TWI627452B - Polarization plate and liquid crystal display device - Google Patents

Abstract

The subject of the present invention is to provide a polarizing plate which has a protective film only on one side of a polarizer and is less prone to cracks during a durability test.

The polarizing plate 1 of the present invention includes a polarizer 2 and a protective film 3 laminated on only one surface of the polarizer 2. The end surface 2a of the polarizer 2 and the end surface 3a of the protective film 3 are inclined with respect to the thickness direction of the polarizing plate 1. The end surface 2a of the polarizer 2 is located further inside than the end surface 3a of the protective film 3. With such an end shape, the end surface 2a of the polarizer 2 is not easily exposed to a physical stimulus from the external environment.

Description

Polarizing plate and liquid crystal display device

The present invention relates to a polarizing plate and a liquid crystal display device.

In recent years, a liquid crystal panel for a liquid crystal display has been reduced in thickness. Polarizers for liquid crystal panels are generally fragile and easily cracked. Therefore, in order to protect the polarizers, a protective film is laminated on both sides of the polarizer to form a polarizer, and it is attached to the liquid crystal cell (liquid crystal cell). In addition, at this time, in order to improve the dimensional accuracy of the polarizing plate, the ends of the polarizing plate are generally polished (for example, refer to Patent Document 1).

A polarizing plate is usually attached to a liquid crystal cell using a pressure-sensitive adhesive. That is, a separator (also referred to as a release film) is bonded to a yet-to-be-used polarizer through a pressure-sensitive adhesive layer (for example, refer to Patent Document 2), and the separator is peeled off when the polarizer is used to give a sense The pressure-sensitive adhesive layer is exposed, and the polarizing plate is attached to the liquid crystal cell with the surface facing the liquid crystal cell.

In addition, the polarizing plate may have other optical functional films other than the polarizer, and the bonding of the polarizer and other optical functional films may use a pressure-sensitive adhesive (for example, refer to Patent Document 3).

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5743291

[Patent Document 2] Japanese Unexamined Patent Publication No. 11-254550

[Patent Document 3] Japanese Patent No. 3873531

In response to the demand for further thinning of the liquid crystal panel, the development of a protective film bonded on only one side of the polarizer has been continuously developed. However, a polarizing plate with a protective film bonded to only one side of the polarizer has a tendency that cracks tend to occur in the polarizer during the durability test.

Furthermore, from a design point of view, the liquid crystal display preferably has a narrow frame, and therefore requires a high dimensional accuracy for the polarizing plate. In order to obtain high dimensional accuracy, when polishing the end of a polarizing plate, a polarizing plate formed by laminating a protective film only on one side of the polarizing plate may cause great damage to the polarizing plate during grinding, roughen the end face of the polarizing plate, In the endurance test, the polarizer tends to crack easily.

Accordingly, an object of the present invention is to provide a polarizing plate which has a protective film only on one side of a polarizer and is less likely to generate cracks during a durability test. Another object is to provide a liquid crystal display device having the polarizing plate.

The present invention provides a polarizing plate having a polarizer and a protective film laminated on only one surface of the polarizer, wherein an end surface of the polarizer is And the end surface of the protective film is inclined with respect to the thickness direction of the polarizing plate, and the end surface of the polarizer is located more inside than the end surface of the protective film.

In this polarizer, the end face of the polarizer and the end face of the protective film are inclined with respect to the thickness direction of the polarizer, and the end face of the polarizer is located more inside than the end face of the protective film, so that the end face of the polarizer is not easily exposed. Physical stimuli from the external environment. Therefore, this polarizer is less prone to cracks during the durability test. In addition, the polarizing plate is preferably a sheet-like body cut out from a long polarizing plate roll and having an area of 100 square millimeters to 96,000 square millimeters.

The polarizing plate may further include a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is laminated on the surface of the polarizer opposite to the side on which the protective film is laminated, and may further have the feeling across An optically functional film laminated with a pressure-sensitive adhesive. According to this, a polarizing plate having a polarizer and a protective film can be made into a polarizing plate further having an optical function.

The end face of the optical functional film is preferably located outside the end face of the polarizer.

Accordingly, the end face of the polarizer can be further protected from physical stimuli from the external environment.

The optical function may be a reflective polarizer.

Furthermore, the present invention provides a liquid crystal display device having the above-mentioned polarizing plate. Even in a liquid crystal display device such as a liquid crystal cell having the above-mentioned polarizing plate attached thereto, the end face of the polarizer is not easily exposed to physical stimuli from the external environment.

