WO2019087979A1 - Thermoplastic resin film and inkjet paper - Google Patents

Abstract

Provided are a thermoplastic resin film and an inkjet paper which have excellent printability for aqueous pigment ink. This thermoplastic resin film has a substrate layer and a porous layer on at least one surface of the substrate layer, wherein: the water absorption amount per unit area of the porous layer is 0.1 g/m2 or less; when a first liquid having a surface tension of 30 mN/m is dripped onto the porous layer and left to stand for 5 minutes, the first liquid permeates; and when a second liquid having a surface tension of 44 mN/m is dripped onto the porous layer and left to stand for 5 minutes, the second liquid does not permeate.

Description

Thermoplastic resin film and inkjet paper

The present invention relates to a thermoplastic resin film and an inkjet paper.

In ink jet printing, various inks such as water-based ink, oil-based ink, and ultraviolet curable ink are used. The ink penetrates the paper or hardens on the surface of the paper to fix the ink to the paper. As the paper, not only the conventional fibrous paper but also a thermoplastic resin film is used as an inkjet paper capable of vividly printing an image.

As an inkjet paper suitable for aqueous ink, a biaxially stretched resin film is proposed (see, for example, Patent Document 1). This biaxially stretched resin film exhibits high water permeability by containing an inorganic fine powder surface-treated with a water-soluble cationic surfactant having a relatively low molecular weight, and the aqueous ink easily penetrates.

In addition, it contains an inorganic fine powder having a water absorbing layer on at least one surface, and the water absorbing layer is surface-treated with a water-soluble cationic polymer and then surface-treated with a water-soluble anionic surfactant to impart hydrophilicity. Also, there is disclosed a resin stretched film which exhibits water absorbency by conducting the reaction (see, for example, Patent Document 2).

There is also an inkjet paper provided with a coat layer having high affinity with ink on the outermost surface in order to improve printability. For example, an ink jet recording sheet is also proposed in which an image receiving layer for improving printability is provided on a water absorbing layer having a porous structure to which aqueous ink easily penetrates (see, for example, Patent Document 3). Moreover, the resin film for inkjet printing which provided the coating layer which improves affinity with an ink on a porous layer is also proposed by surface-treating a porous layer (for example, refer patent document 4).

However, the conventional inkjet paper has high affinity with water as well as ink. Therefore, when the dye penetrates the film together with the water as in the case of the aqueous dye ink, the dye may exude from the film when it gets wet after printing. On the other hand, although the water-based pigment ink is superior in water resistance to the water-based dye ink, when printed on a film, only water penetrates into the film and the pigment remains on the surface of the film to be rubbed. It is easy to drop off.

In addition, the water-based pigment ink generally contains a solvent for the purpose of preventing clogging of the ink jet head and the like, and the absorption speed and the wetting spread of the ink are different from those of water. When the ink absorption speed is low, in the case of multi-color printing, the inks of the respective colors are mixed and bleeding is likely to occur, and even when the films are superimposed, the ink is easily transferred to another film. In addition, when the spread of the ink is too large, it becomes easy to be observed as bleeding.

JP, 2012-092213, A JP, 2014-080025, A JP 2017-124531 A JP, 2011-131416, A

An object of the present invention is to provide a thermoplastic resin film and an inkjet paper having excellent printability with respect to an aqueous pigment ink.

As a result of intensive investigations by the present inventors to solve the above problems, it was found that the above problems can be solved by a porous layer having a small amount of water absorption and exhibiting a certain permeability to a liquid having a specific surface tension. , Completed the present invention.

That is, according to one aspect of the present invention,
(1) base material layer,
A porous layer on at least one surface of the substrate layer,
The water absorption amount per unit area of the porous layer is 0.1 g / m ² or less,
When the first liquid having a surface tension of 30 mN / m is dropped onto the porous layer and left for 5 minutes, the first liquid penetrates, and the second surface having a surface tension of 44 mN / m is formed on the porous layer. When the liquid is dropped and left for 5 minutes, the second liquid does not permeate.
There is provided a thermoplastic resin film characterized in that.

According to another aspect of the invention,
(2) base material layer,
A thermoplastic resin film having a porous layer on at least one surface of the substrate layer,
The porous layer is a layer containing a thermoplastic resin and 30 to 70% by mass of an inorganic filler whose surface is coated with a cationic polymer,
The average particle size of the inorganic filler is 0.3 to 5 μm,
The thermoplastic resin film is characterized in that the water absorption amount per unit area of the porous layer is 0.1 g / m ² or less.

According to another aspect of the invention,
(3) A thermoplastic resin film having a substrate layer, a porous layer, and a coating layer in this order,
The porous layer is a layer containing a thermoplastic resin and 30 to 70% by mass of an inorganic filler whose surface is coated with a cationic polymer,
The average particle size of the inorganic filler is 0.3 to 5 μm,
A thermoplastic resin film is provided, wherein the coating layer contains a cationic polymer.

(4) The porous layer is a multilayer,
The outermost layer of the porous layer is a layer containing a thermoplastic resin and 30 to 70% by mass of an inorganic filler whose surface is coated with a cationic polymer,
The layer adjacent to the outermost layer is preferably a layer containing a thermoplastic resin and an inorganic filler whose surface is coated with an anionic hydrophilizing agent.

According to another aspect of the invention,
(5) An inkjet paper comprising the thermoplastic resin film of (3) or (4) is provided.

ADVANTAGE OF THE INVENTION According to this invention, the thermoplastic resin film and inkjet paper which have the outstanding printability with respect to water-based pigment ink can be provided.

It is sectional drawing which shows the structure of the thermoplastic resin film of one embodiment of this invention. It is sectional drawing which shows the structure of the thermoplastic resin film of one embodiment of this invention.

Hereinafter, the details of the thermoplastic resin film and the inkjet paper of the present invention will be described, but the configuration described below is an example (representative example) as an embodiment of the present invention, and the present invention is limited to the contents described. I will not.
In the following description, a numerical range represented by using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value. Moreover, the description of "(meth) acrylate" indicates both acrylate and methacrylate. The same applies to the description of (meth) acrylic acid derivatives and the like.

[Thermoplastic resin film]
The thermoplastic resin film of the present invention has a substrate layer and a porous layer on at least one surface of the substrate layer. The porous layer may be only one layer, but the thermoplastic resin film of the present invention may have a porous layer as a multilayer structure and may have a plurality of porous layers on the base layer. If the porous layer has a multilayer structure, it is preferable because the characteristics can be made different in each layer to exhibit various functions.

FIG. 1 shows the structure of a thermoplastic resin film having a porous layer having a multilayer structure as an embodiment of the present invention.
As shown in FIG. 1, the thermoplastic resin film 1 preferably has a base layer A and two porous layers B1 and B2 on one side of the base layer A.

[Base layer]
The base material layer can impart strength (stiffness) to the thermoplastic resin film. As a base material layer, a thermoplastic resin excellent in mechanical strength can be preferably used.

(Thermoplastic resin)
As a thermoplastic resin which can be used for a base material layer, polyolefin resin, a polyamide resin, polyester resin, polycarbonate resin, a polystyrene resin, poly (meth) acrylate resin, polyvinyl chloride resin, these mixed resins etc. are mentioned, for example. Among them, polyolefin resins are preferable from the viewpoint of water resistance and solvent resistance. Moreover, it is preferable from being excellent in the adhesiveness with a porous layer, and the durability of a thermoplastic resin film improving that it is a thermoplastic resin of the same kind as a porous layer.

