JPH03215080A - Printing film - Google Patents

Abstract

PURPOSE:To improve the surface quality of a plastic film and thereby make it highly ink-receptive by providing an ink fixing layer consisting mainly of a colloidal silica complex emulsion with a specific glass transition point at least on one surface of plastic film. CONSTITUTION:A colloidal silica complex emulsion is a complex obtained by polymerizing a monomer having an ethylenic unsaturated bond in the pres ence of a colloidal silica using an emulsion polymerization. The glass transition point of the emulsion ranges from -30 to 20 deg.C. An ink-receptive layer consisting mainly of the colloidal silica complex emulsion is provided on the surface of film. Thus it is possible to obtain the film for offset printing which exhibits excellent receiving, scratch resistant and anti-blocking properties.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a printing film, and particularly to a printing film that can be printed well using a drying oil type ink.

``Conventional technology'' Conventionally, printing on plastic films has been carried out using gravure printing, flexo printing, screen printing, etc., taking advantage of the wide range of printing inks available and the ease of selecting inks that are compatible with the film. Offset printing is performed by taking advantage of the good drying properties of curable ink.

However, gravure printing, flexographic printing, and screen printing have drawbacks such as high plate-making costs, poor workability, and printed images that tend to have poor gradation and become unclear.

On the other hand, in the case of offset printing using ultraviolet curable ink, the plate making costs are low, printing is easy, and the printed matter has excellent gradation and clear images, which are the characteristics of offset printing. This requires expensive equipment such as an ultraviolet irradiation device, and especially in the case of simultaneous multicolor printing, a device must be installed for each color, and the ultraviolet curable ink used is affected by reaction initiators and residual monomers. There are also safety and environmental issues, such as the ink emitting a unique unpleasant odor even after drying. For this reason, there is a strong desire to be able to perform offset printing on the surface of a plastic film using a normal drying oil type ink in the same way as with general coated printing paper.

However, drying oil-type inks, which are prepared by adding colorants, resins, drying oils, and high-boiling petroleum solvents as main ingredients and additives such as wax compounds and dryers, have been used for printing on plastic films. In this case, there is little ink absorption as occurs when printing on paper, resulting in a pale print with a small amount of ink. Furthermore, since the setting of the ink is extremely slow, when printing on a sheet of film, stains are likely to occur due to ink set-off or bleeding. In recent years, plastic films suitable for offset printing using drying oil type inks have become commercially available, but all of these products have significantly inferior ink receptivity compared to paper. Prints printed on such films are inferior in density, color tone, and gradation compared to those printed on ordinary paper, and there is still room for improvement.

[Problems to be Solved by the Invention] In light of the above-mentioned circumstances, the present invention provides an offset printing film that has excellent ink receptivity and can produce high-density, clear printed matter by modifying the surface of a plastic film. It provides:

"Means for Solving the Problems" The present invention provides an ink fixing layer mainly composed of a colloidal silica composite emulsion having a glass transition point in the range of -30 to 20°C on at least one side of a Blasti-Siku film. This is a printing film that is characterized by:

``Operation'' An effective method for improving ink receptivity and imparting printability to a plastic film while maintaining its transparency is to provide a coating layer of latex with a low glass transition point on the film. The coated layer is extremely soft and easily damaged, and furthermore, there is a problem that blocking occurs easily when the coated layers are stored one on top of the other.

For this purpose, an inorganic pigment such as colloidal silica is usually added to this latex, but it is impossible to improve the scratch resistance and blocking resistance to the desired level by this means alone.

Therefore, the present inventors have improved scratch resistance, blocking resistance, etc.
As a result of intensive research to develop a plastic film for offset printing that satisfies the necessary conditions as a printing film and has excellent ink receptivity, we have developed an ink-receiving layer whose main component is a specific colloidal silica composite emulsion. The present inventors have discovered that an offset printing film with extremely excellent ink receptivity, scratch resistance, blocking resistance, etc. can be obtained by providing the above film on the surface of the film, and the present invention has finally been completed.

The colloidal silica composite emulsion used in the present invention is obtained by polymerizing a monomer having an ethylenically unsaturated bond (hereinafter referred to as an ethylenic monomer) in the presence of colloidal silica using a conventional emulsion polymerization method. For example, JP-A-59-71316, JP-A-6
The glass transition point of the emulsion as described in No. 0-127371 is in the range of -30 to 20°C.

Incidentally, those having a glass transition point of more than 20°C have insufficient improvement in ink receptivity, while those having a glass transition point of less than -30°C have problems in terms of anti-blocking suitability.

