EP0087688B1 - Drawing sheet - Google Patents

Abstract

Disclosed is a drafting film which comprises a plastic base provided on at least one surface with an adhesive layer and a pigmented coating system which comprises a pigmented layer and a top layer or a pigmented layer alone. In particular, the pigmented coating system comprises an acrylate or methacrylate copolymer comprising at least 50 percent by weight of an ester monomer, the alcohol component of which has a chain length of at least four carbon atoms, an antistatic agent comprising a polymeric sulfonic acid salt in combination with homopolymers or copolymers of vinyl acetate, or partially hydrolyzed polyvinyl acetate, cross-linking agents and delusterants. Also disclosed is the use of the drafting film for producing diazo sensitized film.

Description

The present invention relates to a drawing film made of a plastic carrier which is provided at least on one surface with an adhesive layer and a pigment coating system which consists of polyvinyl acetate or a copolymer of vinyl acetate and an unsaturated carboxylic acid or a partially hydrolyzed polyvinyl acetate, hydrophobicizing and matting agents and possibly crosslinking compounds .

A drawing film is usually made from a plastic film made of cellulose acetate, polyvinyl chloride, polypropylene, preferably from polyethylene terephthalate, which is provided with an adhesive layer on at least one surface. They are coated with a pigment coating system so that a surface that can be written on or written on with pencil leads and ink is created. The pigment lacquer system is designed so that a pigment lacquer layer is formed on its surface, on which also lines of water-based drawing ink adhere, or in such a way that a separate top layer is applied to the pigment lacquer layer in order to achieve ink adhesion.

A film material which can be written on is known (DE-OS 2417879) which, on a pigment lacquer layer, contains a top layer which consists of a homopolymer of vinyl acetate, a polymeric compound which mainly contains monomers containing hydroxyl or carboxyl groups, and consists of a hydrophobizing agent. In principle, such a top layer has proven to be sensitive to water and moisture. With a large proportion of water repellents, the wetting of water-based ink is also unsatisfactory. Finally, this film material lacks an antistatic finish.

There is also known a cover layer for a matt, label-accepting film material (DE-OS 2347324) which contains an outer layer as an antistatic coating on a polyester support which is provided with a layer of film-forming cellulose lacquer on at least one surface. Antistatic agents are water-soluble, relatively complicated compounds of sulfonated polystyrene and a cycloaliphatic amine salt of an alcohol sulfate, in which at least one alicyclic radical having at least five carbon atoms is connected to the amine nitrogen atom, the alcohol radical of the alcohol sulfate contains at least five carbon atoms and the compound in total has at least twelve carbon atoms includes, used. A disadvantage of such a layer is that it is sensitive to atmospheric moisture and can be removed from the surface at any time with water.

A matt film material is also known (DE-OS 2 342 601) which accepts ink or ink characters, which contains at least on one surface a first coating of a matt, film-forming cellulose lacquer composition and is provided with a second coating, which consists of an alkyl monoester the poly (alkyl vinyl ether maleic acid) exists. Such a coating must be applied from a solution containing organic solvent. In addition, the cover layers are relatively thick, so that they tend to stick slightly at elevated temperatures. There is no antistatic equipment whatsoever.

There is also a transparent drawing material with a carrier made of polyester film and a drawing layer known (DE-PS 1 621 988 corresponding to GB-PS 1 231 407), the silica and / or aluminum silicate as a pigment and as a binder a hardened mixture of polyvinyl alcohol, a urea - or melamine-formaldehyde precondensate and an acrylic acid ester copolymer. Although such a material maintains a good ink line width, it has an unsatisfactory ink setting and is also not antistatic, so that the material does not meet the highest demands.

Finally, a printable and ink-writable polyester film is known (GB-PS 1 500 134) with a very thin layer of polyvinyl alcohol or up to 72 mole percent hydrolyzed polyvinyl acetate and a second component, which is a wax, applied during the production of the film or a homo- or copolymer of acrylic or methacrylic acid or its esters or a homo- or copolymer of vinyl acetate. Such a film is not a drawing film, which can usually also be labeled with a pencil, and which must have a significantly greater application weight for the purpose of correcting lines. When applying such a layer in the character layer thickness, however, layers are obtained which are highly sensitive to moisture and heat and which are not technically usable. In addition, the known layer lacks the antistatic finish.