As polyolefin resin, polypropylene resin, polyethylene resin etc. can be used preferably.
Examples of the polypropylene resin include propylene homopolymers such as isotactic homopolypropylene and syndiotactic homopolypropylene obtained by homopolymerizing propylene, mainly composed of propylene, ethylene, 1-butene, 1-hexene, 1-heptene, 1 And propylene copolymers obtained by copolymerizing α-olefins such as octene and 4-methyl-1-pentene. The propylene copolymer may be a binary system, a ternary system or a multicomponent system, and may be a random copolymer or a block copolymer.

Examples of the polyethylene resin include, for example, high density polyethylene, medium density polyethylene, linear linear low density polyethylene, ethylene and the like, and α-olefin such as propylene, butene, hexene, heptene, octene, 4-methylpentene-1 etc. Polymerized copolymer, maleic acid modified ethylene / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid alkyl ester copolymer, ethylene / methacrylic acid alkyl ester Examples thereof include copolymers, metal salts of ethylene / methacrylic acid copolymers (metals are zinc, aluminum, lithium, sodium, potassium and the like), ethylene-cyclic olefin copolymers, maleic acid-modified polyethylene and the like.
Among the above-mentioned polyolefin resins, propylene homopolymer or high density polyethylene is preferable from the viewpoint of moldability and cost.
Among the above-mentioned thermoplastic resins, one kind can be used alone or two or more kinds can be used in combination.

(Other ingredients)
The thermoplastic resin film which is a base material layer can optionally contain known additives as needed. Additives include antioxidants, light stabilizers, ultraviolet light absorbers, dispersants of inorganic fillers, crystal nucleating agents, antiblocking agents, plasticizers, slip agents such as fatty acid amides, dyes, pigments, mold release agents, difficult Well-known adjuvants, such as a flame retardant, are mentioned.

From the viewpoint of enhancing the outdoor durability, the base material layer preferably contains an antioxidant, a light stabilizer, and the like.
Examples of the antioxidant include sterically hindered phenol-based antioxidants, phosphorus-based antioxidants, amine-based antioxidants and the like.
Examples of light stabilizers include sterically hindered amine light stabilizers, benzotriazole light stabilizers, and benzophenone light stabilizers.
The content of the antioxidant and the light stabilizer is preferably in the range of 0.001 to 1% by mass with respect to the mass of the thermoplastic resin film as the base layer.

The base material layer can contain a filler to such an extent that the strength is not lost. The base material layer may be a non-oriented film or a stretched film from the viewpoint of enhancing the strength. By using a stretched film of a thermoplastic resin containing a filler as the substrate layer, the rigidity, whiteness and opacity of the substrate layer can be adjusted according to the purpose. As a filler, the inorganic filler mentioned by the porous layer mentioned later can be used. The inorganic fillers of the base layer and the porous layer may be the same or different.

The thickness of the base material layer can be appropriately determined according to the thickness of the porous layer and the use or purpose of the thermoplastic resin film. In general, the thickness of the base material layer is preferably 15 μm or more, more preferably 20 μm or more, and still more preferably 30 μm or more, from the viewpoint of obtaining sufficient stiffness. The thickness of the substrate layer is preferably 400 μm or less, more preferably 300 μm or less, and still more preferably 200 μm or less.

[Porous layer]
The porous layer is a layer capable of printing using an inkjet method. The porous layer has a water absorption amount per unit area of 0.1 g / m ² or less. In the porous layer, when the first liquid having a surface tension of 30 mN / m is dropped on the porous layer and left for 5 minutes, the first liquid permeates, and the surface tension of 44 mN / m on the porous layer And the second liquid does not penetrate when left for 5 minutes. The static contact angle of water on the surface of the porous layer measured according to JIS R 3257: 1999 is preferably 115 degrees or more, more preferably 120 degrees or more, and still more preferably 125 degrees or more. The static contact angle of water is usually below 170 degrees.

In such a porous layer, while water with high surface tension hardly penetrates, the surface tension is usually in the range of 30 to 42 mN / m by the water-soluble organic solvent added for preventing clogging of the inkjet head and the like. Some aqueous pigmented inks penetrate. Since the aqueous pigment ink rapidly penetrates into the porous layer, even when the aqueous pigment inks of a plurality of colors are stacked, the ink is not mixed, and bleeding when multicolor printing is performed is small. Since the porous layer having good ink permeability is excellent in the drying property of the ink, it is possible to reduce the ink transfer when another sheet of paper is stacked on the film. After penetration, the pigment component remains in the pores inside the porous layer, so that a thermoplastic resin film excellent in abrasion resistance can be obtained.

In addition, when the first liquid having a surface tension of 30 mN / m is dropped and left for 5 minutes, the porous layer having a permeability in which the first liquid is excessively wet and spreads excessively expands dots of the aqueous pigment ink, It is presumed that the cause is a decrease in the sharpness of the inkjet image. The porous layer exhibiting the permeability of the present invention is also considered to be one of the factors causing less bleeding, because it can suppress excessive wetting and spreading of the ink. Empirically, it is preferable that the diameter of the approximate circle is 5 cm or less when the outermost part of the spread of the liquid mark after wiping the liquid droplets left on the first liquid for 5 minutes is approximated by a circle.

In the case where a plurality of porous layers are provided on any one side of the base material layer, the water absorption amount and the permeability of the porous layer located at least on the outermost surface among the plurality of porous layers are the above conditions. It should be satisfied.

The water absorption amount is measured in accordance with JIS P8140: 1998. The water absorption amount is preferably 0.05 g / m ² or less, and may be 0.0 g / m ² as a measurement value.
Further, the permeability is judged by the spread of a liquid mark after each 20 μL of the first liquid and the second liquid are dropped on the surface of the object to be measured and left for 5 minutes. Specifically, the outermost part of the spread of the liquid mark after wiping off the surface droplets left for 5 minutes is approximated by a circle, and if the diameter of the approximate circle is 2 cm or more, it is judged that penetration has occurred. If there is, we will judge that it does not penetrate.

The porous layer is a thermoplastic resin film containing 30-70% by mass of a thermoplastic resin and an inorganic filler surface-treated with a cationic polymer. The formation of the porous layer having pores is facilitated, and the formation of the porous layer exhibiting the water absorption and permeability is facilitated.

From the viewpoint of enhancing the adhesion between the porous layer and the base material layer, it is adjacent to the base material layer between the porous layer containing the inorganic filler surface-treated with the cationic polymer and the base material layer, It is preferable to further provide a porous layer having a water absorption of not more than 0.1 g / m ² .

