KR20200098482A - Biaxially Oriented Laminated Film - Google Patents

Abstract

It is a laminated film having a layer containing inert particles (layer A) containing as a main component a thermoplastic resin A having a thickness of 0.5 μm or more and 2.0 μm or less on at least one side of a layer (layer B) containing thermoplastic resin B as a main component, and the laminated Provided is a biaxially oriented laminated film in which the film satisfies specific requirements without impairing transparency, and suppresses a decrease in yield due to a wound during film formation and a wound during surface processing.

Description

Biaxially Oriented Laminated Film

The present invention relates to a biaxially oriented laminated film with few scratches and excellent transparency of the film after high-temperature heat treatment and suppression of thermal deformation.

Polyester films are used in various fields because of their excellent transparency, dimensional stability, mechanical properties, heat resistance, and electrical properties. In particular, in recent years, those used as a base material for a transparent conductive laminate used for touch panels, electronic papers, and surface protective films thereof have been increasing.

When using a polyester film for the above purposes, it is required to have high transparency (light transmittance) and no surface defects such as scratches and defects. For example, the base film used for the transparent electrode of a touch panel is made into a transparent electrode by subjecting it to a hard coat process to form a transparent conductive layer, which is attached to a liquid crystal display device as a touch panel module and used. In the touch panel, in order to obtain a touch panel having a clear display in order to visually recognize a liquid crystal display through a transparent electrode, it is required that the base film used for the transparent electrode of the touch panel is highly transparent and has no surface defects. In general, films with less surface defects reduce scratches and defects on the film surface by increasing the sliding properties of the film surface. In order to increase the slidability of the film, it is necessary to add particles to the film. However, since the addition of particles contributes to a decrease in transparency, it is very difficult to achieve both high transparency and reduction of surface defects (Patent Document 1).

In addition, in the manufacturing process of a transparent electrode for a touch panel, the transparent conductive film on which a transparent conductive film made of ITO (Indium Tin Oxide) is formed is annealing treatment, crystallization process of ITO, printing process of resist, edging process, etc. It goes through many heating processes and processes of chemical liquid treatment (patent document 2). In these treatment processes, low molecular weight substances (oligomers) remaining in the polyester film or generated by thermal decomposition, etc., precipitate on the surface, whitening the appearance of the polyester film, reducing the yield due to transfer to ITO, contamination of the process, extra cleaning, etc. There is a problem of increasing the number of processes and greatly reducing the productivity of the product. In particular, in recent years, in order to reduce the additional electrical resistance of ITO, the heat treatment of the ITO proceeds to increase the temperature and increase the temperature for a longer period of time, and more advanced heat distortion resistance is required, and the challenge of smartphones or tablets equipped with a capacitive touch panel. The demand for densification and appearance quality of circuits is becoming more and more advanced, and further suppression of oligomer precipitation on the film surface is required.

Japanese Patent Publication No. 2014-46569 Japanese Patent Laid-Open No. 2007-42473

In order to reduce surface defects caused by wounds, a method of increasing the sliding property of the surface by making a film in a three-layer structure and adding particles to only the surface is known. For example, in Patent Literature 2, the reduction of the wound is suppressed by adding particles of 4 to 12 µm to the surface layer, but there is a problem with a large haze. In order to increase the slidability of the film surface, it is necessary to add particles having a large average particle diameter. However, when particles are added to the film, voids are formed from the particles as a starting point when the film is stretched, so that the haze inside the film is reduced. There is a problem in that the visibility is increased and the visibility is lowered. In general, the haze of a film (hereinafter referred to as total haze) is classified into a haze caused by scattering on the surface of the film (hereinafter, surface haze) and a haze caused by scattering inside the film (hereinafter, internal haze). Since haze contributes even after surface processing such as a hard coat, there is a problem in that visibility decreases when a touch panel is formed.

In addition, it is generally known that oligomers move to the surface by moving microspaces inside the film when heated, crystallize, and precipitate. Therefore, an increase in voids due to the addition of particles promotes an increase in haze during the heating process. It becomes the cause of.

As a result of intensive investigation in view of the above problems, the inventors of the present invention have found that the above problems can be solved with a film having a specific configuration, and the present invention has been completed.

That is, the present invention achieving the above object is obtained by the following.

The present invention to achieve the above object is as follows.

[1] A laminated film having a layer containing inert particles (layer A) containing as a main component a thermoplastic resin A having a thickness of 0.5 μm or more and 2.0 μm or less on at least one side of a layer (layer B) containing thermoplastic resin B as a main component. , A biaxially oriented laminated film in which the laminated film satisfies the following requirements (1) to (3).

(1) Internal haze of 0.5% or less.

(2) A 10-point average roughness (SRz) of the surface of the layer A on the surface opposite to the surface of the layer A in contact with the layer B is 250 nm or more.

(3) The amount of change in the total haze before and after heat treatment at 150°C for 30 minutes is 2.0% or less.

[2] The biaxially oriented laminated film according to [1], wherein the amount of change in total haze before and after treatment at 150°C for 180 minutes is 2.0% or less.

[3] The biaxially oriented laminated film according to claim [1] or [2], wherein the total haze is 3% or less.

[4] The biaxially oriented laminated film according to any one of [1] to [3], wherein the cold crystallization temperature (Tcc) of the layer B is 150°C or more and less than 165°C.

[5] The biaxially oriented laminated film according to any one of claims [1] to [4], wherein the content of the cyclic trimer in the layer B is 0.01% by mass or more and 1.00% by mass or less.

[6] Claims having at least one maximum value in the range of 0.8 to 2.0 µm in particle diameter when the particle size distribution of the inert particles contained in the layer A is measured, and the particle diameter on the horizontal axis and the proportion of particles on the vertical axis are plotted [ The biaxially oriented laminated film according to any one of 1] to [5].

[7] Claims having at least one maximum value in the range of 0.1 μm to 0.5 μm in particle diameter when the particle size distribution of the inert particles contained in the layer A is measured and the particle diameter on the horizontal axis and the proportion of particles on the vertical axis are plotted. The biaxially oriented laminated film according to any one of [1] to [6].

[8] The biaxially oriented laminated film according to any one of claims [1] to [7], in which the inert particles contain calcium carbonate particles.

[9] The biaxially oriented laminated film according to any one of claims [1] to [7], wherein the inert particles contain organic particles containing a styrene component.

[10] The biaxially oriented laminated film according to any one of [1] to [9], wherein the difference between the total haze and the internal haze is 0.8% or more.

[11] The biaxially oriented laminated film according to any one of claims 1 to 10, wherein the layer A is on at least one surface layer.

[12] The biaxially oriented laminated film according to any one of claims 1 to 11, wherein the inert particles contained in the layer A are 0.01 to 0.5% by mass.

According to the present invention, it is possible to obtain a biaxially oriented laminated film that suppresses a decrease in yield due to a wound during film formation and a wound during surface processing without impairing transparency. Therefore, the biaxially oriented laminated film of the present invention can be suitably used as a base film or a protective film of a transparent conductive laminate, and the industrial value of the present invention is high.

Next, an embodiment for implementing the biaxially oriented laminated film of the present invention will be described in detail. In addition, the "film" in the present invention is used with a meaning including a two-dimensional structure such as a sheet, a plate, and a film.

The laminated film of the present invention has a layer containing inert particles (layer A) containing as a main component a thermoplastic resin A having a thickness of 0.5 μm or more and 2.0 μm or less on at least one side of the layer (layer B) containing the thermoplastic resin B as a main component. It needs to be a laminated film. When the thickness of the layer A is 2.0 µm or more, it is necessary to add 2 µm or more particles in order to form projections on the film surface, and when such particles are added, it is not preferable because it leads to an increase in internal haze. On the other hand, in order to improve the sliding property of the film surface, it is preferable to add many particles. However, in the case of obtaining a biaxially oriented film, a process of orienting the film (usually, a stretching process) is performed, but particles added to form projections on the film surface are used in the stretching process of the resin constituting the film. As a result of being unfollowable, voids occur around the particles. Voids generated here raise the internal haze of the film more than the particles. Therefore, when a film to which a large number of particles are added is biaxially oriented, not only the internal haze increases due to the particles, but also the internal haze increases due to the voids generated around the particles.

