JPS62164538A - Biaxial-oriented laminated polyester film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a biaxially stretched laminated polyester film for magnetic recording, and more specifically, to a biaxially stretched laminated polyester film for magnetic recording, which has excellent electromagnetic conversion characteristics and excellent running durability and abrasion resistance during repeated use. The present invention relates to a biaxially stretched laminated polyester film that provides a magnetic recording medium.

[Prior art]

Magnetic recording media based on polyester films, such as video tapes, audio tapes, computer tapes, and footsbee discs, are known and widely used.

In recent years, demands for higher density recording and higher quality have been increasing in these application fields, and with this, the polyester film that serves as the base has a flat surface and excellent slipperiness.
And durable running performance.

The ix of having excellent abrasion resistance is becoming stronger and stronger.

Conventionally, methods for improving slipperiness have been proposed, such as adding inorganic particles such as silicon oxide or calcium carbonate to polyester, or precipitating fine particles containing calcium, lithium, or phosphorus in the polymerization system during polyester synthesis. ing. In either method, when polyester is formed into a film, projections are formed on the surface of the film due to fine particles, thereby improving the slipperiness of the film.

However, in the method of improving the slipperiness of the film using protrusions made of fine particles as described above, the slipperiness usually improves as the film surface becomes rougher; The surface tends to become rough and the electromagnetic conversion characteristics tend to deteriorate.

As a way to solve these contradictory problems of flatness and slipperiness, a method has been proposed that uses composite particles that are a combination of large particles and small particles. Since both sides of the film have the same surface properties, there is a limit and the level is not satisfactory.

Therefore, several different surface films have been proposed in which one exposed surface has excellent slipperiness and the other exposed surface is flat.Laminated films are also used as a means for this purpose. It is being

However, the conventional method using this means also has the following problems. That is, 0) If the surface is made rough in order to make it slippery, the other surface will also be affected and the flatness will be impaired. This tendency becomes particularly noticeable as the film thickness becomes thinner. ■Even if the film surface on which magnetic paint is applied to a film with different surfaces, which are flat and easy to slide, is flat, if the opposite side is too rough, the rough surface of the film will have unevenness on the surface of the applied magnetic layer. As a result of off-print transfer, unevenness occurs on the surface of the magnetic layer, resulting in loss of flatness and insufficient electromagnetic conversion characteristics. ■Generally, when trying to provide excellent slipperiness, the protrusions on the film surface become high, and as a result, the high protrusions are scraped off during the cleaning process with nonwoven fabric in the magnetic recording tape manufacturing process or the calendering process, which causes drub-out. cause ■
Since the distribution of additive particles as a means for forming protrusions on the film surface is hardly controlled in the prior art, it is difficult to adjust the protrusions on the film surface as designed.

There are other problems.

The inventors of the present invention solved the above-mentioned problems and succeeded in developing a laminated film that has flatness, slipperiness, and abrasion resistance that can be applied to high-quality magnetic recording applications.

[Purpose of the invention]

An object of the present invention is to provide a base film that has high density recording, high quality, and can withstand repeated use as a magnetic recording medium.Furthermore, there are no large protrusions on the surface of the film, which causes noise such as dropouts. It has a flat surface (Side B) that does not easily deteriorate electromagnetic conversion characteristics, a low coefficient of friction during repeated running, and abrasion of the film due to the processing of the magnetic recording medium and contact with parts of the magnetic recording and reproducing device. To provide a biaxially oriented laminated polyester film that has very little (K), has good durability in continuous use, and has an easily slippery surface (side A) with few large protrusions that cause transfer to magnetic layer images. be.

[Structure and effects of the invention]

According to the present invention, an object of the present invention is to provide a biaxially oriented laminated film comprising a film-forming aromatic polyester containing an aromatic dicarbonate as a main acid component and an aliphatic glycol as a main glycol component, the film comprising: One exposed surface (Side A) has a surface roughness RaA of 0.02.
5 μm or less and 0.010 μm or more, and the number of protrusions is 20/
Number of protrusions found in an area larger than mm3 (y: ke/mm3)
The distribution plane representing the relationship between the height of the protrusion (x: μm), +
7. j line has a protrusion distribution that does not intersect with the straight line expressed by formula (1) % formula % (1) in the range lOgtaY > 1.3, and the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by formula (2) Provides a smooth surface that is within the range of formula % (2) and substantially free of protrusion heights (x) of 0.87 μm or more.

The other exposed surface (surface B) has a surface roughness RaB of 0.
0.012 pyl or less, 0.004 pm or more, and the number of protrusions is 2.
Number of protrusions found in an area of 0 pcs/m or more (y: pcs/m
m3) and the height of the protrusion (x: μm), the curve of the portion larger than the maximum value of the protrusion distribution curve intersects the formula (3)% formula (3), and further the formula ( 4) IQg! ++Y≧-44, 1x+4.33 -- (
4), and the protrusion height X) is 0.13 μm
The above gives a flat surface substantially free of Ic
The surface roughness RaA of the A side (smooth surface) and the surface roughness RaB of the B side (flat surface) satisfy the formula (5), and the density ρ and the refractive index n in the thickness direction of the laminated film , L is the formula/6)
, (7) 1.352≦n −-”≦1,366−
・--(6) 1.385≦ρ≦1.405
...It is achieved by a biaxially stretched FF layer polyester film for magnetic recording which satisfies (7) as a percentage image.

