JP4407902B2 - Biaxially stretched laminated polypropylene film and use thereof - Google Patents

Description

The present invention relates to a biaxially stretched laminated polypropylene film excellent in surface smoothness, concealability, surface gloss, blocking resistance and laminate suitability, and uses thereof.

Biaxially stretched polypropylene film (hereinafter sometimes referred to as “OPP film”)
Utilizing its excellent properties such as transparency, mechanical strength, and rigidity, it is used in a wide range of fields including packaging materials. Moreover, while improving the concealability of the OPP film, as a method of imparting surface glossiness, an incompatible material such as an organic material such as nylon or an inorganic material such as glass beads is added to polypropylene as a core material, A biaxially stretched film (Patent Document 1) in which the surface layer is an additive-free polypropylene layer has been proposed.

On the other hand, in recent years, thermal printers, particularly thermal transfer printers capable of printing clear full-color images, have attracted attention. The thermal transfer printer includes a thermal transfer sheet having a dye layer containing a dye that migrates by sublimation or melt diffusion due to heat, and an image receiving layer (hereinafter referred to as a “receiving layer”) that receives the dye of the thermal transfer sheet on one side of a film support. The dye layer and the receiving layer are superposed on each other, and the dye at the desired location of the dye layer is transferred onto the receiving layer by a predetermined concentration by heat supplied from a thermal head or the like to form an image. To do. In particular, the dye thermal transfer method using a dye having sublimation property is capable of printing a digital image, and therefore, replacement with a silver salt photograph is progressing. In addition, as the number of pixels of digital images increases, higher quality prints are being demanded. Furthermore, it is required to increase the printing speed of a thermal transfer printer, and a thermal transfer receiving sheet with higher sensitivity is required.

In order to meet such demands, in order to have heat insulation, to have a gap and to increase the number of pixels,
There has been proposed a thermal transfer sheet using a biaxially stretched polypropylene film having a thermoplastic resin layer having a surface center line roughness of 0.7 μm or less (Patent Documents 2 to 4). Further, a biaxial film having a surface layer having a three-dimensional center plane roughness of 0.3 μm or less and a surface glossiness of 80% or more on at least one surface of a biaxially stretched form base material containing inorganic fine powder such as calcium carbonate. A stretched film (Patent Document 5) has been proposed.
However, the surface roughness specifically described in the above patent document is 0.08 to 0.6 μm.
m, which is insufficient for printing a high-pixel-value digital image that has been rapidly developed in recent years, and there is a problem that the image tends to be rough. Further, when printing is performed using a thermal transfer receiving sheet, there is a drawback that the printing portion of the thermal transfer receiving sheet is recessed due to heat from the thermal head, and the appearance is deteriorated. In particular, the higher the density of printing, the larger the dent,
An image having a high contrast has a problem that the unevenness is remarkable and the appearance is very poor. Also,
It is difficult to improve the surface smoothness while maintaining the concealment.

JP 58-147348 A (pages 1 to 3) JP 63-222891 A (page 3) JP-A-7-76186 (2nd page) JP 7-125453 A (page 2) Japanese Patent Application No. 2000-127303 (2nd page)

Accordingly, an object of the present invention is to provide a biaxially stretched laminated polypropylene film particularly excellent as a support for an image receptor excellent in surface smoothness, concealability, surface glossiness, blocking resistance and laminate suitability, and such a biaxially stretched laminated polypropylene film. It is an object to provide an image receptor having a support as a support.

The present invention has been proposed in order to achieve the above object, and is characterized by having the following configuration.
That is, according to the present invention, 5 to 25% by mass of calcium carbonate having an average particle size of 0.5 to 5 μm and a 90% cumulative frequency particle size of 3 μm or less to 55 to 90% by mass of the propylene polymer (a1). And a biaxially oriented polypropylene film base layer (B) obtained from a propylene polymer composition (A) comprising an inorganic compound powder (a2) comprising 5 to 20% by mass of rutile titanium oxide treated with alumina A surface layer made of the propylene polymer (a1) is provided on one side of the surface, and the surface roughness (three-dimensional center surface average roughness SRa) is 0.3 to 0.7 μm and the glossiness is on the other side. A back layer composed of a polyolefin polymer composition (C) of 15% or less of a propylene polymer (c1) and an ethylene polymer (c2) is laminated, and the surface roughness of the surface layer (three-dimensional center) Surface average roughness It SRa) no 0.01 0.07 .mu.m, and a glossiness of 100% or more, the density is 0.43 to 0.85g / cm ^3, L * value is 95 or higher and haze of the biaxially oriented laminated polypropylene film A biaxially stretched laminated polypropylene film having 91 to 94% and a total light transmittance of 20% or less is provided.

The biaxially stretched laminated polypropylene film of the present invention is particularly excellent for use as a support for photographic paper for digital photo printers. In particular, an image receiving layer is formed on the polyurethane resin layer of the biaxially stretched laminated polypropylene film. Things are excellent as image receptors.

The biaxially stretched laminated polypropylene film of the present invention is excellent in surface smoothness, concealing property, surface gloss, blocking resistance and laminating suitability, as will be understood from Examples described later. Suitable as a body. In addition, the thermal transfer receiving sheet using the biaxially stretched laminated polypropylene film of the present invention can achieve higher image quality and higher sensitivity than conventional thermal transfer receiving sheets, has high gloss after printing, and has few dents in the printing area. It has the characteristics.

The present invention will be described in further detail.
[Propylene-based polymer composition (A)]
The propylene polymer composition (A) according to the present invention is a propylene polymer (a1) described later.
) Is added to the inorganic compound (a2), and the biaxially stretched polypropylene film substrate layer (B) is obtained by biaxially stretching the composition.
The amount of the inorganic compound (a2) added to the propylene-based polymer (a1) depends on the type of the inorganic compound and how much the haze, total light transmittance and density of the resulting biaxially stretched laminated polypropylene film are set. Although different, usually 10 to 45% by mass, preferably about 15 to 35% by mass is adopted.

By adding this inorganic compound (a2) to the propylene-based polymer (a1), the concealability, density, haze and total light transmittance of the biaxially stretched polypropylene film substrate layer (B) are adjusted to appropriate values. I can do it.
By using calcium carbonate and titanium oxide in combination, the density is 0.43 to 0.85.
g / cm ³ , more preferably 0.48 to 0.71 g / cm ³ , haze of 90% or more,
Preferably it is 91 to 94%, and the total light transmittance is 20% or less, preferably 7 to 16%.
A biaxially stretched laminated polypropylene film is obtained.

In addition to the inorganic compound powder (a2), the propylene-based polymer composition (A) according to the present invention includes a heat stabilizer, a weather stabilizer, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, Various additives such as antistatic agents, antifogging agents, pigments, dyes and the like that are generally known to be added to polyolefins may be added as long as the object of the present invention is not impaired.

<Propylene-based polymer (a1)>
The propylene polymer (a1) according to the present invention is a polyolefin resin that is generally produced and sold under the name of polypropylene, and usually has a density of 0.890 to 0.930 g /
cm ³ , MFR (ASTM D1238 load 2160 g, temperature 230 ° C.) 0.5 to 60 g / 10 min, preferably 0.5 to 10 g / 10 min, more preferably 1 to 5
A propylene homopolymer of g / 10 min, or a random copolymer of propylene and another small amount, for example, 5 mol% or less of an α-olefin such as ethylene, butene, hexene-1, and the like.