As a result of examining this phenomenon, the present inventors found that even if a large number of particles were added, the layer to which the particles were added was present on the surface layer of the film, and when the thickness was thin, voids were difficult to occur and internal haze was difficult to increase. . The reason why this phenomenon is obtained is not clear at present, but the inventors of the present invention estimate as follows. In the process of orienting the film (usually, the stretching process), the surface is exposed to a higher temperature than the inside of the film. Therefore, in the process of orienting the film (usually, the stretching process), the fluidity of the thermoplastic resin is higher on the surface of the film, so it is estimated that it is easy to follow at the time of stretching. Therefore, it is preferable that the A layer is in at least one surface layer of the laminated film. It is more preferable that the A layer is in both surface layers. The layer thickness of the layer A is preferably 2 µm or less, more preferably 1.5 µm or less. On the other hand, when the thickness of the layer A is less than 0.5 µm, it is necessary to add 0.5 µm or more particles to make the 10-point average roughness (SRz) 250 nm or more, but in that case, the particles are liable to drop out during film formation. As a result, it is not preferable because the part where the particles are removed may become a defect as it is. Here, as the relationship between the particle diameter (r) (µm) of the particles added to the layer A and the thickness (d) (µm) of the layer A, if r/d is 0.1 or more and 2 or less, while suppressing the increase in internal haze It is preferable because the sliding property of the film surface can be improved.

The internal haze of the laminated film of the present invention needs to be 0.5% or less. The internal haze is determined by canceling and measuring the surface haze by immersing the film in a solvent and measuring it by the method described in JIS-K-7105 (1985) in the measurement method described later. Since the total haze also contributes to light scattering, it is increased or decreased by the surface roughness, but since the film surface is often used after being surface-treated, the internal haze is essentially more important. When the internal haze is large, since the haze remains even after the surface treatment, visibility is poor. Therefore, the internal haze is preferably 0.4% or less, and more preferably 0.3% or less.

In addition, the laminated film of the present invention needs to have a 10-point average roughness (SRz) of 250 nm or more on the surface of the layer A on the surface opposite to the surface in contact with the layer B of the layer A. When the SRz of the A layer is 250 nm or more, the occurrence of scratches during film formation is suppressed and the yield is improved. Further, in a process such as ITO sputtering, since it is performed in a low pressure state (or in a vacuum state), higher sliding properties are required in order to suppress wounds during transportation. In order to improve the transportability in a low-pressure state, it is necessary to further increase SRz, and the SRz is preferably 400 nm or more, and more preferably 500 nm or more. In order to improve SRz, the relationship between the thickness of the particle addition layer and the particle diameter becomes important. On the other hand, when SRz is excessively increased, when the present film is used as an ITO base material, the transparent conductive layer may be disconnected and the function of the conductive layer may decrease. Moreover, in the case of using as a protective film, the surface of the conductive layer may be damaged by protrusions of the particles and disconnected. Therefore, the SRz is preferably 1000 nm or less.

The laminated film of the present invention was heat-treated at 150°C for 30 minutes, and the amount of change in the total haze before and after rapid cooling (after heating at 150°C for 30 minutes and before heating) (ΔHz 150°C for 30 minutes) It needs to be less than 2.0%. In general, when the film is heated, the cyclic trimer contained in the resin precipitates on the film surface to cause haze up. When ΔHz 150℃ for 30 minutes exceeds 2.0%, many cyclic trimers are deposited on the film surface, so in the case of a protective film of a transparent conductive laminate by bonding with other members, the precipitated cyclic trimers are relative It may be transferred to the surface of the member to deteriorate the quality of the product. Further, if the total haze after heating is high, the visibility in the case of a transparent electrode substrate and the inspection visibility in the case of a protective film of a transparent conductive laminate are lowered, which is not preferable. It is more preferably 1.0% or less, and still more preferably 0.5% or less.

In addition, in the laminated film of the present invention, the amount of change in total haze before and after treatment at 150°C for 180 minutes (change amount in total haze of the film after heating at 150°C for 180 minutes and before heating) (ΔHz 150°C for 180 minutes) is 2.0% or less. It is desirable. As also mentioned above, in recent years, it has been made to pass through a long heating process in preparation of a transparent electrode, and heat resistance for a longer time has been demanded. Therefore, heating stability over a longer period of time is required, more preferably 1.0% or less, further preferably 0.5% or less.

It is preferable that the total haze of the laminated film of the present invention is 1.0% or more and 3.0% or less. The total haze of the film is the total haze value after film formation, and it can be set as a film excellent in transparency by setting it as 3.0% or less. The total haze value is preferably 2.5% or less.

In the laminated film of the present invention, it is preferable that the difference between the total haze and the internal haze is 0.8% or more. The laminated film of the present invention is often used by applying an adhesive layer or a hard coat layer to its surface. In that case, since the surface of the laminated film is covered by the adhesive layer or the hard coat layer, the surface haze of the film depending on the surface roughness of the laminated film is canceled, so that the internal haze becomes more important. In the conventional method, in order to suppress wounds during film formation and wounds during surface processing, when protrusions are formed on the film surface by adding particles, not only the surface haze but also the internal haze increases, so that the total haze inevitably becomes large. On the other hand, in the present invention, by making the film into a specific configuration and containing particles, protrusions are formed on the film surface to increase the surface haze, but the internal haze is difficult to increase. Therefore, the difference between the overall haze and the internal haze tends to be large. The larger this difference is, the easier it is to suppress the occurrence of scratches on the surface, and the transparency can be ensured even after processing. In particular, when the difference is 0.8% or more, it is preferable because both transparency and suppression of wounds can be achieved. More preferably, it is 1.0% or more, and still more preferably 1.2% or more and 2.5% or less.

Layers A and B of the laminated film of the present invention need to have a thermoplastic resin as a main component. Among thermoplastic resins, polyester resins are excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc., and polyester films made of polyester resins are, for example, surface protection films for conductive films, and transparent conductive substrate films. It can be preferably used as. In addition, in the present invention, the main component refers to a component occupying 50% by mass or more with respect to the entire layer.

Polyester resin is a generic term for a polymer having an ester bond as the main bond chain of the main chain, and ethylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, ethylene-α,β-bis(2-chlorophenoxy) ) At least one constituent component selected from ethane-4,4'-dicarboxylate, etc. is used as the main component, and these constituents may be used alone or in combination of two or more, but among them, quality and economy When considered comprehensively, it is preferable to use polyethylene terephthalate as a main component. Further, in these polyester resins, another dicarboxylic acid component or diol component may be partially copolymerized, preferably 20 mol% or less.

When using a polyester resin as the thermoplastic resin constituting the present invention, the content of the alkali metal element contained in the polyester composition is M1 (mol/t), the content of the divalent metal element is M2 (mol/t), When the content of the trivalent metal element is M3 (mol/t), M (mol/ton) obtained as M = 0.5 × (M1) + M2 + 1.5 × (M3) and the content of phosphorus element P (mole The molar ratio (M/P) of /ton) is preferably in the range of 2.0 to 5.4. (In the formula, however, M is an alkali metal element, an alkaline earth metal element, and P is per 10 ⁶ g of a polyester of phosphorus element. It represents the total number of moles.) In general, since anions derived from phosphorus elements such as phosphoric acid have a trivalent negative charge, the cation of the monovalent metal element is 1:3 and the cation of the divalent metal element is 2:3. , It is thought that it interacts 1:1 with the cation of the trivalent metal element. However, as a result of intensive investigation by the present inventors, it was found that a phosphorus element derived from a phosphorus compound such as phosphoric acid interacts with a cation of a metal element as a divalent anion (M/P) (i.e., Under the premise that the anion interacts 1:2 with the cation of the monovalent metal element, 1:1 with the cation of the divalent metal element, and 3:2 with the cation of the trivalent metal element), When the M/P is 2.0 or more, the volume ratio resistance at the time of melting of the polyethylene terephthalate resin composition is lowered, and the electrostatic application casting method can be suitably used at the time of film molding, thereby suppressing the occurrence of variation in the thickness of the film. In addition, if the M/P is 5.4 or less, it becomes easy to suppress the regeneration of the cyclic trimer at the time of melting and the catalyst residue remaining as foreign matter in the film, so that the initial total haze value after film formation and the total haze value after heating can be reduced. I can. It is preferable to set it as the range of 2.5-4.5 further about M/P.