The biaxially stretched laminated polyester film of the present invention is a laminated film comprising a layer providing a smooth surface and a layer providing a flat surface.

The layer providing this easy-slip surface (Side A) has a surface roughness RaA of 0.025 μm or more o, o i
0 μm or less, substantially does not include protrusions with a protrusion height (x) of 0.87 μm or more, and the number of protrusions is 20/mm3
The distribution curve representing the relationship between the number of protrusions (y: ke/mm3) and the height of protrusions (x: μm) obtained in the above area is a straight line expressed by the following formula (1). logl, 7) 1.3, and the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by the following formula (2) % formula % (
It has properties in the range of 21. If the surface roughness RaA is larger than 0.025 μm, the surface of the base film becomes too rough and the flatness of the magnetic surface is impaired due to show-through transfer, which deteriorates the electromagnetic conversion characteristics, which is not preferable.

Moreover, when RaA is smaller than 0.010 μm, running properties deteriorate, which is not preferable. The preferred surface roughness RaA is 0
．． 02Q, un or less is 0.0125 μm or more.

Furthermore, the distribution curve representing the relationship between the number of protrusions (y) and the height of protrusions (X) determined in a region where the number of protrusions is 20/mm3 or more is a straight line expressed by the above equation (1) and lQgt.

If it intersects in the range of y>1.3, the flatness of the magnetic surface will be impaired due to show-through transfer, and the electromagnetic conversion characteristics will deteriorate, which is undesirable, and the protrusions will be scraped off during the tape processing process, especially during the calendering process. Further, when the tape is used repeatedly, it is undesirably scraped, which increases the coefficient of friction, and the scraped powder adheres to the tape WiK, increasing dropouts. Furthermore, if the curve in the portion larger than the maximum value of the distribution curve is not within the range of formula (2) above, the film surface will be too flat, and the coefficient of friction (μk) after 200 repetitions will be 0.15 to 0.35. This is not preferable because it becomes difficult to satisfy the range. In the above distribution curve.

The curve on the side exceeding the maximum value is -18X+3.7≦logse7≦-9, 8x+4.4
(However, 10gt.y) 1.3) is preferably satisfied. Furthermore, 0.87μ on the film surface
If there are protrusions larger than the wind, the running properties of the tape will improve, but this is not preferable because it will cause the protrusions to be scraped during the processing process and also cause dropouts.

In the laminated polyester film of the present invention, the flat surface (B
The film surface properties of the layer that provides a surface roughness RaB of 0.012 μm or more, no protrusions with a protrusion height (xJ of 0.13 μm or more, and a protrusion count of 20 protrusions/mm3 or more) Number of protrusions found in the area (y: ke/mm3)
In the distribution curve representing the relationship between the projection height (x: μm), the curve of the portion larger than the maximum value of the projection distribution curve intersects the following formula (3) % formula % (3), and further the following formula (4 ) "gn)'≧-44, I X + 4.33 -
It has characteristics within the range of .--(4). If the surface roughness RaB is larger than 0.012 μm, it is not preferable because the magnetic surface cannot maintain the electromagnetic conversion characteristics necessary for a high-quality magnetic recording tape. The preferable surface roughness RaB is 0.010 μm or less. O
Q: 4 μm or more. In addition, in the distribution curve that expresses the relationship between the number of protrusions (yl) and the height of protrusions (Xl) determined in a region where the number of protrusions is 20/mm3 or more, the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by the above formula (3). ), for example, if the curve in the portion larger than the maximum value of the protrusion distribution curve always satisfies the above formula (2), the film surface is too rough and there are protrusions with a protrusion height of 0.13 μm or more. This is not preferable because the electromagnetic conversion characteristics deteriorate and the characteristics necessary for a high-quality magnetic recording tape cannot be maintained.

Conversely, if the protrusion distribution curve always satisfies K log16y < -18x+ 3.7 in a region where the number of protrusions is 20 or more per pi, the film surface becomes too flat;
The coefficient of friction is large, which makes the film difficult to handle during the production of the base film or during the processing of the magnetic recording material, and is undesirable because it causes problems such as wrinkles.

The two-wheel stretched laminated polyester film of the present invention has the above-mentioned film surface characteristics, and at the same time has a relationship between the surface roughness RaA of the easy-slip surface (side A) and the surface roughness RaB of the flat surface (side B) according to the following formula (5). ) % Formula % aA If the value of RaB is less than 1.3, it is not possible to exhibit properties that satisfy flatness and slipperiness at the same time, and either electromagnetic conversion properties or running properties are sufficient, so it is preferable. The difference in slipperiness between the front and back surfaces is too large,
Wrinkles may occur during winding of the film, creases may occur during processing, and scratches may occur, which is undesirable. These points aB are correct.