A coated plastic film such as polyester film is also known (DE-OS 2 513 422), which is optionally provided on a substrate layer made of acrylic or methacrylic acid copolymer with a layer which consists of a non-hydrolyzed or partially hydrolyzed polymer or copolymer of vinyl acetate and a resinous component suitable for intramolecular crosslinking. The copolymer of vinyl acetate has 50 or more mole percent vinyl acetate and can contain as a comonomer a wide variety of compounds such as dialkyl maleate, 2-ethylhexyl acrylate, ethylene, vinyl chloride or a vinyl ester of versatic acid. Such a coated film, it is stated, should also be suitable for the production of drawing films if appropriate additives such as particulate materials or fillers, dyes, pigments and / or antistatic agents are incorporated into it. However, a composition in this regard is not specified.

Due to the installation of finely divided matting agents, a certain writability with pencil leads can be expected, additives are more suitable Type for ink or ink lettering, however, require considerable experimental effort with regard to compatibility and coordination of the substances with one another and with regard to required properties such as wettability of the inks on the surface in a suitable manner, adhesion on the surface and correctability of the characters, etc. This only applies especially with the eventual addition of antistatic agents, which experience has shown that they can be written on with ink, which can go so far that they no longer wet.

It was therefore an object of the present invention to provide a high-resistance drawing film which can be written on with pencil and aqueous ink or ink and which avoids the disadvantages described, on which lines of ink or ink are sharp and full-coverage and on which the lettering also coincides Target line widths submitted to tube springs are observed. Corrections on the surface should be possible without leaving ghost images and the adhesion of the layers as well as the adhesion of the applied signs should meet high demands. It was also an object of the invention to provide the drawing sheet with an antistatic finish, without the wetting ability of the inks being impaired and without adversely affecting the necessary resistance of the drawing sheet to moisture, mechanical attack and elevated temperature.

In the case of a drawing material of the type mentioned at the outset, the object is achieved in that the pigment coating system contains, as a hydrophobizing agent, a copolymer which consists of at least 50% by weight of an acrylic or methacrylic acid ester monomer, the alcohol component of which has a chain length of at least four carbon atoms, and no vinyl acetate contains as a comonomer, and that an antistatic from the series of salts of polymeric sulfonic acids is present in the pigment coating system.

The pigment coating system preferably contains an acrylic or methacrylic ester interpolymer which is formed at least 75 percent by weight from an acrylic or methacrylic ester monomer, the alcohol component of which has a chain length of at least four carbon atoms and an antistatic from the series of the sodium salts of polymeric sulfonic acids.

It has proven to be advantageous if the pigment coating system contains an acrylic or methacrylic ester interpolymer which is formed at least 50% by weight from an acrylic or methacrylic acid ester monomer, the alcohol component of which has a chain length of four carbon atoms.

Also particularly suitable is an acrylic or methacrylic ester interpolymer which is formed at least 75 percent by weight from an acrylic or methacrylic ester monomer whose alcohol component has a chain length of eight carbon atoms.

This ensures that, according to the invention, a drawing film can be made available that meets the highest demands. The bond between the dimensionally stable plastic film and the pigment coating system is excellent. The writability with graphite or plastic leads and their correctability are good. The mechanical strength, the thermal resistance and the resistance to moisture or water influence meet the requirements for a good drawing film. The writability with water-based drawing inks is so good that the lines fully cover, i.e. H. inking is satisfactory; the lines are sharp. The dashed line width corresponds to the specified width when labeled with tube nibs. Furthermore, the ink lines are easy to correct and there are no ghost images. The drawing surface does not charge when it is handled, i.e. H. Formats can be easily unstacked. Eraser remains do not stick and the dust attraction is significantly reduced.

Plastic carriers are those made of polyvinyl chloride, polycarbonate, polystyrene, polysulfone, polyolefin or of polyester or cellulose ester. Because of the excellent dimensional stability, which is of particular importance, films based on polyester, such as polyethylene terephthalate, are preferably used.

Known mixtures are used as adhesive layers, which are described, for example, in DE-PS 1228414, corresponding to GB-PS 1061784, and consist of a mixture of the aqueous solution of a halocarboxylic acid, finely divided silicon dioxide and wetting agent, or also of mixtures which consist of DE- AS 1 629480, according to GB-PS 1 127 076, emerge. Polyvinylidene chloride copolymers of aqueous dispersion are applied between stretching in the longitudinal and transverse directions.

