DE69008646T2 - Print strips. - Google Patents

Description

Background of the invention Field of invention

The present invention relates to an improved printing sheet having good ink adhesion properties, sheet running properties, anti-blocking properties, etc., and more particularly to an improved printing sheet having good adhesion properties when used with an ultraviolet-curable ink (hereinafter, "ultraviolet-curable ink" is referred to as "UV ink").

State of the art

In recent years, diversification of printed products requires printing on a wider variety of materials in sheet form, e.g., papers, synthetic papers, thermoplastic resin films, metal foils, metallized sheets, etc. These printed objects are printed by processes such as offset printing, gravure printing, flexographic printing, screen printing and letterpress printing. Among these printing processes, a process using a UV ink has recently become widely used because UV inks are rapidly cured and the printing process using a UV ink can be better managed. At present, there is a great demand for flat sheet-like objects.

In printing processes that use UV printing inks, the printing sheet must have the property that the cured UV printing ink adheres well to it. In addition, there are generally required properties such as sheet running properties, anti-blocking properties, the induction of a uniform distribution of the printing ink over the surface of the sheet and antistatic properties.

However, UV inks do not sufficiently adhere to the above sheet-formed materials, especially thermoplastic resin films, after printing and curing. Accordingly, the printed and cured UV ink has a problem that the printed and cured UV ink separates from the sheet-formed materials.

Therefore, a printing sheet to which the UV printing ink adheres better is required.

Summary of the invention

This invention takes into account the problems described above and therefore it is an object of this invention to provide a printing sheet, in particular a printing sheet made of a thermoplastic film, which has superior properties required of printing sheets and which in particular has better properties with regard to the adhesion of cured UV ink.

According to the invention, there is provided a printing sheet comprising a support body and a surface layer covering at least one side of the support body and comprising a copolymer consisting of an acrylic monomer having a carboxyl group and an acrylic monomer having an amino group or amide group.

In a further aspect, the present invention provides a printing sheet comprising a support body and a surface layer covering at least one side of the support body and comprising a copolymer or a homopolymer consisting of an acrylic monomer having an amino group or an amide group and a copolymer or a Homopolymer consisting of an acrylic monomer having a carboxyl group.

Description of preferred embodiments of the invention

In this invention, the term "acrylic monomer having an amino group or an amide group" means, for example, (meth)acrylamide and all kinds of (meth)acrylic esters containing amino groups such as a primary amino group (-NH2), a secondary amino group (-NH-), a tertiary amino group (N-), etc., specifically, 2-aminoethyl (meth)acrylate, 2-(methylamino)ethyl (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, 4-(dimethylamino)-n-butyl (meth)acrylate, acrylamide, N-methylolacrylamide, N-ethylolacrylamide, diacetoneacrylamide, etc. are given, but are not limited to these. The term "an acrylic monomer having a carboxyl group" means chemicals such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc., but is not limited to them. In these monomers, as "acrylic monomer having an amino group or an amide group", 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate and N-alkylolacrylamide are preferred, and as "acrylic monomer having a carboxyl group", acrylic acid and methacrylic acid are preferred.

In this invention, the term "a surface layer" means a layer covering at least one side of the support body described below. This surface layer contains the above copolymer or homopolymer having the above acrylic monomer and a composition described below. The copolymer having the above acrylic monomer having a carboxyl group and the above acrylic monomer having an amino group or an amide group refers to copolymers consisting of the above two components or copolymers consisting of not less than one kind of monomer capable of polymerizing with the above copolymers in addition to the above two components. In this case, "a monomer capable of polymerizing" means, for example, a (meth)acrylic monomer, styrene monomer, etc., with n-butyl (meth)acrylate being particularly preferred.

The ratio of the composition of the above acrylic monomer in the surface layer is the ratio of "acrylic monomer having an amino group or amide group" / "acrylic monomer having a carboxyl group", which is between 8/2 to 2/8 inclusive (molar ratio), and preferably between 6/4 to 4/6 inclusive. The weight ratio of the above acrylic monomers in the surface layer is over 1%, preferably between 5 to 40%. The thickness of the surface layer is preferred to be 1 to 10 µm.