The colloidal silica used for preparing this composite emulsion usually has a primary particle size of 2 to 100 mμ. Examples of ethylenic monomers include (meth)acrylic acid esters having an alkyl group, aryl group, or allyl group having 1 to 18 carbon atoms, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, vinyl chloride, vinylidene chloride. , vinyl acetate, vinyl propionate, acrylamide, N-methylol acrylamide, ethylene, butadiene, and other materials known in the latex industry, if necessary, to further improve the compatibility between the colloidal silica and the organic polymer. Vinylsilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, T-methacrylooxyprobyltrimethoxysilane, etc. also stabilize the dispersion of emuldigon with (meth)acrylic acid, maleic acid, maleic anhydride, and fumaric acid. Anionic heptanomers such as , crotonic acid, etc. are used as auxiliaries. In addition, two or more types of ethylenic monomers can be used in combination if necessary.

Moreover, the ratio of ethylenic monomer/colloidal silica in emulsion polymerization is 100/1 to 200 in solid content ratio.

Among the colloidal silica composite emulsions used in the present invention, a more preferable one has a glass transition point of -
Examples include those in the range of 20 to 10°C. In addition, preferred compositions include those selected from acrylic esters or methacrylic esters as the ethylenic monomer, and particularly preferred ones include (meth)
Copolymers of acrylic acid ester and styrene, copolymers of (meth)acrylic acid alkyl ester and (meth)acrylic acid aralkyl ester, and copolymers of (meth)acrylic acid alkyl ester and (meth)acrylic acid aryl ester are listed. It will be done.

Incidentally, examples of emulsifiers used in emulsion polymerization include alkylaryl polyether sulfonic acid sodium salt, lauryl sulfonic acid sodium salt, alkylbenzene sulfonic acid sodium salt, polyoxyethylene nonylphenyl ether sulfate sorta salt, and alkylaryl sulfosuccinate sodium salt. Salt, sulfopropyl maleate monoalkyl ester sorter salt, etc. are exemplified.

Since the colloidal silica composite emulsion as described above has adhesive properties, the composite emulsion can be used alone or in combination of two or more types as a coating liquid for the ink fixing layer in the present invention. Furthermore, if necessary, other resin components may be used to adjust the hardness of the coating film to improve the balance of ink receptivity, scratch resistance, and anti-blocking suitability, or may affect the hardness of the coating film. Pigments are used to prevent films from adhering to each other and improve blocking resistance by forming fine irregularities on the surface of the film, and dispersants and additives are used to change the physical properties of coating liquids and coatings. Various auxiliary agents such as a sticky agent, an antifoaming agent, a coloring agent, a mold release agent, an antistatic agent, and a preservative are added as appropriate.

Examples of the above-mentioned resin components include conjugated diene polymer latex such as styrene-putadiene copolymer, methyl methacrylate-butadiene copolymer, acrylic ester such as acrylic acid ester and/or methacrylic acid ester polymer or copolymer, etc. latexes such as vinyl-based polymer latexes such as ethylene/vinyl acetate copolymers, and modified latexes obtained by modifying these various polymer latexes with functional group-containing monomers such as carboxyl groups; casein; Proteins such as soy protein and synthetic proteins; Starches such as positive starch and oxidized starch; Cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; Polyvinyl alcohol, olefin/maleic anhydride copolymer, melamine resin, epoxy resin, etc. Illustrated.

These resin components are usually blended in an amount of O to 50 parts by weight per 100 parts by weight of the solid content of the coating liquid for the ink fixing layer.

Examples of pigments include colloidal silica, clay, kaolin, aluminum hydroxide, calcium charcoal, titanium oxide, barium sulfate, zinc oxide, satin white,
Examples include calcium sulfate, talc, and plastic pigments. These pigments are usually blended in an amount of O to 50 parts by weight per 100 parts by weight of the solid content of the coating liquid for the ink fixing layer.

Examples of the plastic film used in the present invention include polyolefin films such as polyethylene, polypropylene, ethylene-brobylene copolymer, and polybutene-1, and transparent films such as PET, polystyrene, polyvinyl chloride, and nylon. PET and oriented polypropylene are preferred from the viewpoint of ease of processing.

Incidentally, the colloidal silica composite emulsion is effective as a means for improving the ink receptivity while maintaining the transparency of the film, and is also effective as a means for improving the ink receptivity of a pigment-internally added polyolefin film.

When using the above plastic film,
In order to further improve the ink fixability and the adhesion to the film, it is effective to perform surface activation treatment or anchor treatment by corona discharge treatment, flame treatment, ionizing radiation treatment, chemical treatment, etc.

Plastic films are electrically insulating and easily subject to frictional electrification, which can easily cause paper feeding problems during printing.Therefore, antistatic agents are usually added to the coating liquid for the ink fixing layer, and the ink fixing layer is Measures are taken such as coating the opposite surface with an antistatic coating liquid or incorporating an antistatic agent into the plastic film.

The coating liquid for the ink fixing layer is usually adjusted to a solid content concentration of 20 to 70% by weight, and is coated on untreated plastic film or surface-activated or anchor-treated plastic film using a gravure coater, roll coater, or bar coater. , air knife coater, curtain coater, etc., and then conventionally known and publicly used steam heating, hot air heating, gas heater heating, electric heater heating, infrared heater heating, high frequency heating, laser heating, and electron beam heating. It is dried by heating or other methods.

