GB2045688A - Process for producing a plastic web decorated with a coloured and embossed or relief pattern - Google Patents

Abstract

The colour pattern (6, 7) is applied to a temporary substrate (10) in the form of a release paper by generating high contact pressure between the printing surface and the printed substrate using an intaglio or letterpress printing method. A deposit (11) consisting of a foamable unfoamed resin composition is applied to the temporary substrate (10) on top of the colour pattern (6, 7) by a screen printing process. The colour and relief or embossed pattern- forming element are then transferred from the temporary substrate (10) to a substrate (2) intended to form part of the plastic web, under heat and pressure. Heat is again applied to cause the resin to foam and provide the relief or embossed surface. Substrate (2) is preferably coated with a uniform layer (12) of foamable resin. <IMAGE>

Description

SPECIFICATION Process for producing a plastic web decorated with a coloured and embossed or relief pattern The present invention relates to a process for producing a plastic web decorated with a coloured and embossed or relief pattern, e.g.

a floor-covering material.

The invention relates to the type of covering materials for e.g. floors and walls which materials show both a coloured pattern and an embossed or relief pattern which are in registry with each other. An essential part of the product is formed by a foamed resin layer with different thickness forming a relief or embossed pattern. The colour pattern is printed on the surface of the relief or embossed patterned resin composition. In addition, the product usually comprises a substrate, e.g. a non-woven fabric, covered by the resin composition and a transparent resin layer protecting the colour and relief or embossed patterned surface of the resin composition. According to prior art the colour and relief or embossed patterns were produced mainly by one or two printing methods, i.e.

the intaglio method using steel cylinders and high contact pressure or the screen printing method using perforated cylinders, with low contact pressure. It has also been found that intaglio printing is to be preferred for the printing of the colour patterns on account of its aptitude to print half-tones and fine detail.

The resin composition which is to form the relief pattern cannot be applied by the intaglio method as more substantial quantities and/or thicknesses of foamable plastisol are needed, exceeding the transforming capacity of the intaglio process. Therefore, usually the screen printing method is utilized, which on the other hand does not allow the fine details and the good half-tone colours, resulting in a colour pattern with harsh effects and without fine shades.

In order to produce a high quality colour and relief or embossed patterned product it is desirable to use both intaglio printing and screen printing on the same product. Here great difficulties are experienced as the foamable plastisol must be applied first in the pattern providing the relief or embossment followed by intaglio printing of the colour pattern. Intaglio printing must be adapted to the screen printing and it has been found difficult to keep a good registry between the intaglio and the prior screen printing. This difficulty originates from the fact that the intaglio printing uses high contact pressure and, therefore, often causes dimensional changes in the substrate and retards or prevents the repositioning of the printing cylinders.In the prior art, these difficulties led to the acceptance of less detailed and harsher patterns as obtained also by screen printing the colour pattern. Here the pressure between the screen and the substrate, as mentioned above, is very low or non-existent as the only contact between the substrate and the printing surface is a colour film or plastisol layer and it is easy to let the printing screen cylinders slide into full registry and also keep them there during the whole printing process. Another method of the prior art applies also a foamable plastisol composition not only in the envisaged relief or embossed pattern but as an uniform layer, which is printed with inks containing foam controllants and resulting in varying thickness of the end product. In this way, the same printing process produces both the colour and relief pattern.The resulting disadvantages are regionally differing hardness of the product and uneconomic and resin consumption as the foamability of resin is used only to a minor degree in the valley areas of the pattern.

An object of the present invention is to provide a process to produce a plastic web with colour relief or embossed pattern, using intaglio printing for the colour pattern and screen printing for application of the foamable resin consumption to form the relief or embossed pattern and eliminating or minimising the above mentioned difficulties to achieve substantially perfect register.

Another object of the invention is a partitioning of the process steps with regard to time and place, making it possible to print according to the two printing methods at one place and finish the material later and/or at a different location. Also implied is the advantage of producing the pattern forming the material at a time suitable for production and storing a smaller volume product until need for the larger volume end product arises. It is also possible to utilize the printing equipment to produce the pattern material at one place which material later can be made into the finished product at one or several other places. These so called logistic advantages have shown themselves especially valuable when export is considered.