It is preferable that the intrinsic viscosity (IV) of the thermoplastic resin used in the laminated film of the present invention is 0.55 or more and 0.75 or less. When the intrinsic viscosity (IV) is within the above range, variation in thickness of the film is suppressed, and thus the film can be stably formed. If the intrinsic viscosity (IV) is less than 0.55, the melt viscosity is lowered, and local thickness deviation is liable to occur from the extrusion port to the landing of the resin on the drum for melting and cooling the resin, and the intrinsic viscosity (IV) is 0.75. If it exceeds, pressure is applied to the extrusion site in the extrusion process at the time of film formation, and thickness variation is liable to occur. More preferably, the intrinsic viscosity (IV) is 0.60 or more and 0.70 or less. In addition, the smaller the thickness deviation of the film, the less the non-uniformity of the refractive index can be suppressed in the longitudinal refractive index (nMD), the width direction refractive index (nTD), and the surface vertical refractive index (nZD) of the film, and the occurrence of interference deviation is reduced. It becomes easier to suppress. The thickness variation of the film is preferably 5.0% or less, and more preferably 3.0% or less in both the longitudinal direction (film formation direction) and width direction (direction perpendicular to the film formation direction) of the film.

The layer B of the laminated film of the present invention preferably has a cold crystallization temperature (Tcc) of 150°C or more and less than 165°C. The cold crystallization temperature refers to the crystallization peak of 2ndrun determined by differential scanning calorimetry to be described later. When the cold crystallization temperature (Tcc) is less than 150°C, the difference between the total haze value before heating of the film (hereinafter sometimes referred to as the initial haze value) and the total haze value of the film after heating the film at 150°C for 180 minutes tends to be large. When used as a transparent conductive base film and a surface protective film for conductive films, transparency is impaired. Specifically, it may become difficult to make ΔHz, which is the difference between the total haze values before and after heating the film at 150° C. for 180 minutes, to 2.0% or less. This is because thermal crystallization proceeds upon heating of the film, and the cyclic oligomers contained in the film exist as a plurality of multimers, and the cyclic oligomers precipitate on the surface of the film, thereby deteriorating the total haze value of the film. In addition, since cyclic oligomers are mostly cyclic trimers, cyclic trimers are mainly described in the present invention. On the other hand, when the cold crystallization temperature (Tcc) is 165° C. or higher, the planarity of the film after heating may be affected. More preferably, it is 150 degreeC or more and 160 degreeC or less.

In the present invention, the cold crystallization temperature (Tcc) is measured by measuring 10 mg of a film sample with an electronic balance, inserting it into an aluminum packing, and using a Seiko Instruments robot DSC-RDC220 thermal differential scanning system, and data analysis is A value obtained by performing the disk session SSCS/5200 manufactured by the same company according to JIS-K-7121 (1987) is shown. As a specific measurement condition, the temperature of the deviation is increased from 25°C to 300°C at 20°C/min, then the deviation is rapidly cooled to 25°C, and then the temperature is raised to 300°C at 20°C/min (2ndRun). Tcc) is determined as the peak temperature of the crystallization peak. When multiple 2ndrun crystallization peaks are observed, the crystallization peak peak temperature indicating the maximum peak area determined by JIS-K-7122 is measured, and this is repeated three times, and the average value is determined as the crystallization peak temperature (Tcc). do. In addition, this time, for the measurement of the inner layer B layer, the surface layer is cut and then measured.

Although it does not specifically limit as a means for making the cold crystallization temperature (Tcc) 150 degreeC or more and less than 165 degreeC, In the present invention, when polyester resin is used as the main component as the thermoplastic resin constituting the layer B, the average of the polyester resin A method of adjusting molecular weight, particle content, and cyclic oligomer content is mentioned as a preferred method. As the average molecular weight, there are number average molecular weight and mass average molecular weight, but as a result of investigation by the present inventors, when the mass average molecular weight is small (if the polymer with a long molecular chain is small), the crystallinity of the film is likely to increase, and the cold crystallization temperature (Tcc) is Conversely, when the mass average molecular weight is large (when there are many polymers having long molecular chains), the crystallinity of the film tends to be lowered, and the cold crystallization temperature (Tcc) tends to increase. However, in the case of performing high-rise polymerization, the mass average molecular weight increases, but the amount of the cyclic trimer decreases. Therefore, although shown below, Tcc tends to decrease easily.

Further, it is considered that the cold crystallization temperature (Tcc) changes also by the content of the particles or cyclic trimers present in the polyester layer of the present invention. For example, when the content of the particles increases, the particles become nuclei and crystallization of the film also proceeds, so that the cold crystallization temperature (Tcc) of the polyester resin decreases. On the other hand, when the particle content decreases, the crystallization of the film is also suppressed, so it is considered that the cold crystallization temperature (Tcc) tends to increase. When the content of the cyclic trimer is small, it is easy to crystallize and the cold crystallization temperature (Tcc) tends to be lowered because less inhibiting the orientation crystallization of the molecular chains of the polymer. On the other hand, it is thought that when the content of the cyclic trimer is large, there are many components that inhibit the orientation determination of the molecular chains of the polymer, so that it is difficult to crystallize and the cold crystallization temperature (Tcc) tends to increase.

For the film, a film containing particles is preferably used for the purpose of the film forming process and the easy activity for post-processing, but the cold crystallization temperature (Tcc) varies depending on the particle content. When the particle content increases, the cold crystallization temperature (Tcc) tends to increase because the particles become nuclei and crystallization is promoted, so that the cold crystallization temperature (Tcc) tends to decrease, and when the particle content decreases, the cold crystallization temperature (Tcc) tends to increase because the nucleus decreases. . In order to increase the haze value after heating and maintain the flatness of the film, it is important to adjust the cold crystallization temperature (Tcc) in consideration of the mass average molecular weight and particle content of the polyester resin. In order to obtain a polyester resin having a predetermined average molecular weight, a polymer described later can be employed, and in particular, it is preferable to perform solid phase polymerization to adjust the molecular chain. The mass average molecular weight of the polyester layer constituting the present invention is 30,000 or more and 50,000 or less, and preferably 40,000 or less.

It is preferable that the content of the cyclic trimer in the layer B of the laminated film of the present invention is 0.01% by mass or more and 1.00% by mass or less. More preferably, it is 0.5 mass% or less. When the content of the cyclic trimer is 1.00% by mass or less, the initial haze value, which is an index of the transparency of the film, is 3.0% or less, and the haze value after heating the film (after heating at 150° C. for 180 minutes) is 3.0% or less. It becomes easier. When the content of the cyclic trimer is less, it becomes difficult for the cyclic trimer to precipitate on the surface of the film during film forming or in the film processing step, and the transparency of the film after heating is also easily maintained. Although it does not specifically limit about the lower limit of content of a cyclic trimer, In this invention, it is 0.01 mass% or more. In the case of less than 0.01% by mass, the time taken for solid phase polymerization to reduce the cyclic trimer becomes a long time, so that the increase in the intrinsic viscosity of the resin increases, the intrinsic viscosity in the case of the laminated film of the present invention also increases, and the load at the time of melt extrusion Becomes large, and may cause thickness variation of the film. When the cyclic trimer exceeds 1.0% by mass, the initial haze value of the film and the haze value after heating may exceed 3.0%, and the film of the present invention is used as a substrate for a transparent electrode, similar to the amount of particles added. As a final transparent electrode, visibility may be lowered, and it may be unsuitable for applications requiring high visibility such as touch panels. It is preferable that the lamination film of the present invention has a haze value of 3.0% or less after heating (after heating at 150° C. for 180 minutes). More preferably, it is 2.5% or less.

