EP4006228A1

EP4006228A1 - Method for laser marking textiles

Info

Publication number: EP4006228A1
Application number: EP20383034.4A
Authority: EP
Inventors: Enrique Silla Vidal; Fernando CARDONA FORTEA
Original assignee: Jeanologia SL
Current assignee: Jeanologia SL
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2022-06-01

Abstract

A method for improving laser marking on a textile, the method comprising applying an acid on a textile, and subsequently marking by means of laser radiation a feature on the textile, the acid being a carboxylic acid that preferably has six or less carbon atoms and/or has a molar mass that is equal to or less than 200 g/mol. Moreover, use of citric acid on a textile for improving the appearance of a subsequently induced by means of laser radiation feature on the textile.

Description

TECHNICAL FIELD

The present invention relates to the field of laser marking on textiles. It concerns a method for improving laser finishing of textiles, such as for improving laser marking features on textiles. Improving laser marking may refer to improving the speed of the laser marking, and/or allowing for reducing the laser power required for marking, and/or improving the quality of a marked feature, and/or making a laser marked feature to appear "lifelike", i.e. non-artificial, on the fabric. Therefore, it can be said that improving laser marking may be rendering lifelike a laser marked feature on a textile, i.e. causing that a laser marked feature when is created on a textile appears lifelike. The textile may be a fabric, preferably a garment. Likewise, the textile may be denim or comprise denim.

BACKGROUND

The textile industry has benefited greatly by the use of laser finishing technology. Laser radiation can be used for creating various finishing effects and/or features on fabrics, garments, textiles and the like. Accordingly, related to improving the laser marking, particularly the marking of features, graphics, patterns and the like on fabrics, the prior art mostly describes controlling some factors related to the laser beam, e.g. the laser's energy, and/or the laser beam's motion. For example, patent application document EP3346038 A1 concerns changing the laser power for laser marking, and describes a method starting with a digital image, in which each pixel of the image has a pixel value, and in the method, for each pixel a laser burns in said clothing a point corresponding to said pixel, with a laser energy level which is a function of said pixel value, wherein said function has two regions with two gradients of different absolute values, and wherein the two regions correspond to different laser energy values.
An alternative approach related to improving laser marking, concerns creating yarns that are specifically configured for laser marking, and manufacturing corresponding fabrics. Patent application document WO 2020202195 A1 describes a method for manufacturing a laser friendly denim fabric, the method including making a yam, passing said yarn through a dye solution for obtaining a dyed yam, sizing said dyed yarn, and weaving a fabric.
In view of the prior-art, it is considered that a pending problem is how to improve the laser marking on fabrics, including on fabrics that are not necessarily laser friendly fabrics, and do so without necessarily requiring the improvement of the existing systems and apparatuses that are currently used for laser marking and finishing of fabrics.

SUMMARY OF THE INVENTION

A particular application of laser technology is found in the denim industry, wherein wear patterns and decorative features such as holes and tears, as well as any kind of graphics, can be created on denim using a laser beam that is scanned on/across a surface of the garment. The laser beam may decolor, burn, create holes or cause a visible physicochemical change on the surface of the garment. The effects created by a laser beam on each point of the fabric may crucially depend on the energy conveyed by the laser on said point of the surface. Advantageously, said energy is controlled so that the laser beam may create a different effect, such as different level of discoloration, on different points of the fabric, when for example it is required to laser scribe a graphic on the denim, wherein the graphic comprises different pixels of different color values.
Each of said different color values may be transferred as correspondingly different discoloration levels on the fabric surface's different points that correspond to the different pixels. The energy conveyed by the laser on each point of the surface may depend on various factors related to the laser beam and/or the laser beam's motion, such as the power density of the beam, the wavelength of the laser beam, and the speed with which the beam may move/scan over said point.
An object of the present invention is providing a method for improving laser marking of fabrics. The method does not require the use of laser friendly fabrics and yarns, nor necessarily requires the advancement of the laser marking systems that are currently used in the textile industry. Accordingly, an object of the present invention is providing a method that allows for reducing the laser power required for laser marking. Likewise, an object of the present invention is providing a method that allows for improving the speed with which features can be marked on a fabric using laser, wherein said method is compatible and readily applicable in combination with existing laser systems for the textile industry.
Accordingly, the present invention in its first aspect concerns a method for improving laser marking on a textile, the method comprising applying an acid, said acid being a carboxylic acid, on a textile, and subsequently marking by means of laser radiation a feature on the textile. Preferably the carboxylic acid is a short chain carboxylic acid that has less than seven carbon atoms and/or that has a molar mass that is equal to or less than 200 g/mol. Accordingly, the carboxylic acid may be have ≤6 carbon atoms and/or a molar mass that is ≤200 g/mol. Surprisingly, the application of a carboxylic acid, particularly of a short chain carboxylic acid, prior to the marking of the feature on fabric, improves the responsivity of the fabric to the laser. It is contemplated that the small size of short chain carboxylic acids improves the penetration of the acid in the fabric's yarns and fibers, resulting to a laser marking enhancement. The use of carboxylic acids, particularly the use of short chain carboxylic acids, renders the method cost effective, scalable and compatible with other existing processes for processing fabrics. In the context of the present invention, the responsivity of the fabric to the laser may be understood as any of the following and combinations thereof:

