HK1019721B - Process for the manufacture of a colour-marked object - Google Patents

Description

Method for manufacturing color-marked object and laser device

The invention relates to a method for manufacturing an object with colour marks (colormarked) by irradiating the surface of the object with laser light.

Such a process is known from WO 94/12352. This patent application discloses a method for producing a colour marking by irradiating the surface of an object under optional conditions.

A disadvantage of this known method is that the resulting color is not freely selectable, but is formed randomly. Moreover, only a limited number of colors of the marking are available.

The object of the present invention is to provide a process which does not have the above-mentioned disadvantages.

Surprisingly, this object is achieved by an object which, at least at the location where the marking is applied, consists of a plastic composition containing at least three light-absorbing components; the light absorption components have a maximum in the absorption spectrum at different wavelengths and lose their light absorption capacity under the action of laser light; the marking is applied in the form of a matrix dot and the surface of the object at the location of the matrix dot is irradiated with a laser having a wavelength, intensity and irradiation time such that at least one light-absorbing component loses its light-absorbing capacity completely or partly.

In this way, a marking of a freely determined colour can be obtained, which marking can contain different colours, and which marking of different colours can be obtained on the surface of the same plastic composition. Moreover, such markings obtained on the surface of the same plastic composition can even have many different colors.

The matrix dots take on the spectral color absorbed by the color absorbing component before the color absorbing component has lost its light absorbing capacity, either completely or partially.

It is well known that the light-absorbing component is a component having a color, for example: dyes and pigments. It is also known that the light-absorbing component does not comprise a white or black component, for example: titanium dioxide, chalk, barium sulphide, carbon black or iron sulphide.

Most importantly, the light absorbing component does not lose or hardly loses its light absorbing capacity in normal daylight. For this purpose, the light-absorbing component should have a color stability, on the Wool scale (Wool scale) (to DIN54003), of at least 5, more preferably at least 7, and even more preferably above 7.

An example of a suitable light-absorbing component is Irgalith^Rubine 4BP, a magenta colored pigment; irgalith Blue LGLD, a cyan colored pigment; or Cromopthal^Yellow 6G and Cromopthal Yellow 3G, two Yellow coloring pigments. Incidentally, most light-absorbing components lose all or part of their light-absorbing ability by laser radiation.

The invention enables the application of matrix dots to a surface in a simple manner.

The absorption capacity of the preselected light-absorbing component is reduced by irradiation with a laser of a specific wavelength: the surface of the irradiation site will reflect a color that the component in question is not capable of re-absorbing. The brightness of the reflected color can be increased by increasing the intensity of the laser or by extending the irradiation time.

The indicia of the color of interest may be formed by applying a plurality of matrix dots on the surface.

It is also possible to apply matrix dots of different colors to the surface side by side. The surface color of the matrix dot location is a blend of colors for the viewer, since the color of the matrix dot is projected onto the naked eye by the blend. Such a color mixing method in which colors to be mixed are arranged side by side is called a partial method. Color mixing is determined by the surface area ratio of the matrix dots and the color intensity ratio. In this way, a number of mixed colors can be formed.

Most importantly in this context, the center-to-center distance between the matrix dots is so small that the individual matrix dots cannot be distinguished by the naked eye. The news pictures are also colored in this way.

As is known from color printing, the application of at least three differently colored substrate dots to a surface gives very good results. This can be achieved by irradiating the surface with laser light of at least three different wavelengths, in the course of which one of the at least three light-absorbing components loses its light-absorbing capacity at each wavelength completely or partly. In this way, the application of at least three colors enables the formation of many other colors by blending the appropriate amounts of color.

Color mixing can be performed in many ways. Color mixing is accomplished, for example, by varying the intensity of the color of the matrix points relative to one another, e.g., by irradiating matrix points of a particular color that are longer than other matrix points. In addition, the total area ratio of different colors can be changed by, for example, preparing a larger number of matrix dots than other matrix dots, or forming a larger number of matrix dots of one color than other matrix dots. The matrix points may be round or square, but may also be, for example, triangular or linear, for example, in order to better fill the surface or to increase the total reflection of the surface.

The color is characterized in that, according to ASTM standard E308, the tristimulus values of the color are first determined, and then the position of the color in the CIE D65 color diagram (10 ℃ observer) is determined by calculating the chromaticity coordinates therefrom as described in the above standard. As such, the color map is an illustration of all colors in the visible range.

The distributive mixing technique may form colors that are located in the color map in areas between points representing at least three different colors of the base dot in the color map. These points form the peaks of the region.