The invention provides a process in which the colour pattern is applied to a provisional substrate as a release paper by a first printing method, generating high contact pressure between the printing surface and the printed substrate as the intaglio printing method and a deposit consisting of a foamable unformed resin composition is applied to the provisional substrate on top of the colour pattern by a screen printing process and the colour and relief or embossed pattern-forming elements is transferred from the provisional substrate to a substrate intended to form part of the plastic web.

The accompanying drawings show by way of example a preferred mode of the invention; Figure 1 shows the successive build-up of a product in a schematic way; Figure 2 shows a cut-off of an end product where the different layers are visible; Figure 3 shows a first arrangement for the accomplishment of a first part of the process; and Figure 4 shows a second arrangement for the termination of the process..

The web shown in Fig. 2 comprises a substrate 2 of non-woven, preferably of glass fibre. This substrate is usually confined to floor covering materials but it is not vital for light gauge materials, e.g. for wall coverings.

The substrate 2 is covered by a layer of foamed resin 3, e.g. a PVC-resin composition.

On the foamed resin layer 3 there are relief pattern deposits 4, preferably of the same resin composition as the foamed resin layer 3.

The layer 3 and the pattern deposits 4 form together a relief patterned surface whereof only'a small sample is shown in Fig. 2. This relief pattern, identified in Fig. 2 as numeral 5, is also colour patterned with pattern elements such as a pattern element 6 placed on the relief pattern deposit 4 and pattern element 7 located on the free surface of the resin layer 3.

The relief pattern may show a more or less complicated pattern and may consist of more than two levels shown in Fig. 2. This would be accomplished by pattern deposits 4 having varying heights. Usually at least three different relief levels are used. The colour pattern registers with the relief pattern, which means that the colour pattern elements 6, 7 are located in a fixed relationship to the relief pattern deposits. The colour pattern may be more or less sophisticated with any number of different colours, pattern figures, half-tones, screen patterns etc.

The relief pattern may also contribute to the colour pattern if it consists of differently coloured deposits and of a differently coloured background, all concerting with the intaglio print pattern.

A transparent wear layer hereinafter called top layer 8 covers the colour pattern 6, 7 on the surface of the layers 3 and 4. This top layer protects the foam layer and the colour pattern from abrasion and mechanical destruction. If the final product is to be exposed to minor wear only, e.g. a wall covering material, a wear layer is not imperative as in the case of floorings.

Fig. 1 shows schematically the preparation of the different parts constituting the end product. The pattern is made by first producing the pattern-forming material 9. Here one starts with a so-called release paper 10, which is intaglio printed with a reverse picture of the colour pattern elements 6, 7. Thereafter the deposits 11 comprising a foamable plastisol and intended to form the relief elements 4 are printed in register with the elements 6, 7. In Fig. 1 the elements 6, 7 and 11 are all shown with considerable thickness for the sake of distrinctness only. In reality the thicknes of pattern elements 6, 7 is only a few micrometres whereas the deposits 11 prior to foaming would show a thickness of about one or a few tenths of a millimetre.

Independently of the production of the pattern-forming material 9, the substrate 2 is coated with a layer 1 2 of a foamable resin composition and pregelled. The production may proceed whenever the substrate is provided with the layer 1 2. The pattern-forming material 9 is thereby placed in contact with the layer 1 2 in the presence of pressure and heat. Due to the special releasing properties of the, usually silicone impregnated, paper and to the adhesive action of layer 12, the elements 6, 7 and 11 are transferred to the layer 1 2. The release paper 10 is then removed and the colour patterned and faintly relief patterned material may be covered with a transparent resin composition in a subsequent operation which forms the transparent top layer 8.This is shown somewhat to the right of the contact point between the release paper 10 and the layer 1 2 whereas to the right in Fig. 1 the material is shown after having been heated to its final appearance. Here the layer 1 2 has foamed and forms the foam plastic layer 3 and the deposits 11 have foamed and form the relief pattern elements 4 in the intended relief level on the surface of the relief. The colour pattern elements 6, 7 are in turn covered by the transparent top layer 8.

From this it can be understood that it is a characteristic of the method not to apply the pattern-forming elements directly to the final substrate, but to a provisional substrate, from which they are transferred to the final one.