According to the present invention, it is possible to provide a polarizing plate having a protective film only on one side of a polarizer, and which is less likely to generate cracks during a durability test. Furthermore, a liquid crystal display device having the polarizing plate can also be provided.

1, 1A, 1B‧‧‧‧Polarizer

1a‧‧‧ End face of polarizing plate

2‧‧‧ polarizing film (polarizer)

2a‧‧‧ End face of polarizing film

2b‧‧‧End of polarizing film

3‧‧‧ protective film

3a‧‧‧ end face of protective film

3b‧‧‧End of protective film

4‧‧‧Reflective Polarizer (Optical Functional Film)

4a‧‧‧ End face of reflective polarizer

5‧‧‧ pressure-sensitive adhesive layer

8‧‧‧ LCD unit

9‧‧‧ LCD panel

10‧‧‧ cutting tools

10a‧‧‧Support Desk

11a, 11b, 11c, 11d, 11e, 11f‧‧‧ Cutting

100‧‧‧LCD display device

A‧‧‧rotation shaft

B‧‧‧ cutting edge

S‧‧‧ Setting surface

FIG. 1 is a perspective view of a polarizing plate according to an embodiment of the present invention.

FIG. 2 (A) is a cross-sectional view of IIa-IIa in FIG. 1. Fig. 2 (B) is a sectional view taken along line IIb-IIb in Fig. 1.

FIG. 3 is an enlarged view of the ends of the polarizing film and the protective film.

Fig. 4 is a sectional view of a polarizing plate according to another embodiment of the present invention.

Fig. 5 is a sectional view of a polarizing plate according to another embodiment of the present invention.

Fig. 6 is a sectional view of a liquid crystal display device.

Fig. 7 is a side view of the cutting tool.

Figure 8 is a front view of the cutting tool

FIG. 9 is a diagram showing the shape of an end portion of the polarizing plate produced in Example 1. FIG.

FIG. 10 is a view showing the shape of an end portion of the polarizing plate produced in Example 2. FIG.

FIG. 11 is a diagram showing the shape of an end portion of a polarizing plate produced in Comparative Example 1. FIG.

[Forms for Implementing Invention]

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, the same or equivalent parts in each figure The same symbols are assigned and duplicated explanations are omitted. In addition, the proportions of the drawings in the inch method are not necessarily consistent with the actual ones, especially the exaggerated depiction of thickness.

<Polarizer>

As shown in Figs. 1 to 3, the polarizing plate 1 of this embodiment has a protective film 3 on a single area layer forming a thin film-shaped polarizing film (polarizing plate) 2 and transmits a pressure-sensitive adhesive layer on the other side. 5 laminated with a reflective polarizer 4. The polarizing film 2, the protective film 3, and the reflective polarizer 4 are all formed into a rectangular shape in a plan view, and this shape also becomes the appearance shape of the polarizing plate 1.

The polarizing plate 1 is bonded to one or both sides of a display unit (image display element) such as a liquid crystal cell. The polarizing plate 1 is preferably attached to the back side of the display unit. Compared with the polarizing plate on the viewing side, the polarizing plate on the rear side is more prone to dew condensation, etc., and the polarizing film is prone to cracks. If the polarizing plate 1 of this embodiment is used, the generation of the polarizing film 2 can be significantly suppressed. crack.

The end face 2a of the polarizer 2 and the end face 3a of the protective film 3, which are the constituent elements of the end face 1a of the polarizing plate 1, are inclined with respect to the thickness direction of the polarizing plate 1, and the end face 2a of the polarizing film 2 is located more than the end face of the protective film 3a is further inside (the center side of the main surface of the polarizing plate 1). In other words, among the sides constituting the end surface 2a of the polarizing film 2, the side 2b located farther from the protective film 3 and perpendicular to the thickness direction of the polarizing plate 1 (refer to FIG. 3; hereinafter referred to as "end edge 2b") Is located more inward than the side 3b described below, which is the side of the end surface 3a constituting the protective film 3 and is located away from the polarizing film 2 The side on the far side and perpendicular to the thickness direction of the polarizing plate 1 (refer to FIG. 3; hereinafter referred to as "end side 3b").

