JPS631184B2 - - Google Patents

Description

[Detailed description of the invention]

[1] BACKGROUND TECHNICAL FIELD OF THE INVENTION The present invention relates to a thermoplastic resin film with excellent printability suitable for use as synthetic paper. More specifically, the present invention provides printing, folding,
Trouble caused by falling of compounded filler during secondary processing such as lamination, that is, so-called paper powder trouble.
This invention relates to a filler-containing thermoplastic resin film. By uniaxially or biaxially stretching a thermoplastic resin film containing a fine filler at an appropriate temperature, an opaque thermoplastic resin film can be obtained. This film is similar to pulp paper in terms of its opacity, whiteness, texture and feel, and can be used as a single-layer structure consisting only of this film or as a multi-layer structure with this film as a surface layer. It is known that it can be used for various paper purposes. Stretched films made of filler-containing thermoplastic resins are opaque and white because peeling occurs at the interface between the resin and filler during film stretching, and as stretching progresses, fine gaps are created between the resin and filler. Therefore, at the end of stretching, fine voids containing filler particles are formed inside the film, and the closed shape of the voids is not maintained near the film surface, resulting in the formation of fine cracks on the surface. This is because light is scattered on the film surface and inside. These surface cracks and internal voids give the film properties similar to pulp paper. However, when performing secondary processing such as printing, folding, bookbinding, and bag making on such opaque film,
As voids near the surface have their closed structure destroyed and become surface cracks, filler particles that have come to exist in a free or semi-free state on the surface adhere to the rolls and blankets of secondary processing machines and cause problems during processing. Failures often occur and the efficiency of secondary processing is significantly reduced. Prior Art Regarding the prevention of such paper dust problems, there are methods of applying a pigment coat on the surface similar to pulp paper to prevent filler particles from falling off, methods of coating the surface with a paste-like substance, and methods of combining filler and resin. A method of blending additives to improve interfacial adhesion,
and so on. However, these methods are not satisfactory. In other words, in the pigment coating method, the film and the coating layer tend to separate easily and the generation of paper dust from the edges of the film is unavoidable, whereas in the method of coating with a paste-like substance, the paste-like substance impairs printability. This is because there are problems in terms of lowering the temperature and the complexity of the process. On the other hand, the method of improving resin/filler particle interfacial adhesion is simple in terms of process, but has the disadvantage that the additives used to improve adhesion are expensive and cannot be used in large quantities. Significant problems arise during stretching in this case. In other words, since the resin/filler particle interfacial adhesion becomes strong, a large stretching force is required during film stretching, which may make it impossible to produce thick films depending on the stretching equipment, or may cause breakage problems during film stretching. Frequently occurring and unable to perform stable production,
There are other problems. By the way, some of the inventors of the present invention have already made a proposal regarding synthetic paper that is improved in terms of paper dust problems (Japanese Patent Application No. 139674/1982). The synthetic paper according to this prior invention is a synthetic paper having a paper-like layer made of a stretched film of a polyolefin composition containing an inorganic filler, in which a part of the polyolefin is graft-copolymerized with ethylenically unsaturated carboxylic acid, etc. be. The synthetic paper according to this prior invention has a multilayer structure consisting of one specific base material layer and this paper-like layer, and the thickness of the paper-like layer (after stretching) in this case is the sum of the front and back layers. 40-50 for multilayer structures
% (base material layer 50-60 microns, paper-like layer
25 microns x 2). Therefore, the synthetic paper according to this prior invention had the above-mentioned problems regarding stretching. The present inventors have made a proposal to solve the problems of this prior invention regarding stretching (Japanese Patent Application No. 41307/1982). [] Summary of the Invention The present invention aims to solve the above points, particularly the problems recognized in the case of improving interfacial adhesion between resin/filler particles, and provides an additive for improving interfacial adhesion. This objective is achieved by blending only into a thin surface layer to form a laminated structure. Therefore, the thermoplastic resin film with excellent printability according to the present invention has a multilayer structure consisting of a base layer and a printable surface layer made of a stretched film of an inorganic filler-containing polyolefin composition provided on at least one side of the base layer. The film is characterized in that the surface layer is defined as below. (1) The thickness of the surface layer shall be 1/6 or less of the thickness of this multilayer structure film and 3 microns or more. (2) Having minute voids. (3) The inorganic filler-containing polyolefin composition forming the surface layer must contain a modified polyolefin copolymerized with a polyolefin (excluding polypropylene) unsaturated carboxylic acid or its anhydride. Effects Modified polyolefin (excluding polypropylene) as a resin/filler particle interfacial adhesion enhancer is blended only in the surface layer, and this surface layer is made sufficiently thin to prevent the filler from falling off during secondary processing. It has now become possible to stably and economically produce thermoplastic resin films that are The thermoplastic resin film with excellent printability according to the present invention is particularly suitable for use as synthetic paper. [] Detailed Description of the Invention The thermoplastic resin film with excellent printability according to the present invention is a multilayer structure film consisting of a base layer and a surface layer, and because this surface layer is specified, it is different from conventional films. This type of paper is distinguished from film or synthetic paper. 1 Surface Layer The surface layer consists of a stretched film of a polyolefin (excluding polypropylene) composition containing an inorganic filler provided on at least one side, preferably both sides, of the base layer. This film has paper-like properties due to the mechanism described above, and also contains modified polyolefin (excluding polypropylene) in accordance with one of the features of the present invention. In the present invention, the "surface layer" refers to the inorganic filler and modified polyolefin (excluding polypropylene) present on the surface in relation to the base material layer.
