1. A printing method for generating local thick texture of a metal flat plate for packaging is characterized by comprising the following steps:

(1) after the surface of the metal flat plate is coated with the base coat, the base coat is formed by curing, then the image-text printing ink is printed and then the printing ink is cured to form the printing ink layer, and then the gloss oil is coated and then the printing ink layer is cured to form the gloss oil layer;

(2) printing gloss oil on the part of the surface of the gloss oil layer needing to generate thick texture by adopting a lithographic offset printing method, and curing and drying to form an external gloss oil layer;

(3) and (3) screen-printing thick film gloss oil on the surface of the external gloss oil layer, and then curing and drying to form the thick film gloss oil layer.

2. The printing method for generating the local thick texture of the metal flat plate for the package as claimed in claim 1, wherein the gloss oil coated on the gloss oil layer in the step (1) is polyester resin, acrylic resin or epoxy resin, the solid content is 30-50 wt%, the weight of the construction dry film is 5-8 g/square meter, and the metal flat plate is baked at the temperature of 150-180 ℃ for 10-12 minutes to be cured.

3. The printing method for producing local thick texture on the metal flat plate for packaging as claimed in claim 1, wherein the gloss oil used in step (2) comprises polyester acrylate, UV photoinitiator, pigment and auxiliary agent, and the solid content is 90-100 wt%, wherein the polyester acrylate is 50-70 wt%, the UV photoinitiator is 8-10 wt%, the pigment is 18-25 wt%, and the auxiliary agent is 2-5 wt%.

4. A printing method for creating a local thickness feeling in a flat metal sheet for packaging as set forth in claim 3, wherein the surface tension of the external gloss oil layer is 36 to 42 dyn/cm.

5. The printing method for producing local thick texture on the metal flat plate for packaging as claimed in claim 1, 3 or 4, wherein the curing in the step (2) is LED-UV light curing, and the light source intensity is not less than 8W/cm²The value of the absorption energy of the printing surface is more than or equal to 300mj/cm²。

6. The printing method for creating the local thick texture on the flat metal plate for packaging as claimed in claim 1, wherein the printing plate used in the offset printing in the step (2) is a local image-text enlarging printing plate for making the image-text edge size of the part to be created thick texture by an AI document.

7. A printing method for generating local thick texture on a metal flat plate for packaging as claimed in claim 6, wherein the outward expansion size of the image-text edge is not less than the overprinting error of the ink layer, the external gloss oil layer and the thick film gloss oil layer corresponding to the part needing to generate thick texture.

8. A printing method for producing a partial thick texture on a metal flat plate for packaging as claimed in claim 1, wherein the main components of the gloss oil used for the thick film gloss oil layer are polyester resin or acrylate resin, and the photoinitiator has a solid content of 90 to 100wt%, and a UV photoinitiator content of 5 to 10 wt%.

9. The printing method for producing a local thickness feeling on a flat metal sheet for packaging according to claim 1, wherein the thick film is screen-printed using a thick film having a mesh number of 70 to 150 meshes/inch.

10. A printing method for giving a local thick feeling to a flat metal sheet for packaging as claimed in claim 1, wherein the surface hardness of the glossy oil layer, the external glossy oil layer and the thick film glossy oil layer is not less than 2H pencil hardness.

Background

Offset lithographic printing is the most widely used printing process for packaging metal plates: firstly, forming a base coat on the surface of a metal flat plate by adopting a rubber roll for roll coating, then printing pictures and texts by adopting a lithographic offset printing method, then coating a glossy oil layer on the surface of the metal flat plate subjected to picture and text printing by using a cylindrical rubber roller or a polyurethane roller in a roll coating mode for covering, and realizing the protection and personalized appearance effect on the surface of a printed matter by using a glazing process. However, the existing offset lithography process cannot bring the thick texture of metal offset lithography pictures and texts, mainly because the offset lithography pictures and texts and the gloss oil layer are both in a plane effect, the printing effects of the regular raised thick texture and the visual effect of the specific area boundary cannot be realized, and the form is monotonous and has certain limitation.

