JPH08290538A - Fine cell containing laminated polyester film - Google Patents

Abstract

PURPOSE: To provide a fine cell containing laminated polyester film, the weight per unit volume of which is reduced and, at the same time, which has cushioning properties and is excellent in surface smoothness, whiteness and especially the adhesion to gelatin, and can produce at low cost and especially is suitable for high quality photographic paper. CONSTITUTION: To one side or both sides of a polyester layer B, which contains a large number of fine closed cells so as to have the density of 0.40-1.30g/cm<3> , a polyester layer A, the density of which is larger than 1.30g/cm, is laminated so as to obtain the fine cell containing the laminated polyester film under the condition that the b-value of the surface of the layer A serving as one topmost surface is below 2.0 and its surface roughness Ra is 0.030-0.50μm while the surface roughness Ra of the other topmost surface is larger than the Ra of the above-mentioned topmost surface and the easily bonding layer to gelatin is provided on the surface on the side, the surface roughness of which is lower than that of the other side.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a laminated polyester film provided with a gelatin easy-adhesion layer. More specifically, the present invention is a film in which the weight per unit volume is reduced by containing fine closed cells and has a cushioning property, and is excellent in surface smoothness, whiteness, and particularly adhesion to gelatin. Moreover, it can be produced at low cost,
In particular, the present invention relates to a finely bubble-containing laminated polyester film suitable for high quality photographic paper.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are widely used as industrial materials because they have various properties in a well-balanced manner and are excellent in cost performance. Among polyester films, recently, a white film having a cushioning property has been used, which is made lightweight by containing fine bubbles. Such films have come to be used, for example, in printer image-receiving papers, dust-free papers, labels, decorative papers, tracing papers as synthetic papers, or as white films for magnetic cards. Further, JP-A-49-134755 proposes to use an opaque film obtained by stretching and heat treating a polyester to which polyolefin is added, for use in photographic printing paper. However, when such a film is used for photographic paper, there is a problem that the surface has a rough surface and thus its shape adversely affects the image, or the whiteness is insufficient and the image quality is deteriorated.

In order to solve such a problem, the cost is increased by adding expensive white particles or a fluorescent whitening agent or using an expensive heat resistant resin as a void forming material. In recent years, when the demand for cost reduction has become extremely strong, the range of use of such films is extremely narrow and limited, and the need for white films of high quality and low cost is increasing.

When a functional layer such as a photosensitive layer, a printing layer, a magnetic layer coating, a metal vapor deposition, an adhesive layer or a release layer, or a lamination with another polymer is formed on the surface of the film, it is easily formed. It is necessary not to peel. Conventionally, in order to improve the adhesiveness with these functional layers,
An undercoat layer is provided on the surface of the polyester film, and this undercoat layer is formed by coating in the film forming process of the film and then continuously stretching, that is, in the case of so-called in-line coating and after the film formation is completed. In some cases, so-called off-line coating is applied to the rolled film. In fact, the required level of adhesiveness is improved, the adhesiveness with the functional layer is fully considered, and even if an improved undercoating layer is provided, the familiarity between the polyester film surface and the undercoating layer is poor. There is a problem that peeling occurs at the interface.

As mentioned above, the functional layer tends to be diversified, but especially the functional layer has an affinity for water such as gelatin, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), cellulose and / or their derivatives. In the case of containing a high polymer (specific examples include a photographic film, an ink image-receiving film, a plate-making film, etc.), the above problem becomes remarkable. An acrylic resin can be given as a resin having good adhesiveness to these functional layers, but it has a problem that it is not familiar with the polyester film and easily peels off at the interface between the undercoat layer and the polyester film.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, provided a gelatin easy-adhesion layer on a film having a specific constitution in which a polyester layer was laminated on a film containing fine bubbles. As a result, it was found that a film having excellent adhesiveness with the photographic image forming layer and satisfying each property as a printing paper was obtained, and that such a film could be produced with high productivity and at a relatively low cost, and thus the present invention was completed. It was

That is, the gist of the present invention is that it contains a large number of fine closed cells and has a density of 0.40 to 1.30 g / cm ^3.
A film obtained by laminating a polyester A layer having a density of more than 1.30 g / cm ^{3 on} one or both sides of the polyester B layer which is, wherein the b value of the surface of the A layer which is one outermost layer is 2.0. Less, surface roughness Ra is 0.030 to
0.50 μm, the surface roughness Ra of the other outermost layer
Is larger than Ra on the surface of the outermost layer, and a fine bubble-containing polyester film having an easy-adhesive gelatin layer on the surface on the low roughness side is present.

The present invention will be described in detail below. The laminated film of the present invention is obtained by stretching and heat-treating a resin extruded by a so-called co-extrusion method in which the resin constituting each layer is co-melt extruded from an extruder. Hereinafter, a coextruded two-layer or three-layer film will be described as a laminated film.
The present invention is not limited to these and may be a multilayer of 4 layers or more.

The polyester constituting each layer of the laminated film of the present invention is a polyester obtained from an aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 80% or more of repeating structural units are ethylene terephthalate. Refers to polyesters having units or ethylene-2,6-naphthalate units. Further, other third component may be contained as long as it does not deviate from the above range.

As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxy). Benzoic acid etc.) and the like can be used. As the glycol component, other than ethylene glycol, for example, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol,
One kind or two or more kinds such as neopentyl glycol can be used.

Books made from the above polyesters
The feature of the film of the invention is that it contains a large number of fine closed cells.
Containing almost all air bubbles on one or both sides of low density B layer
The point is to stack A layers that are not. That is, the density of layer B is
0.40 to 1.30 g / cm ³ Must be in the range
And preferably 0.50 to 1.20 g / cm³ ,
And preferably 0.70 to 1.10 g / cm³ In the range of
is there. The density of layer A is 1.30 g / cm.³ Greater than
Required, preferably 1.35 to 1.50 g
/ Cm³ Range. B layer has a density of 1.30 g / cm
³ If it exceeds, the content of closed cells is small, and
The cushioning and paper-like texture that are the characteristics of the film are lost.
You will be told. On the other hand, the density of the B layer is 0.40 g / c
m³ If it is less than 1, the mechanical strength of the film is significantly reduced.
However, productivity is also significantly deteriorated, which is not preferable.
Further, the density of the A layer is 1.30 g / cm.³ If:
The flatness of the surface of layer A is impaired, resulting in deterioration of image quality.
This is not preferable.