The biaxially stretched laminated polyester film of the present invention has the above-mentioned film surface characteristics, and at the same time, the refractive index n2 in the thickness direction of the film and the density ρ are expressed by the following formula (6) +
(7) It has the characteristic of satisfying the formula % (6). (nz,
If the value of o) is lower than 1.352, the running properties are bad, and if it is larger, the abrasion resistance and running properties are good, but 1.36
If it exceeds 6, # the film! Preferably 1.355.
1,362 or less, particularly preferably 1.356
1.360 or less.

Furthermore, if the density ρ exceeds 1.405 (!/cTI'J), the machinability will deteriorate and scratches will occur easily, so it is not preferable. This is undesirable because it increases the ratio and tends to cause wrinkles in the heating process part during the magnetic tape manufacturing process. Density ρ is 1.39011cr1 or more 1.400
g/cd or less is preferable, and 1.3949/cd or more1
,398,! The special button is preferably less than i'/m.

In the present invention, the aromatic polyester is a polyester containing aromatic dicarboxylic acid as the main acid component and aliphatic glyfur as the main glycol component. Such polyethylene film is substantially linear and has film-forming properties, particularly film-forming properties by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid, and the like. I can do it. Examples of aliphatic glycols include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, or alicyclic glycols such as cyclohexane dimetatool. Diols etc. can be mentioned.

In the present invention, polyesters containing, for example, fullkylene terephthalate and/or alkylene naphthalate as main constituents are preferably used.

Among such polyesters, for example, not only polyethylene terephthalate and polyethylene naphthalate, but also terephthalic acid and/or naphthalene dicarboxylic acid account for 80 moles or more of the total dicarboxylic acid component, and ethylene glycol accounts for 80 mole or more of the total glycol component. Copolymers are particularly preferred. In this case, the dicarboxylic acid of 20 molyth or less in the total fermentation can be the above-mentioned aromatic dicarboxylic acids, and also, for example, aliphatic dicarboxylic acids such as 7-divic acid and cepacic acid; alicyclic acids such as cyclohexane-1,4-dicarboxylic acid. dicarboxylic acids and the like.

Also, up to 20 moles of the total glycol component can be the aforementioned glycols other than ethylene glycol, or for example hydroquinone.

Aromatic diols such as resorcinol, 2,2-bis(4-human p-xyphenyl)propane; aliphatic diols containing aromatics such as 1,4-dihydroxymethylbenzene; polyethylene glycol, polybutylene glycol, polytetra It can also be polyalkylene glycol (polyoxyfulkylene glycol) such as methylene glycol.

In addition, the aromatic polyester used in the present invention may contain a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-human p-xicaproic acid, or a dicarboxylic acid. It also includes those containing 20 moles or less based on the total amount of the component and the oxycarboxylic acid component. Further, the aromatic polyester in the present invention includes a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as trimellitic acid, in an amount within a substantially linear range, for example, an amount of 2 mole or less based on the total acid component. Copolymerized pentaerythritol is also included.

The above-mentioned aromatic polyester is known per se, and can be produced by a method known per se.

The aromatic polyester preferably has an intrinsic viscosity of about 0.4 to about 0.9, measured as a solution in O-pp sphenol at 35°C.

The polyester film I-, which forms one surface (A side: easy-slip surface) exposed in the present invention, preferably contains inert particles consisting of large particles and small particles. [Particles that can be used as large particles constituting the inert particles]

Compositionally, it consists of calcium carbonate, and it may be either light calcium carbonate or calcium bicarbonate. These large calcium carbonate particles are characterized by their particle size distribution, and when the particle size distribution of calcium carbonate particles is plotted on logarithmic probability paper, it is expressed as the ratio to the particle diameter when the cumulative weight of calcium carbonate is 75%. The particle size distribution ratio expressed by the following formula (8) is in the range of 1.5 to 2.3, preferably in the range of 1.5 to 2.2, more preferably 1.
．． It has a particle size distribution controlled to be in the range of 5 to 2.1. A controlled particle size distribution of the calcium carbonate particles used in the present invention is a particularly preferable condition for achieving the above-mentioned object of the present invention, and the lower the value of this particle size distribution ratio ■, the lower the particle size distribution of the calcium carbonate particles. It shows that it is sharp. Calcium carbonate particles having such a specific range of particle size distribution ratios are only commercially available.

It cannot be obtained by simply using a product, but can only be obtained by pulverizing or crushing in a solvent such as ethylene glycol, separating coarse particles by sedimentation, and then performing pretreatment such as filtration. It is.

Further, the small particles constituting the inert particles are compositionally composed of titanium dioxide, and crystalline form is anatase titanium dioxide. More preferably, it is a special titanium dioxide containing specific amounts of phosphorus element and potassium element, as described below.

