JP7264295B2 - LAMINATED WHITE POLYESTER FILM AND RECORDING MATERIAL - Google Patents

Description

The present invention relates to laminated white polyester films. More specifically, it relates to a laminated white polyester film suitable as a recording material, which is an information printing medium replacing paper such as copying paper.

Currently, with the high performance of copiers and printers, these machines are used for printing and copying documents, as well as for printing photos and videos, issuing forms and slips, etc. Paper materials for various purposes and forms is used for the issuance of As a result, the amount of copier paper and printer paper consumed in companies and homes is increasing.

Since the mass consumption of paper, including copy paper and printer paper, is undesirable from the perspective of curbing deforestation, recycled paper is now being used by collecting used paper and disaggregating it into recycled pulp at paper mills. .
The main raw material for recycled paper is used paper that has been collected. Even if the utilization rate of paper rises, wood resources will still be consumed, and the use of recycled paper will not be a drastic solution for protecting the forest environment.
In addition, the quality of recycled paper is still inferior to that of high-quality paper, and when copying paper made from recycled paper is used, the whiteness of the paper decreases and the color becomes grayish. image quality tends to deteriorate.
In addition, recycled paper is expensive to manufacture and tends to be more expensive than wood-free paper.

Instead of such recycled paper, there has been proposed a paper that can be reused once by peeling and removing an image formed on the surface of the paper by an electrophotographic method such as a copying machine. For example, a paper mainly composed of cellulose fibers is used as a base, and a layer containing a polymer selected from polyvinyl alcohol, starch, carboxymethyl cellulose, polyvinyl acetate, and acrylic resin is provided on the image recording surface of the base. A reusable recording material is disclosed in which a toner-repellent layer containing a compound having a linear or branched alkyl group or alkenyl group is provided on a layer containing the compound (see, for example, Patent Document 1).
However, such a recording material has a thin polymer layer in order to reduce the cost of the polymer layer, and since it requires paper as a base, it does not completely eliminate the use of wood resources. It's not a solution for protection.

Therefore, as a material that completely replaces paper, synthetic paper made of plastic is being studied. For example, synthetic paper made of polypropylene is used for daily necessities. (See Patent Document 2, for example)

JP 2005-234162 A JP-A-10-204196

However, the synthetic paper described in Patent Document 2 is vulnerable to heat, and when used in copiers and printers that fix toner at relatively high temperatures, the synthetic paper melts and wrinkles in the copier, causing paper jams. could have occurred.

The present invention has been made in view of the above-mentioned circumstances, and the problem to be solved is that it can be used as a recording material that is an information printing medium that replaces paper such as copying paper, and is extremely cost-effective. To provide a polyester film.

The gist of the present invention resides in a laminated white polyester film characterized by containing a polymer incompatible with polyester in a surface layer and having an arithmetic mean roughness (SRa) of 950 nm or less.

The laminated white polyester film of the present invention contains a polymer incompatible with polyester in the surface layer, and the arithmetic average roughness (SRa) of the surface layer is 950 nm or less, so that information that replaces paper such as copy paper It is a plastic film that can be used as a recording material, which is a printing medium, and is extremely cost-effective. Furthermore, the laminated white film of the present invention can suitably transfer a toner image. That is, the toner image can be suitably transferred by a method such as an electrophotographic method, a thermal transfer method, or an ink jet method for transferring the toner image onto the recording material. In addition, after being used as a recording material, characters and images formed on the surface by toner and/or image forming substances can be easily peeled off.

The present invention will now be described in more detail.

<This laminated white polyester film>
A laminated white polyester film (referred to as "this laminated white polyester film") as an example of a mode for carrying out the present invention is a laminated film having at least two or more layers containing polyester as a main resin. At least the surface layer is characterized by containing a polyester and a polymer incompatible with the polyester.

<Surface layer>
The surface layer of this laminated white polyester film preferably contains at least polyester as the main component resin and a polymer incompatible with polyester.
Here, the "main component resin" means a resin having the highest content ratio among the resin components constituting the surface layer. It can be assumed that the main component resin accounts for 30% by mass or more, especially 50% by mass or more, and especially 80% by mass or more (including 100% by mass) of the resin components constituting the surface layer.

(polyester)
The polyester constituting the present laminated white polyester film refers to one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol.
Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, etc. Aliphatic glycols include ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1, 4-cyclohexanedimethanol and the like can be mentioned.

Typical polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalene dicarboxylate (PEN), polybutylene terephthalate and the like.

The polyester may be a homopolymer that is not copolymerized, and 20 mol % or less of the dicarboxylic acid component is a dicarboxylic acid component other than the main component, and/or 20 mol % or less of the diol component is other than the main component. It may be a copolyester such as a diol component of. A mixture thereof may also be used.

Polyester can be obtained by a conventionally known method, for example, a method of directly obtaining a polyester by reacting a dicarboxylic acid and a diol, or a method of reacting a lower alkyl ester of a dicarboxylic acid and a diol with a conventionally known transesterification catalyst, followed by addition of a polymerization catalyst. It can be obtained by a method of performing a polymerization reaction below. As the polymerization catalyst, known catalysts such as antimony compounds, germanium compounds, titanium compounds and aluminum compounds can be used.

The lamination structure of the laminated white polyester film is not particularly limited, and may be two layers, three layers, four layers, or more layers as long as the gist of the present invention is not exceeded. Among them, a three-layer structure (surface layer/intermediate layer/surface layer) consisting of both surface layers and an intermediate layer is preferable.
In addition, when the laminated structure is two layers, it means that it is composed of two surface layers. For example, it may be formed by layers.

