JPH0720662B2 - Crack prevention cutting body - Google Patents

Description

TECHNICAL FIELD The present invention is that a crack generated at a cut end portion of a cut body made of a film having anisotropy in mechanical strength such as a stretched film extends more than a predetermined amount. The present invention relates to a crack-preventing cut body that prevents cracking.

Conventional technology and problems When a film having anisotropy in mechanical strength, such as a uniaxially stretched film, is cut in a direction intersecting a direction having a large mechanical strength, that is, a direction not parallel to a direction having a large mechanical strength, There has been a problem that fine cracks are generated in the cut portion in a direction substantially parallel to the direction of high mechanical strength, and the cracks develop into cracks due to stress or the like accompanying environmental changes.

The members of the development group to which the present inventors belong have previously proposed means for solving the above problems (Japanese Patent Application No.
60-73159). The means is to deal with the cut end of the cutting body.

However, in the subsequent research conducted by the present inventors, it was found that the handling of the cut end portion may not be sufficiently satisfactory in terms of, for example, processing efficiency.

That is, for example, when a plurality of holes 2 are punched in the width direction of an anisotropic substrate 1 made of a film having anisotropy in mechanical strength, as shown in FIG. A crack occurs in a direction substantially parallel to the large direction (long direction in the figure), and the crack expands due to stress caused by environmental changes. Alternatively, as shown in the figure, the band-shaped portion connecting the holes is welded. However, it may take a lot of time to process the individual holes, and on the other hand, the strip-shaped processing method that connects the holes causes an anisotropic state between the individual holes due to the required strength. When you want to remain, there will be problems such as not being able to deal with it.

Means for Solving the Problems The present invention provides a crack-preventing cut body processed by a new method in place of the above-mentioned cut end processing method.

That is, the crack-preventing cut body of the present invention has a predetermined distance from the cut end in the cut body having a cut end in a direction intersecting with a direction having a large mechanical strength in a product made of a film having anisotropy in mechanical strength. It is characterized in that only the separated portion is subjected to anisotropy cancellation processing.

Action As a result of the extension of the crack generated at the cut end being blocked by the anisotropy release treatment portion, substantial damage to the cut product due to the extension of the crack is effectively prevented.

Examples of Constituent Elements of the Invention As a product made of a film having anisotropy in mechanical strength in the present invention, a stretched film such as a uniaxially stretched film can be given as a typical example. Further, a product made of a film having anisotropy in mechanical strength may be contained as a constituent layer of a laminate, such as a uniaxially stretched film that constitutes a polarizing film in a polarizing plate or a surface protective film. .

The crack-preventing cut body of the present invention is obtained by subjecting only the portion separated by a predetermined distance from the cut end in the direction intersecting the direction in which the mechanical strength of the product is large to the anisotropic release treatment. The anisotropy canceling portion is usually provided near the cut edge. For example, as shown in Figure 1a,
In the anisotropic substrate 1 composed of a uniaxially stretched film having a stretching ratio of 2/1 or more and a longitudinal stretching ratio of 5% or more, the longitudinal direction with a high stretching ratio (long direction in the figure) is the direction with a large mechanical strength. Since it is (arrow), for the plurality of holes 2 provided in the width direction of the anisotropic substrate 1, the anisotropy cancellation processing portion 3 is provided in a strip shape on the substrate center side in the vicinity of the hole stomach portion. 1b, 1c,
FIG. 1d shows another example of attachment of another anisotropy canceling treatment portion 3, in which the direction in which the mechanical strength of the anisotropic substrate 1 is large due to the holes provided in the anisotropic substrate 1 in an arbitrary form. The anisotropy cancellation processing portion 3 is provided in the vicinity of the cut portion in an appropriate state according to the form of the cut portion with respect to the cut portion that is orthogonal or oblique to the (arrow). Arrows 4 in each figure indicate the directions of cracks generated due to the formation of holes.
It should be noted that in FIG. 1a, the anisotropy release treated portion 3'for the portion of the crack 4 extending to the outside of the substrate due to the hole 2 may be provided as necessary depending on the purpose of use of the substrate.

As a method of the anisotropy releasing treatment in the present invention, an appropriate method such as a heat treatment method or a treatment method with a solvent is used according to the material of the film having anisotropy. Generally, a heat treatment method is preferably used from the viewpoints of treatment efficiency, the range of treatable objects, and the like. Specific examples of the heat treatment method include a method of directly heating a predetermined processing target portion to a melting point or a softening point or higher, a method of contacting a heated material having a melting point or a softening point or higher, and a pressing at a temperature of the melting point or softening point or higher. The method etc. can be mentioned. As in the case of the above-mentioned polarizing plate, when the portion to be treated in the cut body as a product made of a film having anisotropy in mechanical strength is included as a constituent layer of the laminate, its anisotropy releasing treatment May be performed in the state of a laminate. Further, the polarizing plate described above is a good example, but the cut body to be treated has a thermal expansion coefficient,
When it is laminated with a material that has significantly different physical properties such as shrinkage, when punching and punching this laminate as a target, in addition to the constituent layer consisting of a film with anisotropy in mechanical strength Fine cracks that develop into cracks may also occur in other constituent layers in the stretching direction of the anisotropic material or in the direction of high mechanical strength. In such a case, the above-mentioned heat treatment may be performed on the entire laminate or all the constituent layers that generate cracks.