i) The laser energy threshold required for the fabric being marked or decolored or burned; improving the responsivity may be decreasing said threshold.
ii) A linear or other type of relationship between a degree of a laser radiation induced change on the fabric, and a parameter controlled for marking with the laser radiation; said parameter may be related to the power or energy of the laser radiation used for marking the substrate, or may be related to the scanning and motion of the laser radiation if said laser radiation is scanned over the surface as part of the laser marking; improving the responsivity may be altering or affecting said linear or other type of relationship, such as increasing a laser energy range across which said relationship holds true, or altering numerical parameters related to said relationship.

Advantageously, said carboxylic acid may be citric acid. The use of citric acid may allow for obtaining an optimized laser marking improvement effect, as well as for rendering said effect long lasting. When the improvement effect is long lasting then said effect may be attainable even in the optional case that the time duration between applying the acid on the fabric and laser marking a feature is one or more days. Of course said period may be one or more minutes, or hours, or weeks or months. Preferably, said period is less than 15 days for avoiding damaging the fabric, but a longer period is also contemplated. Accordingly, preferably marking the feature is being executed less than 30 days, and preferably less than 10 or 5 days, and more preferably the same or next day as of a day on which executing applying the acid.
Applying the acid may be applying a solution that preferably is aqueous and comprises the acid. The use of water as a solvent for the acid, may facilitate scaling up the method, rendering the latter readily available for widespread industrial application. Accordingly, it is contemplated the optional case that said solution that comprises the acid may not comprise dissolved or dispersed or added in the solvent another additive other than said acid. Said another additive may be an organic or inorganic salt, or an organic or inorganic base. Said another additive may be dangerous for the environment, or increase the cost of the method, or be complicate to use and combine with the acid. Accordingly, the solution may consist of water and the acid. While several liquid based textile treatment methods rely on the use of solutions that contain one or more additives and substances purposely dissolved in the solution, the method of the invention works exceptionally well in the optional and preferable case that the solution consists of water and the acid.
The method may be applied for laser marking on large fabric surfaces, and/or for laser marking of fabrics, e.g. garments, processed in batches. Therefore, advantageously the acid may be applied in a step that permits reliably, and preferably homogenously, applying the acid over a large fabric surface, e.g. over a surface of a garment, and/or applying acid simultaneously on several different fabrics. Accordingly, in a method according to the first aspect of the invention wherein there is the aforementioned optional feature that there is a solution comprising the acid, preferably applying the acid on the textile may comprise any of: spraying onto the textile the solution that comprises the acid; wetting the textile with said solution; immersing the textile in said solution. Likewise, preferably the concentration of the acid in the solution is of between 10 g/L and 500 g/L, and more preferably of between 50 g/L and 200 g/L, because said concentration ranges allow for simultaneously optimizing the laser marking improvement, shortening the duration of the step of applying the acid on the fabric, and avoiding that the acid detrimentally damages the fabric in an undesired and aesthetically displeasing way.
Advantageously the method of the present invention allows for quick processing of the textile. For quick processing it may be necessary to dry the fabric. In a preferred embodiment, the textile is dried after applying the acid and before marking with the laser. In contrast to the prior art where some chemical agents applied on the garment may not be quickly dried at elevated temperatures, because said temperatures may cause undesired physicochemical changes on the chemical agents or the garments bearing them, in the present method drying may be applied thusly achieving advantageous effects. Accordingly, preferably in between applying the acid and (laser) marking the feature, the method may further comprise drying the textile. More preferably, drying the textile is done at a temperature of more than 40°C, and preferably of more than 50°C or 70°C. When the temperature is higher than 40°C or 50°C or 70°C then quick and efficient drying and processing of the fabric are achieved.