It is preferable that the thickness of the laminated film of the present invention is 16 µm or more and 300 µm or less. When the thickness of the film is less than 16 µm or exceeds 300 µm, it may be difficult to produce a stable film. In particular, when it exceeds 300 µm, compatibility with transparency may be difficult. The thickness of the laminated film of the present invention is more preferably 18 µm or more and 260 µm or less, still more preferably 20 µm or more and 250 µm or less, and particularly preferably 20 µm or more and 200 µm or less. In the laminated film of the present invention, when the thickness ratio (A/B) per layer of A layer to layer B is 0.001 to 0.10, transparency and wound suppression properties become good, and thus it is preferable.

It is preferable that the refractive index of the laminated film of this invention is 1.63 or more and 1.69 or less. If the refractive index is less than 1.63, the heat deformability may not be sufficient because crystallization of the film is difficult to proceed, and there may be cases where sufficient mechanical properties cannot be obtained when used with a surface protective film for a conductive film or a transparent conductive base film. have. In addition, when the refractive index exceeds 1.69, film rupture tends to occur during the stretching process during the film production process, and production stability may deteriorate. It is particularly preferable that the refractive index of the laminated film of the present invention is 1.65 or more and 1.67 or less.

In addition, the refractive index here refers to the average value of the refractive index in the film longitudinal direction and the refractive index in the film width direction. The refractive index can be measured with an Abbe refractometer using a sodium D line (wavelength 589 nm) as a light source and using diiodomethane as an intermediate solution. The method of making the refractive index into the above range is not particularly limited, but in general, it can be controlled by adjusting the draw ratio or temperature at the time of stretching.

The laminated film of the present invention is not limited in its film configuration as long as it satisfies the important requirements of the present invention, for example, a laminated film of layer A/B layer, that is, a two-layer laminated film, A layer/B layer/ A laminated film of layer A, that is, a two-type three-layer laminated film, and a laminated film of an A-layer/B-layer/C-layer, that is, a three-type three-layer laminated film. It is preferable that the A layer is in at least one surface layer.

The lamination method of the laminated film of the present invention is not limited, for example, a lamination method by co-extrusion, lamination method by bonding, a method by a combination thereof, etc. are mentioned, but from the viewpoint of transparency and production stability It is preferable to employ a coextrusion method from In the case of a laminated body, different resin configurations may be used for the purpose of imparting different functions to each layer. For example, in the case of a laminated film of layer A/layer B/layer A, that is, a two-type three-layer laminated film, the layer B is composed of homopolyethylene terephthalate from the viewpoint of transparency, and the layer A has particles to impart reactivity. Methods, such as adding to are mentioned.

The biaxially oriented film is generally obtained by biaxially stretching, that is, by stretching a sheet in an unstretched state about 2.5 to 5.0 times each in the sheet length direction and in the width direction, and then performing heat treatment to complete crystal orientation. I can. Further, as the biaxial stretching method, a sequential biaxial stretching method may be used, or a simultaneous biaxial stretching method may be used. Further, after biaxial stretching is performed, a re-stretching method in which stretching is performed in the film longitudinal direction or the film width direction may be performed again.

In addition, the laminated film constituting the present invention has various additives, such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic releasing agents, pigments, dyes, organic or inorganic agents, as long as the effects of the present invention are not impaired. Microparticles, fillers, antistatic agents, nucleating agents, crosslinking agents, and the like may be added.

In the laminated film of the present invention, when the particle size distribution of the inert particles contained in the layer A is measured, and the particle diameter on the horizontal axis and the ratio of the particles on the vertical axis are plotted, at least one maximum value is in the range of 0.8 to 2.0 μm in particle diameter. It is desirable to have. As a method of achieving the above, the use of particles having a number average particle diameter in the range of 0.8 µm to 2.0 µm as particles added to the layer A is exemplified. If the diameter having the maximum value of the inert particles contained in the layer A is too large, it may lead to an increase in internal haze and an increase in surface defects due to particle dropping during film formation. In order not to increase the internal haze, it is preferable to have a maximum value in the range of 0.9 to 1.8 µm in particle diameter, and more preferably in the range of 0.9 to 1.5 µm in particle diameter.

In addition, in the laminated film of the present invention, when the particle size distribution of the inert particles contained in the layer A is measured, and the particle diameter on the horizontal axis and the ratio of the particles on the vertical axis are plotted, one or more maximum values in the range of 0.1 to 0.5 μm in particle diameter. It is preferable to have. As a method of achieving the above, the use of particles having a number average particle diameter in the range of 0.1 µm to 0.5 µm as particles added to the layer A is exemplified. When particles having a number average particle diameter of 0.5 µm or less are contained in the surface layer having the above-described layer thickness, it has been found that it is difficult to form voids even when stretching, so that many particles can be put. By containing a large number of small-diameter particles having a number average particle diameter in the range of 0.1 µm to 0.5 µm, the particles can be dispersed over the entire surface of the film, making it more difficult to cause scratches.

In the laminated film of the present invention, when the particle size distribution of the inert particles contained in the layer A is measured, and the particle diameter on the horizontal axis and the proportion of the particles on the vertical axis are plotted, one or more maximum values in the range of 0.1 to 0.5 μm in particle diameter are obtained. , It is preferable to have at least one maximum value in the range of 0.8 to 2.0 µm in particle diameter. As a method of achieving the above, a combination of particles having a number average particle diameter in the range of 0.1 μm to 0.5 μm and particles having a number average particle diameter in the range of 0.8 μm to 2.0 μm are used as particles added to layer A. I can.

In the laminated film of the present invention, when the particle size distribution of the inert particles contained in the layer A is measured, and the particle diameter on the horizontal axis and the ratio of the particles on the vertical axis are plotted, the largest abundance ratio in the range of 0.1 to 0.5 μm in particle diameter When the maximum value is set to α and the maximum value in the range of 0.8 to 2.0 µm in particle diameter is set to be β, it is preferable that α/β is 1 to 1000. More preferably, it is 10 to 200. By setting α/β in the above-described range, it is possible to suppress the occurrence of scratches on the film surface while maintaining transparency.

In the laminated film of the present invention, the content of the inert particles in the layer A is preferably 0.01 to 0.5% by mass. When the content of the inert particles is 0.01% by mass or more, it becomes easy to suppress a wound during film formation and a wound during surface processing. When the content of the inert particles is 0.05% by mass or less, the effect of suppressing the influence of the increase in internal haze due to containing the inactive particles of the present invention can be sufficiently obtained. More preferably, it is 0.1 to 0.3 mass %.

In addition, in the laminated film of the present invention, the content of the inert particles in the layer B is preferably 0.1% by mass or less. Transparency can be improved by making content of an inert particle into 0.1 mass% or less. More preferably, it is 0.05 mass% or less.

Examples of the inert particles include inorganic particles or organic particles. Examples of the inorganic particles include oxide particles such as silica, alumina, and zirconia, and particles of metal compounds such as calcium carbonate. Examples of the organic particles include crosslinked styrene particles, epoxy particles, polyphenylene sulfide particles, and polyamideimide particles. Among them, particles containing a styrene component (especially crosslinked styrene particles (refractive index: about 1.58)), calcium carbonate particles (refractive index about 1.66) and the like are particularly preferred from the viewpoint of controlling the refractive index and particle diameter. By adding particles close to the refractive index of the substrate, scattering is less likely to occur and internal haze is easily reduced.

