JPH0352935A - Drawn film of synthetic resin - Google Patents

Abstract

PURPOSE:To obtain the subject film for a magnetic tape of photographic film, etc., having smoothness in one surface and slipperiness in other surface together with preventing decrease of transparency and generation of pinhole of film by making a film to specific roughened surface state with dispersing inorganic particles in a resin in a specific ratio. CONSTITUTION:(B) 0.01-3wt.% inorganic particles (e.g. titanium dioxide) having 0.1-8mum averaged particle diameter are dispersed in (A) 100wt.% resin component (e.g. a polyester-based resin mainly composed of polyethylene terephthalate) to afford the aimed film having roughened surface of the film of Ra1>1.5Ra2 and Rz1>1.2Rz2 (Ra1 is averaged roughness of center line in a surface of the film; Ra2 is averaged roughness of center line in other surface of the film; Rz1 is averaged roughness of 10 points in a surface of the film; Rz2 is averaged roughness of 10 points in other surface of the film).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synthetic resin stretched film in which the front and back surfaces of the film have different surface roughness. Such films can be used, for example, as base paper for thermal stencil printing, dielectric materials for capacitors, magnetic tape base materials, photographic film base materials, and the like. [Prior Art] Synthetic resin films, especially films made of thermoplastic resins such as polyester resins, polyolefin resins, polyamide resins, etc., especially stretched films of polyester resins, have good mechanical properties, heat resistance, and chemical resistance. Also, because of its excellent dimensional stability, it is used in various fields as a film for heat-sensitive stencil printing, capacitors, packaging, magnetic tape, photography, etc. Films used for these applications are required to have a high level of surface slipperiness and surface abrasion resistance, so as an improvement technology, a film is formed using a resin containing inorganic fine particles, and the film surface is coated with fine particles. The method of adding protrusions is widely known. For example, JP-A-52-133356, JP-A-55
-54346 publication has an average particle diameter of 0.01 to 10 μm
of inorganic particles from 0.01 to 100g of resin component
A manufacturing method has been proposed in which the film is dispersed at a ratio of 3% by weight and then coated to obtain a film with a roughened film surface. However, with this manufacturing method, when fine particles are used, the surface roughness is insufficient, and when coarse particles are used, especially when a large amount is added, the film properties deteriorate and a good quality film cannot be obtained. Furthermore, the resulting film is prone to defects such as pinholes, increased water vapor permeability, and decreased breakdown voltage. Furthermore, the surface roughness of this type of film is almost the same on both sides. Examples of the above-mentioned improvement methods include methods described in JP-A-60-255410 and JP-A-61-130043. This method proposes that two layers of resin to which inorganic particles have been added are laminated on a central layer of resin to which no inorganic particles have been added, stretched in a three-layer structure, and then the surface film is peeled off. Based on this method, there is an advantage that the stretchability of the film is improved and the occurrence of pinholes can be prevented. However, there is no difference in the surface roughness of the obtained film between the front and back sides. On the other hand, Japanese Patent Application Laid-Open No. 58-38158 proposes a method in which a water-soluble polymer or the like is applied to one side of the film after stretching or film, and worm-like protrusions are formed on the applied surface. However, this method has the disadvantage that it is difficult to dry and fix the applied material and it is difficult to form stable protrusions. The basic manufacturing method of the present invention is the above-mentioned Japanese Patent Application Laid-open No. 60-2
This method is based on the method of making a three-layer film and peeling it off as described in Japanese Patent Application Laid-open No. 55410 and Japanese Patent Application Laid-open No. 130043/1982, but it mainly involves identifying the viscosity difference between adjacent resins during extrusion flow. By adding measures such as keeping the surface roughness within a certain range, they were finally able to complete the process, and they succeeded in completing a new film in which the surface roughness of one side of the film is always greater than the surface roughness of the other surface. [Problem to be solved by the invention] With conventional films, when the roughness of one surface is satisfied, the other surfaces also have the same roughness. When used for tape rewinding and rewinding, the rough surface of the film has sufficient slipperiness to be used for winding and rewinding the tape. There is a problem that the shape protrudes and causes a loss of magnetic signals. Furthermore, when this film is used as a film for heat-sensitive stencil paper, for example, it is required that the thermal head move without applying large resistance to the film in order to avoid promoting the stick phenomenon. Another problem in meeting this requirement is that the roughness becomes an obstacle and deteriorates the bonding with the porous support.

