JPH09174650A - Manufacture of multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To gauge a thickness of each layer online and make thick mottles small by gauging a thickness pattern of a polyester layer in the cross direction with an optical interference type film thickness gauge and adjusting by using its result. SOLUTION: A thickness pattern of a polyester layer in the cross direction is adjusted by using a result of the thickness pattern of the polyester layer in the cross direction gauged by an optical interference type film thickness gauge. At least one of the utmost outer layers of it is a polyester layer having a thickness of 0.2-100μm. The layer adjacent thereto having a beam permeability of 0-85% at 600nm and a thickness of 2-100μm is a polyolefin layer which is manufactured by co-extrusion. The thickness of the polyester layer can be gauged online by applying beam from the surface side and gauging an interference light of a reflected light on the irradiated face of the utmost outer layer and a reflected light on an interface of the polyester layer/the polyolefin layer. The gauged result is fed back to a thickness adjusting equipment so as to obtain a multilayer film having excellent thick mottles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer film and a method for producing the same, and more particularly to a film for heat-sensitive stencil printing, a film for condensers, a film for thermal transfer printer ribbons by peeling and separating a polyester layer from the multi-layer film. The present invention relates to a multi-layer film, which is useful as a base film for magnetic recording tapes such as video tapes, and can efficiently produce a polyester film having a small thickness unevenness, and a method for producing the same.

[0002]

2. Description of the Related Art A method for obtaining an ultrathin film by peeling and separating a polyester film from a multilayer film obtained by laminating a polyolefin layer and a polyester layer is disclosed in JP-A-58-58.
5226, JP-A-58-136417, JP-A-57-176125 and the like. The total thickness of the multilayer film obtained by these methods can be measured online with a β-ray thickness meter or a γ-ray thickness meter. However, it is impossible to measure the thickness of each layer constituting the multilayer film online with a β-ray thickness meter or a γ-ray thickness meter.

Therefore, under the present circumstances, after winding a multilayer film, the film is sampled, each layer is separated and separated, and the thickness and thickness unevenness are measured off-line, and the thickness adjustment is attempted based on the result. However, this method cannot adjust the thickness unevenness quickly and sufficiently, and the thickness unevenness of the polyester film obtained by peeling and separating from the multilayer film is not sufficient. In addition, when the unevenness of the thickness of the polyester film is insufficient, problems such as wrinkles occur when the polyester layer is peeled off from the polyolefin layer and wound up, resulting in a poor production yield.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to improve the above-mentioned drawbacks and to provide on-line the thickness of each layer of a multilayer film in which at least one of the outermost layers is a polyester layer and the layer adjacent thereto is a polyolefin layer. It is an object of the present invention to provide a multilayer film which enables measurement and can efficiently produce a polyester film having a small thickness unevenness, and a method for producing the same.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
According to the present invention: At least one of the outermost layers is a polyester layer having a thickness of 0.2 to 100 μm, and the layer adjacent to it is 600
The light transmittance in nm is 0 to 85% and 2 to 100
When a multilayer film, which is a polyolefin layer having a thickness of μm, is produced by coextrusion, the width pattern of the polyester layer in the width direction is measured by using an optical interference type film thickness meter. A method for producing a multi-layer film, which comprises adjusting.

[0006] 2. At least one of the outermost layers is 0.2-1
A multilayer film produced by coextrusion, which is a polyester layer having a thickness of 00 μm, and a layer adjacent to the polyester layer having a light transmittance at 600 nm of 0 to 85% and a thickness of 2 to 100 μm. The widthwise thickness pattern of the polyester layer is achieved by the multilayer film adjusted using the result of the widthwise thickness pattern of the polyester layer measured by an optical interference type film thickness meter. Hereinafter, the present invention will be described in detail.

[Measurement of Thickness] In the present invention, the thickness of the outermost polyester layer is measured by irradiating a light beam from the surface side of the polyester layer and using a reflection-type optical interference film thickness meter to measure the reflected light on the irradiation surface of the outermost layer. It can be carried out online by measuring the interference light with the reflected light at the interface between the polyester layer and the polyolefin layer. The method of measuring the thickness using this optical interference film thickness meter is to calculate the thickness by the following formula (I) from the peak wavelength interval of adjacent interference fringes or the valley wavelength interval of adjacent interference fringes.

[0008]

## EQU2 ## t = (λ ₁ × λ ₂ ) / [2 × n × (λ ₁ −λ ₂ )] ... (I)

However, in the formula (I), t is the thickness (nm) of the polyester layer, and λ ¹ and λ ² are the peak wavelength (nm) of adjacent interference fringes or the valley wavelength (n) of adjacent interference fringes.
m) (λ ¹ > λ ² ), where n is the average value of the refractive index of the polyester layer in the longitudinal direction and the transverse direction.

