JPH03256785A - Transparent film for printing - Google Patents

Abstract

PURPOSE:To prevent printing running properties, ink receiving properties, blocking-resistant properties and transparency by adding synthetic hectorite clay to an ink fixing layer and/or a rear layer and setting a haze degree to a specific value or less. CONSTITUTION:Synthetic hectorite clay is added to an ink fixing layer and/or a rear layer. The transparency of a film generally lowers as a haze degree becomes high but, by setting the haze degree to 10% or less, since the printed pattern of the lowermost layer can be sharply seen through even when a plurality of printed transparent films subjected to printing processing are superposed one upon another, the characteristics of the transparent film are put to practical use. The ink fixing layer can be formed by applying an aqueous coating solution, a solvent type coating solution or a solventless coating solution to the single surface or both surfaces of a plastic film but it is pref. to use the aqueous coating solution from the aspect of safety and cost and, as the synthetic hectorite clay used in the ink fixing layer and/or the rear layer, there are 'Laponite(R)' RD, RDS, XLG, XLS or the like having the same structure as natural hectorite clay.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a transparent film for printing, and particularly to a transparent film for printing that has excellent printing runnability.

``Prior art'' Traditionally, printing on plastic films has been carried out by 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 excellent drying properties of UV-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.

In recent years, offset printing using drying oil type ink has been performed using a sheet of plastic film with an ink-receiving layer provided on the surface to improve the above-mentioned drawbacks of printing, but it is still insufficient in terms of performance. It has aspects that cannot be said to be true. For example, when performing offset printing on sheet plastic film, in addition to considering ink absorption and drying properties, it is also important to ensure that the stacked films are fed smoothly one by one to the printing machine, and are printed with good registration accuracy. They must also have excellent printing running properties, which means that they can be stacked in a perfectly aligned state.

However, plastic films have higher electrical insulation properties than paper, and therefore tend to cause sheets to stick to each other due to frictional electrification, and often have poor printing running properties. Generally, in order to improve this problem, a polymer containing a known organic conductive agent such as (1) quaternary ammonium salt or sodium sulfonate is coated on the surface. (2) Perform metal sputtering and vapor deposition. (3)
Methods such as incorporating an inorganic conductive agent such as tin oxide, indium oxide, or conductive zinc oxide during sheet manufacturing, or coating the sheet surface with a resin that serves as a binder are used, but method (1) The antistatic effect is not constant because the electrical resistance is highly dependent on humidity, and since the compound is hygroscopic, it tends to evaporate on the surface under high humidity. [
In method 2), it is technically difficult to control the thickness of the metal coating, and the manufacturing cost is high. Method (3) has its own problems, such as poor transparency and high cost.

In addition, for the purpose of improving antistatic properties, patent application No. 1-311
No. 435 describes a film coated with a composition consisting of synthetic hectorite clay, kaolin and an emuldigone adhesive. However, although this also provides a stable antistatic effect, the addition of kaolin reduces the transparency of the film, so when multiple sheets of printed transparent film are stacked, the printed pattern on the bottom layer cannot be clearly seen through. There are problems such as loss of quality.

``Problems to be Solved by the Invention J'' The present invention provides a transparent film for printing that does not have the above-mentioned drawbacks of conventional antistatic measures and has excellent printing runnability.

"Means for Solving the Problems" The present invention provides a transparent film for printing comprising an ink fixing layer mainly composed of a synthetic resin on one or both sides of a plastic film. This transparent film for printing is characterized in that it contains synthetic hectorite clay and has a haze degree of 10% or less.

"Function" The present inventors have found that the most effective method for imparting antistatic properties to plastic films without impairing their transparency is to incorporate synthetic hectorite clay into the ink fixing layer and/or its back layer. I found it.