This means that it is the layer on the provisional substrate (i.e. the release paper 10), which is to form the pattern elements on the final substrate, the free surface of the pattern elements on the provisional substrate having to be brought in contact with and secured to the final substrate whereas the outer surface of the pattern elements, which is to form the outer side of the pattern elements has to be turned towards the release paper. In other words the pattern elements are applied to the release paper in reverse order compared to what would have been the case if they had been applied directly to the final substrate.

Therefore, the colour pattern elements are applied first and are followed by the relief pattern deposits in a later printing step. In this way the advantage is obtained that intaglio printing can be done without any adjustment of register to a prior pattern. If intaglio printing is done in several colours, which is quite usual, several printing steps are necessary and there, of course, registry must be insured.

These, however, are minor difficulties; as these different colours can be printed on the same printing machine and with cylinders of the same type, no serious problems are en countered. Also, the control of registry is relatively easy as the printing is done on the release paper, a material of relatively low elasticity. One gains the double advantage of not needing to intaglio print in registry with an earlier pattern and using the more suitable substrate for intaglio printing compared to the resinious material used as a substrate for direct printing according to earlier methods.

The important point, is that the control of intaglio print registry with an earlier pattern applied by means of a different printing method is no longer necessary.

In Fig. 3 the shown arrangement is intended for printing the release paper. The machine has a shaft 13 intended for a roll 14 of release paper 1 0. The release paper web is unwound from the roll 14, passes over an idler roll 1 6 and through an intaglio print machine 15, shown in Fig. 2 with three printing cylinders and allowing printing with up to three different colours. The printed release paper passes additional idler rolls and a control station 1 7 to the screen printing device 1 8. Here only one rotary screen is shown but several may be employed if more than one relief level is envisaged.After several more idler rolls 1 6 the release paper web passes through an oven 21 and is rewound on a shaft 20 into a roll 23 containing the finished pattern forming material.

Fig. 4 shows an arrangement in which the pattern-forming material is laminated to the permanent substrate. It comprises (Fig. 1) a substrate with a pre-gelled plastic layer 12.

This material hereinafter called back-lamina 22 is unwound from the roll 24 on a shaft 25 obviously after having been prepared previously. This preparation comprises the doctoring of the plastic layer 1 2 onto the substrate 2 followed by pre-gelling in an oven. Although not so shown in Fig. 4, this may also be done in the shown machine. In that case, the roll 24 comprises the substrate which passes a doctor blade and a pre-gelling oven.

From another roll 26 on the shaft 27 the pattern-forming material, the same as shown collected on roll 23 of the machine in Fig. 3, is unrolled. After passing the ider rolls 28, 29 both materials are brought together and pass around a heated drum 30 rotating about a shaft 31. The printed release paper 10 from the roll 26 is brought into contact with the layer 1 2 on the back-lamina 22 with its printed side. After passing part of the circumference of drum 30, the webs are separated from each other by an idler roll 32 and the release paper 10 is rewound on roll 33 on axle 34. The other web passes over an idler roll 35 under the doctor blade 36 for application of the transparent resin composition of the top layer 8.

By receiving the pattern elements from the release paper 10 during the passage over the heated drum 30 and after coating with the transparent resin composition forming the top layer, the back-lamina 22 is now complete and is led through the oven 37. There the resin composition 1 2 and the relief pattern deposits 11 (compare Fig. 1) are foamed to their final thickness. In connection herewith, the plastic layers gel and after cooling, the product is rewound into the roll 38 on shaft 39.

In the first step in the machine line of Fig.

3 the release paper 10 is printed in the intaglio printing station 1 5. The printing layer lies in direct contact with the release paper. In a next step, foamable plastisol is applied in the screen printing station 1 8 on top of the foregoing layer. As there is only very low contact pressure-if any at all-between the rotary screen cylinders and the paper web, the registry is easily controlled. The correcting action can be automated as shown in the drawing by use of control station 1 7 which works over one or several photocells which react to marks applied during the intaglio printing in the first step. The finished pattern forming material is wound up in roll 23.

Being relatively thin, it is easy to store and, also, to convey to other places for the finishing operation as shown in Fig. 4. E.g. it is possible to deploy the printing step, which demands high precision and technology, at one location whereas the finishing operation may be conducted somewhere else using less sophisticated equipment.