When the porous layer has a multilayer structure and has a plurality of porous layers on one side of the base layer, ie, between the base layer and the porous layer exhibiting the above water absorption and permeability, In the case of having one or more porous layers, expression of the above-mentioned water absorption amount and permeability becomes easy, so the outermost layer among the plurality of porous layers on the base layer, that is, the outermost side opposite to the base layer The porous layer located on the surface is a thermoplastic resin film containing 30 to 70% by mass of an inorganic filler (surface treated with a cationic polymer) whose surface is covered with a cationic polymer. Inorganic filler (surface-treated by an anionic hydrophilic agent) whose inner porous layer adjacent to the outermost layer (porous layer located on the outermost surface) is coated with an anionic hydrophilic agent It is preferable that it is a thermoplastic resin film containing In addition, if the inorganic filler surface-treated by the anionic hydrophilic agent has the surface treatment layer of the anionic hydrophilic agent on the outermost surface, the surface is treated by the cationic polymer and then the surface is treated by the anionic hydrophilic agent. It may be a treated inorganic filler.

The porous layer located on the outermost surface opposite to the substrate layer contains an inorganic filler whose surface is covered with a cationic polymer, whereby the coloring material which is anionic is layered from the surface of the porous layer The effect of adsorbing to the inside is exhibited, and the density of the inkjet image can be increased, and the sharpness can be enhanced. On the other hand, when the porous layer adjacent to the outermost porous layer contains an inorganic filler whose surface is covered with an anionic hydrophilizing agent, the water-soluble organic solvent penetrates to the deep part of the porous layer As a result, the effect of separating the coloring material and the water-soluble organic solvent is developed, and the drying property of the ink and the fixing property of the coloring material can be improved.

From the viewpoint of enhancing the adhesion between the porous layer having a multilayer structure and the substrate layer, the substrate layer may be provided between the porous layer containing the inorganic filler coated with an anionic hydrophilizing agent and the substrate layer It is preferable that a porous layer having no water absorbency, that is, a water absorption amount of 0.1 g / m ² or less be further provided.

(Thermoplastic resin)
As a thermoplastic resin which can be used for a porous layer, the said thermoplastic resin mentioned by the base material layer can be used. Among them, from the viewpoint of obtaining sufficient strength, a polyolefin resin is preferable, and a polypropylene resin or a polyethylene resin is more preferable.

From the viewpoint of improving the abrasion resistance, it is preferable to use a polypropylene resin and a resin having a melting point lower than that of the polypropylene resin in combination. By using a polypropylene resin that can easily obtain sufficient strength of the porous layer in combination with a resin that is easier to melt than a polypropylene resin, the fibrillar porous layer that easily holds the pigment component can be easily formed. . In addition, even when the content of the inorganic filler is the same, the porosity of the porous layer is increased, so that the liquid absorption amount of the ink can be increased.

The content of the polypropylene resin in the porous layer is preferably 20 to 70% by mass. Within this range, the polypropylene resin can be easily stretched in a non-melted state, and sufficient strength of the porous layer can be easily obtained.
The content of the resin having a melting point lower than that of the polypropylene resin in the porous layer is preferably 5 to 30% by mass. Within this range, it is easy to draw a resin having a melting point lower than that of a polypropylene resin in a molten state, the fibrillar porous layer can be easily formed, and the abrasion resistance can be easily improved.

Among resins having a melting point lower than that of a polypropylene resin, polyethylene-based resins are preferable, and high-density polyethylene or low-density polyethylene is more preferable because they have stretching stability and easily form a fibril structure on the porous layer surface.
When a polypropylene resin and a polyethylene resin are used in combination, the content ratio of polypropylene resin to polyethylene resin in the porous layer (polypropylene resin: polyethylene resin) is 1: 2 to 1 from the viewpoint of achieving both excellent strength and abrasion resistance. It is preferably 2: 1.

(Inorganic filler)
As an inorganic filler which can be used for the porous layer, for example, heavy calcium carbonate, light calcium carbonate, calcined clay, talc, titanium oxide, barium sulfate, alumina, silica, zinc oxide, zeolite, mica, glass fiber, hollow glass beads, etc. Can be mentioned. Among them, heavy calcium carbonate, calcined clay, diatomaceous earth and the like are preferable because they are inexpensive and easily form many pores by stretching of a thermoplastic resin film, and adjustment of the porosity is easy. In particular, heavy calcium carbonate or light calcium carbonate is preferable because it is easy to adjust its average particle size or particle size distribution to a range in which pores are easily formed. Among the above-mentioned inorganic fillers, one kind can be used alone or two or more kinds can be used in combination.

The average particle diameter of the inorganic filler used in the porous layer is preferably 0.3 to 5 μm, and more preferably 0.5 to 2 μm, from the viewpoint of pore formation. If the average particle diameter of the inorganic filler is 0.3 μm or more, the porous layer is made porous, and the permeability of the aqueous pigment ink can be easily enhanced. If the average particle diameter of the inorganic filler is 5 μm or less, the formation of coarse pores is suppressed and the sharpness of the ink jet printed image can be easily enhanced.
The content of the inorganic filler in the porous layer is preferably 30 to 70% by mass, and preferably 40 to 68% by mass from the viewpoint of obtaining the above-mentioned permeability and water absorption to the aqueous pigment ink by making the porous layer porous. More preferably, 50 to 65% by mass is more preferable. When the content of the inorganic filler is 30% by mass or more, the permeability of the water-based pigment ink due to the formation of pores can be easily enhanced to improve the bleeding or the drying property. If the content of the inorganic filler is 70% by mass or less, stable stretch forming of the porous layer can be easily performed.

As described above, the inorganic filler in which the surface is coated with a cationic polymer is used as the inorganic filler in the porous layer, and the average particle diameter and the compounding amount of the inorganic filler to be used are specified ranges to make the porous layer porous. It is difficult for liquid with high surface tension like water to pass through (penetrate), and liquid with low surface tension like ink (organic solvent) tends to pass through (penetrate) in the porous layer and ink components that have penetrated further. A porous layer which can easily adsorb the anionic coloring material in the medium can be realized.

(Cationic polymer)
As described above, for the purpose of realizing a film having different penetrability depending on the adhering liquid and adsorbing an anionic coloring material, an inorganic filler having its outermost surface cationized is used as the inorganic filler. The cationic material that covers the surface of the inorganic filler is preferably a polymer-based material, that is, a cationic polymer. In the case of a polymer-based material, the cationic material does not easily penetrate to the surface of the porous layer after molding, and the second liquid does not permeate when left for 2 minutes after dropping the second liquid having a surface tension of 44 mN / m. , Is likely to express the permeability.

Examples of cationic polymers that are polymer materials include nitrogen-containing (meth) acrylic copolymers, ethyleneimine polymers, water-soluble polymers having a tertiary amine structure, a quaternary amine structure or a phosphonium salt structure, A vinyl polymer etc. which cationized water-soluble polymers, such as polyvinyl pyrrolidone and polyvinyl alcohol, by modification | denaturation, etc. are mentioned, These can be used individually or in combination of 2 or more types. Among them, a cationic polymer having a tertiary amine structure or a tertiary amine or higher tertiary amine structure having a quaternary amine structure is preferable. If it is a tertiary amine or higher higher amine structure, the surface of the inorganic filler is not simply hydrophilized, and the first liquid with a surface tension of 30 mN / m, which has a small amount of water absorption of 0.1 g / m ² or less, penetrates This makes it easy to develop a specific permeability, in which the second liquid with a surface tension of 44 mN / m does not penetrate.

(Anionic hydrophilic agent)
As an anionic hydrophilic agent, surfactant etc. which have a sulfo group, a carboxy group, etc. are mentioned, for example. Specific examples include surfactants having a sulfonic acid group described in JP-A-10-212367.