Furthermore, in general, when a high degree of roughness is required on the film surface due to the need to thicken the coating layer or vapor deposited layer, there is a difference between a case where the particles are distributed in the same way on both sides and a case where the particles are distributed on one side. requires the addition of larger amounts of particles or the use of larger particle sizes. Addition of a large amount of these particles or use of large particle sizes poses problems such as a decrease in the transparency of the film or the occurrence of pinholes. [Means for solving the problem] Inorganic particles with an average particle diameter of 0.1 to 8 μm have a resin component amount of 1
A stretched film of Hewei resin dispersed at a ratio of 0.01 to 3% by weight based on 0.0g, and the condition of the rough surface of the film formed of the above-mentioned inorganic particles satisfies the following relational expression. This is a stretched Hewei resin film that is characterized by: Rat > 1.5 Rat, and Rz, > 1.2
Rzz [However, Ra. is the centerline average roughness of one surface of the film, Rag is the centerline average roughness of the other surface of the film, Rz+ is the ten point average roughness of one surface of the film, Rz. represents the ten-point average roughness of the other surface of the film. ] In describing the content of the present invention, for convenience of explanation, the method for producing the film of the present invention will be explained first.

In producing the film of the present invention, inorganic particles having an average particle diameter of 0.1 to 8 μm may be dispersed in a thermoplastic synthetic resin at a ratio of 0.01 to 3% by weight per 100 g of resin. For example, it is based on the same technical idea as the method described in Japanese Patent Application Laid-open Nos. 52-133356 and 55-54346. Regarding the selection of particle diameter, it is described in Japanese Patent Laid-Open No. 63-286396 that the particle diameter is selected from a range of particle diameters from 0.5 to 2.5 times the target thickness. However, in the present invention, the average particle diameter is 0. 1~8μm
From the range of 0 to 0 for film thickness. It is desirable to select and use particles with a particle diameter of 1 to 2.5 times.

The synthetic resin dispersed with inorganic particles is melted and extruded in an extruder. At this time, two extruders were prepared,
In one extruder, the dispersed resin is fed into one circular guide and merged to form a three-layer resin in which two layers of the dispersed resin are attached on both sides of the core layer. A cylindrical coextrusion is carried out, which is once cooled, then heated to the stretching temperature and stretched to form a three-layer stretched film. Thereafter, the two surface layers of the three-layer structure film are peeled off from the core layer, and the two surface layers are utilized. Therefore, the basic idea of this extrusion film formation is the same as that described in the examples of JP-A-60-255410 and JP-A-61-130043, for example. However, the differences between the conventional method and the method of the present invention in terms of manufacturing method are: (1) The resin used for the core layer has a Vicat softening point (according to ASTM 01525) of 100°C or less, and the Vicat softening point of the resin for the surface layer is 100°C or less. Using a resin with a lower value of Vicat softening point.

■ Melt viscosity of core layer resin (B) and surface layer resin (M) measured under the same conditions as the temperature and shear rate near the extrusion die lip VI (B), Vl (M) C unit: so as to be within the range Choose the right resin.