means a layer containing Therefore, even if the multilayer structure film of the present invention comprising such a base layer and a surface layer has some kind of layer on the surface layer and this surface layer is buried, this layer can be removed from the surface. It's called a layer. 1 Modified polyolefin (excluding polypropylene) The modified polyolefin used as the resin/filler particle interfacial adhesion enhancer in the present invention is a combination of polyolefin (excluding polypropylene) and ethylenically unsaturated carboxylic acid or its anhydride (hereinafter, modified). It is a copolymerized product of monomers (sometimes referred to as monomers). In this case, the polyolefin is a homopolymer of olefin other than propylene, and has 2 to 2 carbon atoms.
A copolymer of α-olefin of No. 8 (however, in the case of a copolymer containing propylene, the content of propylene units should be 20% or less, preferably 5% or less (all percentages by weight)), or Mixtures thereof may be mentioned as some specific examples. Ethylenically unsaturated carboxylic acids (and their anhydrides) may include maleic acid, itaconic acid, hemicic acid (and their respective acid anhydrides), acrylic acid, and others. Particularly effective in preventing desorption of filler particles according to the present invention are maleic acid and maleic anhydride. Since this reaction is a copolymerization of the polymer polyolefin and the monomer ethylenically unsaturated carboxylic acid or its anhydride, this reaction belongs to the category of so-called graft copolymerization. Graft copolymerization techniques are already known, and the modified polyolefin for the present invention can be obtained by any of these methods, but typical graft copolymerization techniques are classified according to the type of polymerization initiation. For example, it is as follows. (i) A method in which maleic anhydride and polyolefin are subjected to suspension polymerization in an aqueous solution in the presence of a radical initiator. (ii) A method in which a resin composition containing a radical initiator is melt-kneaded using heat and shear force in a kneader. The modified polyolefin produced in this way is a mixture of a graft copolymerized polyolefin, a polyolefin that did not participate in the graft copolymerization, and optionally a polymer of a modifying monomer (the modifying monomer is In the case of a monomer with a large absolute value of the so-called e value, such as maleic acid, almost no polymer of itself will be formed). In such a case,
Since it is virtually impossible and not practical to define the amount of carboxylic acid residues in the modified polyolefin by the weight percentage of the graft copolymer in the modified polyolefin, The amount of carboxylic acid residue is determined by the content of the modified monomer obtained. Further, the content of the modified polyolefin in the polyolefin composition for the surface layer is also defined by the amount of the polymerized modifying monomer (details will be described later). The modified polyolefin used in the present invention preferably has a content of such polymerized modifying monomer of 0.01 to 5% by weight, particularly 0.02 to 2% by weight. 2 Inorganic filler Any fine inorganic filler that can be blended into polyolefin (excluding polypropylene) can be used as the inorganic filler for the surface layer of the present invention. Specific examples of such inorganic fillers include clay, titanium oxide, barium sulfate, calcium carbonate, silica, alumina, silicate, magnesium carbonate, calcium sulfite, diatomite, and gypsum. Among these, calcium carbonate is particularly preferred for use in the present invention because it has good printing effects, high whiteness, and low abrasion. Since the number of defects and falling off from the stretched film is extremely high, the effect of improving the adhesiveness of the modified polyolefin according to the present invention is particularly noticeable. The inorganic filler is granular and has an average particle size of 0.3~
Preferably it is 20 microns, especially 0.5 to 5 microns. If it is less than 0.3 microns, voids will not be effectively generated, resulting in poor whitening, and secondary aggregation of the filler will occur, resulting in poor dispersion into the resin. When it exceeds 20 microns, the surface of the molded product (film) becomes rough and the void generation rate per unit weight of filler becomes small. The shape of the particles of the inorganic filler is basically arbitrary, and may be, for example, spherical, rod-shaped, conical, pyramidal, or other shapes within the range of granular shapes. However, from the viewpoint of void generation, it is preferable that the material is not flat. The blending amount of the filler is appropriately selected depending on the intended use of the film to be obtained (details will be described later). In addition, when calcium carbonate is blended as an inorganic filler, 0.1 to 3% by weight of oleic acid is used as a dispersant, and 2.6-di-tertiary butyl para-cresol and octadecyl-3-(3,5-di-tertiary) are used as antioxidants. 0.1 to 2% by weight (based on resin) in combination with butyl-4-hydroxyphenyl) propionate
