CN117820924A

CN117820924A - Oxygen barrier layer and flexible plate with built-in flat top lattice points containing same

Info

Publication number: CN117820924A
Application number: CN202311854905.0A
Authority: CN
Inventors: 王晓阳; 陈雷; 高英新; 冯磊; 黄永山; 许文然; 余志华; 杨媛媛; 王国才
Original assignee: Lucky Huaguang Graphics Co Ltd
Current assignee: Lucky Huaguang Graphics Co Ltd
Priority date: 2023-12-29
Filing date: 2023-12-29
Publication date: 2024-04-05

Abstract

The oxygen barrier layer and the flexible plate with built-in flat top lattice points containing the oxygen barrier layer have the main component for blocking oxygen permeation of polyethylene substances and have the capability of crosslinking polymerization. Under strong enough ultraviolet exposure, the crosslinking polymerization of the ultraviolet radiation causes difficulty in removing the oxygen barrier layer in the plate washing process, and residues are often formed on the field part of the plate, so that the plate cannot be cleaned. The addition of the polymerization inhibitor in the oxygen barrier layer can effectively prevent the formation of residues. The field part of the plate manufactured by the invention can not form residues under the UVA lamp tube or the LED lamp beads.

Description

Oxygen barrier layer and flexible plate with built-in flat top lattice points containing same

Technical Field

The invention relates to a flexible plate with built-in flat top dots, in particular to an oxygen barrier layer and a flexible plate with built-in flat top dots containing the oxygen barrier layer. The application belongs to green printing materials in the 3.19 ecological environment material sub-direction under the 3.1 novel functional material industry key direction in the 3 new material industry of the strategic emerging industry catalogue.

Background

Until now, the development of flexo flat top dot technology has proposed its own technical solution from plate suppliers to equipment manufacturers. Analysis of these techniques has readily found that the prior art has achieved flat top dots around shielding oxygen or reducing the effect of oxygen on resin polymerization during flexographic printing.

The influence of oxygen on the elastomer is isolated in early days mainly through peripheral equipment.

The dupont DigiFlow technology adopts a mode of filling nitrogen into an exposure machine to isolate oxygen, and the exposure machine (such as DigiFlow2000 EC) is provided with an oxygen concentration detection, UV energy detection and temperature control device to accurately control the exposure process. Nitrogen is the primary consumable in this process and nitrogen cylinders or nitrogen making machines are the necessary investments beyond conventional flexographic plate making procedures. The technology has the advantages that the type of the plate used by the user is not limited, the laser plate based on the black film system is compatible, the comprehensive cost of nitrogen is low, and the customer needs to purchase the exposure equipment again.

The kodak NX technology and the medes mailux technology are used for isolating oxygen by coating the surface of the plate material through a film coating machine, so that a user must use a special film or an imaging material provided by a plate material provider. The Maidemar technology is an open technology, and a user can use any plate material with a black film, so that flat-top net points can be manufactured by using original equipment only by purchasing a film laminating machine and a corresponding film. However, unlike plate making systems that use black films, kodak technology requires that the user must use kodak's NXH plate, NX thermal imaging films, and dedicated laser engraving machines. However, the film coating technology is sensitive to dust in the environment, and occupies the edge material of the plate, so that certain waste is caused.

The technical route of Fullent and Ai Sike is to use high energy LED UV lamps to expose the plate during the main exposure stage, with a rapidly formed polymeric layer to reduce the oxygen impact on the process. Ai Sike is known as the Inline UV technology, i.e. a high energy led UV tube is built into a conventional laser engraving machine CDI. Compared with the first generation of online UV exposure equipment, the latest online UV2 technology with the full high definition function needs to be exposed after the engraving of the plate is completed; fulin is a traditional exposure machine with built-in LED UV light source, named NExT technology. The technical routes of the two are similar. Although the LED UV lamp built in CDI can reduce the CDI usage, if the user purchases the online back exposure unit of Ai Sike, the main exposure device is not needed, which helps the printing enterprise to improve the process automation level and reduce the manpower. The exposure machine of the Fulin special built-in LED UV light source solves the problem that the main exposure process of the Inline UV technology occupies CDI time, meanwhile, the technology of combining the LED UV light source with the traditional UV light source is adopted, a user can select to singly adopt the LED UV light source for exposure, and the LED UV light source and the traditional UV light source can also be used for mixed exposure, so that the convenience and the flexibility in production are provided for the user. While LED UV light sources have an inherent advantage in stabilizing output UV light sources, the problems of excessive exposure time and excessive equipment costs associated with LED UV light sources alone are also drawbacks. The technology of two companies is also a completely open technology, and a laser plate based on a black film system can be used, but the LED UV exposure technology is adopted, so that the exposure equipment needs to be upgraded or additionally purchased.

