JPH01241440A - Composite sheet - Google Patents

Abstract

PURPOSE:To obtain a composite sheet excellent in curling-proofness, by maximizing the thickness and filler content of the filler-containing uniaxially stretched resin film layer on the surface side of the multilayer resin sheet laminated to the upper surface of a core material layer and gradually reducing a thickness and filler content toward the lower layer. CONSTITUTION:A composite sheet is a laminate fundamentally constituted by laminating a multilayer resin sheet (a) constituted of at least a double-layer structure of a surface layer A and a base material layer B to a core material layer (b); further, an image receiving layer 11 is provided to the surface of the laminate. The thickness of the surface layer A is made larger than that of the base material layer B to reduce the effect of heat conduction on the base material layer B, and further the core material layer (b) more excellent in heat resistance and rigidity than the multilayer resin sheet is bonded to the multilayer resin sheet to make it possible to prevent curling after thermal transfer printing. Further, the multilayer resin sheet (a) is formed from a triple-layer structure consisting of the surface layer A, the base material layer B and a rear layer C: the filler content of the surface layer A is set to 30-80wt.%, that of the base material layer is set to 10-45wt.% and that of the rear layer is set to 5-30wt.%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a composite sheet with excellent anti-curl properties, and in particular does not curl even when heated during printing, and is suitable for use with playing cards, art paper, etc. The present invention relates to a composite sheet that can be used as information recording paper, such as printing paper such as poster paper, composite paper, electrostatic block paper, thermal paper, and base sheet for image-receiving sheets for thermal transfer recording.

[Prior Art] Conventionally, in an image-receiving sheet for thermal transfer recording, a transfer sheet having a transfer layer containing a sublimable or vaporizable dye and a receiving sheet are overlapped, and this transfer sheet is heated during printing. Thermal transfer is performed by sublimating or vaporizing the dye contained in the transfer layer and dyeing it onto the receiving sheet, thereby forming a dye image on the receiving sheet.

Specifically, in the transfer type thermal recording method using a heat source controlled by an electric signal such as a thermal head, as shown in FIG. 11 and a support 12 is sandwiched between the drum 3 and the heat source 4, and the layer 2 is heated in response to an electrical signal.
A color copy is printed by heating the coloring material No. 2 and transferring it onto the image-receiving layer 11.

The material used for the image-receiving layer 11 differs depending on the content of the coloring material used. In the case of a heat-melting coloring material containing a pigment, the support 12 itself may be used; In the case of a coloring material, an activated clay (activated clay) layer is used, and in the case of a sublimable disperse dye type coloring material, a coating layer of a polymeric material such as polyester is used.

In addition, as the support I2, paper or inorganic fine powder can be used as
Synthetic paper made of stretched film of thermoplastic resin containing 50% by weight M% (Japanese Patent Publication No. 46-40794), or transparent polyethylene terephthalate film or transparent film, coated with an inorganic compound such as silica or calcium carbonate together with a binder. Coated synthetic paper with improved whiteness and dyeability is used.

However, when considering the after-use of the thermally transferred receiving sheet (copying, pencil writing, quality retention, etc.), the image receiving sheet for thermal transfer recording is not suitable in terms of strength, dimensional stability, and adhesion to the print head. It is preferable that the synthetic paper has a large number of microvoids inside obtained by stretching a polyolefin resin film containing inorganic fine powder from
JP-A-60-245593, JP-A No. 61-112693, Japanese Patent Application No. 62-25080).

[Problems to be Solved by the Invention] Such polyolefin resin-based synthetic paper is made of polyolefin as a material in order to provide opacity and a soft feel, as well as to improve adhesion to the print head and paper feeding/ejection properties. The film is stretched at a temperature lower than the melting point of the resin to form microvoids inside.

However, the melting point of the polypropylene resin is lower than that of polyethylene terephthalate or polyamide (240 to 255°C), which is 167°C or less, and the temperature of the surface of the receiving sheet during printing by the print head is low for a very short time. However, since the temperature is 190 to 200°C, which is higher than the above melting point, it has been pointed out that the synthetic paper shrinks due to the heat during printing, causing the heat-sensitive transfer receiving sheet to curl on the printed inner surface. (Unexamined Japanese Patent Publication No. 60-245593)
No. 61-283595).

Furthermore, as a method for preventing the printed receiving sheet from curling, a method has been proposed in which synthetic paper is pasted with another core material (Japanese Patent Application Laid-open No. 198497/1983), but this method is particularly useful for transferring high-density images. The curls had not yet reached a satisfactory level, and problems still remained with the quality of the images obtained.

[Means for Solving the Problems] The present invention has been made in view of the above problems, and includes:
A multilayer resin sheet consisting of at least a two-layer structure in which a filler-containing two-wheel stretched resin film is used as a base layer and a filler-containing uniaxially stretched resin film is attached to one or both sides of the base layer,
In a composite sheet formed by adhering to at least one side of the core material layer, the thickness and filler content of the filler-containing uniaxially stretched resin film layer on the surface side of the multilayer resin sheet adhered to the upper surface of the core material layer are maximized. This is a composite sheet characterized in that the thickness and filler content are gradually decreased toward the lower layer.

[Detailed Description of the Invention] Il+ Composite Sheet The composite sheet of the present invention is basically constructed by laminating a multilayer resin sheet having at least a two-layer structure of a surface layer and a base layer, and a core material layer. The laminate shown in FIG. 2 is provided with an image receiving layer II on the surface thereof, and is put into practical use as a laminate shown in FIG. 5.