These propylene polymers (a1) may be one or more compositions, for example, a composition of a propylene homopolymer and a propylene / α-olefin random copolymer having different molecular weights. Good. Among these, a homopolymer of propylene or a random copolymer of 1 mol% or less and a polymer having high isotacticity is preferable because a biaxially stretched laminated polypropylene film having high rigidity can be obtained.
This propylene polymer (a1) is blended with the inorganic compound (a2) and biaxially stretched to form the biaxially stretched film base layer of the biaxially stretched laminated polypropylene film of the present invention. Even if it is the same as the propylene polymer (a1) used for the back layer,
May be different.

When the propylene polymer (a1) is used as a surface layer or a back layer of a biaxially stretched laminated polypropylene film, a heat resistance stabilizer, a weather resistance stabilizer, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, Various compounding agents usually added to polyolefins such as antistatic agents, antifogging agents, face amounts, and dyes may be added within a range not impairing the object of the present invention. Among them, the blocking inhibitor is 0.01 to 3.0% by mass, preferably 0.05 to 1%.
. When 0 mass% is added, a biaxially stretched laminated polypropylene film having antiblocking properties can be obtained. When the blending amount of the anti-blocking agent is less than 0.01% by mass, the anti-blocking effect of the obtained biaxially stretched laminated polypropylene film is not sufficient,
When it exceeds 3.0 mass%, the surface state of the obtained biaxially stretched laminated polypropylene film tends to deteriorate and the surface gloss tends to be impaired. Examples of such an antiblocking agent include silica, talc, mica, zeolite, inorganic compound particles such as metal oxide obtained by firing metal alkoxide, polymethyl methacrylate, melamine formalin resin, melamine urea resin, polyester resin, and the like. Organic compounds such as organic compound particles are used, and silica and polymethyl methacrylate are particularly preferably used from the viewpoint of antiblocking properties.

<Inorganic compound powder (a2)>
And an inorganic compound powder according to the present invention (a2), among inorganic compound powder, calcium carbonate and titanium oxide, rather preferable in that the biaxially oriented laminated polypropylene film excellent in unevenness without whiteness is obtained In the present invention, this calcium carbonate and titanium oxide are used in combination .

Further, by using calcium carbonate and titanium oxide in combination, the density is 0.43 to 0.
. 85 g / cm ³ , more preferably 0.48 to 0.71 g / cm ³ , haze of 90%
As described above, a biaxially stretched laminated polypropylene film having 91 to 94% and a total light transmittance of 20% or less, preferably 7 to 16% is obtained. The calcium carbonate preferably has an average particle size in the range of 0.5 to 5 μm, more preferably 1 to 1.5 μm. The maximum particle size is preferably 5 μm or less. The particle size of calcium carbonate is a value measured by a laser diffraction scattering method.

The amount of calcium carbonate and titanium oxide added to the propylene polymer (a1) is as follows:
The propylene polymer (a1) is preferably 55 to 90% by mass, more preferably 65 to 85% by mass, and calcium carbonate is preferably 5 to 25% by mass, more preferably 10 to 23% by mass, Titanium oxide is preferably 5 to 20% by mass, more preferably 5 to 15% by mass.
When the blending amount of calcium carbonate is less than 5% by mass, the concealability of the obtained biaxially stretched polypropylene film may be inferior, while when it exceeds 20% by mass, the appearance of the biaxially stretched polypropylene film may be impaired. Further, even if the blending amount of titanium oxide is less than 5% by mass, the concealability of the obtained biaxially stretched polypropylene film may be inferior. On the other hand, if it exceeds 20% by mass, the appearance of the biaxially stretched polypropylene film may be impaired. is there.

In the calcium carbonate according to the present invention, preferably the calcium carbonate particles having a particle size of 3 μm or less are 80% by mass (80% cumulative frequency particle size) or more, preferably 90% by mass (90% cumulative frequency particle) of the whole calcium carbonate. (Diameter) or more. When calcium carbonate having such a particle size distribution and average particle size is used, the size of voids in the film due to the calcium carbonate particles becomes uniform, so that the film has excellent hiding power and whiteness without unevenness, and the maximum width. There are almost no surface irregularities of 50 μm or more, for example, the number of surface protrusions is 50 (pieces / A4 size) or less, preferably 10 (pieces / A4 size) or less, most preferably 0 (pieces / A4 size).
Film is obtained.
In order to obtain a film having uniform voids in the film and excellent in hiding power and whiteness, the water content of calcium carbonate is more preferably 0.5% by weight or less. The water content of calcium carbonate is a value measured according to JIS K 5101.

Further, the surface of the particles of the calcium carbonate of the present invention may be treated with, for example, a higher fatty acid, preferably a higher fatty acid having 10 to 28 carbon atoms. By treating the particle surface with such a higher fatty acid, it is possible to prevent the occurrence of foreign matters, fish eyes and the like due to secondary aggregation of calcium carbonate, and a biaxially stretched laminated polypropylene film having a good appearance can be obtained. .

Specific examples of the higher fatty acid include decanoic acid, undecanoic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, and cellotine. Saturated higher fatty acids [CH ₃ (CH ₂ ) _n COOH, n = 8 to 26] such as acid and heptacosanoic acid; oleic acid (cis),
Elaidic acid (trans), cetreic acid, erucic acid (cis), brassic acid (tr
ans), unsaturated higher fatty acids such as linoleic acid, linolenic acid, arachidonic acid, and the like,
Of these, saturated higher fatty acids, particularly stearic acid, are preferred.

The titanium oxide preferably has an average particle size in the range of 0.1 to 0.5 μm. Titanium oxide is also called titanium white, and there are rutile type and ataanatase type.
The rutile type is preferable because of its high hiding power. In addition, when the titanium oxide according to the present invention is one whose surface is treated with alumina, the appearance of the resulting biaxially stretched laminated polypropylene film is excellent, and when the L * value is 95 or more, thermal transfer is performed. When used as a receiving sheet, it is preferable in that it gives a high-class feeling and can express the shade more clearly when recording an image with a shade. The L * value is the overlap of 10 films on white paper,
o Value measured using Eye (manufactured by Gretag Macbeth). In addition,
The particle diameter of titanium oxide is a value measured by a light scattering method.

[Polyolefin polymer composition (C)]
The polyolefin polymer composition (C) according to the present invention is a component constituting a back layer laminated on the other side of the biaxially stretched polypropylene film substrate layer (B), and is composed of polyethylene, polypropylene, polybutene, ethylene- It is a composition of one type or two or more types of polyolefin polymers or copolymers such as α-olefins. This polyolefin polymer composition (C) is a raw material for the back layer formed mainly for the purpose of imparting blocking resistance and laminate suitability to the obtained biaxially stretched laminated polypropylene film. Therefore, the composition is not particularly limited as long as the composition can impart blocking resistance and laminating suitability to the biaxially stretched laminated polypropylene film. ) A composition comprising 20 to 80% by weight, preferably 30 to 70% by weight and ethylene polymer (c2) 80 to 20% by weight, preferably 70 to 30% by weight, is excellent in blocking resistance and laminate suitability. This is preferable. The surface roughness (three-dimensional center plane average roughness SRa) of the back surface layer is preferably 0.3 to 0.7 μm, and the glossiness is preferably 15% or less.

In the polyolefin polymer composition (C) according to the present invention, a heat resistance stabilizer, a weather resistance stabilizer, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an anti-blocking agent, as long as the object of the present invention is not impaired. Various additives that are generally added to polyolefins such as antistatic agents, antifogging agents, pigments, and dyes may be added.