In the laminated film of the present invention, when two films are stacked up and down according to the method described in JIS K7125, and the coefficient of dynamic friction is measured using a 200 g load, the value is preferably 0.1 or more and 0.5 or less. When the coefficient of dynamic friction is too large, it is difficult to slip, so there is a tendency that the film is easily damaged when the film is conveyed. More preferably, it is 0.4 or less. On the other hand, when the coefficient of dynamic friction is too small, there is a tendency that winding deviation is likely to occur when wound on a roll. Further, when the dynamic friction coefficient is measured using a 1000 g load, it is preferable that the value is 0.2 or more and 0.5 or less. If the coefficient of dynamic friction at the time of friction under a load of 1000 g is too large, the transportability under vacuum such as sputtering or the like tends to deteriorate. A more preferable range is 0.2 or more and 0.4 or less.

Next, a preferred method for producing the laminated film of the present invention will be described below by taking an A/B/A laminated film using two types of polyester resins as thermoplastic resin A and thermoplastic resin B as an example. Of course, the present invention is not construed as being limited to these examples.

A polyester resin is prepared in the form of pellets. The pellets are dried in hot air or under vacuum as needed and then fed to each extruder. In the extruder, the resin heated and melted to a melting point or higher is equalized by a gear pump or the like, and foreign matter or modified resin is removed through a filter or the like. These resins are molded into a desired shape in a die and then discharged. Then, the multilayered sheet discharged from the die is extruded onto a cooling body such as a casting drum, and cooled and solidified to obtain a casting film. At this time, it is preferable to use an electrode such as a wire shape, a tape shape, a needle shape, a knife shape, etc. to rapidly cool and solidify by intimate contact with a cooling body such as a casting drum by electrostatic force. In addition, a method of rapidly cooling and solidifying by blowing air from a slit-shaped, spot-shaped, or planar-shaped device and making it in close contact with a cooling body such as a casting drum, or by bringing it into close contact with a cooling body with a nip roll to rapidly cool and solidify is also preferable.

Further, in the case of producing a laminated film made of a plurality of polyester resins, a plurality of resins are fed out from different flow paths using two or more extruders, and are joined by pinols. The pinol design is composed of A/B/A, and the discharge amount is adjusted so that the thickness of the surface layer becomes the desired thickness. In this way, the molten multilayer laminate formed in the desired layer structure is extruded from a T-shaped cage into a sheet shape, wound around a mirror casting drum having a surface temperature of 10 to 60°C using an electrostatically applied cast method, cooled and solidified, and undrawn PET Produce a film. This unstretched film is stretched 2.5 to 5.0 times in the longitudinal direction (also referred to as the "longitudinal direction" to indicate the advancing direction of the film) between rolls heated at 70 to 100°C. Subsequently, the film is held by a clip, guided to the preheating zone, heated to a temperature of 75 to 95°C, and then continuously in a heating zone at 90 to 115°C in the transverse direction (orthogonal to the advancing direction of the film). It is stretched 3.0 to 5.0 times in a direction (also referred to as "width direction"), and then heat treated in a heating zone at 200 to 240°C for 5 to 60 seconds, and the crystal orientation is changed through a cooling zone at 100 to 200°C. A finished polyester film is obtained. Further, during the heat treatment, a relaxation treatment of 3 to 12% may be performed as necessary. The biaxial stretching may be either sequential stretching or simultaneous biaxial stretching, and may be re-stretched in any one of vertical and transverse stretching after longitudinal and transverse stretching. After cutting the end of the obtained biaxially oriented laminated polyester film, it is wound up to form an intermediate product, and then cut to a desired width using a slitter, and then wound around a cylindrical core to obtain a polyester film roll of the desired length. have. Further, in order to improve the winding posture during winding, an embossing treatment may be applied to both ends of the film.

In the laminated film of the present invention, a coating layer may be formed on one side of the film or on both sides of the film. Further, the coating layer may be a plurality of coating layers of two or more layers on one side, or when forming the coating layer on both sides, another composition may be applied on one side and the other side.

Example

Hereinafter, the configuration and effects of the present invention will be described in more detail by examples. In addition, the present invention is not limited to the following examples. Prior to the description of each example, methods for measuring various physical properties are described.

(1) thickness

The film was cut into A4 size, using a dial gauge ("No2110S-10" manufactured by Mitsutoyo), arbitrary 20 points were measured, and the average value was taken as the thickness (µm).

(2) Overall haze, internal haze

A 5 cm x 5 cm film was used as a sample, and total haze before and after heating was measured with a haze meter according to JIS-K-7105 (1985), respectively. ("HZ-V3" made by Suga Skenki) Each of the three measurement samples was prepared, the average was taken as the haze value, and ΔHz was calculated from the difference. In addition, the internal haze was measured in a state in which a sample was placed in a quartz cell and immersed in a 1,2,3,4 tetrahydronaphthalenetetrarin solution. In this case, calibration was performed only with solution and quartz cell.

(3) Cold crystallization temperature (Tcc)

10 mg of the film was weighed with an electronic balance, placed in an aluminum packing, and measured using a Seiko Instruments robot DSC-RDC220 thermal differential scanning system, and data analysis was performed using the company's disk session SSC/5200, and JIS -According to K-7121 (1987). The temperature was raised from 25°C to 300°C at 20°C/min. After that, it was rapidly cooled to 25°C, and the temperature was raised again to 300°C at 20°C/min (2ndRun). The midpoint glass transition temperature was determined as the glass transition temperature (Tg), and the peak temperature of the crystallization peak was determined as the crystallization peak temperature (Tcc).

When a plurality of crystallization peaks of 2ndrun are observed, the crystallization peak peak temperature indicating the maximum peak area determined by JIS-K-7122 is taken as the temperature.

(4) Content of cyclic trimer

20 mg of the film piece before heating was taken as a sample, dissolved in OCP (o-chlorophenol) for 30 minutes at 150°C, and cooled at room temperature. After that, 1,4-diphenylbenzene was added as an internal standard, and then 2 ml of methanol was added to separate the polymer with a high-speed centrifuge, and the liquid layer was subjected to a high-performance liquid chromatography ("LC-10ADvp" manufactured by Shimadzu Seisakusho). Measured.

(5) Surface roughness

According to JIS B0601-1994, it measured using a three-dimensional fine surface shape measuring instrument (ET-4000A manufactured by Kosaka Seisakusho), and according to JIS B0601-1994, according to the profile curve of the obtained film surface, center plane average roughness (SRa), 10-point average roughness ( SRz) was obtained. Measurement conditions are as follows.

Needle diameter 2 (㎛R)

Needle pressure 10(mg)

Measurement length 500(㎛)

Vertical magnification 20000 (times)

CUT OFF low range: 0.25mm, high range: R+W

Measurement speed 100 (㎛/s)

Measurement interval 5(㎛)

81 records

Hysteresis width ±0(nm)

Reference area 0.2(mm2).

(6) particle diameter measurement

The surface of the polyester film was observed and photographed at a magnification of 10,000 times using a field emission scanning electron microscope JSM-6700F (manufactured by Nippon Denshi Corporation). From these observation photographs, the particle size distribution of the particles present on the film surface was determined using the image analysis software Image-Pro Plus (Nippon Roper Co., Ltd.). The surface photograph is selected from another arbitrary measurement field, and the diameter (circular equivalent diameter) of 1000 or more particles randomly selected from the photograph is measured, and the horizontal axis is the particle diameter, and the vertical axis is the volume-based particle size plotted as the presence ratio of particles. The distribution was obtained. In the volume-based particle size distribution, the particle diameter in charge of the horizontal axis is determined by the rank at every 10 nm interval with 0 nm as the focus, and the abundance ratio of the particles in charge of the vertical axis is calculated using the formula ``existence ratio = detection particles having a corresponding particle diameter. The total volume of / total volume of all detected particles". The particle diameter of the peak top showing the maximum was read from the chart of the presence ratio of the particles obtained as described above.

(7) Measurement of wounds and defects

In the dark room, a three-wavelength fluorescent lamp was placed on the side of the examiner, and at the time of 1 m inspection, a wound that could be visually confirmed was sampled. The sampled wound was observed with a laser microscope, and the height difference was measured. The difference in elevation was obtained as the difference between the highest and lowest points of the wound. The wounds in the table are indicated as follows. There are ranks A to D, and there are severe wounds in the order of A<B<C<D.