The ink fixing layer containing the colloidal silica composite emulsion of the present invention as a main component is provided on one or both sides of the plastic film, and the coating amount is usually about 0.3 to 20 g/rrf per side in terms of solid content. 2 to 10 g/r considering acceptability and coater productivity
A value of about yf is preferable.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

In addition, unless otherwise specified, "r part" and "%" in the examples indicate "part by weight" and "% by weight," respectively.

Example 1 A styrene-acrylic colloidal silica composite particle emulsion (product name: Movinyl 8000, Hoechst) with a glass transition point of 2°C was coated on one side of a transparent PET film (manufactured by Toyobo) with a thickness of 100μ and anchored. A transparent film for printing was prepared by coating the film with a roll coater to give a dry weight of 5 g/m.

Example 2 The same procedure was carried out, except that an acrylic colloidal silica composite particle emulsion (trade name: Movinyl 8020, manufactured by Hoechst Synthesis) with a glass transition point of -17°C was used instead of Movinyl 8000 used in Example 1. A transparent film for printing was prepared in the same manner as in Example 1.

Example 3 Carboxy-modified styrene-butadiene latex (trade name) was added to 80 parts of Movinyl 8020 used in Example 2.
A transparent film for printing was prepared in the same manner as in Example 1, except that 20 parts of emulsion (SN-307/manufactured by Sumitomo Naugatax ■) was used.

Example 4 Same as Example 1 except that a coating liquid was used in which 90 parts of Movinyl 8020 used in Example 2 was mixed with 10 parts of Colloidal Shiriyoku (trade name: Snowtex 0/manufactured by Nissan Chemical Industries, Ltd.). A transparent film for printing was created.

Example 5 Instead of Movinyl 8000 used in Example 1, a styrene-acrylic colloidal silica composite particle emulsion (trade name: Movinyl 8010, manufactured by Hoechst Synthesis ■) having a glass transition point of 19°C was used. is Example 1
A transparent film for printing was prepared in the same manner as above.

Example 6 A transparent film for printing was produced in the same manner as in Example 1, except that an acrylic colloidal silica composite particle emulsion with a glass transition point of -25°C was used instead of Movinyl 8000 used in Example 1. did.

Example 7 A transparent film for printing was produced in the same manner as in Example 1, except that a styrene-acrylic colloidal silica composite particle emulsion with a glass transition point of -15°C was used instead of Movinyl 8000 used in Example 1. It was created.

Comparative Example 1 Acrylic emulsion (product name: Movinyl 9000
Printing was carried out in the same manner as in Example 1, except that a coating liquid was used that was a mixture of 80 parts of Colloidal Silica (trade name: Snoté Nx O/manufactured by Nissan Chemical Industries, Ltd.) and 50 parts of colloidal silicone (trade name: Snoté Nx O/manufactured by Nissan Chemical Industries, Ltd.). A transparent film was created.

Comparative Example 2 Instead of Movinyl 8000 used in Example 1, an acrylic colloidal silica composite particle emulsion (trade name: Movinyl 8030) having a glass transition point of 22°C was used.
) A transparent film for printing was produced in the same manner as in Example 1 except that the following was used.

Comparative Example 3 A transparent film for printing was produced in the same manner as in Example 1, except that an acrylic colloidal silica composite particle emulsion with a glass transition point of -35°C was used instead of Movinyl 8000 used in Example 1. Created.

A total of 10 types of printing films of Examples 1 to 7 and Comparative Examples 1 to 3 thus obtained were cut to the required size,
After forming into a sheet-fed film, multicolor printing was performed on an offset printing machine using process ink, and the resulting printed matter was evaluated for printing, and the results are shown in Table 1.

The evaluation method and evaluation criteria are as follows.

[Ink receptivity] (abbreviated as A in Table 1) 3 hours after printing, rub the printed surface with the tip of your finger to check the degree of dryness of the printed area.

[Blocking resistance suitability] (abbreviated as B in Table 1) The front and back of the printed matter were stacked, and a load of 1kg/c+u” was applied to it for 50 minutes.
The degree of peeling of the front and back surfaces after being left for 72 hours at 90% RH was evaluated.

[Scratch Resistance] (abbreviated as C in Table 1) The hardness of the ink receiving layer was evaluated according to the paint film pencil hardness measuring method specified in JIS K 5400.

[Ink adhesion] (abbreviated as D in Table-1) 24 days after printing
After a period of time, a cellophane tape was attached to the printed area and peeled off vigorously to evaluate the degree of peeling of the printing ink.

Note that the evaluations of A, B, and D in Table 1 are as follows.

◎; Extremely good ○; Good Δ; Slightly inferior, but practical It had excellent ink receptivity, blocking resistance, and scratch resistance.

Claims (1)

[Claims] 1. A printing film comprising, on at least one side of a plastic film, an ink fixing layer whose main component is a colloidal silica composite emulsion having a glass transition point in the range of -30 to 20°C.