(Polymer incompatible with polyester)
By incorporating a polymer incompatible with polyester into the present laminated white polyester film, the polyester film stretched at least uniaxially can contain a myriad of extremely fine cavities. Due to the microscopic cavities, the laminated white polyester film not only scatters light and provides white opacity, but also reduces the apparent density of the laminated white polyester film.
Above all, by containing a polymer incompatible with polyester in the surface layer of this laminated white polyester film, when used as a recording material for copying paper or printer paper, toner printed or printed on the surface of this laminated white polyester film The image forming material containing the thermoplastic resin can be easily peeled off. Further, in order to ensure sufficient hiding power and weight reduction, the intermediate layer may contain a polymer incompatible with polyester, if necessary.

As the polymer incompatible with polyester, conventionally known polymers can be used. Examples thereof include polyolefin, polystyrene, polyacryl, polycarbonate, etc. Among them, polyolefin and polystyrene are preferable, and polyolefin is more preferable. Further, among polyolefins, polypropylene, polyethylene, poly-4-methylpentene-1, amorphous polyolefins and the like can be mentioned, and among them, polypropylene is more preferable in consideration of cavity formation and ease of film formation.

A polymer incompatible with the above-described polyester is incorporated into the film, extruded into a sheet, and then stretched in at least one direction to form ultrafine closed cavities inside the film. In this case, surfactants, inert particles, fluorescent whitening agents, etc. may be blended in order to make the cavities extremely fine, concealing properties, and increasing whiteness.

In the present laminated white polyester film, when polypropylene is used as a polymer incompatible with polyester, the content of propylene units in the polypropylene polymer is preferably 80 mol% or more, more preferably 90 mol% or more, and more preferably It is in the range of 95 mol % or more. For example, by reducing the content of the copolymer obtained by copolymerizing units other than propylene units and using it within the above range, it is possible to sufficiently generate microvoids.

When polypropylene is used as a polymer incompatible with polyester, the melt flow index of polypropylene under conditions of a temperature of 230° C. and a load of 2.16 kg (21.2 N) is usually 0.5 ml/10 minutes or more as a lower limit, The range is preferably 1 ml/10 minutes or more, more preferably 3 ml/10 minutes or more, and still more preferably 5 ml/10 minutes or more. In the case of the above range, a sufficient size of the cavity can be generated, and breakage during stretching can be easily avoided.
On the other hand, the upper limit is generally 50 ml/10 minutes or less, preferably 40 ml/10 minutes or less, more preferably 30 ml/10 minutes or less, and even more preferably 25 ml/10 minutes or less. In the case of the above range, it is possible to avoid clipping during lateral stretching, and it is possible to maintain productivity.

The lower limit of the content of the polyester-incompatible polymer in the surface layer is usually 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, still more preferably 5% by weight or more, and particularly preferably 8% by weight. % or more. By using it in the above range, a sufficient amount of microvoids is generated in the film, the hiding property of the film is improved, and the effect of reducing the apparent density, that is, the weight is sufficiently reduced. In addition, the slipperiness of the film and the writing ability with a pencil or the like are improved, which is advantageous for print transportability. Further, on the surface of the film, characters and images formed by printed toner and/or image-forming substances can be easily peeled off, making it possible to repeatedly use the film as a recording material for copy paper and printer paper. Tend.
On the other hand, the upper limit of the content of the polymer incompatible with polyester in the surface layer is usually 70% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less, still more preferably 35% by weight or less, and particularly preferably 30% by weight or less, most preferably 25% by weight or less. By using it in this range, the amount of cavities generated is not too large, and there is a tendency to easily suppress breakage during stretching.

In addition, the lower limit of the content of the polyester-incompatible polymer in each layer of the laminated white polyester film is usually 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, and still more preferably 5% by weight. above, and particularly preferably at least 8% by weight. By using it in the above range, it is possible to have a sufficient concealing property and to achieve a sufficient effect of reducing the apparent density, that is, a reduction in weight.
On the other hand, the upper limit of the content of the polyester-incompatible polymer in each layer of the laminated white polyester film is usually 70% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less, and still more preferably 35% by weight. Below, particularly preferably 30% by weight or less, most preferably 25% by weight or less. By using it in this range, the amount of cavities generated is not too large, and there is a tendency to easily suppress breakage during stretching.

When the present laminated white polyester film has a structure of three or more layers, the intermediate layer may be a recycled product such as the selvage generated during film production, the master roll selvage and the lower winding of the master roll within the scope of the present invention. May be blended. Containing recycled products has the effect of reducing costs and reducing environmental impact. The content of the recycled product in the intermediate layer is preferably 95% by weight or less, more preferably 85% by weight or less, relative to the intermediate layer from the viewpoint of film formation stability due to reduction in intrinsic viscosity in addition to color tone regulation. , more preferably 70% by weight or less, particularly preferably 60% by weight or less, and most preferably 40% by weight or less.

(metallic compound particles)
It is also possible to incorporate metal compound particles into the laminated white polyester film for the purpose of further improving the hiding power and whiteness. When the polyester film has a structure of three or more layers, it may be a surface layer or an intermediate layer. preferably.

The metal compound particles used in this laminated white polyester film tend to compensate for white opacity due to the light scattering effect caused by fine cavities caused by blending incompatible polymers, resulting in higher hiding power and whiteness. tend to be obtained. Examples of the metal compound particles to be used include known titanium oxide, calcium carbonate, barium sulfate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, zirconium oxide and the like. Titanium is suitable.

