JPS5853419A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a slippery film of low frictional coefficient by a method wherein many projections and many dents around them are provided on the surface of a polyester film, these dents have a form by ellipse having a long diameter 2mum-50mum along the stretching direction and said projections are produced by inert inorganic compound or residual catalyst. CONSTITUTION:When unstretched film containing grains of inert inorganic compound or residual catalyst or the like is stretched uniaxially, unstretched film is designated to be preheated at a high temperature and/or the stretching magnification is set to a low level not to provide voids around the grains of uniaxially stretched film. When this film is stretched in the second axial direction, the depression 24 of the film 23 which nucleate the grains are provided. THe depression takes the form of an ellipse having a long diameter along the 2nd axis. Said long diameter is 2mum-50mum and the following formulas are designated to exist between the long diameter D(mum) and the projection occurring frequency N(pieces/ mm.<2>).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film having a smooth surface and a low coefficient of friction.

Polyester films have a variety of uses, including magnetic tape applications and electrical applications. In magnetic tape applications, especially video tape applications, a smooth film surface is required to improve electromagnetic conversion characteristics, as well as the running properties, abrasion resistance, and durability of the tape on the deck. In order to improve the friction coefficient, a low coefficient of friction is required.

Conventionally, as a technology to reduce the coefficient of friction of film,
There is a known method of imparting irregularities to the surface of a film by forming into a film a polymer to which inorganic particles are added or a polymer in which insoluble catalyst residue particles are formed.

This means reduces the contact area between the film and the object with which it comes into contact by providing protrusions on the film surface, thereby reducing frictional resistance. All of these methods actively create protrusions on the surface of the film, and it is effective to create a large number of high protrusions on the film surface in order to reduce the coefficient of friction. However, in this case, although the coefficient of friction can be lowered as the number of tall protrusions increases, when magnetic coating is applied, coating 1iii#c is also affected by the protrusions, and there is a strong possibility that the electromagnetic conversion characteristics will be deteriorated.

As a result of extensive research into a base film suitable for slippery magnetic tapes that have excellent electromagnetic conversion characteristics and a low film friction coefficient, the inventors discovered that the polyester film has a convex portion and a portion on its surface. Ta. The minute unevenness unit,
It was discovered that this problem could be solved by forming a large number of flies, and this invention was achieved.

That is, one aspect of the present invention is a polyester film having a large number of single convex units consisting of protrusions and depressions with the protrusions as cores on the surface of the film, the depressions being formed in an elliptical shape around the protrusions. The long axis of the protrusion is from 2I to sO, and the protrusion is composed of an inert inorganic compound (
This is an easily slippery polyester film with concavity and convexity units whose major axis is along the stretching direction of the film due to additives) or catalyst residues.

The present invention will be explained. In order to obtain a slippery film, the prior art has added inert inorganic compounds (e.g. silica, clay, titania, etc.) or organic compounds (e.g. calcium terephthalate, high melting point polyester) or (and) utilized catalyst residues. In contrast, the present invention is characterized in that projections and depressions are formed on the film surface. Compared to films obtained by conventional techniques having only protrusions on the surface, this has the advantage that the coefficient of friction is significantly lower and the effect of facilitating slippage is apparent.

Polyesters to which the present invention can be applied include terephthalic acid,
Refers to a polymer or copolymer obtained by condensation polymerization of an aromatic dibasic acid such as isophthalic acid, cafthalene-6-dicarboxylic acid, and a glycol such as ethylene glycol, detramethysine glycol, neopentyl glycol, etc. Typical examples of these polymers include polyethylene terephthalate, polybutylene tere-7 tallate polyethylene-4
Examples include homoprimers such as 6-naphthalene dicarboxylate, partially modified copolymers thereof, and polymer blends such as polyethylene terephthalate K (adding ethylene terephthalate/polyethylene glycol coblock copolymer). Of course, fillers, pigment colorants, antioxidants, light stabilizers, etc. can also be added to monopolymers and copolymers. Films obtained from these materials are included in the polyester film of the present invention.

The protrusions formed on the film surface of the present invention are as follows.