In the present invention, the transparency of the film is expressed by the degree of haze,
Measured by the measurement method specified in JIS [6714]. Generally, as the degree of haze increases, the transparency of the film decreases, but by reducing the degree of haze to 10% or less, even if multiple sheets of printed transparent film are stacked, the printed pattern on the bottom layer can be clearly seen through the transparent film. The characteristics of

The ink fixing layer of the present invention can be applied and formed on one or both sides of a plastic film using an aqueous coating liquid, a solvent-based coating liquid, or a solvent-free coating liquid. A synthetic resin that is the main component of such an ink fixing layer is preferably a coating liquid based on styrene, for example.
Conjugated diene polymer latex such as butadiene copolymer, methyl methacrylate/butadiene copolymer, acrylic polymer latex such as polymer or copolymer of acrylic acid ester and/or methacrylic acid ester, ethylene/vinyl acetate copolymer Vinyl polymer latex such as polymer, or modified latex obtained by modifying these various polymer lattices/7x with a monomer containing a functional group such as a carboxyl group,
Acrylic ester-based or styrene-acrylic ester-based colloidal silica composite emulsions as described in JP-A-59-71316 and JP-A-60427371, polyvinyl alcohol, olefin/maleic anhydride copolymer, melamine resin, epoxy resin etc. are exemplified. Among these, colloidal silica composite emulsions with a good balance in ink receptivity and bronking resistance are preferred, and in particular, colloidal silica composite emulsions with a glass transition temperature of 130°C to 20°C are preferred.
Preferably, the range is .

The present invention includes not only a plastic film in which an ink fixing layer is provided on one or both sides, but also a plastic film in which an ink fixing layer is provided on one side and a back layer for antistatic purposes is provided on the opposite side. Like the ink fixing layer, this back layer is composed of a layer containing synthetic resin as a main component, and a synthetic resin having a higher glass transition point than that used for the ink fixing layer is usually selected from the above-mentioned synthetic resins.

The synthetic hectorite clay used for the ink fixing layer and/or its back layer has the same structural formula as natural hectorite clay, that is, the following formula: C(Sin(Mgs, :+4Lio, bb)Oz.

(OH, F) a) ) Laport displayed as M”., 66 (Note: almost all gates are Na”)
Laponite B manufactured by e Industries Ltd.
, S, or the following structural formula in which all the central layers are hydroxyl groups,
That is, ((Si8(Mgs, :+4Lio, bh')0□
. (OH) 4)) M”., 66 (Note: gate is always N
Laporte Industries displayed in
Ltd., Laponite RD, RDS, XLG, XLS
Tokaal.

The amount of synthetic hectorite clay to be mixed is appropriately adjusted depending on the type of plastic film, the composition of the layer, the type of synthetic resin used, etc., and is not particularly limited, but in general, The amount is about 0.1 to 50 parts by weight, more preferably about 1 to 20 parts by weight, based on 100 parts by weight of the solid content of the paint. In the above coating liquid, dispersants, thickeners,
Various auxiliary agents such as antifoaming agents, coloring agents, mold release agents, and preservatives are added as appropriate, and colloidal silica, aluminum hydroxide, talc,
Pigments such as plastic pigments are blended in an appropriate amount within a range that does not impair transparency.

The plastic film used in the present invention includes:
Examples include polyolefin films such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, and transparent films such as PET, polystyrene, polyvinyl chloride, and nylon. Oriented polypropylene is preferred.

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.

The coating liquid for the ink fixing layer or the coating liquid for the back layer is usually 2
Gravure coater, roll coater, bar coater, air knife coater, curtain coater on untreated plastic film, surface active treatment, or anchor treatment with solid content concentration adjusted to 0 to 70% by weight. It is coated using coating equipment such as
Next, conventionally known and publicly used steam heating, hot air heating, gas heater heating, electric heater heating, infrared heater heating,
Drying is performed using methods such as high frequency heating, laser heating, and electron beam heating.

The coating amount of the coating liquid for the ink fixing layer or back layer is usually about 0.3 to 20 g/m per side in terms of solid content, and 2 to 10 g/m considering ink receptivity and productivity by coater. degree is preferred.