The average particle size of the metal compound particles used has a lower limit of usually 0.05 µm or more, preferably 0.10 µm or more, more preferably 0.20 µm or more, and still more preferably 0.25 µm or more, and an upper limit of usually 0.50 µm or less. , preferably 0.45 μm or less, more preferably 0.40 μm or less. By using it in the above range, the degree of opacity when formed into a film becomes sufficient, and show-through tends to be improved particularly when the entire surface is printed on both sides of the film.

Furthermore, the lower limit of the content of the metal compound particles is preferably 1% by weight or more, more preferably 2% by weight or more, and still more preferably 3% by weight, based on the entire surface layer of the laminated white polyester film containing the metal compound particles. The upper limit is usually 30% by weight or less, preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 13% by weight or less, and particularly preferably 10% by weight or less. By setting it within the above range, it is possible to impart a sufficient degree of opacity, and it is also advantageous in terms of cost. tends to become a thing.

(Particles other than metal compound particles)
In order to improve the handleability and slipperiness of the laminated white polyester film, the surface layer of the laminated white polyester film contains particles other than the metal compound particles exemplified above for imparting slipperiness. good too.
Specific examples of particles other than the metal compound particles exemplified above include silica particles and organic particles. Examples of organic particles include organic particles such as acrylic resins, styrene resins, urea resins, phenol resins, epoxy resins, and benzoguanamine resins. Among them, silica particles are preferable because they are particularly effective even in a small amount.

The average particle size of the particles (silica particles or organic particles) other than the metal compound particles exemplified above is preferably more than 0.50 μm, more preferably 1.0 μm or more, still more preferably 1.5 μm or more, and particularly preferably 2.0 μm or more. By setting it as the said range, it tends to become possible to provide sufficient slipperiness. The upper limit of the average particle size of the particles is usually 15.0 μm or less, preferably 12.0 μm or less, more preferably 10.0 μm or less, and still more preferably 8.0 μm or less. By setting it in the above range, the film surface does not become too rough, and characters and images such as toner and / or image forming substances printed on the film surface are easily peeled off, and the film can be used as copying paper or the like. There is a tendency that it can be used repeatedly as a recording material for printer paper. Furthermore, it is not necessary to make the thickness of the surface layer extremely thick in terms of particle shedding, and the optimum range of the thickness is wide, which is a preferable form.

The shape of the particles (silica particles or organic particles) other than the metal compound particles exemplified above is also not particularly limited, and any of spherical, massive, rod-like, flattened and the like may be used. Moreover, there are no particular restrictions on its hardness, specific gravity, color, and the like. Two or more kinds of these particles may be used in combination, if necessary.

The content of particles (silica particles or organic particles) other than the metal compound particles exemplified above depends on the average particle size, so it cannot be said unconditionally, but the entire polyester film surface layer containing silica particles or organic particles On the other hand, it is usually 5% by weight or less, preferably 3% by weight or less, more preferably 2% by weight or less, further preferably 1% by weight or less, and the lower limit of the preferable range is 0.005% by weight or more, more It is preferably 0.05% by weight or more, more preferably 0.1% by weight or more. By using it in the above range, it becomes possible to make the surface roughness of the film moderate, and there is a tendency to achieve the desired lubricity. In addition to imparting lubricity, it also makes it easier to peel and remove letters and images such as toner and / or image forming substances printed on the film surface, and the film can be used as a recording material for copying paper and printer paper. It tends to be reusable. Furthermore, silica particles and organic particles tend to further improve the writability of pencils, mechanical pencils, ballpoint pens, and the like.

(other ingredients)
In addition to the above-mentioned particles and polymers incompatible with polyester, the present laminated white polyester film may optionally contain conventionally known antioxidants, heat stabilizers, lubricants, antistatic agents, and fluorescent brighteners. , dyes, pigments and the like can be added. Further, depending on the application, an ultraviolet absorber, particularly a benzoxazinone-based ultraviolet absorber, etc. may be contained.

(Laminate structure)
As described above, the present laminated white polyester film is a laminated film having at least two layers containing polyester as a main resin, at least the surface layer of which contains a polymer incompatible with polyester, and The laminated white polyester film is characterized in that the surface layer has an arithmetic mean roughness (SRa) of 950 nm or less.
As described above, if the surface layer contains polyester and a polymer incompatible with the polyester, fine cavities can be provided by stretching, so that weight reduction, concealability and whitening can be realized. Furthermore, since the surface roughness can be adjusted, the writability can be improved.

If the surface layer further contains metal compound particles, the hiding power and whiteness can be further improved, and by containing particles other than the metal compound particles, slipperiness can be improved.

As long as the intermediate layer other than the surface layer contains the polyester, it may optionally contain a polymer incompatible with the polyester, metal compound particles, and particles other than the metal compound particles. It is preferable to reduce the content of the metal compound particles and particles other than the metal compound particles as much as possible, and to use polyester as a recycled product in combination from the viewpoint of cost reduction and environmental load reduction.

(thickness)
The thickness of the laminated white polyester film is not particularly limited as long as it can be formed as a film. ~350 μm range. By using it in the above range, it becomes possible to make the film stiffness and handleability sufficient.

In this laminated white polyester film, the content of metal compound particles and particles other than metal compound particles contained in recycled products is as small as possible. It is preferable to contain. In addition, it is preferable to use a co-extrusion method to form a laminated structure in order to reduce costs and reduce environmental impact by blending recycled products in the intermediate layer. From this point of view, when the polyester film has a laminated structure of three or more layers as described above, the thickness of each surface layer is preferably 1 μm to 50 μm, especially 2 μm or more or 40 μm or less, especially 3 μm or more or 30 μm. Below, among them, it is more preferable that the thickness is 4 μm or more or 25 μm or less. By using it in the above range, it becomes possible to fully exhibit the performance of the metal compound particles and particles other than the metal compound particles described later, and the production cost can be kept low.