<Propylene polymer (c1)>
The propylene polymer (c1) according to the present invention is a polyolefin resin that is generally produced and sold under the name of polypropylene, and usually has a density of 0.890 to 0.930 g /
cm ³ , MFR (ASTM D1238 load 2160 g, temperature 230 ° C.) 0.5 to 60 g / 10 min, preferably 0.5 to 10 g / 10 min, more preferably 2 to 5
It is a random or block copolymer of a propylene homopolymer of g / 10 min or propylene and another small amount, for example, 10 mol% or less of an α-olefin such as ethylene, butene, hexene-1, and the like. These polymers are the above-mentioned propylene polymers (a1).
May be the same as or different from each other, and may be one or a blend of two or more.

<Ethylene polymer (c2)>
The ethylene-based polymer (c2) according to the present invention is an ethylene homopolymer or a random copolymer of ethylene and an α-olefin having 3 or more, preferably 4 or more, more preferably 6 or more carbon atoms, Polymers called so-called high pressure process low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) with a density in the range of 0.910 to 0.960 g / cm ³ . Such an ethylene polymer (c2) is usually an ethylene produced using a high pressure method, a Ziegler catalyst or a metallocene catalyst, and optionally propylene, butene-1, hexene-1, 4-methyl-pentene- 1
And a copolymer with an α-olefin such as octene-1. Its melt flow rate (MF
R) is in accordance with ASTM D1238, and the value measured at a temperature of 190 ° C. and a load of 2160 g is 0.05 to 30 g / 10 minutes, preferably 0.1 to 20 g / 10 minutes. These polymers may be used alone or in combination of two or more, but the above-mentioned propylene polymer (c1
)), It becomes excellent in blocking resistance and laminate suitability. At this time, it is preferable to use high-density polyethylene for at least a part of the ethylene polymer (c2).

[Polyurethane resin (D)]
The polyurethane-based resin (D) according to the present invention is formed on a surface layer made of the propylene-based polymer (a1) of the biaxially oriented polypropylene film base layer (B) defined in claim 6 of the claims. Polyester-based polyurethane, which are generally manufactured as dry laminates, water-based dry laminates, solvent-free laminates, and electron beam curable laminate adhesives, which are known as polyurethane adhesives, as film adhesives. Examples thereof include ether-based polyurethane and polyurethane polyurea resin. Such polyurethane-based resins may be either water-dispersed or solvent-based, but water-dispersed polyurethane-based resins are preferred from the standpoint of the working environment at the production site because the degree of crosslinking of the polyurethane-based resin film can be easily adjusted. Examples of water-dispersed polyurethane resins include self-emulsifying polyurethane resins in which hydrophilic groups such as carboxylates (such as —COONa) and sulfonates (such as —SO ₃ Na) are introduced into the main chain or side chain of the polyurethane resin. Resins are preferred. In the case of the solvent type, an isocyanate resin is used as a crosslinking agent to form a polyurethane having a three-dimensional structure, but the water dispersion type is often a linear polyurethane or polyurethane polyurea resin, A crosslinking agent such as a melamine resin, an epoxy resin, or an imine resin may be added in an amount of about 3 to 10% by mass relative to the polyurethane resin, or an acid catalyst may be added in an amount of about 0.5 to 1% by mass to cure. The reaction can be further promoted. Such a cross-linking agent is water resistant of an easily adhesive film,
Not only improves solvent resistance, but also contributes to improved adhesion.

Furthermore, there is no problem in the case of a solvent type, but in the case of a water dispersion type resin, if a surfactant such as an antifoaming agent or an emulsifier is contained in the component, the surface of the biaxially stretched film is whitened and the appearance is poor. In addition, there is a risk that a barrier property defect after vapor deposition may occur. Moreover, you may add inorganic fine particles, organic fine particles, etc. to the polyurethane resin (D) which concerns on this invention as needed, for the purpose of preventing blocking etc., for example.

[Biaxially stretched laminated polypropylene film]
The biaxially stretched laminated polypropylene film of the present invention comprises a propylene polymer (a1) 55 to 90% by mass, calcium carbonate 5 to 5 having an average particle size of 0.5 to 5 μm and a 90% cumulative frequency particle size of 3 μm or less. Biaxially stretched polypropylene film substrate layer obtained from propylene-based polymer composition (A) comprising 25% by mass and alumina-treated rutile type titanium oxide 5 to 20% by mass inorganic compound powder (a2) (B) has a surface layer made of a propylene-based polymer (a1) on one side, and the other side has a surface roughness (three-dimensional center plane average roughness SRa) of 0.3 to 0.7 μm and A back layer composed of a polyolefin polymer composition (C) of a propylene polymer (c1) and an ethylene polymer (c2) having a glossiness of 15% or less is laminated, and the surface roughness of the surface layer Three-dimensional center plane average roughness SRa) is 0.01 to 0.07 .mu.m, and a glossiness of 100% or more, to 0.43 no density of the biaxially oriented laminated polypropylene film 0.85g / cm ^3, L * value Is 95 or more, haze is 91 to 94%, and total light transmittance is 20% or less.

The biaxially stretched laminated polypropylene film of the present invention has a surface layer roughness of less than 0.08, preferably 0.01 to 0.07 μm, a glossiness of 100% or more, preferably 103 to 115%, and total light transmittance. Is 20% or less, preferably 7 to 16% , and the haze is 90% or more, preferably 91 to 94%. The surface roughness of the surface layer is related to the glossiness, and when the biaxially stretched laminated polypropylene film having a surface roughness of 0.08 μm or more is used as a base film for a thermal transfer receiving sheet, surface irregularities occur, When recording an image, there may be a portion where the transfer of the ink transferred along the unevenness of the surface is insufficient, and there is a risk that the density of the image may be dark. If the gloss is less than 100%, There is a risk that the recorded image is dull and dull. When the total light transmittance exceeds 20%, there is a possibility that the color of the core material layer described later appears on the surface.

In general, when an inorganic compound powder is added, the surface layer of the biaxially stretched laminated polypropylene film is visibly sized, for example, a maximum width of 50 to 100 μm due to the inorganic compound powder. There may be some degree of surface protrusions, but if there are many surface protrusions of such a size, the appearance is inferior. The number of convex portions on the surface of the film having a maximum width exceeding 50 μm is most preferably 0 for an A4 size film, preferably about 1 to 10, and practically usable in the range of 11 to 50. However, when 51 or more are present, the appearance as a film is inferior, and when used as an image receptor, the color of the core material or the like may appear on the surface of the recorded image.

The roughness of the surface layer in the biaxially stretched laminated polypropylene film of the present invention was measured with a three-dimensional surface roughness measuring instrument SE-30KS and an analyzer YDA-21 manufactured by Kosaka Laboratory, and the average roughness was obtained ( 3D center plane average roughness SRa).
Biaxially oriented laminated polypropylene film of the present invention, by Rukoto to form a backside layer on the other side of the base layer, Ru can be prevented from falling off the inorganic compound powder contained in the base layer (a2). The resin for forming the back surface layer is not particularly limited, but may be the same as the propylene polymer (a1) constituting the surface layer or the polyolefin polymer composition (C) described later. Good. Further, the surface roughness of the back layer is 0.3 to 0.7 μm .

In the biaxially stretched laminated polypropylene film of the present invention, the other surface of the biaxially stretched laminated polypropylene film base layer has a surface roughness (three-dimensional center plane average roughness SRa) of 0.3 to 0.7 μm, preferably Is 0.4 to 0.6 μm and the glossiness is 15% or less, preferably 7 to 14%, and the total light transmittance comprising a back surface layer made of a polyolefin polymer composition (C) is 20% or less, A biaxially stretched laminated polypropylene film having a range of preferably 7 to 16%, preferably having a haze of 90% or more, more preferably 91 to 94%.