As mentioned, in the method according to the first aspect of the invention preferably the textile comprises denim. Indeed, the method works exceptionally well for denim. The laser marking of denim may be improved if the denim has been previously treated with acid. The laser marking improvements may be very pronounced if the denim is black or of dark color. Accordingly, optionally and preferably in the method of the first aspect of the invention the textile has a black or dark color. Likewise, the laser marking improvements may be more noticeable if the textile/fabric is dyed and some discoloration or a similar effect is being induced in said textile/fabric before or after the textile/fabric is marked using the laser. Accordingly, in the method optionally and preferably the fabric is dyed and the method comprises washing and/or bleaching or and/or decoloring or and/or abrading and/or softening and/or functionalizing the fabric.
From the above it can be understood that in the method of the first aspect of the invention preferably improving laser marking on a textile is improving the appearance of a laser induced feature on a textile. Likewise, preferably said (laser induced) feature comprises a graphic or wear pattern or damage or a hole or a combination thereof. Said feature may be formed by the laser radiation scribing or burning the surface of the textile/fabric. Likewise, the laser radiation may remove and/or burn material from the surface of the textile, thusly creating said feature on the textile. Accordingly, optionally marking the feature on the textile comprises burning through the textile.
As mentioned, the feature marked on the textile may be a graphic image. Said image may be created or provided in a digital form, and may be a vector graphic or may comprise pixels, and each pixel may have a corresponding value that may correspond to a color scale. An example of a color scale is a grayscale from 0 to 255. Such an image may be transferred on the textile by scanning the laser radiation across different parts of the textile, wherein each part corresponds to a pixel. Each part has a corresponding area value, and preferably the area value of each part is the same. The color of each part may be modified by the laser radiation according to the corresponding value of the pixel that corresponds to said part. Such modification may be done by adjusting and controlling the amount of energy of the laser radiation that hits the corresponding part on the textile surface. Said amount of energy can be adjusted according to said values of the pixels. Said amount of energy may be adjusted by means of adjusting the speed of scanning the laser radiation, and/or by adjusting the energy density per unit time per unit area of the laser radiation that hits the textile. Accordingly, it is contemplated that in the method according to the first aspect of the invention, preferably marking the feature on the textile comprises: applying the laser radiation on a surface of the textile; scanning the laser radiation on the surface, thereby applying the laser radiation on different parts of the surface, and preferably during scanning altering a value of an energy per unit time per unit area of said laser radiation being applied on said surface.
A second aspect of the invention concerns the use of carboxylic acid, particularly short chain carboxylic acid, for improving laser marking of the textile. Accordingly, the invention in its second aspect preferably concerns the use of citric acid on a textile for improving the appearance of a subsequently induced by means of laser radiation feature on the textile. It is preferable to use citric acid because the latter gives astonishing results in terms of the achievable laser marking improvements.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows a flow diagram of a method according to the first aspect of the invention
Fig. 2 shows two pieces (one on the right and one on the left) of black denim with the same features marked on each piece by means of laser radiation under the same laser marking conditions, with the difference being that before the application of the laser radiation the piece on the right was treated with citric acid, whereas the piece on the left was not treated with the acid.

DETAILED DESCRIPTION OF DRAWINGS.

