CS242794B1 - Peel-off film - Google Patents

Abstract

The invention provides a material for creating reproduction substrates on a transparent foil substrate. The retractable peel-off layer applied to this substrate is the only applied layer, the adhesion of which to the substrate is solved by using an appropriate ratio of true and false plasticizers of the film-forming binder. The foil is used in printing, cartography, electrical engineering, textile industry and wherever substrates for reproduction are created.

Description

The present invention relates to a retractable peel-off film used to produce auxiliary images and masks in the printing, cartography, electrical engineering, or even the textile and photo industries.

The retractable peel-off films usually consist of a backing formed by clear (transparent) films with suitable mechanical, optical and physicochemical properties, as well as auxiliary adhesive interlayers and the peel-off layers themselves stained with suitable dyes to filter the luminous flux used for copying. The backing is usually formed of films of polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyvinyl chloride or even cellulose triacetate and the like.

The auxiliary adhesive intermediate layer is typically formed by applying an adhesive layer of an elastomer, e.g., butadiene-styrene copolymer, polyvinyl ether, polyisobutylene, etc., or the intermediate layer is a polymer different from the polymer of the backing and the peeling layer. The adhesive interlayer may also be formed by a gelatin coacervate, especially for a gelatin withdrawable layer type (U.S. Patent No. 155,837).

The retractable peel layer is applied to a substrate provided with an auxiliary adhesive intermediate layer, typically in a thickness of 0.030 to 0.050 mm. It is usually intensely red, orange, or even green tinted to filter the light used when copying created masks or images. The peeling layer is usually based on gelatin, polyvinylpyrrolidone, polyvinyl alcohol or even chlorinated polyvinyl alcohol, PVC-PVAc copolymers, cellulose derivatives and the like.

The proper functioning of the peel layer provides considerable adhesion to the substrate and considerable internal cohesion of the peel layer when peeling the sites, and allows other operations such as fine, accurate and non-embossing cuts, correction agents and good dimensional stability in accordance with the substrate.

Not all peel layers meet all requirements. The layers do not exhibit good dimensional stability (usually depending on the relative humidity), they float on the surface of the carrier foil due to unsuitable adhesive layers, do not allow the application of correction varnishes, water the cut, tear during peeling, or even spontaneously detach from the substrate.

These disadvantages are overcome by the invention of a peel-off film without an auxiliary adhesive intermediate layer, the advantage being that the adhesion and cohesion of the layer is controlled by the ratios of true and false plasticizers, characterized in that the peel layer contains 30-90% of at least one nitrocellulose % of true emollients, preferably dibutyl phthalate, and 3 to 15% of false emollients, preferably castor oil, and the ratio of true emollients to nitrocellulose is from 1: 4 for low-adhesion layers to 8:10 for high-adhesion layers and the ratio of true and false plasticizers are from 2: 1 for low-adhesion layers to 4: 1 for high-adhesion layers.

The invention also relates to a retractable peel-off film, characterized in that the backing is a biaxially oriented high-transparency polyethylene terephthalate film or a polyester and polyolefin film with a transparency of greater than 60%. The retractable peel-off film is dyed in the peel-layer mass with light-fast dyes or pigments that are impermeable to actinic light or light of defined wavelengths.

The K-value given in the examples of the invention is a constant of the viscosity ratio according to CSN 64 0001.

The physical nature of the boundary adhesive active layer formed at the pad-peel layer is the diffusion and migration of a suitable ratio of true and false plasticizers, which for a given type of macromolecular substance used as the peel layer base is minimal at the optimum ratio and composition of true and false plasticizers. An advantage of the film according to the invention is that an optimal plasticizer ratio of 3: 1 has been found for nitrocellulose peel layers.

At the same time using several types of macromolecular substance differing only by the polymerization stage and several types of softening systems or even the percentage of true and false plasticizers, a relatively wide range of peel layer adhesives can be obtained. Macromolecular substances with a lower degree of polymerization (viscosity number) have the highest adhesion and conversely the highest intrinsic cohesion and relatively lower adhesion of a macromolecular substance with a high degree of polymerization (viscosity number).