The biaxially stretched laminated polypropylene film of the present invention is a film excellent in blocking resistance, laminate suitability and the like by having the back layer in the above range . Therefore, by constituting the back layer of the biaxially stretched laminated polypropylene film of the present invention with the above polyolefin polymer composition, a biaxially stretched laminated polypropylene film excellent in blocking resistance and laminate suitability can be obtained.

The thickness of the biaxially stretched laminated polypropylene film of the present invention is variously determined depending on the application and is not particularly limited. Usually, the base material layer is 10 to 100 μm, preferably 15 to 50 μm, The surface layer is 0.5 to 15 μm, preferably 1 to 10 μm, the back layer is 0.5 to 15 μm, preferably 1 to 10 μm, and the total thickness is in the range of 20 to 70 μm, preferably 25 to 55 μm. It is in. When the thickness of the surface layer is less than 0.5 μm, the surface roughness (three-dimensional center plane average roughness SRa) of the biaxially stretched laminated polypropylene film may not be kept below 0.08. The biaxially stretched laminated polypropylene film of the present invention has a density of 0.43 to 0.85 g / cm ³ , preferably 0.48 to 0.71 g / cm ³ , a haze of 91 to 94%, and a total light transmittance. it is 20% or less.

The biaxially stretched laminated polypropylene film of the present invention may be subjected to a surface treatment such as corona treatment or flame treatment on one or both sides as necessary. Depending on the application, in order to impart heat sealability, a high pressure process low density polyethylene, linear low density polyethylene, a random copolymer of crystalline or low crystalline ethylene and an α-olefin having 3 to 10 carbon atoms, or Laminate a low-melting point polymer such as a random copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, polybutene, ethylene / vinyl acetate copolymer, or a film made of these compositions on the back layer. May be. Furthermore, in order to improve adhesiveness with other substances, the surface of the stretched film may be anchored with an adhesive such as imine or urethane, or maleic anhydride-modified polyolefin may be laminated.

The biaxially stretched laminated polypropylene film of the present invention includes, for example, a propylene polymer composition (A) as a base layer, a propylene polymer (a1) as a surface layer, and a polyolefin polymer composition as a back layer. A multilayer sheet obtained by coextrusion molding of (C) or the propylene polymer (a1) by a method known per se by a biaxially stretched film molding method such as a simultaneous biaxial stretching method or a sequential biaxial stretching method. Can be molded.

A specific example in the case of producing the biaxially stretched laminated polypropylene film according to the present invention by the sequential biaxial stretching method will be described in the longitudinal direction at 70 to 140 ° C., preferably 90 to 120.
After stretching in the range of 3 to 7.5 times, preferably 4 to 6 times at a temperature of ° C, then in the transverse direction 120 to 190 ° C, preferably in the temperature range of 140 to 180 ° C, 7 to 12
After stretching by a factor of preferably 8 to 11 times, 110 to 180 ° C., preferably 125
It can be obtained by heat setting in a temperature range of 170 ° C.
If the stretching temperature in the machine direction is less than 70 ° C, the multilayer sheet may not be stretched uniformly. On the other hand, if it exceeds 140 ° C, it may be difficult to form voids in the film. Further, when the transverse stretching ratio is less than 3 times, the multilayer sheet may not be uniformly stretched, and when it exceeds 6 times, the film formability may be deteriorated.
If the transverse stretching temperature is less than 120 ° C., the multilayer sheet may not be uniformly stretched.
When it exceeds 90 degreeC, there exists a possibility that it may be difficult to form a space | gap in a film. In addition, if the stretching ratio in the transverse direction is less than 7 times, the multilayer sheet may not be uniformly stretched, and if it exceeds 12 times, the film formability may be deteriorated.
Further, when the heat setting temperature is less than 110 ° C., when the biaxially stretched laminated polypropylene film is used as a support for a photographic paper for a digital photo printer, the film may be curled and the workability may be deteriorated. And there is a possibility that it is difficult to form voids in the film.

A further preferred aspect of the present invention is the constitution defined in claim 6, wherein the polyurethane resin (D) is further formed on the surface layer made of the propylene polymer (a1) of the biaxially stretched laminated polypropylene film described above. A biaxially stretched laminated polypropylene film in which a coating layer made of
The surface roughness (three-dimensional center plane average roughness SRa) of the coating layer surface of the biaxially stretched laminated polypropylene film formed by laminating the coating layer made of such polyurethane resin (D) is 0.08 μm.
Less than, preferably 0.01 to 0.07 μm, glossiness of 100% or more, preferably 10
It is in the range of 3 to 125%. By setting the surface roughness and glossiness of the coating layer made of the polyurethane resin layer within such a range, in the thermal transfer receiving sheet using the biaxially stretched laminated polypropylene film, the gloss after printing is increased, and there is a sense of quality. An image can be formed and dents after printing can be reduced.

The thickness of the biaxially stretched laminated polypropylene film is variously determined depending on the application and is not particularly limited. Usually, the base material layer is 10 to 100 μm, preferably 15 to 50 μm, and the surface layer is 0.5 to 15 μm, preferably 1 to 10 μm
m, the back layer is 0.5 to 15 μm, preferably 1 to 10 μm, the covering layer is 0.1 to 3 μm, preferably 0.3 to 2 μm, and the total thickness is 20 to 70 μm. , Preferably in the range of 25 to 55 μm.

In order to coat (laminate) the polyurethane resin layer on the surface layer of the biaxially stretched laminated polypropylene film, for example, an aqueous solution or dispersion of polyurethane resin is coated with an air knife coater, direct gravure coater, gravure offset, arc gravure coater, Gravure reverse and jet nozzle type gravure coaters, top feed reverse coaters, bottom feed reverse coaters and reverse feed roll coaters such as nozzle feed reverse coaters, 5-roll coaters, lip coaters, bar coaters, bar reverse coaters, die coaters, etc. Using a known coating machine, the amount of the composition contained in the aqueous solution of the polyurethane resin is 0.1 to 20 g / m ² , preferably 0.3 to 2 g.
/ M ² and then dried at a temperature of 50 to 140 ° C. for 10 seconds or more.

Before laminating the polyurethane resin layer on the surface layer of the biaxially stretched laminated polypropylene film, polyisocyanate, polyethylene amine, acrylic polyol or the like may be applied as an anchor agent to the surface layer. In order to laminate the polyurethane resin on the surface layer of the biaxially stretched laminated polypropylene film, once the biaxially stretched laminated polypropylene film is obtained, the polyurethane resin layer is laminated (coated) on the surface layer. Alternatively, the propylene polymer composition (A) serving as the base layer, the propylene polymer (a1) serving as the surface layer, and the polyolefin polymer composition (C) serving as the back layer or the propylene polymer (a1). And a polyurethane-based resin layer may be laminated (coated) on the surface of the multilayer sheet obtained by coextrusion molding. Furthermore, after laminating (coating) a polyurethane-based resin layer on the surface layer of a stretched film obtained by stretching a multilayer sheet obtained by coextrusion molding in the longitudinal direction, it is stretched in the transverse direction to form a biaxially stretched laminated polypropylene film. Also good.