■ The thickness of the core layer must be 5 to 10 times the thickness of one surface layer. ■ Use an extrusion die with a flow path such that the residence time in the flow path after the three-layer resin is laminated within the extrusion die until it is extruded is in the range of 15 to 40 seconds. The goal is to select conditions that meet at least three items. By doing so, when the three-layer film is peeled off, a film is formed in which the surface of the surface layer that was in contact with the central layer has a higher roughness than the surface of the surface that was in contact with the atmosphere. It becomes. Although the phenomenon mechanism of this uneven surface roughness has not yet been completely clarified, the present inventors have discovered that when the laminated resin is spread widely within the goo and is extruded from the lip part, During flow, the distribution of particles dispersed in the surface layer is biased toward the center layer due to the difference in shear rate that occurs between the resins, and this bias in the particle distribution occurs during the stretching process. We estimate that this is a phenomenon that is further promoted and protrudes toward the central layer side. In any case, this phenomenon of unbalanced film is a surprising phenomenon that was first investigated by the present inventors, and by utilizing this phenomenon, the film of the present invention was first completed. However, the film of the present invention does not have the above-mentioned manufacturing method. This is because the present invention has disclosed that the above-mentioned phenomenon mechanism of different surface roughness is based on the uneven distribution of dispersed inorganic particles. This is because other methods can be easily devised by those skilled in the art. Next, the novel film of the present invention obtained in this manner will be explained. As is clear from the description of the manufacturing method, the film of the present invention obtained by the above-mentioned manufacturing method contains inorganic particles with an average particle diameter of 0.1 to 8 μm per 11100 g of resin. It is effective from a stretched synthetic resin film in which the resin is dispersed at a ratio of ~3% by weight. FIG. 1 is a schematic diagram showing an enlarged cross section in the thickness direction, conceptually showing the structure of the film of the present invention. X in the figure. χ1...κ represents the terms of the highest protrusions from the highest protrusion to the fifth protrusion on one surface side existing in the determined length (L) of the film (sample). , Yl+ Yz'...Y, means the existence of deep bottoms from the deepest valley bottom on one surface side to the fifth deepest valley bottom on the surface side, as described above. X7, X;,...X; and Yrr y;,
...Y; indicates the term of the protrusion and the bottom of the valley on the other surface side, which were selected in the same manner as on the one surface side. Therefore, there are protrusions and shallow valley bottoms lower than these, but these are omitted in the figure.
The most important feature of the film of the present invention is that, as can be seen from Figure 1, the condition of the rough surface of the film where the inorganic particles are formed differs greatly between the front and back sides of the film. In the present invention, this condition is expressed by the relational expression Ral > 1.5 Rag and Rzl > 1.2
This is indicated by specifying that it is Rzz. To explain this point using Fig. 1, in this case, Ra+ of one surface,
The Rat of the other surfaces is usually expressed as the "center line average roughness" and is a value determined as follows, as explained with reference to FIG. 1 showing the film of the present invention. In FIG. 1, first, parallel lines Y and Y' are lines drawn at positions where the area of the protrusion and the area of the valley at a certain length (L) on one surface and the other surface are the same value. Then, the peaks and valleys that deviate from each of the average lines, ¥, and "Y' are arranged on one side of each average line in the direction of the protrusion, and the values obtained by averaging the areas are the lines P1 and P', respectively. In the figure, Ra and Ra. are the values shown as the bias between -×'' and P and the bias between Y' and P'. In other words, this bias (Ra) corresponds to the value when the direction of the protrusion is the Y axis and the direction of the film length (L) is the X axis. Also, RZI is x4 and YSt in Figure 1, Xs and Y4
, XI and Y3. Rz. is the ten-point average roughness (height) of the other surface obtained in the same manner as above. Therefore, Ra+>1. 5 Rat means that the centerline average roughness (height) of one surface determined as described above is at least 1.5 times larger than the centerline average roughness (height) of the other surface. It means something. This consideration of 1.5 times or more is a sufficient condition for application to applications that require different physical properties on the front and back sides, and there are no known products that have a slight difference in roughness between the front and back sides. This is a consideration to avoid inclusion. Furthermore, it has been confirmed through experiments by the present inventors that the upper limit can be up to 7 times. Similarly, Rzl>1 in the present invention. 2 R
The meaning of zg is the ten-point average roughness (height) corresponding to the dimensions of the peaks and valleys.
Also, this 1 means that the value of one surface is at least 1.2 times coarser (higher) than the value of the other surface.
．． The significance of 2 times or more is a sufficient condition for application to applications that require different physical properties on the front and back sides, and is a consideration to avoid including known roughness that is slightly different between the front and back sides. It has been confirmed that the upper limit can be up to 6 times. The present invention attempts to clearly express the difference in roughness between the front and back surfaces of the film using the values of both Ra and Rz. The measurement method for this item is JIS-8-060.
1. The value of the film of the present invention determined by this measurement method is that the value of Rag (center line average roughness of one surface of the film) is 0.01 to 3 μcm.
, Rat (center line average roughness of other surfaces of the film)
The value of RZI (ten point average roughness of one surface of the film) is 0.02 to 30a.
It has been confirmed that the values of rm and Rzz (ten-point average roughness of the other surface of the film) are 0.015 to 20μ. The synthetic resin referred to in the present invention is a thermoplastic resin, and specifically includes polyester resin, polyolefin resin, polyamedo resin, and the like. In particular, a polyester resin is desirable, and from the viewpoint of obtaining high slip properties, a polyester resin containing polyethylene terephthalate as its main component is even more desirable.