Particles of inorganic compound added to polio: Particles based on insoluble catalyst residue produced by polymer polymerization KvAL: Or due to the presence of both particles - Produced as the protruding nucleus generated around the protrusions referred to in the present invention. The depressions are not caused by conventional mechanical stamps such as embossing, but are caused by deformation of the film itself during the film stretching process.

When an unstretched film containing particles is stretched in the uniaxial direction, the polymer is plastically deformed without deforming one particle, so that voids are generated at the boundary between the polymer and the particles upon large deformation (stretching). When this void-containing film is first stretched in a direction (second axis direction) that is almost perpendicular to the single-axis stretching direction and summed with the biaxially oriented film, the voids that were generated during the -axis stretching are further extended in the second axis direction. As shown in FIG. 1-IK, the protrusion 21 is deformed.
A void 22 is formed around the device shape. In this case, as shown in the cross-sectional view of Figure 1-2, the particles existing in the shallow part near the film surface and the voids around them produce protrusions with the particles as the nucleus, but no depressions are formed around one particle. .

In the present invention, the above-mentioned voids are changed to depressions on the surface of the film. When axially stretching an undrawn film,
Set the stretch film preheating to a high temperature, or
or (and) by setting the stretching ratio low, so that the film after the first axial stretching has substantially no voids formed around the particles (external particles due to inorganic additives or internal particles containing catalyst residue). When the stretched film in this state is then stretched in the second axial direction, depressed portions (depressions) of the film with particles as cores are formed along the second axial direction. The major axis of the elliptical depression is along the second axis direction.

Even if a slight void is formed around the grain during the -th axis stretching, a C depression is generated with this grain as the nucleus.

The surface of the film after biaxial stretching is in the state 11 as shown in Figure 2-IC top view), and if the second axial stretching is under stretching conditions such that stress is concentrated around the particles, the depressed portion will be at the level of stress concentration. Figure 2-zCWt plane view) shows a cross section of the film near plane 111, and shows the protrusion 21 containing one particle and its long axis. 1i124 formed around the polyester film 23.

In the present invention, the depressions formed around the protrusions include pseudo-ellipsoidal depressions that are biased in the second axis direction.

In terms of improving the running properties of the magnetic tape and improving the electromagnetic conversion characteristics, it is necessary that the major axis of this recess be at least two tones, which is called the major axis of the most biased unloading.

Furthermore, if the major axis of the depression exceeds S G Jll, dropout of the magnetic tape increases, making it undesirable as a base film for a magnetic tape.

According to the present invention, the length D (β) of the depressions and depressions of the uneven units on the surface of the polyester film and the frequency N of occurrence of the uneven units (simple/-
) between.

200-N (3500゜5≦)
1) (Things of 10 150≦N<2000゜10≦
D<30 50≦N(1100゜3・≦
When O<S O When the relationship is 0≦N≦5, favorable slipperiness is exhibited, and the electromagnetic conversion characteristics are also excellent.

More preferably.

When 2≦D is 6, 3! I・≦N<2　S　o　.

When 5≦D<1・2s・≦N(150010:i
;; D (when 210, 1e≦N<5o (ID≧) When the conditions of OWN≦3 are satisfied, the base film has excellent running properties and electromagnetic properties. According to the present invention, the depressions on the film surface It is understood that frictional resistance is reduced by reducing the contact area.

In the present invention, it consists of 11 protrusions and depressions around them. It can be controlled by a.

The physical stretching method of the polyester film of the present invention will be explained. The average particle diameter of kaolin, silica, etc. is aOS ~ 5
μ Hou (preferably 13-t.

An unstretched polyester film containing (11) 1 to 10 weight of fine particles of (11) is preheated to 80 to 1 zo'c when stretched in the first axial direction. When preheating this unstretched film to about 90 to 120" CK, a hard chrome-plated roll with a matte surface or a ceramic roll is preferable. A predetermined preheating temperature can be reached under conditions such that no crystallization occurs.Of course, the unstretched film can be preheated in a non-contact manner.