A: It is a wound with a height difference of less than 0.5㎛, and the length is more than 0mm and less than 2mm

B: It is a wound with a height difference of less than 0.5㎛, and the length is more than 2mm

C: It is a wound with a height difference of 0.5㎛ or more, and the length is more than 0mm and less than 0.3mm

D: A wound with a height difference of 0.5 µm or more, and a length of 0.3 mm or more.

(8) Measurement of dynamic friction on the film surface

Two sheets cut into 80mm×200mm are overlapped so that the A sides are in contact, and a weight is placed thereon, and the upper sheet is stretched horizontally at 100mm/min using a universal testing machine (Shimazu Seisakusho EZ-S). And measured the friction force applied at that time. According to the method described in JIS K7125, the coefficient of dynamic friction was measured when a 200 g weight and a 1000 g weight were used. In addition, the measurement under a load of 1000 g assumes slippage in a sputtering process (conveyance in a vacuum state).

(9) Thickness of the film surface layer

The surface thickness of the film is taken by making a small piece cut in the vertical direction to the surface of the film, and then magnifying the cross section to 10000 times using a field emission scanning electron microscope JSM-6700F (manufactured by Nippon Denshi Co., Ltd.). , The location farthest from the surface was taken as the film thickness.

(10) Measurement of thickness deviation

Ten points of the polyester film were measured in the longitudinal direction or the width direction, and the average value was made into the center value A. Further, the value obtained by subtracting the minimum value from the maximum value was taken as the thickness deviation B, and the ratio of the thickness deviation to the center value was calculated. That is, the thickness variation (%) of the film was set to 100×B/A, and the average of the longitudinal direction and the width direction was evaluated below.

[Evaluation of thickness deviation]

A: Thickness deviation is less than 3.0%

B: Thickness deviation exceeds 3.0% and is 5.0% or less

C: Thickness deviation exceeds 5.0%.

(11) Flatness evaluation (heat deformation resistance)

After the film cut into 20 cm x 20 cm was placed on the punching metal and held for 10 minutes in a non-tensioned state in an oven at a temperature of 150° C., the film sample was cooled at room temperature for 10 minutes, and the film surface The state of the reflective image of the fluorescent lamp illuminated by was observed. The punched metal was evaluated using the following two types, and the heat distortion resistance was evaluated according to the following criteria.

Punching metal A: Punching metal SUS304 made by Okutani Kanami Seisakusho

Embossing 1.5t×D4.5×P7.5 60° zigzag

Punching metal B: Punching metal SUS304 made by Okutani Kanami Seisakusho

Embossing 2t×D7/H1.3×P10 60° zigzag

[Evaluation criteria for heat distortion resistance]

A: In either case of punching metal A and punching metal B, no deformation was observed on the reflection of the fluorescent lamp.

B: In either case of punching metal A and punching metal B, there was a deformation|transformation on the reflection of a fluorescent lamp by the embossing pitch of the punching metal on a part of the film surface.

C: In either of the punched metal A and the punched metal B, there was a deformation on the reflection of the fluorescent lamp on the entire surface of the film due to the embossing pitch of the punched metal.

[Polyester resin used]

(PET-A)

The esterification reaction product, which is the reaction product of terephthalic acid and ethylene glycol, is stored in a molten state at 255°C in advance, and the terephthalic acid and ethylene glycol are in the form of a slurry so that the molar ratio of ethylene glycol to terephthalic acid is 1.15, while maintaining the temperature of the esterification reaction tank. It quantitatively supplied and the esterification reaction was performed, distilling water out, and the esterification reaction product was obtained. The obtained esterification reaction product was transferred to a polymerization reactor, and an ethylene glycol solution containing phosphoric acid, an ethylene glycol solution containing magnesium acetate tetrahydrate, an ethylene glycol solution containing antimony trioxide, and an ethylene glycol solution containing potassium hydroxide, respectively. To the resulting polyester resin, an alkali metal element, an alkaline earth metal element, and a phosphorus element were added so that the M/P was 2.8 and 60 ppm as an antimony element, and then the inside of the polymerization reactor was gradually reduced to a pressure of 0.13 kPa or less in 30 minutes. At the same time, the temperature was gradually increased to 280°C, and polymerization reaction was performed. After that, the polycondensation reaction tank was returned to normal pressure with nitrogen gas, discharged from the cage into a strand shape in cold water, extruded and pelletized into a columnar shape with a cutter, pre-crystallized by a surface crystallization apparatus, and a liquid polyester was obtained. . Using the liquid polyester obtained here, solid-phase polymerization was performed at a temperature of 215°C for 20 hours under a reduced pressure of 0.13 KPa by a rotary vacuum drying apparatus to obtain a polyester resin (PET-A). The intrinsic viscosity of the obtained polyester resin (PET-A) was 0.63, the cyclic trimer content was 0.44 mass%, and Tg was 80°C.

(PET-B)

In the production process of the polyester resin (PET-A), the polyester resin (PET-B) is carried out in the same manner as PET-A, except that solid-phase polymerization after obtaining the liquid polyester is performed using a continuous vacuum drying apparatus. ). The intrinsic viscosity of the obtained polyester resin (PET-B) was 0.73, the cyclic trimer content was 0.40 mass%, and Tg was 80°C.

(PET-C)

A polyester resin (PET-C) was obtained by a method similar to that of a polyester resin (PET-A) except that the solid phase polymerization was not performed and the intrinsic viscosity was changed. The obtained polyester resin (PET-C) had an intrinsic viscosity of 0.70, a cyclic trimer content of 1.07 mass%, and a Tg of 80°C.

(PET-D)

PET-C and calcium carbonate particles having an average particle diameter of 1.0 µm were mixed, and the mixture was melt-kneaded to obtain a master pellet. Here, the amount of particles was set to 1% by mass.

(PET-E)

PET-C and crosslinked polystyrene particles having an average particle diameter of 0.3 µm were mixed, and the mixture was melt-kneaded to obtain a master pellet. Here, the amount of particles was set to 2% by mass.

(PET-F)

PET-C and silica particles having an average particle diameter of 2.0 µm were mixed, and the mixture thereof was melt-kneaded to obtain a master pellet. Here, the amount of particles was set to 1% by mass.

(PET-G)

PET-C and crosslinked polystyrene particles having an average particle diameter of 0.8 µm were mixed, and the mixture was melt-kneaded to obtain a master pellet. Here, the amount of particles was set to 1% by mass.

(PET-H):

Except changing the addition amount of potassium hydroxide, magnesium acetate, and phosphoric acid so that M/P might become 1.5, it carried out by the method similar to PET-A, and obtained the polyester resin (PET-G). The intrinsic viscosity of the polyester resin (PET-H) was 0.62 dl/g, the cyclic trimer content was 0.43 wt%, and the glass transition temperature Tg was 80°C.

(PET-I):

A polyester resin (PET-I) was obtained by performing the same method as PET-A except for changing the magnesium acetate tetrahydrate and the addition product of phosphoric acid so that M/P becomes 2.0. The intrinsic viscosity of the polyester resin (PET-I) was 0.63 dl/g, the cyclic trimer content was 0.43% by weight, and the glass transition temperature Tg was 80°C.

(PET-J):

A polyester resin (PET-I) was obtained in the same manner as PET-A except for changing the magnesium acetate tetrahydrate and the addition product of phosphoric acid so that M/P becomes 5.4. The intrinsic viscosity of the polyester resin (PET-J) was 0.65 dl/g, the cyclic trimer content was 0.43% by weight, and the glass transition temperature Tg was 80°C.

(PET-K):

A polyester resin (PET-I) was obtained in the same manner as PET-A except for changing the magnesium acetate tetrahydrate and the addition product of phosphoric acid so that the M/P became 6.0. The intrinsic viscosity of the polyester resin (PET-K) was 0.67 dl/g, the cyclic trimer content was 0.43% by weight, and the glass transition temperature Tg was 80°C.