The anatase titanium dioxide particles have a particle size distribution that is % dependent, and the value of the particle size distribution ratio ω expressed by the above formula (8) is in the range of 1.2 to 2.3, preferably 1.4 to 2. 2
and more preferably a controlled particle size distribution in the range of 1.4 to 2.1.

A controlled particle size distribution of the titanium dioxide particles used in the present invention is a particularly preferable condition for achieving the above-mentioned object of the present invention, and the smaller the value of this particle size distribution ratio ω, the smaller the particle size distribution of the titanium dioxide particles. is sharp. However, it is empirically very difficult and difficult to achieve a particle size distribution with a particle size distribution ratio value of less than 1.2. Titanium dioxide particles having such a particle size distribution ratio in a specific range cannot be obtained simply by using commercially available products, but are pulverized or crushed in a solvent such as ethylene glycol, and coarse particles are separated by sedimentation. However, it is a specific particle with a controlled particle size distribution that can only be obtained by performing a pretreatment such as filtration in combination. When the value of the particle size distribution ratio (■) is 2.3, the number of coarse particles in the inert particles increases, and the protrusions on the film surface become large. The electromagnetic conversion characteristics of the product also tend to deteriorate rapidly.

In addition, even if the particle size distribution ratio of either calcium carbonate particles or titanium particles exceeds 2.3, the number of coarse particles in the inert particles may increase even though they are small in terms of weight. The number of protrusions with three or more rings of interference fringes caused by Na rays on the film surface increases.
This results in more than 20 pieces per 100i.

The calcium carbonate particles used in the present invention have an average particle size in the range of 0.3 to 0.9 μm, preferably 0.35 to 0.9 μm.
It is characterized by being in the range of 8 pm, more preferably in the range of 0.4 to 0.7 pm. The content (WB) of charcoal calcium particles in the film is 0.06-0.5% by weight
The content is preferably in the range of 0.1 to 0.4% by weight, more preferably in the range of 0.15 to 10.3% by weight. When the average particle size of the calcium carbonate particles is larger than 0.9 μm and the content (WB) of calcium carbonate in the film is larger than 0.50% by weight, K has good slipperiness of the base film.

The frequency of unevenness on the film surface increases, and noise during magnetic recording tends to increase. When the content of calcium carbonate particles in the film is 0.1 to 0.5% by weight and 0.06%
Weight% or more 0.1%* (weight) (especially 0.06-0.
When compared with the case of 09x57%), the former has a tendency to increase the roughness of the film surface (RaAO value),
The latter shows a tendency that the running friction coefficient [μk] of the film running surface does not change even after repeated use. Therefore,
When the content of calcium carbonate is less than 0.1%, the durability and sliding properties of the film become unstable due to running (use).

The titanium dioxide particles among the inert particles used in the present invention are
The average particle size is in the range of 0.10-0.50 μm, preferably in the range of 0.15-0.50 pm, more preferably in the range of 0.
．． It is preferably in the range of 20 to 0.40 μm. The content (WB) of the titanium dioxide particles used in the present invention in the film is in the range of 0.10 to 0.601, preferably 0.601.
In the range of 12 to 0.50% by weight, more preferably 0.15%
It is characterized by being in the range of ~0.40% by weight.

When the average particle size of titanium dioxide particles is smaller than 0.1 Oμm and the content (Ws) in the film is less than o, io weight%, the surface of the base film has low lubricity and cannot be rolled up during film forming. This problem occurs frequently.

In the present invention, the ratio of the average particle size of the carbonate particles to the average particle size of the titanium dioxide particles is in the range of 1.5 to 1%, furthermore, in the range of 1.5 to 8%, the ratio is 1.6 to 5%. It is preferable that it is in the range of . When the ratio of the average particle size of calcium carbonate particles to the average particle size of titanium dioxide particles is larger than 10, the unevenness of the film surface becomes large and the reproducibility of magnetic recording is poor. Furthermore, if the ratio to the average particle diameter of calcium carbonate particles is smaller than 1.5, the winding properties during base film formation are poor, and there is often a difference in the winding hardness in the width direction of the base film. There is a tendency to

The titanium dioxide particles used in the present invention have a composition in which p, o, converted to 0.25% by weight or more, preferably in the range from 0.25% to 1.0% by weight, more preferably f), Contains phosphorus element ranging from 28% by weight to LO% by weight, and at least 0.11% by weight in O terms, preferably from 0.1% by weight to 0.30% by weight, more preferably 0.01% by weight % to 0.28% by weight of potassium element. In the composition of titanium dioxide particles, if the content of phosphorus element calculated as Pgos is less than 0.25 i,
If the converted potassium element content is less than 0.131%, the color tone of the titanium dioxide particles tends to be poor. The titanium dioxide particles preferably used in the present invention are characterized by low abrasion properties because they contain phosphorus and potassium elements in the above ranges. There is less damage such as, etc., and the effect of low abrasion appears in terms of workability, equipment maintenance, cost, etc. Furthermore, there is also the effect that scratches and scratches are less likely to occur on the film surface.