This is preferable since there is no change in hue when blended. 3. Polyolefin (excluding polypropylene) composition for surface layer The surface layer consists of a polyolefin (excluding polypropylene) composition containing an inorganic filler, and this composition contains the modified polyolefin as described above. Here, the fact that the surface layer polyolefin composition contains a modified polyolefin means that the composition is not only composed of the modified polyolefin as a resin component, but also when it is a mixture with an "unmodified" polyolefin. It also includes.
Regarding the type of unmodified polyolefin in this case, the above explanation regarding the modified polyolefin applies. The polyolefin composition for the surface layer consists of two essential components: a modified polyolefin and an inorganic filler (and non-essential or auxiliary components added as necessary). The amount of the inorganic filler to be added is appropriately selected depending on the intended use of the film to be obtained. In the case of films intended for use in printing and writing paper applications where printing or writing is often performed (sometimes referred to as synthetic paper), the content in the polyolefin composition for the surface layer is between 12 and 12. 70% by weight, especially
It is preferably 30 to 70% by weight. This is because if it is less than 12%, printability or writability will not be sufficient, and if it exceeds 70%, the surface smoothness and surface strength will be low, which is disadvantageous. In addition, when the multilayer structure film of the present invention is used as synthetic paper, there is a preferable range for the filler content of the multilayer structure film as a whole. 8-40% by weight, especially 15-40% by weight. If it is less than 8%, the quality of the resulting multilayer film as synthetic paper will be poor, so in order to satisfy the minimum whiteness, opacity, writability, printability, etc. of synthetic paper, it is necessary to use at least 8%.
%is necessary. If it exceeds 40%, the strength and surface properties of the paper will be insufficient. Since the purpose of blending the modified polyolefin is to prevent the filler from detaching, it is reasonable to specify the amount of the modified polyolefin based on the amount of the filler. The amount of polymerized modifying monomer in the modified polyolefin is 0.01 to 5 parts by weight, particularly 0.03 to 0.15 parts by weight, relative to 100 parts by weight of the inorganic filler in the polyolefin composition for the surface layer. The amount of modified polyolefin is preferred. If it is less than 0.01 part, the adhesive effect of the filler is small,
Prevention of paper dust problems is insufficient. If the amount exceeds 5 parts, the polyolefin composition undergoes significant hue change and deterioration due to heat, and cannot be used for practical printing purposes. Such a composition consisting of two essential components is a thermoplastic resin composition containing polyolefin as the main resin component, and therefore can contain various non-essential or auxiliary components that thermoplastic resin compositions normally contain. Such aids include, for example, compatible resins, antioxidants, ultraviolet absorbers, dyes and pigments, fluorescent brighteners, and the like. An example of a compatible resin is a polyolefin that has not undergone the above-mentioned modification, but in a polyolefin composition in which a modified polyolefin, an unmodified polyolefin, and a filler are mixed, the molded product is homogeneous. It is preferable that the type of polyolefin of the base resin of the modified polyolefin and the non-modified polyolefin are the same type from the viewpoint of properties, dispersion effect of the filler, etc. 4 Surface Layer Thickness The thickness of the surface layer should be at least 3 microns in the multilayer structure film after stretching. If it is less than 3 microns, the intended effect of preventing filler from falling off is not sufficient. On the other hand, if the thickness of the surface layer is too large, the forming stability will be poor when carrying out a stretching process to obtain a multilayer structure film having such a surface layer.
