CN112776491A

CN112776491A - Screen printing process

Info

Publication number: CN112776491A
Application number: CN201911077163.9A
Authority: CN
Inventors: 唐枫
Original assignee: Shanghai Caiyi Printing Co ltd
Current assignee: Shanghai Caiyi Printing Co ltd
Priority date: 2019-11-06
Filing date: 2019-11-06
Publication date: 2021-05-11

Abstract

The invention discloses a silk-screen printing process, which comprises the following steps: s1, selecting a silk screen, cleaning the silk screen, removing impurities and drying; s2, stretching the screen, fixing the screen mesh on the screen frame, and cleaning and drying the screen mesh again; s3, coating photosensitive glue on the silk screen, and then drying the silk screen in the sun; s4, carrying out development treatment, washing with clear water and drying to obtain a screen printing plate; s5, installing the screen printing plate into a screen printing device, and adding ultraviolet curing ink for printing; s6, printing down; and S7, taking out the printed finished product, and naturally cooling and forming at room temperature. The silk-screen printing process is simple, the printing quality is obviously improved and stable, and the printing ink printing layer on the printed matter is uniformly colored, has strong adhesive force and good wear resistance.

Description

Screen printing process

Technical Field

The invention relates to the technical field of printing, in particular to a screen printing process.

Background

Printing techniques have originated in China, and have a long history in China. With the continuous improvement of the technological level, especially the development of computer technology, the printing industry has also entered the digital era. Meanwhile, the development of the ceramic industry, the electronic industry, the advertising industry and the like puts higher and higher requirements on the printing technology. Among many printing processes, the screen printing process is a printing process with rapid development and many advantages, which uses a photosensitive material to make a screen printing plate by a photoengraving method, and when printing, ultraviolet curing ink (UV ink) is transferred to a printing stock through meshes of an image-text part by extrusion of a scraper, so as to form an image-text same as that of an original. The screen printing equipment is simple, convenient operation, and printing, platemaking are simple and easy and low cost, strong adaptability, and common printed matter has: color paintings, posters, business cards, binding covers, merchandise tags, printed and dyed textiles, and the like.

However, the existing screen printing process is too dependent on the production experience of operators, and a normalized and digitalized production flow is not formed, so that the quality and the precision of the screen printing process are difficult to be ensured to be in the same standard; meanwhile, in the screen printing process, the UV ink is adopted to form an ink printing layer on a printing stock, so that the ink printing layer on a printed matter is yellowed under the irradiation of natural light, and the yellowing resistance of the printed matter is poor; in addition, the existing UV ink has weak acting force with the printing stock, so that the adhesive force of the ink printing layer on the printing stock is poor, the surface wear resistance is poor, and the ink printing layer is easy to fall off after long-term use or when the printed matter is stressed and bent.

Disclosure of Invention

In order to solve the problems in the background art, the invention aims to provide a screen printing process which is simple, remarkably improved and stable in printing quality, uniform in coloring of an ink printing layer on a printed matter, strong in adhesive force and good in wear resistance.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a screen printing process, which comprises the following steps:

s1, selecting a silk screen, wherein the silk screen can be a polyester silk screen, a nylon silk screen, a polyester silk screen or a stainless steel silk screen, the mesh number of the silk screen is 240 meshes and 300 meshes, the thickness of the silk screen is 6-10mm, cleaning and removing impurities from the silk screen, and then drying the silk screen;

s2, stretching the processed silk screen by using a manual or stretching machine, fixing the silk screen on a screen frame through adhesive glue after the silk screen is stretched, wherein the screen frame is a rectangular hollow aluminum screen frame, sticking the silk screen around the outside of the screen frame at the sharp end after the adhesive glue is dried, then sticking a single-sided adhesive tape on the part where the silk screen is bonded with the screen frame, and cleaning and drying the silk screen again;

s3, coating photosensitive glue on the silk screen, and then drying the silk screen by using a silk screen drying lamp, wherein the time for drying the silk screen is controlled to be 18-24 h; wherein the photosensitive emulsion comprises 30-35% of heavy complex acid salt and 65-70% of gelatin by mass;

s4, then, putting the screen into pure water containing a developer at the temperature of 30-40 ℃ for developing, and after the patterns are completely presented, washing and drying the screen by using clean water to obtain a screen printing plate; the developing agent adopts a bathophenanthroline reagent with the mass fraction of 15-20%;