In the composite sheet of the present invention, the thickness of the filler-containing uniaxially stretched resin film layer (surface layer) on the surface side of the multilayer resin sheet adhered to the upper surface side of the core material layer is reduced by the heat conducted from the thermal head. By forming the film thicker than the two-wheel stretched resin film layer (base material layer) containing filler, which is easy to absorb, the influence of the heat conduction on the base material layer is reduced (minimizes the shrinkage of the base material layer), and By adhering to such a multilayer resin sheet a core material layer that has better heat resistance and rigidity than the multilayer resin sheet, it is possible to prevent curling after thermally transferred printing.

As a synthetic paper similar to the composite sheet of the present invention, commercially available synthetic paper Yubo FPG (product name: egg oil synthetic paper) is known. Since the thickness is approximately 172 mm thick of the base material layer, it is 1
The thickness of the surface layer is thinner than the thickness of the base material layer, and it is a laminate having a layer structure clearly different from that of the composite sheet of the present invention.

In addition, in order to impart opacity, whiteness, and surface softness to the composite sheet of the present invention, the surface layer of the multilayer resin sheet contains a higher content of inorganic fine powder than the base layer. As a result, the number of microvoids generated is increased, and the adhesion with the thermal head is improved, so that the transferred image is improved.

The surface layer and base material layer of the multilayer resin sheet improved as described above, and a core material having more rigidity and heat resistance than the multilayer resin sheet attached to the side opposite to the surface layer of the base material layer. The thickness of the composite sheet formed in layers is generally 60 to 25
0um, preferably 80 to 210μ, and when the thickness of the multilayer resin sheet is 1, the thickness of the core material layer is generally 0um.
．． 2-3.5. Preferably, the thickness is in the range of 0.5 to 3.0.

In addition, when the multilayer resin sheet is formed with a three-layer structure of a surface layer, a base layer, and a back layer, the composite sheet has a four-layer structure as shown in Figure 1 because a core layer is added in addition to the above three layers. It has become.

The filler-containing uniaxially stretched resin film (back layer) sandwiched between the base layer and the core layer on the back side of the base layer has a lower inorganic fine powder content in the back layer than the base layer. By doing so, the number of microvoids generated by stretching is reduced, and rigidity is imparted to overcome the thermal shrinkage stress of the surface layer generated when the thermal head touches the surface layer.

Furthermore, by forming the back layer to be thinner than the surface layer, the back layer has a tendency to curl slightly in a concave shape.

The back layer imparted with such properties cancels out the heat shrinkage stress generated in the surface layer, thereby making it possible to further reduce curling of the entire multilayer resin sheet when the surface layer is heated.

Furthermore, the multilayer resin sheet is formed of a three-layer structure of a surface layer, a base layer, and a back layer, and the multilayer resin sheet is attached to both the front and back surfaces of the core layer to form a composite sheet as shown in FIG. It is also possible to have a superstructure like this.

Further, other layers may be laminated between or on the composite sheet for other purposes to form a layered structure as shown in FIG. 4.

(2) Multilayer resin sheet Next, each constituent layer of the composite sheet of the present invention, which can be used as a support for an image-receiving sheet, will be explained in more detail.

The multilayer resin sheet is mainly formed from at least a two-layer structure including a surface layer and a base layer shown below, preferably a three-layer structure including a surface layer, a base layer, and a back layer.

fA1 surface layer The surface layer fAl has a specific surface area of 10.000c++”7g
It is a uniaxially stretched polyolefin resin film containing 30 to less than 80% by weight, preferably 40 to 65% by weight, of the above inorganic fine powder and having a thickness of 6 to 90μ, preferably 17 to 80μ.

The uniaxially stretched films of the surface layer and the back layer described below may each be a single layer or a multilayered uniaxially stretched resin film.

In the present invention, for example, when the surface is multilayered.

[The wall thickness and filler content J of the filler-containing uniaxially stretched resin film on the surface side means the total thickness and total filler amount of the multilayer filler-containing uniaxially stretched resin film forming these surface layers.

The sum of the thickness of the surface layer and the back layer is 5 of the total thickness of the composite sheet.
It is 2-80%.

The surface layer fAl has many fine elongated voids with inorganic fine powder as the nucleus.

IB1 base material layer The base material layer fB+ has a specific surface area of 10.000C1
1! A biaxially stretched polyolefin resin film containing 10 to 45% by weight, preferably 15 to 35% by weight of inorganic fine powder of /g or more, and containing many microvoids produced by biaxial stretching, and whose wall thickness is that of a composite sheet. total thickness of 2
It accounts for 0-48%. The wall thickness is generally 5 to 80 μm, preferably 15 to 70 μm, and such a base layer is coated with a polyolefin resin film containing 0 to 25% by weight of inorganic fine powder on both sides. It may have an adhesive layer tE) and a back adhesive layer fFl made of a polyolefin resin film containing 0 to 25% by weight of inorganic fine powder.

The thickness of these adhesive layers fE, F) is 0.2 to 2 μ■
is sufficient.

If the thickness of the base material layer is less than 20% of the total thickness, the stiffness (stiffness) of the laminated resin sheet will decrease, causing problems when adhering to the core material. If it exceeds %, the thickness of the surface layer becomes thinner, so the temperature rise of the base material layer due to heating by a thermal head or the like increases, the amount of shrinkage increases, and the curl prevention effect decreases.