Unstretched film is a-! ? Temperature from 0 to 135℃ -〇L
It is stretched at a stretching ratio of 2 times or less (preferably 2.6 to 5?L2 times). It is preferable that the drawing speed be relatively slow and the force should not exceed 156 @/am.

A stretching speed of about 3Ii110-IQO+a/heel is selected, and in the case of a low speed, the stretching temperature can be moved to a slightly lower temperature side.

Next, in the second stretching, the uniaxially oriented film is cooled once below the glass transition point, or without cooling (, l'00 to i
Preheat to a temperature of so°C, and further heat at a temperature similar to y.
Stretch it by $5 times. When the second axis stretching temperature is high, the boundaries between the concave and convex units become clear, but at low temperatures, the boundaries are often not clear.The stretching ratio in the second axis direction has a significant effect on the frequency of occurrence of the concave and convex units. If you select a second axis stretch ratio of 18 times or more, the mechanical strength in the second axis direction (Young's book) will be higher than the mechanical strength in the first axis direction. This results in a so-called tensilized film, and the slipperiness of the film tends to decrease.

If this two-wheel stretched film has insufficient mechanical strength in the 4L first axial direction, it may be further stretched by 120 to 1yo' in this direction.
Smells at a temperature of C@ degrees.

L2~1. It can also be re-extended to make a balanced film.

The biaxially oriented polyester film, which has been subjected to two-stage stretching and 3R stretching if necessary, has a temperature of 180 to 240°C (preferably 1wo to 100°C).
The vagina can be heat-fixed at a temperature of 210℃ for about 2 to 30 seconds. Note that the third stage (first axial direction) re-stretching in i*m stretching can also be performed on a film that has been heat-set.

By appropriately combining the above-mentioned stretching conditions, a slippery polyester film having an appropriate frequency of uneven units can be produced.

In the present invention, the first axial stretching direction can be either the machine direction or the width direction of the film, and the second axial stretching direction is preferably approximately perpendicular to the first axial direction. High-stage (multi-stage) stretching can be performed by adding JC-stretching in the C- or I-axis direction.

In this case 4. The shape of the protrusions and convexes on the film surface varies somewhat, c4. Since it remains intact, it is possible to maintain the electromagnetic conversion characteristics as a magnetic tape and to maintain the film (
(tape) running properties (low coefficient of friction) are maintained.

The conditions for stretching the film to form such surface depressions are as follows:
There is a tendency to make the film l1M relatively smooth, and as a result, the electromagnetic conversion characteristics as a magnetic tape are reduced.

In other words, the poester film of the present invention has the ability to be used as a base filler for magnetic tapes, and does not cause drudging or color noise even when a magnetic recording layer is provided because the film surface is relatively flat. In addition, since the tape has depressions to reduce the force around the protrusions, the contact area with magnetic heads, guide seals, and other films as a tape is further reduced, and the low protrusions on the film surface also enhance the sliding effect. There is.

Since the surface of the polyester film of the present invention has depressions in addition to protrusions, the electromagnetic conversion characteristics can be maintained at a high level when compared with the conventional film having only protrusions, and the adverse effects caused by some excessive unevenness units can be maintained. has the advantage of being avoided.

The physical property measurement method for zero-start Ijl is as follows.

OL Measurement method for uneven parts A thin layer of aluminum vapor deposited on the surface of the film is measured using a differential interference H microscope device (for example, a N1kon differential interference microscope AL).
1) to take a photograph and measure its size using a scale.

(2) Surface roughness CLA Surface roughness CLA (Csmt@r Lim
The eAv@rag·) value is measured using the following method.

The roughened film is measured using, for example, a stylus type surface roughening needle (SURFCOM 1B) manufactured by Tokyo Seimitsu Co., Ltd., and the radius of the needle is measured. all, under the condition of load 1011F.

Determine the film roughness curve, extract a part of measurement length L (reference length 2 lengths), take the center line of this punched part as X1m, take the vertical magnification direction as the Y axis, and calculate the roughness -liI as Y. When expressed as = fω, the value given by the linear equation is expressed in units of μ.

O This measurement was performed on 8 samples.