In this invention, the surface layer is formed on the supporting body by applying a paint which is prepared in which the above compound is dissolved or dispersed in a solvent, water, etc. with a binder resin, if necessary. This paint is applied to the supporting body by the method of roll coating, blade coating, spray coating, air knife coating, bar coating, etc. and then dried. As another method of forming the surface layer, a compound of the above material for forming the surface layer is uniformly mixed and used to form the surface layer on the supporting body by the method of hot melt coating or by laminating. In this case, as the binder resin, the resin which is generally used for coating and laminating is used. All kinds of copolymers or homopolymers can be used, e.g. polyester resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, etc.

The surface layer may, if necessary, contain any other additional agents for preventing blocking of one sheet to another and for improving sheet running properties, antistatic properties, non-transparency properties, etc. As the above additive agent, for example, a pigment such as polyethylene oxide, silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, synthetic zeolite, aluminum oxide, zinc oxide, titanium oxide, lithopone, satin white, etc., and cationic, anionic and non-ionic antistatic agents, etc. may be used.

As the support body that can be used in this invention, a thermoplastic resin sheet, paper, synthetic paper, woven fabric, nonwoven fabric, ceramic sheet, metal fiber sheet, metallized sheet (film), metal foil, metal plate, etc., and a composite sheet formed by the combination of the above materials bonded together into a multilayer structure are preferred. If a printing machine can be changed over, the shape of the support body is not limited to, for example, a film, sheet, plate, etc.

In this invention, the printing sheet to which cured UV ink adheres particularly well comprises a surface layer comprising the copolymer polymerized n-butyl methacrylate and the "acrylic monomer having an amino group or an amide group" in which at least one kind is selected from the group consisting of 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate and N-alkylolacrylamide, and the "acrylic monomer having a carboxyl group" which is selected from acrylic acid and methacrylic acid. This surface layer covers the support body.

In this printing sheet, an opposite side of the carrier body, namely a side not covered by the surface layer, can be provided with a pressure-sensitive Adhesive layer (contact adhesive layer) consisting of a commonly used pressure-sensitive adhesive. Further, if necessary, a release film or sheet consisting of a release agent may cover the pressure-sensitive adhesive layer. This printing sheet can be used for an adhesive label which can be attached to various kinds of surfaces. Accordingly, this printing sheet can expand the applications of the printing sheet of this invention.

EXAMPLES

The following examples further illustrate preferred operations within the scope of the present invention. "Parts" as used in the present invention means parts by weight.

Example 1:

A polyethylene terephthalate film having a thickness of 100 µm (sold by Fuji Film Company under the name of PET100G) was used, and on one side of this film, a surface layer was formed by applying a paint containing the following ingredients and drying the surface layer. This surface layer had a thickness of 3 µm.

The following are components of the above paint:

- 10 parts 2-(dimethylamino)ethyl methacrylate / acrylic acid / methyl methacrylate / n-butyl methacrylate (2:2:2:4) copolymer;

The molecular weight is in the range of 100,000;

the non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

Example 2:

The same procedure as described for Example 1 was repeated, with the exception that the components of the paint were as follows:

The following are the components of the above paint:

- 10 parts 2-(dimethylamine)ethyl methacrylate / acrylic acid / methyl methacrylate / n-butyl methacrylate (1:1:2:6) copolymer;

The molecular weight is in the range of 100,000;

the non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

Example 3:

The same procedure as described for Example 1 was repeated, with the exception that the components of the paint were as follows:

The following are the components of the above paint:

- 10 parts 2-(diethylamino)ethyl methacrylate / methacrylic acid / methyl methacrylate / n-butyl methacrylate (0.5:0.5:3:6) copolymer;

The molecular weight is in the range of 100,000;

the non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

Example 4:

The same procedure as described for Example was repeated, with the exception that the components of the paint were as indicated below.

The following are the components of the above paint:

- 5 parts 2-(diethylamino)ethyl methacrylate / n-butyl methacrylate (2:8) copolymer;

The molecular weight is in the range of 50,000;

the non-volatile material accounts for 40%.

- 5 parts acrylic acid / n-butyl methacrylate (2:8) copolymer;

The molecular weight is in the range of 50,000;

The non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

Example 5:

The same procedure as described for Example 1 was repeated, except that the components of the paint were as indicated below.