The end surface 2 a of the polarizing film 2 and the end surface 3 a of the protective film 3 form almost the same plane (that is, a flush state) with each other, and the plane is inclined with respect to the thickness direction of the polarizing plate 1. The angle α (see Fig. 3) between this plane and the surface of the polarizing plate 1 is preferably 45 to 88 degrees. Here, the angle α can be obtained from the cross-sectional shape of the polarizing plate 1 obtained through a laser microscope. More specifically, the connection between the end surface 3a of the protective film and the end surface 2a of the polarizing film is perpendicular to the protective film. Among the angles sandwiched by the planes in the thickness direction 3, the maximum angle is referred to as an angle α (see also FIG. 9).

The end edge 2b is located further inside than the end edge 3b. The distance L between the two when viewing the polarizing plate 1 (refer to FIG. 3) is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 5 Up to 10 μm. When the end edge 2b and the end edge 3b have such a positional relationship, the effect of physically protecting the end surface 2a of the polarizing film 2 is particularly high, and a wide display surface can also be ensured when constituting a liquid crystal display.

The end surface 2 a of the polarizing film 2 and the end surface 3 a of the protective film 3 preferably have the above-mentioned relationship throughout the outer periphery of the polarizing plate 1. When the above-mentioned relationship is established throughout the periphery of the polarizing plate 1, all the ends of the polarizing plate 1 can be protected from physical stimuli.

As the material of the polarizing film 2, known materials conventionally used in the production of polarizing plates can be used, and examples thereof include a polyvinyl alcohol resin, a polyvinyl acetate resin, an ethylene / vinyl acetate (EVA) resin, and a polymer Resin resin, polyester resin, etc.

Among these, a polyvinyl alcohol-based resin is preferable. When forming into a film shape for bonding to the protective film 3, it is preferable to apply a dye with iodine or a dichroic dye to the uniaxially stretched film, and then perform a boric acid treatment.

The thickness of the polarizing film 2 is preferably 2 to 30 μm, more preferably 2 to 15 μm, and even more preferably 2 to 10 μm. Generally speaking, the thinner the polarizing film is, the more likely it is to crack. However, even if the polarizing film 2 in this embodiment is 10 μm or less, cracks can be significantly prevented.

The protective film 3 is a film that prevents cracks and scratches on the main surface and the ends of the polarizing film 2. The “protective film” herein refers to a film that can be laminated on various films of the polarizing film 2 and is physically laminated on the position closest to the polarizing film 2 for the purpose of protecting the polarizing film 2.

The protective film 3 can be composed of various transparent resin films known in the field of polarizing plates. Examples include: cellulose-based resins typified by cellulose triacetate, polyolefin-based resins typified by polypropylene-based resins, cyclic olefin-based resins typified by norbornene-based resins, and polymethylene Methyl acrylate resins are representative examples of acrylic resins, and polyethylene terephthalate resins are representative examples of polyester resins. Among them, cellulose-based resins are representative. The term "transparent" as used herein means that the visible light transmittance is 80% or more.

The thickness of the protective film 3 is preferably 5 to 90 μm, more preferably 5 to 80 μm, and still more preferably 5 to 50 μm.

The laminated layer of the polarizing film 2 and the protective film 3 may be formed by laminating the polarizing film 2 and the protective film 3 formed into a film shape with an adhesive therebetween, or forming the protective film 3 by a coating layer. The material constituting the coating The solution (for example, the adhesive agent mentioned later) is apply | coated on the polarizing film 2, and it is comprised by drying or irradiating an active energy ray. The adhesive layer is not shown in FIGS. 1 to 3.

When an adhesive is used for the laminated layer between the polarizing film 2 and the protective film 3, as for the adhesive, various adhesives conventionally used in the manufacture of a polarizing plate can be used. For example, an epoxy resin which does not contain an aromatic ring in a molecule | numerator is preferable from a viewpoint of weather resistance, a refractive index, and cation polymerizability. Further, it is preferably one which is hardened by irradiation with active energy rays (ultraviolet rays or hot rays).

The epoxy resin is preferably, for example, a hydrogenated epoxy resin, an alicyclic epoxy resin, or an aliphatic epoxy resin. For epoxy resins, a polymerization initiator (for example, a photocationic polymerization initiator for polymerization by ultraviolet irradiation, a thermal cationic polymerization initiator for polymerization by heat ray irradiation), and other additives (additives) Sensitizers, etc.), and an epoxy resin composition for coating is prepared and used.