The other surface exposed in the present invention (Side B: flat surface)
It is preferable that the polyester film layer forming the layer contains inert particles to an extent that does not impair flatness. The inert particles are preferably small particles, particularly titanium dioxide particles, contained in the polyester layer/flum layer forming the easy-slip surface (A side). The description of the titanium dioxide particles can basically be applied as described above. These titanium dioxide particles have an average particle size of 0.
in the range of 10 to 0.50 μm, preferably 0.12 to 0
．． 50 μm range, more preferably 0.15 to 0.40
It is characterized by being in the μm range. Further, the content (Ws) of titanium dioxide particles in the film is 0.0
in the range of 1-1.0% by weight, preferably 0.02-0.6
It is characterized by being in the range of 0% by weight, more preferably in the range of 0.05 to 0.40% by weight. When the average particle size of titanium dioxide particles is smaller than 0.10 μm and the content (Ws) of titanium dioxide particles in the film is less than 0.01% by weight, the surface of the base film has poor lubricity, and when forming the film, , troubles such as not being able to wind up occur frequently.

The thickness structure of the laminated film in the present invention is not particularly limited, but in order to maximize the effect of the added inert particles, the layer thickness of the easy slip layer (A side) after biaxial stretching is 2 μm. It is preferably at least 3 μm, more preferably at least 4 μm. If the thickness of the slippery layer is too thin, protrusions, especially protrusions caused by small particles, will be difficult to form, resulting in poor running performance and scratch resistance.In addition, the layer that provides a flat surface (Side B) will maintain flatness. Therefore, the layer thickness of K after biaxial stretching is preferably 3 μm or more, more preferably 4 pm or more, particularly preferably 5 μm or more.

If the thickness of the flat layer is too thin, flatness will be impaired due to the influence of inert particles in the slippery layer, which is not preferable.

Although the laminated film of the present invention has a multilayer structure of two or more layers, a two-layer structure is particularly preferable. In the case of a laminated film with two or more layers, the outermost layer is the above-mentioned surface A,
If it is a polyester film layer of H, the intermediate layer may be a single layer of any polymer.

The laminated film of the present invention can be manufactured using conventional laminated film manufacturing methods. For example, the polyester layer forming surface A and the polyester layer forming surface B can be laminated in a molten state or in a cooled and assimilated state. More specifically, for example, coextrusion
It can be manufactured using methods such as extrusion coating. The film laminated by the above method is sequentially biaxially stretched or simultaneously biaxially stretched by a method that is consistent with conventional methods for producing biaxially stretched films, and is further heat treated. At this time, the surface characteristics of the film vary depending on the shape, particle size, amount, etc. of the solid fine particles, and also depending on the stretching conditions, so they are appropriately selected from conventional stretching conditions. For example, the stretching temperature is such that the first stage stretching temperature (e.g. longitudinal stretching temperature: 'rt) is (Tg-t
O) to (Tg+45) °C (however, the glass transition temperature of 1 g polyester), the second stage stretching temperature (for example, transverse stretching temperature: T) is from (T, +15) to (T, +
40) It is preferable to select from the range of ℃. Further, the stretching ratio is preferably selected from a range in which the uniaxial stretching ratio is 2.5 or more, particularly 3 times or more, and the area magnification is 8 times or more, especially 10 times or more. In addition, the heat setting temperature is 180 to 250
℃, preferably from the range of 200 to 230℃. In addition, in order to satisfy the above-mentioned relationship between nz and density ρ, K
It is desirable that the longitudinal stretching temperature is (Tg+25)° C. or higher and the longitudinal stretching speed is 1500 inches/second or less, preferably 900%/second or less.

The biaxially stretched laminated polyester film according to the present invention has excellent properties for use in magnetic recording media, particularly for high-grade magnetic tapes.

〔Example〕

The present invention will be further explained below with reference to Examples.

Note that various physical property values and characteristics in the present invention were measured and defined as follows.

(1) Average particle size of inert solid particles Shimadzu CP-50If Centrifugal Particle Size Analyzer (Centrifugal
Particle 5ize Analyzer)
Measured using From the cumulative curve of particles of each particle size and their abundance calculated based on the obtained centrifugal sedimentation curve, the particle size corresponding to 50 mass percent was read, and this value was taken as the above average particle size. (“
"Particle size measurement technology" published by Nikkan Kogyo Shimbun, 1975, p. 9, 2
42-247) O (2) Particle size distribution ratio of inert solid particles■ Based on the centrifugal sedimentation curve obtained in the measurement of the average particle size of inert inorganic particles, the relationship between particles of each particle size and their abundance is calculated. Calculate and draw the cumulative curve, read the particle size corresponding to the cumulative weight of the particles of 25 mass percent and the particle size corresponding to the cumulative weight of the particles of 75 mass percent), divide the former value by the latter value. Calculate the particle size distribution ratio of each inert solid particle.

