CN1208376A - Method for manufacturing color-marked objects - Google Patents

Abstract

Method for producing an object with a colour marking by irradiating the surface of the object with laser light, characterized in that the object, at least at the location of its application of the marking, consists of a plastic composition containing at least three light-absorbing components which have a maximum in their absorption spectra at different wavelengths and which lose their light-absorbing power under the influence of laser light, and in that 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 laser light of a wavelength, intensity and irradiation time such that at least one of the light-absorbing components loses its light-absorbing power completely or partly.

Description

Method for manufacturing color-marked objects

The present invention relates to a method for manufacturing a color marked object by irradiating the surface of the object with a laser.

Such a method is known from WO 94/12352. This patent application discloses a method of irradiating the surface of an object under optional conditions to produce colored markings.

A disadvantage of this known method is that the resulting colors cannot be chosen freely, but are formed randomly. Furthermore, markings are only available in a limited number of colors.

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

Surprisingly, this object has been achieved with 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; There is a maximum value in the absorption spectrum and loses its light-absorbing ability under the action of laser; the mark is applied in the form of a matrix dot (matrix dot), and the wavelength, intensity and radiation time should be such that at least one light-absorbing component Laser light that has completely or partially lost its light-absorbing ability irradiates the surface of the object at the position of the matrix point.

In this way, a freely determinable color marking can be obtained which can contain different colors and which can be obtained on the surface of the same plastic composition. Moreover, such marks can even be obtained in many different colors on the surface of the same plastic composition.

The matrix dots have the spectral color absorbed by the color-absorbing component before the color-absorbing component completely or partially loses its light-absorbing ability.

Light-absorbing components are known to be colored components such as dyes and pigments. It is also known that light absorbing components do not include white or black components such as: titanium dioxide, chalk, barium sulfide, carbon black or iron sulfide.

Most importantly, the light-absorbing component does not lose or hardly loses its light-absorbing ability under normal sunlight. To this end, the light-absorbing component should have a color stability, measured on the Woolscale (according to DIN 54003), of at least 5, more preferably of at least 7, and still more preferably of 7 or more.

Examples of suitable light absorbing components are ^Irgalith® Rubine 4 BP, a magenta coloring pigment; Irgalith Blue LGLD, a cyan coloring 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 capacity by means of laser radiation.

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

Irradiation with a laser of a specific wavelength reduces the light-absorbing capacity of the preselected light-absorbing component: the surface at the site of the irradiation will reflect the color that can no longer be absorbed by the component in question. The brightness of the reflected color can be increased by increasing the intensity of the laser or prolonging the irradiation time.

Markings of the desired color can be formed by applying a number of matrix dots on the surface.

It is also possible to apply matrix dots of different colors side by side to the surface. For the observer, the surface color at the position of the matrix point is a color mixture, because the color of the matrix point is projected to the naked eye through the color mixture. This color mixing method of arranging the colors to be mixed side by side is called a partial method. Color mixing is determined by the surface area ratio of the matrix points and the color brightness ratio. In this way, many mixed colors can be formed.

The most important thing in this paper is that the center-to-center distance between the matrix points is so small that the naked eye cannot distinguish a single matrix point. News pictures are also colored in this way.

As is known from color printing, good results are obtained by applying matrix dots of at least three different colors to the surface. This can be achieved by irradiating the surface with laser light of at least three different wavelengths, during which process one of the at least three light-absorbing components completely or partially loses its light-absorbing ability at each wavelength. In this way, the use of at least three colors enables the formation of many other colors by mixing appropriate amounts of colors.

Color mixing can be done in many ways. Color mixing is accomplished, for example, by varying the color brightness of the matrix points relative to one another, eg by radiating matrix points of a particular color that are longer than other matrix points. In addition, it is also possible to change the total area ratio of different colors to each other by, for example, preparing a matrix dot larger than other matrix dots, or forming a matrix of one color with more matrix dots than other colors point. The matrix points can be circular or square, but also, for example, triangular or linear, for example to better fill the surface or to increase the total reflection of the surface.