The pigment coating system according to the invention consists either of a pigment coating layer and a top layer, which is preferred, or of a pigment coating layer alone.

A pigment lacquer system consisting of a pigment lacquer layer and top layer consists of a pigment lacquer layer of a known type and the top layer consists of a copolymer of vinyl acetate and an unsaturated carboxylic acid, of a copolymer which consists of at least 50% by weight of an acrylic or methacrylic ester monomer, the alcohol component of which has a chain length of at least has four carbon atoms and contains no vinyl acetate as a comonomer, and from an antistatic from the series of the salts of polymeric sulfonic acids.

In the case of the preferred embodiment in the form of a pigment lacquer layer and top layer, the top layer contains a copolymer of at least 90 percent by weight vinyl acetate and at most 10 percent by weight of unsaturated carboxylic acid and the combination of acrylic or methacrylic ester mixed polymer, which is formed at least 75 percent by weight from an acrylic or methacrylic ester monomer, the alcohol component of which has a chain length of at least four carbon atoms, and an antistatic from the series of sodium salts of polymeric sulfonic acids, while the pigment coating layer corresponds to a recipe known, for example, from DE-OS 2 417 879.

If the pigment coating system forms only one layer, then the pigment coating layer known from DE-PS 1 621 988, for example, incorporates the components of the combination according to the invention.

A copolymer of at least 90 percent by weight vinyl acetate and at most 10 percent by weight unsaturated carboxylic acids serves as comonomers for the vinyl acetate, for example acids such as maleic acid or maleic anhydride, citraconic acid, itaconic acid or also crotonic acid. Copolymers containing 95 percent by weight vinyl acetate are preferably used.

A product is used as the partially hydrolyzed polyvinyl acetate, which ensures a good combination of water insolubility and hydrophilicity during crosslinking. Polyvinyl acetates with a residual acetyl content of up to about 20 percent by weight are suitable for this, which corresponds to a hydrolyzed fraction of up to about 75 mole percent.

The inventive acrylic or methacrylic acid ester copolymers used are copolymers which are formed from at least 50, preferably 75 percent by weight or more from an ester monomer, the alcohol components of which have a chain length of at least four carbon atoms and contain no vinyl acetate as comonomer. Alcohol components of four and eight carbon atoms have proven particularly useful here. If the alcohol component has four carbon atoms, it was recognized that, as an additional requirement, the copolymer dispersion must lead to films which are not hydrophilic. In the case of the alcohol component with eight carbon atoms, substances that are normally used for permanently elastic adhesives have surprisingly proven themselves, for example copolymers with a large proportion of 2-ethylhexyl acrylate. The copolymers according to the invention have glass transition points in the range between 0 ° C. and -70 ° C.

The mixing ratio between the copolymer of the vinyl acetate and the acrylic or methacrylic ester copolymer can be up to 1: 1 in the top layer. However, it has been shown that at such a ratio the top layer is sometimes set too soft, so that mixtures with proportions of 70 to 90 percent by weight of vinyl acetate copolymer or partially hydrolyzed polyvinyl acetate to 30 to 10 percent by weight of acrylic or methacrylic acid ester copolymer are preferred Find application.

The pigment lacquer layers provided with the combination according to the invention as a top layer can have the composition known from DE-OS 2,347,324. It consists of cellulose esters alone or as a mixture with other polymers such as acrylates, formaldehyde resins together with plasticizers and pigments. The pigment lacquer layer can also be used, as is apparent from DE-OS 2 417 879 with polyvinyl formal as the polymeric compound and amorphous silicon dioxide and titanium dioxide as the matting agent.

Compounds from the series of salts, preferably sodium salts, of polymeric sulfonic acids are present as antistatic agents in the pigment coating system according to the invention. Acetals of polyvinyl alcohol with butyraldehyde or polystyrene have proven particularly useful as polymers. The antistatic is preferably used in approximately the same proportion by weight as the acrylic-methacrylic ester interpolymer.

The thicknesses of the combination according to the invention used as the top layer, based on the layer weight, are 0.1 to 0.3 g / m ² . The known thicknesses of the pigment lacquer layers into which the combination according to the invention has been incorporated are not changed.