The inorganic particles in the present invention are not particularly limited. Specific examples include titanium oxide, calcium carbonate, talc, silica, and alumina. Two or more of these may be used as a mixture, and when a mixture of two or more is used, the average particle diameter refers to the average particle diameter of the inorganic particles having the largest average particle diameter among them. Also, the amount added is 0
If it is less than 0.01% by weight, both surfaces will become smooth, which is not preferable. Also, 3
If it exceeds % by weight, both surfaces become rough and there is no difference, which is not preferable. From the viewpoint of increasing the difference in properties between the front and back surfaces, the content is more preferably in the range of 0.05 to 1% by weight.

[Action of the invention]

In the film of the present invention, since the inorganic particles are distributed to one side, the film is slightly smaller than that of the conventional method.
Particles with a particle size in the range of 8 μm are mixed with a slightly smaller amount of 0 than before.
．． Sufficient surface roughness can be formed with an addition amount of 0.01 to 3% by weight (per 100g of resin). This advantage, combined with the effect of stretching the film in a laminated state, prevents the formation of bottle holes in the resulting film and prevents deterioration of transparency.

In addition, since the film of the present invention has different roughness on one surface and the other surface, it has different effects such as bondability with other substances and slipperiness with other substances. show.

Furthermore, when the film of the present invention is applied to a magnetic tape, for example, by coating the magnetic layer on the less rough surface, the slipperiness of the more rough surface can be improved. It compensates for the poor slippage of the magnetic layer surface, and prevents the film from squeaks and damage to the magnetic layer that occur when the film is wound up and unwound. It is highly useful because it prevents the loss of magnetic signals caused by large protrusions.

Furthermore, when the film of the present invention is applied to, for example, a film for heat-sensitive stencil printing base paper, a porous support is bonded to another relatively flat surface, and a single layer with improved slipperiness due to the size of the protrusions is bonded to another relatively flat surface. When used so that the surface is in contact with the thermal head, it is useful in that it prevents the promotion of the stick phenomenon that occurs between the thermal head and the base paper, yet does not impede the bonding properties of the support. [Example] The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

In addition, the method of measuring the characteristic value and the method of evaluating the effect of the present invention are as follows.

(1) Average particle size The value was taken as the cumulative 50% point in the equivalent spherical diameter distribution measured by a centrifugal sedimentation type particle size distribution analyzer (manufactured by Shimadzu Corporation).