The biaxially stretched laminated polypropylene film of the present invention is a photographic paper for a digital photo printer,
Preferably, it can be suitably used as a support (thermal transfer receptor) for thermal transfer type photographic paper. When the biaxially stretched laminated polypropylene film of the present invention is suitably used as a thermal transfer receptor, the biaxially stretched laminated polypropylene film may be used alone as the thermal transfer receptor, but when the biaxially stretched laminated polypropylene film is used alone, the film In order to avoid this, the biaxially stretched laminated polypropylene film was used as the surface base material layer, because there is a risk that the running performance of the photographic paper may deteriorate when printing with a thermal transfer printer due to the low stiffness (rigidity) of A multilayer structure (support) is preferable.

The thermal transfer receptor preferably has a thickness of usually 100 to 300 μm. When the thickness is less than 100 μm, the mechanical strength becomes insufficient, the rigidity is low, and the texture as a receptor (sheet) may be inferior. If the thickness exceeds 300 μm, the roll length of the roll-shaped receiving sheet in the printer is reduced, or if a predetermined roll length is accommodated, the volume of the printer is increased, making it difficult to make the printer compact. May cause problems.

When the thermal transfer receptor is a multi-layer structure support, the biaxially stretched laminated polypropylene film of the present invention is used as a surface base material from the viewpoint of curling countermeasures, etc., and a three-layer structure of a core material layer and a back surface base material layer is used. Further, a method of laminating (bonding) the back substrate layer and the surface substrate layer by a known technique such as wet lamination, extrusion lamination, dry lamination, wax lamination, etc. can be exemplified. Among these methods, the dry laminating method and the extrusion laminating method are generally preferably used. As an adhesive for dry lamination,
Adhesives such as polyester, polyether, and polyurethane can be used. In the extrusion laminating method, a polyolefin resin such as polyethylene or polypropylene is used as an adhesive. A multilayer structure support according to the present invention includes a first base material layer comprising a biaxially stretched laminated polypropylene film of the present invention on which a receiving layer is formed, an adhesive layer,
A structure in which a release agent layer and a second base material layer are sequentially laminated may be used. Of course, a support having a so-called sticker or seal type structure can also be used. Moreover, you may provide a back surface layer in the back side of a 2nd base material.

<Image receptor>
An example of the layer structure of the image receptor of the present invention is as follows: receiving layer / [biaxially stretched laminated polypropylene film / polyurethane-based resin coating layer / surface layer / biaxially stretched polypropylene film substrate layer / (back layer)] / core material Consists of layers. As another example, receiving layer / [biaxially stretched laminated polypropylene film / polyurethane resin coating layer / surface layer / biaxially stretched polypropylene film substrate layer / (back layer)] / core material layer / biaxially stretched laminated polypropylene A layer structure made of a film can also be exemplified. The image receptor of the present invention is supplied in a sheet form or a roll form, and any one may be selected and used depending on the application. The receptor layer for the image receptor of the present invention is provided on the support via an intermediate layer or directly (multilayer structure). The receiving layer according to the present invention contains a dye dyeable resin as a main component, and if necessary, a crosslinking agent, an anti-fusing agent (lubricant, release agent, etc.),
UV absorbers, colored pigments, colored dyes, fluorescent brighteners, plasticizers, antioxidants, inorganic applications, etc. 1
It is formed by applying a coating appropriately added with seeds or more on the surface of the intermediate layer or a sheet-like support, drying it, and further crosslinking.

As the dye-dyeing resin used in the receiving layer according to the present invention, a resin having good affinity with dyes and high dye-dyeing property is preferably used. Examples of such resins include polyester resins, polycarbonate resins, polyvinyl chloride resins, vinyl chloride-vinyl acetate copolymer resins,
Examples thereof include polyvinyl acetal resins, polyvinyl butyral resins, polystyrene resins, polyacrylate resins, cellulose derivative resins such as cellulose acetate butyrate, thermoplastic resins such as polyamide resins, and active energy ray curable resins. These resins preferably have a functional group (for example, a functional group such as a hydroxyl group, an amino group, a carboxyl group, or an epoxy group) that is reactive with the crosslinking agent to be used.

The receiving layer according to the present invention may be crosslinked by a crosslinking agent. As the cross-linking agent, a chemical reaction type cross-linking agent that is cured or polymerized by a chemical reaction is preferable. Chemical reaction type crosslinking agents include addition reaction types such as epoxy compounds and isocyanate compounds, thermosetting types such as resols, moisture curing types such as 2-cyanoacrylates and alkyl titanates, and condensation reaction types such as urea. Agents and the like. As the addition reaction type crosslinking agent, for example, crosslinking agents such as isocyanate compounds and epoxy compounds are preferably used. The blending amount of the crosslinking agent is preferably 1 to 30% by mass with respect to the total solid content of the receiving layer. In addition, in this receptor layer,
In order to prevent fusion between the receiving sheet and the ink sheet in the printing process, it is preferable that an anti-fusing agent is contained.

As the anti-fusing agent, a release agent and a lubricant are used. For example, modified silicone oil such as amino-modified, hydroxy-modified, carboxy-modified silicone oil, non-modified silicone oil, silicone resin such as silicone acrylic resin, modified silicone One or more of prepolymers of oil and isocyanate compounds, silicone compounds, fluorine compounds, fatty acid ester compounds and phosphate ester compounds are used. As the ultraviolet absorber, benzotriazole-based, benzophenone-based, phenyl salicylate-based, and cyanoacrylate-based ultraviolet absorbing compounds are used.

These various receiving layer-added components may cause a crosslinking reaction via a crosslinking agent. These additives may be mixed with the main component of the receptor layer and applied. Moreover, it may be coated on and / or below the receiving layer as another coating layer. Further, the solid content coating amount of the receptor layer is usually adjusted in the range of 1 to 12 g / m ² , preferably 3 to 10 g / m ² . When the solid coating amount of the receiving layer is less than 1 g / m ² , the receiving layer may not be able to completely cover the surface of the support, resulting in deterioration of the image quality or heating of the thermal head. There is a possibility that a fusing trouble that the ink sheet adheres may occur. On the other hand, the solid content coating amount is 12 g
If it exceeds / m ² , not only is the effect saturated and uneconomical, but also the strength of the receptor layer is insufficient or the thickness of the receptor layer increases, so that the heat insulating effect of the support is not fully exhibited, and the image density May decrease.

The image receptor of the present invention has a sheet-like (multilayer structure) for improving the adhesion between the (multilayer structure) support and the receptor layer, or for improving the antistatic property when a roll-like receptor sheet is used as the image receptor. Structure) An intermediate layer made of resin may be provided between the support and the receiving layer. As the resin used for forming the intermediate layer, various hydrophilic resins and hydrophobic resins can be used. For example, vinyl polymers such as polyvinyl alcohol and polyvinyl chloride and derivatives thereof, polyacrylamide, polydimethyl Polymers containing acrylic groups such as acrylamide, polyacrylic acid or salts thereof, polyacrylic acid esters, polymers containing methacrylic groups such as polymethacrylic acid and polymethacrylic acid esters, polyester resins, polyurethane resins, starches, modified starches, Resins such as cellulose derivatives such as carboxymethylcellulose can be used.

If necessary, the intermediate layer may contain various auxiliary agents such as known antistatic agents, crosslinking agents, thickeners, lubricants, mold release agents, antifoaming agents, wetting agents, leveling agents, and whitening agents. It is also possible to add.
As for the antistatic agent, a conductive agent such as a conductive resin or a conductive inorganic pigment is added. As the conductive resin, there are cationic, anionic and nonionic conductive resins, and among them, cationic conductive resins are preferably used. Examples of the cationic conductive resin include polyethyleneimine, an acrylic polymer containing a cationic monomer, a cation-modified acrylamide polymer, and a cationic starch. About a crosslinking agent, it is preferable to add the above-mentioned isocyanate type crosslinking agent, an epoxy-type crosslinking agent, etc. in order to improve the water resistance of a mid layer, and solvent resistance.