The cover layers are applied using one of the usual coating processes. Mixtures of alcohols and water have proven themselves as solvents. The alcohol content depends on the solubility of the raw materials, the desired wetting behavior on the surface to be coated and the adhesion of the substrate.

The top layers constructed according to the invention can also contain suitable additives such as fillers, dyes, pigments and crosslinking agents, such as compounds of metals of the IV main and subgroup of the periodic table which are soluble in the solvents used.

If the pigment coating system is used in one layer as the pigment coating layer, the components of the combination according to the invention are added to the composition of a known drawing layer. For example, they are applied together with hydrolyzed polyvinyl acetates from aqueous solution to a film with an adhesion promoter, the proportion of the components according to the invention being a maximum of 30 percent by weight, based on the polyvinyl acetate used. A proportion of antistatic above 20 percent by weight has not proven itself, because then the resistance of the pigment lacquer layer to air humidity or water decreases.

The drawing film according to the invention can also be used as a blueprint film if a layer containing light-sensitive diazochemicals, for example composed of diazonium salt and coupling component, stabilizer, etc., is applied to one side.

The following examples are intended to explain the invention in more detail.

example 1

A 75 μm thick film made of polyethylene terephthalate served as the basis and had an adhesive layer on both sides, as has become known, for example, from DE-AS 1 629 480 (GB-PS 1 127 076). Furthermore, an approximately 10 μm thick film of cellulose acetopropionate with finely divided silica and aluminum silicate as matting agent (pigment lacquer layer) was applied to the adhesive layer. Thin cover layers were applied to this pigment lacquer layer from 2.5 percent by weight solutions in equal parts of water and isopropanol and dried. They had a dry weight between 100 and 300 mg / m ² .

Table 1 shows the copolymers which can be used according to the invention in dispersion form. Table 2 shows the results of experiments in which the copolymers from Table 1 were used in the top layer in the proportions indicated in combination with a copolymer from 95 percent by weight vinyl acetate which is clearly soluble in the stated solvent mixture.

A material with a cover layer, which was produced from the copolymer of the vinyl acetate alone, served as a comparison sample.

The compliance with the line width on lines drawn on the surface with TT ink from Rotring and a tube filler for 1.4 mm wide lines was tested. After the ink had dried, the line width was measured at 29x magnification at several points in millimeters and an average was formed. The theoretical value for exact compliance with the line width is 40 to 41 mm. A larger value indicates unwanted spreading of the ink lines, a smaller value indicates poor edge sharpness.

It can be seen from this that when the copolymers are added in dispersion form, the line width of the ink is obtained in the desired width in a proportion of up to 30%. Parts with 50% addition also meet this requirement, but the layers are too soft. The wetting and adhesion were good for all samples. It also shows that in Experiment 1, a good effect can be achieved even with a relatively small addition.

• 1 Acetal des Polyvinylalkohols mit Butyraldehydsulfonsäure als Natriumsalz
• 2 Natriumsalz der Carboxymethylcellulose
• 3 Polyvinylbenzyltrimethyl-ammoniumchlorid
• 4 Poly-N,N'-dimethyl-3,5-methylen-piperi- diniumchlorid
• 5 Polystyrolsulfonsaures Natrium
• 6 Polystyrolsulfonsaures Lithium
• 7 Polyacrylsäure (Natriumsalz)
• 8 Polyacrylsäure (Ammoniumsalz)

For antistatic finishing, 2.5 percent by weight solutions were prepared from equal parts of water and isopropanol, the solids of which consisted of 80% of a copolymer with 95% vinyl acetate and 20% of an inventive copolymer (OACR-I) (solution A). This solution was mixed with 2.5 percent by weight solutions of the following compounds in a weight ratio of 5: 1.

• 1 acetal of polyvinyl alcohol with butyraldehyde sulfonic acid as the sodium salt
• 2 sodium salt of carboxymethyl cellulose
• 3 polyvinyl benzyl trimethyl ammonium chloride
• 4 poly-N, N'-dimethyl-3,5-methylene-piperidium chloride
• 5 sodium polystyrene sulfonic acid
• 6 polystyrene sulfonic acid lithium
• 7 polyacrylic acid (sodium salt)
• 8 polyacrylic acid (ammonium salt)

The width of the ink lines, the wetting of the ink TT by checking the dried lines with a magnifying glass and the surface resistance of the cover layer at 50% relative humidity and 23 ° C. with a spring tongue electrode (arrangement A) according to DIN 53482 or VDE 0303 were checked, Part 3 and 100 V measuring voltage.