(apparent density)
The lower limit of the apparent density of the laminated white polyester film is usually 0.7 g/cm ³ or more, preferably 0.75 g/cm ³ or more, more preferably 0.8 g/cm ³ or more. By setting it to the above range, the strength of the film can be maintained, and clogging of the film in the transport process in the copying machine can be reduced when using it as a recording material instead of paper for copying paper or printer paper, which is an information printing medium. This makes it possible to perform optimal printing/printing.
On the other hand, the upper limit is usually 1.3 g/cm ³ or less, preferably 1.2 g/cm ³ or less, more preferably 1.1 g/cm ³ or less. By setting it within the above range, it is possible to reduce the work burden when carrying a large amount of printed materials, and to reduce the environmental impact and cost by reducing the _CO2 generated in the film (sheet) transportation process. .
The apparent density of the polyester film can be adjusted by blending an incompatible polymer having a lower specific gravity than the polyester that is the main component resin, and stretching in at least one direction. However, it is not limited to these methods.

<Physical properties>
The arithmetic mean roughness (SRa) of the surface of the laminated white polyester film, that is, the surface layer is preferably 950 nm or less, more preferably 850 nm or less, and more preferably 800 nm or less. By using the arithmetic average roughness (SRa) within the above range, characters and images such as toner containing thermoplastic resin and/or image forming substances formed on the film surface by printing or printing can be easily peeled off and removed. The film tends to be used repeatedly as a recording material for copying paper and printer paper.
On the other hand, the lower limit of the arithmetic mean roughness (SRa) is preferably 100 nm or more, more preferably 200 nm or more, more preferably 300 nm or more, and more preferably 350 nm or more. By setting the thickness within the above range, it is possible to obtain sufficient concealability and transportability, and it is possible to obtain a film most suitable for use as a recording material for copying paper and printer paper. Furthermore, it tends to have sufficient writability.
In addition, the arithmetic mean roughness (SRa) in the present invention shall be based on the measuring method used in the examples described later.

The b value (reflection method), which is an index representing the yellowness of the laminated white polyester film, is usually 0.00 or less, preferably -0.20 or less, more preferably -0.40 or less, and further preferably -0. It is 50 or less, particularly preferably -0.60 or less, and the lower limit is not particularly limited, but -5.0 or more is preferable. By using it in the above range, the yellowness can be suppressed and the whiteness can be improved. Furthermore, when used as a recording material for color printing, the resulting image tends to be of excellent quality.

The laminated white polyester film has a heat shrinkage rate of 2.8% or less, preferably 2.3% or less as an absolute value in the film longitudinal direction (MD) and the film width direction (TD) at 150° C. for 30 minutes. More preferably, it is 2.0% or less.
By setting the heat shrinkage rate within the above range, when printing or printing on a recording material by a method such as an electrophotographic method or a thermal transfer method in which a toner image is transferred to the recording material, the dimensional stability of the film is improved due to the influence of heat. In particular, the edge of the film (sheet), that is, the part where wrinkles are likely to occur, can also suppress the occurrence of wrinkles, resulting in distortion and unevenness in characters and images. As a result, it is possible to suppress the phenomenon that the image quality deteriorates. In addition, since wrinkles cannot be erased once they occur, they cannot be used repeatedly as recording materials such as copying paper and printer paper.

The opacity (OD) of the laminated white polyester film is usually 0.30 or more, preferably 0.35 or more, more preferably 0.40 or more, and still more preferably 0, as measured by a single film with a Macbeth densitometer. .45 or higher. By using the amount within the above range, show-through is reduced when the entire surface is printed on both sides of the film, and high-quality characters and images can be obtained. On the other hand, the upper limit of the opacifying property (OD) is not particularly limited, but considering the balance of other physical properties, it is preferably 1.0 or less, more preferably 0.9 or less.

The whiteness of the laminated white polyester film is determined by measuring the Hunter whiteness (Wb) of a single film with a colorimeter, and the lower limit is usually 80.0% or more, preferably 81.0% or more, more preferably 81.0% or more. is 82.0% or more, more preferably 83.0% or more, and particularly preferably 83.5% or more. By keeping the whiteness within the above range, when used as a recording material for copying paper and printer paper, which are information printing media that replace paper, especially when color printing is performed, characters and images can be produced with high definition. , and tends to be favorable in terms of quality. In addition, since it depends on the application to be used, a higher value is preferable in order to give a sense of quality, and the upper limit is not particularly limited. On the other hand, when used in applications where gloss is a concern, the upper limit of the preferred range is 95.0% or less.

<Function layer>
A functional layer may be provided on at least one side of the laminated white polyester film.
The functional layer preferably has antistatic performance and release performance.
In the laminated white polyester film, the apparent density can be reduced, whitening can be performed without incurring costs, and characters and images such as printed or printed thermoplastic resin-containing toners and/or image-forming substances can be added. In order to realize easy peeling and removal, it is preferable to have a polyester resin layer containing polyester and a polymer incompatible with polyester, and it is more preferable that the polyester resin layer is provided on the surface layer. However, it was found that when a functional layer is provided, it tends to be difficult to develop the ability to easily peel and remove characters and images such as toner and/or image forming substances on the surface layer. Preferably, the layer also has release properties.

When using this laminated white polyester film as a recording material for copying paper or printer paper, which can suitably transfer the toner image by a method such as an electrophotographic method or a thermal transfer method for transferring the toner image to the recording material, it can be It is intended to prevent double feeding in paper transport of the machine and to prevent paper from sticking to each other when handling paper. Furthermore, in order to prevent adhesion of dust and to obtain a good quality film or a film print with good image quality, it is preferable to have a functional layer containing an antistatic agent on at least one side.