(PET-L):

PET-A and silica particles having an average particle diameter of 0.5 µm were mixed, and the mixture was melt-kneaded to obtain a master pellet. Here, the amount of particles was set to 0.5% by mass.

[Application liquid used]

(Application agent A)

In a nitrogen gas atmosphere, 40 mole parts of 2,6-naphthalenedicarboxylic acid as a dicarboxylic acid component, 50 mole parts of terephthalic acid, 10 mole parts of sodium 5-sulfoisophthalate, 95 mole parts of ethylene glycol as a glycol component, 5 moles of diethylene glycol Part was put into the transesterification reactor, 100 parts by mass of tetrabutyl titanate (catalyst) was added to the total dicarboxylic acid component 100 parts by mass, and esterification was carried out at 160 to 240°C for 5 hours, and then the distillate (溜出液) was removed. Thereafter, 5 mol parts of trimellitic acid and 100 parts by mass of tetrabutyl titanate were further added with respect to 1 million parts by mass of the total dicarboxylic acid, and the distillate was removed at 240° C. until the reactants became transparent, and then at 220 to 280° C. Polycondensation reaction was carried out under reduced pressure to obtain polyester (A). After that, 100 parts by mass of polyester (A) and 50 parts by mass of a melamine-based crosslinking agent ("Nikarak" (registered trademark) MW12LF manufactured by Sanwa Chemical Co., Ltd.: 70% by mass of active ingredient and 17% by mass of isopropyl alcohol) 5.0 parts by mass of an active ingredient obtained by mixing 1.5 parts by mass of parts (in terms of active ingredient) and colloidal silica (particle diameter of 140 nm), 3.0 parts by mass of ethylene glycol mono-n-butyl ether, and 92.0 parts by mass of water, followed by application Liquid-1 was obtained.

(Application agent B)

In a stainless steel reaction vessel, 75 parts by mass of methyl methacrylate, 20 parts by mass of hydroxyethyl methacrylate, urethane acrylate oligomer (manufactured by Negami Kogyo Co., Ltd., Atresin (registered trademark) UN-3320HA, acryloyl) 5 parts by mass of the number of groups 6) was added, and 2 parts by mass of sodium dodecylbenzenesulfonate was added as an emulsifier, followed by stirring to prepare a mixed solution 1. Next, a reaction apparatus equipped with a stirrer, a reflux cooling tube, a thermometer, and a dropping lot was prepared. 60 parts by mass of the mixed solution 1, 200 parts by mass of isopropyl alcohol, and 5 parts by mass of potassium persulfate as a polymerization initiator were put into a reaction apparatus, and heated at 60°C to prepare a mixed solution 2. The mixed solution 2 was kept heated at 60°C for 20 minutes. Next, a mixed solution 3 comprising 40 parts by mass of the mixed solution 1, 50 parts by mass of isopropyl alcohol, and 5 parts by mass of potassium persulfate was prepared. Then, using the dropping lot, the mixed solution 3 was dripped into the mixed solution 2 over 2 hours, and the mixed solution 4 was prepared. After that, the mixed solution 4 was kept heated at 60°C for 2 hours. After cooling the obtained liquid mixture 4 to 50°C or less, it was transferred to a container equipped with a stirrer and a decompression facility. To it, 60 parts by mass of 25% aqueous ammonia and 900 parts by mass of pure water were added, and isopropyl alcohol and unreacted monomer were recovered under reduced pressure while heating to 60° C. to obtain a resin (B) dispersed in pure water. After that, 100 parts by mass of the resin B and 50 parts by mass of a melamine-based crosslinking agent ("Nikarak" (registered trademark) manufactured by Sanwa Chemical Co., Ltd. MW12LF: 70% by mass of the active ingredient and 17% by mass of isopropyl alcohol) are contained (effective Component conversion), 2 parts by mass of silica particles having a number average particle diameter of 300 nm (SEHOSTER (registered trademark) KE-W30 manufactured by Nippon Shokubai Co., Ltd.), and coating properties of the resin composition on the polyester film In order to improve, a fluorine-based surfactant (GOO Chemical Co., Ltd. Plus Coat (registered trademark) RY-2) was added so that the content of the coating solution containing the resin composition was 0.06 parts by mass to obtain coating solution-2. .

[Preparation of polyester film]

(Example 1)

The thermoplastic resin A was mixed so as to have a mass ratio of PET-A:PET-D:PET-E=89:10:1, and PET-A was used as the thermoplastic resin B.

The prepared thermoplastic resins A and B were each dried in a vacuum at 160°C for 4 hours, and then fed to an extruder to perform melt extrusion at 285°C. It is a filter with an average eye size of 5㎛ by sintering and compressing stainless steel fibers, and then filtering the stainless steel powder with an average eye size of 14㎛ through a sintered filter, and weighing the A/B mass ratio to 2:48 by a gear pump In the meantime, after joining as A/B/A with pinol, it was extruded from a T-shape to the shape of a sheet, wound around a mirror casting drum having a surface temperature of 20°C using an electrostatic casting method, and cooled and solidified. Further, at this time, cold air at a temperature of 10°C was sprayed onto the film at a wind speed of 20 m/s from a slit nozzle having a gap of 2 mm provided in 8 steps in the longitudinal direction from the opposite surface of the casting drum, and cooling was performed from both sides.

After preheating this unstretched film to 70°C with a preheating roll, it is heated up to 90°C using a radiation heater from the vertical direction, and stretched 3.1 times in the longitudinal direction using the difference in circumferential speed between the rolls, and then cooled to 25°C with a cooling roll And it was set as a uniaxial orientation (uniaxial stretching) film.

The film was gripped with a clip, guided to an oven, and heated by hot air having a temperature of 110°C and a wind speed of 20 m/min. Subsequently, it was guided to the extending|stretching process continuously, and it extended|stretched 3.7 times in the width direction, heating with a hot air of a temperature of 100 degreeC and a wind speed of 15 m/min. The obtained biaxially oriented film was continuously heat-treated for 15 seconds with hot air at a temperature of 230°C and a wind speed of 20 m/min, and then a 5% relaxation treatment was performed in the width direction while cooling from 230°C to 120°C. It cooled to 50 degreeC. Subsequently, after removing both ends in the width direction, it was wound up and a laminated film having a thickness of 50 µm was obtained.

The laminated film obtained here had few wounds and defects, and was excellent in transparency. Moreover, there is little haze-up after heating, and it can be used suitably as a surface protective film use for conductive films and a transparent conductive base film use.

(Example 2)

It was carried out in the same manner as in Example 1 except that the total discharge amount was increased and the discharge amount of the extruder was changed to obtain a 125 µm film, and the mass ratio was set to A:B=2:123. Even if the film became thick, the thickness of the surface layer did not change, so the internal haze and SRz hardly changed.

(Examples 3 and 4, Comparative Example 1)

It was carried out in the same manner as in Example 1, except that the A:B mass ratio was set to 3:47, 4:46, and 5:45 by changing the rotation speed of the gear pump, and the thickness of the layer A was increased. As a result, even if the surface layer thickness was made thicker than 1 μm, the SRz hardly changed, but it was found that the internal haze increased. It is thought that this is because coarse particles are contained inside the layer, so that voids tend to be generated. On the other hand, as the number of particles contained in the layer increased, the surface scratches tended to decrease.

(Example 5)

The mixing ratio of the thermoplastic resin A was changed to PET-A:PET-D:PET-E=78:20:2, the rotation speed of the gear pump was changed, and the mass ratio of A:B was changed to 1:49. Except that, it carried out similarly to Example 1, and performed. As a result, it was found that it became a film in which both transparency and transportability in a vacuum state were achieved.

(Comparative Example 2)

It carried out in the same manner as in Example 1 except that the thermoplastic resin A was changed to PET-A:PET-D:PET-E=70:10:20. It was found that the internal haze increased as the particle concentration of the surface layer increased.