Solution A served as the zero sample.

The solids ratio of the components in the formulations of copolymer with 95% vinyl acetate to the inventive copolymer to antistatic was 66:17:17.

It can be seen that the combinations with antistatic agents 1, 5 and 6 have the best results.

Example 2

Solutions containing antistatic 1 were applied to a 75 μm thick polyester film with adhesive layer and pigment lacquer layer, as described in Example 1, in which the copolymer was combined with 95% vinyl acetate and 5% crotonic acid (VAc) with the following copolymerizations according to the invention. The composition in percentages by weight was as follows:

The results are shown in Table 4. In addition, the result of the ink liability has also been entered in the table. For this purpose, 0.5 mm wide lines were drawn with India ink TT, air-dried and then checked for adhesion by pressing on an adhesive strip with the aid of a weatherstrip tool and pulling it off suddenly. With good adhesion, hardly any traces of the ink lines can be seen on the adhesive strip. In the case of poor adhesion, on the other hand, a considerable part of the ink line is removed with the adhesive strip.

Claims (7)

1. A drafting film which consists of a plastic carrier which is provided on at least one surface with an adhesive layer and with a pigmented coating system which consists of polyvinyl acetate or a copolymer of vinyl acetate and an unsaturated carboxylic acid or a partially hydrolized polyvinyl acetate, of hydrophobicity-imparting compounds and delustrants, and optionally crosslinking compounds, wherein the pigmented coating system contains, as the hydrophobicity-imparting compound, a copolymer which is formed to at least 50 per cent by weight by an acrylic or methacrylic acid ester monomer, the alcohol component of which has a chain length of at least four carbon atoms, and which does not contain vinyl acetate as a comonomer, and wherein an antistatic agent of the series of the salts of polymeric sulfonic acids is present in the pigmented coating system.

2. A drafting film as claimed in claim 1, wherein the pigmented coating system contains an acrylic or methacrylic acid ester copolymer which is formed to at least 75 per cent by weight of an acrylic or methacrylic acid ester monomer the alcohol component of which has a chain length of at least four carbon atoms, and wherein an antistatic agent of the series of the sodium salts of polymeric sulfonic acids is present in the pigmented coating system.

3. A drafting film as claimed in claim 1, wherein the mixing ratio between the vinyl acetate copolymer or partially hydrolyzed polyvinyl acetate and the acrylic or methacrylic acid ester is within a range of 70 to 90:30 to 10 per cent by weight.

4. A drafting film as claimed in claim 1, wherein the pigmented coating system contains an acrylic or methacrylic acid ester copolymer which is formed to at least 50 per cent by weight of an acrylic or methacrylic acid ester monomer the alcohol component of which has a chain length of four carbon atoms.

5. A drafting film as claimed in claim 1 or 2, wherein the pigmented coating system contains an acrylic or methacrylic acid ester copolymer which is formed to at least 75 per cent by weight of an acrylic or methacrylic acid ester monomer the alcohol component of which has a chain length of eight carbon atoms.

6. A drafting film as claimed in claims 1 to 5, wherein the pigmented coating system comprises a known pigmented layer and a top layer which contains a copolymer of vinyl acetate and an unsaturated carboxylic acid, a copolymer which is formed to at least 50 per cent by weight by an acrylic or methacrylic acid ester monomer the alcohol component of which has a chain length of at least four carbon atoms, and which does not contain vinyl acetate as a comonomer and an antistatic agent of the series of the salts of polymeric sulfonic acids.

7. A drafting film as claimed in claim 6, wherein the top layer contains a copolymer of at least 90 per cent by weight of vinyl acetate and at most 10 per cent by weight of unsaturated carboxylic acid, an acrylic or methacrylic acid ester copolymer which is formed to at least 75 per cent by weight of an acrylic or methacrylic acid ester monomer the alcohol component of which has a chain length of at least four carbon atoms, and an antistatic agent of the series of the salts of a polymeric sulfonic acid.