In the present invention, the total thickness of the film is 5
It is 0 to 250 μm, and the thickness of the B layer containing the closed fine cells is preferably 60% or more of the total thickness, and 80
% Or more is more preferable. B layer thickness is 60%
When it is less than the above range, the lightness and cushioning property of the film, which are the features of the present invention, are not satisfied. On the other hand, A which forms a flat surface
The layer thickness is usually 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less. Even if the thickness of the layer A exceeds 30 μm, the smoothness of the surface hardly changes any more, and the density of the entire film may increase, or the cushioning property may deteriorate.
Further, in order to satisfy the smoothness of the surface of the layer A, the thickness of the layer A is preferably 0.5 μm or more, more preferably 1.0 μm or more.

In the present invention, the manufacturing method is not particularly limited as long as the above-mentioned requirements are satisfied. That is, a method for producing a polyester film (layer B) containing fine bubbles is described in, for example, JP-A-50-38765, JP-B-57-46456, or JP-A-57-34931. And a method of forming a foam by adding a gas or a vaporizable substance as described above, JP-A-52-43871,
A method of forming a foam by adding a substance that chemically decomposes to generate a gas, as described in JP-B-58-50625, and further, JP-A-51-34963 and JP-B-58-34963. As described in JP-A No. 52-27666, there is a method of impregnating a liquid and extracting a substance soluble in a solvent to form a foam after molding, and any method may be adopted. Absent. However, all of these methods require a special molding device or processing device and complicate the process, so it cannot always be said that these methods can be easily adopted.

Therefore, the inventors of the present invention have previously proposed JP-A-63-168441 and JP-A-63-193938.
It is particularly preferable to employ the method described in Japanese Patent Publication or the like or a method similar thereto. That is, it is a method in which polyester is mixed with an incompatible polymer and extrusion-molded into a sheet, and then the obtained sheet is stretched at least uniaxially to form a film. When this method is adopted, the density of the present invention containing a large number of fine closed cells is 0.4 to
A polyester film (layer B) of 1.30 g / cm ³ can be obtained with good productivity and at low cost.

Examples of polymers incompatible with polyester include polyolefins such as polyethylene, polypropylene, polymethylpentene and polymethylbutene, polystyrene, polycarbonate, polyphenylene sulfide, liquid crystal polyester, etc., among which cost and productivity are high. From the viewpoint of, polypropylene is preferable.

The amount of such incompatible polymer compounded is usually 5 to 40% by weight, preferably 5 to 30% by weight, based on the polymer constituting the B layer. If the content is less than 5% by weight, the content of bubbles tends to be small, and there is a possibility that the weight saving of the film and the imparting of cushioning properties, which are the features of the present invention, may be insufficient. On the other hand, the content is 40
If it exceeds 5% by weight, the film tends to break during stretching, resulting in poor productivity. Thus, the polyester is blended with an incompatible polymer, but this method requires further stretching in at least uniaxial direction.
As described above, this is not only for giving the mechanical strength of the film, but also for containing sufficient closed cells only after the stretching step. This stretching method itself does not require a special operation and is performed within the range of conditions for producing a normal polyester film.

When polypropylene is used as the incompatible polymer, it is preferable that at least 95 mol% or more, preferably 98 mol% or more, of the crystalline polypropylene homopolymer having a propylene unit. When the polypropylene is amorphous, when it is made into an amorphous polyester sheet, the polypropylene bleeds out on the sheet surface, which contaminates the surface of the cooling drum, the drawing roll, etc., which is not preferable. Further, if the ethylene units other than the propylene units are copolymerized in an amount of more than 5 mol%, the formation of closed cells becomes insufficient, which is not preferable.

The melt flow index (MFI) of such polypropylene is usually 0.5 to 30 g / 10 minutes,
It is preferably in the range of 1.0 to 15 g / 10 minutes. MF
When I is less than 0.5 g / 10 minutes, the bubbles generated become large and breakage occurs during stretching, while 3
If it exceeds 0 g / 10 minutes, clip disengagement in the tenter may occur, density may not be evenly distributed over time, and density control may be difficult, resulting in deterioration of productivity.

When the method of blending an incompatible polymer as described above to generate fine bubbles is used, the size of the bubbles is controlled so that the density and cushioning property of the film are within a desired range. It is preferable that the layer raw material contains a surfactant. Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and the like, among which nonionic surfactants, especially silicone surfactants. Is preferred. Examples of the silicone-based surfactant include an organopolysiloxane-polyoxyalkylene copolymer and an alkenylsiloxane having a polyoxyalkylene side chain. The content of the surfactant is preferably 0.001 to 1.0% by weight, more preferably 0.01 to 0.5% by weight, based on the B layer raw material. When the content of the surfactant exceeds 1.0% by weight, the effect is no longer improved, and in addition, troubles in the extruder and deterioration of the polymer may occur.

On the other hand, the polyester layer (A layer) containing almost no fine closed cells is formed by laminating with the resin composition constituting the B layer by the coextrusion method.
That is, the raw materials for forming the A layer and the raw material for forming the B layer are melted by separate extruders, respectively, then introduced into one die, and the A layer and the B layer are laminated in a molten state and extruded in a slit shape to obtain a sheet. Is a way to get.

The polyester forming the layer A forms at least one surface of the film, and when used as photographic paper, a photographic image is formed on the surface of the layer A. Since the quality of such an image is affected by the roughness of the film surface, the surface of the A layer is required to be smooth. On the other hand, if the surface of the film is flat, scratches may occur on the surface during contact with various rolls or in the winding process during the film manufacturing process,
After all, it will affect the quality of photographic images. In order to solve this problem, it is preferable that the polyester forming the layer A of the film of the present invention contains particles to form appropriate protrusions on the film surface. Examples of such particles include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite,
Examples thereof include inorganic particles such as molybdenum sulfide, crosslinked polymer particles, organic particles such as calcium oxalate, and precipitated particles generated during polyester polymerization.