Chinese patent ZL2010296386.7, the name of the invention "Mixed printing method of metal plate" discloses a method for printing on metal plates such as tinplate, aluminum sheet and the like by adopting metal oily ink and ultraviolet curing ink. The personalization of the product is realized by matching the metallic ink and the ultraviolet curing ink, and the material is saved. However, the preparation process is still the traditional prime coat-offset lithography-brightening method in practice, and the local thick feeling of the metal flat plate cannot be realized.

Disclosure of Invention

The invention aims to provide a printing method for generating local thick texture on a metal flat plate for packaging, aiming at the problem that the traditional printing process of the metal flat plate for packaging is difficult to bring thick texture, and the local thick texture of a specific part can be printed on the metal flat plate for packaging.

The invention provides the following technical scheme:

a printing method for generating local thick texture of a metal flat plate for packaging comprises the following steps:

(1) after the surface of the metal flat plate is coated with the base coat, the base coat is formed by curing, then the image-text printing ink is printed and then the printing ink is cured to form the printing ink layer, and then the gloss oil is coated and then the printing ink layer is cured to form the gloss oil layer;

(2) printing gloss oil on the part of the surface of the gloss oil layer needing to generate thick texture by adopting a lithographic offset printing method, and curing and drying to form an external gloss oil layer;

(3) and (3) screen-printing thick film gloss oil on the surface of the external gloss oil layer, and then curing and drying to form the thick film gloss oil layer.

In the prior art, individuation of a metal lithographic plate is mainly represented by exaggerated color, various color plates and the like, and the individualized effect expression is increased by utilizing a bright effect, and the fact that a three-dimensional effect is formed by local image-text protrusions is rarely considered, so that the experience of thick texture in touch and vision is brought. The reason for this is that it is difficult to produce a thick feel in the prior art, while it is cost effective. Because the ink layer thickness of the offset lithography pattern and text is thin in the current printing process, the locally obvious concave-convex hand feeling can not be realized through ink accumulation in consideration of the process and the cost; the roller coating of the rubber roller realizes full-page coating, and the coating accumulation of a local regular pattern area cannot be realized by the roller coating method of the rubber roller; although the silk-screen printing can realize the accumulation of an ink layer thicker than that of the offset lithography, the metal lithography uses more types of surface gloss oil according to the product requirements and has larger surface characteristic difference, so that the adhesion force of the silk-screen thick film gloss oil on the surface is unstable, the contact edge is easy to shrink by saw teeth, and the silk-screen thick film gloss oil is easy to fall off in the subsequent processing link; meanwhile, the method is limited by the smooth and fine surface of the metal flat plate, and the printing effect brought by the operation is poor. In order to bring obvious unsmooth hand feeling of local picture and text, the inventor is studied, develop a new way on the basis of the existing metal lithographic printing process, break and directly utilize offset printing picture and text printing ink to pile up the thinking that produces thick feel, need to produce the local special preparation printing plate of thick feel on the surface of the gloss oil reservoir, utilize offset printing to form the external gloss oil reservoir, then utilize screen printing to pile up the printing ink reservoir and obtain thick film gloss oil reservoir, thereby combine together local offset printing and screen printing and realize local picture and text arch, produce three-dimensional effect, bring unsmooth hand feeling, the good cohesiveness of the thick film gloss oil reservoir of screen printing to the metal flat plate has been guaranteed simultaneously, avoid thick film gloss oil reservoir edge sawtooth shrink to appear.

Preferably, the gloss oil coated on the gloss oil layer in the step (1) is polyester resin, acrylic resin or epoxy resin, the solid content is 30-50 wt%, the weight of a construction dry film is 5-8 g per square meter, and the metal plate is baked at the temperature of 150-180 ℃ for 10-12 minutes to be cured. The glossy oil layer mainly plays a role in protecting the offset lithography pictures and texts, and the appearance effect can be glossy, pearly-lustre, matte and the like, so that the product has good layout effect and processing resistance.