(C) Back layer The back layer fcl contains 5 to less than 30% by weight, preferably 10% by weight of inorganic fine powder having a specific surface area of 10.000c or more.
Uniaxially stretched wall thickness containing ~25% by weight is 4~70μ■,
Preferably! It is a resin film of 3 to 6ouII+.

Examples of polyolefin resins constituting the surface layer, base layer, and back layer include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, poly(4-methylpentene-1) ), among which polypropylene is preferred in terms of heat resistance, solvent resistance, and cost.

To this polyolefin resin, polystyrene, polyamide, polyethylene terephthalate, partial hydrolyzate of ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer and its salt, vinylidene chloride copolymer such as vinyl chloride/vinylidene chloride copolymer, etc. etc. may be blended.

Inorganic fine powders include calcium carbonate, calcined clay,
Examples include diatomaceous earth, talc, titanium oxide, barium sulfate, aluminum sulfate, and silica.

Sheet 1°1 To specifically describe the production of the multilayer resin sheet of the present invention, first, the following compositions fA), fBl and fcl are prepared.

fA1 Composition for forming surface layer fa) Polypropylene 2o-70 Weight 11b
) Resin selected from polystyrene, high density polyethylene, medium density polyethylene, low density polyethylene, ethylene/vinyl acetate copolymer O~2
0 weight 1 fcl inorganic fine powder 30-80% by weight (81 Base layer forming composition fa) Polypropylene 35-955-95 weight Selected from high density polyethylene, medium density polyethylene, low density polyethylene, ethylene/vinyl acetate copolymer Resin 0-20% by weight (cl inorganic fine powder 10-45% by weight Ic
Composition for forming I back layer (a) Polypropylene 70 to 95% by weight (b
) Polystyrene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, ethylene/vinyl acetate copolymer 0 to 20 weight 2 1 cl inorganic fine powder 5 to 30 weight to the base layer forming composition fB) uniaxially stretched film A composition for forming one surface layer (resin sheet of Al) is melt-laminated on one side of the sheet, a resin composition for forming a back layer (resin sheet of C1) is melt-laminated on the other side, and this multilayer sheet is once cooled. This laminate is heated again and stretched in a direction perpendicular to the uniaxial stretching direction of the fBl sheet, and then heat treated.

In order to prevent curling, it is necessary to make a sheet with a low heat shrinkage rate, and it is preferable to set the stretching temperature and annealing treatment temperature high during the production of multilayer resin shinito.

By this stretching, the sheet of composition FB+ is biaxially stretched, and a large number of voids (microvoids) are formed inside the sheet. On the other hand, the surface layer fAl and the back layer tel become films stretched only in the uniaxial direction by the stretching,
There are minute irregularities on the surface.1Surface smoothness (Beck index)
is about 300 to 3000 seconds.

The thickness of each of the surface layer, back layer, and base layer is 1.1 or more, where the thickness of the base layer is 1 and the thickness of one surface layer is 1.1 or more.

Preferably 1.10 to 1.30, the thickness of the back layer is 0.9
Hereinafter, it is preferably 0.70 to 0.85.

If the thickness of the surface layer is smaller than the above range, the curling property will be deteriorated, and if the thickness of the back surface layer is larger than the above range, the curling property will be deteriorated.

Specifically, the thickness of each layer of the surface layer, base material layer, and back layer is such that the total thickness of the surface layer and back layer is within the range of 52 to 80% of the total thickness of the multilayer resin sheet, and The thickness of the base material layer is 2
It is preferably 0 to 40%.

If the thickness of the base layer exceeds 40% of the total thickness, the heat shrinkage of the base layer will increase due to heating from one surface layer, and the curl improvement effect will decrease. Conversely, if the thickness of the base material layer is 20% of the total thickness
% or less, the stiffness of the multilayer resin sheet decreases, making it unsuitable for use as a base material for thermal transfer receiving paper or various printing papers.

In the case of a multilayer composite sheet as shown in FIG. 4, the outermost layers iD and Gl are preferably 50% or less of the thickness of the surface layer IAI; For example, it is important to arbitrarily control surface smoothness, gloss, pencil writing properties, adhesion to core materials, and slip properties), and the optimal formulation and
For example, there is the following composition.

a) Polypropylene 20-70% by weight b)
0 to 20% by weight of a resin selected from polystyrene, high density polyethylene, medium density polyethylene, low density polyethylene, and ethylene/vinyl acetate copolymer C) Inorganic fine powder 30 to 80% by weight 2 In the multilayer resin sheet of the present invention, the base material The layer fBl is stronger against tensile force than a uniaxially stretched film layer or a non-axially stretched film layer, but it is easily heat-shrinkable and has poor curl prevention properties.Therefore, the thickness of the surface layer fAl is increased, and the filler content is increased. By increasing the number of voids in the surface layer tAl by stretching with a high tAl, the transfer of heat to the base layer is reduced, and the opacity of the sheet is also improved.

Furthermore, in order to impart rigidity to the back layer fcl, the amount of filler is reduced and the amount of voids due to stretching is reduced.

Therefore, it is important that the surface layer contains a large amount of inorganic fine powder, and the content and thickness of the inorganic fine powder are gradually decreased from the base layer to the back layer.