At present, each company mainly sets an oxygen barrier layer on the plate material or improves the photoinitiation efficiency of the plate material, thereby achieving the purpose of realizing the dot flatting.

Typical patents such as Fulin CN105745578B provide oxygen barrier layers composed of water-washable polyvinyl alcohol and the like. CN107969149A, an oxygen barrier layer of 0.3-5 μm, is composed of polyvinyl acetal and basic adhesive components (oligomeric or polymeric polyvinylamine and polyethyleneimine).

In the practical use process, once the light intensity of the polyvinyl alcohol component reaches a certain level under the exposure of ultraviolet rays, cross-linking bodies can be formed under the action of a photoinitiator in the photosensitive elastomer, and the cross-linking bodies are difficult to dissolve and wash out in a plate washing liquid, particularly tetrachloroethylene n-butyl alcohol plate washing liquid. In the large field part of the plate, the plate becomes a residue which cannot be removed.

The photoinitiation efficiency of the printing plate is improved, namely more free radicals are generated in unit time in the exposure process through a better ultraviolet initiator or an initiation system, and when oxygen does not quench the free radicals, cross-linking is formed on the surface of the printing plate, so that the penetration of oxygen into the elastomer is prevented; or the elastomer is added with a more sensitive monomer which is easy to crosslink, and in the patent CN201680048472.1, the flat-top halftone dot is obtained by adding 0.05 to 0.2 percent of butyl hydroxy toluene by weight ratio into the photosensitive elastomer layer. This approach is undoubtedly detrimental to the photo-aging resistance of the plate. The plate is often decayed in the secondary on-press printing process and cannot be printed.

Disclosure of Invention

In order to solve the problems, the invention provides an oxygen barrier layer and a flexible plate with built-in flat top dots containing the oxygen barrier layer. By adding the polymerization inhibitor into the oxygen barrier layer containing the polyethylene substances, the polymerization problem caused by the initiation of the initiator in the photosensitive elastomer of the polyethylene substances in the oxygen barrier layer under the exposure of ultraviolet rays is effectively solved. Thus solving the problems that the oxygen barrier layer cannot be removed well in the plate washing process because of the polymerization of substances in the oxygen barrier layer, and residues are formed on the plate in situ due to the oxygen barrier layer, and the printing plate is uneven in inking.

The object of the invention is achieved in the following way: the raw materials of the oxygen barrier layer comprise an oxygen barrier agent, an adhesive and a coating auxiliary agent, wherein the oxygen barrier agent and the adhesive contain polyethylene substances, and the oxygen barrier layer contains a polymerization inhibitor.

The content of the polymerization inhibitor is 0.1-5% of the mass of the polyethylene substance.

The oxygen barrier is polyvinylpyrrolidone, the adhesive is polyvinyl amine, the dry weight of the oxygen barrier layer is calculated according to mass percent, the oxygen barrier layer comprises 50-80% of polyvinylpyrrolidone, the K value of the polyvinylpyrrolidone is 100-150, the mass of the polyvinyl amine is 10-50% of the polyvinylpyrrolidone, the content of the polymerization inhibitor is 0.1-5% of the mass of the polyvinylpyrrolidone, the coating auxiliary agent comprises at least one of a surfactant, a leveling agent or a thickening agent.

The polymerization inhibitor comprises at least one of phenolic polymerization inhibitor, quinone polymerization inhibitor, aromatic hydrocarbon nitro compound polymerization inhibitor or inorganic compound polymerization inhibitor.

The phenolic polymerization inhibitor is hydroquinone, resorcinol, catechol or tert-butyl catechol, the quinone polymerization inhibitor is p-benzoquinone, methyl chloranil or tetrachlorobenzoquinone, and the inorganic compound polymerization inhibitor is sodium sulfate, ferric chloride, sodium sulfide or ammonium thiocyanate.