Preferably, the gloss oil used in the step (2) mainly comprises polyester acrylate, a UV photoinitiator, a pigment and an auxiliary agent, and the solid content is 90-100 wt%, wherein the polyester acrylate accounts for 50-70 wt%, the UV photoinitiator accounts for 8-10 wt%, the pigment accounts for 18-25 wt%, and the auxiliary agent accounts for 2-5 wt%. The external gloss oil layer is more suitable for selecting LED-UV semi-matte oil, can form obvious difference with the thick film gloss oil layer, enhances the thick texture, and controls the printing ink amount between 0.3CC and 0.6 CC.

Preferably, the curing in the step (2) is LED-UV illumination curing, and the light source intensity is more than or equal to 8W/cm²The value of the absorption energy of the printing surface is more than or equal to 300mj/cm². The method has important influence on ensuring the adhesive force between the glossy oil layer and the external glossy oil layer and between the thick film glossy oil layers.

Preferably, the curing in the step (2) is LED-UV illumination curing, and the light source intensity is more than or equal to 8W/cm²The value of the absorption energy of the printing surface is more than or equal to 300mj/cm². The external gloss oil layer is convenient to quickly solidify, good interlayer binding force is formed among the gloss oil layer, the external gloss oil layer and the thick film gloss oil layer on the surface of the product, the adhesive force among the layers is more than or equal to II level, and the basic characteristics and the appearance effect of the original protective gloss oil on the surface of the product are reserved.

Preferably, the printing plate used in the offset lithography in the step (2) is a local image-text enlarged printing plate which is used for making the image-text edge size of the part needing to generate thick texture by an AI document. The shape and the size of the image and the text of the local silk-screen thick film gloss oil layer can be consistent with the shape and the size of the offset color printing image and text of the corresponding position on the surface of the metal plate, so that the local concave-convex effect is clearer.

Preferably, the outer expansion size of the image-text edge is not less than the overprinting error of the image-text of the ink layer, the outer gloss oil layer and the thick film gloss oil layer. The adhesive force of the silk-screen thick film gloss oil layer on the surface of a product is increased conveniently, the thick film gloss oil layer is prevented from cracking and falling off in the subsequent processing link, and the clear boundary of the local image-text part is ensured. The overprinting error is generally controlled to be less than or equal to 0.2mm, so the outward expansion size of the image-text edge is more than or equal to 0.2 mm.

Preferably, the gloss oil used for the thick film gloss oil layer comprises polyester resin or acrylate resin as main components and a photoinitiator, wherein the solid content is 90-100 wt%, and the UV photoinitiator content is 5-10 wt%. The thick film gloss oil used in the invention is UV gloss oil, the curing speed of the UV gloss oil is high, the printing efficiency can be improved, and meanwhile, the surface of the silk-screen thick film gloss oil can be subjected to special treatment such as gold stamping, laser and the like according to the requirement.

Preferably, the method of the present invention is performed by thick film screen printing with a mesh size of 70 to 150 meshes/inch. The mesh number of the silk screen affects the thickness of the thick film gloss oil layer, local convex hand feeling can be formed after curing, and good binding force is mainly formed between the silk screen and the external gloss oil layer. The method of the invention can realize that the thickness of the thick film gloss oil layer is at least 30 mu m to present obvious concave-convex feeling, of course, the thickness of the thick film gloss oil layer is not as high as possible, and the upper limit height is lower than 500 mu m.

Preferably, the surface hardness of the glossy oil layer, the external glossy oil layer and the thick film glossy oil layer is not less than 2H pencil hardness. The bonding force and the strength of the three are ensured, and the damage of thick texture brought by subsequent processing is avoided.