The arrangement of Fig. 4 is used as said above for the transfer of the pattern elements to the permanent substrate, i.e. the backlamina 22. This is accomplished by the application of pressure and heat which make the pattern elements stick to the resin layer 1 2 as they concomitantly release from the silicone impregnated release paper. In this fashion, the colour pattern produced in the intaglio printing step 1 5 covers the still latent relief pattern deposits 11. They are foamed to their full gauge by heating in the oven 37 to form the final relief pattern elements 4.

In the foregoing it was assumed that the colour pattern was produced by the intaglio method only, while it is indeed a very suitable method in this connection, this should not be construed to exclude other printing methods, e.g. letter press characterized by the colour being transferred by the land parts instead of the valley parts of the printing cylinder in the case of intaglio.

This difference does little to relieve the problems encountered when trying to change the position of the printing cylinders relstive to the printing substrate; they are of the same order as those met with the intaglio method.

Thus, the present invention is applicable and advantageous whenever the said conventional processes prescribe the application of relief forming deposits to printing the colour pattern and difficulties are experienced with keeping the different types of patterns in registry.

When producing the patternforming material according to the present invention, it is essential to apply the colour pattern prior to the relief pattern. It was assumed that the pattern-forming deposits comprise a foamable resin applied exclusively by screen printing, yet mention was made of more than two relief levels. To achieve this, several types of resin compositions with different foamability are printed every one with its own screen. Differences in pattern levels may also be realised by applying the foamable resin compositions in different thicknesses which among other measures may be done by varying the viscosity of the resin composition. According to another embodiment of the invention, the process may be reversed by printing with a non-foamable resin composition, followed by pre-gelling and doctoring with a foamable resin composition.

As the slightly elevated non-foamable deposits support the doctor blade, the foamable resin composition will be found almost exclusively in the interstices between the patterns formed by them. In this fashion too, limited surface areas of foamable resin composition are achieved which, by stoving, are transformed into the relief. If several levels are desired, non-foamable resin compositions are applied in different thicknesses. Consequently, the foamable resin composition will be present in maximum thickness only where no deposits of non-foamable resin compositions are found, whereas limited thicknesses result where nonfoamable resin deposits of less than maximum thickness are situated. The highest levels of the non-foamable resin composition support the doctor blade and virtually none of the foamable resin composition will be found in these places.In this way several thicknesses of the foamable plastic composition can be realized resulting in a relielf pattern with different levels. Also in cases where a foamable resin composition has been screen printed it is feasible to coat with still another layer. This would be done using a non-foamable resin composition and aims at smoothing the layer on the release paper, which increases the ease of rewinding and the later transfer to the final substrate. Therefore, it is quite feasible to apply the layer 1 2 on top of the pattern elements and join the assembly directly with a substrate such as a carrier. In that case all resin layers but the wear layer are located on the release paper but this, given a greater thickness to the pattern forming material, is generally considered as less advantageous.

Under some circumstances it still may be preferable to have a large part of the layers located on the preliminary substrate. Such circumstances have been describd at the outset of the description and are relevant whenever it is desired to separate the several steps of the process with regard to timing and/or location. In addition, it may de desirable to supply the provisional substrate with the top layer 8 as well, which in the foregoing was assumed to be applied by doctoring after the transfer of the colour pattern and the relief pattern elements from the release paper 1 0.

Instead, first the transparent resin composition 8 may be coated onto the release paper, followed by printing the colour pattern elements 6, 7 and, thereafter, the resin composition intended to form the relief pattern deposits 4. In this fashion the intaglio and the screen printing are not done directly on the release paper 10 but rather on the pregelled layer of a transparent resin composition. After screen printing as before still other resin compositions may be applied including, if so desired, the resin composition forming the layer 1 2. After transfer to the final substrate, the top layer 8 will constitute the surface and no additional application of a layer is necessary.

Apart from the separation in time or/and place the application of the top layer composition an additional effect is an increased ease of producing a top layer with even thickness.

Doctoring the resin composition onto the substrate with the transferred pattern so as to cause variations in thickness results in thickness variations of the top layer, or to be more precise, the top layer will be thicker in the valley parts of the pattern and thinner above the land parts which is the exact opposite of what is desirable with regard to protection against wear. Applying the resin composition of the top layer to the release paper with its substantially perfect surface results in an extremely even wear layer.