s5, installing the screen printing plate into a screen printing device, adding ultraviolet curing ink for printing, and forming an ink layer on a printing stock;

the ultraviolet curing ink comprises the following components in parts by mass: 20-30 parts of polyester acrylic resin, 10-20 parts of aldehyde ketone resin, 5-10 parts of lauric acid modified epoxy acrylic resin, 5-10 parts of trihydroxy methyl propane triacrylate, 0.5-1.5 parts of 2, 4, 6-trimethylbenzoyl-diphenyl phosphine oxide, 0.1-1 part of poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] acetone ], 10-15 parts of active diluent, 1-3 parts of additive, 1-2 parts of pigment and 15-30 parts of ethanol;

s6, performing plate burning treatment by adopting an ultraviolet cold light lamp in an environment of 35-45 ℃, wherein the plate burning time is 3-5min, and the ink layer on the printing stock is cured and formed to form an ink printing layer;

and S7, taking out the printed finished product, and naturally cooling and forming at room temperature.

According to the invention, ultraviolet curing ink with a specific component ratio is adopted, polyester acrylic resin, aldehyde ketone resin, lauric acid modified epoxy acrylic resin and trihydroxy methyl propane triacrylate are selected as main film forming substances, 2, 4, 6-trimethylbenzoyl-diphenyl phosphine oxide and poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] acetone ] are added as photoinitiators, under the action of ultraviolet light, the photoinitiators initiate unsaturated double bonds in the film forming substances to perform polymerization reaction, polymer molecules form a net structure, and the speed of film forming can be controlled by adding an active diluent; the poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] acetone ] is a low-odor and non-yellowing photoinitiator, has good compound property with a selected film forming substance, can be uniformly mixed with resin in the film forming substance, and the 2, 4, 6-trimethylbenzoyl-diphenyl phosphine oxide can improve deep curing of a product, meet the drying requirement of the product, so that an ink printing layer has stronger adhesive force and is not easy to fall off.

Preferably, in the step S5, the reactive diluent is a mixture of ethyl acetate and diacrylate in a mass ratio of (1-3): 1. By adding ethyl acetate and diacrylate, the viscosity of the ultraviolet curing ink can be adjusted, the film forming process is promoted, and the polymerization degree and polymer properties of the reaction are controlled.

Preferably, in the step S5, the additive is a mixture of polydimethylsiloxane, polyether modified polysiloxane and polyethylene wax in a mass ratio of (1-1.2): 0.8-1): 1.

The phenomenon of blooming of an ink layer on a printing stock can be prevented by adding polydimethylsiloxane; by adding polyether modified polysiloxane, the surface tension can be reduced, a substrate can be wetted, and the leveling performance of the ink layer can be improved; the wear resistance of the ink can be improved by adding the polyethylene wax, and the extinction effect can be achieved, so that the ink printing layer on the final printing stock has better luster and stereoscopic impression.

Preferably, in step S2, after the screen is cleaned and the impurities are removed, the screen needs to be degreased by using a sodium hydroxide solution with a mass fraction of 20-25%. By carrying out degreasing treatment on the silk screen, the subsequent coating of the photosensitive glue on the surface of the silk screen is more uniform, and the combination between the photosensitive glue and the silk screen is firmer.

Preferably, in step S3, the photoresist layer is coated on the screen twice, and both sides of the screen are coated each time, and the dry thickness of the photoresist layer is 3-5% of the thickness of the screen.

Preferably, in step S7, the used screen printing plate is soaked in 75-80 ℃ sodium hydroxide aqueous solution for 30-50S, the printing material is automatically peeled off, and then the screen printing plate is washed with clean water, dried and stored in a place without dust.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the screen printing process flow is optimized, and the process parameters in each step are limited, so that the screen printing effect is obviously improved, the stability of the printing quality is ensured, and the practicability is strong; the ultraviolet curing ink with a specific component ratio is adopted, an ink printing layer formed by silk-screen printing and curing has excellent yellowing resistance, and meanwhile, the ink printing layer on a printing stock is more uniformly colored, has stronger adhesive force and wear-resistant surface, and is not easy to burst when being stressed and bent.