The invention has the following beneficial effects:

the invention provides a method for generating local thick texture on the surface of a metal flat plate for packaging, which can realize that the metal flat plate printing plate has plane hand feeling and local concave-convex hand feeling; the thick film gloss oil layer and the image-text ink layer at the bottom are coincided and responded, the edges of local images and texts are clear, and the image-text ink layer has concave-convex thick texture; the original base coat and protective gloss oil are used according to the characteristics of the product, so that the quality foundation and appearance style of the substrate of the metal packaging product are kept; the traditional metal packaging offset printing and silk screen printing missing process is compatible, the bottom layer protective gloss oil layer and the silk screen thick film gloss oil layer are well connected, and the requirement of the subsequent basic processing is met; the offset printing outer oil layer and the silk-screen thick film gloss oil layer respectively adopt LED-UV and UV photocuring processes, are more energy-saving and environment-friendly than the traditional thermal baking curing process, have high printing efficiency, and simultaneously reduce yellowing of the bottom color of a product and influence of baking furnace ash pollution on the appearance of a layout.

Drawings

FIG. 1 is a graph showing the effect of an automobile rust remover sample can made of a metal flat plate printed in example 1.

Detailed Description

The following further describes the embodiments of the present invention.

The starting materials used in the present invention are commercially available or commonly used in the art, unless otherwise specified, and the methods in the following examples are conventional in the art, unless otherwise specified.

The following description will be made by taking a metal plate for a rust remover sample tank of an automobile manufactured by Hangzhou ZhongLiang Meite Container Co.

Example 1

A printing method for generating local thick texture of a metal flat plate for packaging comprises the following steps:

(1) coating a base coat on the surface of a metal flat plate, curing to form the base coat, printing image-text ink, curing to form an ink layer, coating gloss oil, and curing to form a gloss oil layer, wherein the specific steps are as follows:

coating a base coat: coating and priming by using a roll coating mode of vertically reserving an empty rubber roller on the whole plate surface, wherein the used ink is an MC-UV-C504 white Keding product which is produced by the chemical company Limited in the Conn Ling of Fushan City and has the solid content of 65 +/-2 percent (m/m), and the dry film is dried by a heating and curing mode of 180 ℃/12 minutes, and the weight of the coated dry film is 13 g/square meter;

printing image-text ink: one or more printing is carried out according to different layouts to form a printing ink layer, and in the embodiment, three printing passes are carried out, wherein the following printing inks are respectively adopted:

1 PASS: UVLED red special + UVLED blue special;

2 PASS: UVLED red special + UVLED blue special;

3 PASS: UVLED6662-2 four-color red + UVLED4411-2 four-color blue + UVLED8018 black ink + UVLED yellow; the UVLED red special ink, the UVLED blue special ink and the UVLED yellow special ink are prepared by UVLED series ink produced by Conlin chemical Co., Ltd, Fushan City; UVLED6662-2 four-color red and UVLED4411-2 four-color blue adopt UVLED series printing ink produced by Conlin chemical limited company of Fushan City, and the printing ink is irradiated and dried by using an LED-UV curing light source;

coating gloss oil: coating in a rolling coating mode by vertically leaving a hollow rubber roller on the whole plate surface, wherein the used gloss oil is HF-701H type gloss oil produced by the Breyns chemical Co., Ltd, the main component is acrylic resin, the solid content is 45 +/-2% (m/m), drying is carried out in a heating curing mode that the temperature of a metal flat plate is kept at 180 ℃ for 12 minutes by baking, and the weight of a coating dry film is 8 g/square meter;

the surface hardness of the bright oil layer is the hardness of a 2H pencil;