Fractures often occur during stretching. Therefore, the thickness of the surface layer should be 1/6 or less of the thickness of the multilayer film after stretching. Note that the thickness of the surface layer here refers to a single layer of the surface layer. Therefore, if surface layers exist on both sides of the base material layer, the total thickness is 1/3 of the thickness of the multilayer structure film. This means the following. When there are two layers, the preferred thickness is 1/5 or less. 5. Stretching In order for surface cracks to be generated as described above, the surface layer should be stretched. The stretching may be uniaxial or biaxial stretching, but in the case of a preferred production method described later, uniaxial stretching is usually used (the stretching ratio will be described later). 6 Void Since it is stretched in this way,
There are more than 50 cracks/m ² on the surface of the surface layer, and voids inside the surface layer. From the viewpoint of writability and printability, the void ratio of the surface layer is preferably 10% or more. Note that the void ratio is defined by the following formula. Void ratio (%) = Specific gravity of the film before stretching - Specific gravity of the film after stretching / Specific gravity of the film before stretching 2 Base layer Should have a surface layer made of the polyolefin composition as described above on one or both sides. Various film materials can be used as the base layer. This base material layer may also have a multilayer structure itself (details will be described later). The material for the base layer may be any suitable material, but it is usually one that can be stretched if the preferred manufacturing method described below is followed. Various thermoplastic resins can be used as stretchable materials for the base layer, but polyolefin is preferred among them. Examples of polyolefin include polypropylene, high density polyethylene, medium and low density polyethylene, etc.
It is possible to use either the same kind of resin as the surface layer main resin or a different kind, but the same kind is preferable from the viewpoint of reuse of burrs and adhesion between the surface layer and the base material layer. The base material layer preferably has good stretchability, and therefore the resin to be used preferably does not substantially contain the above-mentioned modified polyolefin. As mentioned above, it is preferable that the base layer also contains an inorganic filler, but if both the filler and the modified polyolefin are contained, the stretchability will deteriorate. The base material layer is also preferably uniaxially or biaxially stretched. The base layer may also contain auxiliary components as described above for the surface layer. In addition, there are many fine voids inside (porosity: 5
~30%), the paper-like texture is better. As mentioned above, the base material layer itself may have a multilayer structure. An example of such a multilayer structure is one consisting of a biaxially oriented layer and a uniaxially oriented layer bonded preferably on both sides thereof. In this case, the two layers differ in the filler content and/or in the type of resin used (differences due to resin type or melting properties), but this difference is purposefully determined from the point of view of the production of the stretched film. be done. Note that when the surface layer is made of a uniaxially stretched film and the base layer is made of a biaxially stretched film, and the main resins constituting the surface layer and the base layer are of the same type, the base layer is made of a uniaxially stretched film to facilitate stretching. The resin composition of the material layer may contain a thermoplastic resin that is compatible with the main resin and whose melting point is 10°C or more lower than the melting point of the main resin at a ratio of 5 to 50% by weight (based on the main resin). preferable. 3. Manufacturing Some preferred methods for manufacturing the multilayer structure film of the present invention are as follows, for example. (1) Materials for the base layer, such as polyolefin, and inorganic fillers and auxiliary components used as necessary are mixed, kneaded in an extruder, and then formed into a sheet. Place this sheet lengthwise at least
After stretching 1.3 times, on one or both sides,
Materials for the surface layer, ie, modified polyolefin, inorganic filler, and if necessary, unmodified polyolefin, are mixed, kneaded in an extruder, extruded into a sheet, and laminated when melted. The multilayer sheet is stretched at least 3.5 times in the transverse direction. (2) When extrusion laminating a surface layer sheet on one or both sides of the base layer sheet as described above, polyolefin, preferably polyolefin (unmodified), and inorganic filling are added between both sheets. After melt-kneading the mixture with the agent in a separate extruder, it is coextruded from the same die as the sheet for the surface layer to produce a three-layer to five-layer sheet, which is then stretched in the same manner as above. According to this aspect (2), the base material layer itself has a multilayer structure. In other words, it has a multilayer structure consisting of a biaxially stretched layer and a uniaxially stretched layer (formed at the same time as the surface layer) between this layer and the surface layer (layer containing modified polyolefin). . When the base material layer has such a multilayer structure according to the embodiment (2), there are competitive requirements for the base material layer, that is, the base material layer has good biaxial stretchability and has a somewhat high filler content. Being able to skillfully fulfill the following. That is, a biaxially oriented layer is made from a composition that has a relatively low content of a resin and/or filler that is relatively easy to stretch biaxially, and a composition that has a relatively high content of a resin and/or filler that is relatively difficult to stretch biaxially. By forming a uniaxially oriented layer from the composition to form a multilayer structure, it is possible to combine the good mechanical properties and isotropy of a biaxially oriented film with the high brightness or opacity of a oriented film with a high filler content. This is because the base material layer included therein can be easily obtained. 4 Experimental Examples In order to make the present invention easier to understand, the following examples will be used to explain the invention. These examples constitute one aspect of the present invention, and can be arbitrarily modified within the scope of the present invention. Example 1 and Comparative Example 1 (1) 95 parts by weight of melt index (MI) 1.2 high-density polyethylene (density 0.96 g/cm ³ ) and 5 parts by weight of MI8 low-density polyethylene (density 0.918 g/cm ³ ), average Calcium carbonate 20 with particle size 1.5 microns
After mixing parts by weight and premixing with a mixer, this mixture is melt-kneaded with an extruder, extruded into a sheet, and then cooled with a cooling device to form a sheet with a thickness of 1.8 mm.