Drawings

The invention is described in further detail below with reference to specific embodiments and with reference to the following drawings.

Fig. 1 is a flow chart of a screen printing process in the present invention.

Detailed Description

Example 1

The invention provides a screen printing process, as shown in fig. 1, comprising the following steps:

s1, selecting a silk screen, wherein the silk screen is a polyester silk screen in the embodiment, the mesh number of the silk screen is 240 meshes, the thickness of the silk screen is 8mm, cleaning and removing impurities from the silk screen, drying the silk screen, and then degreasing the silk screen by using a sodium hydroxide solution with the mass fraction of 20-25%;

s3, coating photosensitive resist on the silk screen twice, wherein the front side and the back side of the silk screen are coated each time, the dry thickness of the photosensitive resist layer is 5% of the thickness of the silk screen, and then drying the silk screen by using a screen drying lamp, wherein the screen drying time is controlled to be 24 h; wherein the photosensitive emulsion comprises complex acid salt with the mass fraction of 30% and gelatin with the mass fraction of 70%;

the ultraviolet curing ink comprises the following components in parts by mass: 24 parts of polyester acrylic resin, 10 parts of aldehyde ketone resin, 5 parts of lauric acid modified epoxy acrylic resin, 6 parts of trihydroxy methyl propane triacrylate, 1.5 parts of 2, 4, 6-trimethylbenzoyl-diphenylphosphine oxide, 0.3 part of poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] acetone, 13 parts of reactive diluent, 2 parts of additive, 1.6 parts of pigment and 30 parts of ethanol;

in this example, the reactive diluent is a mixture of ethyl acetate and diacrylate in a mass ratio of 1: 1; the additive is a mixture of polydimethylsiloxane, polyether modified polysiloxane and polyethylene wax in a mass ratio of 1:0.9: 1.

and S7, taking out the printed finished product, naturally cooling and forming at room temperature, soaking the used screen printing plate in a sodium hydroxide aqueous solution at the temperature of 75-80 ℃ for 30-50S, automatically dropping the printing material, washing the screen printing plate with clear water, drying, and storing in a place without dust.

Example 2

s1, selecting a silk screen, wherein the silk screen is a nylon silk screen in the embodiment, the mesh number of the silk screen is 260 meshes, the thickness of the silk screen is 6mm, cleaning and removing impurities from the silk screen, drying the silk screen, and then degreasing the silk screen by using a sodium hydroxide solution with the mass fraction of 20-25%;

s3, coating photosensitive resist on the silk screen twice, wherein the front side and the back side of the silk screen are coated each time, the dry thickness of the photosensitive resist layer is 4% of the thickness of the silk screen, and then drying the silk screen by using a screen drying lamp, wherein the screen drying time is controlled to be 18 h; wherein the photosensitive emulsion consists of 35 mass percent of complex acid salt and 65 mass percent of gelatin;

the ultraviolet curing ink comprises the following components in parts by mass: 20 parts of polyester acrylic resin, 20 parts of aldehyde ketone resin, 10 parts of lauric acid modified epoxy acrylic resin, 5 parts of trihydroxy methyl propane triacrylate, 1.2 parts of 2, 4, 6-trimethylbenzoyl-diphenylphosphine oxide, 0.1 part of poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] acetone ], 10 parts of reactive diluent, 1 part of additive, 1 part of pigment and 24 parts of ethanol;

in this example, the reactive diluent is a mixture of ethyl acetate and diacrylate in a mass ratio of 3: 1; the additive is a mixture of polydimethylsiloxane, polyether modified polysiloxane and polyethylene wax in a mass ratio of 1.2:0.8: 1.

Example 3

s1, selecting a silk screen, wherein the silk screen in the embodiment is a polyester silk screen, the mesh number of the silk screen is 300 meshes, the thickness of the silk screen is 10mm, cleaning and removing impurities from the silk screen, drying the silk screen, and then degreasing the silk screen by using a sodium hydroxide solution with the mass fraction of 20-25%;

s3, coating the photosensitive adhesive on the silk screen twice, wherein the front side and the back side of the silk screen are coated each time, the dry thickness of the photosensitive adhesive layer is 3% of the thickness of the silk screen, and then drying the silk screen by using a screen drying lamp, wherein the screen drying time is controlled to be 18 h; wherein the photosensitive emulsion consists of 32 mass percent of complex acid salt and 68 mass percent of gelatin;