The content of inorganic fine powder in the surface layer is determined according to JIS P-8120.
The surface smoothness (Beck finger pi) measured at 300-3.
It is preferable to select the time to be about 000 seconds.

The inorganic fine powder to be mixed into the surface layer is selected so as not to form large protrusions on the surface layer as much as possible, and preferably has a 325 mesh residue of 1 opp or less.

The particle size is preferably 3 μm or less.

The back layer (C1) of the multilayer resin sheet attached to the opposite side of the front-transferred image-receiving layer contains fine inorganic powder in order to provide slipperiness with the roll during transfer and writability to the back layer after transfer. The content is preferably 5 to 30% by weight, preferably 8 to 20% by weight, and it is preferably selected so that the surface smoothness (Beck index) measured according to JIS P-8120 is 50 to 2.000 seconds.

The multilayer resin sheet of the P' sheet has a surface layer (the thickness of Al) as the base layer (B).
By making it thicker and containing a large amount of inorganic fine powder, it has a moderate amount of microvoid inside even under stretching and annealing temperature conditions in the softening temperature range near the melting point, making it a thermal transfer receiving paper. Since the adhesion with the thermal head when used as a substrate for printing is improved, the resulting transferred image can be made clearer.

When the surface layer (^) which is a uniaxially stretched film layer is stretched under the same stretching conditions as the base layer which is a biaxially stretched film layer,
Thermal shrinkage rate becomes smaller in both the vertical and horizontal directions. Therefore, in order to prevent curling caused by unilateral heating from the surface layer (Al), by making the surface layer fAl, which has a small heat shrinkage ratio, as thick as possible, the base material layer (Bl
Curling is prevented by lowering the heat transfer (temperature) to reduce shrinkage.

Since the back layer fcl is less exposed to high heat like the front layer fAl, by reducing the content of inorganic fine powder as much as possible than the base layer (Bl), it is possible to reduce the generation of microvoids and improve the rigidity. It is applied to the back side to prevent curling.

Furthermore, by making the thickness of the back layer fcl thinner than the surface layer fAl, it is possible to create a slight tendency to curl toward the back surface (to the extent that there is no problem in practice).

Furthermore, as shown in Fig. 3, by attaching the surface layer of the multilayer resin sheet to the back side of the core material layer, it is possible to give the negative layer a tendency to curl, so that the effect of preventing curling toward the surface is improved. 6 In addition, if it is necessary to give the back surface writing properties with a pencil or the like or slipperiness with a roll during thermal transfer, the surface layer composition fGl may be added to the back surface layer (the outermost layer of C1). The back layer fc)
A layer having a thickness not exceeding 20% of the thickness of the back layer (C) may be provided.However, if the thickness exceeds 20% of the thickness of the back layer (C), the improvement in rigidity and the back surface curl effect by the back layer (C) will decrease. .

In the pasting of the multilayer resin sheet and the core material, the thickness of the pasted laminated sheet after being pasted is at least 60 to 250 mm.
The layer thickness is preferably 80 to 210 .mu.m. If the thickness is less than 60 .mu.m, the adhesive sheet itself lacks rigidity and is not suitable as a support for printing paper or image-receiving sheets for thermal transfer. Thickness is 2
If it exceeds 50 μI, it is effective in preventing curling, but it is not preferable in terms of suitability for machines such as printers (for example, transportability).

(Other layers) The multilayer resin sheet may contain the surface layer,
In addition to the base layer and the back layer, other layers may be laminated.6 For example, an inorganic fine powder having a specific surface area of IO,000c++" or more of 7 g is added to the outside of the surface layer and/or the back layer. A uniaxially stretched polyolefin resin film containing 60 weight 2, preferably 40 to 55 weight 1 is laminated (
D, GI L, writability and adhesion during pasting can be imparted.

(3) Core layer layer In the composite sheet of the present invention, materials that can be used as the core layer laminated on the multilayer resin sheet include:
Pulp paper, plastic film, etc., preferably those having higher heat resistance and rigidity than the multilayer resin film to be laminated, are also usable. Pulp paper laminated with blast film can also be used.

The pulp paper includes high quality paper and art paper.

Examples include coated paper, wallpaper, paper impregnated with synthetic resin or emulsion, paper with internal addition of synthetic resin, and paperboard.

The above plastic films include polyolefin polyvinyl chloride, polyethylene terephthalate, polystyrene, polymethacrylate, polyamide (nylon 6,
Nylon 66 Nylon 6, IO, Nylon 6.12
etc.). These films may be stretched.

Additionally, metal foils such as aluminum foils can also be used.

The thickness of the film or pulp paper used for these core materials is 0.2 to 1 when the thickness of the multilayer resin sheet to which it is attached is 1.
3.5, preferably in the range of 0.5 to 3.0.

If the thickness of the core material is 0.2 or less, the image quality obtained by thermal transfer will be good (although the curl prevention effect will decrease when three colors are printed solidly with high density gradation. If it is more than twice as large, the resulting image will deteriorate due to the influence of the surface properties of the core material.

Methods for attaching the core material and the multilayer resin sheet include, for example, a method of attaching using a solvent-based or water-based adhesive, and a method of attaching by heat using a hot-melt adhesive. The adhering means is appropriately selected depending on the type of core material.