When used for photographic paper, it is preferable that the film is white and has a high degree of concealment in order to improve the sharpness of the image, and since the layer B of the film of the present invention contains fine bubbles, it has a certain degree. It has concealment and whiteness.
However, since the sharpness of the image largely depends on the characteristics near the film surface, it is preferable to improve the hiding power and whiteness of the layer A in the film of the present invention. For this purpose, titanium dioxide and barium sulfate are particularly preferable as the particles contained in the polyester of the layer A among the above examples. Further, two or more kinds of particles can be contained, and it is particularly preferable that at least one of them is titanium dioxide or barium sulfate.

The polyester forming the B layer also has
It may contain the same or different particles as the layers. The average particle size of the particles contained in the film of the present invention is preferably 0.005 to 5.0 μm, more preferably 0.01 to 5.0 μm.
It is in the range of 3.0 μm. If the average particle size exceeds 5.0 μm, the surface becomes rough and the quality of photographic images deteriorates.
There arises a problem that the particles easily fall off the surface of the film. On the other hand, if the average particle size is less than 0.005 μm, the formation of protrusions is insufficient, so that the surface of the film may be scratched or the handleability of the film may be deteriorated.

The content of particles in the layer A is 0.3 to 30.0% by weight, more preferably 0.5 to 20.0% by weight, and especially 1.0 to 10% by weight based on the polyester constituting the layer A. 20.0
It is preferably in the weight%. If the particle content is less than 0.3% by weight, the whiteness of the film surface is insufficient, and the quality of photographic images, especially the contrast and sharpness, tends to be insufficient. On the other hand, when the content of the particles exceeds 30.0% by weight, the particles are likely to come off, and the particles are aggregated to form coarse protrusions.

The content of particles in the layer B is not particularly limited, but is preferably less than 10% by weight from the viewpoint of cost and film productivity. When two or more kinds of particles are used, the total content of particles is preferably within the above range.

In producing the polyester containing particles constituting the layers A and B of the present invention, the particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When it is added during the synthesis reaction, a method of adding it as a slurry in which particles are dispersed in ethylene glycol or the like at any stage of polyester synthesis is preferable. On the other hand, when it is directly added to the polyester, a method of adding and mixing to the polyester as a dried particle or as a slurry dispersed in water or an organic solvent having a boiling point of 200 ° C. or less using a twin-screw kneading extruder is preferable. . It should be noted that the particles to be added may be subjected to treatments such as crushing, dispersing, classifying, and filtering, if necessary.

As a method for controlling the content of particles, a master raw material containing a high concentration of particles is prepared by the above-described method, and the master raw material is diluted with a raw material containing substantially no particles at the time of film formation. A method of adjusting the particle content is effective. The surface roughness of the layer A of the film thus obtained is Ra
Is 0.030 to 0.50 μm, preferably 0.040
To 0.40 μm, more preferably 0.050 to 0.3
It is in the range of 0 μm. When Ra is less than 0.030 μm,
The problem of deterioration of handleability due to scratches and blocking of films occurs. When Ra exceeds 0.50 μm, the quality of photographic images is deteriorated, which is not preferable. A photographic image is formed on a surface having such a smooth surface, but the back surface is usually in a state in which some print record or description is usually made, and for example, it is possible to write with a pencil. Is convenient. Therefore, it is preferable that the opposite surface of the A layer having a smooth surface is roughened. Therefore, the surface roughness Ra of the opposite surface of the smooth A layer is preferably 0.1 μm or more, more preferably 0.2 μm or more.

The laminated film of the present invention has a structure in which the A layer is laminated on one side or both sides of the B layer. When the A layer is present on one side, that is, in the case of the A / B structure, the smooth surface is the A layer. If A layers are provided on both sides, A / B /
Although the structure is A, the thickness of the A layer on one side is increased to form a flat surface, and the thickness of the A layer on the other side is decreased to reflect the influence of the fine bubbles existing in the B layer and thus the surface roughness. Can be adopted.

Further, by providing layers other than A and B, for example, A /
A method of increasing the surface roughness of the C layer by adopting a B / C structure can also be adopted. In short, in the present invention, it is necessary that there is an A layer having a smooth surface constituting one side of the film and a B layer containing fine bubbles, and the opposite surface of the A layer is roughened. Is.

In the case of the A / B structure, if the surface of the layer A is made smooth, the layer B contains fine bubbles and the surface becomes rough, which is convenient for obtaining the film of the present invention. However, since the two layers have different shrinkage characteristics, when this film is used, a problem may occur in that curling occurs due to heat. Therefore, it is preferable to form a layer containing no bubbles also on the surface opposite to the A layer. Therefore, it is preferable to form a film having an A / B / A structure in which a thin layer made of the same raw material as the A layer is provided. It is preferable in terms of prevention. Similarly, the A / B / C structure is also preferable in terms of curl prevention, but if a large amount of particles are contained in order to roughen the C layer, the particles are likely to fall off. In order to prevent such a problem, even when the C layer is formed, it is preferable that the thickness of the C layer is thin, for example, about 3 μm or less so that the B layer has an influence on roughening.

A constituting the low roughness surface of the film of the present invention
The surface of the layer preferably has a high degree of whiteness in view of the quality of the photographic image, and specifically, it is necessary that the b value is less than 2.0. When the b value is 2.0 or more, the color of the photographic image is affected and the quality of the photographic paper is deteriorated.

In order to achieve such whiteness, the A layer polyester preferably contains a whitening particle and a fluorescent brightening agent. Examples of such optical brighteners include trade names "Ubitech" OB, MD (manufactured by Ciba Geigy), "O
B-1 ”(manufactured by Eastman) and the like. on the other hand,
The surface opposite to the layer A does not require a particularly high degree of whiteness.

In addition to such whiteness requirements, the high glossiness of the surface of layer A provides particularly good photographic image quality. Specifically, the glossiness is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more. 30% gloss
If it is less than 1, the resolution of the photographic image may be insufficient and the quality may be deteriorated.