(2) Center line average roughness (Ra) and ten point average roughness (Rz
) Specified using a contact type surface roughness meter (Tokyo Seimitsu Surfcocom 550A) according to JIS-B-0601. The cutoff was 0.08 am, and the measurement length was 0.5 mm. (3)
Melt viscosity values (VI) were determined at each temperature and shear rate using a melt viscosity capillary fluidity tester (Toyo Seiki Capillograph). The cavity used was a diameter lam and a length 10 mm (Model E type). Example 1 The surface layer (M layer) was made of monomers in which the acid part was mainly terephthalic acid, and the alcohol part was 30 mol% 1,4 cyclohexane-dimethanol, 70 mol% ethylene glycol, etc. A copolymerized polyester of substantially poor quality [Vicat softening point 82°C, T 181°C, intrinsic viscosity 0.75 (KO Ro^ of Eastman Kodak Company)
R@PP. TG6763)), a composition was prepared in which 0.2% by weight of silica particles with an average particle diameter of 4 μm were added to the above resin as inorganic particles, and then ethylene-vinyl acetate copolymer was added as a core layer (layer B). Coalescence (vinyl acetate group content 1
4-fold flea%, Vicat softening point 81"C, mp95℃) 70
Weight%, 15% by weight of ethylene-α-olefin copolymer elastomer (amorphous, Vicat softening point 40°C or less) and crystalline polypropylene (Vicat softening point 138°C, m
A 15% by weight mixed resin (the Vicat softening point of this mixed resin was 72°C) was prepared (143°C, 4% random copolymerization of ethylene). These two types of resin are melted in separate extruders, and CM/B/
M) was extruded using a 3lIl structure so that the thickness was [50/300/50) (μm) in the above order, and the material was rapidly cooled and solidified with a refrigerant to form a tube-shaped original fabric. Furthermore, the residence time in the flow path from when the three-layer resin in the M-layer and B-layer resins were laminated near the die lip until extrusion was 37 seconds. This tubular raw fabric was passed between two pairs of differential nip rolls and heated to 90'C-110 in the heating zone.
゜Adjust the temperature in the cooling part of C1 to 20゜C, adjust the temperature to the optimal stretching state with the air ring and hood, fill the specified pressurized air inside the tube, and spread it about 5 times horizontally.
It was simultaneously biaxially stretched approximately 5 times vertically. The obtained film was a uniform film, which was slit at both ends and wound into a roll.

Next, the desired surface layer was peeled off from this roll and the core layer was removed to obtain two films with a thickness of 2 μm. Ra and Rz were measured on the front and back sides of this film using the method described in the text, and the results are shown in Table 1. Next, a porous support was adhered to the smooth side of the obtained film to make a heat-sensitive stencil paper, and when perforated with a thermal head, the movement of the thermal head was smooth and no stickiness occurred. A good perforated product was obtained. Further, the adhesive strength between the film and the porous support was 23 (g/25 peng).

Example 2 Instead of silica in Example 1, an average particle size of 1.2μ
1 calcium carbonate 0. The properties of the film obtained in the same manner as in Example 1 except that 2% by weight was used were the center line average roughness Ra. is 0.10 (μm), Rat is 0.
06 (, czm), Rat/Rat = 1.67, which satisfies the relational expression (Ra+ > 1.5 Rat), but the ten-point average roughness of both surfaces, Rz, is 1.7.
6 (μni), RZ2 is 1.28 (μm), Rz+
/Rzz=1.37, and the relational expression (Rz+>1.2Rz
z).

In all Examples, by satisfying the conditions of the present invention, a high quality film was obtained that satisfies different requirements on the front and back.

Comparative Example 1 The center layer in Example 1 was omitted, and a single surface layer was tried to be stretched, but the film broke when the thickness was less than 8 μm and stretching could not be performed. - At 8 μm, it was very easy to puncture, and only a non-uniform film with a length of about 2 to 3 m could be obtained. The film properties in the parts that can be evaluated are the center line average roughness R
a. , Rat are 0.20 (μm) and 0.20 (μm), respectively.
18 (μffl), ten-point average roughness RZI%RZ. are 2.66 (μm), 2.57 (μI1), and Ra., respectively.
/Ra. =1.11, Rz+/Rz. = 1.04, which did not satisfy the relational expression, and there was no difference in the characteristics between the front and back surfaces.

When this film was made into a heat-sensitive stencil paper in the same manner as in Example 1 and perforated with a thermal head, the thermal head did not slide well and the paper was damaged. Furthermore, the adhesive strength between the film and the porous support decreased to 18 (g/25 feet). Comparative Example 2 Surface 71! (M layer) contains carnauba wax in polyethylene terephthalate (intrinsic viscosity 0.62 dll/g, mp 259°C) so that the content in the film is 0.5% by weight, and 0.5% dry silica as inorganic particles. % by weight, and then as a core layer, a propylene-ethylene copolymer (intrinsic viscosity 1.6
5di/g, mp 120″C, 6% by weight random copolymerization of ethylene) was prepared.

These two types of resin are melt-extruded at 280'C using separate extruders, and each melt is merged in a T-shaped nozzle to form a three-layer structure (M/B/M) with different thicknesses. Expressed in the above order, it was extruded so as to have (8/2 3 0/8) (μm), and this was wound around a cooling drum at 25°C and cooled and solidified to form a three-layer laminated sheet.