As the adhesive, a composition containing an acrylic resin such as acrylamide, acrylate, urethane acrylate, or epoxy acrylate, and an aqueous adhesive containing a polyvinyl alcohol resin can also be used.

The pressure-sensitive adhesive layer 5 may be composed of an acrylic resin, a silicone resin, polyester, polyurethane, polyether, or the like.

The thickness of the pressure-sensitive adhesive layer 5 is preferably 2 to 500 μm, more preferably 2 to 200 μm, and even more preferably 2 to 50 μm.

In the method of laminating the pressure-sensitive adhesive layer 5 of the polarizing film 2, for example, the polarizing film 2 may be coated with the The method of adding the component solution may also be a method of forming a pressure-sensitive adhesive layer 5 on the separately prepared separator with the solution, and then transferring it to the polarizing film 2.

The separator is generally a peelable film that is attached for the purpose of protecting the pressure-sensitive adhesive layer or preventing foreign matter from being attached. When the polarizing plate 1 is used, the separator is peeled to expose the pressure-sensitive adhesive layer. The separator may be composed of, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate. Among them, an stretched film of polyethylene terephthalate is preferred.

The thickness of the separator is preferably 2 to 500 μm, more preferably 2 to 200 μm, and still more preferably 2 to 100 μm.

The separator may be a temporary user during the manufacturing process of the polarizing plate 1 as described above, or may be left as a part of the polarizing plate 1 until the polarizing plate 1 is attached to a liquid crystal cell or the like.

As the reflective polarizer 4, any one can be used. The end surface 4 a of the reflective polarizer 4 is inclined with respect to the thickness direction of the polarizing plate 1, and is inclined in the same direction at substantially the same angle (for example, a range of ± 20 degrees) as the end surface 2 a of the polarizing film 2. The end edge of the reflective polarizer 4 on the side closer to the polarizer 2 is located more outward than the end edge 2b of the polarizer film 2 so as to protrude from the end of the polarizer film 2 to the outside. That is, the end surface 4 a of the reflective polarizer 4 forms the same plane as the end surface 2 a of the polarizing film 2. In a plan view, the reflective polarizer 4 preferably covers the entire surface of the polarizing film 2. The end face in this form can be obtained by, for example, laminating the reflective polarizer 4 on the polarizing film 2 through the pressure-sensitive adhesive layer 5 by cutting as described below. to make.

The full thickness of the polarizing plate 1 containing the polarizing film 2, the protective film 3, and the reflective polarizer 4 is preferably 10 to 500 μm, more preferably 10 to 300 μm, and even more preferably 10 to 200 μm.

In the polarizing plate 1 described above, the end surface 2a of the polarizer 2 and the end surface 3a of the protective film 3 are inclined with respect to the thickness direction of the polarizing plate 1, and the end surface 2a of the polarizing film 2 is located more At the inner side, the end face 2a of the polarizing film 2 is not easily exposed to physical stimuli from the external environment. Therefore, the polarizing plate 1 is unlikely to be cracked during the endurance test.

The polarizing plate 1 further includes a reflective polarizer 4 because of the pressure-sensitive adhesive layer 5 on the side opposite to the side where the protective film 3 is laminated on the polarizing film 2 through the laminated layer. The end surface 4a of the reflective polarizer 4 is located further outside than the end surface 2a of the polarizing film 2, so the end surface 2a of the polarizing film 2 can be further protected from physical stimulation from the external environment.

The polarizing plate 1 of this embodiment can be changed to a different configuration. For example, the polarizing plate 1A shown in FIG. 4 may be set such that the end face 4 a of the reflective polarizer 4 is not inclined with respect to the thickness direction of the polarizing plate 1, or the polarizing plate 1B shown in FIG. 5 may be used. It is assumed that the reflective polarizer 4 is not provided.

In addition, as shown in FIG. 6, for example, a pressure-sensitive adhesive layer 5 different from the pressure-sensitive adhesive layer 5 constituting the polarizing plate 1 is used on the back side (lower side of the figure) of the liquid crystal cell 8 to The polarizing plate 1 is attached, on the other hand, A polarizing plate 1B having a pressure-sensitive adhesive layer 5 on the surface of the polarizing film 2 is adhered to the viewing side (upper side of the figure) of the liquid crystal cell 8 to form a liquid crystal panel 9. (Illustration omitted) and other component combinations, whereby the liquid crystal display device 100 can be manufactured. In addition, in a liquid crystal display device, two polarizing plates are generally mounted, but the liquid crystal display device of this embodiment only needs to have at least one polarizing plate.