I got a sheet of The sheet was then heated to 135° C. and then stretched 4 times in the longitudinal direction by utilizing the difference in circumferential speed between the roll groups. (2) Polyethylene of MI 1.1 (density 0.96g/cm ³ )
100 parts by weight of maleic anhydride, and 5 parts by weight of benzoyl peroxide (BPO) in 600 parts by weight of xylene.
After reacting in parts by weight at 120°C for 5 hours, a large excess of acetone was added and reprecipitation was performed to obtain powdered polyethylene modified with maleic anhydride. When the grafted concentration of maleic anhydride in this polymer was determined by infrared absorption spectrum, maleic anhydride corresponding to 0.6% by weight was detected. (3) After melt-kneading the following compositions (A) and (B) in separate extruders, introduce them into the same die through a conduit and laminate them in the die, then create the longitudinal direction obtained in (1) above. It was extruded and laminated on both sides of the stretched sheet, and immediately pressed and cooled with a roll so that the layer made of composition (A) was on both outer sides and the layer made of composition (B) was made to be an adhesive layer.5 A layered sheet was obtained. Next, this 5
The laminated body was heated to 135° C. and then stretched 7 times in the transverse direction using a tenter stretching machine to obtain a 5-layer film. (A) ● 100 parts by weight of polyethylene with a density of 0.96 g/cm ³ ● 8 parts by weight of the modified polyethylene obtained in (2) ● 80 parts by weight of calcium carbonate (“Whiten #1500” manufactured by Shiraishi Calcium Co., Ltd.) ● 2,6-ditert-butyl para-cresol
0.2 parts by weight ● Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate
0.2 parts by weight ● Oleic acid 0.3 parts by weight (B) ● Polyethylene with a density of 0.96 g/cm ³ 100 parts by weight ● Calcium carbonate ("Whiten #1500" manufactured by Shiroishi Calcium Co., Ltd.) 80 parts by weight ● 2,6-di Tertiary butylparacresol
0.2 parts by weight ● Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate
0.2 parts by weight (4) Also, as Comparative Example-1, using the composition (A) of (3) that does not contain modified polyethylene, (3)
A 5-layer laminate was obtained in the same manner as above, and then stretched under the same conditions as in (3) to obtain a 5-layer film. (5) As Comparative Example-2, using only composition (A) of (3),
Laminated on both sides of the longitudinally stretched sheet obtained in (2) to the same thickness as the five-layer body of (3) and (4),
The obtained three-layer laminated sheet was stretched under the same conditions as in (3). (6) The properties of the obtained films are as compared in Table 1. The film obtained in Example 1 had less filler falling off during offset printing and could be produced stably.

[Table] Example 2 (1) 95 parts by weight of polyethylene with a density of 0.96, density
5 parts by weight of polyethylene having a particle diameter of 0.918 and 20 parts by weight of calcined clay having an average particle size of 1.2 microns were mixed, melt-kneaded using an extruder, extruded into a sheet, and cooled to obtain a non-stretched sheet. This sheet is 130
After heating to 0.degree. C., the film was stretched 4 times in the longitudinal direction to obtain a longitudinally stretched film. (2) Polyethylene modified with maleic anhydride by mixing 100 parts by weight of MI 1.0 polyethylene, 15 parts by weight of maleic anhydride, and 5 parts by weight of benzoyl peroxide (BPO) and kneading in a kneader. I got it. After reprecipitating this polymer with acetone to remove unreacted maleic anhydride, the content of maleic anhydride craft in the polymer was determined using an infrared absorption spectrum. An equivalent amount of acid was detected. (3) A composition was prepared by mixing the modified polyethylene obtained in (2) in the following proportions.