In this fashion, the method leaves a wide choice of how to group the different layers onto the final substrate in the different steps of the procedure. One extreme is the case where colour and relief pattern elements alone are applied to the release paper whereas at the other end of the scale all resin compositions may be applied to the release paper for transfer to a carrier. In one important variant the top layer is located on the release paper together with the colour and relief patternforming elements.

As demonstrated the pattern-forming material can be produced in different ways. It is, however, essential that the layer forming the colour pattern is placed nearest the release paper followed by deposits forming the foamable relief pattern elements in this order.

According to different embodiments of the process these pattern elements are screen printed in a direct or reverse print procedure and optionally augmented with additional resin layers without departing from the scope of the invention.

Claims (14)

1. Process for the production of a plastic web decorated with a colour and embossed or relief pattern, comprising the application of deposits of a foamable resin composition to a substrate, application of a colour pattern on the surface of the substrate and of the thereon located deposits so as to constitute an embossed or relief pattern in register with the colour pattern, in which the following successive steps are comprised: applying colour pattern elements to a provisional substrate not to be integrated into the final product as a release paper by a first printing method of the kind generating high contact pressure between the printing surface and the printed substrate as the intaglio printing method; applying deposits consisting of a foamable unfoamed resin composition intended for the forming of relief pattern elements to the provisional substrate and on top of the colour pattern by a screen printing process; transferring the elements for the forming of the colour and relief pattern from the provisional substrate to the said substrate intended to form part of the plastic web by bringing the pattern-covered side of the provisional substrate under pressure into contact with the substrate prepared to receive the said pattern; treating as by heat the provisional substrate and the contacting permanent substrate so as to cause the pattern elements to release the provisional substrate and to adhere to the permanent substrate, which carries the colour pattern close to or on its surface and the deposits thereunder; heating the web to expand the foamable resin compositions thereby expanding the deposits to form the land areas of the relief pattern and gelling the resin compositions to produce the finished product.

2. Process according to claim 1, in which the foamable resin composition intended to form the land areas of the embossed or relief pattern is formed by said deposits, printed directly with a screen according to the rotary screen printing method.

3. Process according to claim 2, in which deposits are provided of a foamable resin composition in the form of elements of different thicknesses resulting in an embossed or relief pattern with several levels.

4. Process according to claim 2, in which the application deposits are provided of several resin compositions differing in their foamability resulting in an embossed or relief pattern with several levels.

5. Process according to claim 1, in which said deposits are formed of a first resin composition applied to the provisional substrate by screen printing and a second resin composition filled into the interstices between the first said deposits by means of a doctor blade, the resin compositions differing in their foamability.

6. Process according to claim 5, in which the first resin composition is substantially lacking foamability and the second resin composition being foamable.

7. Process according to claim 5, in which the first resin composition being foamable and the second resin composition is substantially lacking foamability.

8. Process according to claim 5, in which an additional third resin composition is applied to the substrate by screen printing in a thinner layer than said first resin composition so that after the application by doctor blade the second resin composition forms its thickest layer at locations where the provisional substrate carries deposits of neither the first not the additional third resin compositions and forms thinner layer at locations where the first and the additional third resin compositions are applied to the provisional substrate.

9. Process according to claim 8, in which the first and the additional third resin compositions are substantially lacking of foamabiliity and the second resin composition being foamable.

1 0. Process according to claim 8, in which the first and the additional resin compositions being foamable and the second resin composition is substantially lacking foamability.

11. Process according to any one of the preceding claims in which there is applied a substrate layer comprising a foamable resin composition to the provisional substrate after the application of the colour and relief pattern elements and after the possible application of further resin compositions, and by its subsequent transfer to the remaining substrate in connection with the transfer of the colour and pattern elements.

1 2. Process according to any one of the preceding claims, in which a transparent resin composition is applied to the provisional substrate prior to the application of the colour and embossed or relief pattern forming elements and prior to the application of further resin compositions, so that the transparent resin composition is transferred to the substrate in connection with the transfer of the colour and embossed or relief pattern forming elements, the end product after the transfer showing a toplayer of the transparent resin composition.

1 3. Process substantially as herein described and illustrated with reference to the accompanying drawings.

14. The invention substantially as herein described.