GB2162015A - Method of screen printing - Google Patents

Abstract

A method is described for producing a screen for printing a selected colour of a photographic image in which each colour area of the image comprises a plurality of component colour islands which together produce the colour perceived for said area. The method comprises scanning the image with electronic detector means to detect the colour islands of a selected scanned colour. A printing screen is then prepared from a blank of material by forming in the material a pattern of apertures which extend uninterrupted through the entire thickness of the material under the control of information obtained from the detector means. There is thus produced a printing screen with a pattern of apertures corresponding to the pattern of colour islands as of the scanned colour islands in the photographic image.

Description

SPECIFICATION Production or printing screens This invention relates to the production of screens for use in screen printing operations.

GB-A-2106741 (Summerseat Island Prints Ltd) describes a screen printing method for reproducing a photographic image in which each colour area of the image comprises a plurality of component colour islandswhich together produce the colour perceived.

The method comprises scanning the image with electronic detector means to detect the colour islands of a selected scanned colour, preparing for each scanned colour a screen for printing the detected islands of that colour as a matrix of individual dots, and printing each colour using the respective screen.

As described in the aforesaid specification, the screens are produced as follows.

Firstly, and using conventional techniques, a matrix of opaque islands (corresponding in position to the colourislandsto be printed) is produced on a transparent film. Secondly,thefilm is laid onto a printing screen mesh coated with a cross-linkable emulsion and the screen is irradiated through the film to cross-linkthe emulsion otherwise than at the locations of the opaque islands. Thirdly, the film is removed and the screen washed to remove the non-cross-linked resin thereby producing a screen for printing colour islands at the required locations.

This method of producing the screens does howevear have a number of disadvantages. In particular, the production method requires a number of separate steps and moreoverthere may be problems incurred during the printing operation with moire effects due to the fact that printing is effected through a portion of screen mesh.

It is an object ofthe invention to obviate or mitigate the abovementioned disadvantages.

According to the present invention there is provided a method of producing a screen of printing a selected colour of a photographic image in which each colour area ofthe image comprises a plurality of component colour islands which together produce the colour perceived for said area, the method comprising scanning said image with electronic detector means to detectthe colour islands of a selected scanned colour, and preparing a printing screen from a blank of material by forming in the material a pattern of apertures which extend uninterrupted through the entire thickness of the material underthe control of information obtained from the detector means, whereby there is produced a printing screen with a pattern of apertures corresponding to the pattern of colour islands ofthe scanned colour islands in the photographic image.

The invention also provides a method offorming a screen printed reproduction of a photographic image comprising preparing a printing screen in accordance with the abovedefined method for each of a plurality of colours for which the photographic image is scanned, and 6sing the thus prepared screens successivelyto print each of the respective colours for which they have been prepared thereby to produce a screen printed reproduction of the photographic image.

The present method offorming a printing screen thus differs from that described in GB-A-2106741 in that, in the present invention, the printing screen is formed directly from the information obtained bythe detector means by producing aperturesthrough the entire thickness of the material from which the screen is produced. The apertures are provided in the material only where required and the method avoids the need to impregnate a mesh material with a resin.

Each aperture extends continuously from one face of the material to the other face and is uninterrupted by screen mesh, as is the case in the screens produced by the method described in GB-A-21 06741. This has advantages in avoiding moire effects when the screen is used in a printing operation.

The aperture in the blank of material may be produced, for example, by a laser controlled by a computer associated with the detector means. Alternativelythe aperture may be produced by drilling or any other suitable means. The material from which the screen is produced may, for example, be metal or plastics.

The method of the invention forforming printing screens is particularly useful for producing screens for rotary printing operations.

The method of scanning the photographic image and the subsequent printing operations are as described in GB-A-2106741.

1. A method of producing a screen for printing a selected colour of a photographic image in which each colour area ofthe image comprises a plurality of component colour islands which together produce the colour perceived for said area,the method comprising scanning said image with electronic detector means to detectthe colour islands of a selected scanned colour, and preparing a printing screen from a blank of material by forming in the material a pattern of apertures which extend uninterrupted through the entire thickness of the material underthecontrol of information obtained from the detector means, whereby there is produced a printing screen with a pattern of apertures corresponding to the pattern of colour islands as of the scanned colour islands in the photographic image.

2. A method as claimed in claim 1 wherein the aperturesareformed bya laser.

3. A method of forming a screen printed reproduction of a photographic image comprising preparing a printing screen by the method of claim 1 for each of a plurality ofcolours for which the photographic image is scanned, and using the thus prepared screens successively to print each ofthe respective colours for which they have been prepared, thereby to produce a screen printed reproduction of the photographic image.