In addition, the functional layer has a release property so that characters such as a toner containing a thermoplastic resin formed on the film surface and an image forming substance can be suitably peeled off after printing or printing. It is preferable to contain a mold release agent to provide the

In addition, the functional layer contains a polymer for improving the ease of forming the image forming substance and improving the adhesiveness, and for improving the wettability to the substrate film when the functional layer is provided by coating. It is preferable to contain (a polymer other than the antistatic agent and release agent described above).

The functional layer contains an antistatic agent, a release agent, and a polymer to impart appropriate release performance, thereby adhering toner and/or image-forming substances, etc. to the film surface; It was found that the function of peeling and removing the image forming substance and the like can be obtained more appropriately. In other words, the present inventors have found a technique for realizing the conflicting properties of adhesiveness and peelability with a single functional layer to a higher degree. This technology can be said to be a highly effective technology considering that peeling performance cannot be achieved with a functional layer having general adhesive performance, while adhesive performance cannot be achieved with a functional layer having general peeling performance. . Moreover, even if a functional layer having adhesive performance and a functional layer having peeling performance are laminated, neither performance can be exhibited, and only the performance of the outermost functional layer is reflected.

Even when the present laminated polyester film has the functional layer, the preferred ranges of the b value, heat shrinkage, opacity (OD), and whiteness of the present laminated polyester film are the same as the numerical ranges described above. .

<Manufacturing method>
The method for producing the present laminated white polyester film will be specifically described below, but the present invention is not particularly limited to the following examples as long as the gist of the present invention is satisfied.

First, raw materials, which are dried or undried by a known method and mixed for each layer, are supplied to each melt extruder, heated to a temperature equal to or higher than the melting point of each polymer, and melt-kneaded. The molten polymer for each layer is then directed, typically through a multi-manifold or feedblock, to a die for lamination.
The molten sheet extruded from the die is then quenched and solidified on a rotating cooling drum to a temperature below the glass transition temperature to obtain an unoriented sheet in a substantially amorphous state. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotating cooling drum, and the electrostatic application adhesion method and/or the liquid application adhesion method are preferably employed.

The sheet obtained as described above is stretched to form a film. The ultrafine closed cavities contained in the polyester film are produced by such stretching.

Specifically, the unstretched sheet is preferably stretched 2.5 to 5 times in the longitudinal direction (longitudinal direction) at 70 to 150 ° C. to form a longitudinal uniaxially stretched film, and then stretched in the width direction ( The film is stretched 3 to 5 times at 70 to 160° C. in the transverse direction), usually 200 to 250° C., preferably 210 to 240° C., more preferably 215 to 240° C., usually 5 to 600 seconds, preferably 8 It is preferable to perform the heat treatment for up to 300 seconds.

Various conditions of the heat treatment process affect not only the heat shrinkage of the film but also the arithmetic mean roughness (SRa) of the surface layer of the film. That is, by setting the temperature to a high temperature within the above range, the ultrafine voids formed by the polymer incompatible with the polyester existing on the surface of the surface layer are dissolved. By moderately reducing the surface roughness, it becomes possible to easily peel and remove characters and images such as a toner containing a thermoplastic resin and/or an image forming substance formed on the film surface by printing or printing. . As a result, the film can be repeatedly used as a recording material for copy paper and printer paper.

After the heat treatment step, a method of relaxing 2 to 20% in the longitudinal direction and/or the transverse direction in the highest temperature zone of the heat treatment and/or the cooling zone at the exit of the heat treatment is preferred. In addition, re-stretching in the longitudinal direction and re-stretching in the lateral direction can be added as necessary.

A method for forming a functional layer on this laminated white polyester film will be described below. The functional layer can be provided by various known methods such as a coating method, a coextrusion method, and a transfer method. Among them, the one by coating is preferable from the viewpoint of efficient production and imparting performance.

As the coating method, the film surface may be treated during the film forming process of the polyester film, which may be provided by in-line coating, or may be applied to the film once produced outside the system, which may employ offline coating. . More preferably, it is formed by in-line coating.

In-line coating is a method of coating in the process of polyester film production, specifically, a method of coating at any stage from melt extrusion of polyester to stretching, heat setting and winding. Usually, it is coated on an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after heat setting and before winding. Although it is not limited to the following, for example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (machine direction) is coated and then stretched in the transverse direction is excellent. According to such a method, film formation and functional layer formation can be performed at the same time, which is advantageous in terms of manufacturing cost. In addition, since stretching is performed after coating, the thickness of the functional layer can be changed by the stretching ratio. , thin film coating can be performed more easily than offline coating. Further, by providing the functional layer on the film before stretching, the functional layer can be stretched together with the base film, thereby firmly adhering the functional layer to the base film. Furthermore, in the production of biaxially stretched polyester film, the film can be restrained in the vertical and horizontal directions by holding the ends of the film with a clip or the like while the film is stretched. High temperature can be applied while maintaining the properties. Therefore, since the heat treatment applied after coating can be performed at a high temperature that cannot be achieved by other methods, the film-forming property of the functional layer is improved, and the functional layer and the base film can be adhered more firmly. Furthermore, a strong functional layer can be obtained, the functional layer can be prevented from coming off, and antistatic performance and release performance can be improved.

<Toner and/or Image Forming Substance>
Characters and images containing a thermoplastic resin such as a toner and/or an image-forming substance are provided on the surface of the laminated white polyester film on which the functional layer is not provided or on the surface on which the functional layer is provided. Is possible.
Characters and images can be provided by a conventionally known method, and can be obtained by printing or printing with a copier, printer, or the like. Also, conventionally known materials can be used for thermoplastic resins such as toners and/or image forming substances.