The color is characterized in that, according to ASTM standard E 308, the tristimulus values (tristimulus values) of the color are first determined, and then as described in the above standard, the chromaticity coordinates are calculated to determine the position of the color in the CIE D65 color map. position (10° observer). As such, a colormap is a representation of all colors in the visible range.

The distributive mixing technique can form a color that is located in the region between at least three differently colored points in the color map that represent matrix points in the color map. These points form the peaks of the region.

The method of the present invention to obtain more different colors consists in applying matrix dots in full or partial overlap. This color mixing technique is called subtractive color mixing.

Preferably, the surface color is determined by subtractive mixing of at least three differently colored matrix points. The range of colors emanating from subtractive color mixing is greater than in the case of distributive mixing, since the resulting colors lie outside the region in the color map between points of at least three different colors representing matrix points in the color map.

The plastics composition can in principle contain any thermosetting or thermoplastic plastics or elastomers. The plastics that can be contained in the plastics compositions described in WO 94/12352 are particularly suitable.

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

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

The wavelength of the laser light at which the surface is irradiated in order to cause the predetermined light-absorbing component to lose its light-absorbing capacity can easily be determined experimentally.

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

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 not transmissive in non-irradiated surface locations. The continuous irradiation of the surface with different masks and different wavelengths of laser light enables the application of matrix dots of different colors to the surface quickly and easily.

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, thus, the surface can be irradiated with a large diameter laser beam. As a result, the radiation time is shorter.

Preferably the method of the invention is carried out 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, with the added advantage that it does not absorb, but scatters the non-transmitted laser beam, so that the mask does not heat up.

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

If the method of implementing the present invention is to simultaneously irradiate the object surface with a laser device by means of at least three masks positioned adjacent to each other, the lasers of different wavelengths project the mask images onto the object surface one after the other to the mask radiation. That will get good results. The advantage is that the object surface is irradiated with different masks in one operation. If the mask is variable in this process, an additional advantage is that different markings can be applied in quick succession. The same mechanism can be seen from the image projection.

The method can also be carried out with a controllable laser beam of variable intensity. With regard to the shape and color intensity of the object to be irradiated, this method of implementation offers greater flexibility.

In addition, a laser device having a tunable wavelength is also most desirable, since it is possible to irradiate the surface with lasers of different wavelengths with 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. This enables all possible colors to be formed with a single laser.

More preferably, a laser device that combines at least three laser beams of different wavelengths in one fiber, which can vary the intensity of each beam independently of other beams, is used. This has the advantage that the surface of the object can be irradiated easily with one composite laser beam which emits all colors. The result is a high degree of flexibility as far as the number of colors that can be selected and the shape of the marks applied.

Example 1

Dry blends were prepared from the following raw materials: 1897 parts by weight of ^Ronfalin® SFA-34, an acrylonitrile-butadiene-styrene copolymer (ABS) from DSM (Netherlands); 100 parts by weight of Tiofine® ^R41 , The titanium dioxide pigment that Tiofine Company (Netherlands) produces; And 1 weight part Iraglith ^® Rubine 4BP, 1 weight part Irgalith BlueLGLD and 1 weight part Cromopthal ^® Yellow 6G, each is respectively the magenta, cyan and color that Messrs Ciba Geigy Company (Netherlands) produces successively. Yellow coloring pigment.

The dry blend was kneaded and pelletized at 260° C. in a ^ZSK® 30 twin-screw extruder from the company Weiner and Pfleiderer (Germany). The pellets were injection molded in an Arburg ^Allrounder® 320-90-750 injection molding machine at 240° C. into tablets of 3.2 x 120 x 120 mm. In-chip coloring pigments absorb visible light. The flakes are light gray.

The marking is then applied to the surface by means of a laser device. A tunable wavelength laser device (TMW laser device) is used. The laser unit is equipped with a seeding laser of the type EEO® ^- 355, which is used as a laser pump for a Nd ^: YAG laser of the type GCR®-230/50. In addition, the laser unit is equipped with an optical parametric oscillator (OPO) of the type ^MOPO® 710, which receives the signal from the laser described below by means of frequency doubling optics (FDO). This device is produced by Spercra-Physics Company of the United States.