The processing width of the anisotropy releasing treatment is usually 0.5 to 5, but may be appropriately determined depending on the usage conditions such as the purpose of use of the cut body.

EFFECTS OF THE INVENTION According to the present invention, the anisotropy canceling treatment is applied to the cut portion in the direction intersecting the direction in which the mechanical strength of the cut body made of a film having anisotropy in mechanical strength is large. Therefore, even if cracks in a direction generally along the direction of large mechanical strength caused by drilling etc. develop into cracks due to stress due to environmental changes and expand, cracks occur in the anisotropy release treatment part. Extension is effectively prevented.

In addition, the intrusion of moisture or the like through the cracks is prevented, and the deterioration of the material or the laminate due to the intrusion is suppressed or prevented. The effect of preventing (suppressing) alteration is particularly significant in the polarizing plate.

Examples Example 1 A polyvinyl alcohol film having a thickness of 100 μm was stretched 5 times in water and then dyed with iodine to obtain a polarizer having a thickness of 30 μm. Then, a 0.1 mm-thick acrylic plate was attached to both sides of this polarizer with an adhesive to form a polarizing plate.

Next, this polarizing plate was cut with scissors in a direction orthogonal to the stretching direction of the polarizer. At this time, when the cut portion formed was observed with an optical microscope, many fine cracks having a length of 0.1 to 0.2 mm were found in a direction substantially along the stretching direction of the polarizer.

Then, after pressing all of the direction 10 mm away from the cut portion in a direction intersecting with the direction of high mechanical strength at 260 ° C. for 5 seconds to form an anisotropy release treated portion having a width of 3 mm,
The polarizing plate was dried at 100 ° C. for 1 hour, then immersed in water at 50 ° C. for about 10 minutes and taken out.

Comparative Example 1 A dried-immersed product of a polarizing plate was obtained in the same manner as in Example 1 except that the anisotropic release treatment was not performed.

Example 2 A polarizing plate was obtained by sticking a 100 μm thick triacetyl cellulose film on both sides of a polarizer similar to that in Example 1 with an adhesive.

Next, this polarizing plate was cut with scissors in a direction orthogonal to the stretching direction of the polarizer. In addition, in the cutting portion, the first embodiment
Similar cracks were found by optical microscopy.

Then, press all of the direction 10 mm away from the cut part in the direction intersecting with the direction of high mechanical strength at 260 ° C. for 5 seconds to form an anisotropy release processed part with a width of 3 mm, and then on one side of it. A pressure-sensitive adhesive was provided in a thickness of 30 μm, a glass plate was stuck to this, the resulting laminate was dried in vacuum at 60 ° C. for about 24 hours, and then immersed in water at 50 ° C. for about 10 minutes and taken out.

Comparative Example 2 A dried-immersed product of a polarizing plate was obtained in the same manner as in Example 2 except that the anisotropic release treatment was not performed.

Observation Evaluation The degree of crack extension was examined for the dried-immersed products of the polarizing plates obtained in Examples and Comparative Examples. The results are shown in the table.

[Brief description of drawings]

FIGS. 1a, 1b, 1c and 1d are plan views of the embodiment, and FIG. 2 is a plan view of the comparative example. 1: Anisotropic substrate, 2: Hole, 3,3 ': Anisotropy release processing part, 4:
Crack direction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-223121 (JP, A) JP-A-60-114500 (JP, A) JP-A-60-31703 (JP, A) JP-A-60- 67099 (JP, A) JP-A-61-230923 (JP, A)

Claims (5)

[Claims] 1. A product comprising a film having anisotropy in mechanical strength, which has a cutting end in a direction intersecting with a direction having a large mechanical strength, is different only in a portion separated from the cutting end by a predetermined distance. A crack-preventing cut body, which is characterized by being subjected to an orientation releasing process. 2. The cut body according to claim 1, wherein the film having anisotropy in mechanical strength is a uniaxially stretched film. 3. The cut body according to claim 2, wherein the cut body is included as a constituent layer of the laminate. 4. A laminate according to claim 3, wherein the laminate is a polarizing plate.
Sectioned body. 5. The cut body according to claim 1, wherein the anisotropy releasing treatment is a heat treatment.