A commercial item can also be used as a surface-coated (surface-treated) inorganic filler with a cationic polymer or an anionic hydrophilic agent. As a commercial item, for example, AFE-Z, AFF-95, AFF-Z (manufactured by Fimatech Co., Ltd.) and the like can be mentioned.
The cationic polymer or the anionic hydrophilizing agent is preferably contained in the porous layer in a proportion of 1 to 2% by mass, and more preferably 1 to 1.5% by mass. The water absorption amount and the permeability of the porous layer can be adjusted by adjusting the content of the cationic polymer or the anionic hydrophilic agent.

The method of surface treatment is not particularly limited, and can be carried out, for example, by introducing an aqueous solution of a cationic polymer or an anionic hydrophilizing agent when wet-milling the raw material of the inorganic filler. This makes it possible to obtain a surface-treated inorganic filler, that is, an inorganic filler having a surface treatment layer containing a cationic polymer or an anionic hydrophilizing agent on the surface. In the case of combined use, surface treatment using a cationic polymer and surface treatment using an anionic hydrophilizing agent may be sequentially performed.

A water absorption of not more than 0.1 g / m ² , and a permeability to which the second liquid does not penetrate when the second liquid having a surface tension of 44 mN / m is dropped on the porous layer and left for 5 minutes; Preferably, the surface-treated inorganic filler in the porous layer located on the outermost surface opposite to the substrate layer exhibits cationicity. For that purpose, it is preferable to use only a cationic polymer having a relatively high molecular weight as a surface treatment agent, and to use a surface-treated inorganic filler without using an anionic hydrophilizing agent. Here, the molecular weight of the cationic polymer is preferably 20,000 to 200,000, and more preferably 30,000 to 100,000. When the molecular weight is at least the lower limit value of the range, the hydrophilicity of the surface decreases, and the second liquid tends to be difficult to penetrate. When the molecular weight is less than or equal to the upper limit value of the range, the inorganic filler surface-treated with the cationic polymer is less likely to aggregate, uniform voids are easily formed, and defects on the surface of the porous layer can be reduced.

(Dispersant)
The porous layer can contain a dispersant from the viewpoint of improving the dispersibility of the inorganic filler.
As a dispersing agent, an acid modified polyolefin, a silanol modified polyolefin etc. are mentioned, for example, A commercial item can also be used. Commercially available dispersants include Yumex 1001 (manufactured by Sanyo Chemical Industries, Ltd., maleic acid-modified polypropylene) and the like.

The content of the dispersant in the porous layer is preferably 0.01% by mass or more, and more preferably 1% by mass or more because sufficient dispersibility is easily obtained. In addition, the content of the dispersant is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less, because aggregation of the inorganic filler can be easily avoided.

The thickness of the porous layer (in the case of a porous layer having a multilayer structure, the total thickness of the individual porous layers combined) is 1 μm or more from the viewpoint of sufficiently securing a region through which the aqueous pigment ink penetrates. Preferably, it is 3 μm or more, more preferably 5 μm or more. The thickness of the porous layer is preferably 100 μm or less, more preferably 70 μm or less, and still more preferably 60 μm or less, from the viewpoint of preventing the thermoplastic resin film from becoming excessively thick.

When a plurality of porous layers are provided, the thickness of the porous layer located on the outermost surface may be 1 to 60% of the thickness of the whole of the plurality of porous layers because sufficient permeability is easily obtained. preferable. Among them, the lower limit is preferably 2% or more, more preferably 3% or more, and the upper limit is preferably 55% or less, more preferably 50% or less. The porous layer located on the outermost surface is a layer containing a cationic inorganic filler surface-treated with a cationic polymer, and the porous layer adjacent to the outermost surface is surface-treated with an anionic hydrophilizing agent In the case of a layer containing an anionic inorganic filler, the thickness of the layer located on the outermost surface is preferably 10% or less of the whole of the plurality of porous layers.

(Porosity)
The porosity of the porous layer is preferably 25 to 50% because this facilitates the adjustment of the ink absorption rate and the mechanical strength of the porous layer.
The porosity can be adjusted by the average particle diameter of the filler, the composition of the thermoplastic resin film containing the filler, for example, the ratio of the polypropylene resin and the polyethylene resin, and the stretching conditions such as the stretching temperature and the stretching ratio.

The method of measuring the porosity can be determined from the ratio of the area occupied by the pores in a given region of the cross section of the porous layer observed by an electron microscope. Specifically, an arbitrary part of the film to be measured is cut, embedded in epoxy resin and solidified, and then cut perpendicularly to the surface direction of the film to be measured using a microtome, and the cut surface is It is stuck on the observation sample stand so as to be the observation surface. Gold or gold-palladium etc. are vapor-deposited on the observation surface, and the pores of the porous layer are observed at an arbitrary magnification (for example, magnification of × 500 to × 3000) which is easy to observe with an electron microscope. Import as image data. The obtained image data is subjected to image processing by an image analysis device, and the area ratio (%) of the pore portion in a predetermined region of the porous layer is determined to be the porosity (%). In this case, it is possible to average the measurement values in any ten or more observations to obtain the porosity.

(Basis weight)
The basis weight of the porous layer, since the ink absorbing capacity is easily obtained, is preferably 3 g / ^{m 2} or more, more preferably 6 g / ^{m 2} or more, more preferably 8 g / ^{m 2} or more, 10 g / ^{m 2} The above is particularly preferable. Further, since the porous layer has lower mechanical strength than the base material layer, the basis weight is preferably 50 g / m ² or less, more preferably 40 g / m ² or less, and still more preferably 30 g / m ² or less.

The basis weight ratio between the porous layer containing an inorganic filler having a cationic property by surface treatment and the porous layer containing an inorganic filler having an anionic property by surface treatment is preferably 1:99 to 3: 1. , 2:99 to 1: 9 are more preferable. It is preferable for the basis weight ratio to be in this range because separation of the anionic colorant and the solvent component of the ink becomes easy.

When it has a plurality of porous layers, it is preferable that each porous layer which absorbs ink meets the above-mentioned basis weight conditions.
The said basis weight can be calculated | required from the density and thickness of a porous layer.
The basis weight of the porous layer may be adjusted by the thickness of the porous layer, the content of the inorganic filler, the average particle diameter, the stretching conditions of the thermoplastic resin film containing the inorganic filler, for example, the stretching temperature, the stretching ratio, etc. it can.

(Aperture ratio of surface)
The open area ratio of the surface of the porous layer is preferably 45 to 95%.
If it is in the said range, it will be easy to make an aqueous | water-based pigment ink permeate in a porous layer. Moreover, it is easy to fix a pigment in the void | hole of a porous layer, and it is easy to improve the abrasion resistance of a thermoplastic resin film.

(Average diameter of surface opening)
The average diameter of the openings of the porous layer is preferably 0.5 to 5 μm as the major axis and 0.1 to 1 μm as the minor axis.
If it is in the said range, it will be easy to make an aqueous | water-based pigment ink permeate in a porous layer. Moreover, it is easy to fix a pigment in the void | hole of a porous layer, and it is easy to improve the abrasion resistance of a thermoplastic resin film.
In a preferred embodiment of the present invention, when the porous layer is stretched, the melted cheese behaves as if it were stretched, and a fibrillar porous layer is obtained.