Apply a single coat, dipping, spraying or rolling onto a backing of polyethylene, polypropylene, polyethylene terephthalate foil or for use in other fields as well as opaque backings (copper plates, etc.) with a uniform coating thickness of 0,030 up to 0.050 mm, optimally 0.040 nun. The film is dried either freely (discontinuous production method) or in a drying tunnel (continuous production) at elevated temperature depending on the type of substrate used. If, for example, polyethylene terephthalate foil is used as a substrate (used in cartography) with a thickness of 0.010 to 0.018 mm, the layers can be dried up to a temperature of 140 ° C. During drying, it is necessary to ensure a uniform (Gaussian) temperature distribution along the drying tunnel in order to avoid defects in the layer or winding of the still hot foil. At the end of the drying line, additional equipment (cooling equipment, anti-static coating equipment, etc.) is added.

He did

Material composition:

High viscosity nitrocellulose soluble in esters of

Κ = 1,440 15.5 g butyl acetate 5.2 g acetone 71.0 g polyvinyl ether 2.7 g dibutyl phthalate 5.1 g Victoria blau B 0.1 g Chrysoidin R 0.4 g

A homogeneous peeling layer is applied by dipping onto a 0.1 mm thick sheet of polyethylene terephthalate film and allowed to dry freely or at a slightly elevated temperature. The resulting green foil with a retractable peel layer is suitable for manual processing of images and masks, has high cohesion and acceptable adhesion to the substrate.

Example 2

Another example of a film having a withdrawable layer for manual processing.

Material composition:

High viscosity nitrocellulose soluble in esters of

1 = 1 440 8,5 g nitrocellulose, highly viscous, soluble in esters of a value

K = 950 8.5 g butyl acetate 7.2 g acetone 77.0 g castor oil 2.1 g dibutyl phthalate 6.3 g chrysoidin R 0.3 g

Rhodamine 0.1 g

A sheet of polyethylene foil of 0.15 mm thickness is topped with a corona charge and coated with a lacquer of the stated composition by pulling with a bar spatula. The draft must correspond to an optimum dry matter thickness of 0.040 mm. After surface drying, the film sheet is allowed to dry in the oven at a temperature of approx

Mp 100 ° C. After a quarter of an hour, the foil is usable for manual processing. The peel layer has high cohesion and moderate adhesion to the substrate.

Example3

Another example of a peel-off film intended for automated and manual creation of images or masks.

Material composition:

Highly viscous nitrocellulose soluble in esters of

K = 950 1450 g Low-viscose nitrocellulose soluble in esters of

K = 510 200 g butyl acetate 700 g acetone 6 500 g castor oil 350 g dibutyl phthalate 750 g

Orasolsoharlach 50 g

The coating of the peeling layer of this composition diluted to the required consistency (tumbler ČSN 0 6-18 s) is applied by dipping in a continuous dipping device at a constant speed of 0.4 m / min- ⁴ on the running polyethylene terephthalate film strip. The film must be passed through a drying tunnel with a maximum temperature of 130 ° C and, after drying, cooled through a roll of antistatic soap solution.

Claims (3)

SUBJECT OF THE INVENTION 1. A peel-off film, characterized in that the peel layer comprises 30 to 90% of at least one nitrocellulose in the dry state, 10 to 45% of true plasticizers, preferably dibutyl phthalate, and 3 to 15% of false plasticizers, preferably castor oil, and plasticizers to nitrocellulose are from 1: 4 for low-adhesion layers and up to 8:10 for high-adhesion layers, and the ratio of true and false plasticizers is from 2: 1 for low-adhesion layers and up to 4: 1 for high-adhesion layers. 2. A film according to claim 1, wherein the backing is a biaxially oriented polyethylene terephthalate film or a polyester and polyolefin film having a transparency of greater than 60%. 3. A film as claimed in claim 1, characterized in that it is colored in the peel layer by light-colored dyes or pigments which are impermeable to actinic light or light of defined wavelengths.