By this method of measuring the thickness of the outermost polyester layer using the reflection type optical interference film thickness meter, when the thickness of each layer of the multilayer film is close to each other, the waveforms of the interference spectra are extremely close to each other. As a result, it becomes extremely difficult to separate and determine the thickness of each layer. Alternatively, even if the thicknesses of the layers are not close to each other, the interference spectra of the layers affect each other, and the interference peak of the layer to be measured cannot be accurately detected.

At this time, 600 n of the polyolefin layer
When the light transmittance at m is 0 to 85%, the intensity of reflected light other than the reflected light at the irradiation surface and the reflected light at the interface between the polyester layer and the polyolefin layer can be sufficiently attenuated, and the polyester layer and the polyolefin Since the reflected light intensity at the layer interface can be set to a sufficient intensity, the thickness of the polyester layer can be accurately measured.

Since the measurement result of the thickness of the polyester layer which is continuously measured on-line by such a method can be fed back to the thickness adjusting equipment promptly, it is possible to obtain a multilayer film in which the thickness unevenness of the polyester layer is good. still,
The value of n in the above formula (I) (the average value of the refractive index of the polyester layer in the machine direction and the average value in the transverse direction) shows a substantially constant value if the stretching condition of the multilayer film is constant. When the value is used in the above formula (I), the thickness of the polyester layer can be detected online only by measuring the peak wavelength interval of the interference fringes or the valley wavelength interval of the adjacent interference fringes.

The thickness of each layer of the multi-layer film can be measured by the following method. For example, a multi-layer film is composed of a polyester layer and a polyolefin layer 2
In the case of a layer film, by irradiating a light beam from the surface of the polyester layer, the thickness of the polyester layer can be continuously measured by the method described above, but at the same time, the thickness of the multilayer film can be measured by a γ-ray thickness meter or a β-ray thickness meter. By measuring the total thickness and subtracting the thickness of the polyester layer from this thickness, the thickness of the polyolefin layer can also be continuously measured. The thickness of each layer of the two-layer film can be measured by measuring only the thickness of one side of the polyester layer, if necessary.

When the multilayer film is, for example, a three-layer film consisting of a polyester layer / polyolefin layer / polyester layer, the thickness of the outer polyester layer is continuously measured by irradiating light from both sides of the multilayer film. At the same time, the total thickness of the multilayer film is measured by the method described above, and the thickness of the polyolefin film layer can be continuously measured by subtracting the thicknesses of the polyester layers of both outer layers from this thickness. The thickness of each layer of the three-layer film can be measured by measuring only the thickness of one side of the polyester layer or both outer layers of the polyester layer, if necessary.

[Polyester Layer] In the present invention, the polyester constituting the polyester layer is a linear polyester comprising a dicarboxylic acid component and a glycol component.

Examples of the dicarboxylic acid component include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid and 4,4-diphenyldicarboxylic acid, and particularly terephthalic acid and 2,6-naphthalenedicarboxylic acid. Is preferred.

Examples of glycol components include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl. Examples thereof include glycol, and particularly ethylene glycol, 1,4
-Butanediol is preferred.

The above-mentioned polyester is a homopolymer of polyethylene terephthalate, polyethylene 2,6-naphthalene dicarboxylate or polybutylene terephthalate, and the mechanical properties and thermal properties of the polyester film obtained by peeling and separating from the laminated film are It is preferable because it has excellent characteristics.

The polyester in the present invention may be a polyester obtained by copolymerizing a small amount (for example, a proportion of 10 mol% or less) of a copolymerization component, and a trifunctional or higher polyvalent compound makes the polyester substantially linear. It may be a polyester copolymerized in the range (for example, 5 mol% or less).

As the copolymerization component, in addition to the above components,
Examples thereof include hexahydroterephthalic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, 1,3-propanediol, polyethylene glycol, polytetramethylene glycol, dipropylene glycol, triethylene glycol and bisphenol A.

The polyester used in the present invention may be a blend of the above homopolymers or copolymers.

The polyester used in the present invention is 2
It is preferable that the volume resistivity value in the molten state at 70 ° C. is 0.5 × 10 ⁹ Ω · cm or less under the measurement condition of the AC voltage of 50 Hz. When the volume resistivity is in this range, the electrostatic application to the laminated film becomes strong during casting, and the adhesion between the cooling drum and the laminated film becomes good. The polyester having such a volume resistivity value can be obtained, for example, by blending a compound having an alkali metal salt with the polyester. Incidentally, it is preferable to use a polyester to which a quaternary phosphonium salt of sulfonic acid is added, or to use a copolymer thereof, because the adhesion between the multilayer film and the cooling drum is further improved.