[Method of producing thermoplastic resin film]
The method for producing the thermoplastic resin film of the present invention is not particularly limited, and the thermoplastic resin film can be produced by an ordinary method. For example, after forming the thermoplastic resin film which comprises a base material layer, you may laminate | stack a porous layer. Examples of the film forming method include cast molding, calendar molding, rolling molding, inflation molding, etc., in which a molten resin is extruded into a sheet by a single-layer or multi-layer T die or I die connected to a screw extruder. Be In addition, film formation and lamination of the base layer and the porous layer are performed in parallel by using a general method such as a feed block, a multilayer die system using multi manifolds, and an extrusion lamination system using a plurality of dies. It can also be done.

The thermoplastic resin film of the base layer can be stretched before laminating the porous layer, or can be stretched after laminating. Since the porous layer is thin, it is preferable to stretch after laminating on the base material layer, not stretch forming in a single layer. Especially, since mechanical strength can be made high as a base material layer is a biaxial stretching layer, it is preferable. In addition, it is preferable that the porous layer is a uniaxially stretched layer, because a fibrillar surface can be easily formed and the abrasion resistance after pigment ink jet printing can be improved. It is further preferable that the base material layer is a biaxially stretched layer, and the porous layer is a uniaxially stretched layer.

As a stretching method, for example, a longitudinal stretching method using a circumferential speed difference of rolls, a transverse stretching method using a tenter oven, a sequential biaxial stretching method combining these, a rolling method, simultaneous two by a combination of a tenter oven and a pantograph An axial stretching method, a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor, and the like can be mentioned. Moreover, after extruding a molten resin into a tube shape using a circular die connected to a screw type extruder, a simultaneous biaxial stretching (inflation molding) method or the like in which air is blown into this can also be used.

When the thermoplastic resin to be used is an amorphous resin, the stretching temperature when carrying out the stretching is preferably in the range of the glass transition temperature or more of the thermoplastic resin. In addition, when the thermoplastic resin is a crystalline resin, the stretching temperature is not less than the glass transition point of the noncrystalline part of the thermoplastic resin and not more than the melting point of the crystalline part of the thermoplastic resin. Is preferred, and a temperature 2 to 60 ° C. lower than the melting point of the thermoplastic resin is preferred. Specifically, in the case of a propylene homopolymer (melting point 155 to 167 ° C.), a stretching temperature of 100 to 164 ° C. is preferable, and in the case of high density polyethylene (melting point 121 to 134 ° C.), a stretching temperature of 70 to 133 ° C. preferable.

The stretching speed is not particularly limited, but is preferably in the range of 20 to 350 m / min from the viewpoint of stable stretch forming.

Further, the draw ratio can also be appropriately determined in consideration of the characteristics and the like of the thermoplastic resin to be used. For example, when using a propylene homopolymer or a propylene copolymer, the lower limit is usually about 1.2 times or more, preferably 2 times or more, and the upper limit is 12 times in the case of drawing in one direction. Or less, preferably 10 times or less. On the other hand, in the case of biaxial stretching, the lower limit is usually 1.5 times or more, preferably 4 times or more, and the upper limit is 60 times or less, preferably 50 times or less. When the other thermoplastic resin film is stretched in one direction, the upper limit is usually 1.2 times or more, preferably 2 times or more, and the lower limit is 10 times or less, preferably 5 times or less. . When the biaxial stretching is performed, the lower limit is usually 1.5 times or more, preferably 4 times or more, and the upper limit is 20 times or less, preferably 12 times or less in area stretch ratio.
If it is in the range of the said draw ratio, the target porosity and basic weight will be easy to be obtained, and it will be easy to improve opacity. In addition, breakage of the thermoplastic resin film is less likely to occur, and there is a tendency that stable stretch molding can be performed.

[Thermoplastic resin film having a coat layer]
The thermoplastic resin film of the present invention may further have a coat layer containing a cationic polymer on the porous layer. That is, the thermoplastic resin film of the present invention having a coat layer has a base layer, a porous layer and a coat layer in this order. The thermoplastic resin film of the present invention having a coated layer is particularly useful as an inkjet paper.

FIG. 2 is a cross-sectional view showing the configuration of a thermoplastic resin film according to an embodiment of the present invention.
As shown in FIG. 2, the thermoplastic resin film 2 comprises a substrate layer A, two porous layers B1 and B2 on one surface of the substrate layer A, and a coat layer C on the porous layer B2. And.

(Coat layer)
The coat layer is a thin film covering all or part of the surface of the porous layer, and can maintain the water absorption and permeability of the porous layer described above. That is, the coat layer exhibits the same permeability as the porous layer, and when the first liquid having a surface tension of 30 mN / m is dropped on the coat layer and left for 5 minutes, the first liquid penetrates, and on the coat layer. When the second liquid having a surface tension of 44 mN / m is dropped and left for 5 minutes, the second liquid does not penetrate. The coat layer contains a cationic polymer and has a higher affinity to the ink than the porous layer, thereby facilitating the movement of the ink to the pores of the porous layer. Since the ink can be rapidly absorbed into the porous layer, the printability can be further improved.

(Cationic polymer)
As a cationic polymer which can be used for a coating layer, the fixing agent used for inkjet printing for common water-based dyes or water-based pigments can be used. An adhesion promoter contains the compound similar to the cationic polymer mentioned as a surface treatment agent of the said inorganic filler. The fixing agent may be used alone or in combination of two or more. Among them, from the viewpoint of enhancing the affinity to the aqueous pigment ink, a polymer containing a salt of a primary to tertiary amine or a quaternary ammonium salt as a cationic group is preferable. As such a polymer, a nitrogen-containing (meth) acrylic polymer or a cationic polymer having a quaternary ammonium salt structure obtained by quaternizing a nitrogen-containing (meth) acrylic copolymer with a cationizing agent, allylamine co-polymer Examples thereof include salts of polymers, salts of diallylamine copolymers, diallyldimethylammonium salts and the like. Here, the anion group of the salt is an acid residue, and examples of the organic acid include acetic acid, citric acid and lactic acid, and examples of the inorganic acid include hydrochloric acid, sulfuric acid and nitric acid. Among these, residues of inorganic acids are preferred, and chloride ions are particularly preferred.

The coating layer can be provided by applying a coating solution in which the cationic polymer is dissolved in water on the porous layer and drying it as necessary. By coating, a coating layer can be formed as a thin film which covers the surface of a porous layer. In the coating liquid, a water-soluble solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, ethyl acetate, toluene and xylene may be used as long as the function of the coating layer is not impaired. For coating, a coating apparatus such as a die coater, a roll coater, a gravure coater, a spray coater, a blade coater, a reverse coater, an air knife coater, or a size press coater may be used, or it may be immersed in a coating solution. It may be coated by

The coating amount of the coating layer is preferably 0.05 to 1.5 g / m ² in terms of solid content. When the coating amount is 0.05 g / m ² or more, the fixability of the aqueous pigment ink is easily expressed. In addition, when the coating amount is 1.5 g / m ² or less, the opening of the porous layer is less likely to be buried, and the abrasion resistance is likely to be improved.