In the present invention, it is advantageous in terms of raw material cost to blend a recycled raw material for the film itself into the film. Since such a recycled raw material contains a polymer that is incompatible with the polyester, it is preferably blended only with the raw material forming the B layer. Further, as a more advantageous method in terms of raw material cost, it is possible to use an inexpensive polyester raw material for the B layer. Examples of such a raw material include recycled polyester and direct-weight polyester generated from various uses. In particular, since the layer B contains bubbles and imparts a large surface roughness, it does not matter if the raw material contains large particles or has some color. Therefore, B occupies most of the film
The range of polymers that can be used in the layer is extremely wide, and the cost advantage is great.

On the other hand, the use of such regenerated polymer is limited for the raw material of the layer A which needs to maintain a high whiteness. A
The content of the regenerated raw material in the layer depends on the degree of coloring, but it is usually preferable not to exceed 40%.

The concentration of terminal carboxyl groups of the polyester forming the B layer of the film of the present invention is preferably 45 equivalents / ton or more, more preferably 50 equivalents / ton or more. When the terminal carboxyl group concentration is 45 equivalents / ton or more, the reason is not always clear, but the size of the fine bubbles formed in the layer B becomes uniform, and the film density is easily controlled, thus improving productivity. Is advantageous in that.

Further, the intrinsic viscosity of the B layer polyester is
It is usually 0.50 or more, more preferably 0.53 or more. When the intrinsic viscosity is less than 0.50, film breakage is likely to occur during film formation, and the size of bubbles becomes nonuniform, which makes it difficult to control the density, resulting in a decrease in productivity. On the other hand, the upper limit of the intrinsic viscosity is usually 1.0 or less from the viewpoint of productivity during polymer production. The intrinsic viscosity of the A layer polyester and the intrinsic viscosity of the B layer may be the same or different, but when the surface layer has a higher intrinsic viscosity than the inner layer, breakage during film formation is prevented, and It is preferable because the particles do not easily fall off the surface.

Next, the method for producing the film of the present invention will be specifically described. In the present invention, a coextrusion method is used as a method for obtaining a laminated film. Hereinafter, an example of the coextrusion method will be described.

The polyester raw material constituting each layer is supplied to an extruder for coextrusion lamination. That is, two or more extruders, two or three or more layers of multi-manifolds or feed blocks are used for lamination, and extruded as a molten sheet from a slit-shaped die. A / B /
In the case of the film having the structure A, the polymers forming the A layer and the B layer are extruded from one extruder and divided in the middle of the melt line. A quantitative feeder such as a gear pump is installed on the melt line after the division, and the flow rates of the polymer for A layer and the polymer for B layer are adjusted to be laminated on both sides of the B layer. The thickness of each is controlled by its flow rate. Of course, installing a gear pump in the melt line of B layer polymer
It is effective in adjusting the thickness.

Next, the molten sheet extruded from the die is rapidly cooled and solidified on the rotary cooling drum so as to have a temperature not higher than the glass transition temperature to obtain a substantially non-oriented sheet in an amorphous state. In this case, in order to improve the flatness of the sheet,
It is necessary to enhance the adhesion between the sheet and the rotary cooling drum, and in the present invention, the electrostatic application adhesion method and / or the liquid coating adhesion method are preferably adopted.

The electrostatic application adhesion method is usually a method in which a linear electrode is placed on the upper surface of the sheet in a direction orthogonal to the flow of the sheet, and a DC voltage of about 5 to 10 kV is applied to the electrode to statically apply the sheet. This is a method of applying an electric charge to improve the adhesion to the drum. In addition, the liquid application contact method is a method for improving the adhesion between the drum and the sheet by uniformly applying the liquid to the whole or part of the surface of the rotary cooling drum (for example, only the portions that contact both ends of the sheet). Is. In the present invention, both may be used together if necessary.

In the present invention, the sheet thus obtained is stretched at least uniaxially to form a film. As described above, the fine bubbles in the B layer of the present invention are
Since it can be produced by such stretching, and to appropriately satisfy the strength and dimensional stability of the film,
It is necessary to stretch under suitable conditions.

The biaxial stretching conditions will be specifically described.
The unstretched sheet is preferably in the temperature range of 70 to 150 ° C., more preferably 75 to 130 ° C., and is first unidirectionally stretched by a roll or tenter type stretching machine to 3.0 to 7
Stretching twice, preferably 3.2 to 6 times. Next, it is stretched in a direction orthogonal to the first stage at a temperature range of preferably 75 to 150 ° C., more preferably 80 to 140 ° C. by a factor of 3.2 to 7 times, preferably 3.5 to 6 times, and biaxially stretched. Obtain an oriented film. A method in which unidirectional stretching is performed in two or more stages can be used, but in that case as well, it is desirable that the final stretching ratio falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area ratio becomes 10 to 40 times.

The film thus obtained is used in the range of 150 to 25
Heat treatment is performed at 0 ° C. for 30 seconds or less, limited shrinkage, or constant length for 1 second to 5 minutes. After biaxial stretching, another 11
A method of re-stretching 1.05 to 2.0 times in the machine direction at a temperature of 0 ° C. to 180 ° C. and then performing heat treatment can also be adopted. On this occasion,
It is also possible to appropriately adopt a method such as heat setting before re-longitudinal stretching, longitudinal relaxation after re-longitudinal stretching, or fine-length longitudinal stretching before or after re-longitudinal stretching. Further, re-stretching may be performed in the transverse direction as well. In addition, various surface treatments may be performed in the film forming process as needed.

In the film of the present invention, in order to enhance the adhesiveness with the photographic image forming layer, it is preferable to provide two layers on the film surface, that is, a primer layer and a gelatin easy-adhesion layer provided thereon. The coating layer may be provided in the film production process or may be applied after the film production.

The primer layer coating agent is preferably a water-soluble and / or water-dispersible polyester resin. For example, the dicarboxylic acid component is a blend of terephthalic acid or isophthalic acid and sodium sulfoisophthalic acid. , A copolyester whose glycol component is ethylene glycol.

The amount of the copolyester resin in the coating solution is usually 0.5 to 15% by weight, preferably 5 to 10% by weight. The thickness of the coating layer is usually in the range of 0.001 to 1 μm as the final dry thickness, and preferably 0.0
It is 1 μm.