The thickness of the polyester layer in the present invention is
The thickness is 0.2 to 100 μm, and particularly preferably 0.5 to 30 μm. Thickness of polyester layer is 0.2μ
When it is less than m, the peak wavelength interval of the adjacent interference fringes or the valley wavelength interval of the adjacent interference fringes becomes too long when the thickness is measured by the optical interference film thickness meter, and the reflected light interferes only in the visible light range. Cannot be detected. If the thickness of the polyester layer exceeds 100 μm, a spectroscope having a resolution higher than 1 nm is required, which makes measurement difficult.

Further, in order to improve the winding property of the polyester layer separated and separated and to satisfy the surface property required for each application, the polyester has an average particle size of about 0.001 μm to 5.0 μm, and organic or inorganic. Particles of, for example, 0.
It can be contained in a blending ratio of 01 wt% to 2.0 wt%. Examples of such fine particles include dry silica, wet silica, zeolite, calcium carbonate, calcium phosphate, kaolin, kaolinite, clay, talc, titanium oxide, alumina, zirconia, aluminum hydroxide, calcium oxide, graphite, carbon black, zinc oxide, Examples thereof include inorganic particles such as silicon carbide and silver oxide, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, and organic particles such as crosslinked silicone resin particles.

If necessary, a lubricant, an antioxidant, an antistatic agent, a colorant, a pigment, a tendency brightening agent, a plasticizer, a cross-linking agent, an ultraviolet absorber, or another resin may be added to the polyester. be able to.

[Polyolefin Layer] In the present invention, the polyolefin constituting the polyolefin layer is a polymer obtained by polymerizing an olefin compound, and may be a homopolymer or a copolymer.

Examples of the polyolefin include low density polyethylene, high density polyethylene, polypropylene, polybutene, and copolymers thereof. Of these polyolefins, the melting point is 1
Polypropylene or copolymerized polypropylene at 00 ° C to 170 ° C is preferable because it is excellent in coextrudability and costretchability with polyester. Examples of the copolymerized polypropylene include propylene / ethylene copolymers (block copolymers having a copolymerization component ratio of 50 mol% or less, random copolymers, graft copolymers, etc.).

The polyolefin may also be a mixture of polypropylene and / or copolymerized polypropylene with other olefins (eg polyethylene).

The thickness of the polyolefin layer in the present invention is 2 to 100 μm. The thickness of the polyolefin layer is 2μ
When it is less than m, the light transmittance of the polyolefin layer is 85.
% Or less is difficult. Even if the thickness of the polyolefin layer is less than 2 μm, the light transmittance of the polyolefin layer can be 85% or less by blending the polyolefin with a high concentration of inert particles (for example, a concentration exceeding 15% by weight). When the polyester layer is peeled off from the polyolefin layer, breakage occurs in the polyolefin layer, the surface roughness of the polyolefin layer becomes too rough, and this is transferred to the polyester layer and the surface characteristics of the polyester film obtained by peeling off from the multilayer film. Will be inferior, and the reflected light at the interface between the polyester layer and the polyolefin layer will be indefinite due to irregular reflection. When the thickness of the polyolefin layer exceeds 100 μm, the polyester layer and the polyolefin layer are separated from each other in a step of cooling the multilayer film with a cooling drum into an unstretched film, a step of uniaxially stretching the unstretched film in the longitudinal direction, and the like. It may peel off and separate, which causes inconveniences such as difficulty in producing a good multilayer film.

The polyolefin layer of the present invention has a light transmittance of 0 to 85% at a wavelength of 600 nm. If this light transmittance exceeds 85%, the intensity of the reflected light other than the reflected light at the interface between the polyester layer and the polyolefin layer cannot be sufficiently attenuated, so that the thickness of the polyester layer cannot be accurately measured.

Examples of the method for adjusting the light transmittance of the polyolefin layer to 85% or less include, for example, a method of adding inactive particles to the polyolefin constituting the polyolefin layer, a method of increasing the thickness of the polyolefin layer, and a stretching of the polyolefin layer. And the like, and the like can be used in combination.

Of the above methods, the method of adding inert particles to the polyolefin is preferable because the light transmittance can be 85% or less even in the case of a thin polyolefin layer. As this method, for example, polyolefin has an average particle diameter of 0.01 to 1.0 μm (especially 0.1 to 0.
It is preferable that 0.1 to 15% by weight of the inert particles of 8 μm) be mixed. 15% by weight of inert particles
When it exceeds, the irregularities on the surface of the polyolefin layer become remarkable,
This unevenness is not preferable because the surface characteristics of the polyester film obtained by transferring to the polyester layer and peeling and separating from the multilayer film may become poor.