Exclude S values from the one with the largest value and express it as the average value of the five values,
Note that #I4 constant is performed for both the vertical direction and the horizontal direction, and the average value of both is used.

(3) Friction coefficient as shown in Figure 4 (outer diameter S x 18-s stainless steel 8U8304 fixed rod (surface roughness CLA Tomio) in an atmosphere of 2@℃ and relative temperature 60%. /2 (
7frflK cuff) The film wrapping angle is radian.

& 3 Move and rub at a speed of 11/1lle. Entry pressure mark T, (Detected by entry pressure mark detector S)
Calculate the dynamic friction coefficient μk using the following formula from the exit density 1in T, j (detected by the output density wear detector 1) when adjusting the tick contact 2 to be 3.l. Let Jk be the coefficient of kinetic friction when running at 9o.

Stomach T.

(4riaw8/N The magnetic footing tape is measured using the following method.

S@% white level signal K10 using a commercially available home VTR
The signal on which the 0% RPM level signal is superimposed is recorded, and the reproduced signal is measured using a noise meter 925C. In addition, the definition of Ku18/H is as follows (according to the definition of Sibaku).

However, l5(p-p)-Q, yxnV[p-p)′gN
(rms)=AMυ is exothermic value voltage (V) Also, the magnetic powder coating is prepared by the following method.

Apply the magnetic powder paint shown below using a gravure rule, and smear the magnetic paint layer with a doctor knife.
A magnetic layer of approximately SJ type is formed. Magnetism 1 is used to magnetically orient the still-dry surface using a conventional method, and then the material is opened and dried. Further, it is calendered to create m cloth*1iit-uniform-KL 1/I (7+I?-pu).

Composition of magnetic paint r-F@, 0. Powder 106 weight - Heiker 143 Snow J (manufactured by Nippon Zeon, butadiene ac V renitrile copolymer) 11 #Lecithin 1 #Carbon
8 #MEK 11) 0 #MIBK
100 # Additive (lubricant, silicone resin) ass # The present invention will be explained in more detail with reference to Examples below.

Examples 1 to 5 Comparative Examples 1 to 4 Intrinsic viscosity (L6!! #/j (measured at 3S°C using Ortsk Gyp phenol as a solvent) containing a2m weight percent of Kaon with an average particle size of 6μ After drying the polyethylene terephthalate (basket) at 160℃,
The product was melt-extruded at 0°C and rapidly cooled on a casting drum maintained at 1.1@'cK to obtain an unextended film of 160 pm.

Subsequently, as shown in FIG. 3, the unstretched 7" film was preheated with four heating tubes 11.3 and 34, and then the film was heated with an infrared heater s8 while heating 34.
One step of stretching was carried out in the longitudinal direction between 1 and 3 seconds. Sara K1
The 1i film was stretched once at 10 I'C by λ× in the transverse force direction and then heat-treated at 210°C. Incidentally, the wave elongation shielding rate at this time was 55 blades/min.

Here, while changing the heating temperature during vertical stretching--the heating temperatures in the coolers 31 to 34 and the conditions of the infrared heater 38, the film temperature immediately before the a-cooler 35 and the stretching ratio were changed to produce IIg.
Elongation 1 A film as shown in Table 1 was obtained.

In Examples 1 to 5 and Comparative Example L44 [, same poly 1-
Even when using a film, the frequency of uneven units having depressions on the film surface can be changed by changing the stretching conditions.

In this case, when the uneven units according to the present invention are formed on the film surface, although the surface becomes flat iJ1, the friction coefficient is greatly improved and the electromagnetic conversion characteristics are improved in proportion to the flatness of the surface. Chroma S/M, which is a typical value, improves.

In addition, in Comparative Example 3, it was observed that under conditions where the stretching temperature was very high, the frequency of concavo-convex units with relatively large indentation lengths increased. An increase in RI-78/M and an increase in dropouts were observed, which is not desirable.

Examples @ ~ 8 and Comparative Examples 5 ~ 6 Same conditions as Example 1, except for the type of particles and addition, and the film temperature during longitudinal stretching was 120°C.