In the coating layer, additives such as an antioxidant, an antiblocking agent, an antistatic agent, and a mildew proofing agent may be blended as long as the effects of the present invention are not impaired. The amount of the additive to be added to the coating layer is preferably 0.01 to 3% based on the weight of the coating layer.

[Inkjet Paper]
The inkjet paper of the present invention comprises the thermoplastic resin film of the present invention having the above-mentioned coating layer. The inkjet paper of the present invention may have a single layer structure of only the thermoplastic resin film of the present invention having a coat layer, or a multilayer structure, a thermoplastic resin film having the coat layer of the present invention at least at the outermost layer. May be used.

[Printing on Thermoplastic Resin Film and Inkjet Paper]
The thermoplastic resin film and the inkjet paper of the present invention have inkjet suitability, and can print various information such as photographs, figures, characters, and patterns on the porous layer or the coat layer by the inkjet method. For printing, various inkjet inks such as aqueous inkjet, solvent-based inkjet, and ultraviolet curable inkjet can be used. Among them, the thermoplastic resin film and the inkjet paper of the present invention are excellent in the printability with respect to the aqueous pigment ink, are less bleeding even at the time of multicolor printing, and can perform inkjet printing with high vividness and high sharpness. In addition to ink jet printing, it is possible to record using aqueous and oily sign pens, fluorescent markers, pencils and the like.

[Water-based pigment ink]
The aqueous pigment ink contains, for example, water, a pigment, a dispersant, a water-soluble organic solvent, a surfactant and the like.
The content of each component relative to the total mass (100% by mass) of the ink is usually about 0.2 to 10% by mass of pigment, about 1.5 to 15% by mass of dispersant, and 5 to 40 of water-soluble organic solvent The content of the surfactant is about 0.5 to 2% by mass.

EXAMPLES The present invention will be more specifically described below with reference to examples and comparative examples, but the present invention is not limited to the description of the following examples as long as the scope of the technical idea is not exceeded.
In addition, description of "part", "%", etc. in an Example means description by mass basis unless there is a notice.

Using the materials shown in Table 1 as the resin compositions used for producing the thermoplastic resin films of the following Examples and Comparative Examples, they are mixed at the compounding ratio (parts by mass) shown in Table 2 to obtain resin compositions a to I prepared h. The abbreviations in Table 2 are the same as the abbreviations described in Table 1.

Example 1
(Production of base material layer (longitudinal uniaxial stretched film))
Propylene homopolymer PP-2 (trade name: Novatec PP MA3H, manufactured by Nippon Polypropylene Corporation) 15 parts by mass, Propylene homopolymer PP-3 (trade name: Novatech PP FY6H, manufactured by Nippon Polypropylene Corporation) 59.5 parts by mass, High-density polyethylene PE-1 (trade name: Novatec HD HJ 590N, manufactured by Nippon Polyethylene Co., Ltd.) 9.5 parts by mass, Heavy calcium carbonate powder F-3 (trade name: Softon 1800, manufactured by Bihoku Powder Co., Ltd.) 16 parts by mass And 0.1 parts by mass of oleic acid D-3 (trade name: Lunak O-V, manufactured by Kao Corporation) as a dispersing agent, and mixed by stirring with a mixer to obtain a resin composition g.

The above resin composition g was melt-kneaded with an extruder set at 250 ° C., and then extruded into a sheet from a die and cooled to 70 ° C. with a cooling device to obtain a single layer non-oriented film. The unstretched film was reheated to 145 ° C., and then stretched 5 times in the machine direction using the circumferential speed difference between the rolls to obtain a longitudinally uniaxially stretched film.

(Production of porous layer (three-layer stretched film))
16 parts by mass of propylene homopolymer PP-1 (trade name: PM900C, manufactured by Sun Aroma Co., Ltd.), 20 parts by mass of high density polyethylene PE-1 (trade name: Novatek HD HJ 590N, manufactured by Nippon Polyethylene Co., Ltd.), surface-treated heavy calcium carbonate 62 parts by mass of powder F-1 (trade name: AFF-95, manufactured by Fimatech Co., Ltd.), 0.5 parts by mass of titanium dioxide powder F-5 (trade name: Typaque CR-60, manufactured by Ishihara Sangyo Co., Ltd.), and maleic acid A resin composition a was obtained by blending 2.0 parts by mass of modified polypropylene D-1 (trade name: MODIC P 908, manufactured by Mitsubishi Chemical Corporation) and stirring using a mixer.

Separately, 30 parts by mass of propylene homopolymer PP-2 (trade name: Novatec PP MA3H, manufactured by Nippon Polypropylene Corporation), 20 parts by mass of propylene homopolymer PP-3 (trade name: Novatech PP FY6H, manufactured by Nippon Polypropylene Corporation), High-density polyethylene PE-1 (trade name: Novatec HD HJ 590N, manufactured by Nippon Polyethylene Co., Ltd.) 4.5 parts by mass, Heavy calcium carbonate powder F-3 (trade name: Softon 1800, manufactured by Bihoku Powder Co., Ltd.) 45 parts by mass And 0.5 parts by mass of titanium dioxide powder F-5 (trade name: Typek CR-60, manufactured by Ishihara Sangyo Co., Ltd.), and mixed with stirring using a mixer to obtain a resin composition h.
The resin composition a and the resin composition h were melt-kneaded using two extruders set at 250 ° C., respectively, and then supplied to a co-extrusion die. Next, two types of resin compositions a and h are laminated in a co-extrusion die, which is extruded into a sheet, and a film derived from the resin composition h is in contact with the longitudinally uniaxially stretched film on one side of the longitudinally uniaxially stretched film. It laminated | stacked so that the film derived from the resin composition a might become an outer side, and obtained the laminated body of 3 layer structure.

The obtained laminate was reheated to 160 ° C. using an oven, and then stretched 9 times in the transverse direction using a tenter stretching machine. Subsequently, the film was heat-treated at 170 ° C. to obtain a stretched film having a three-layer structure of biaxially stretched layer / uniaxially stretched layer / uniaxially stretched layer, and used as the thermoplastic resin film of Example 1. In the thermoplastic resin film of Example 1, the biaxially stretched layer derived from the resin composition g is a base material layer, and each uniaxially stretched layer derived from the resin compositions h and a is a porous layer.
The thickness of the thermoplastic resin film of Example 1 was 80 μm. Among them, the thickness of the base material layer derived from the resin composition g was 58 μm, and the basis weight was 46 g / m ² . The thickness of the porous layer derived from the resin composition h was 10.2 μm, and the basis weight was 10.0 g / m ² . The thickness of the porous layer derived from the resin composition a was 11.8 μm, the basis weight was 10.0 g / m ² , and the water contact angle on the surface of the porous layer was 131 degrees.

Water contact angle
The contact angle of water on the surface of the porous layer of the thermoplastic resin film obtained in Example 1 was measured using an automatic contact angle meter (trade name: DM-301, manufactured by Kyowa Interface Science Co., Ltd.) according to JIS R 3257: 1999. It was measured under the conditions of temperature 23 ° C. and relative humidity 50% according to the method described. The measurement was performed three times, and the average value of each time was taken as the measurement value.