The method of the invention for obtaining more distinct colors comprises applying the matrix dots in a wholly or partially overlapping manner. This color mixing technique is called subtractive color mixing.

Preferably, the surface color is determined by subtractive color mixing of at least three different colored base dots. The range of colors emitted from the subtractive color mixing is greater than in the case of the assigned mixing because the colors formed are located outside the region in the color map between the points representing the at least three different colors of the base dot in the color map.

The plastic composition may in principle comprise any thermoset or thermoplastic or elastomer. The plastics which the plastics composition described in WO94/12352 can comprise are particularly suitable.

Preferably, the light-absorbing components are selected such that the area between the points representing at least three different colors of the matrix points in the color map covers at least 10% of the area of the map.

Preferably, the area covers at least 30% of the map, more preferably at least 75% of the map.

The wavelength of the laser used to irradiate the surface so that the predetermined light-absorbing component loses its light-absorbing capacity can be readily determined by experimentation.

Preferably, the surface is irradiated with a laser wavelength at which a maximum appears in the absorption spectrum of the light-absorbing component that loses its light-absorbing capacity. In this way, very good color selectivity and brightness can be achieved.

Preferably, the method of the invention is performed using one or more masks. Such masks are transmissive in the surface locations to be irradiated and non-transmissive in the surface locations not to be irradiated. The continuous irradiation of the surface with lasers of different masks and different wavelengths allows matrix dots of different colors to be quickly and easily applied to the surface.

The advantage of this method is that the size of the matrix spot is determined by the mask and not by the diameter of the laser beam, and therefore the surface can be irradiated with a laser beam of large diameter. As a result, the irradiation time is shorter.

Preferably, the method of the invention is performed with a variable mask.

It is preferable to use a mask made of an LCD (liquid crystal display) panel.

More preferably, a PDLCD (polymer dispersed liquid crystal display) mask is used, which has the additional advantage that it does not absorb, but scatters the non-transmitted laser beam, so that the mask does not heat up.

The advantage of such masks is that the ideal mask can be computer-fabricated on LCD screens and PDLCD screens. The surface can then be irradiated through a mask. Thereafter, another mask is compensated for on the same positioned screen. In this way, possible positional deviations are avoided. Another advantage is the ability to quickly change different masks.

If the method according to the invention is carried out by irradiating the object surface simultaneously with a laser device by means of at least three masks which are located next to one another, the masks are irradiated with laser light of different wavelengths in such a way that the mask images are projected one on top of the other onto the object surface. Then good results are not obtained. This has the advantage that the object surface is irradiated with different masks in one operation. If the mask is variable during this process, a further advantage is the ability to apply the different marks in rapid sequence. The same kind of mechanism is known from image projection.

The method can also be carried out using a controllable laser beam of variable intensity. This implementation has a great flexibility with respect to the shape and color brightness of the object to be irradiated.

In addition, a laser device having a tunable wavelength is also preferable since a surface can be irradiated with laser light of different wavelengths by one laser device.

Preferably, the laser is capable of emitting light of different wavelengths that match the absorption spectrum maxima of the different light absorbing components. Thus all possible colors can be formed using one laser.

More preferably, a laser device is used which combines at least three laser beams of different wavelengths in one fibre, which device is capable of varying the intensity of each beam independently of the other beams. The advantage is that it is easy to radiate the object surface with a composite laser beam that can emit all colors. As a result, there is a high flexibility in terms of the number of colours that can be selected and the shape of the applied indicia.

Example 1

A dry blend was prepared from 1897 parts by weight of Ronfalin^SFA-34, acrylonitrile-butadiene-styrene copolymer (ABS) from DSM (the Netherlands); 100 parts by weight of Tiofine^R41, titanium dioxide pigment from tiofini (netherlands); and 1 part by weight of Iraglith^Rubine 4BP, 1 part by weight Irgalith BlueLGLD and 1 part by weight Cromopthal^YelloW 6G, in that order, are magenta, cyan and YelloW colored pigments from the Messrs Ciba Geigy company (the Netherlands).

Dry blends were applied to ZSK from Weiner and Pfleiderer, Germany^Kneading and pelletizing at 260 ℃ in a 30-twin-screw extruder. Placing the pellets in an Arburg Allrounder^Injection molding in a 320-90-750 injection molding machine at 240 ℃ into 3.2X 120 mm tablets. The in-chip colored pigment absorbs visible light. The tablets were light grey.

Thereafter a mark is applied to the surface by means of a laser device. A wavelength tunable laser device (TMW laser device) is applied. The laser device is provided with an EEO^-355 seeding technology laser (seeding laser) for use as GCR^-230/50 type Nd: YAG laser. In addition, the laser device is provided with MOPO^710 type lightAn Optical Parametric Oscillator (OPO) receives the signal emitted by the laser described below by means of a frequency doubling optical lens (FDO). The device is available from Spercra-Physics, Inc. of the United states.