(2) printing external gloss oil on the part of the surface of the gloss oil layer needing to generate thick texture by adopting a lithographic offset printing method, and curing and drying to form an external gloss oil layer, which specifically comprises the following steps:

the used ink is SCP ULED-540W printing LED-UV semi-matte oil produced by Shanghai super-color ink company Limited;

separately manufacturing corresponding printing plates according to the parts needing to generate thick texture, transferring the semi-matte oil layer of the printing plates to the specific parts needing to generate thick texture on the surface of the metal flat plate through a rubber blanket, irradiating, curing and drying by using an LED-UV light source to form an external gloss oil layer, wherein the light source intensity is 8W/cm²The printing surface absorption energy value is 300mj/cm²The ink amount is controlled to be 0.5 CC;

controlling the surface tension of the external gloss oil layer to be 36 dyn/cm;

controlling the surface hardness of the external gloss oil layer to be the hardness of a 2H pencil;

(3) the method comprises the following steps of screen printing thick film gloss oil on the surface of an external gloss oil layer, and then curing and drying to form the thick film gloss oil layer, wherein the method specifically comprises the following steps:

the gloss oil is UV-JS-LS laser gloss oil produced by Hangzhou constant base coating ink company Limited;

separately manufacturing corresponding screen printing plates according to the parts needing to generate thick texture, wherein the mesh number of screen printing is 100/inch;

transferring the thick film gloss oil leakage print to a specific part of the surface of the metal flat plate needing to generate thick texture by using scraper pressure, and then irradiating, curing and drying by using a UV light source;

the surface hardness of the thick film gloss oil layer is controlled to be 2H pencil hardness.

The metal plate printed through the above process is used to make a rust remover sample can for automobiles, as shown in fig. 1, and it can be seen from the figure that a remarkable concavo-convex thick texture is generated at a portion where a thick texture is required, i.e., an english letter "WD-40", compared to other portions.

Example 2

The difference from the embodiment 1 is that when the single lithographic printing plate is prepared in the step (2), the prepared printing plate is a local image-text amplification plate with the image-text edge size expanded outwards, which is prepared by using an AI file to the part needing to generate thick texture, and the local image-text amplification plate is printed on the surface of a metal flat plate by a lithographic offset press to realize the edge expansion of local images and texts, wherein the overprinting error of the ink layer image-text, the external gloss oil layer and the thick film gloss oil layer is controlled to be 0.15mm, and the image-text edge size is expanded outwards by 0.2 mm.

Example 3

The difference from the embodiment 2 is that when the single printing plate is manufactured before the printing layer of the offset lithographic printing in the step (2), the manufactured printing plate is a local image-text enlarged plate for manufacturing the image-text edge size extension of the part needing to generate thick texture through an AI file, so that the local image-text enlarged plate is printed on the surface of a metal flat plate by an offset lithographic printing machine to realize the edge extension of local image-text, wherein the overprinting error of the image-text of the ink layer, the printing layer of the external gloss oil and the printing layer of the thick film is controlled to be 0.15mm, and the image-text edge size extension is 0.3 mm.

Example 4

The difference from the embodiment 2 is that,

the weight of the dry coating film coated with the gloss oil in the step (1) is 10g per square meter;

in the step (2), an external gloss oil layer is formed by irradiating, curing and drying through an LED-UV light source with the intensity of 12W/cm²The printing surface absorption energy value is 450mj/cm²The ink amount is controlled to be about 0.6 CC;

controlling the surface tension of the external gloss oil layer to be 42 dyn/cm;

the mesh number of the screen printing in the step (3) is 120 pieces/inch;

the surface hardness of the bright oil layer, the external smooth oil layer and the thick film smooth oil layer is controlled to be the hardness of a 3H pencil.

Example 5

The difference from example 2 was that the surface hardness of the glossy oil layer and the thick film glossy oil layer was controlled to be 4H pencil hardness, and the hardness of the outer glossy oil layer was controlled to be 2H pencil hardness.

Comparative example 1

The difference from example 1 is that the process of step (3) is performed after the graphic ink layer is prepared in step (1), i.e. the ink is directly printed on the lithographic printing text by silk screen printing to realize ink accumulation, and then a gloss oil layer is coated (rolling causes extrusion damage), and step (2) in example 1 is omitted.