The primer layer coating liquid in the present invention includes
An anionic surfactant or a cross-linking agent may be added for surface modification. Examples of the anionic surfactant include sodium lauryl sulfonate, sodium dodecylbenzene sulfonate, sodium alkyl allyl ether sulfonate, and the like, and examples of the cross-linking agent include melamine formaldehyde. The amount of these additives is in the range of 1 to 15%, further 2 to 3%, based on the copolyester.
Is preferred.

The coating agent for forming the gelatin easy-adhesion layer is
A water-soluble and / or water-dispersible acrylic resin is preferable, in which a hard monomer that can be a raw material for an acrylic resin such as alkyl acrylate, alkyl methacrylate, styrene, acrylonitrile or vinyl acetate is copolymerized. And these ingredients are 3
The water-soluble or water-dispersible resin is preferably 0 to 100 mol% and further contains 70 to 5 mol% of a copolymerizable vinyl monomer component having a functional group.

Examples of the alkyl group of alkyl acrylate and alkyl methacrylate include a methyl group and n-
Examples thereof include a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a 2-ethylhexyl group, a lauryl group, a stearyl group and a cyclohexyl group.

The vinyl monomer which is copolymerizable and has a functional group has a functional group which improves the adhesiveness to the base material or the functional layer or the affinity to other coating agents. Those are preferable. The preferred functional group is a carboxyl group, or a salt thereof, an acid anhydride group, a sulfonic acid group or a salt thereof, an amide group or an alkylolated amide group,
An amino group (including a substituted amino group), an alkylolated amino group or a salt thereof, a hydroxyl group, an epoxy group and the like. Particularly preferred are a carboxyl group or a salt thereof, an acid anhydride group, an epoxy group and the like. Two or more kinds of these groups may be contained in the resin.

As the vinyl-based monomer having a functional group to be copolymerized, the following compounds having a functional group such as a reactive functional group, a self-crosslinking functional group and a hydrophilic group can be used. Examples of the compound having a carboxyl group or a salt thereof, or an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid,
Examples thereof include maleic acid, metal salts of these carboxylic acids with sodium and the like, ammonium salts and maleic anhydride. Examples of the compound having a sulfonic acid group or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium, ammonium salts and the like.

Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylol acrylamide, methylol methacrylamide,
Examples thereof include ureido vinyl ether, β-ureido isobutyl vinyl ether, and ureido ethyl acrylate.

Examples of the compound having an amino group or an alkylolated amino group or a salt thereof include diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether and 2
-Aminobutyl vinyl ether, dimethylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, those obtained by methylating their amino groups, alkyl halides; those obtained by quaternization with dimethylsulfate, sultone and the like.

Examples of the compound having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β
-Hydroxypropyl methacrylate, β-hydroxy vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate and the like can be mentioned.

Examples of the compound having an epoxy group include glycidyl acrylate and glycidyl methacrylate. In addition to the above compounds, the following compounds may be used in combination. That is, butyl vinyl ether, maleic acid mono- or dialkyl ester, fumaric acid mono- or dialkyl ester, itaconic acid mono- or dialkyl ester, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl pyridine, vinyl pyrrolidone, vinyl trimethoxysilane and the like can be mentioned. Are not limited to these.

The water-soluble and / or water-dispersible acrylic resin in the present invention is preferably a coating agent using water as a medium for safety and hygiene, but within the scope of the present invention, the water-soluble acrylic resin is water-soluble. Alternatively, an organic solvent may be contained as an auxiliary agent for the water-dispersible resin. When water is used as the medium, it may be a coating agent forcibly dispersed with a surfactant or the like, but is preferably a hydrophilic nonionic component such as a polyether or a cation such as a quaternary ammonium salt. It is a self-dispersion type coating agent having a functional group, more preferably a water-soluble or water-dispersible coating agent having an anionic group. The water-soluble or water-dispersible coating agent having an anionic group is a compound having a compound having an anionic group bound to a resin by copolymerization or grafting, and sulfonic acid, carboxylic acid, phosphoric acid and their From salt, etc.
It is selected appropriately.

The amount of the anionic group of the water-soluble or water-dispersible coating agent having an anionic group is 0.05% by weight to 8%.
Weight percent is preferred. When the amount of the anionic group is less than 0.05% by weight, the water solubility or water dispersibility of the resin tends to deteriorate, and when the amount of the anionic group exceeds 8% by weight, the water resistance of the undercoat layer after coating may be poor. However, there is a tendency that the films are likely to stick to each other by absorbing moisture.

The gelatin easy-adhesion layer coating solution of the present invention may contain particles for improving the slipperiness of the coating layer. As the type of particles, inorganic particles, organic particles and the like can be used.

Inorganic particles such as silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, calcium phosphate, titanium oxide, barium sulfate, carbon black, molybdenum sulfide and antimony oxide sol are used as organic particles such as polystyrene and polyethylene. , Fine particles with or without a cross-linking agent composed of a homopolymer or a copolymer of polyamide, polyester, polyacrylic acid ester, epoxy resin, polyvinyl acetate or polyvinyl chloride, and fine particles such as silicone resin and fluororesin. .

The gelatin easy-adhesion layer coating solution of the present invention is methylolated or alkylolized as a cross-linking agent in order to improve the adhesion (blocking property), water resistance, solvent resistance and mechanical strength of the coating layer. Urea, melamine, guanamine, acrylamide, polyamide, etc. compounds, isocyanate compounds, epoxy compounds, aziridine compounds, silane coupling agents, titanium coupling agents, zirco-aluminate coupling agents, It may contain an oxide, a thermally and photoreactive vinyl compound, a photosensitive resin, and the like.

Further, if necessary, an antifoaming agent, a coating property improving agent, a thickening agent, an antistatic agent, an organic lubricant, an antioxidant,
It may contain an ultraviolet absorber, a foaming agent, a dye, a pigment and the like. Further, the coating liquid of the present invention contains, in addition to the acrylic coating agent of the present invention, another type of acrylic resin, urethane resin, ester resin, vinyl resin or the like for improving the coating liquid or the coating layer. You may have.

