JPH0452204B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diagonally uniaxially oriented molecularly oriented film or a laminate thereof that is hard to curl and has excellent physical strength. Films with diagonal uniaxial molecular orientation (including uniaxial stretching) inherently have the disadvantage that they have residual stress in the diagonal direction and tend to curl. Another major drawback is that the tear strength in the direction of the stretching axis is low, which limits its use in packaging materials and the like. One way to improve tear strength is to
It is known to laminate (cross-laminate) more than one layer of stretched films. (For example, Jitsukaiaki
55-21168, Publication Act 1987-19087, Japanese Patent Publication No. 56-32139,
(Japanese Patent Publication No. 57-38134, etc.) The cross lamination method is
It is certainly effective in improving tear strength. However, it is not sufficient to improve the curling property, and further improvements are desired in addition to other disadvantages caused by lamination (high cost, increased thickness, etc.). The present invention aims to solve the above-mentioned problems. In the present invention, as a method to solve this curling problem, grooves are formed to intersect the molecular orientation axis of a diagonally uniaxially uniaxially oriented film, and both the curling property and the tear strength are improved at the same time. That is, in the present invention, the longitudinal direction of the unevenness with respect to the orientation axis of the obliquely uniaxial molecularly oriented thermoplastic resin film is 5.
To provide a film or a laminated film characterized in that it has a large number of groove-like irregularities forming an angle of 85 degrees and having a depth of 3 to 70 μm. The grooves are typically formed as grooves transverse to the film's longitudinal axis, preferably intersecting the film's longitudinal axis at 30 to 60 degrees. In general, diagonally uniaxial molecularly oriented thermoplastic resin films are uniaxially stretched diagonally (5 to 85
It is manufactured by applying A typical example is one in which the film is uniaxially stretched at an angle of 45 degrees to the longitudinal axis. Although forming irregularities on a film itself has been widely practiced in the past, there is no known method that focuses on the relationship with the molecular orientation axis to improve curling properties and tear strength, as in the present invention. In fact, among shaping methods, diagonal curls cannot be corrected on silky or matte surfaces, and it is not effective on grooves parallel to the molecular orientation axis.
It is unclear why the curling property is improved by forming grooves that intersect with the molecular orientation axis, but the triangular structure formed by the molecular orientation axis and the groove is
It is presumed that this improves physical strength and curling properties. The angle of the groove with respect to the long axis of the film is preferably 75 to 90 degrees.If the groove is parallel to the long axis (vertical groove), wrinkles will occur, especially in long roll films, making the production itself difficult and causing loss. Most of them are not practical. A diagonally uniaxially stretched film can be made by direct diagonally stretching, but it can also be obtained by slitting a longitudinally uniaxially stretched blown tubular film into a spiral shape. It is easiest to form the grooves using an embossing roll, but a method using an embossing plate may also be used. The angle α (see Figure 11) formed by the groove with respect to the molecular orientation axis of the film is 5 to 85 degrees, preferably 30 to 85 degrees.
The angle is 60 degrees, and if it exceeds 85 degrees or less than 5 degrees, a sufficient curl prevention effect will not occur. The shape of the groove is not particularly limited, but the cross section of the groove may be wavy, trapezoidal, triangular, or other polygonal. Some preferred examples of groove shapes are shown in Figures 12 to 1.
It is shown in Figure 9. The grooves can be formed on one side (FIGS. 5, 7, and 10) or both sides (4th, 6th, 8th, and 9th sides) of the film. When grooves are formed on both sides, the grooves on both sides may be parallel to each other or may intersect, but the angle of intersection with the molecular orientation axis of the film should be within the above range. As illustrated in FIG. 23, the grooves are typically continuous grooves, but they do not necessarily have to be continuous and may be composed of a combination of discontinuous grooves as shown in FIG. 22. Furthermore, a broken line shape or a chain line shape is also sufficiently effective.
However, it is necessary to ensure a sufficient groove length in the predetermined direction. The pitch of the grooves and the height between the valleys and crests of the unevenness are selected depending on the film material, thickness, etc. The pitch of the groove is
It may be the same pitch or different pitches. In the case of equal pitch, for example, 0.1 to 3 mm, preferably 0.1 to 2 mm,
Most preferably it is 0.5-1.5 mm. The thickness of the film targeted by the present invention is not particularly limited, but includes at least 10 to 200 μm (hereinafter μ means μm), preferably 20 to 70 μm. Generally, the narrower the pitch, the greater the resistance to curling, but the tear strength does not improve beyond a certain value. The depth of the groove is determined depending on the application, film thickness, etc., and is generally 1 to 50% of the film thickness.
%, preferably ratios of 5 to 25% are effective. For films in the above range, the groove depth is practically 3.
It is necessary to set it to 70 micrometers, and especially for general packaging, 5 to 50 micrometers is more preferable. Generally speaking, the deeper the grooves, the better the tear strength, curl resistance, stiffness, etc. Furthermore, the smaller the area of the remaining portions of the grooves (the peaks), the better the slip characteristics, anti-peeling voltage, etc. Although the grooved film of the present invention can be effectively used even if it is applied to a single layer of film, it is often effective to form grooves on a laminate of two or more layers (particularly when grooves are formed on both sides). The case of a laminate will be specifically explained below as an example of an embodiment of the present invention. It is known to increase the strength by laminating two layers of uniaxially stretched films so that their stretching axes intersect with each other, but the grooved stretched film of the present invention also has
You can use this method. That is, when two layers of grooved stretched films are stacked so that their stretching axes intersect at 90 degrees, the grooves are parallel to each other in the lateral direction on both the front and back sides. Such a laminate becomes more resistant to curling. In this case, the arrangement of the protrusions on the front and back sides can be arranged so that they match, as shown in Figs. 15 and 17, or the protrusions on the front side and the recesses on the back side can be arranged so that they match, as shown in Figs. 16 and 19. It is also possible to do so. In this case, the later tear strength in the lateral direction is stronger than the former, but either one can be freely selected depending on the required impact hole tear strength, gas permeability, stiffness, longitudinal and lateral sliding properties, etc. Further, the grooves (recesses) on the front and back sides may be shifted from each other. The groove is the second