[Examples 2, 3 and Comparative Examples 1 to 4]
The resin composition a used as the outer layer of the porous layer in Example 1 was changed to the resin compositions b to f shown in Table 3 and the discharge amount of the extruder was changed to be shown in Table 3 The thermoplastic resin films of Examples 2 and 3 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1 except that the porous layer was obtained by changing the thickness and the basis weight. . Each thermoplastic resin film was a three-layer stretched film having a three-layer structure of biaxial stretching layer / uniaxial stretching layer / uniaxial stretching layer. In each thermoplastic resin film, the biaxially stretched layer is a base material layer, and each uniaxially stretched layer is a porous layer.

Example 4
The same operation as in the production of the base material layer (longitudinal uniaxial stretched film) of Example 1 was performed to obtain a longitudinally uniaxial stretched film.
Separately, the materials described in Table 1 were compounded at the compounding ratio described in Table 2 and stirred and mixed by a mixer to obtain a resin composition a, a resin composition d, and a resin composition h.
The resin composition a, the resin composition d, and the resin composition h were separately melt-kneaded using three extruders set at 250 ° C., respectively, and then supplied to a co-extrusion die. Next, three types of resin compositions a, d and h are laminated in a co-extrusion die, and this is extruded into a sheet, and a film derived from the resin composition h is longitudinally uniaxially stretched on one surface of the longitudinally uniaxially stretched film. It laminated | stacked so that the film derived from the resin composition a might be an outer side in contact with a film, and the laminated body of 4 layer structure was obtained.

The obtained laminate was reheated to 160 ° C. using an oven, and then stretched 9 times in the transverse direction using a tenter stretching machine. Heat-treated at 170 ° C. and composed of a laminate of resin composition g / resin composition h / resin composition d / resin composition a 4 of biaxially stretched layer / uniaxially stretched layer / monoaxially stretched layer / uniaxially stretched layer A layered stretched film was obtained to obtain the thermoplastic resin film of Example 4.
In the thermoplastic resin film of Example 4, the biaxially stretched layer derived from the resin composition g is a base material layer, and each uniaxially stretched layer derived from the resin compositions h, d and a is a porous layer.
The thickness of the thermoplastic resin film of Example 4 was 80 μm. Among them, the thickness of the porous layer derived from the resin composition h was 10.2 μm, and the basis weight was 10.0 g / m ² . The thickness of the porous layer derived from the resin composition d was 5.8 μm, and the basis weight was 5.1 g / m ² . The thickness of the porous layer derived from the resin composition a was 6.0 μm, and the basis weight was 5.0 g / m ² . The base layer had a thickness of 58 μm and a basis weight of 46 g / m ² , as in Example 1.

[Examples 5, 6]
The same operation as in Example 1 except that the discharge amount of the extruder is changed in Example 1 to change the outer layer of the porous layer made of the resin composition a to the thickness and basis weight shown in Table 3 Then, each thermoplastic resin film of Examples 5 and 6 was obtained.
The resin composition of the porous layer of the thermoplastic resin film obtained by each Example and a comparative example, thickness, and basis weight are shown in Table 3. Each base layer of each thermoplastic resin film had a thickness of 58 μm and a basis weight of 46 g / m ² as in Example 1.
Further, when the water contact angle was measured in Comparative Example 1 in the same manner as in Example 1, the water contact angle on the surface of the porous layer derived from the resin composition d of Comparative Example 1 was 98.4 degrees.

[Example 11]
On the surface of the thermoplastic resin film of Example 1 on the porous layer side, a cationic polymer diluted with water (trade name: Papiogen P-105, manufactured by Senka, polydimethyldiallyl ammonium chloride, trade name: Saftomar ST- 3200, a coating solution of a mixture of solid content ratio 1: 1 with a quaternized acrylic copolymer, manufactured by Mitsubishi Chemical Corporation, was applied. A # 4 mayer bar was used for coating. After coating, it was dried by a hot air drier at 105 ° C. to form a cationic polymer film, which was used as a coat layer to obtain a thermoplastic resin film having a coat layer. The coating amount of the cationic polymer was 0.13 g / m ² in terms of solid content, as calculated from the mass before drying and the concentration of the cationic polymer in the coating liquid.

[Examples 12 and 13]
Example 11 is the same as Example 11 except that the coating amount of the cationic polymer is increased by increasing the concentration of the cationic polymer in the coating liquid and changing the count of the meyer bar by a large count. The thermoplastic resin films of Examples 12 and 13 were obtained. The coating amount of the cationic polymer was 1.4 g / m ² in Example 12 and 1.6 g / m ² in Example 13 in terms of solid content.

The following evaluation was performed about the thermoplastic resin film of each Example and a comparative example.
[Water absorption]
The water absorption amount of the porous layer (uniaxially stretched layer) of the outermost surface of the thermoplastic resin film of each Example and each comparative example was measured. The amount of water absorption was determined by measuring the amount of water absorption after contact for 120 seconds using a Cobb size measuring device (manufactured by Kumagaya Riki Kogyo Co., Ltd.) according to the Cobb method (JIS P8140: 1998). The average value of data measured at three points was taken as the amount of water absorption.

[Permeability]
The thermoplastic resin films of the respective examples and comparative examples were allowed to stand in the form of a horizontal table with the porous layer side facing upward under an environment of a temperature of 23 ° C. and a relative humidity of 50%.
Next, using a commercially available mixture for wet tension test (Wako Pure Chemical Industries, Mixed fluid No. 30.0 for wet tension test) as a first liquid with a surface tension of 30 N / m, 20 μL of the same solution with a microsyringe It was dropped and dropped from 1 cm above the film. After leaving for 5 minutes, wipe the same solution from the surface after dropping with a tissue paper, approximate the outermost part of the spread of the mixed solution trace for wetting tension test with a circle, and if the diameter of the circle is 2 cm or more, the first liquid is It penetrated, and when less than 2 cm, it was judged that the first liquid did not permeate. In the thermoplastic resin films of Examples 11 to 13 having a coat layer on the porous layer, the first liquid was dropped from above the coat layer side.

Next, using a commercially available mixture for wetting tension test (mixture for wetting tension test No. 44.0, manufactured by Wako Pure Chemical Industries, Ltd.) as a second liquid having a surface tension of 44 N / m, It was made into droplets by a syringe and dropped from 1 cm above the film. After standing for 5 minutes, wipe the same solution from the surface after dropping with a tissue paper, approximate the outermost part of the spread of the mixed solution trace for wetting tension test with a circle, and if the diameter of the circle is 2 cm or more, the second liquid It penetrated, and when less than 2 cm, it was judged that the 2nd liquid did not penetrate. In the thermoplastic resin films of Examples 11 to 13 having the coat layer on the porous layer, the second liquid was dropped from the upper side of the coat layer side.

[Evaluation of suitability for inkjet printing]
On the porous layer side or the coated layer side of the thermoplastic resin film of each example and each comparative example, the pattern of N5 of JIS X 9201: 2001 (high-definition color digital standard image (CMYK / SCID)) is inkjet method I printed it. For printing, an aqueous pigment inkjet printer (type name: TM-C3500, manufactured by Seiko Epson Corporation) and an aqueous pigment ink of cyan, magenta, yellow, and black (model number: SJIC22) as the printer standard were used.