The proportion of the water-soluble and / or water-dispersible acrylic resin that can be used in the present invention in the coating layer is preferably 60% or more, more preferably 70% or more, and most preferably 80% in terms of solid content. % Or more. When the water-soluble and / or water-dispersible acrylic resin content is low, the desired adhesive performance of the present invention may not be exhibited.

The thickness of the coating layer is usually in the range of 0.01 to 2 μm as the final dry thickness, preferably 0.02 to 2 μm.
It is in the range of 1 μm, more preferably 0.03 to 0.
It is in the range of 2 μm. A thick coating layer is not preferable because the films stick to each other. However, if the thickness of the coating layer is thin, it is difficult to obtain a uniform coating layer, and thus uneven coating tends to occur on the product.

A reverse roll coater, a gravure coater, a rod coater shown in "Coating Method" by Yuji Harasaki, Maki Shoten, 1979, is used as a method for applying each coating solution for the primer layer and the easy gelatin adhesion layer to a polyester film. A method of applying the coating liquid outside the biaxially stretched polyester film manufacturing process using an air doctor coater or a coating device other than these, more preferably a method of coating within the film manufacturing process. As a coating procedure in the film manufacturing process, a method of first coating the first layer (primer layer) and then drying and then coating the second layer (easy adhesion layer of gelatin) and drying may be used. The coating method of each layer includes, after die extrusion, coating on a rapidly solidified polyester unstretched film, coating on a uniaxially stretched polyester film, or coating on a biaxially stretched polyester film, according to the above order. , Any combination of these is possible. In the present invention, an antioxidant, a heat stabilizer, a lubricant, a polyester, or an incompatible polymer, if necessary, in the polymer.
You may mix additives, such as an antistatic agent, a dye, and a pigment.

[0066]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The evaluation methods in Examples and Comparative Examples are as follows. Further, all "parts" in the component ratios shown in the examples are "parts by weight".

(1) Layer Thickness of Each Layer The film cross section was observed with a transmission electron microscope (TEM). That is, a small piece of a film sample was embedded in a resin in which an epoxy resin was mixed with a curing agent and an accelerating agent, and a section having a thickness of about 200 nm was prepared with an ultramicrotome, and used as an observation sample. A micrograph of a cross section of the obtained sample was taken using a transmission electron microscope H-9000 manufactured by Hitachi Ltd., and the thickness of each layer was measured. However, the acceleration voltage is 300 kV, and the magnification depends on the outermost layer thickness.
It was set in the range of 10,000 times to 100,000 times. The thickness was measured at 50 points, 10 points from the thickest value and 10 points from the thinnest value were deleted, and 30 points were averaged to obtain the measured value.

(2) Film Density (g / cm ³ ) A square sample of 10 cm × 10 cm was cut out from an arbitrary portion of the film and weighed. Next, the thickness at 9 arbitrary points was measured with a micrometer, and the weight per unit volume was calculated from the average value and the weight. The number of measurements was 5 and the average value was taken as the film density. After measuring each layer thickness, the A layer on the film surface was cut with a microtome, and the density of the A layer was measured using a density gradient tube,
The density value of each layer was calculated.

(3) Whiteness (b value) Color Analyzer TC-1800 manufactured by Tokyo Denshoku Co., Ltd.
Using the MKII type, the color tone (L, a, b) of the film was measured according to the method of JIS Z-8722, and the b value was taken as the whiteness. A large b value on the + side indicates that the yellow tint is strong. The measurement was performed at three points, and the average value was used as the measured value.

(4) Centerline average roughness (Ra) The average roughness was measured as follows using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory Ltd. That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, and the center line of the extracted portion is taken as the x-axis, and the direction of longitudinal magnification is taken as the y-axis. When represented by f (x), the value given by the following equation was represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portions obtained from the 10 section curves obtained from the surface of the sample film. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08.
mm.

[0071]

## EQU1 ## Ra = (1 / L) ∫ ₀ ^L │f (x) │dx

(5) Glossiness (%) The glossiness was measured using a gloss meter 1001DP type manufactured by Nippon Denshoku Co., Ltd. according to the method of JIS Z-8741. The reflectance of the material was calculated based on the reflection angle of the black standard plate at the incident angle and the reflection angle of 60 degrees, and was taken as the glossiness.

(6) Average particle size and particle size distribution value of particles Centrifugal sedimentation type particle size distribution measuring device (SA-CP manufactured by Shimadzu Corporation)
Equivalent spherical distribution measured by type 3) 5
The particle size of 0% was taken as the average particle size.

(7) Intrinsic viscosity of polymer [η] (dl
/ G) Polymer-1 g phenol / tetrachloroethane = 50
Dissolve in 100 ml of a mixed solvent of 50/50 (weight ratio) and
It was measured at 0 ° C.

(8) Carboxyl end group concentration (equal amount /
Tons) A. The method of Conix [Makromol. Che
m. , 26, 226 (1958)].

(9) Melt flow index M
FI (g / 10 minutes) Measured according to JIS K-6758-1981. The higher this value, the lower the melt viscosity of the polymer.

(10) Practical characteristics as photographic paper A gelatin emulsion containing a photoconductor is applied to one side of a film to form a photosensitive layer, which is exposed and developed to form an image.
The quality of the obtained image was evaluated for the following items.

(I) Resolution Rank A: High resolution and high quality Rank B: Somewhat inferior resolution, but practically acceptable Rank C: Inferior resolution and practically problematic

(Ii) Contrast Rank A: An image with clear contrast and high quality can be obtained. Rank B: The contrast is slightly inferior in sharpness, but practical. Rank C: Contrast is low and image quality is inferior.