As shown in Figures 0 and 21, the film may be shaped into a corrugated shape. It is also possible to make one layer a stretched film with grooves and the other layer a stretched film without grooves so that the stretching axes intersect. However, in this case, by carefully selecting the thickness of the grooved stretched film, the pitch of the grooves, the depth, etc., the resistance to curling is lower than that with double-layer grooves, but greater than that without grooves. , is sufficient for normal use. When seeking a material with low sliding properties, it is advantageous not to have grooves on one side (Fig. 10). Also,
By providing grooves on only one side of the cross-laminated film, one side may be made of a synthetic resin layer with good sliding properties (FIG. 5). The diagonally uniaxially oriented thermoplastic film to which the present invention is advantageously applied is polyethylene (HDPE,
LDPE, L-LDPE), polypropylene, polystyrene, polyvinylidene chloride, polyvinyl chloride compounds, polycarbonate, polyethylene terephthalate, polyamide, etc. Materials that tend to curl especially when diagonally uniaxially stretched, such as HDPE, polypropylene, polystyrene, etc. most suitable for Further, the grooved film of the present invention may be laminated with other films with or without grooves to form a grooved laminated film, if necessary. Other films are selected according to their respective purposes in order to further improve heat-sealing properties, light-shielding properties, strength, dimensional stability, abrasion resistance, cost suitability, etc. (FIGS. 4, 5, and 9). It is also useful to use a synthetic resin layer on one side that is easy to heat seal when a strong seal is required (Figure 4). Depending on the purpose, other flexible sheets such as paper, synthetic paper, cellophane, other synthetic resin films, metal foils, nonwoven fabrics, etc. can be laminated on the surface or in the middle of the film of the present invention (fourth, fifth,
Figure 9). When laminating these layers, an adhesive layer can be provided as appropriate (FIGS. 5, 8, 9, and 10). Further, lateral grooves may be formed in these heat-sealing layers or flexible sheets (FIG. 4). When forming grooves with an embossing roll, the depth of the grooves can be increased by increasing the pressure of the press. Furthermore, the higher the temperature of the embossing roll, the easier it is to form grooves and fix the shape, but it is necessary to avoid melting the film or causing heat shrinkage. Therefore, the temperature is 100°C or lower, usually 20 to 60°C. The same results can be obtained by preheating the film without increasing the metal roll temperature. The film of the present invention becomes a useful packaging material for photographic materials by imparting light-shielding properties to at least one layer of the diagonally uniaxially oriented thermoplastic resin film or the laminated film. This light-shielding property can be obtained by using light-shielding substances commonly used in packaging materials for photosensitive materials, such as light-shielding powders such as carbon black, metal foils such as aluminum foil, and the like. For example, thickness 20~
300 μm, particularly preferably 30 to 150 μm, stretching ratio
Carbon black is applied to a uniaxial obliquely stretched polyethylene film of 1.5 to 10 times, more preferably 2.5 to 4.5 times.
The content is 0.1 to 15 g/m ² , more preferably 1.5 to 7 g/m ² , the depth of the surface is 1 to 100 μm, more preferably 5 to 50 μm, and the pitch is 0.1 to 3 mm, more preferably 0.5
Products with ~1.5 mm horizontal grooves can be used as is as an excellent packaging material for photographic materials. In addition to adding carbon black, methods for imparting light-shielding properties to films or laminates include adding other light-shielding substances, printing, laminating layers with light-shielding properties such as paper, aluminum foil, etc. good. Other additives such as lubricants and antistatic agents may also be freely added to the film. Examples of other applications include cassette tapes, VTRs,
When making a friction sheet for tape rolls such as S-8 film, (a) a single uniaxial diagonally stretched polyethylene (HDPE) film with a thickness of 50 to 500 μm, (b) two layers of diagonally stretched polyethylene (HDPE) film so that the axes of the two layers intersect. (c) Laminated with (a) on other flexible sheets such as paper, etc. are both effective. After forming horizontal grooves with an embossing roll, an excellent friction sheet can be obtained which has the following advantages whether it is punched out parallel to the grooves or perpendicular to the grooves. The following is a comparison with the same type of film and laminate without horizontal grooves. (1) High surface strength and low wear. (2) Tear strength, especially in the direction of the stretching axis, is improved. (3) Peeling electrostatic voltage decreases. (4) Improved rigidity and tape roll holding power. (5) Improved curl resistance. (Especially useful for cassettes) (6) Improves slippage. Such effects also indicate that the present invention is useful as film-like members that require similar effects (for example, container lining materials, sliding member surface materials, cushioning materials, light shielding materials, etc.). Of course, the product of the present invention is extremely useful not only for photosensitive materials but also for general packaging materials. Examples are shown below. Stretching ratio 3.5 including 5% carbon black by weight
A non-grooved film of twice the size of a uniaxially obliquely stretched high-density polyethylene film (density 0.96 g/cm ³ , 90 μm thickness) will be referred to as Conventional Product 1 as a comparative example. As a product of the present invention, this was passed between a metal embossing roll (35°C) having 5 horizontal grooves per cm and a hard rubber roll,
Four types (1 to 4) were manufactured in which grooves with the predetermined depths shown in Table 1 were formed (intersecting angle between the groove and the stretching axis was 45 degrees). Next, as an example of a stretched axes-crossing laminate,
Uniaxial obliquely stretched high-density polyethylene film (HDPE) containing 5% carbon black at a stretching ratio of 4 times.
Conventional product 2 is made by gluing two sheets (density 0.96 g/cm ³ , thickness 40 μm) together with a 10 μm low-density polyethylene (LDPE) adhesive layer so that the stretching axes intersect at 90 degrees. A product in which lateral grooves with a depth of 15 μm (angle with the stretching axis was 45 degrees) was formed using the same method as described above was compared as Invention Product 5. Furthermore, conventional product 3 and invention product 6, in which aluminum foil was sandwiched in the middle, were manufactured. Carbon black content is 5% by weight, stretching ratio is 4 times, density is 0.96g/
cm ³ , two 40 μm thick uniaxially obliquely stretched HDPE films are coated with a 10 μm LDPE adhesive layer on both sides of a 7 μm thick aluminum foil.
Glue them together so that the crossing angle of the stretching axes is 90 degrees. This was designated as conventional product 3, and a horizontal groove with a depth of 15 μm was formed using the same method as before (the angle with the stretching axis was
45 degrees) was designated as Invention Product 6. As a result of the test, the tear strength, curl resistance, stiffness, sliding property, peeling voltage, etc. of all the products of the present invention in which horizontal grooves were formed were improved. Moreover, this effect became more pronounced as the depth of the groove increased.