The laser setting options are as follows:

Pulse Width: 5 ns

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

Spot diameter: 3mm

Recording speed: 10 mm/s

Line spacing: 0.66mm

Focal length: +80mm

Colored light is applied to the sample by means of the laser device described below using the method described below. With the help of "Corel-photoprint 5.0 for Hewlett Packard" of Corel Corporation of the United States, the colored light is subdivided into "red mask", "green mask" and "blue mask" (selection: fractional channel RGB). These black/white masks were printed on transparent objects using a "Spectra Star ^™ GTx" color printer from Messrs General Parametric, USA. For precise positioning, a cross is set around the image.

Subsequently, a "blue mask" was placed on the above sheet and irradiated with a laser light having a wavelength of 450 nm. Next, remove the mask and replace it with a "green mask", and precisely position it on the image obtained by the "blue mask". This "green mask" is irradiated with laser light having a wavelength of 530 nanometers. Finally, a "red mask" is placed and irradiated with a laser with a wavelength of 650 nanometers. When this final irradiation is complete, an indelibly colored light is obtained on the plastic with a color range comparable to the original color range.

Example 2

A paint consisting of 65.0 parts by weight of Uracron® 474CY, a hydroxy- ^functional resin available from DSM Resins (Netherlands); 20.8 parts by weight of ^Tolonate® HDT EV 412, Huls 0.6 parts by weight of dibutyltin dilaurate (dibutylindilaureate), produced by Aldrich Company (Belgium); 10 parts by weight of Kronos® CL220 ^, 1.2 parts by weight of Cromoptal® ^Yellow 3G, a kind of product produced by Ciba Geigy Company (Netherlands) Yellow pigment; 1.2 parts by weight of Paliogen® Red L 3910HD, a red pigment from the company BASF (Netherlands) and ^1.2 parts by weight of Orasol® Blue ^GN , a blue colorant from the company Ciba Geigy (Netherlands). The lacquer was applied to the aluminum sheet at a film thickness of 50 microns. The paint film is gray. Paint film markers were made as described in Example 1 above.

The laser settings for this experiment are:

Pulse Width: 5 ns

Conversion circuit quality factor Frequency: 30 Hz

Spot diameter: 3mm

Recording speed: 25mm

Line spacing: 0.66mm

Focal length: +40mm

Claims (11)

1. Method for producing an object with colored markings by irradiating the surface of the object with a laser; characterized in that the object consists of a plastic composition containing at least three light-absorbing components, at least at the locations where the markings are applied; these light-absorbing components are in different It has a maximum value in its absorption spectrum under the wavelength and loses its light-absorbing ability under the action of laser light; the mark is applied in the form of matrix points, and the wavelength, intensity and irradiation time should be such that at least one light-absorbing component is completely or The laser light, which has partially lost its light-absorbing ability, irradiates the surface of the object at the position of the matrix point. 2. A method according to claim 1, characterized in that the surface color is formed by subtractive color mixing of at least three differently colored matrix points. 3. 2. A method according to claim 1, characterized in that the surface color is formed by distributive mixing of matrix point colors. 4. A method according to any one of claims 1, 2 or 3, characterized in that the light-absorbing components are selected in such a way that the area between points of at least three different colors representing matrix points in the color map covers At least 10% of the figure area. 5. 4. A method according to any one of claims 1 to 4, characterized in that the surface is irradiated at a laser wavelength at which maxima occur in the absorption spectra of the different light-absorbing components. 6. 5. A method according to any one of claims 1 to 5, characterized in that the method according to the invention is carried out by means of one or more masks. 7. 6. A method according to any one of claims 1 to 6, characterized in that the method according to the invention is carried out by means of a variable mask. 8. 6. A method according to claim 6, characterized in that the mask is made of an LCD panel. 9. 6. A 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 to 9, characterized in that the surface is irradiated by a laser device which simultaneously irradiates the surface of the object by means of at least three masks positioned adjacent to each other, the lasers of different wavelengths irradiating the mask Radiation is performed in such a way that the images of the masks are projected one after the other onto the surface of the object. 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 other beams.