<Resin layer>
In this laminated white polyester film, a resin layer can be further provided on characters and images containing thermoplastic resin such as toner and/or image forming substance.
The resin layer may be provided so as to peel off characters and images from the film together with the resin layer in order to reuse the laminated white polyester film.

A conventionally known material can be used as the resin layer, and a curable resin layer is preferable.
The curable resin layer includes a thermosetting resin layer and an active energy ray-curable resin layer. An active energy ray-curable resin layer is preferred from the viewpoint that it is easy to peel and remove without leaving any characters or images.

Examples of the active energy ray-curable resin layer include an ultraviolet-curable resin layer, an electron beam-curable resin layer, and a visible light-curable resin layer. It is preferably a flexible resin layer. An example of the active energy ray-curable resin layer is a hard coat layer.

The material used for the active energy ray-curable resin layer is not particularly limited. mentioned. Among these, from the viewpoint of compatibility between productivity and hardness, it is particularly preferable to use a polymerized and cured product of a composition containing an active energy ray-curable (meth)acrylate.

A composition containing an active energy ray-curable (meth)acrylate is not particularly limited. For example, mixtures of one or more of known active energy ray-curable monofunctional (meth)acrylates, bifunctional (meth)acrylates, and polyfunctional (meth)acrylates, and commercially available active energy ray-curable hard coating resin materials or those to which other components are further added as long as they do not impair the object of the present embodiment.

The active energy ray-curable monofunctional (meth)acrylate is not particularly limited. For example, alkyls such as methyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc. hydroxyalkyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate Alkoxyalkyl (meth)acrylates such as meth)acrylate and ethoxypropyl (meth)acrylate, aromatic (meth)acrylates such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxypropyl (meth)acrylate, diaminoethyl ( meth)acrylates, amino group-containing (meth)acrylates such as diethylaminoethyl (meth)acrylate, ethylene oxides such as methoxyethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, and phenylphenol ethylene oxide-modified (meth)acrylates modified (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylic acid and the like.

The active energy ray-curable bifunctional (meth)acrylate is not particularly limited. For example, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecanedi alkanediol di(meth)acrylates such as methylol di(meth)acrylate; bisphenol-modified di(meth)acrylates such as bisphenol A ethylene oxide-modified di(meth)acrylate; bisphenol F ethylene oxide-modified di(meth)acrylate; (Meth)acrylate, polypropylene glycol di(meth)acrylate, urethane di(meth)acrylate, epoxy di(meth)acrylate and the like.

The active energy ray-curable polyfunctional (meth)acrylate is not particularly limited. For example, dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylol propane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (Meth) acrylates, isocyanuric acid-modified tri(meth) acrylates such as ε-caprolactone-modified tris(acloxyethyl) isocyanurate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, di Examples include urethane acrylates such as pentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer.

Other components contained in the composition containing the active energy ray-curable (meth)acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers and leveling agents. Moreover, in the case of drying after film formation in the wet coating method, an arbitrary amount of solvent can be added.

For indoor use such as offices, it is preferably solvent-free. As the resin (resin liquid) for forming the resin layer, the solvent content is preferably 10% by weight or less, more preferably 5% by weight or less, even more preferably 3% by weight or less, and particularly preferably 1% by weight or less. and most preferably solvent free (intentionally free).

Methods for forming the resin layer include general wet coating methods such as roll coating and die coating, and extrusion methods. The formed resin layer can be heated or irradiated with an active energy ray such as an ultraviolet ray or an electron beam as necessary to carry out a curing reaction.

<Explanation of terms, etc.>
In the present invention, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less" and "preferably larger than X" or "preferably Y It also includes the meaning of "less than".
In addition, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably greater than X" unless otherwise specified, and is described as "Y or less" (Y is an arbitrary number). If not otherwise specified, it also includes the meaning of "preferably smaller than Y".

[EXAMPLES] Hereafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Examples, unless the gist is exceeded. Moreover, the measuring method used in the present invention is as follows. Various physical properties, methods for measuring them, and definitions in the present invention are as follows.

<Measurement method>
(1) Intrinsic viscosity of polyester Accurately weigh 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed, add 100 ml of a mixed solvent of phenol/tetrachloroethane = 50/50 (weight ratio) and dissolve. , 30°C.

(2) Melt flow index (MFI)
In accordance with JIS K7210-1995, the amorphous polyolefin was measured at 275°C and 21.2N, and the crystalline polypropylene was measured at 230°C and 21.2N. A higher value indicates a lower melt viscosity of the polymer.

(3) Arithmetic mean roughness (SRa)
The surface of the laminated white polyester film is measured using a non-contact surface/layer cross-sectional shape measurement system VertScan (registered trademark) R550GML manufactured by Ryoka Systems Co., Ltd., CCD camera: SONY HR-50 1/3 ', objective lens: 20 Magnification, Lens barrel: 1X Body, Zoom lens: No Relay, Wavelength filter: 530 white, Measurement mode: Wave, measure a 640 μm × 480 μm area, and use the output from a 4th-order polynomial correction to calculate the arithmetic mean roughness. The SRa value was obtained by averaging 10 points.

(4) Average Particle Size Particle size was measured by a sedimentation method based on Stokes' law of resistance using a centrifugal sedimentation particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation. The average particle size was obtained by using the value of 50% of the cumulative (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement.