This sheet was heated to 90°C, stretched 3.4 times in the longitudinal direction, and immediately cooled to 30°C. Next, it was heated again to 100°C, stretched 4.6 times in the width direction, and while maintaining the tension, was heat treated at a temperature of 200°C for 6 seconds, slowly cooled, cooled to room temperature, and rolled up. . The obtained film had surface layers on both sides each having a thickness of 0.5 μm,
The laminated film had a core layer thickness of 15 μm. When the surface layer was peeled off, the peelability was good.

Center line average roughness Ra+, Rat of both surfaces of this film
are 0.050 (μn+) and 0.035 (μ*), respectively.
, ten-point average roughness Rz, , Rz. are each 0.22
(μIm), 0.21 (μm), Rat/Ra. =1
．． 43, Rz. /Rzt = 1.05, and both relational expressions (Ral>1.5Raz, RZI>1.2 Rz
z), and there was no significant difference in the properties between the front and back surfaces (this comparative example is a reproduction of the example described in JP-A-61-130043).

Comparative Example 3 The surface layer (M layer) resin in Comparative Example 2 had an average particle size of 0.0.
3 μm of silica fine particles o. tm amount% and containing 0.1% by weight of sodium moncitate, core Fi
Propylene-ethylene random copolymer (mp 12 5°C, ethylene content 5.5
% by weight) containing 0.15% by weight of polyoxyethylene-modified silicone oil (denaturation rate: 80%, viscosity at 25°C: 1800 centistokes).

Thickness (5/150/
5] (μm), and a laminated film was obtained in the same manner as in Comparative Example 2, except that the stretching ratio was 3.1 times in the longitudinal direction and 3.2 times in the width direction. The surface layer thickness of the obtained laminated film was 0.5 μm, and the center line average roughness Ra, ,
Rat is 0.020 (μI1) and 0.015 (
u m), ten-point average roughness Rz. , RZ! are 0.11 (μm), 0.10 (μm), Rat/
Rag = 1.33, Rzl/Rzz = 1.1. Similar to Comparative Example 2, this Comparative Example also did not provide a film with significantly different physical properties on the front and back sides, and had poor adaptability when different properties were required on the front and back sides. (This comparative example is
This is a reproduction of the example described in Publication No. 255410. ) The following margins [Effects of the Invention] When the film of the present invention is used as a film for magnetic tape, photographic film, condenser, heat-sensitive stencil printing base paper, etc., the film has smoothness on one surface and smoothness on the other surface. It is possible to provide properties such as slipperiness that match different levels of requirements. Additionally, compared to a film in which inorganic particles are distributed on both sides of the film, the added amount and particle size of the inorganic particles can be reduced, making it possible to prevent a decrease in the transparency of the film and the occurrence of pinholes. Further, the film of the present invention is something that has been desired in the industry but has not existed, so the present invention is an excellent invention that is useful to the industry.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing an enlarged cross section of the structure of the film of the present invention cut in the thickness direction. In the figure, Xl+X2
+...X, is the top of the protrusion on one side that exists along the length of the film, YI+YZ+...Y
, is the bottom of the trough on the side of - which exists in the length L of the film, and X;, X2+... Top, m YF+ ・
. . . Y; indicates the bottom of another troublesome trough that exists along the length of the film.

Claims (1)

[Scope of Claims] 1. A stretched synthetic resin film in which inorganic particles with an average particle diameter of 0.1 to 8 μm are dispersed in a proportion of 0.01 to 3% by weight based on 100 g of resin component, comprising: A synthetic resin stretched film, characterized in that a rough surface of the film formed of inorganic particles satisfies the following relational expression. Ra_1>1.5Ra_2 and Rz_1>1.2R
z_2 [However, Ra_1 is the centerline average roughness of one side of the film, Ra_2 is the centerline average roughness of the other side of the film, and Rz_1 is the ten-point average roughness of one side of the film. Rz_2 indicates the ten-point average roughness of the other surface of the film. ]