The solid layer coating amount of the intermediate layer is usually in the range of 0.2 to 5 g / m ² , preferably 0.5 to 3 g / m ² . If the solid content coating amount is less than 0.2 g / m ² , the adhesive improvement effect as an intermediate layer may not be sufficiently obtained. On the other hand, if the solid content coating amount exceeds 5 g / m ² , blocking may occur. The effect and operability may be deteriorated.
In the image receptor of the present invention, a back layer may be provided on the back surface (surface opposite to the side on which the receiving layer is provided) of the (multilayer structure) support. Such a back layer is mainly composed of a resin effective as an adhesive, and may contain a crosslinking agent, an antistatic agent, an anti-fusing agent, an inorganic and / or organic pigment, and the like.

For the back layer, a back layer forming resin effective as an adhesive is used. This resin is effective in improving the adhesive strength between the back layer and the (multilayer structure) support, preventing the receiving layer surface from being damaged, and preventing the dye from transferring to the back layer in contact with the receiving layer surface. Such resins include acrylic resins,
Epoxy resins, polyester resins, phenol resins, alkyd resins, urethane resins, melamine resins, polyvinyl acetal resins, and the like, and reaction cured products of these resins can be used. Moreover, in order to improve the adhesiveness of a sheet-like support body and a back surface layer, you may mix | blend crosslinking agents, such as the above-mentioned polyisocyanate compound and an epoxy resin, into a back surface layer coating material suitably.

Further, an antistatic agent such as a conductive resin or a conductive inorganic pigment for preventing static electricity is added to the back layer. Examples of the conductive resin include cationic, anionic, and nonionic conductive resins, and among them, the cationic type is preferably used. Particularly preferred examples of the cationic conductive resin include polyethyleneimine, an acrylic polymer containing a cationic monomer, a cation-modified acrylamide polymer, and a cationic starch. Examples of the conductive inorganic pigment include inorganic pigments coated with compound semiconductor pigments such as oxides and / or sulfides.

In the back layer, if necessary, a friction coefficient modifier such as an organic and / or inorganic filler,
Alternatively, anti-fusing agents such as lubricants and mold release agents can be blended. As an organic filler,
Nylon filler, cellulose filler, urea resin filler, styrene resin filler, polyacrylic acid filler, etc. can be mentioned, and inorganic fillers include silica, barium sulfate, kaolin, clay, talc, heavy calcium carbonate, light calcium carbonate, Examples thereof include titanium oxide and zinc oxide. Examples of the anti-fusing agent include silicone compounds such as non-modified and modified silicone oils, silicone block copolymers, and silicone rubbers, phosphate ester compounds, fatty acid ester compounds, and fluorine compounds. Further, conventionally known antifoaming agents, dispersants, colored pigments, fluorescent dyes, fluorescent pigments, ultraviolet absorbers and the like may be appropriately selected and used.

The back layer has a solid coating amount of usually 0.3 to 10 g / m ² , preferably 1 to 8 g.
/ M ² range. When the coating amount of the solid content of the back layer is less than 0.3 g / m ² , the scratch resistance when the receiving layer is rubbed is not sufficiently exhibited, and a coating defect occurs, resulting in a surface electrical resistance value. May go up. On the other hand, even if the solid content coating amount exceeds 10 g / m ² , no further effect is obtained, and the effect is saturated, which is uneconomical. In the image receptor of the present invention, an image protective layer may be formed after printing on the receiving layer by a thermal transfer method. The image protection layer formation is a so-called transfer method in which a transfer image protection layer is provided on a thermal transfer sheet, and the thermal transfer image protection layer is transferred by heating,
There is a sticking method in which a substantially transparent sheet is adhesively laminated on a thermal transfer image.

Each coating layer in the present invention is coated using a known coater such as a bar coater, gravure coater, comma coater, blade coater, air knife coater, gate roll coater, die coater, curtain coater, lip coater and slide beat coater. Can be formed by drying.

EXAMPLES Next, although an Example is given and this invention is demonstrated further more concretely, this invention is not restrict | limited to these Examples, unless the technical idea is exceeded. In this example, unless otherwise specified, “%” and “parts” mean “% by mass” and “parts by mass”, except for those relating to solvents.
<Evaluation of physical properties>
The physical property values in Examples and Comparative Examples are values obtained by the following evaluation methods.
(1) Surface roughness (μm)
Three-dimensional center surface average roughness SRa was measured using a three-dimensional surface roughness measuring instrument (SE-30KS manufactured by Kosaka Laboratory) and an analyzer (TDA-21 manufactured by Kosaka Laboratory).
(2) Glossiness (%)
Using a Haze Meter (Nippon Denshoku Industries Co., Ltd. VGS-1D-300A), the measurement was performed according to JIS K 7105 at an incident angle of 60 °.
(3) Haze (%)
Using a Haze Meter (NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd.), the light transmittance of one film was measured according to JIS K 7105.
(4) Density (g / cm ³ )
It was calculated by measuring the mass thickness and 1 m ² per film.
(5) Light transmittance (%)
Using a Haze Meter (NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd.), the light transmittance of one film was measured according to JIS K 7105.
(6) Blocking force (N / 20mm)
The film was cut into a strip with a width of 20 mm × 100 mm, the surface layer and the back layer were overlapped, a weight of 250 g / cm ² was applied near the center, and left in an oven at 55 ° C. for 24 hours.
Using a tensile tester (manufactured by Toyo Seiki Co., Ltd.), the test piece was measured for shear peel strength at a tensile rate of 300 mm / min to obtain a blocking force.
(7) Color difference (-)
Overlay 10 sheets of film on white paper, Spectro Eye (Gretag Ma
cbeth).
(8) Number of surface protrusions (film appearance) [piece / A4 (210 mm × 297 mm)]
The surface of the A4 size film was visually observed, and the number of protrusions exceeding 50 μm was counted and evaluated as follows (note that none of the films had surface protrusions with a maximum width exceeding 100 μm). .
A: Zero, has a clean appearance, and has no problem in practical use.
○: 1 to 10 is practically acceptable.
Δ: 11 to 50, but usable.
X: Many 51 or more generate | occur | produce, an external appearance is inferior, and cannot be used as a film for image receptors.

Example 1
<Base material layer: Propylene polymer composition layer>
Propylene homopolymer (PP-1); melting point: 162 ° C., MFR: 2.0 g / 10 min.
As a heat stabilizer, tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′hydroxyphenyl) propionate] methane (product name “Irganox 1010”, manufactured by Ciba Geigy Japan) 1000 ppm and calcium stearate ( 100)
Composition with 0 ppm added;
Calcium carbonate powder [average particle size: 1.1 μm, maximum particle size: 5 μm, 90% cumulative frequency particle size: 2 μm, water content: 400 ppm or less (Karl Fischer method, measured at 200 ° C.)] A rutile type titanium oxide pre-alumina-treated with a composition obtained by kneading and a propylene homopolymer [average particle size: 0.2 μm, water content: 400 pp
m or less (Karl Fischer method, measured at 200 ° C.)] were each dry blended to produce 76.0% propylene homopolymer, 12.0% calcium carbonate, and 12.0% titanium oxide. A propylene polymer composition (A-1) containing was prepared.