The following are the components of the above paint:

- 10 parts acrylamide / acrylic acid / methyl methacrylate / n-butyl methacrylate (1:1:2:6) copolymer;

The molecular weight is in the range of 100,000;

the non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

Example 6:

The same procedure as described for Example 1 was repeated, with the exception that the components of the paint were as indicated below.

The following are the components of the above paint:

- 10 parts N-methylolacrylamide / acrylic acid / methyl methacrylate / n-butyl methacrylate (1:1:2:6) copolymer;

The molecular weight is in the range of 100,000;

the non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

Comparison example 1:

The same procedure as described for Example 1 was repeated, with the exception that the components of the paint were as indicated below.

The following are the components of the above paint:

- 20 parts methyl methacrylate resin (sold by Soken Kagaku Company under the name M-2000);

the non-volatile material makes up 10%.

- 5 parts toluene

- 5 parts methyl ethyl ketone.

Comparison example 2:

The same procedure as described for Example 1 was repeated, with the exception that the components of the paint were as follows:

The following are the components of the above paint:

- 10 parts 2-(diethylamino)ethyl methacrylate / n-butyl methacrylate (2:8) copolymer;

The molecular weight is in the range of 50,000;

the non-volatile material is 40%.

8 parts toluene

2 parts methyl ethyl ketone.

Comparison example 3:

The same procedure as described for Example 1 was repeated, with the exception that the components of the paint were as indicated below.

The following are the components of the above paint:

- 10 parts acrylic acid / n-butyl methacrylate (2:8) copolymer;

The molecular weight is in the range of 50,000;

the non-volatile material accounts for 40%.

- 8 parts toluene

- 2 parts methyl ethyl ketone.

The printing sheets obtained by the above procedure (Examples 1 to 6 and Comparative Examples 1 to 3) were evaluated for ink adhesion properties and reproducibility. In the evaluation procedure, a UV ink (marketed by Toyo Ink Mfg. Co., Ltd. under the name Flash Dry, dark blue) was printed on these sheets, then cured by three UV lamps (5.6 kw) at a distance of 14 cm between the lamps and the sheets for 3 seconds. These printing sheets were evaluated by the I.G.T. Printability Tester (manufactured by Kumagaya Riki Co., Ltd.).

The results obtained are shown in the following Table 1. Table 1 Reproducibility Adhesion Example Comparative example

In Table 1, "Reproducibility" means the even spread of the ink over the surface of the sheets, and "Adhesion" indicates how well the ink adhered to the sheets. In Table 1, "Reproducibility" was evaluated by visual inspection; and means a desirable thickness and X means an unsatisfactory thickness.

In Table 1, the adhesive properties were evaluated by using an adhesive tape. This adhesive tape was applied to the above printed sheets with a dried UV printing ink on its surface and then the adhesive tape was quickly peeled off. In this way, the properties of the ink printed on the sheet are determined. indicates that the ink did not peel off from the sheet; indicates that part of the ink peeled off from the sheet; Δ indicates that the ink peeled off from the sheet to a considerable extent, but that the printed letters, etc. were still legible; X indicates that the ink peeled off from the sheet to a considerable extent and accordingly the remaining remnants of the printed letters, etc. were no longer legible.

Then, the printing sheets obtained by the above operations (Examples 1 - 6) were subjected to actual printing conditions. In this practical test, an offset printing machine (HEIDELBERG MO) was used and 10,000 sheets of the above printing sheet were printed. As a result, the above printing sheets exhibited very desirable properties in terms of adhesion of the printing ink to the above sheets, reproducibility, etc.

Claims (3)

1. A printing sheet comprising a support body and a surface layer, the layer covering at least one side of the support body and comprising a copolymer, wherein the copolymer comprises two kinds of acrylic monomers: one kind of monomers having carboxyl groups and the other kind of monomers selected from the group having amino groups and amide groups. 2. A printing sheet comprising a support body and a surface layer, the layer covering at least one side of the support body and comprising two kinds of polymers: one kind of the polymers selected from a copolymer and a homopolymer having acrylic monomers selected from the group consisting of amino groups and amide groups, and the other kind of the polymers selected from a copolymer and a homopolymer having a carboxyl group. 3. Printing sheet according to claims 1 and 2, wherein the acrylic monomer selected from the group consisting of amino groups and amide groups is 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate and N-alkylolacrylamide.