Fig. 1 shows a flow diagram of an embodiment of the method according to the first aspect of the invention, wherein in step 1001 acid is applied on a textile, and in step 1002 a feature is marked on a textile's surface by means of laser radiation. The feature is preferably a graphic that is provided to a laser marking system as a digital file. Preferably the laser marking system scans a laser beam (the laser radiation) over the textile's surface controlling the speed and/or energy density per unit time per unit area of said beam as a function a value that corresponds to each pixel of the graphic. Preferably and optionally the textile is a denim fabric or a denim garment. More preferably the denim is dyed with indigo. Moreover, preferably the denim comprises sulfur. Denims that comprise sulfur because have been produced using a yarn that has been dyed using a process that comprises the use of a sulfur containing compound, often appear dark colored. Preferably in step 1001 the acid is citric acid that is a short chain carboxylic acid, and is applied on the textile by spraying. In an embodiment, citric acid dissolved in water at a concentration of 100 g/L is being sprayed on the textile at a flow rate of 8 L/h (liters per hour), until the surface of the textile is uniformly treated with the spray. Said spraying may be done with the textile being processed within a rotating drum. Subsequently, before the laser marking, preferably the textile is dried at 70°C in a dryer.
The laser marking in step 1002 may be done using any laser, and for example using a CO₂ laser of a Flexi Pro laser marking system fabricated by the applicant, wherein the laser wavelength is 10.6 micrometers and the laser power was set to be 400 watts. An example of the laser marking improvement that is achieved by the method of the present invention is shown in Fig. 2. The black denim on the left in Fig. 2 has not been treated with citric acid (or other carboxylic acid) before the laser marking. In contrast, the denim on the right in Fig. 2 has been treated with citric acid. The same laser marking step, using the same original graphic, was applied on each piece of denim of Fig. 2, and as can be seen the graphic created on the right piece of denim is more vivid, clear, lifelike looking and aesthetically pleasing compared to the corresponding graphic created on the left piece of denim.
Although specific terms are used in the previous description for the sake of clarity, these terms have been presented for the purposes of illustration and description of the invention. It is not intended to be exhaustive or limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use.

Claims

A method for improving laser marking on a textile, the method comprising applying an acid on a textile, and subsequently marking by means of laser radiation a feature on the textile, the acid being a carboxylic acid that preferably has six or less carbon atoms and/or has a molar mass that is equal to or less than 200 g/mol.
A method according to claim 1, wherein applying the acid is applying a solution that preferably is aqueous and comprises the acid.
A method according to claim 2, wherein the solution consists of water and the acid.
A method according to any of claims 2-3, wherein applying the acid on the textile comprises any of: spraying onto the textile the solution that comprises the acid; wetting the textile with said solution; immersing the textile in said solution.
A method according to any of claims 2-4, wherein the concentration of the acid in the solution is of between 10 g/L and 500 g/L, and preferably of between 50 g/L and 200 g/L.
A method according to any of claims 1-5, wherein marking the feature is being executed less than 30 days, and preferably less than 10 or 5 days, and more preferably the same or next day as of a day on which executing applying the acid.
A method according to any of claims 1-6 wherein, preferably in between applying the acid and marking the feature, the method further comprises drying the textile.
A method according to claim 7, wherein drying the textile is done at a temperature of more than 40°C, and preferably of more than 50°C or 70°C.
A method according to any of the preceding claims, wherein the textile comprises denim.
A method according to any of the preceding claims, wherein the textile has a black or dark color.
A method according to any of the preceding claims, wherein the fabric is dyed and the method comprises washing or bleaching or decoloring or abrading the fabric.
A method according to any of the preceding claims, wherein improving laser marking on a textile is improving the appearance of a laser induced feature on a textile, and preferably the feature comprises a graphic or a wear pattern or a damage or a hole or a combination thereof.
A method according to any of the preceding claims, wherein marking the feature on the textile comprises burning through the textile.
A method according to any of the preceding claims, wherein marking the feature on the textile comprises: applying the laser radiation on a surface of the textile; scanning the laser radiation on the surface, thereby applying the laser radiation on different parts of the surface, and preferably during scanning altering a value of an energy per unit time per unit area of said laser radiation being applied on said surface.
Use of citric acid on a textile for improving the appearance of a subsequently induced by means of laser radiation feature on the textile.