<Surface layer: Propylene polymer layer>
Propylene homopolymer (PP-2); melting point: 162 ° C., MFR: 2.4 g / 10 min.
As a heat stabilizer, tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′hydroxyphenyl) propionate] methane (product name “Irganox 1010”, manufactured by Ciba Geigy Japan) 1000 ppm and calcium stearate ( 100)
A propylene-based polymer composition added with 0 ppm was prepared.

<Back layer: Polyolefin polymer composition>
High density polyethylene (MFR: 0.33 g / 10 min, density: 0.964 g / cm ³ , melt
Point: 132 ° C.) 10%, high pressure method low density polyethylene (MFR: 0.35 g / 10 min, density: 0.919 g / cm ³ , melting point: 109 ° C.) 30% and propylene-ethylene block copolymer (MFR: 20 g / 10 min, ethylene content: 12 mol%, melting point: 153 ° C.)
A polyolefin polymer composition containing 0% was prepared. To this resin composition, tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′hydroxyphenyl) propionate] methane (product of Ciba Geigy Japan, product name “Irganox 1” was used as a heat stabilizer.
010 ") 3000 ppm was blended.

<Manufacture of biaxially stretched laminated polypropylene film>
A propylene polymer composition is prepared as a surface layer, a propylene polymer composition as a base material layer, and a polyolefin polymer composition as a back surface layer, and the extrusion ratio of the surface layer / base material layer / back surface layer is (2/17). / 1) Each was melt extruded using a screw extruder and extruded using a multi-manifold type T-die and quenched on a cooling roll to obtain a multilayer sheet having a thickness of about 1.5 mm. This sheet was heated at 120 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times is heated at 160 ° C. and stretched 10 times in the direction (transverse direction) orthogonal to the flow direction. The thickness of the base layer: 25.5 μm and the thickness of the surface layer: 3 μm And the thickness of the back layer: 1.5 micrometer (total thickness: 30 micrometer) The biaxially stretched laminated polypropylene film was obtained. The front layer and the back layer of the biaxially stretched laminated polypropylene film were subjected to corona treatment. The physical properties and the like of the obtained biaxially stretched laminated polypropylene film were measured by the method described above.
The evaluation results are shown in Table 1.

Example 2
In place of the propylene polymer composition (A-1) used as the base material layer in Example 1, calcium carbonate powder [average particle size: 1.3 μm, maximum particle size: 5 μm, 90% cumulative frequency particle size is 2 .3 μm, water content: 400 ppm or less (Karl Fischer method, measured at 200 ° C.)]
A chilled titanium oxide [average particle size: 0.2 μm, water content: 400 ppm or less (Karl Fischer method,
) Measured at 200 ° C.)] was dry blended to produce a propylene polymer composition containing 71.5% of a propylene homopolymer, 19.5% of calcium carbonate, and 9.0% of titanium oxide. A biaxially stretched laminated polypropylene film was obtained in the same manner as in Example 1 except that it was used.
The evaluation results are shown in Table 1.

Example 3
On the surface layer of the biaxially stretched laminated polypropylene film obtained in Example 1, an isocyanate-based anchor agent (manufactured by Mitsui Takeda Chemical Co .; A310: D110N = 3: 2 mixed and diluted with methyl ethyl ketone (MEK)) After coating and drying to coat a 0.15 g / m ² film, waterborne polyurethane (waterborne polyurethane manufactured by Mitsui Takeda Chemical Co., Ltd .; particle size 100
20% aqueous solution) was applied and dried to obtain a film having a 0.15 g / m ² coating laminated thereon.
The evaluation results are shown in Table 1.

Example 4
On the surface layer of the biaxially stretched laminated polypropylene film obtained in Example 2, an isocyanate-based anchor agent (manufactured by Mitsui Takeda Chemical Co .; A310: D110N = 3: 2 mixed and diluted with methyl ethyl ketone (MEK)) After coating and drying to coat a 0.15 g / m ² film, waterborne polyurethane (waterborne polyurethane manufactured by Mitsui Takeda Chemical Co., Ltd .; particle size 100
20% aqueous solution) was applied and dried to obtain a film having a 0.5 g / m ² coating laminated thereon.
The evaluation results are shown in Table 1.

Comparative Example 1
In place of the calcium carbonate used in the base material layer of Example 1, an example except that calcium carbonate having an average particle size of 0.8 μm, a maximum particle size of 6 μm, and a 90% cumulative frequency particle size of 2.6 μm is used. 1 was performed, and a biaxially stretched laminated polypropylene film was obtained.
The evaluation results are shown in Table 1.

Comparative Example 2
In place of the calcium carbonate used in the base material layer of Example 1, an example except that calcium carbonate having an average particle size of 1.2 μm, a maximum particle size of 6 μm, and a 90% cumulative frequency particle size of 2.8 μm is used. 1 was performed, and a biaxially stretched laminated polypropylene film was obtained.
The evaluation results are shown in Table 1.

Comparative Example 3
In place of the calcium carbonate used in the base material layer of Example 1, an example was used except that calcium carbonate having an average particle size of 1.8 μm, a maximum particle size of 10 μm, and a 90% cumulative frequency particle size of 4.2 μm was used. 1 was performed, and a biaxially stretched laminated polypropylene film was obtained.
The evaluation results are shown in Table 1.

Comparative Example 4
The thickness ratio of each layer of the biaxially stretched laminated polypropylene film obtained in Example 1 is the surface layer /
A biaxially stretched laminated polypropylene film was obtained in the same manner as in Example 1 except that melt extrusion was performed using a screw extruder so that the base material layer / back surface layer was 1/18/1.
The evaluation results are shown in Table 1.

Comparative Example 5
A biaxially stretched laminated polypropylene film was prepared in the same manner as in Example 1 except that the multilayer sheet of Example 1 was stretched 4.7 times in the flow direction (longitudinal direction) of the film heated at 120 ° C. Got.
The evaluation results are shown in Table 1.

Example 5
<Manufacture of support>
The biaxially stretched laminated polypropylene film produced in Example 1 was used as a front surface base layer and a back surface base material layer, and art paper (OK Kanto N127.6 g / m ² , manufactured by Oji Paper Co., Ltd.) as a core material layer in between.
Was laminated by a dry laminating method using a urethane-based adhesive to obtain a support having a three-layer structure.

<Formation of back layer>
The back layer coating liquid-1 having the following composition was applied to one side of the support so that the solid coating amount was 3 g / m ² and dried to form a back layer.
Back layer coating solution-1
Polyvinyl acetal resin (trade name: ESREC KX-1, manufactured by Sekisui Chemical Co., Ltd.) 35 parts polyacrylic acid ester resin (trade name: Julimer AT316, manufactured by Nippon Pure Chemical Industries) 25 parts nylon resin particles (trade name: MW330, manufactured by Shinto Fine) ) 10 parts zinc stearate (trade name: Z-7-30, manufactured by Chukyo Yushi) 20 parts cationic conductive resin (trade name: Chemistat 9800, manufactured by Sanyo Kasei) 10 parts water / isopropyl alcohol = 2/3 (mass) Ratio) 400 parts of liquid mixture

<Formation of intermediate layer>
On the surface of the support obtained above, the coating liquid for intermediate layer-1 having the following composition has a solid content coating amount of 1 g.
/ M ² was applied and dried to form an intermediate layer.
Intermediate layer coating solution-1
Acrylic ester resin (trade name: SAR615A, manufactured by Chuo Rika Kogyo Co., Ltd.) 50 parts Cationic conductive resin (trade name: Chemistat 9800, manufactured by Sanyo Chemical Industries) 50 parts Water / isopropyl alcohol = 2/3 (mass ratio) mixed solution 400 Part