the ultraviolet curing ink comprises the following components in parts by mass: 30 parts of polyester acrylic resin, 16 parts of aldehyde ketone resin, 8 parts of lauric acid modified epoxy acrylic resin, 10 parts of trihydroxy methyl propane triacrylate, 0.5 part of 2, 4, 6-trimethylbenzoyl-diphenylphosphine oxide, 1 part of poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] acetone ], 15 parts of reactive diluent, 3 parts of additive, 2 parts of pigment and 15 parts of ethanol;

in this example, the reactive diluent is a mixture of ethyl acetate and diacrylate in a mass ratio of 2: 1; the additive is a mixture of polydimethylsiloxane, polyether modified polysiloxane and polyethylene wax in a mass ratio of 1:1: 1.

Comparative example 1

Comparative example 1 is a comparative test to example 1, with the following differences: in comparative example 1, the components of the uv curable ink were not added with poly [ 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl ] propanone ], and the remaining components, preparation process and parameter settings were the same as in example 1.

The prints obtained in examples 1 to 3 and comparative example 1 were tested for yellowing resistance, force bending resistance and adhesion, and the specific test results are shown in table 1.

The yellowing resistance was specifically measured by using an ultraviolet aging lamp as a light source, and the prints obtained in examples 1 to 3 and comparative example 1 were exposed to a temperature of (30. + -. 3 ℃ C.) and an irradiance of 0.68W/m²And in the dried fluorescent ultraviolet aging machine, continuous illumination is kept for 24 hours in the whole process, the dried fluorescent ultraviolet aging machine is taken out after the illumination is finished, and compared with a printed matter which is not illuminated, the color change is measured by a color difference meter, the unit delta E of the color change value is smaller, and the yellowing resistance is better.

The procedure of the force bending property test was to fold the printed matters obtained in examples 1 to 3 and comparative example 1 repeatedly at 180 degrees for 5 times, and to observe whether the ink printed layer at the folded position bursts or not.

The procedure of the adhesion property test was to vertically apply a force of 2Kg to the surface of the prints obtained in examples 1 to 3 and comparative example 1 with an eraser to make 5 passes, and to observe whether the ink printed layer on the surface of the print faded or not.

TABLE 1

The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.

Claims

1. A screen printing process comprising the steps of:

s1, selecting a silk screen, wherein the mesh number of the silk screen is 240 meshes and 300 meshes, the thickness of the silk screen is 6-10mm, cleaning and removing impurities, and then drying the silk screen;

s2, stretching the processed silk screen, fixing the silk screen on the screen frame through adhesive glue after the silk screen is stretched, and cleaning and drying the silk screen again after the adhesive glue is dried;

s3, coating photosensitive glue on the silk screen, and then drying the silk screen by using a silk screen drying lamp, wherein the time for drying the silk screen is controlled to be 18-24 h;

s4, then, putting the screen into pure water containing a developer at the temperature of 30-40 ℃ for developing, and after the patterns are completely presented, washing and drying the screen by using clean water to obtain a screen printing plate;

2. The screen printing process according to claim 1, wherein in the step S5, the reactive diluent is a mixture of ethyl acetate and diacrylate in a mass ratio of (1-3): 1.

3. The screen printing process according to claim 1 or 2, wherein in the step S5, the additive is a mixture of polydimethylsiloxane, polyether-modified polysiloxane, polyethylene wax in a mass ratio of (1-1.2): 0.8-1): 1.

4. The screen printing process according to claim 1, wherein in the step S2, after the screen is cleaned and the impurities are removed, the screen is further degreased by using a sodium hydroxide solution with a mass fraction of 20-25%.

5. The screen printing process according to claim 1, wherein in step S3, the photoresist layer is coated on the screen twice, and both sides of the screen are coated each time, and the dry thickness of the photoresist layer is 3-5% of the thickness of the screen.

6. The screen printing process according to claim 1, wherein in the step S7, the used screen printing plate is immersed in an aqueous solution of sodium hydroxide at a temperature of 75 to 80 ℃ for 30 to 50 seconds, the printing material is peeled off by itself, and then the screen printing plate is washed with clean water, dried and stored in a place free from dust.