(3) Film surface roughness Ra) Measured according to JIS B Offal. Stylus type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd.
), a film surface roughness curve was plotted on the chart under the conditions of a needle radius of 2μ and a load of 0.07 &. A part of measurement length L is extracted from the film surface roughness curve in the direction of its center line, and the center line of this extracted part is set as the X axis,
With the vertical magnification direction as the Y axis, the roughness curve is Y=fl:xl
When expressed as , the value given by the following formula (Ra: μm)
is defined as the film surface roughness.

In the present invention, eight measurements were taken with a reference length of 0.25 m, and Ra was expressed as the average value of the five measurements, excluding three from the largest value.

(4) Number of surface projections Aluminum is vacuum-deposited uniformly on the surface of the film to a thickness of 400 to 500X or less, and the opposite non-deposited surface (
Film surface) VC:I Rodion was applied, pasted, and dried. TII monochromatic light multiple interference reflection microscope (e.g. Ca
An arbitrary xOOd on the aluminum vapor-deposited surface was observed at a magnification of 100 times using a camera (manufactured by JENA Co., Ltd.).

The number of protrusions H1 (
) were counted.

(5) Coefficient of friction (μk) of film It was measured as follows using the apparatus shown in Figure 2. In Figure 2, l is the unwinding reel.

2 is tension controller + 3. s, 6. s, 9 and 11 are free rollers, 4 is a tension detector (inlet), 7 is a fixed rod made of stainless steel SUS 304 (outer diameter 5w and φ), 10 is a tension detector (outlet), 12
is a guide ruler.

Reference numeral 13 indicates a take-up reel.

In an environment with a temperature of 20° C. and a humidity of 60%, a film cut to a width of 1/2 inch is brought into contact with a fixed rod (152°) of 7 and moved (frictioned) at a speed of 200 α per minute. Entrance tension T.

When the tension controller 2 is adjusted so that the film is 35g, the exit tension (Tlg) is 90g.
After traveling m, the exit tension is detected by the detector, and the running friction coefficient μk is calculated using the following formula.

(6) Scrapability The scratchability of the running surface of the base film was evaluated using a 5-stage mini super calendar.

The calender is a 5-stage calender with knife rolls and steel rolls, the processing temperature is 80℃, and the linear pressure applied to the film is 200kl? /mouth.

The film was run at a speed of 507+1/min.

After running the running film for a total length of 2000 m, the abrasion resistance of the base film was evaluated based on the dirt adhering to the top roller of the calendar.

<5-level evaluation> ◎ No stains on the nylon roll ○ Almost no stains on the nylon rule △ Nylon roll gets dirty × Nylon rule gets very dirty ×× Nine-pole gets very dirty (7) Electromagnetic conversion characteristics of magnetic coating film (Chroma S/N) On the film, 1100 parts by weight of Co-containing iron oxide powder with the following composition S-LEC A (vinyl chloride-vinyl acetate copolymer manufactured by Tanesui Chemical Co., Ltd.) 10 x
Niraporan 2304 (Polyurethane elastomer made by Nippon Polyurethane) 1O〃Cornate L (Polyr Socia Fukito made by Nippon Polyurethane) 5 〃
Shi Chin
l 〃Methyl ethyl ketone
744iflII (methyl in butyl ketone
75 Toru en
75 〃Additives (
Lubricant, silicone resin) Magnetic powder paint with O, 15# is applied using a gravure rule, the magnetic paint layer is smoothed with a doctor knife, magnetically oriented using a conventional method while the magnetic paint is still dry, and then placed in an oven. and dry and cure. Further, the coated surface was made uniform by calendering, and a 1/2 inch wide magnetic coating tape was prepared by slitting to form a magnetic layer of approximately 5 μm.

Electromagnetic conversion characteristics of this magnetic coating tape (Ripma S
/N) is measured by the following method.

A 50% white level signal (10
The 0% white level signal is peak; two; the voltage at the peak is 0.
714 volts), a 100% chroma level signal is recorded, and the reproduced signal is measured using a Shibasoku Noise Meter: Type 925R.

The definition of chroma S/N is as follows according to Shibak's definition.

Here, gs(p-p) is the peak-to-peak voltage difference (P-=p'') of the reproduction signal of the white level signal.

ES (p-p) = 0.714 V (p-p) Also, EN (rms) is the square root value of the peak voltage of the reproduced signal of the chroma level signal.

EN (rms) = AM/Is effective value voltage (V) (8)
Dropout (7) Tape coated with magnetic powder coating (l)
/2 inch width) with a commercially available dropout counter (for example, Shibatsu VHOIBZ type) to 5μ5ecXl.
The dropout of odB was counted and the number of counts per minute was calculated.

(9) Slit the scratch judgment base film into 1/2 inch width and
) At the same time as the measurement of the friction coefficient of The following five grades were given based on the thickness, depth, and number of the pieces.