The particle size of the inert particles added to the polyolefin is preferably 0.01 to 1.0 μm in order to make the reflected light at the interface between the polyester layer and the polyolefin layer clear, and 0.1 It is particularly preferable that the thickness is 0.8 μm. If the particle diameter of the inert particles is less than 0.01 μm, the effect of reducing the light transmittance of the polyolefin layer is insufficient, and if it exceeds 1.0 μm, the irregularities on the surface of the polyolefin layer become remarkable, and these irregularities are transferred to the polyester layer. Then, the polyester film obtained by peeling and separating from the multi-layer film may have poor surface characteristics and the reflected light at the interface between the polyester layer and the polyolefin layer may become unclear due to irregular reflection, which is not preferable.

The inert particles to be blended with the polyolefin may be of any type as long as it can reduce the light transmittance of the polyolefin layer. For example, dry silica, wet silica, zeolite, calcium carbonate, calcium phosphate, kaolin, kaolinite, clay, talc, titanium oxide, alumina, zirconia, aluminum hydroxide, calcium oxide, graphite, carbon black, zinc oxide, silicon carbide, silver oxide. Examples thereof include organic fine particles such as inorganic fine particles, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, and crosslinked silicone resin particles. In particular, titanium oxide, calcium carbonate, and carbon black are preferable because they have an excellent effect of reducing the light transmittance of the polyolefin layer.

The thickness of the polyolefin layer to which the inert particles are added, the transmitted light intensity, the incident light intensity, the extinction coefficient, and the concentration of the inert particles are determined by the law (Lambert-Beer's law) represented by the following formula (II). ).

[0036]

[ ^Equation 3] τ = 10 ^-kcd (II)

In the formula (II), τ is the light transmittance, k is the extinction coefficient, c is the concentration [wt%] of the inert particles, and d is the thickness [μm] of the polyolefin layer.

When the inert particles are added to the polyolefin so that the light transmittance of the polyolefin layer is 85% or less, the concentration of the inert particles and the thickness of the polyolefin layer can be determined using the above formula (II). it can.

In the polyolefin layer, it is preferable to use those inert particles having a sharp particle size distribution to make the dispersion state as uniform as possible. In order to make the dispersed state of the inert particles uniform, for example, master pellets obtained by kneading and extruding with a twin-screw kneader (mixed with a high concentration of inert particles in polyolefin) are added to the polyolefin pellets. It is possible to use a method used for extruding the film, a method for extruding the film by using pellets obtained by kneading and extruding with a twin-screw kneader in advance (inert particles are blended in advance with polyolefin). In addition, when the film is extruded, the polyolefin pellets may be mixed with inert particles and used.

Further, in order to improve the adhesion between the cooling drum and the laminated film, it is preferable to add a quaternary phosphonium sulfonate or an alkali metal salt to the polyolefin.

[Multilayer Film] In the multilayer film of the present invention, at least one of the outermost layers is a polyester layer (hereinafter sometimes abbreviated as “E layer”), and a layer adjacent thereto is a polyolefin layer (hereinafter referred to as “O layer”). However, the number of layers and the mode thereof are not limited. The preferred structure of such a multilayer film is, for example, a two-layer film consisting of E layer / O layer, E layer / O layer /
A three-layer film composed of the E layer can be mentioned.

In the present invention, polyester and polyolefin are used as the polymer constituting each layer of the multi-layer film, and the polyester and polyolefin having a solubility parameter (SP value) difference of 1 or more, particularly 2 or more are used in combination. It is preferable that the polyester layer or the polyolefin layer can be easily peeled and separated from the multilayer film, and the separated layer can be wound in a good winding shape.

In the multilayer film of the present invention, the interlayer adhesive force between the polyester layer and the polyolefin layer is 0.
It is preferably 1 to 20 g / cm, particularly preferably 0.1 to 10 g / cm. If the interlaminar adhesive strength is less than 0.1 g / cm, peeling may occur in the film forming process, or wrinkles or tears may occur due to delamination or misalignment between layers when the multilayer film is rolled and stored or transported. This is not preferable because trouble may occur. Further, when a polyester layer having an interlayer adhesive strength of more than 20 g / cm is peeled from the multilayer film, the film may be broken or pinholes may be formed, which is not preferable.

The multilayer film of the present invention may be an unstretched film, a uniaxially stretched film or a biaxially stretched film, but a biaxially stretched film is particularly preferable because it has excellent mechanical properties.