<Manufacture of image receptor: formation of receptor layer>
Next, the receiving layer coating liquid-1 having the following composition was coated on the intermediate layer and dried so that the solid content was 5 g / m ² .
Receiving layer coating solution-1
Polyester resin (trade name: Pylon 200, manufactured by Toyobo) 100 parts silicone oil (trade name: KF101, manufactured by Shin-Etsu Chemical Co., Ltd.) 3 parts polyisocyanate (trade name: Takenate D-140N, manufactured by Takeda Pharmaceutical Co., Ltd.) 5 parts Toluene / Methyl ethyl ketone = 1/1 (mass ratio) liquid mixture 300 parts The image receptor is wound in a roll shape around a winding core having an outer diameter of 170 mm so that the receiving layer coating surface is the inner surface of the roll, and immediately moisture-proof packaged at a temperature. The receiving layer was crosslinked by leaving it in a heat treatment chamber controlled at 50 ° C. and a relative humidity of 30% for 5 days to produce a sheet-like thermal transfer image receptor.

Example 6
A sheet-like thermal transfer image receptor was produced in the same manner as in Example 5 except that the formation of the support was changed as follows in the method of Example 5.
<Formation of support>
The biaxially stretched laminated polypropylene film produced in Example 4 is used as the base material surface layer, the biaxially oriented laminated polypropylene film produced in Example 3 is used as the back base material layer, and art paper (trade name: OK Kanto N127.6 g / m ² , made by Oji Paper Co., Ltd.) was bonded by a dry laminating method using a urethane-based adhesive to obtain a support having a three-layer structure.

Comparative Example 7
A sheet-like thermal transfer image receptor was produced in the same manner as in Example 5 except that the formation of the support was changed as follows in the method of Example 5.
<Formation of support>
The biaxially stretched laminated polypropylene film produced in Comparative Example 3 was used as a base material surface layer and a back base material layer, and an art paper (trade name: OK Kanto N127.6 g / m) as a core material layer between them.
² , made by Oji Paper Co., Ltd.) was bonded by a dry laminating method using a urethane adhesive to obtain a support having a three-layer structure.

Comparative Example 8
A sheet-like thermal transfer image receptor was produced in the same manner as in Example 5 except that the formation of the support was changed as follows in the method of Example 5.
<Formation of support>
The biaxially stretched laminated polypropylene film produced in Comparative Example 5 is used as the base material surface layer, the biaxially oriented laminated polypropylene film produced in Comparative Example 3 is used as the back base material layer, and art paper (trade name: OK Kanto N127.6 g / m ² , made by Oji Paper Co., Ltd.) was bonded by a dry laminating method using a urethane-based adhesive to obtain a support having a three-layer structure.

Evaluation Using the thermal transfer image receivers obtained in the above Examples and Comparative Examples, the following items were evaluated by the methods described below. The evaluation results are shown in Table 2.
-Blank paper glossiness: Each thermal transfer image receptor was measured using a photometer based on JIS Z 8741.
A gloss value of 60 degrees was measured.
Next, each thermal transfer image receptor is supplied to a thermal transfer printer (trade name: UP-DR100, manufactured by Sony). On a polyester film having a thickness of 6 μm, yellow, magenta, cyan 3
An ink sheet provided with an ink layer containing a sublimable dye for each color together with an adhesive is sequentially brought into contact with the receiving sheet, and heating is controlled in 16 stages with a thermal head, whereby a predetermined image is applied to the image receptor. Thermal transfer was performed, and a halftone single color image and a color overlay image were printed. The following evaluation was performed on the obtained recorded image.

(1) Print density The reflection density of the recorded image for each applied energy transferred onto the image receptor was measured using a Macbeth reflection densitometer (trade name: RD-914, manufactured by Kollmorgen). The density of the high gradation portion corresponding to the 15th step from the lowest applied energy was displayed as the print density.
(2) Image uniformity The uniformity of the recorded image of the gradation portion corresponding to an optical density (black) of 0.5 was visually evaluated for the presence or absence of shading unevenness and white spots.
There are no shade unevenness and white spots, and there are no practical problems at all. ○, light shade unevenness and white spots are slightly seen, but there are practically no problems. Those markedly marked with problems in practical use were rated as x.
(3) Glossiness of the printed part JIS Z 874 of the high gradation part corresponding to the 15th step from the lowest applied energy
Using a gloss meter based on 1, a glossiness of 60 degrees was measured.
(4) Image unevenness The thickness of the high gradation portion corresponding to the 15th step from the lowest applied energy and the thickness of the unprinted portion were measured using a thickness meter based on JIS P 8118. Print section thickness "-"
The “15-step printed part thickness” was calculated and evaluated based on the following.
“Step” is 0 to 3 μm and there is no practical problem at all. ○, “Step” is larger than 3 μm and 8 μm or less, and irregularities are visible, but there is no practical problem. Δ, “Step” is larger than 8 μm. Those marked with unevenness and very poor in practical use were indicated as x.

The biaxially stretched laminated polypropylene film of the present invention is excellent in surface smoothness, concealability, surface gloss, blocking resistance and laminate suitability, and of course, as a packaging film, this biaxially stretched laminated polypropylene film is used. The resulting image receptor has high image quality,
Since it has high sensitivity, high gloss after printing, and few dents in the printed portion, it becomes a very excellent thermal transfer receptor, and is also useful as an image receptor support.

Claims (6)

Propyl polymer (a1) 55 to 90% by mass, 5 to 25% by mass of calcium carbonate having an average particle size of 0.5 to 5 μm, 90% cumulative frequency particle size of 3 μm or less, and alumina-treated rutile oxidation On one side of the biaxially oriented polypropylene film base layer (B) obtained from the propylene polymer composition (A) obtained by adding an inorganic compound powder (a2) comprising 5 to 20% by mass of titanium, a propylene polymer is provided. a propylene-based polymer comprising a surface layer comprising (a1), having a surface roughness (three-dimensional center plane average roughness SRa) of 0.3 to 0.7 μm and a glossiness of 15% or less on the other surface. A back layer composed of a polyolefin polymer composition (C) of (c1) and an ethylene polymer (c2) is laminated, and the surface roughness (three-dimensional center plane average roughness SRa) of the surface layer is 0. .01 or .07Myuemu, and a glossiness of 100% or more, two to the density of the biaxially stretched laminated polypropylene film is 0.43 no 0.85g / cm ^3, L * to have no 91 95 or more and a haze value of 94%, the total light transmittance A biaxially stretched laminated polypropylene film having a rate of 20% or less. On the surface layer made of propylene-based polymer of the biaxially oriented polypropylene film substrate layer (B) (a1), biaxially oriented laminated according to claim 1, wherein the coating layer comprising a polyurethane resin (D) is formed Polypropylene film. The biaxially stretched laminated polypropylene film according to claim 1 or 2, wherein the biaxially stretched laminated polypropylene film is used as a support for a photographic paper for a digital photo printer. 4. The biaxially stretched laminated polypropylene film according to claim 3 , wherein the photographic paper for a digital photo printer is a thermal transfer type photographic paper. An image receptor comprising an image receiving layer on the polyurethane resin layer (D) of the biaxially stretched laminated polypropylene film according to claim 4 . 6. The image receptor according to claim 5 , wherein the image receiving layer is a thermal transfer image receiving layer.