<Cutting method of end of polarizing plate>

The shape of the end portion of the polarizing plate 1 described above can be formed by cutting (polishing) the end portion of the polarizing plate, for example, as described below.

First, prepare about 100 polarizing plates obtained by laminating the polarizing film 2, the protective film 3, the pressure-sensitive adhesive layer 5 and the reflective polarizer 4 as described above and cutting them into the same shape. The same surfaces are oriented in the same direction to form a polarizing plate laminate. Next, the end portion of this polarizing plate laminated body was cut with a cutting tool described below.

As shown in FIG. 7 and FIG. 8, the cutting tool 10 is a revolving body which is fixed to the support table 10 a and is capable of revolving around the revolving axis A as an axis. In addition, although the cutting tool 10 is drawn in a disk shape in FIGS. 7 and 8, the shape is not limited to this. This rotation axis A extends in a direction orthogonal to the end surface of the polarizing plate laminated body to be cut.

The cutting tool 10 has a setting surface S that is perpendicular to the rotation axis A (that is, parallel to the end surface of the polarizing plate laminate to be cut). On the installation surface S, a first cutting portion group composed of the cutting portions 11a, 11b, and 11c, and a cutting portion 11d, 11e, and 11f are provided. In the second cutting portion group, each cutting portion has a cutting edge B for cutting an end surface. Each cutting portion is arranged around the rotation axis A. Each cutting portion protrudes from the installation surface S toward the end surface of the polarizing plate laminate to be cut, and the cutting edge B is disposed on the top surface of the protruding cutting portion. The cutting edge B included in each cutting portion is generally arranged so as to extend parallel to the installation surface S (that is, the end surface of the polarizing plate laminate to be cut).

As shown in FIG. 8, when the cutting tool 10 is rotated in the rotation direction (the direction of the arrow shown in FIG. 8), the cutting portions 11 a, 11 b, and 11 c constituting the first cutting portion group are sequentially and polarized. The end faces of the plate laminated body abut, and the end faces are cut. The cutting portions 11a, 11b, and 11c are formed so that the distance from the installation surface S to the cutting edge B (the protruding height of the cutting edge B) becomes larger in the cutting portion located further downstream in the turning direction of the cutting tool 10. Configuration. That is, the protruding height of the cutting edge B of the cutting portion 11b is larger than the protruding height of the cutting edge B of the cutting portion 11a, and the protruding height of the cutting edge B of the cutting portion 11c is larger than the protruding height of the cutting edge B of the cutting portion 11b.

The second cutting section group is also the same as described above. When the cutting tool 10 is rotated in its turning direction, the cutting sections 11d, 11e, and 11f constituting the second cutting section group sequentially come into contact with the end faces of the polarizing plate laminate. Then cut the end face. The cutting portions 11d, 11e, and 11f are arranged such that the cutting portion located further downstream in the turning direction of the cutting tool 10 has a larger distance from the installation surface S to the cutting edge B. That is, the protruding height of the cutting edge B of the cutting portion 11e is larger than the protruding height of the cutting edge B of the cutting portion 11d, and the protruding height of the cutting edge B of the cutting portion 11f is larger than The protruding height of the cutting edge B of the cutting portion 11e.

As shown in FIG. 8, the cutting sections 11 a, 11 b, and 11 c constituting the first cutting section group are cutting sections located on the downstream side in the turning direction of the cutting tool 10, from the rotary axis A to the cutting edge B. The distance to the end will be arranged in a shorter manner, that is, the distance from the rotary axis A to the cutting edge B in the cutting portion 11b is shorter than the distance in the cutting portion 11a, and the distance from the rotary axis A to the cutting portion 11c is shorter. The distance to the cutting edge B is shorter than the distance in the cutting portion 11b. The same applies to the second cutting section group. The cutting sections 11d, 11e, and 11f constituting the second cutting section group are cutting sections located on the downstream side in the rotation direction of the cutting tool 10, from the rotation axis A to the cutting edge B. The shorter the distance will be configured. That is, the distance from the rotation axis A to the cutting edge B in the cutting portion 11e is shorter than the distance in the cutting portion 11d, and the distance from the rotation axis A to the cutting edge B in the cutting portion 11f is shorter than that of the cutting portion 11e. The distance is shorter.

