizing plate 2 has a function of extracting linearly polarized light from incident light, and the type thereof is not particularly limited. As an example of a suitable linearly polarizing plate, one having a configuration in which a transparent protective layer is provided on both surfaces of a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin can be exemplified. As the dichroic pigment, iodine or a dichroic organic dye is used. Moreover, as a transparent protective layer, a triacetyl cellulose film etc. are used, for example. The thickness of the polarizing film is, for example, about 5 to 50 μm, and the thickness of the linear polarizing plate 2 as a whole is, for example, about 50 to 200 μm.

  The liquid crystalline optical compensator 3 is one in which a liquid crystalline compound is applied and oriented, and the orientation is fixed, and is usually produced by applying a liquid crystalline compound on a support substrate. Before being bonded to the plate 2 to form an elliptically polarizing plate, the support substrate is peeled off, so that it is finally used as a form having no support substrate. The thickness of the liquid crystalline optical compensation plate 3 is, for example, about 5 to 30 μm. This liquid crystalline optical compensator has an optical function for compensating the viewing angle and color of the liquid crystal display device. Such a liquid crystalline optical compensator (with a liquid crystal layer formed on a support substrate) is, for example, a film sold by Shin Nippon Oil Co., Ltd., and rod-like liquid crystal molecules are formed on the support substrate. “LC film” fixed in a twisted orientation in the film thickness direction, or “NH film” in which rod-like liquid crystal molecules are fixed in an oblique orientation while changing the inclination in the film thickness direction on the support substrate ( Both are trade names).

  Adhesive layer 5 for adhering protective film 1 and linear polarizing plate 2, adhesive layer 6 for adhering linear polarizing plate 2 and liquid crystalline optical compensator 3, and adhesive provided outside liquid crystalline optical compensator 3 Each of the agent layers 20 can be made of a highly transparent adhesive such as acrylic. Further, the separator 21 for protecting the pressure-sensitive adhesive layer 20 can be constituted, for example, by applying a silicone-based release agent on one side of a film made of a resin such as polyethylene terephthalate.

  And in this invention, the thickness of the protective film 1 arrange | positioned on the outer side of the linearly-polarizing plate 2 shall be 50 micrometers or more and 500 micrometers or less. When the thickness is less than 50 μm, the bending repulsion of the elliptically polarizing plate 10 to which the protective film is attached is small, and there is a possibility that the liquid crystalline optical compensator 3 is cracked during handling. If the thickness of the protective film 1 becomes too large, the whole becomes thick, so the upper limit of the thickness is 500 μm. As the thickness of the protective film 1 is increased to 50 μm or more, the bending resilience of the elliptically polarizing plate increases. Therefore, the thickness is more preferably 100 μm or more. Further, from the viewpoint of not increasing the overall thickness, it is also preferable that the thickness of the protective film 1 is 200 μm or less.

  The elliptically polarizing plate 10 having the pressure-sensitive adhesive layer 20 as shown in FIG. 1 is bonded to at least one surface of the liquid crystal cell with the separator 21 peeled off, and finally the protective film 1 is peeled off together with the pressure-sensitive adhesive layer 5. It becomes a liquid crystal display device.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by these examples. The measurement methods in the following examples are as follows.

<Thickness of protective film>
Measurement was performed with a measuring machine “ZC-101” manufactured by Nikon Corporation.

<Bending resilience>
Measured in accordance with JIS L 1096 Method A (Gurley method). That is, measurement was performed using a 25 mm × 25 mm sample, and the sample size (25 mm × 25 mm = 1 inch × 1 inch), weight of the pendulum weight and mounting position [100 mm from the axis (= 4 Using a conversion coefficient [in this case, 444] with a 200 g weight attached at the position of inch), the bending resistance indicating rebound was calculated in units of force (mgf).

[Comparative Examples 1-2 and Examples 1-3]
(A) Production of protective film A methylene chloride solution of polyethylene terephthalate was uniformly applied on a mirror-finished stainless steel plate with an applicator, dried at 50 ° C. for 5 minutes, and then peeled off from the stainless steel plate. The film was dried at a temperature of 10 ° C. for 10 minutes to produce four types of films having thicknesses of 38 μm (Comparative Example 2), 75 μm (Example 1), 100 μm (Example 2), and 125 μm (Example 3). Further, an acrylic adhesive solution was applied to one side of each film and dried to form an adhesive layer having a thickness of 25 μm, thereby producing a protective film with an adhesive.

(B) Production of Elliptical Polarizing Plate A linear polarizing plate was prepared in which a 40 μm thick triacetyl cellulose film was bonded to both surfaces of a 30 μm thick polarizing film in which iodine was adsorbed and oriented on polyvinyl alcohol. The protective film with the pressure-sensitive adhesive obtained in (a) above was bonded to one side of the linear polarizing plate on the pressure-sensitive adhesive layer side, and an acrylic pressure-sensitive adhesive layer having a thickness of 25 μm was attached to the other side.

  Separately, an optical compensator (“LC film” sold by Shin Nippon Oil Co., Ltd .: trade name) in which rod-like liquid crystal molecules are fixed in a twisted orientation state on a polyethylene terephthalate film was prepared. After adhering a 25 μm thick acrylic adhesive layer provided on the separator to the liquid crystal alignment layer side of the optical compensator, the polyethylene terephthalate film as the substrate was peeled off from the optical compensator, and the exposed liquid crystal layer The surface of the (optical compensator) was stuck to the pressure-sensitive adhesive layer side in the configuration of the protective film / linearly polarizing plate / pressure-sensitive adhesive layer prepared earlier to prepare an elliptical polarizing plate. At this time, the angle formed by the stretching direction of the linear polarizing plate (absorption axis direction) and the flow direction of the “LC film” (longitudinal direction of the film supplied in a roll shape) was 20 degrees.

(C) Evaluation of elliptically polarizing plate A 25 mm × 25 mm square sample was cut out from the obtained elliptically polarizing plate so that one side forms an angle of 90 degrees with respect to the extending direction of the linearly polarizing plate. Bending resilience was measured by bending in a direction perpendicular to the direction. The bending resilience was measured in the same manner for the sample without the protective film (Comparative Example 1). The results are shown in Table 1.

  As shown in Table 1, it can be seen that by increasing the thickness of the protective film provided on the outside of the linearly polarizing plate, the bending resilience increases, and therefore it is difficult to be affected by strain and bending during handling.

It is a cross-sectional schematic diagram which shows the example of an elliptically polarizing plate.

Explanation of symbols

1 ... Protective film,
2 ... Polarizing plate,
3. Liquid crystal optical compensator,
5,6 …… Adhesive layer,
10 …… Ellipse polarizing plate,
20 …… Adhesive layer,
21 …… Separator.

Claims (2)

  A protective film, a linearly polarizing plate, and a liquid crystalline optical compensator having no support substrate are laminated in this order, and the protective film has a thickness of 50 μm to 500 μm. The elliptically polarizing plate according to claim 1, wherein the protective film has a thickness of 100 μm to 200 μm.

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