<5-level evaluation> ◎ No scratches observed on the 1/2 inch wide base film 0 Almost no scratches observed on the 1/2 inch wide base film △ Scratches observed on the 1/2 inch wide base film. (Several) Several thick scratches are observed on the XI/2 inch wide base film xx Many thick and deep scratches are observed all over the 172 inch wide base film Ql Protrusion distribution measurement method Three-dimensional roughness manufactured by Koita Research Institute Using a scale (SE-30K),
The protrusion distribution was measured under the following conditions: needle diameter 2 μm R1 needle force 3o, measurement length 1 m sampling pitch 2 μm 1 cutoff 0.25 m, vertical magnification 20,000 times, horizontal magnification 200 times, number of scans 150, For protrusion height (x-axis), the protrusion height level 2) at the point where the area ratio from the reference level is 70% is set as 0 level, the difference from that height is defined as protrusion height, and the corresponding number of protrusions is plotted on the y-axis. I punched it.

[Example 1] [Slurry v! A. Preparation of ethylene glycol slurry containing lucium carbonate particles 301 L parts of commercially available calcium carbonate particles were added to 70 parts by weight of ethylene glycol with stirring, and stirred at high speed with a homogenizer to form a slurry with a concentration of 30% by weight (1 )It was created. The average particle size of calcium carbonate constituting this slurry was 1.03 μm, and the value of the particle size distribution ratio was 2.6.

Next, the 30% by weight ethylene glycol slurry of calcium carbonate was treated with a sand grinder,
An ethylene glycol slurry (2) of calcium carbonate was prepared. The average particle size of this slurry particle is 0.56 μm
The particle size distribution ratio value was 2.9.

Next, the slurry (
2) to classify coarse particles of calcium carbonate, followed by filtration with a filter (commercially available nominal opening 3 μm) to create an ethylene glycol slurry (3). The average particle diameter of the slurry particles was 0.52 μm, and the particle size distribution ratio (■) was 1.9.

B. Preparation of Ethylene Glycol Slurry of Anataseya Titanium Dioxide Particles Commercially available 7Natazeya titanium dioxide particles and ethylene glycol were mixed with high speed stirring using a homogenizer mixer to prepare a slurry (1) with a concentration of 30% by weight.

Next, the slurry (1) was passed through a sand grinder and processed to produce slurries I)-(2).

Furthermore, the slurry (3) was prepared by processing with a high speed rotating decanter classifier and filtering with a filter.

The particle size distribution of each slurry was measured. The results are as follows.

One type of slurry Average particle size Particle size distribution ratio
1) 0.64 μff12.7(2)
0.33 μm2.8(3) 0.3
1 pm 1.9 [Production method of polymer for film] Add 100 parts by weight of dimethyl terephthalate and 70 parts by weight of ethylene glycol to 0% of dimethyl terephthalate.
．． 0.015 molty manganese acetate and 0.010 molty sodium acetate were added, and transesterification was carried out at 150 to 250°C while distilling methanol. At that time, an ethylene glycol slurry (fa degree lO%) of calcium carbonate particles prepared in advance was added.

After the transesterification reaction was completed, 0.015 mol of trimethyl phosphate, which had been heated under reflux in the presence of ethylene glyfur, was added to dimethyl terephthalate. Furthermore, 0.03% of 7thimony trioxide to dimethyl terephthalate
A polycondensation reaction was carried out under a high vacuum of 1 Torr or less. After the polycondensation reaction was completed, the polymer was cooled with water and cut to obtain polyethylene terephthalate pellets containing calcium carbonate particles dispersed therein (hereinafter referred to as polyester 1).

Transesterification and polycondensation reactions were carried out in the same manner as above, except that instead of the ethylene glycol slurry of calcium carbonate particles, the ethylene glycol slurry of titanium dioxide particles prepared in 1.14 was added. A polyethylene terephthalate pellet in which particles were dispersed was obtained (hereinafter referred to as polyester ■).

Next, a transesterification reaction and a polycondensation reaction were carried out in the method for producing polyester I without adding any inert particles to obtain a polyethylene terephthalate pellet without the addition of external inert particles [hereinafter referred to as polyester (1)].

[Membrane made]

Polyester I, Polyester■, and Polyester■
were mixed so that the content of calcium carbonate particles was 0.35% by weight and the content of titanium dioxide particles was 0.15% by weight to obtain blend A, and polyester (III) and polyester (III) were mixed together so that the content of calcium carbonate particles was 0.35% and the content of titanium dioxide particles was 0.15% by weight. Content is 0.15
Blend B was obtained by mixing in such a manner as to achieve the same weight percentage. Then, the blend A is supplied to separate extruders of the film forming machine so that it becomes a layer forming the A side, and the blend B becomes a layer forming the B side, and the A side is formed. When the thickness of the polyester layer accounted for 60% of the thickness of the laminated film, it was extruded from a die to obtain an unstretched film of 200 μm.

This unstretched film was sequentially biaxially stretched at a longitudinal stretching temperature of 115°C, a longitudinal stretching ratio of 3.1 times, a transverse stretching temperature of 120°C, and a transverse stretching ratio of 3.2 times, and was further heat-treated at 225°C.