A flexible plate with built-in flat top lattice points comprises a protective layer, a mask layer capable of laser ablation, an oxygen blocking layer, a photosensitive elastomer and a supporting body from top to bottom, wherein the oxygen blocking layer is used for blocking oxygen.

Compared with the prior art, the flexible plate with built-in flat top dots is characterized in that the oxygen barrier layer is arranged on the photosensitive elastomer, and the quenching of oxygen in the air to free radicals generated in the photosensitive elastomer is blocked in the ultraviolet exposure process, so that the crosslinking efficiency and the crosslinking depth are improved.

The main component of the oxygen barrier layer of the present invention, which is resistant to oxygen permeation, is a polyethylene-based material, which itself also has the ability to crosslink and polymerize. Under strong enough ultraviolet exposure, the crosslinking polymerization of the ultraviolet radiation causes difficulty in removing the oxygen barrier layer in the plate washing process, and residues are often formed on the field part of the plate, so that the plate cannot be cleaned. The addition of the polymerization inhibitor in the oxygen barrier layer can effectively prevent the formation of residues. The field part of the plate manufactured by the invention can not form residues under the UVA lamp tube or the LED lamp beads.

Detailed Description

The present invention will now be described in detail with reference to specific examples, which are given herein for further illustration only and are not to be construed as limiting the scope of the invention, since numerous insubstantial modifications and adaptations thereof will now occur to those skilled in the art in light of the foregoing disclosure.

The raw materials of the oxygen barrier comprise an oxygen barrier, an adhesive and a coating auxiliary agent, wherein the oxygen barrier and the adhesive contain polyethylene substances, and the oxygen barrier is characterized in that: the oxygen barrier layer further comprises a polymerization inhibitor.

The polymerization inhibitor accounts for 0.1 to 5 percent of the mass of the polyethylene.

The oxygen-blocking agent is polyvinylpyrrolidone, the adhesive is polyvinyl amine, the dry weight of the oxygen-blocking layer is calculated according to mass percent, the polyvinylpyrrolidone is 50-80%, the K value of the polyvinylpyrrolidone is 100-150, the mass of the polyvinyl amine is 10-50% of the polyvinylpyrrolidone, the content of the polymerization inhibitor is 0.1-5% of the mass of the polyvinylpyrrolidone, and the coating auxiliary agent comprises at least one of a surfactant, a leveling agent or a thickening agent. The polyvinyl amine is an excellent adhesive to bond the photosensitive elastomer layer and the laser ablation mask layer together. And the adhesiveness is not affected by carbon dioxide in the air like polyethyleneimine, and the adhesiveness is not attenuated.

A flexible plate comprises a protective layer, a mask layer capable of laser ablation, an oxygen blocking layer, a photosensitive elastomer and a support body from top to bottom, wherein the oxygen blocking layer is the oxygen blocking layer.

The mask layer, the oxygen barrier layer and the photosensitive elastomer can be dissolved or dispersed in solvents such as halohydrocarbon, alcohols, amines and the like, namely, can be dissolved or dispersed in popular flexographic plate washing liquid such as quick morning plate washing liquid, n-butyl alcohol, tetrachloroethylene plate washing liquid and the like in the market.

Support body

The support is a dimensionally stable carrier. A dimensionally stable support of 50-300 μm thickness is generally used, the material of which is steel, aluminum, an alloy or a plastic, for example ethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate or polycarbonate. Particularly suitable are PET films of 100-200 μm thickness. In the common flexographic plate, a PET film with a thickness of 175 μm was used for plates with a thickness of 1.14mm or less, and a PET film with a thickness of 125 μm was used for other flexographic plates.

The carrier may optionally be treated with conventional adhesion treatments. Such as corona treatment, chemical etching treatment, physical bonding, etc.

Between the support and the photoelastic layer, there may be other layers, such as an adhesive layer or an elasticity-enhancing layer.

Photosensitive elastomer

The photosensitive elastomer raw materials generally include: at least one elastomeric binder, an ethylenically unsaturated monomer, and a photoinitiator system. Other ingredients, plasticizers, dyes, UV absorbers, and the like may also be included. The photosensitive elastomer layer is also known as a photopolymerizable relief forming layer.

Elastomeric adhesives are well known to those skilled in the art, for example: styrene-diene block copolymers, natural rubber, polybutadiene, polyisoprene, styrene-butadiene rubber, nitrile rubber, butyl rubber, styrene-isoprene rubber, styrene-butadiene-isoprene rubber, polynorbornene rubber or ethylene-propylene-diene rubber. Binders soluble in non-polar hydrocarbon solvents and alcohols with medium polarity are preferred.