[Compounding Agent] In the polyester and / or the polyolefin constituting each layer of the laminated film of the present invention, a lubricant is added, for example, 0.001 to 1 wt% in order to adjust the adhesive force between the polyester layer and the polyolefin layer, More preferably, 0.005 to 0.5 wt% can be added.

This lubricant may be liquid or solid at room temperature, and preferably has a melting point or softening point of 200 ° C. or lower. The following may be mentioned as specific examples of the lubricant, and two or more kinds of these may be used. A. Aliphatic hydrocarbons: liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin, polyethylene wax, polypropylene wax, etc. Higher fatty acid or metal salt thereof: stearic acid, calcium stearate, hydroxystearic acid, hydrogenated oil, sodium montanate, etc. Aliphatic amide: stearamide, oleamide, erucamide, ricinoleamide, behenamide, methylenebisstearamide, etc. Fatty acid esters: n-butyl stearate, methylhydroxystearate, myristyl celloate, high alcohol fatty acid esters, ester waxes, etc. Aliphatic ketone: Ketone wax, etc. F. Fatty alcohol: lauryl alcohol, stearyl alcohol, myristyl alcohol, cetyl alcohol, etc. Partial ester of fatty acid and polyhydric alcohol: glycerin fatty acid ester, hydroxystearic acid triglyceride, sorbitan fatty acid ester, etc. Nonionic surfactants: polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, polyoxyethylene alkyl amide, polyoxyethylene fatty acid ester, etc. Silicone oil: linear methyl silicone oil, methylphenyl silicone oil, modified silicone oil, etc. J. Fluorosurfactants: fluoroalkyl carboxylic acid, perfluoroalkyl carboxylic acid, monoperfluoroalkyl ethyl phosphate, perfluoroalkyl sulfonic acid salt, etc.

[Manufacturing Method of Multilayer Film] In the present invention, at least one of the outermost layers is a polyester layer having a thickness of 0.2 to 100 μm, and the layer adjacent thereto is 60.
The light transmittance at 0 nm is 0 to 85% and is 2 to 10
When manufacturing a multilayer film which is a polyolefin layer having a thickness of 0 μm, the thickness pattern in the width direction of the polyester layer is measured by an optical interference type film thickness meter, and the result is used to make the thickness pattern in the width direction of the polyester layer uniform. A multi-layer film can be produced by using it for adjustment.

For example, polyester and polyolefin are fed to separate extruders and the melting point of each polymer is not less than 3
Melt to a temperature of up to 50 ° C, combine the molten polymers in the conduit or inside the die (die) to form a multi-layered state, discharge this from the die, and apply an electrostatic charge to the discharge film. An unstretched multilayer film can be produced by cooling and solidifying with a cooling drum. This unstretched multilayer film may have any number of layers as long as at least one of the outermost layers is a polyester layer and has a polyolefin layer adjacent thereto, but in order to measure the thickness of all polyester layers, Two
Layers and trilayer films are preferred.

The above-mentioned unstretched multilayer film can be further uniaxially or biaxially stretched to obtain a uniaxially stretched multilayer film or a biaxially stretched multilayer film. This uniaxially stretched multilayer film has a temperature (for example, Tg of polyester) at which the unstretched multilayer film can be stretched.
It can be obtained by heating at (glass transition temperature) or higher and a temperature of Tg + 80 ° C. or lower) and uniaxially stretching in the machine direction or the transverse direction, for example, 2 to 12 times. The biaxially stretched multilayer film is, for example, a so-called longitudinal-transverse sequential stretching method in which an unstretched multilayer film is stretched in the machine direction at a temperature at which it can be stretched, and then stretched in the transverse direction, and it is simultaneously stretched in the machine direction and the transverse direction. It can be manufactured by the simultaneous biaxial stretching method. The biaxially stretched multi-layer film can be further re-stretched in the machine direction or the transverse direction to obtain a bi-axial re-stretched multi-layer film. In a biaxially stretched multi-layer film, for example, 2
It can be obtained by stretching each to 12 times. The stretching area ratio is preferably 5 to 50 times.

The above uniaxially stretched multilayer film or biaxially stretched multilayer film is further heat-treated at a temperature lower than Tm (melting point) of polyester, and then cooled to room temperature to give a uniaxially stretched (heat treated) multilayer film or biaxially stretched (heat treated). It can be a multilayer film.

The thickness of the polyester layer is adjusted by adjusting the width of the polyester layer in the width direction by using the result of measuring the thickness pattern of the polyester layer in the width direction with an optical interference type film thickness meter. By adjusting the opening degree and / or adjusting the temperature distribution of the die, it is possible to obtain a polyester layer having a small thickness unevenness. The multi-layer film thus obtained can be peeled and separated when slitting into a desired size to obtain a rolled polyester film.