The properties of the laminated polyester film thus obtained are shown in Table 1, and the distribution of unevenness on the film surface is shown as curve A in Figure 1.

Note that the symbol A means the A side, and the symbol B means the B side. The density ρ of the laminated film was 1.3980 El/cd, and the "10" value determined from the refractive index n2 in the film thickness direction and the density ρ was 1.3590.

This film had different surfaces on the front and back sides, had good abrasion resistance on the easily slippery side (side A), had few scratches, and had good electromagnetic conversion characteristics and scratch resistance after coating the magnetic layer.

Example 2 and Comparative Examples 1 to 2 In Example 1, calcium carbonate particles to be added and 7
A biaxially stretched laminated film was produced in the same manner as in Example 1 except that the Nataize type titanium dioxide particles were changed. The results are shown in Table 11 and Figure 1. In addition, in Figure 1,
Curve 2 shows that of Example 2, curve C shows that of Comparative Example 1, and curve 2 shows that of Comparative Example 2. Furthermore, the symbol A means the characteristics of the A side, and the symbol B means the characteristics of the B side.

The additive particles on the smooth surface in Comparative Example 1 had an average particle size of 1.1μ.
In the case of calcium carbonate of No. m, the runnability was good, but there were high protrusions, the electromagnetic conversion characteristics were poor, and furthermore, the calendering was poor, and it could not be used. Also, comparative example 2
If the easy-slip surface (Side A) was too flat, the coefficient of friction (μk) after 200 repetitions became high, the running performance deteriorated, and the product could not be used.

Table-1

[Brief explanation of drawings]

Figure 1 shows the height of protrusions on the film surface (μm) and the number of protrusions (
It is a figure showing the relationship of (-). FIG. 2 is a diagram showing the film 7p of the device used for measuring the coefficient of friction (μk). Figure-2

Claims (1)

[Scope of Claims] 1. A biaxially stretched laminated film comprising a film-forming aromatic polyester containing aromatic dicarboxylic acid as the main acid component and aliphatic glycol as the main glycol component, comprising: One side (Side A) has a surface roughness RaA of 0.025 μm or less and 0.010 μm or more, and the number of protrusions (y: ke/mm^) determined in the area where the number of protrusions is 2.0 ke/mm^3 or more. 3) and the height of the protrusion (x: μ
The distribution curve representing the relationship with m) is the equation (1) log_1_
0y=-9.8x+4.4...It has a protrusion distribution that does not intersect with the straight line represented by (1) in the range of log_1_0y>1.3, and further has a part larger than the maximum value of the protrusion distribution curve. The curve is equation (2) log_1_0y≧-18x+3.7 (2
) and with a protrusion height (x) of 0.87 μm or more provides a smooth surface that is substantially free of surface roughness, and the other exposed surface (Side B) has a surface roughness RaB of 0.87 μm or more. 0.012 μm or less and 0.004 μm or more, and represents the relationship between the number of protrusions (y: ke/mm^3) and the height of the protrusions (x: μm) determined in an area where the number of protrusions is 20 protrusions/mm^3 or more. In the distribution curve, the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by the formula (3) log_1_0y=-1
8x+3.7...Crosses (3) and further formulas (
4) log_1_0y≧-44.1×+4.33...
・It is within the range of (4) and the protrusion height (x) is 0.13
The surface roughness RaA of surface A (easy surface) and the surface roughness R&B of surface B (flat surface) are expressed by the formula (5) 1.3≦ (RaA)/(AaB)≦5・・・(5
), and the density ρ and the refractive index n_z in the thickness direction of the laminated film satisfy equations (6) and (7) 1.352≦n_z
−(ρ/10)−≦1.366 (6)1.
385≦ρ≦1.405 (7) A biaxially stretched laminated polyester film for magnetic recording, characterized in that it satisfies (7). 2. The film layer forming the A side (slippery surface) contains 0.
1 to 0.5% by weight of calcium carbonate and 0.1 to 0.6% by weight of anatase titanium dioxide are contained, and the calcium carbonate has the following formula (8) [γ] = cumulative weight of particles is 25% Diameter when the cumulative weight of particles is 75%...The value of the particle size distribution ratio [γ] expressed by (8) is in the range of 1.5 to 2.3, and the average The particle size is in the range of 0.3 to 0.9 μm,
Further, the titanium dioxide has a particle size distribution ratio [γ] represented by the above formula (8) in a range of 1.2 to 2.3, and an average particle size in a range of 0.1 to 0.5 μm. The biaxially stretched laminated polyester film according to claim 1, characterized in that the average particle diameter is smaller than that of calcium carbonate. 3. In the film layer forming the B side (flat surface), the value of the particle size distribution ratio [γ] expressed by the above formula (8) is from 1.2 to
2.3 and the average particle size is 0.1 to 0.5 μm
Anatase type titanium dioxide in the range of 0.01 to 1
% by weight of the biaxially stretched laminated polyester film according to claim 1.