The elastomer preferably comprises a thermoplastic elastomeric block copolymer of an alkenyl aromatic compound and a 1, 3-diene, and the preferred elastomeric binder is a triblock copolymer of the type a-B-a or a radial block copolymer of the type (AB) n, wherein a is styrene and B is a diene, and statistical and random copolymers of styrene and diene. The total amount of elastomeric binder is preferably 45 to 75% by weight;

Containing ethylenically unsaturated double bonds and being a polymerizable monomer, typically 3 to 1 5 mass%.

At least one photoinitiator or photoinitiator system, preferably 3 to 6% by weight; the plasticizer is modified and unmodified natural oil and natural resin, and the optional content is 0-40 mass%. In addition, surface-active substances, such as hydrophobic waxes or siliconizing or perfluorinated compounds, may be included, as described in us 8,114,566. During flexographic plate drying, these materials migrate from the relief layer to the surface, repel the printing ink, and reduce the fouling of fine dots during printing and thus reduce the frequency with which the plate must be cleaned.

The relief forming layer thickness is usually 0.1 to 7mm, preferably 0.5 to 4mm, more preferably 0.7 to 2.5mm.

Oxygen barrier layer

The thickness of the oxygen barrier layer is 0.5-5 ų m.

An oxygen barrier layer is disposed between the photosensitive elastomer layer and the laser ablatable mask layer/laser ablatable black film, the layer being capable of bonding the photosensitive elastomer layer and the laser ablatable mask layer together. When the protective film is removed, the black film of the laser ablatable mask layer can be perfectly separated from the protective film and completely covered on the surface of the photosensitive elastomer. Meanwhile, when the laser-ablatable mask layer such as a black film is subjected to laser ablation imaging, the laser ablation does not damage the oxygen barrier layer, and the oxygen barrier layer is still completely remained on the photosensitive elastomer after the black film is ablated.

The oxygen barrier layer typically has an oxygen permeability of less than 1000, preferably less than 500 (cm ³ ×100μm) /(m ² X d x bar). For the oxygen barrier layer (C) in principle any flexible elastomeric adhesive having an oxygen permeability below the agreed maximum can be used, while satisfying other requirements such as transparency to UVA light and solubility or dispersibility in commercially available flexographic flushing media.

Flexible binders having an oxygen barrier effect, such as polyvinylpyrrolidone. The K value of polyvinylpyrrolidone is related to the flexibility, and the K value is selected to be more than 100, so that the oxygen barrier layer can be ensured to have enough flexibility. This feature is particularly valuable at low winter temperatures. Polyvinylpyrrolidone coatings with low K values are prone to brittle fracture.

The mere polyvinylpyrrolidone is difficult to perfectly bond the laser-ablatable mask layer/the laser-ablatable black film and the photosensitive elastomer into a whole. For this reason, there is also a need for an alkaline adhesion component that increases adhesion, i.e., an oligomeric or polymeric alkaline adhesion component, an amine-containing water-soluble resin, such as a polyvinylamine. Other adhesives, such as polyethylenimine, although sufficiently good, gradually decay in adhesion over time, and even affect the integrity of the laser ablatable mask layer/laser ablatable black film when the protective film base is removed using the plate. Whereas polyvinylamine does not have such drawbacks.

The thickness of the oxygen barrier layer is particularly preferably 1 μm to 2. Mu.m. Thicker oxygen barrier layers, although more advantageous for oxygen barrier perfection, are a problem of plate material due to dot gain, and at the same time, thicker oxygen barrier layers are prone to fracture at low temperatures. The thinner oxygen barrier layer has insufficient oxygen barrier, and the cross-linking of the small dots is partially affected by oxygen and cannot be well reduced. Because the dissolution and swelling of the oxygen barrier layer in the plate washing liquid cannot be too much, the less and the better the oxygen barrier effect is ensured.

Laser ablate mask layer

The laser ablatable mask layer, also called laser ablatable black film, is 0.5-5 ų m thick. At least one binder and a material which both blocks ultraviolet light and absorbs infrared light, the binder of the photoablative mask layer (D) being selected from the group consisting of polyamides, polyvinylpyrrolidone (PVP), nitrocellulose and polyvinyl acetals, preferably polyamides. The infrared absorbing and ultraviolet blocking material is selected from carbon black, graphite, carbon nanoparticles and carbon nanotubes, preferably carbon nanoparticles.