(5) Heat Shrinkage A sample was treated for 30 minutes in an oven maintained at 150° C. without tension, and the length of the sample before and after was measured to calculate the heat shrinkage using the following equation.
Heat shrinkage rate (%) = {(L0-L1)/L0} x 100
(In the above formula, L0 is the sample length before heat treatment, and L1 is the sample length after heat treatment)
Five points were measured in the longitudinal direction (MD) and the width direction (TD) of the film, and the average value for each direction was obtained.

(6) Hunter whiteness Hunter whiteness ( Wb) was measured. The back surface of the film was pressed with a black plate.

(7) b value (reflection method)
Using a colorimeter NDH-1001DP (C light source, 2° field of view) manufactured by Nippon Denshoku Industries Co., Ltd., the b value of a single film was measured according to the method of JIS Z-8722, 8730. The back surface of the film was pressed with a black plate.

(8) Opacity (OD)
A Macbeth densitometer TD-904 was used to measure the transmission density under white light. Measurement was performed at 5 points, and the average value was taken as the OD value. A larger value indicates a lower light transmittance.

(9) Apparent density (g/cm ³ )
A square sample of 10 cm x 10 cm was cut out from an arbitrary portion of the film, and the thickness of the sample was evenly measured at 9 points with a micrometer. From the average value and the weight of the film, the weight per unit volume was calculated as the apparent density. The number of measurements was 5, and the average value was used.

(10) Thickness of Laminated White Polyester Film A piece of film was fixed and molded with an epoxy resin, cut with a microtome, and the cross section of the film was observed with a transmission electron microscope. Among the cross sections, two interfaces are observed by light and shade almost parallel to the film surface. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was taken as the thickness of the laminated white polyester film.

(11) Appropriate image quality by electrophotographic printing: Ricoh Co., Ltd.'s multifunctional machine: imagioMPC5001it, a film (sheet) cut to A4 size is fed, and a full-color test image on which an image forming material is printed by photo printing is printed. Obtained. Image quality was evaluated as follows.
(Evaluation criteria)
A: High-definition, high-quality image quality with no wrinkles on the film B: Part of the image quality is slightly blurred, but there is no practical problem C: Wrinkles on the film, image quality is unclear overall inferior to

(12) Characters and images (toner images) are suitable for peeling and removal. 95 parts by weight of an ultraviolet curable resin (2-hydroxy-3-phenoxypropyl acrylate) is applied to the surface of the film on which the image forming substance obtained in (11) is fixed. A mixture of 5 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) is uniformly applied, a glass plate is placed on the mixture, and ultraviolet rays are irradiated from above to cure the mixture. A flexible resin layer was formed. After that, the glass plate and the film were separated. At this time, the formed ultraviolet curable resin layer adheres to the glass plate side, and can transfer and hold characters and images formed by the toner and/or the image forming substance formed on the film surface. At this time, the following evaluations were made with respect to the peeled-off state of characters and images on the film surface.
(Evaluation criteria)
A: The image-forming substances on the film surface can be completely removed, and the film can be used repeatedly as copying paper.
B: A small amount of image forming material remains on the surface of the film, but it can be used repeatedly as copying paper, and there is no practical problem.
C: Most of the image-forming substance remained on the film surface, and the film could not be used repeatedly as copying paper.

(13) Writability
Five straight lines were drawn at intervals of 1 mm with a pencil of hardness H of Uni manufactured by Mitsubishi Pencil Co., Ltd., and the following evaluations were made by visual observation.
(Evaluation criteria)
A: Individual straight lines can be distinguished.
B: The color of the lines is light, and individual lines are difficult to distinguish.
C: A straight line cannot be drawn.

[Example 1]
As an intermediate layer, a mixed raw material obtained by mixing 80 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.67 dl/g and 20 parts by weight of crystalline polypropylene homopolymer chips having a melt flow index of 10 ml/10 minutes was prepared at 280°C. was fed into the main vented twin-screw extruder set to .
As the surface layer, 15 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 50% by weight of titanium oxide particles having an average particle size of 0.32 μm, and a crystalline polypropylene having a melt flow index of 8 ml/10 min. 15 parts by weight of homopolymer chips, 10 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 3.5% by weight of silica particles having an average particle size of 4.1 μm, and an intrinsic viscosity of 0.69 dl/g A mixture of 60 parts by weight of polyethylene terephthalate chips was fed into a sub-vented twin-screw extruder set at 280°C.
Through a gear pump and a filter, the polymer from the main extruder becomes the intermediate layer, and the polymer from the sub-extruder becomes the surface layer. Extrusion was followed by rapid cooling and solidification on a cooling roll whose surface temperature was set to 30° C. using an electrostatic contact method to obtain an unstretched sheet with a thickness of 887 μm.
The obtained unstretched sheet was stretched 3.1 times in the machine direction at 92° C., led to a tenter, stretched in the transverse direction by 3.8 times at 120° C., and then heat-treated at 235° C. for 10 seconds. A biaxially oriented laminated white polyester film having a thickness structure of 6 μm (surface layer)/62 μm (intermediate layer)/6 μm (surface layer) and having a total thickness of 74 μm was obtained by relaxing 10% in the transverse direction.
Evaluation of the obtained laminated white polyester film revealed that the image quality, characters, image peeling and removal suitability and writability were all good. Properties of this film are shown in Tables 2 and 3 below.