The cutting portions arranged on the installation surface S are preferably arranged at intervals around the rotation axis A at equal intervals.

In the cutting tool 10, the cutting portions 11a, 11b, 11d, and 11e other than the last cutting portion (the cutting portion on the most downstream side in the turning direction) in each cutting portion group are used for roughing, and such cutting edges B For example, it can be composed of polycrystalline diamond. The last cutting parts 11c and 11f in each cutting part group are for finishing, and the cutting edges B may be made of, for example, a single crystal diamond. However, the material of the cutting edge B is not limited to these.

As long as the size of the cutting tool 10 is such that the end faces of all the stacked polarizing plates can be cut together, the cutting tool 10 The rotation of 10 is not particularly limited as long as the diameter (shortest diameter) of the circle drawn by the cutting portion is the same as or longer than the height of the polarizing plate laminate.

When cutting the end of the polarizing plate laminate, the cutting tool 10 is rotated in the direction of the arrow in FIG. 8 so that the direction perpendicular to the laminating direction of the polarizing plate laminate is used as the approach direction. The person moves relatively and comes into contact. At this time, in the direction of the polarizing plate laminate, the polarizing film 2 is oriented upward with respect to the protective film 3. The cutting tool 10 is designed to be able to cut from the upper side to the lower side in the turning in the direction of the arrow in FIG. 8, but cannot be cut from the lower side to the upper side in the figure. Thereby, the polarizing plate laminated body is normally cut | disconnected by the edge part from the polarizing film 2 side to the protective film 3 side.

During cutting, the pressing force generated by the rotation of the cutting tool 10 acts on the end portion of the polarizing plate laminate, thereby tilting the end portion of the polarizing plate laminate to sag downward. By cutting the end portion in this state, each of the polarizing plates becomes a polarizing plate 1 having an inclined end surface as shown in FIGS. 2 and 3.

In cutting, in order to make the pressing force generated by the turning of the cutting tool 10 easily tilt the end of the polarizing plate laminate so as to sag downward, a method of reducing the pressure of a clamp that holds the polarizing plate laminate, Or the method of reducing the area of the clamps holding the polarizing plate laminate.

If the above-mentioned cutting process is performed, not only the end face of the polarizing plate can be inclined, but also compared with the cutting of the polarizing plate laminated body by laser in the past, it has the advantage of high dimensional accuracy.

In the above, the preferred embodiment of the present invention has been described. Obviously, the present invention is not limited by the above embodiments.

In the above embodiment, as the optical functional film laminated on the polarizing film 2 through the pressure-sensitive adhesive layer 5, the reflective polarizer 4 can be listed, but it can also be replaced with other films, for example: Film with anti-glare function; film with anti-reflective function on the surface; reflective film with reflective function on the surface; semi-transparent reflective film with both reflective and penetrating functions; viewing angle compensation film.

An optically functional film may be provided on the protective film 3 side with a pressure-sensitive adhesive layer interposed therebetween.

Moreover, in the said embodiment, the cutting tool 10 was used in order to form the edge shape of the polarizing plate laminated body, However, if the end surface of a polarizing plate can be inclined, other processing methods may be used. For example, a method in which a flat blade is inclined and cut is adopted.

[Example]

Hereinafter, the content of the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples.

(1) Production of polarizing film

A polyvinyl alcohol film having a thickness of 20 μm and an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more was stretched about 4 times in a dry uniaxial manner. With the stretched state maintained, it was immersed in pure water at 40 ° C for 1 minute, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100 at 28 ° C for 60 seconds. After that, the weight ratio of potassium iodide / boric acid / water was 10.5 / 7.5 / It was immersed in an aqueous solution of 100 at 68 ° C for 300 seconds. Next, it was washed with pure water at 5 ° C. for 5 seconds, and then dried at 70 ° C. for 180 seconds to obtain a uniaxially stretched polarizing film (polarizing film) having iodine adsorbed on the polyvinyl alcohol film and aligned. The thickness of the polarizing film is 7 μm.

(2) Preparation of water-based adhesive

Polyvinyl alcohol powder (trade name "KL-318" manufactured by Kuraray Co., Ltd., average polymerization degree: 1800) was dissolved in hot water at 95 ° C to prepare a 3% by weight aqueous polyvinyl alcohol solution. In the obtained aqueous solution, a cross-linking agent (trade name "Sumirez Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.) was mixed at a ratio of 2 parts by mass to 1 part by mass with respect to the polyvinyl alcohol powder as a water-based adhesive.