The film layer can absorb infrared laser and is subjected to laser ablation, for example, laser imaging machines such as 830nm and 1064nm in the current market can perform laser ablation imaging on the film layer to form a mask.

The film layer can absorb infrared laser and burn on one hand, and on the other hand, the film layer also has enough blocking effect on ultraviolet rays, and the photosensitive elastomer covered by the black film can not cross-link polymerize under UVA exposure in the process of making the plate.

The film layer is also capable of dissolving or dispersing in commercially available plate washes.

The laser ablatable mask layer comprises carbon black as a component capable of absorbing and ablating infrared light, and comprises carbon black in various forms, such as carbon black, graphite, carbon nano particles, carbon nano tubes and the like. Among them, carbon nanoparticles are most preferable.

Very suitable adhesives for the mask layer are flexible elastic adhesives, for example ethylene vinyl acetate, flexible elastic polyamides, flexible elastic polyurethanes, nitrocellulose, polyvinyl acetals such as poly (vinyl butyral-vinyl alcohol) copolymers (Butvar, mowital) or poly (vinyl butyral-vinyl acetal-vinyl alcohol) copolymers (Picoloform). Of course, other flexible elastomeric materials may be used as binders, such as partially hydrolyzed polyvinyl acetate. A preferred adhesive for the mask layer is flexible elastomeric polyamide Technomelt PA6900.

The amount of absorbing material is generally such that the optical density of the layer to UVA radiation is from 1 to 5. The UVA radiation range includes light having a wavelength of 300-400 nm. The optical density is the logarithmic coefficient of the permeability of the inner layer of this wavelength range. Thus, in measuring optical density, the measured value is not a separate value of light permeability at a particular wavelength, but is an average value of light permeability over a specified wavelength range. Optical density is typically measured using a commercially available densitometer (e.g., from x-rite), where the wavelength range is selected prior to measurement. For the purposes of the present invention, all cited optical density measurements are based on the UVA range, i.e. the range of 300-400 nm.

The preferred mask layer has an optical density of 2-5. The high optical density ensures that the masked areas of the photoelastic body do not polymerize during exposure to UVA light. Suitable light absorbing materials include, in particular, carbon black, graphite, carbon black nanoparticles or carbon nanotubes. These materials absorb very well in the near IR range and are therefore both laser ablated and uv blocking materials. The proportion of this material in the whole mask layer is 10 to 60% by weight, preferably 20 to 40% by weight. The weight of the mask layer is 2-5g/m ² Of these, 2-4g/m is preferred ² When the ablation energy is within this range, the ablation energy is about 3.0-4.5J/cm ² The laser ablation imaging machine for the flexographic plate on the market can be well suitable for the laser ablation imaging machine for the flexographic plate on the market, and the laser ablation imaging machine works in a normal state and under proper efficiency.

Protective layer

The protective layer is a removable protective film. The purpose of which is to protect the flexographic plate. It is removed prior to laser ablation imaging. The material of the removable outer film may be PET film. The thickness is 80-150 μm, preferably 100-130 μm, and the average roughness value (Ra) is preferably 0.02-0.5 μm. The film may be transparent or semi-opaque, and generally, the film preferably has a certain haze, which facilitates the distinction of the two sides of the plate.

Production of flexographic printing plates according to the invention

The flexographic printing plates of the present invention are produced in a known manner by melting the components of the photoelastic layer in an extruder, mixing them and discharging the melt of the starting material of the photoelastic layer through a slot die into the nip of a calender. On one calender roll is a support coated with other layers, such as an adhesive layer, and traveling through the other calender roll is a protective film comprising an oxygen barrier layer, a laser ablatable mask layer, and a protective film. The support, photoelastic, and protective film with the oxygen barrier layer and laser ablatable mask layer are joined together by calendaring.

In the production of a protective film assembly, a laser ablatable mask layer is first applied to the protective film. The coating procedure may be carried out from solution, melt or by spraying. The laser ablate mask layer will then be covered with an oxygen barrier layer. Prior to coating the individual layers, it may be necessary to treat the surface portion of the support PET sheet base to be coated by means of corona or the like in order to achieve a greater spreading capacity. It must be stated that the effect of the corona pretreatment generally declines with the storage time of the printing plate and a permanently satisfactory adhesion cannot be achieved.