【table】

[Table] Mixing the additives necessary for this composition, Example -
Similarly to 1, coextrusion was carried out with a composition prepared by mixing 55% by weight of polyethylene with a density of 0.96 g/cm ³ and 45 parts by weight of calcined clay with an average particle size of 1.5 μm, and the vertical Both sides of the stretched sheet were laminated, and after cooling and pressing, the sheet was heated again to 135°C and then stretched 7 times in the transverse direction. The evaluation of the obtained film is as shown in Table 3.

[Table] Example 3 (1) 90 parts by weight of polyethylene with a density of 0.96 g/ ^cm3 , 10 parts by weight of polyethylene with a density of 0.92 g/ ^cm3 , and 20 parts by weight of calcined clay with an average particle size of 1.2μ were mixed and extruded. After melt-kneading in a machine, it was extruded into a sheet and cooled to obtain a sheet with a thickness of 2.0 mm. Heat this sheet to 130℃
After heating, the film was stretched 5 times in the longitudinal direction to obtain a longitudinally stretched film. (2) 100 parts by weight of polyethylene with a density of 0.92 g/ ^cm3 ,
Modified polyethylene 8 obtained in Example-2 (2)
Composition (A) in which 80 parts by weight of calcined clay with an average particle size of 1.2μ and a processing stabilizer are mixed, and a density of 0.92
100 parts by weight of polyethylene in g/ ^cm3 , average particle size
Composition (B), which is a mixture of 80 parts by weight of 1.2μ calcined clay and 1 part by weight of processing stabilizer, was melt-kneaded in a separate extruder, and composition (A) was prepared in the same manner as in Example-1 (3). A five-layer sheet was obtained in which the outer surface was Next, this 5-layer laminate was heated to 135°C and then stretched 8 times in the transverse direction to obtain a 5-layer laminate film. In offset printing, the obtained film could print more than 4,000 sheets before continuous printing became impossible due to filler falling off, and the production was stable. Example 4 (1) 100 parts by weight of polyethylene with a density of 0.96 g/cm ³ and 20 parts by weight of calcined clay with an average particle size of 1.2 μm were mixed, melt-kneaded in an extruder, and then extruded into a sheet.
A sheet with a thickness of 2.0 mm was obtained by cooling. After heating this sheet to 130°C, it was stretched 5 times in the longitudinal direction,
A longitudinally stretched film was obtained. (2) 1100 parts by weight of polybutene with a density of 0.91 g/ ^cm3 , 8 parts by weight of the modified polyethylene obtained in (2) of Example 2, and 8.0 parts by weight of calcined clay with an average particle size of 1.2μ, making it stable for processing. Composition (A) containing 1 part by weight of
and 100 parts by weight of polyethylene with a density of 0.96 g/ ^cm3 ,
Composition (B), which is a mixture of 80 parts by weight of calcined clay with an average particle size of 1.2μ and 1 part by weight of a processing stabilizer, was melt-kneaded in a separate extruder, and the composition was prepared in the same manner as in Example 1 (3). A five-layer sheet with (A) as the outer surface was obtained.
Next, this 5-layer laminate was heated to 135°C and then stretched 8 times in the transverse direction to obtain a 5-layer laminate film. The obtained film could print 3,000 sheets in offset printing before continuous printing became impossible due to filler falling off, and the production was stable.

Claims (1)

[Scope of Claims] 1. A multilayer structure film consisting of a base layer and a printable surface layer made of a stretched film of an inorganic filler-containing polyolefin composition provided on at least one side of the base layer, where this surface layer is as follows: A thermoplastic resin film with excellent printability, characterized in that it is defined by: (1) The thickness of the surface layer shall be 1/6 or less of the thickness of this multilayer structure film and 3 microns or more. (2) Having minute voids. (3) The inorganic filler-containing polyolefin composition forming the surface layer must contain a modified polyolefin in which polyolefin (excluding polypropylene) and ethylenically unsaturated carboxylic acid or its anhydride are copolymerized.