(Example 6)

It carried out similarly to Example 1 except having changed to PET-A:PET-D=95:5 as thermoplastic resin A. Since only particles having a large particle diameter were contained, the sliding property was good, but because the particles were sparse, the resistance to scratches was slightly low.

(Comparative Example 3)

It carried out similarly to Example 1 except having changed to PET-A:PET-E=95:5 as thermoplastic resin A. Since only particles having a small particle diameter, the sliding properties were poor, and the transportability under vacuum was poor.

(Comparative Example 4)

As thermoplastic resin A, it carried out similarly to Example 1 except having changed the mass ratio of PET-A:PET-F=95:5 and A:B to 3:47. Even if the thickness of the layer A was 1.5 µm, when particles having a large particle diameter were put, it was found that the internal haze increases.

(Example 7)

It carried out in the same manner as in Example 1 except that the thermoplastic resin A was changed to PET-A:PET-G:PET-E=94.5:3:2.5. As the coarse particles became smaller, Rz decreased, but it was found that the haze became smaller and a film having more excellent visibility was obtained.

(Example 8)

It carried out similarly to Example 1 except having used PET-B as resin B. As a result, although the surface roughness and haze did not change, it became smaller than the haze example 1 after a heat resistance test, and it became a film with higher heat resistance.

(Example 9)

It carried out similarly to Example 1 except having used PET-C as resin B. As a result, the surface roughness and haze did not change, but the haze after the heat resistance test increased.

(Comparative Example 5)

By varying the number of rotations of the gear pump, the mass ratio of A:B is set to 2:123, respectively, except that PET-C:PET-D:PET-E = 89:10:1 as thermoplastic resin A. It carried out similarly to Example 1. It was found that the amount of haze-up during heating was increased by using a resin having a large amount of oligomer in the surface layer, and the total thickness was increased.

(Comparative Example 6)

It was carried out in the same manner as in Example 1 except that the mass ratio of A:B was respectively 0.5:49.5 by changing the rotation speed of the gear pump. As a result, it became a film with many defects. When the surface of the wound was observed with a laser microscope, traces of particles were observed.

(Example 10)

The mixing ratio of the thermoplastic resin A was changed to PET-A:PET-D:PET-E=78:20:2, the rotation speed of the gear pump was changed, and the mass ratio of A:B was changed to 3:47. Except that, it carried out similarly to Example 1, and performed. As a result, although the haze was slightly high, it was found that the transportability under vacuum was good and a film with few scratches was obtained.

(Example 11)

It carried out in the same manner as in Example 1 except that the mixing ratio of the thermoplastic resin A was changed to PET-A:PET-D:PET-E=85:10:5, and the rotation speed of the gear pump was changed. As a result, it turned out that it became a film which made transparency and transportability under vacuum compatible.

(Example 12)

In Example 1, it was carried out under the same conditions as in Example 1 except that the resin of the B layer was changed to PET-H. Compared with Example 1, a transparent film and excellent heat resistance were obtained. However, the castability at the time of film formation was poor, and a film having poor thickness variation in the width direction was obtained.

(Example 13)

In Example 1, it was carried out under the same conditions as in Example 1 except that the resin of the B layer was changed to PET-I. Compared with Example 1, a transparent film and excellent heat resistance were obtained. However, the castability at the time of film formation was poor, and although it was improved from Example 14, it became a film with poor thickness variation in the width direction.

(Example 14)

In Example 1, it was carried out under the same conditions as in Example 1 except that the resin of the B layer was changed to PET-J. Compared with Example 1, since there were many catalyst residues in PET, it became a film with large internal haze. A film that was transparent and excellent in heat resistance was obtained.

(Comparative Example 7)

In Example 1, it was carried out under the same conditions as in Example 1 except that the resin of the B layer was changed to PET-K. Compared with Example 1, since there were many catalyst residues in PET, the internal haze further increased, and the heat-resistant haze also worsened.

(Comparative Example 8)

In Example 1, it was carried out under the same conditions as in Example 1 except that the resin of the B layer was changed to PET-L. Compared with Example 1, since particles entered the inner layer, a film having a high inner haze was obtained. Further, since Tcc was 149°C, crystallinity was high, and haze-up after heating became large.

(Reference Example 1)

In Example 1, it carried out under the same conditions as Example 1 except having coated the coating agent A. For coating, after obtaining a uniaxially stretched film, corona discharge treatment was performed on both sides of the film in air, the surface tension of the film was 55 mN/m, and coating material A was used on both sides of the uniaxially stretched film using a bar coater. And applied. In addition, a metal ring wire bar having a diameter of 13 mm and a wire diameter of 0.1 mm (#4) was used.

The obtained film had high transparency, but the heat resistance was slightly lower than that of the coated formulation.

(Reference Example 2)

In Example 12, it carried out under the same conditions as Example 1 except having changed the coating agent to coating agent B. As a result, a film having an acrylic layer having a coating film thickness of 100 nm was obtained. The obtained film had high transparency and the heat resistance was the best. On the other hand, as the film thickness was thicker, the surface roughness became small, and the occurrence of scratches was slightly worse.

(Comparative Reference Example 1)

It carried out in the same manner as in Example 1 except that only PET-A was used as the thermoplastic resin A and was coated with the coating agent A in order to impart this activity. For coating, after obtaining a uniaxially stretched film, corona discharge treatment was performed on both sides of the film in air, the surface tension of the film was 55 mN/m, and coating material A was used on both sides of the uniaxially stretched film using a bar coater. And applied. In addition, a metal ring wire bar having a diameter of 13 mm and a wire diameter of 0.1 mm (#4) was used. As a result, although it was the film with the highest transparency, it turned out that it became a film with many wounds.

Claims (12)

It is a laminated film having a layer containing inert particles (layer A) containing as a main component a thermoplastic resin A having a thickness of 0.5 μm or more and 2.0 μm or less on at least one side of a layer (layer B) containing thermoplastic resin B as a main component, and the laminated A biaxially oriented laminated film in which the film satisfies the following requirements (1) to (3).
(1) Internal haze of 0.5% or less.
(2) A 10-point average roughness (SRz) of the surface of the layer A on the surface opposite to the surface of the layer A in contact with the layer B is 250 nm or more.
(3) The amount of change in total haze before and after treatment at 150°C for 30 minutes is 2.0% or less. The method of claim 1,
A biaxially oriented laminated film having a total haze change of 2.0% or less before and after treatment at 150° C. for 180 minutes. The method according to claim 1 or 2,
A biaxially oriented laminated film having a total haze of 1.0% or more and less than 3.0%. The method according to any one of claims 1 to 3,
A biaxially oriented laminated film having a cold crystallization temperature (Tcc) of layer B of 150°C or more and less than 165°C. The method according to any one of claims 1 to 4,
A biaxially oriented laminated film in which the content of the cyclic trimer in the layer B is 0.01% by mass or more and 1.00% by mass or less. The method according to any one of claims 1 to 5,
When the particle size distribution of the inert particles contained in the layer A is measured and the particle diameter on the horizontal axis and the proportion of particles on the vertical axis are plotted, a biaxially oriented laminated film having at least one maximum value in the range of 0.8 to 2.0 μm in particle diameter . The method according to any one of claims 1 to 6,
When the particle size distribution of the inert particles contained in the layer A is measured and the particle diameter on the horizontal axis and the proportion of particles on the vertical axis are plotted, biaxially oriented lamination having at least one maximum value in the range of 0.1 μm to 0.5 μm in particle diameter film. The method according to any one of claims 1 to 7,
The biaxially oriented laminated film in which the inert particles include calcium carbonate particles. The method according to any one of claims 1 to 7,
The inert particles are biaxially oriented laminated film comprising organic particles containing a styrene component. The method according to any one of claims 1 to 9,
A biaxially oriented laminated film in which the difference between the total haze and the internal haze is 0.8% or more. The method according to any one of claims 1 to 10,
A biaxially oriented laminated film in which layer A is on at least one surface layer. The method according to any one of claims 1 to 11,
A biaxially oriented laminated film in which the inert particles contained in the layer A are 0.01 to 0.5% by mass.