(Bleeding of ink)
The image printed by the inkjet printer was visually observed immediately after printing, and the dots of the image were observed with a stereomicroscope to determine bleeding as follows.
A (excellent): no bleeding is observed B (good): slight blurring is observed at the boundary of high concentration parts C (good): outline of the line becomes thick or unclear, and bleeding occurs in some places Can be seen D (not good): Bleeding can be seen in the entire image

(Ink drying ability)
The state of the ink on the printed image immediately after printing with the ink jet printer was visually observed, and tissue paper was pressed onto the printed image immediately after printing, and the drying property of the ink was determined as follows.
A (excellent): the ink is not visible as a liquid on the surface, and the ink does not transfer to the paper at all even if the paper is pressed lightly B (good): the ink is not visible as a liquid on the surface, but it is high when the paper is pressed Ink is transferred to paper in the image area of density C (OK): Ink is not visible as liquid on the surface, but when the paper is pressed, ink of the whole image is transferred to paper. D (Not possible): Ink is liquid on the surface Visible as

(Abrasion resistance)
The image portion printed by the inkjet printer using the thermoplastic resin film of each example and each comparative example is cut into a size of 30 mm × 120 mm one day after printing, and the Gakushin type dyeing friction fastness tester (trade name “ It was attached to a friction tester type II "(manufactured by Suga Test Instruments Co., Ltd.). The surface of the image portion printed with a weight of 215 g with a white cotton cloth (Golden No. 3) attached was friction-tested 100 times in accordance with JIS L 0849: 2004 (Dye fastness test method against friction), and resistance to dry conditions Abrasion evaluation was performed. Thereafter, the degree of peeling of the ink in the image portion was visually evaluated according to the following criteria.
Separately, in the above evaluation, the surface of the image portion printed with a weight of 215 g with a white cotton cloth (Golden No. 3) impregnated with 20 μL of pure water was subjected to a friction test for 100 times, and scratch resistance under wet conditions I did sex evaluation. Thereafter, the degree of peeling of the ink in the image portion was visually evaluated according to the following criteria.
A (excellent): 95% or more of the rubbed image portion remained B (good): 90% or more and less than 95% of the rubbed image portion C (Poor): 80% or more of the rubbed image portion, Less than 90% remained D (not good): The remaining rate of the rubbed image portion was less than 80%

The above evaluation results are summarized in Tables 3 and 4 below.

In each of Examples 1 to 6, the porous layer provided on at least one surface of the base layer has a water absorption of 0.1 g / m ² or less and the first liquid having a surface tension of 30 mN / m penetrates. In addition, the thermoplastic resin film has a permeability that the second liquid having a surface tension of 44 mN / m does not permeate. Above all, from the comparison of Example 1 and Example 2, the thermoplastic resin film having a porous layer containing an appropriate amount of polyethylene in the composition constituting the porous layer is suitable for inkjet printability (bleeding, ink drying property, And printing scratch resistance), but since the size of the pores is relatively large, the porosity is relatively large, and the surface of the porous layer easily forms a fibril structure, the ink It is thought that it is easy to penetrate

Example 4 has three porous layers on the substrate layer, and among the three layers, the porous layer containing an inorganic filler coated with a cationic polymer on the surface is located at the outermost layer, It can be seen that a porous layer containing an inorganic filler whose surface is coated with an anionic hydrophilizing agent is adjacent to the outermost layer, and exhibits good inkjet printability as in Example 1.
Further, from the comparison between Example 1 and Examples 5 and 6, it is understood that the larger the basis weight of the porous layer, the better the inkjet suitability.

On the other hand, in all of Comparative Examples 1 to 3, the outermost layer of the porous layer provided on at least one surface of the substrate layer is subjected to surface treatment with an anionic hydrophilic agent after surface treatment with a cationic polymer. Prior art thermoplastic resin film using an inorganic filler (inorganic filler whose surface is coated with an anionic hydrophilizing agent), but the amount of water absorption is large and both the first and second liquids permeate. It can be seen that such permeability does not provide excellent suitability for aqueous pigment ink jet printing.
Moreover, although the comparative example 4 is a thermoplastic resin film of the prior art which uses the inorganic filler which surface-treated by the higher fatty acid etc., neither a 1st liquid nor a 2nd liquid penetrates (what kind of liquid (Less permeable), excellent suitability for aqueous pigment ink jet printing was not obtained.

In each of Examples 11 to 13, by fixing the cationic polymer on the porous layer of the thermoplastic resin film and providing the coating layer, the fixability of the aqueous pigment ink is improved, and the bleeding and the ink drying property are improved. This is an example showing further improvement and being very suitable as an inkjet paper.
When Examples 11 to 13 are compared, it can be seen that the smaller the coating amount is, the higher the abrasion resistance is, and the coating amount has an appropriate range. This is presumed to be because the fibrillar structure on the surface of the porous layer is less likely to be buried by the cationic polymer if the cationic polymer to be the coating layer has an appropriate coating amount.

This application claims priority based on Japanese Patent Application No. 2017-210648, filed Oct. 31, 2017, and the entire contents of the Japanese Patent Application are incorporated.

The thermoplastic resin film and the inkjet paper of the present invention have low bleeding when using an aqueous pigment ink, and are excellent in ink drying property and abrasion resistance, so they are widely used as business cards, flyers, window films, POPs, posters, etc. It can be used to

1 Thermoplastic resin film 2 Thermoplastic resin film A Base layer B1, B2 Porous layer C Coat layer

Claims (5)

1. A substrate layer,
   A porous layer on at least one surface of the substrate layer,
   The water absorption amount per unit area of the porous layer is 0.1 g / m ² or less,
   When the first liquid having a surface tension of 30 mN / m is dropped onto the porous layer and left for 5 minutes, the first liquid penetrates, and the second surface having a surface tension of 44 mN / m is formed on the porous layer. When the liquid is dropped and left for 5 minutes, the second liquid does not permeate.
   Thermoplastic resin film characterized by
2. A substrate layer,
   A thermoplastic resin film having a porous layer on at least one surface of the substrate layer,
   The porous layer is a layer containing a thermoplastic resin and 30 to 70% by mass of an inorganic filler whose surface is coated with a cationic polymer,
   The average particle size of the inorganic filler is 0.3 to 5 μm,
   The thermoplastic resin film, wherein the water absorption amount per unit area of the porous layer is 0.1 g / m ² or less.
3. It is a thermoplastic resin film which has a substrate layer, a porous layer, and a coat layer in this order,
   The porous layer is a layer containing a thermoplastic resin and 30 to 70% by mass of an inorganic filler whose surface is coated with a cationic polymer,
   The average particle size of the inorganic filler is 0.3 to 5 μm,
   The thermoplastic resin film, wherein the coating layer contains a cationic polymer.
4. The porous layer is a multilayer,
   The outermost layer of the porous layer is a layer containing a thermoplastic resin and 30 to 70% by mass of an inorganic filler whose surface is coated with a cationic polymer,
   The layer adjacent to the outermost layer is a layer containing a thermoplastic resin and an inorganic filler whose surface is coated with an anionic hydrophilic agent.
   The thermoplastic resin film according to any one of claims 1 to 3, characterized in that
5. The inkjet paper containing the thermoplastic resin film of Claim 3 or 4.

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