(3) Fabrication of single-sided protective polarizer

In the subsequent steps, a single-sided protective polarizer with a release film is produced. While continuously transporting the polarizing film obtained in the above (1), the protective film was continuously rolled out from a roll of a protective film (ZEONOR file ZF14-023, manufactured by Japan Zeon Co., Ltd., thickness: 23 μm) and subjected to corona treatment. deal with. In addition, the release film film was continuously rolled out from a roll of a release film (trade name "KC8UX2MW" of a TAC film manufactured by Konica Minolta Opto Co., Ltd., thickness of 80 m, without saponification treatment).

Next, while injecting the water-based adhesive obtained in the above (2) between the polarizing film and the protective film, pure water was injected between the polarizing film and the release film, and these were passed between a pair of bonding rollers to form a protective film. / Water-based adhesive Laminated film consisting of a layer, a polarizing film, pure water, and a release film. Next, the laminated film was transported and subjected to a heat treatment at 80 ° C. for 300 seconds by a drying device, thereby drying the water-based adhesive layer, and volatilizing and removing pure water existing between the polarizing film and the release film to obtain a release film. The single-sided protective polarizer. From this, the release film was peeled from the single-sided protective polarizer with a release film to obtain a single-sided protective polarizer.

(4) Fabrication of protective polarizer with brightness enhancement film

On the polarizing film surface of the single-sided protective polarizing plate obtained in (3) above, a brightness enhancement film (trade name "APF" of a reflective polarizer made by 3M Corporation) was bonded with an acrylic pressure-sensitive adhesive to obtain a brightness enhancement. One side of the film protects the polarizer. At this time, with respect to the extending direction of the polarizing film, the extending axis of the brightness enhancement film is attached in parallel.

(5) Fabrication of polarizing plate with acrylic pressure-sensitive adhesive

The acrylic pressure-sensitive adhesive with a separator film was bonded to the brightness-improving film surface of the single-sided protective polarizer with a brightness-improving film obtained in the above (4) to obtain a polarizing plate with an acrylic pressure-sensitive adhesive.

(6) End face cutting

The polarizing plate (hereinafter referred to as "polarizing plate") with an acrylic pressure-sensitive adhesive obtained in the above (5) was cut into a size of 120 mm × 70 mm, and 100 pieces of the polarizing plate after cutting were aligned on four sides and laminated. A polarizing plate laminate was obtained. A main body having a smaller area than the main surface of a polarizing plate laminated body Surface clamp to clamp the polarizer laminate. When clamping the polarizing plate laminate, the pressure of the clamp is also adjusted. Next, except that the first cutting section group and the second cutting section group each have five cutting sections, the same cutting tools as those shown in Figs. 7 and 8 are used to perform cutting processing on the four end faces ( Grinding process). The cutting conditions of the four end faces are the same.

The cutting tools used are arranged in each cutting section group such that the five cutting sections are positioned further downstream in the cutting tool rotation direction, and the protruding height of the cutting edge B is larger. The five cutting portions are arranged such that the cutting portion located further downstream in the rotation direction of the cutting tool has a shorter distance from the rotation axis A to the cutting edge B. Each of the cutting sections constituting the first cutting section group and the second cutting section group is arranged around the rotary shaft so as to be separated from each other at equal intervals, and the cutting edges are arranged at positions facing each other across the rotary shaft. The protruding height and the distance from the rotary shaft to the cutting edge are the same for the two cutting parts.

Specifically, when the cutting tool is rotated around its rotation axis A, the polarizing plate laminate is moved horizontally with the position of the cutting tool being fixed, thereby causing the cutting tool to face the end face of the polarizing plate laminate. The longitudinal direction is parallel, and the polarizing plate laminate is relatively moved, and abuts on the two end faces of the cutting edge facing each cutting portion, and the cutting processing is performed on the end faces simultaneously. The relative movement is performed from one end of the end surface to the other end. With this one-time relative movement, five-stage cutting processing is performed at cutting portions having different protruding heights of five cutting edges.

After cutting, use a 3D measurement laser microscope (OLS4100, manufactured by Olympus Co., Ltd.), observe the end of the polarizing plate, and confirm that Due to the slope of the end face.

(7) Heat shock test

A thermal shock test was performed as a durability test. A sample for thermal shock test was prepared by the following procedure.