Comparative example 2

The difference from example 1 is that step (2) in example 1 was omitted directly, i.e., the ink was screen printed directly on the gloss oil layer to achieve ink build-up.

Comparative example 3

The difference from example 1 is that the surface tension of the external gloss oil layer prepared in step (2) is 30 dyn/cm.

Comparative example 4

The difference from example 2 is that the surface hardness of the glossy oil layer and the thick film glossy oil layer was controlled to be 2H pencil hardness, and the outer glossy oil layer was controlled to be H pencil hardness.

The detection of the quality of the finished product comprises an adhesion test, a surface hardness test, an anti-scratch test and a thick part printing thickness test.

Quality of the finished product

1. Surface hardness test: in the above examples and comparative examples, the surface hardness was measured using a Chinese-style pencil reference GB/T6739.

2. And (3) testing the adhesive force: the use of 3M #610 tape was performed in accordance with GB1720-1979, but without the need for grid or circle marking on the silk-screened thick film varnish layer, and the results are shown in Table 1.

3. The surface scratch resistance test method comprises the following steps: using a SHEEN hardness tester, 150mm X100 mm pieces of the samples were placed on a flat plate holder with the film surface facing upward and fixed, and the flat plate holder was moved at a constant speed from left to right with weights on the gram basis of the weight without leaving the bottom as a standard for the film hardness, and the results are shown in Table 1.

4. Local thick part printing thickness test: and measuring by using a micrometer, namely firstly measuring the total thickness of the thick gloss oil layer area of the silk screen of the metal flat plate, measuring three dispersed points and averaging, then measuring the thickness of the surface protection gloss oil area of the metal flat plate, measuring three dispersed points and averaging, and taking the difference value of the front average value and the rear average value as the average thickness of the printing bulges of the local thick part.

The results of the above tests are shown in Table 1.

TABLE 1 quality of the printed Metal Panels obtained in the examples and comparative examples

Note: comparative example 1 after roller coating a glossy oil layer, a thick film glossy oil layer was damaged by extrusion.

As can be seen from the above table, the local thick texture of the metal flat plate for packaging can be achieved by the method of the present invention, and at least level II and above adhesion is maintained between the layers:

from the comparison between the embodiment 1 and the embodiment 2, when the external gloss oil layer is offset printed by the offset lithography, the external expansion of the printing plate size corresponding to the local image-text is beneficial to improving the adhesive force between the thick film gloss oil layer and the external gloss oil layer;

as can be seen from comparison between comparative example 1 and example 1, in the existing offset printing process for metal plates, the silk screen printing ink is directly deposited on the offset printing image-text, although a certain height of deposition can be achieved, the adhesion of the silk screen printing ink is poor, and meanwhile, in the subsequent processes such as roll coating and glazing, the silk screen printing layer is easily damaged, the film thickness is reduced, and meanwhile, local image-text deformation is caused;

from the comparison of comparative example 2 with example 1, it is clear that the screen printing effect directly on the gloss oil layer is not very good, the adhesion between the gloss oil layer and the thick film gloss oil layer is low, and the thick film gloss oil layer is easily damaged in the subsequent processing and the transportation and storage of the packaging worker;

as can be seen from comparison of comparative example 3 with example 1, reasonable control of the surface tension of the exterior gloss oil layer is important for the realization of the method;

it can be seen from comparison of comparative example 4, example 5 and example 2 that controlling the surface hardness of the gloss oil layer, the external gloss oil layer and the thick film gloss oil layer to be not less than 2H of pencil leads to positive effects, and further, maintaining the consistency of the surface hardness of the gloss oil layer, the external gloss oil layer and the thick film gloss oil layer is also beneficial to improving the adhesion between the layers of the product and keeping the adhesion between the layers to be not less than grade I.