Next, Figure 3 shows the structure of a composite sheet in which multilayer resin sheets are pasted on the front and back sides of a core material.Such a composite sheet has been designed to prevent curling after thermal transfer, and it is also important to select the core material. When an image is formed by thermal transfer using the adhesive structure, the image density is high and there is no variation in the image.
Furthermore, there is almost no curling even after the three colors of red, blue, and yellow (Y, M, (:,) are transferred at maximum density (so-called solid black printing).

(4) Thermal transfer image-receiving sheet A coating liquid for forming an image-receiving layer is applied to the surface of the composite sheet of the present invention.7. A thermal transfer image-receiving sheet is obtained by drying and scattering the solvent.

The thickness of this image-receiving sheet is generally 60 to 250μ,
Preferably 80 to 210μ■, JIS P-8125
A material having a taper stiffness of 3 to 20 g/C11 is preferable in terms of curl prevention and sheet feeding/discharging properties.

91111 As the resin forming the image receiving layer, oligoester acrylate resin, saturated polyester resin, vinyl chloride/vinyl acetate copolymer, acrylic ester/styrene copolymer, epoxy acrylate resin, etc. are used,
These are dissolved in toluene, xylene, methyl ethyl ketone, cyclohexanone, etc. and used as a coating liquid.

This coating liquid can contain an ultraviolet absorber and/or a light stabilizer to improve light resistance.

Examples of the ultraviolet absorber include 2-(2'-hydroxy-3,3-di-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-t-
amyl phenyl)-2H-benzotriazole, 2-(
2-Hydroxy-3-t-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2-+2'-hydroxy-3'.

5'-t-butylphenyl)-benzotriazole, 2
-(2'-hydroxy-3',5-di-t-amylphenyl)benzotriazole and the like.

Examples of light stabilizers include distearylpentaerythritol rebiphosphite, bis12.4-di-butylphenyl)pentaerythritol diphosphite, dinonylphenylbentaerythritol diphosphite, and cyclic neoventante dry rebisphosphite. octadeciferophosphite), tris(nonylphenyl, 1- +2- [3- +3.5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl)-4-[3-(3.5 -di-butyl-4-hydroxyphenyl)propionyloxyl-2.2.6
．． Examples include 6-titramethylbiveridine.

Addition 1 of these ultraviolet absorbers and light stabilizers is:

For 100 parts by weight of the resin constituting the image-receiving layer 3, the amount of the ultraviolet absorber is 0.05 to 10 parts by weight, preferably 0.1 to 2 parts by weight, and the light stabilizer is 0.5 to 3 parts by weight, preferably 0, 1
~1 part by weight.

Furthermore, a release agent can be included in the image-receiving layer to improve the bondability with the thermal transfer sheet. Examples of the mold release agent include solid waxes such as polyethylene wax, amide wax, and Teflon powder; fluorine-based and phosphoric acid ester-based surfactants; and silicone oil, with silicone oil being preferred.

Although oily silicone oils can be used, hardened silicone oils are preferred.

Furthermore, in order to improve the whiteness of the image-receiving layer to further enhance the clarity of the transferred image, and to impart writability to the surface of the heat-transfer sheet, and to prevent the transferred image from being re-transferred, the image-receiving layer is A white pigment can be added to.

As the white pigment, titanium oxide, zinc oxide, zinc olin clay, etc. are used, and two or more of these can be used as a mixture. As the titanium oxide, anatase type titanium oxide and rutile type titanium oxide can be used. Examples of the anatase type titanium oxide include KA-to, A-20. KA-15, A-30.

ni A-: J5, KA-60, ni A-80, ni A
-90 (all manufactured by Titanium Kogyo ■), etc.
As rutile type titanium oxide, KR-310, KR-38
0, KR-460, KR-480 (all manufactured by Titan Kogyo ■), and the like. The amount of the white pigment added is preferably 5 to 50 parts by weight based on 100 parts by weight of the resin constituting the image-receiving layer.

The thickness of the image-receiving layer 11 is generally 0.2 to 20 μm.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, the curl height, heat shrinkage rate, image evaluation, and quality evaluation of opacity in the examples are based on the measurement methods shown below.

L2 soil 11 The laminated resin sheet and image receiving sheet to be measured are printed on a Hitachi color video printer VD-50 (product name).
, M, and C colors are transferred in solid print with a width of 120 mta in the MO (machine direction) direction and a TD (
)Rubber direction) cut into a rectangle with a width of 100 mm, and when it was placed on a flat surface for 24 hours at a temperature of 23°C and a humidity of 50%, the height of lift (m + s
Measure l.

The dimension (I2) was measured when the multilayer resin sheet was placed on a flat surface without being fixed and left at a temperature of 120°C for 30 minutes.
The original length (β.) and this! The heat shrinkage rate was determined using the following formula.

55 dishes Determined according to JIS P-8138.

Mitsubishi paper coated with L-valued image-receiving sheet and sublimable dye and dried.■
Thermal gradient test i (Toyo Seiki Type-HG-100
), the hot plate was heated at 5 points at 10°C intervals from 120°C, and heated for 2 seconds at a pressure of 0.5kg/c+m''.
A transferred image was obtained.

The density of the resulting transferred image was measured using a Macbeth densitometer and evaluated on the following five scales.

5: Very good.

4: Good.

3: No practical problem.

2: There are some practical problems.

l: Not practical.