"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, "parts" and "%" in the examples indicate "parts by weight" and "% by weight," respectively.

Example 1 100 parts of a styrene-acrylic colloidal silica composite particle emulsion (trade name: Movinyl 8000, manufactured by Hoechst Daisoku) was synthesized on one side of a 100 μm thick transparent PET film (manufactured by Toyobo Co., Ltd.) that had been subjected to anchor processing. Cutolite clay (trade name: Laponite B, Laporte
Industries Ltd., a coating liquid for ink fixing layer mixed with 50 parts of a dispersion slurry (solid content concentration 10%) was coated using a roll coater to give a dry weight of 5 g/rrf, and after drying, the back side was coated. An acrylic colloidal silica composite particle emulsion (
i (product name: Movinyl 8030, manufactured by Hoechst Synthetic Co., Ltd.) using a roll coater to give a dry weight of 5 g/m to prepare a transparent film for printing.

Example 2 Both sides were coated in the same manner as in Example 1, except that an acrylic colloidal silica composite particle emulsion (trade name: Movinyl 8020, manufactured by Hoechst Taisoko) was blended instead of Movinyl 8000 used in Example 1. A transparent film for printing was created.

Example 3 The same procedure as in Example 1 was carried out except that a styrene-acrylic colloidal silica composite particle emulsion (trade name: Movinyl 80 Ko0, manufactured by Hoechst Taisoko) was blended instead of Movinyl 8000 used in Example I. A transparent printing film coated on both sides was prepared.

Comparative Example 1 A transparent film for printing coated on both sides was prepared in the same manner as in Example 1 except that only Movinyl 8000 was used as the coating liquid for the ink fixing layer.

Comparative Example 2 Acrylic emulsion (product name: Movinyl 9000
, manufactured by Hoechst Synthesis ■) 100 parts of synthetic hectorite clay (trade name: Laponite B, Laporte In)
industries Ltd.) dispersion slurry (solid content concentration i.

%) 50 parts and kaolin (product name; UW-90, EMC
A transparent film for printing coated on both sides was prepared in the same manner as in Example 1, except that an ink fixing layer coating liquid containing 30 parts of a dispersion slurry (solid content concentration: 50%, manufactured by Co., Ltd.) was used.

Examples 1 to 3 and Comparative Examples 1 to 2 thus obtained
After cutting various kinds of transparent printing films to the required size and making them into sheet-fed films, multicolor printing was performed on an offset printing machine using process inks, and the results of printing evaluation of the obtained printed materials are shown in Table 1. It was shown to.

The evaluation method and evaluation criteria are as follows.

[Printing runnability] (abbreviated as A in Table 1) Two-sheet feeding, jamming, uneven loading area when printing continuously with a printing machine,
We evaluated the following disabilities.

[Ink receptivity] (abbreviated as B 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.

[Bronking resistance] (abbreviated as C in Table 1) The front and back of the printed matter are stacked and heated at 50°C under a load of 1kg/Ω2.
The degree of peeling of the front and back surfaces after being left for 72 hours under 190% RH conditions was evaluated.

[Transparency] (Abbreviated as D in Table 1) The haze (clouding; %) of the film before printing was measured using a haze meter (Model-TC-HIII/manufactured by Tokyo Heavy Shiki ■).

In addition, the evaluation judgment in A, B, and C of Table-1 is as follows.

◎; Very good ○; Good Δ; Slightly inferior, but practical was excellent in printing runnability, ink receptivity, blocking resistance, and transparency.

Claims (2)

[Claims] (1) In a transparent film for printing comprising an ink fixing layer mainly composed of a synthetic resin on one or both sides of a plastic film, the ink fixing layer and/or the back layer contains synthetic hectorite clay, and the haze degree is 10%
A transparent film for printing, characterized by the following: (2) The transparent film for printing according to claim (1), wherein the synthetic resin is a colloidal silica composite emulsion.