[Table] Measurement method Curl value... Sheet to be tested: 5cm long and 10cm wide
A rectangular specimen of cm size was prepared, and the temperature was 20℃ and the humidity was 65℃.
After leaving the sheet under a 1 kg load plate in an atmosphere of
Read the average height A+B+C+D/4 (mm) of the four corners A, B, C, and D of the sheet from the flat plate on the scale. Tear strength...JIS P8116 Stiffness...JIS P8125 Sliding angle...Cut out a part of each sheet above.
While pasting it on the bottom of a block with the same load,
Another part of the sheet cut out in the same manner is pasted on an inclined surface, and when the block is placed on the inclined surface and the angle is changed, the angle at which the block starts to slide is read. Peeling voltage (antistatic property)...Cut out a part of each of the above sheets and paste it onto an endless belt, and place the belt between opposing rollers (upper nylon roller, lower SUS roller) with a load of 500g/12m/ Measure the amount of charge using a voltmeter when sending at a speed of 1 minute.

[Brief explanation of the drawing]

Figures 1 to 3 are conventional products, Figures 4 to 10 are sectional views of the embodiment of the present invention, Figure 11 is a schematic plan view showing an example of the molecular orientation direction and groove arrangement, and Figures 12 to 21.
The figure is a sectional view showing another example of the cross-sectional shape of the groove, and Figures 22 and 23 are perspective views showing other examples of the groove arrangement. 1a...Oblique uniaxially stretched film layer, 1b...1
A diagonally uniaxially stretched film layer that intersects a, 2...
...adhesive layer, 3... flexible sheet layer bonded to the middle of the laminated film, 4... heat seal layer, 5... flexible sheet layer provided on the surface of the laminated film.

Claims (1)

[Scope of Claims] 1. On at least one surface of a diagonally uniaxially oriented thermoplastic resin film, the longitudinal direction of the unevenness is at an angle of 5 to 85 degrees with respect to the molecular orientation axis of the molecularly oriented film, and the depth is 3 to 70 μm. A grooved film characterized by forming groove-like unevenness. 2. In a laminated film including at least one thermoplastic resin film with diagonal uniaxial molecular orientation, groove-like grooves with a depth of 3 to 70 μm and the longitudinal direction of the unevenness is at an angle of 5 to 85 degrees with respect to the molecular orientation axis of the molecular orientation film. 1. A grooved laminated film characterized in that unevenness is formed on at least one surface of the molecularly oriented film.