[Example 2]
As an intermediate layer, 40 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.63 dl/g, and 15 parts by weight of crystalline polypropylene homopolymer chips having a melt flow index of 7 ml/10 minutes, generated during the polyester production of Example 1. A biaxially oriented laminated white polyester film with a thickness of 75 μm was obtained in the same manner as in Example 1, except that a mixed raw material in which 45% by weight of lugs and recycled lugs from master rolls was mixed was used. The thickness of each layer of the resulting film was 6 μm/63 μm/6 μm. The total amount of the crystalline polypropylene homopolymer chip-derived and recycled polypropylene in the intermediate layer was 24% by weight.
Evaluation of the obtained laminated white polyester film revealed that the image quality, characters, image peeling and removal suitability and writability were all good. Properties of this film are shown in Tables 2 and 3 below.

[Example 3]
As an intermediate layer, 3 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g, and 10 parts by weight of crystalline polypropylene homopolymer chips having a melt flow index of 10 ml/10 minutes, generated during the production of the polyester of Example 1. A biaxially oriented laminated white polyester film with a thickness of 75 μm was obtained in the same manner as in Example 1, except that a mixed raw material in which 87% by weight of the lugs and recycled products from the lugs of the master roll were mixed was used. The thickness of each layer of the resulting film was 6 μm/63 μm/6 μm.
The resulting laminated white polyester film was evaluated to find that the character and image peelability and writability were all good. Properties of this film are shown in Tables 2 and 3 below.

[Example 4]
As the surface layer, 15 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 50% by weight of titanium oxide particles having an average particle size of 0.12 μm, and a crystalline polypropylene homopolymer having a melt flow index of 8 ml/10 min. 15 parts by weight of chips, polyethylene terephthalate having an intrinsic viscosity of 0.66 dl/g containing 3.5% by weight of silica particles having an average particle size of 4.1 μm 10 parts by weight of chips, polyethylene terephthalate having an intrinsic viscosity of 0.69 dl/g A biaxially oriented laminated white polyester film with a thickness of 75 μm was obtained in the same manner as in Example 1, except that a mixed raw material mixed at a rate of 60 parts by weight of chips was used. The thickness of each layer of the resulting film was 6 μm/63 μm/6 μm.
The resulting laminated white polyester film was evaluated to find that the character and image peelability and writability were all good. Properties of this film are shown in Tables 2 and 3 below.

[Example 5]
As the surface layer, 15 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 50% by weight of titanium oxide particles having an average particle size of 0.32 μm, and a crystalline polypropylene homopolymer having a melt flow index of 8 ml/10 min. 1.3 parts by weight of polymer chips, 1.6 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 0.5% by weight of silica particles having an average particle size of 4.1 μm, and an intrinsic viscosity of 0 A biaxially oriented laminated white polyester film with a thickness of 74 μm was obtained in the same manner as in Example 2, except that a mixed raw material in which polyethylene terephthalate chips of 0.69 dl/g were mixed at a ratio of 82.1 parts by weight was used. The thickness of each layer of the obtained film was 6 μm/62 μm/6 μm.
The resulting laminated white polyester film was evaluated and found to have good image quality. Properties of this film are shown in Tables 2 and 3 below.

[Example 6]
As the surface layer, 15 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.65 dl/g containing 50% by weight of titanium oxide particles having an average particle size of 0.32 μm, and a crystalline polypropylene homopolymer having a melt flow index of 8 ml/10 min. 0.5 parts by weight of polymer chips, 10 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 3.5% by weight of silica particles having an average particle size of 4.1 μm, and an intrinsic viscosity of 0.68 dl A biaxially oriented laminated white polyester film with a thickness of 75 μm was obtained in the same manner as in Example 2, except that a mixed raw material in which 74.5 parts by weight of polyethylene terephthalate chips of 1/g was mixed was used. The thickness of each layer of the resulting film was 6 μm/63 μm/6 μm.
The resulting laminated white polyester film was evaluated and found to have good image quality. Properties of this film are shown in Tables 2 and 3 below.

[Comparative Example 1]
As a surface layer, 15 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 50% by weight of titanium oxide particles having an average particle size of 0.32 μm, and a crystalline polypropylene homopolymer having a melt flow index of 8 ml/10 min. 15 parts by weight of chips and 70 parts by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.66 dl/g containing 5.0% by weight of silica particles having an average particle diameter of 11.1 μm were used. was carried out in the same manner as in Example 2 to obtain a biaxially oriented laminated white polyester film having a thickness of 75 μm. The thickness of each layer of the resulting film was 6 μm/63 μm/6 μm.
As shown in Tables 2 and 3 below, the resulting laminated white polyester film was poor in peeling and removing properties of characters and images.

[Comparative Example 2]
A biaxially oriented laminated white film having a thickness of 75 μm and a thickness of each layer of 6 μm/63 μm/6 μm was performed in the same manner as in Example 2, except that the heat treatment was performed at a heat treatment temperature of 201° C. for 10 seconds in the heat treatment step in the film formation process. A polyester film was obtained.
As shown in Tables 2 and 3 below, the resulting laminated white polyester film was poor in image quality suitability and characters and image peeling removal suitability.

Claims (5)

The surface layer has fine cavities formed by containing a polymer incompatible with polyester, and the surface layer has an arithmetic average roughness (SRa) of 950 nm or less, and toner and toner are formed on at least one surface layer. / Or a layer comprising an image-forming substance and a resin layer thereon, which is a layer made of an active energy ray-curable resin from which the resin layer can be peeled off, and which is used as a recording material, which is an information printing medium instead of paper. polyester film. 2. The laminated white polyester film according to claim 1, wherein the surface layer contains metallic compound particles. 3. The laminated white polyester film according to claim 2, wherein the surface layer contains particles other than the metal compound particles. 4. The laminated white polyester film according to any one of claims 1 to 3, wherein the surface layer contains 1% by weight or more of the polymer incompatible with the polyester. A recording material using the laminated white polyester film according to any one of claims 1 to 4 .