The polyester raw material is preferably dried before being fed to the extruder. On the other hand, the polyolefin raw material does not necessarily need to be dried,
It is also possible to use a polyolefin that has been dried at a temperature lower than Tm (melting point).

The uniaxially stretched multi-layer film or the biaxially stretched multi-layer film is provided on the surface thereof, for example, Japanese Patent Publication No. Sho 56-183.
The surface activation treatment (for example, plasma treatment, amine treatment, corona treatment, etc.) as known from JP-B No. 81 and JP-B-57-30854 may be performed.

[Use of Multilayer Film] A polyester (single layer) film can be obtained by peeling and separating the polyester layer from the multilayer film of the present invention. Since this polyester film causes surface transfer from the polyolefin layer, it is difficult to use in applications where roughness is strictly required, but it can be used in various applications within the constraints of surface properties.

For example, a polyester film having a thickness of 3 μm or less, particularly an ultrathin single-layer film having a thickness of 1 μm or less is likely to cause breakage in the stretching step or winding failure in the winding step, so that the single-layer film is not easily manufactured. Although not present, it can be easily obtained by peeling and separating from the multilayer film of the present invention.

The step of peeling and separating the polyester layer from the multi-layer film is effective in handling the film and preventing wrinkles and abrasions of the film from occurring in the final step as much as possible. It is preferable to peel and separate in the manufacturing process.

Such a polyester single-layer ultrathin film can be used as a heat sensitive stencil printing film (for example, a film having a thickness of about 1.5 μm), a capacitor film (for example, a film having a thickness of 3 μm or less), a printer ribbon film (for example, a film thickness of 5 μm). It is useful for film and so on.

Further, from the biaxially stretched multi-layer film of the present invention, by separating and separating each layer, a biaxially stretched single-layer film can be obtained simultaneously in a plurality of two or more sheets with high efficiency and low cost. You can

[0059]

EXAMPLES The present invention will be described in more detail with reference to examples. In addition, each characteristic value was measured by the following method.

1. Polyester layer thickness Using a reflection-type optical interference thickness meter that uses a halogen lamp as a visible light wavelength emission lamp, the peak wavelength (λ ₁ , λ ₂ ) of adjacent interference fringes, the peak wavelength interval (λ ₁ −λ ₂ ) and The thickness was measured online from the average value n of the refractive index of the polyester layer in the longitudinal direction and the lateral direction according to the following formula (I).

[0061]

T = (λ ₁ × λ ₂ ) / [2 × n × (λ ₁ −λ ₂ )] …… (I)

In the formula (I), t is the thickness of the polyester layer [nm], and λ ₁ and λ ₂ are the peak wavelength (n of the interference fringe).
m) (λ ₁ > λ ₂ ), and n is the average refractive index in the machine direction and the transverse direction of the polyester layer. When the multi-layer film is a two-layer film, the thickness of the polyester layer was measured online by irradiating the surface of the polyester layer with light. When the multi-layer film is a three-layer film, light rays were irradiated from both the front and back sides of the multi-layer film to measure the thickness of the polyester layers of both outer layers online.

2. Measurement of Thickness Unevenness The thickness of each layer separated and separated from the multilayer film was measured off-line using a reflection-type optical interference thickness meter using a halogen lamp. The film width was set to 1 m, and the difference between the maximum value and the minimum value of the thickness of the film in the width direction was defined as the thickness variation value.

3. Light transmittance The visible light transmittance spectrum was measured using a spectrophotometer manufactured by Shimadzu Corporation, and the transmittance at a wavelength of 600 nm was defined as the light transmittance.

4. Adhesion Strength The multilayer film was cut into a size of 10 mm in width and 100 mm in length, and the tension [g] applied when the polyester layer was continuously peeled from the polyolefin layer at a peeling angle of 180 ° at a speed of 2 m / min was measured. The adhesive force (T [g / cm]) was defined as the tension per 1 cm width obtained from the average value of the tension [g] and the sample width (10 mm).

5. Melting point DSC (manufactured by DuPont, V4.0B2000 type machine) was used to heat the sample (10 mg) at a heating rate of 20 ° C./min, and the temperature corresponding to the top of the endothermic peak accompanying melting was measured. The melting point (Tm) was used.

6. Glass transition temperature The glass transition temperature (Tg) was measured by heating the sample (10 mg) using a DSC (V4.0B2000 type, manufactured by DuPont) at a temperature rising rate of 20 ° C./min.