1°1 of the sheet Example 1 (Multilayer resin sheet for Example 1) ill melt index (MIlO, 75 weight i of polypropylene with an average particle size of 1.5 μI mixed with 25 weight % of calcium carbonate (B) C, 270 After heating at 118°C in an extruder, it was extruded into a sheet and cooled in a cooling device to obtain an unstretched sheet.This sheet was heated at 150°C.
After heating, the film was stretched 5 times in the longitudinal direction.

(Surface layer composition IA, which is a mixture of 55% by weight of calcium carbonate with an average particle size of 1.5 μm in 45 weight It of polypropylene having a MI of 4.0 MI) was melt-kneaded using an extruder.

The extruded sheet was laminated on one side of an f1+ 5 times stretched sheet. In addition, on the opposite side of the 5 times stretched sheet of fl), a composition for the back layer (C ) in another extruder,
A laminate with a three-layer structure was obtained by extrusion lamination.

Then, after cooling this laminate to 60°C.

It was heated to 165°C, stretched 7.5 times in the transverse direction with a tenotar, annealed at 167°C, cooled to 60°C, and the edges were slit to form a three-layer fA/B/C: wall thickness. A multilayer resin sheet with a 25/20/15 μml structure was obtained.

The opacity of this multilayer resin sheet is 90%, and the heat shrinkage rate of this sheet is 1.0% in the MD force direction and 0 in the TI direction.
．． It was 2z.

Example 2 (Multilayer resin sheet for Comparative Example 1) +11 75 weight percent of polypropylene with a melt index (Ml) of 0.8 is mixed with 25 weight percent of calcium carbonate with an average particle size of 1.5 μm (B) at 270°C. The mixture was kneaded using an extruder set to , extruded into a sheet, and cooled using a cooling device to obtain a non-stretched sheet.

Next, this sheet was heated to 150°C and then stretched 5 times in the machine direction.

(2) The surface layer composition fA), which is a mixture of 45% by weight of polypropylene of old 4.0 and 55% by weight of calcium carbonate with an average particle size of 1.5 μm, is melt-kneaded in an extruder, and the extruded sheet is , ill was laminated on one side of a 5 times stretched sheet. In addition, on the opposite side of the fl) 5 times stretched sheet, 85% by weight of polypropylene with an MI of 4.0 and an average particle size of 1
．． A composition fc) for the back layer containing 5 µm of calcium carbonate (15% by weight) was melt mixed in another extruder and extruded and laminated to obtain a three-layered laminate.

Next, after cooling this laminate to 60°C,
℃, stretched 7.5 times in the transverse direction using a Tenku, annealed at 163℃, cooled to 60℃, and slit the edges to form a three-layer IA/B/C: wall thickness 25 /
A multilayer resin sheet having a structure of 20/15μI) was obtained.

The opacity of this multilayer resin sheet is 91%, and the heat shrinkage rate is M
It was 2.5% in the D direction and 1.6% in the TD force direction.

Example 3 (Multilayer resin sheet for Comparative Example 2) Stretched laminated three-layer structure with wall thicknesses A/B/C: 15/30/15μ in the same manner as Example 1 except for changing the width of the die slit. A resin sheet was manufactured.

Example 4 (Multilayer resin sheet for Comparative Example 3) 85% by weight of polypropylene with a melt index (fMI) of 0.8 is mixed with 15% by weight of calcium carbonate with an average particle size of 1.5 μm (B), set at 270°C The mixture was kneaded using an extruder, extruded into a sheet, and cooled using a cooling device to obtain a non-stretched sheet. 15 sheets of this
After heating to 0° C., it was stretched for 5 times in the longitudinal direction.

(2) Composition IA) for the surface layer, which is a mixture of 55% by weight of old 4.0 polypropylene and 45% by weight of calcium carbonate with an average particle size of 1.5μ layer, is melted and mixed in an extruder, and the extruded sheet is fl) was laminated on one side of a 5 times stretched sheet. Also, on the opposite side of the 5 times stretched sheet of (1), Ml
4.0 polypropylene 85 weight 1 to average particle size 1.5μ
The back layer composition (fc) mixed with 15% by weight of calcium carbonate was melt-kneaded in another extruder and extruded and laminated to obtain a three-layered laminate.

Next, after cooling to 60°C, heating to 165°C and stretching 7.5 times in the transverse direction with a tenter, annealing at 167°C, cooling to 60°C, slitting the edges and forming three Layer (A/B/C: wall thickness 40/80/40μm
A multilayer resin sheet having an L structure was obtained.

Example 5 (Multilayer resin sheet for Comparative Example 4) fil 25% by weight of calcium carbonate with an average particle size of 1.5 μm was blended into 75% by weight of polypropylene with a melt index (MIIo, 8) (B) Extrusion set at 270°C After mixing in a machine, it was extruded into a sheet and cooled in a cooling device to obtain an unstretched sheet.This sheet was heated at 150°C.
After heating, the film was stretched 5 times in the longitudinal direction.

(2) The surface layer composition fA), which is a mixture of 85 parts by weight of old 4.0 polypropylene and 15% by weight of calcium carbonate with an average particle size of 1.5 microns, is melt-kneaded in an extruder, and the extruded sheet is It was laminated on one side of a 5 times stretched sheet of fil.

In addition, on the opposite side of the 5 times stretched sheet of (1),
．． 45% by weight of polypropylene with an average particle size of 1.5 μ-
A composition (C) for the back layer containing 55 parts by weight of calcium carbonate was mixed in a separate extruder and then extruded and laminated to obtain a three-layered laminate.