(Iii) Color tone Rank A: good color tone Rank B: poor color tone due to the influence of yellowness

(2) Evaluation of adhesiveness Adhesiveness with gelatin 5% of photographic gelatin P-2225 manufactured by Nitta Gelatin Co., Ltd.
An aqueous solution is prepared, coated on the surface of the film so that the dry coating thickness is 0.6 μm, and dried with hot air at 80 ° C. for 1 minute,
Obtain an evaluation film. The film for evaluation has a temperature of 23 ° C,
After the temperature and humidity were controlled at a humidity of 50% RH for 24 hours, the Nichiban Co., Ltd. cello tape (18 mm
(Width) is attached to a length of 7 cm so that air bubbles do not enter, and a constant load is applied on this by a manual load roll. The film is fixed, one end of the cellophane tape is connected to a weight of 500 g, and the peeling test in the 180 degree direction is started after the weight naturally drops at a distance of 45 cm. Adhesiveness is evaluated and displayed according to the following three-stage criteria. ◯: Ink layer peeling area is less than 10% and good Δ: Ink layer peeling area is good in 10 to 50% x: Ink layer peeling area is more than 50% and defective.

Adhesiveness to polyvinyl alcohol (PVA) (2) Except that a 5% aqueous solution of PVA with a saponification degree of 88% manufactured by Nippon Synthetic Chemical Industry Co., Ltd. is used as the ink (4).
Adhesion is evaluated in the same manner as.

Adhesiveness to polyvinyl butyral (PVB) (2) Butvar B-, which is a PVB manufactured by Mitsubishi Chemical Co., Inc., in which 80 mol% of the hydroxyl groups of completely saponified PVA are butyralized using butyraldehyde as an ink.
Adhesion is evaluated in the same manner as in (2) except that 98 (trade name) 5% ethanol solution is used.

Adhesiveness to Cellulose (2) Except for using a 2% aqueous solution of hydroxypropylmethylcellulose Marporose MP (trade name) manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. as the ink (4) The adhesiveness is evaluated in the same manner as in (1).

(3) Evaluation of Adhesiveness Polyester films are superposed, and 10 kgf / cm by a press in a thermo-hygrostat at a temperature of 40 ° C. and a humidity of 80% RH.
The film having a width of 10 cm, which was treated for 20 hours while applying a load of 2, was measured according to the method of peeling with a piano wire of ASTM-D-1893, and judged according to the following criteria. ◯: less than 30 gf Δ: 30 gf or more and less than 100 gf x: 100 gf or more

<Production of Polyester Resin> 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor,
The temperature was raised by heating and methanol was distilled off to carry out an ester exchange reaction. It took 4 hours from the start of the reaction to raise the temperature to 230 ° C. to substantially end the transesterification reaction.

Then, silica particles having a particle diameter of 1.5 μm.
5 parts was added as ethylene glycol slurry. After the slurry was added, 0.03 part of phosphoric acid and 0.04 part of antimony trioxide were further added, the reaction system was gradually depressurized, the temperature was raised to carry out a polycondensation reaction for 4 hours, and a polyester having an intrinsic viscosity of 0.62 ( a) was obtained.

Separately, the transesterification reaction and the polycondensation reaction are carried out in the same manner as described above except that the above silica particles are not added, and the intrinsic viscosity is 0.7 which does not substantially contain inert particles.
A polyester (b) of 0 and a polyester (c) of intrinsic viscosity 0.64 were obtained. 35 parts of titanium dioxide particles having an average particle size of 0.30 μm and 55 parts of polyester (b) were blended using a twin-screw extruder to obtain polyester (d). The intrinsic viscosity of polyester (d) was 0.59. Similarly, using a twin-screw extruder, a polyester (e) containing 1% by weight of OB-1 as an optical brightener and having an intrinsic viscosity of 0.60 was produced.

The coating agents used in the examples are as shown below. Primer coating agent Copolyester (isophthalic acid and 5-sodium sulfoisophthalic acid in a molar ratio of 9: 1, and all of these acid components and ethylene glycol in an equivalent molar ratio)
10%, hexamethoxymethylmelamine (Cymel 303 manufactured by American Cynamid) 1.0%, surfactant (Rhodacal L manufactured by Rhone Poulin)
DS-10) 0.284%, fluorinated surfactant (3M
Fluorad FC-170C) 0.07%,
Colloidal silica (Nalco Chemical Co. Nalco
1060) 1.2% and deionized water 87.446
% Coating agent

Composition of gelatin easy-adhesion layer Solid content weight% of coating agent C1: X1 = 100 C2: X2 = 100 C3: X3 = 100 C4: X1 / Y1 = 60/40 (where X1: methyl methacrylate (105 ° C. ) 4
Acrylic resin aqueous dispersion consisting of 5 mol%, n-butyl acrylate (-54 ° C) 30 mol%, styrene (100 ° C) 20 mol%, and acrylic acid (106 ° C) 5 mol%; X2: methyl methacrylate (105 C) 50 mol%, n-butyl methacrylate (-54 C) 35 mol%, 2-hydroxyethyl methacrylate (55 C) 1
Acrylic resin aqueous dispersion consisting of 0 mol% and methacrylic acid (130 ° C) 5 mol%, X3: ethyl acrylate (-22 ° C) 50 mol%, n-butyl methacrylate (-54 ° C) 35 mol%, 2- Hydroxyethyl methacrylate (55 ° C) 10 mol%, methacrylic acid (130
Acrylic resin water dispersion consisting of 5 mol%) parentheses represent Tg of homopolymer; Y1: terephthalic acid 3
Polyester resin water dispersion consisting of 5 mol%, sodium sulfoisophthalic acid 5 mol%, ethylene glycol 49 mol% and diethylene glycol 1 mol%)

Comparative Example 1 Polyester (c), polyester (d) and polyester (e) were blended at a ratio of 85: 10: 5 (weight ratio) to prepare a polyester raw material. To 100 parts of the polyester raw material, M. F. I. Blending 12 parts of crystalline polypropylene homopolymer chip of No. 5,
Furthermore, silicone-based surfactant (trade name; SH193
A raw material containing 0.3 part of Toray Silicone Co., Ltd. was melted at 290 ° C. by an extruder and extruded on a sheet on a cooling drum at 40 ° C. to obtain an amorphous sheet having a thickness of 1.3 mm. .

Then, the primer layer coating agent was applied to one surface of the amorphous sheet. Then, after stretching 3.2 times at 85 ° C. in the film flow direction (longitudinal direction),
1 gelatin easy-adhesion layer coating agent was applied. Further, the film was stretched in the transverse direction 3.3 times at 110 ° C. and heat-treated at 240 ° C. for 5 seconds to obtain a biaxially oriented film. The total thickness of the film was 170 μm.