The laser settings were selected as follows:

pulse width: 5 ns

Switching circuit quality factor frequency (Q-switching frequency): 30 Hz

Dot diameter: 3 mm

Recording speed: 10 mm/s

Spectral line spacing: 0.66 mm

Focal length: +80 mm

Colored light is applied to the sample by means of the laser device described above in the following manner. The colored light is subdivided into a "red mask", a "green mask" and a "blue mask" (selective: split channel RGB) by means of the "Corel-photoprint 5.0 for Hewlett Packard" of Corel corporation, USA. "Spectra Star from Messrs General Parametric corporation, USA was used^TMGTx "color printer, which prints these black/white masks on transparent objects. For accurate positioning, a cross is placed around the image.

Subsequently, a "blue mask" was placed on the above sheet and irradiated with a 450 nm wavelength laser. Next, the mask is removed, replaced with a "green mask" and accurately positioned over the resulting image of the "blue mask". The "green mask" was irradiated with a laser having a wavelength of 530 nm. Finally, a "red mask" was placed and irradiated with a 650 nm wavelength laser. At the completion of this final irradiation, an indelible coloured light is obtained on the plastic, the colour range of which is comparable to the original colour range.

Example 2

A lacquer consisting of 65.0 parts by weight of Uracron was prepared in a beaker with vigorous stirring^474CY, from DSM resins, Inc. (Netherlands)A hydroxy-functional resin; 20.8 parts by weight of Tolonate^HDT EV 412 available from Huls corporation (Germany); 0.6 part by weight of dibutyltin dilaurate (Dibutyllidilaurate) available from Aldrich Co., Belgium; 10 parts by weight of Kronos^CL220, 1.2 parts by weight of Cromoptal^Yellow 3G, a Yellow pigment from Ciba Geigy, Netherlands; 1.2 parts by weight of Paliogen^Red pigment from Red L3910 HD, BASF corporation (Netherlands) and 1.2 parts by weight of Orasol^A Blue colorant from Blue GN, Ciba Geigy, Netherlands. The lacquer was applied to an aluminum sheet with a film thickness of 50 microns. The paint film is grey. Paint film markings were made as described in example 1 above.

The experimental laser was set to:

pulse width: 5 ns

Conversion circuit quality factor frequency: 30 Hz

Dot diameter: 3 mm

Recording speed: 25 mm

Spectral line spacing: 0.66 mm

Focal length: +40 mm

Claims (11)

1. A method of manufacturing an object having a color mark by irradiating a surface of the object with laser light; characterized in that the object, at least at the location where the marking is applied, consists of a plastic composition containing at least three light-absorbing components; the light absorption components have a maximum value in the absorption spectrum of the light absorption components under different wavelengths, and lose the light absorption capacity under the action of laser; the marking is applied in the form of a matrix spot and the surface of the object at the location of the matrix spot is irradiated with a laser having a wavelength, intensity and irradiation time such that at least one light-absorbing component loses its light-absorbing capacity completely or partly.

2. A method according to claim 1, characterized in that the surface color is formed by subtractive mixing of at least three differently colored matrix dots.

3. A method according to claim 1, characterized in that the surface colour is formed by means of distributive mixing of the colours of the matrix dots.

4. A method according to claim 1, characterized in that the light-absorbing components are selected in such a way that the area between the points representing at least three different colors of the matrix points in the color map covers at least 10% of the area of the map.

5. A method according to any one of claims 1 to 4, characterized in that the surface is irradiated with a laser wavelength at which maxima occur in the absorption spectra of the different light-absorbing components.

6. A method according to any one of claims 1 to 4, characterized in that the method of the invention is carried out by means of one or more masks.

7. The method according to claim 6, characterized in that the method of the invention is carried out by means of a variable mask.

8. The method of claim 6, wherein the mask is made of an LCD panel.

9. Method according to claim 6, characterized in that a variable PDLCD (polymer dispersed liquid crystal display) mask is used.

10. A method according to any one of claims 1-4, characterized in that the surface is irradiated with a laser device which irradiates the object surface simultaneously with at least 3 masks positioned adjacent to each other, the masks being irradiated with laser light of different wavelengths in such a way that the images of the masks are projected one on top of the other onto the object surface.

11. A laser device, characterized in that at least three laser beams of different wavelengths are combined in one fiber and the intensity of each beam can be varied independently of the other beams.