Next, after cooling to 60°C, heating to 165°C, stretching 7.5 times in the transverse direction with a tenter, annealing at 167°C, cooling to 50°C, slitting the edges and forming three Layer I A/B/C: Wall thickness 25/20/15u
A multilayer resin sheet with +S) structure was obtained.

Example 6 (Multilayer resin sheet for Example 2) fil 75% by weight of polypropylene with a melt index + MI of 10.8 is blended with 25% by weight of calcium carbonate with an average particle size of 1.5μI fB) L, in an extruder set at 270°C After mixing, the mixture was extruded into a sheet and cooled using a cooling device to obtain a non-stretched sheet. This sheet 1
After heating to 50°C, it was stretched 5 times in the machine direction.

(21Blend (0) in which 55% by weight of polypropylene with MI 4.0 is blended with 45% by weight of calcium carbonate with an average particle size of 1.5 μm) and 45% by weight of polypropylene with Ml 4.0 with an average particle size of 1.5 μm Calcium carbonate is 55%
The mixture +A) is melt-kneaded in a separate extruder,
They were laminated in a gooey, coextruded into sheets, and laminated so that the surface +01 of the 5 times stretched sheet of (1) was on the outside. 85% by weight of old 4.0 polypropylene on the other side
A composition tc) in which 15% by weight of calcium carbonate having an average particle size of 1.5 μm was mixed with the above mixture was melt-kneaded in another extruder and extruded and laminated to obtain a four-layered laminate.

Then, after cooling to 60°C, heating to 165°C,
Stretched at 7.5 times in the transverse direction using a tenter, annealed at 157°C, cooled to 60°C, and slit the edges to form four layers (opening/A/B/C: wall thickness 3/22/20 /15u
+*1 Yokoen's multilayer resin sheet (1).

Example 7 (Multilayer resin sheet for Example 3) (II Melt index (MIO, 8, melting point 1 [
High-density polyethylene 311 and 25% by weight of calcium carbonate with an average particle size of 1.5 μm were blended with 72% by weight of polypropylene having a temperature of >5 to 167°C (kneaded in an extruder set at 270°C).

On the other hand, polypropylene 99 with a melt index of 1.0
．． Compositions fE and Fl containing 7% by weight and 03% by weight of calcium carbonate were kneaded at 270°C using another extruder.

Then, each of these was supplied to two coextrusion dies, extruded into a sheet, and cooled by a cooling device to obtain an unstretched sheet with a three-layer structure. This sheet was heated to 100°C and then stretched 5 times in the machine direction.

A composition fA) for the surface layer, which is a mixture of 45% by weight of polypropylene with a +21 Ml of 4.0 and 55% by weight of calcium carbonate with an average particle size of 1.5 μm, was melt mixed in an extruder, and the extruded sheet was mixed with 5% of the fil. It was laminated on one side of a double-stretched sheet. Further, on the opposite side of the 5 times stretched sheet of (1), a composition for the back layer was prepared by mixing 85 parts by weight of polypropylene with an Ml of 4.0 and 15 parts by weight and ffi% of calcium carbonate having an average particle size of 1.5 μ. +C) was melt-kneaded in another extruder and extruded and laminated to obtain a laminate having a five-layer structure.

Then, after cooling to 60°C, heating to 165°C,
It was stretched 7.5 times in the transverse direction with a tenter, annealed at 165°C, cooled to 60°C, and the edges were slit to form five layers (A/E/B/F/C: wall thickness 25/1 /+8/I
A multilayer resin sheet having a structure of /15 μml was obtained.

Example 8 (Multilayer resin sheet for Example 4) During lamination in (2) of Example 7, calcium carbonate 45 @ 11% with an average particle size of 1.5 μI was mixed with polypropylene 5511 of [4] on one surface layer fAlO. Composition FD+ for the outermost surface layer was melt mixed and laminated using another extruder. Also,
At the same time, a composition fGl for the outermost back layer (C1'FI!lII, 58% by weight of polypropylene of Ml 4, and 42ilF if% of calcium carbonate having an average particle size of 1.5 μl) was mixed in another extruder. Laminated by melting and mixing.

The stretching conditions were the same as in Example 7, and 7 layers (D/A/E
/B/F/(:/G: Thickness: l/22/l/18/l
A multilayer resin sheet having a /+2/311 ml structure was obtained.

Example 9 (Multilayer resin sheet for Example 5) fil 75% by weight of polypropylene with a melt index of 1Ml1O,8 is blended with 25% by weight of calcium carbonate having an average particle size of 1.5 μm (B) Extrusion set at 270°C After kneading in a machine, the mixture was extruded into a sheet and cooled in a cooling device to obtain a non-stretched sheet. 15 sheets of this
After heating to 0°C, it was stretched 5 times in the machine direction.

(2) The surface layer composition fA), which is a mixture of 45% by weight of old 4.0 polypropylene and 55% by weight of calcium carbonate with an average particle size of 1.5μ, is melt-kneaded in an extruder, and the extruded sheet is processed into a filtrate. was laminated on one side (front surface) of a 5-fold stretched sheet, then cooled to 60°C, heated to 165°C, stretched in the transverse direction with a tenter at a 7.5 (Q), and 16
After annealing at 7°C, cool to 60°C and slit the edges to form a two-layer FA/B: wall thickness 30,725 μml.
A structured multilayer resin sheet was obtained.