A photographic image forming layer was applied on the surface of the coating layer of the obtained film to obtain photographic paper, and its characteristics were evaluated. Since the fine bubble-containing layer was used as the surface, the roughness of the film surface was too large, and the surface shape affected the photographic image, resulting in poor sharpness and resolution.

Example 1 Scrap generated during the production of the film of Comparative Example 1 was melt-extruded by a twin-screw extruder to form recycled chips, which was used as a recycled raw material (f). Polyester (a), polyester (c), polyester (d), and polyester (e) were used as A layer raw materials, respectively, at 20: 35: 40: 5.
The polyester raw material blended in the ratio of (weight ratio) was used. Further, as the B layer raw material, polyester (c), recycled raw material (f), M. F. I. 50:40:10 (weight ratio) of the crystalline polypropylene homopolymer of 5 respectively
Was blended at a ratio of 0.3% by weight of SH193 and used. A layer raw material and B layer raw material are melt extruded by different extruders respectively, and the extrusion amount of each layer is adjusted to form an amorphous sheet having a total thickness of 1.2 mm and having a two-layer structure of A / B. Obtained. Two-step coating on the surface of layer A, stretching,
The heat treatment conditions were the same as in Comparative Example 1, and the total thickness was 170 μm.
A biaxially stretched laminated film of m was obtained. The layer A thickness was 8 μm. When a photographic image forming layer was provided on the surface of layer A (coating layer) of the film and evaluated, high quality image formation was recognized. Further, the surface of the B layer can be sufficiently written with an HB pencil, which is also a preferable characteristic.

Example 2 The same raw material as in Example 1 was used for the A layer, and the weight ratio of the polyester (c), the recycled raw material (f) and the polypropylene of the B layer was 4%.
A laminated film was produced in the same manner as in Example 1 except that the ratio was 3:40:17 and the structure was a three-layer structure of A / B / A. However,
The thickness of A layer on one side was 14 μm (A1 layer), the thickness of A layer on the other side was 1 μm (A2 layer), and the thickness of the entire film was 170 μm. When a photographic image forming layer was provided on the surface of the A1 layer and evaluated, high quality image formation was recognized. On the other hand, on the surface of the A2 layer, writing with a pencil of HB was slightly less clear than in the case of Example 1, but was sufficiently possible.

Comparative Example 2 The layer A raw materials were 20:40: polyester (a), polyester (c) and polyester (d), respectively.
A microcell-containing laminated polyester film was obtained in the same manner as in Example 1 except that the polyester raw material was blended at a ratio of 40 (weight ratio). A layer thickness is 13 μm,
The total film thickness was 170 μm. This film was affected by the fact that it did not contain a fluorescent whitening agent, and the surface of the A layer was inferior in whiteness, and was not suitable for use as photographic paper.

Comparative Example 3 A laminated polyester film containing fine bubbles was obtained in the same manner as in Example 1 except that only the polyester (c) was used as the layer A raw material. The layer A thickness was 20 μm, and the total film thickness was 170 μm. Since the surface of the layer A of the film was extremely flat, scratches were generated on the surface of the layer A due to contact with a roll during film formation and friction during winding, which adversely affected the photographic image.

Comparative Example 4 Polyester (a), polyester (c), polyester (d) and polyester (e) were each added in a ratio of 20: 3.
A polyester raw material blended at a ratio of 5: 40: 5 (weight ratio) was used, and a film-forming condition and a coating method were the same as in Comparative Example 1 to produce a 160-μm-thick single-layer film containing no fine bubbles. Since the film has high rigidity and no cushioning property, it is inferior in handleability as photographic paper,
There was also no writability on the back side, and it was less suitable than the film of the present invention for this application. The measured physical properties and practical evaluation results of the films produced in Examples and Comparative Examples are summarized in Tables 1 to 3 below.

[0099]

[Table 1]

[0100]

[Table 2]

[0101]

[Table 3]

Next, examples of evaluation of easy adhesion of gelatin are shown below. The primer layer was applied to one surface of an amorphous sheet obtained in the same manner as in Example 1 (not applied in Comparative Example 5).
Then, in the film flow direction (longitudinal direction) at 85 ° C. for 3.2.
After being double-stretched, each gelatin easy-adhesion layer coating agent shown in Table 4 below was applied (not applied in Comparative Example 5). Further, the film was stretched in the transverse direction 3.3 times at 110 ° C. and heat-treated at 240 ° C. for 5 seconds to obtain a biaxially oriented film. The total thickness of the film was 170 μm (Examples 3 to 6, Comparative Example 5). The coating layer of the obtained film was evaluated for adhesiveness and adhesion, and the results are summarized in Table 2.

[0103]

[Table 4]

[0104]

The biaxially oriented laminated polyester film of the present invention comprises gelatin, polyvinyl alcohol (PVA),
It has excellent adhesion to functional layers containing highly water-soluble polymers such as polyvinyl butyral (PVB) and cellulose, and because it contains a large number of closed fine cells, it is lightweight and has cushioning properties, and its surface is smooth. It has a high whiteness, and when it is used as an ink image-receiving film, a plate-making film, especially a base film for photographic printing paper, it can highly satisfy the image quality,
Moreover, it is excellent in productivity and cost, and its industrial value is extremely large.

Claims (3)

[Claims] 1. A contains a large number of fine closed cells on one side or both sides of the polyester B layer density of 0.40~1.30g / cm ^3, density of 1.30 g / cm ³ greater than the polyester A layer Which is a film obtained by laminating, and the b value of the surface A of the outermost layer on one side is less than 2.0,
The surface roughness Ra is 0.030 to 0.50 μm, the surface roughness Ra of the other outermost surface layer is larger than Ra of the outermost surface layer, and a gelatin easy-adhesion layer is provided on the surface of the low roughness side. A polyester film containing fine bubbles. 2. The laminated polyester film containing microbubbles according to claim 1, wherein the gelatin easy-adhesion layer is composed of two coating layers. 3. A micro-cell-containing laminated polyester film for photographic paper according to claim 1 or 2.