7. Intrinsic Viscosity of Polyester Measured at 35 ° C as a solution in orthochlorophenol.

8. Surface roughness (Ra) The center line average roughness (Ra) was measured according to JIS B 0601. That is, using a stylus-type surface roughness meter manufactured by Kosaka Laboratory Ltd., a chart (film surface roughness curve) was applied under the conditions of a needle radius of 2 μm and a load of 0.07 g, and the obtained film surface was obtained. From the roughness curve, extract the part of measurement length L in the direction of the center line, and draw the center line of this extracted part as X.
Roughness curve Y = f
When expressed by (x), the value given by the following formula (Ra: μ
m) is defined as the surface roughness (Ra). In the present invention,
8 pieces are measured with a reference length of 0.25 mm, and Ra is expressed as an average value of 5 pieces excluding 3 pieces from the largest value.

[0070]

(Equation 5)

9. Process characteristics (adhesion) Adhesion between the polyester layer and the polyolefin layer in the process of cooling the multilayer film with a cooling drum to obtain an unstretched film, and the process of uniaxially stretching the unstretched film in the longitudinal direction (with the polyester layer). The property of not peeling and separating from the polyolefin layer) was evaluated according to the following criteria. ◎: Peel separation does not occur at all …… Adhesion is extremely good ○: Peel separation does not occur at all by adjusting roll temperature and film tension …… Good adhesion Δ: Peel separation hardly occurs at roll temperature and film tension adjustment… … Slightly good adhesion ×: Peeling and separation frequently occur even if the roll temperature and film tension are adjusted.

10. Process characteristics (winding property) The characteristics (winding property) in which the polyolefin layer is not cut in the process of peeling and separating the polyester layer and the polyolefin layer from the multilayer film and winding each layer in a roll shape are evaluated according to the following criteria. did. ⊚: No cutting of the polyolefin layer at all …… Extremely good winding property ○: No cutting at all by adjusting tension of the polyolefin layer …… Good winding property Δ: Almost no cutting at adjusting tension of the polyolefin layer… … Slightly good windability ×: Frequent cutting occurs even if the tension of the polyolefin layer is adjusted.

Example 1 As a polyester raw material, 0.08% by weight of spherical silica having an average particle size of 1.5 μm and 0.3% by weight of a cataloid having an average particle size of 0.12 μm were blended to obtain an intrinsic viscosity of 0.1. Pellets of 60 polyethylene terephthalate (Tm: 256 ° C., Tg: 68 ° C.) were used, dried at 170 ° C. for 3 hours, then fed to an extruder and melt-extruded at 280 ° C. On the other hand, as a polyolefin raw material, polypropylene (polypropylene / polyethylene / random copolymer, Tm: 168) containing 1.0% by weight of anatase-type titanium having an average particle size of 0.3 μm was blended.
C., melt flow rate 10 g / 10 min) was dried at 100.degree. C. for 2 hours, then fed to another extruder and melt-extruded at 280.degree. C. like polyethylene terephthalate. After each molten polymer was merged inside the die to form a three-layer structure of polyethylene terephthalate / polypropylene / polyethylene terephthalate, it was discharged from the die,
Then, it was cooled and solidified by being wound around a cooling drum kept at 20 ° C. while applying an electrostatic charge to obtain a three-layer unstretched multilayer film. Then, the unstretched multilayer film is brought into contact with a heating roll and heated to 100 ° C., and then stretched by 3.6 times in the longitudinal direction, immediately cooled to 20 ° C., and subsequently, a tenter type transverse stretching device is used in the transverse direction. At 100 ° C.
After being stretched 9 times, it is heat treated at 210 ° C., cooled to room temperature, and has a triaxial structure of a polyethylene terephthalate layer (drum surface side) / polypropylene layer / polyethylene terephthalate layer (air surface side) having a width of 1.1 m. A stretched multilayer film was obtained. In the above process, the adhesion between the polyester layer and the polyolefin layer was extremely good.

In the process of cooling the multi-layer film to room temperature, the thickness of the polyethylene terephthalate layers of both outer layers was measured by a reflection type optical interference film thickness meter, and the thickness adjustment and the thickness unevenness adjustment were performed based on this measurement result. Done and rolled up. At this time,
The thickness of the polyethylene terephthalate layer could be accurately and stably detected by the optical interference film thickness meter.

The biaxially stretched multilayer film thus obtained had an average thickness of the polyethylene terephthalate layer (drum side) of 4.5 μm, an average thickness of the polypropylene layer of 1.0 μm and an average of the polyethylene terephthalate layer (air side). The thickness was 4.6 μm, and the thickness unevenness (difference between the maximum value and the minimum value) in the width direction at a width of 1 m of the polyethylene terephthalate layer (drum surface and air surface) was 0.30 μm, which is very good. It was a thing.