Stretching was carried out at a length of 10 times, and the results shown in Table 1-2 were obtained.

As can be seen from Table 2, even if the type of grain is different, the steeliness of the unevenness unit on the film surface and the five combined evaluations are as described in Examples 11 to S and Comparative Examples 1 to 4. obtained similar results.

Also, the size of the seeds present in the fill people.

Since the frequency of occurrence of uneven units on the film surface differs depending on the number, as in Comparative Example-5, the average particle size is 9LO2filM.
When the average particle size is small and comparative example -
If it is as large as am, then ! ! Convex units occur less frequently. As in Examples 1 to 8, the average particle size is a3.
It can be seen that a large number of uneven units occur when the voice layer is ~1.0.

The sample Ht used was a sulfuric acid powder with an average particle size Q of 257 g + 11 and a warm powder of calcium carbonate with an average particle size (L 8 J weight). It's a tape.

Examples 9-10. Comparative Examples 7-8 Polyethylene terephthalate was polymerized by a conventional method using calcium acetate and lithium acetate as transesterification catalysts, antimony formic oxide as a heavy metal catalyst, and trimethyl phosphate as a stabilizer. At this time, by changing the amount of catalyst added, the particle size and amount of internally precipitated particles were determined as shown in Table 3. The polyethylene terephthalate film was formed and evaluated under the same conditions as in Example 6-a, and the results shown in Table 3 were obtained. In the case of particles, similar results to Examples 1 to 8 and Comparative Examples x to 6 were obtained.

[Brief explanation of drawings]

FIG. 1 shows the state of voids formed around particles when stretched by the conventional method. FIG. 1-1 is a plan view and FIG. 1-2 is a cross-sectional view. FIG. 2 shows a polynisdel film of the present invention in which a protrusion containing one particle and a depression are formed around the protrusion. FIG. 2-1 is a plan view, and FIG. 2-2 is a cross-sectional view. FIG. 1 is a schematic diagram of a stretching machine used in an example of the present invention. FIG. 4 is a schematic diagram of a tape pace inspection machine that determines the dynamic friction coefficient mkt# of a fill person's rough image. FIG. 5 is a microscopic photograph showing the surface of a polynisder film produced by conventional technique IIK, and FIG. 1 is a microscopic photograph of the surface of a polyester film according to the present invention. (All magnifications are 900x). 5 (¥16 Procedural amendment dated March 23, 1980, Commissioner of the Japan Patent Office 1, Indication of the case, Patent Application No. 1983-151946 2, Name of the invention, polyester film 3. Person making the amendment. Relationship to the case. Patent applicant. 1-11 Minamihonmachi, Higashi-ku, Osaka (300) Teijin Ltd. Representative Tomoo Tokusue (1) Specification, page 9, line 7, ``D≧'' changed to ``30≦DS, 50σ7'' (2) Same, page 1, page 0, line 11, ``13.2 times or less'' is corrected to ('34 times or less''). (3) Same, page 1, line 1'7*@17 Eye, "average particle size 0.
8 (4) Correct "130" to "137" in the "Film temperature during 1 longitudinal stretching" column of Comparative Example 3 in the 19th Negative Table-1. (5) Ibid., page 22, line 2, ``Hatsusho 1'' is corrected to ``frequency of occurrence.''that's all

Claims (1)

[Scope of Claim] A polyester film in which a large number of uneven units consisting of WK protrusions on the film surface and depressions with wrinkle protrusions as cores are formed, and the protrusions are formed by inert additives or (and ) This is caused by catalyst residue, and the depression is elliptical with a major axis along the film stretching direction, and the major axis of the isthmus is 2 sm (ξkujin) to S
There is a range of Oμ electric current NK, and there is a leap between the long axis DC voice) and the frequency of occurrence N (number/-) of the uneven unit. 2≦D (When 8, zoo≦N<3500. When 2≦D<10, 1sO≦N (2000°10≦D
When <sO, 50≦N<soo. A polyester film characterized in that the following relationship is satisfied: 30iD (when 50 ≦N≦5).