Multilayer resin sheet (shown in Table 1) manufactured with the above convex side
Toyo Morton's solvent-type urethane blue tint S-208OA (resin) and BLS were used as adhesives on the back layer side of the Al.
-2080 (curing agent) mixture was spread on a φ cloth to give 3 g/+2, the core material shown in Table 7p1 was attached, the adhesive was applied to the back side of this core material, and the adhesive shown in Table 1 was applied. The surface layer side of the multilayer resin sheet shown in Table 1 was pasted with the adhesive to obtain a composite sheet shown in Table 1.

Examples 1-9. Comparative Examples 1 to 4 The image receiving and forming composition shown below was coated on the surface layer of the composite sheet shown in Table 1 by wire bar coating so that the dry thickness was 4 μm, and it was dried and used for thermal transfer. An image receiving sheet was obtained.

1 image Composition: Saturated polyester (Vylon 200 manufactured by Toyobo ■, Tg 67°C) 5.31 parts by weight (Vylon 290.7g 77°C) 5.3 parts by weight Vinyrite V Y II H (Union carbide split vinyl chloride/vinyl acetate) Copolymer) 4.5 parts by weight Titanium oxide (Titan Kogyo A-1o) 1.5 parts by weight Amino-modified silicone oil (Shin-Etsu Silicon KF-393+) 1.1 parts by weight Epoxy-modified silicone oil (Id) Koshi'J:+ntllJ X-22-34311
, 1ffffl part toluene
30 parts by weight methyl ethyl ketone 30
Part by weight cyclohexane 22 @
Measurement of heat shrinkage rate and transparency of one weight layer resin sheet, and
The curl height and image quality of the image-receiving sheet for thermal transfer recording after thermal transfer were measured, and the results are shown in Table 1.

[Effect of the invention 1 The composite sheet of the present invention has a surface layer fAl of a multilayer resin sheet.
By making the thickness of the layer thicker than the base material layer +81 and containing a large amount of inorganic fine powder, even under stretching and annealing temperature conditions in the softening temperature range near the melting point,
It has a moderate amount of microvoids inside, and when used as a base material for thermal transfer receiving paper, the adhesion with the thermal head is improved, so the resulting transferred image is clear. In addition, when the surface layer [Al, which is a uniaxially stretched film layer] is stretched under the same stretching conditions as the base material layer, which is a biaxially stretched film layer, the heat shrinkage rate is small in both the N and lateral directions, and it may be formed thicker. Therefore, curling is prevented by lowering the heat transfer (temperature) to the base material layer (8), which has a large thermal shrinkage rate, and reducing shrinkage.

Furthermore, since the back layer (C1 is the surface layer tA) is not exposed to high heat, the content of inorganic fine powder can be kept as low as possible (by doing so, the generation of microvoids can be reduced) compared to the base layer fB+. , it is possible to prevent curling by adding rigidity to the back surface.Also, by making the thickness of the back layer fcl thinner than the surface layer fAl, it is possible to prevent a slight curling tendency toward the back surface (to the extent that there is no difference in practical terms). can have.

Furthermore, as shown in Figure 3, by attaching the surface layer of the multilayer resin sheet to the back layer of the core material, it is possible to give it even more curling, so the curl prevention effect in the surface direction is even more effective. can be improved.

Such a composite sheet of the present invention can be used as a support for an image-receiving sheet for thermal transfer recording, which is prevented from curling after thermal transfer, and especially for video printers that use a thermal head to form electrical signals on a receptor. It is useful as a support for image-receiving sheets for color copying.

[Brief explanation of the drawing]

1 to 4 show cross-sectional views of a composite sheet according to an embodiment of the present invention, and FIG. 5 shows a cross-sectional view of an image-receiving sheet for thermal transfer recording in which an image-receiving layer is provided on the surface of the composite sheet of the present invention, FIG. 6 shows a sectional view of the main parts of the transfer thermosensitive recording apparatus. 1: Image receiving sheet for thermal transfer recording, 2: Transfer body 3 Nibraten roll 4: Thermal head 11: Image receiving layer ■2・Support (composite sheet) 21: Substrate 22: Coloring material layer A: Surface layer B: Base Material layer C/back layer D, G: Outermost layer E: Surface adhesive layer F: Back adhesive layer, a: Multilayer resin sheet b:
Core material. Figure 1 Figure 2 Figure 5 Figure 3 Figure 4 Figure 6

Claims (3)

[Claims] (1) A multilayer resin sheet consisting of at least two layers, in which a filler-containing biaxially stretched resin film is used as the base layer and a filler-containing uniaxially stretched resin film is attached to one or both sides of the base layer, is attached to at least one side of the core material layer. In the composite sheet formed by the above-mentioned composite sheet, the thickness and filler content of the filler-containing uniaxially stretched resin film layer on the surface side of the multilayer resin sheet attached to the upper surface side of the core material layer are maximized, and the filler content is sequentially increased toward the lower layer. A composite sheet characterized by being formed with a reduced wall thickness and filler content. (2) The composite sheet according to claim 1, wherein the multilayer resin sheet is formed by adhering a surface layer to the surface of the base material layer and a back layer to the back surface of the base material layer. (3) The filler content of the surface layer is within the range of 30 to 80% by weight, the filler content of the base layer is within the range of 10 to 45% by weight, and the filler content of the back layer is within the range of 5 to 30% by weight. composite sheet.