Then, the multilayer film was slit by a slitter to a width of 1.0 m, each layer was separated and separated, and each layer was wound into a roll. In this step, the peeling and separating property (winding property) of the multilayer film was such that cutting did not occur without adjusting the tension of the polyolefin layer. Also,
The rolled state of the polyester layer was also very good without any irregularities on the end face.

The center line average roughness (Ra: surface roughness) of the polyethylene terephthalate film obtained from this polyethylene terephthalate layer (drum surface side) is 25 nm on the drum surface side and 25 nm on the release surface side from the polypropylene layer. And was extremely good. The light transmittance of the polypropylene layer at 600 nm was 83%.

[Examples 2 to 7 and Comparative Examples 1 to 3] The thickness of the polyolefin layer, the blending ratio of the inert particles (titanium oxide) blended in the polyolefin, and the light transmittance of the polyolefin layer are as shown in Table 1. Example 1 except
A multilayer film was obtained in the same manner as. Table 2 shows the evaluation results of the obtained multilayer film.

[0079]

[Table 1]

[0080]

[Table 2]

In Table 2, ⊚ indicates extremely good, ∘ indicates good, Δ indicates slightly good, and x indicates poor. As is clear from the results shown in Table 1 and Table 2, Example 1
The multilayer film of Nos. 7 to 7 has a polyester layer thickness measuring property,
It was excellent in thickness unevenness, surface roughness, adhesion of multi-layer film and winding property.

[0082]

The multi-layer film of the present invention is excellent in the unevenness in thickness and surface roughness of the polyester layer, the adhesion of the multi-layer film and the winding property. Further, it can be obtained by peeling and separating a thin polyester single-layer film or polyolefin single-layer film from the multilayer film of the present invention. Particularly, the polyester single-layer film is a film for capacitors, a film for heat-sensitive stencil printing, a printer repon. It is useful as a base film for a magnetic recording tape such as a recording film and a video tape.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B29K 23:00 67:00 B29L 9:00

Claims (8)

[Claims] 1. At least one of the outermost layers is 0.2 to 10.
When a multilayer film having a thickness of 0 μm and a layer adjacent thereto having a light transmittance of 600 nm of 0 to 85% and a polyolefin layer of a thickness of 2 to 100 μm is produced by coextrusion, the width of the polyester layer is A method for producing a multi-layer film, comprising adjusting a thickness pattern in a width direction using a result of a width pattern in a width direction of a polyester layer measured by an optical interference type film thickness meter. 2. Adjusting the width of the polyester layer in the width direction,
2. The polyester layer is controlled by adjusting the opening degree of the extrusion die and / or adjusting the temperature distribution of the die.
A method for producing the described multilayer film. 3. The thickness in the width direction of the polyester layer is calculated by the following formula (I) using an optical interference type film thickness meter.
A method for producing the described multilayer film. ## EQU1 ## t = (λ ¹ × λ ² ) / [2 × n × (λ ¹ −λ ² )] (I) [wherein, t in the formula (I) is the thickness of the polyester layer (n
m), λ ¹ and λ ² are peak wavelengths (nm) of adjacent interference fringes or valley wavelengths (nm) of adjacent interference fringes
(Λ ¹ > λ ² ), where n is the average value of the refractive index of the polyester layer in the longitudinal and transverse directions] 4. The average particle diameter of the polyolefin layer is 0.01 to
The method for producing a multilayer film according to claim 1, which comprises 0 to 15% by weight of 1.0 μm inactive particles. 5. The method for producing a multilayer film according to claim 4, wherein the inactive particles are at least one kind of particles selected from the group consisting of titanium oxide, calcium carbonate and carbon black. 6. At least one of the outermost layers is 0.2 to 10.
A multilayer film produced by coextrusion, which is a polyester layer having a thickness of 0 μm, and a layer adjacent to the polyester layer having a light transmittance at 600 nm of 0 to 85% and a thickness of 2 to 100 μm. A multilayer film in which the width pattern of the polyester layer in the width direction is adjusted by using the result of the thickness pattern of the polyester layer in the width direction measured by an optical interference type film thickness meter. 7. The average particle size of the polyolefin layer is 0.01 to
7. The multilayer film according to claim 6, which comprises 0 to 15% by weight of 1.0 μm inactive particles. 8. The multilayer film according to claim 6, wherein the inactive particles are at least one kind of particles selected from the group consisting of titanium oxide, calcium carbonate and carbon black.