4. A method of producing a printing screen substantially as hereinbefore described.

5. A method offorming a screen printed reproduction of a photographic image substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Production or printing screens This invention relates to the production of screens for use in screen printing operations. GB-A-2106741 (Summerseat Island Prints Ltd) describes a screen printing method for reproducing a photographic image in which each colour area of the image comprises a plurality of component colour islandswhich together produce the colour perceived. The method comprises scanning the image with electronic detector means to detect the colour islands of a selected scanned colour, preparing for each scanned colour a screen for printing the detected islands of that colour as a matrix of individual dots, and printing each colour using the respective screen. As described in the aforesaid specification, the screens are produced as follows. Firstly, and using conventional techniques, a matrix of opaque islands (corresponding in position to the colourislandsto be printed) is produced on a transparent film. Secondly,thefilm is laid onto a printing screen mesh coated with a cross-linkable emulsion and the screen is irradiated through the film to cross-linkthe emulsion otherwise than at the locations of the opaque islands. Thirdly, the film is removed and the screen washed to remove the non-cross-linked resin thereby producing a screen for printing colour islands at the required locations. This method of producing the screens does howevear have a number of disadvantages. In particular, the production method requires a number of separate steps and moreoverthere may be problems incurred during the printing operation with moire effects due to the fact that printing is effected through a portion of screen mesh. It is an object ofthe invention to obviate or mitigate the abovementioned disadvantages. According to the present invention there is provided a method of producing a screen of printing a selected colour of a photographic image in which each colour area ofthe image comprises a plurality of component colour islands which together produce the colour perceived for said area, the method comprising scanning said image with electronic detector means to detectthe colour islands of a selected scanned colour, and preparing a printing screen from a blank of material by forming in the material a pattern of apertures which extend uninterrupted through the entire thickness of the material underthe control of information obtained from the detector means, whereby there is produced a printing screen with a pattern of apertures corresponding to the pattern of colour islands ofthe scanned colour islands in the photographic image. The invention also provides a method offorming a screen printed reproduction of a photographic image comprising preparing a printing screen in accordance with the abovedefined method for each of a plurality of colours for which the photographic image is scanned, and 6sing the thus prepared screens successivelyto print each of the respective colours for which they have been prepared thereby to produce a screen printed reproduction of the photographic image. The present method offorming a printing screen thus differs from that described in GB-A-2106741 in that, in the present invention, the printing screen is formed directly from the information obtained bythe detector means by producing aperturesthrough the entire thickness of the material from which the screen is produced. The apertures are provided in the material only where required and the method avoids the need to impregnate a mesh material with a resin. Each aperture extends continuously from one face of the material to the other face and is uninterrupted by screen mesh, as is the case in the screens produced by the method described in GB-A-21 06741. This has advantages in avoiding moire effects when the screen is used in a printing operation. The aperture in the blank of material may be produced, for example, by a laser controlled by a computer associated with the detector means. Alternativelythe aperture may be produced by drilling or any other suitable means. The material from which the screen is produced may, for example, be metal or plastics. The method of the invention forforming printing screens is particularly useful for producing screens for rotary printing operations. The method of scanning the photographic image and the subsequent printing operations are as described in GB-A-2106741. CLAIMS

1. A method of producing a screen for printing a selected colour of a photographic image in which each colour area ofthe image comprises a plurality of component colour islands which together produce the colour perceived for said area,the method comprising scanning said image with electronic detector means to detectthe colour islands of a selected scanned colour, and preparing a printing screen from a blank of material by forming in the material a pattern of apertures which extend uninterrupted through the entire thickness of the material underthecontrol of information obtained from the detector means, whereby there is produced a printing screen with a pattern of apertures corresponding to the pattern of colour islands as of the scanned colour islands in the photographic image.

2. A method as claimed in claim 1 wherein the aperturesareformed bya laser.

3. A method of forming a screen printed reproduction of a photographic image comprising preparing a printing screen by the method of claim 1 for each of a plurality ofcolours for which the photographic image is scanned, and using the thus prepared screens successively to print each ofthe respective colours for which they have been prepared, thereby to produce a screen printed reproduction of the photographic image.

4. A method of producing a printing screen substantially as hereinbefore described.

5. A method offorming a screen printed reproduction of a photographic image substantially as hereinbefore described.