After attaching the end-face grinding sample obtained in the above (6) to an alkali-free glass plate ("Eagle-XG" manufactured by Corning Co., Ltd.), the autoclave was added at a temperature of 50 ° C and a pressure of 5 MPa for 20 minutes. It was pressed and then left to stand in an environment of a temperature of 23 ° C and a relative humidity of 60% for one day. Then, in the hot and cold shock tester "TSA-301L-W" manufactured by ESPEC Co., Ltd., the temperature was set to -40 ° C [holding time 30 minutes], 23 ° C [holding time 5 minutes] at room temperature, The durability test was performed 12 times under the conditions in a test tank with a high temperature side of 85 ° C [holding time of 30 minutes]. After that, the sample was taken out, and the end of the sample was examined using an optical microscope (Keyence Co., Ltd., VHX-5000) to determine whether there were crack-like appearance defects, and the number of cracks in the polarizing film per 10 mm of the polarizing plate end was determined.

(8) Examples and comparative examples

The results of the implementation of "(6) end surface cutting" and "(7) thermal shock test" are shown below for the polarizing plate produced according to the implementation procedures of (1) to (5) above.

[Example 1]

100 polarizing plates are laminated, and the polarizing film is placed on the cutting processing device so that the polarizing film is on the upper side, and the cutting processing is performed by cutting the end surface from the polarizing film side to the protective film side. As a result of cutting, the end face of the polarizing plate is inclined with respect to the thickness direction of the polarizing plate. The end edge on the opposite side of the polarizing film from the bonding surface of the protective film appears on the end farther away from the polarizing film in the protective film. The sides are 6 μm further inside.

The end shape of the polarizing plate confirmed by a 3D measurement laser microscope is shown in FIG. 9. After the thermal shock test was performed, no cracks were observed in the polarizing film.

[Example 2]

Except for using saponified cellulose triacetate (Konica Minolta Opto Co., Ltd., Zero Tack, thickness: 20 μm), the same procedure as in Example 1 was performed, and an end face cutting process was performed. As a result of cutting, the end face of the polarizing plate is inclined with respect to the thickness direction of the polarizing plate. The end edge on the opposite side of the polarizing film from the bonding surface of the protective film appears on the end farther away from the polarizing film in the protective film. The sides are 9 μm further inside. The end shape of the polarizing plate confirmed by a 3D measurement laser microscope is shown in FIG. 10. After the thermal shock test was performed, no cracks were observed in the polarizing film.

[Comparative Example 1]

A polarizing plate subjected to cutting processing was manufactured in the same manner as in Example 1 except that the polarizing film was installed on the cutting processing device so as to be lower than the protective film. That is, from the protective film side to the polarizing film side The cutting of the end face is performed. As a result of cutting, the end face of the polarizing plate is inclined with respect to the thickness direction of the polarizing plate. The end edge on the opposite side of the polarizing film from the bonding surface of the protective film appears on the end farther away from the polarizing film in the protective film. The sides are 11 μm further outside. The end shape of the polarizing plate confirmed by a 3D measurement laser microscope is shown in FIG. 11. After the thermal shock test was performed, 71 cracks were observed in the polarizing film.

[Industrial availability]

The present invention can be used as a component of a liquid crystal panel, for example.

Claims (6)

A polarizing plate having a polarizing plate and a protective film laminated on only one side of the polarizing plate, wherein an end surface of the polarizing plate and an end surface of the protective film are inclined with respect to a thickness direction of the polarizing plate. The end surface is located more inward than the end surface of the protective film. When the polarizing plate is viewed from the top, the edge constituting the end face of the polarizer is located on the side farther from the protective film and perpendicular to the thickness direction of the polarizing plate. The side of the end face constituting the protective film is located at a side farther from the polarizer and perpendicular to the thickness direction of the polarizing plate, and is located at an inner side of 1 to 50 μm. The polarizing plate according to item 1 of the scope of patent application, which further has a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is laminated on the surface of the polarizer opposite to the side where the protective film is laminated. . The polarizing plate as described in item 2 of the scope of patent application, which further has an optical functional film laminated through the pressure-sensitive adhesive layer. The polarizing plate according to item 3 of the scope of patent application, wherein the end face of the optical functional film is located further outside than the end face of the polarizer. The polarizing plate according to item 3 or 4 of the scope of patent application, wherein the optically functional film is a reflective polarizer. A liquid crystal display device includes a polarizing plate as described in any one of claims 1 to 5.