Alternatively, the layers may be applied separately to different films and then laminated together. For example, the mask layer and the oxygen barrier layer may be each coated on one film. In this case, a mask layer is coated on the protective film, and an oxygen barrier layer is coated on the temporary auxiliary film. After the coating, the two films were laminated to each other by lamination, and the temporary auxiliary film was removed.

Techniques for coating are known to those skilled in the art. The thickness of the layer to be coated can be adjusted in a known manner by releasing the coating liquid or changing coating parameters, such as the gap or coating speed or the feed speed. To improve the coating quality, it may be necessary to add surface-active substances or flow control adjuvants such as leveling agents or thickeners to the coating solution.

The coated protective film is rolled up and passed through one of the calender rolls during subsequent extrusion and in this way firmly bonded to the photoelastic body as a plate whole.

Alternatively, a layer-by-layer approach may be used in multiple steps. For example, an oxygen barrier layer included on a temporary auxiliary film may be passed through a calender roll and bonded to the photopolymerizable layer. The auxiliary film is then removed. Then, in a second lamination step, the laser ablatable mask layer is laminated with the photosensitive elastomer laminated with the oxygen barrier layer to form a plate.

The process of processing the plate material into the flexographic printing plate

The plate making process comprises the following steps of 1-7:

1. back-exposing the plate to form a suitable base, which may also be performed after step 4;

2. the protective film is removed. The protective film is simply removed, and the ablation mask layer and the lower oxygen barrier layer still remain on the photosensitive elastomer completely;

3. imaging on a laser ablatable mask layer by means of an IR laser, such laser imaging machines are also known as CDI, and there are currently two machines on the market, 1064nm and 830 nm.

4. The UVA light exposes the photosensitive elastomer through the mask layer to image, which can be common UVA lamp tube or latest ultraviolet led lamp beads,

5. Removing the residual part of the laser ablatable mask layer, the oxygen barrier layer and the unpolymerized part of the photosensitive elastomer) by using a flexographic rinse solution, wherein the rinse solution can be a well-known mixed solution of tetrachloroethylene and n-butanol in a volume ratio of 3 to 1, or can be various environment-friendly rinse solutions commonly used in the market;

6. fully drying the obtained flexographic printing plate;

7. post exposure to UVA and de-adhesion to UVC, or elimination of this step.

Through the plate making process, the plate becomes a printable flexible plate. This plate making process is exactly the same as a conventional digital flexographic plate.

When using the flexographic plate material of the present invention, expensive and inconvenient exposure conditions such as nitrogen are not required, and expensive and inconvenient film lamination to the imaged laser ablation mask is not required, nor is the imaged film coated on the photoelastic body by lamination equipment.

Alternatively, the flexographic plates of the present invention can also be thermally developed. In this case, the flexographic plate is mounted on a drum and heated from the surface until melting occurs. The fabric strip is then pressed against the flexographic plate material to adhere the unexposed areas of the photoelastic, the barrier layer, and the remainder of the laser ablatable mask layer. This operation is repeated a number of times until the desired relief height is reached.

Example 1

The technology of the digital flexible plate is omitted by adding an oxygen blocking functional layer on the basis of the digital flexible plate.

In the examples of the oxygen barrier layer, the following components were used in parts by mass:

polyvinylpyrrolidone K100 100

Polyvinyl amine with molecular weight of 15 ten thousand 20

Polymerization inhibitor (phenolic compound), hydroquinone 2

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Polyvinyl pyrrolidone is prepared into 8% aqueous solution, polyvinyl amine (prepared into 5% aqueous solution in advance) is slowly added under stirring (300-500 rpm), then 1% aqueous solution of hydroquinone (prepared in advance) is added, and finally surfactant is added, and after proper stirring, the coating liquid is obtained.

Preparation of plate

Coating the coating liquid of the oxygen barrier layer on the photosensitive elastomer of the Huaguang DR170LS, which is stripped of the protective film and the black film, through a No. 40 silk rod, and then covering and pressing the stripped black film with the protective film on the oxygen barrier layer; or the oxygen barrier layer is coated on the black film by the same method and then is covered on the light-blocking DR170LS photosensitive elastomer. Heating at 100-120deg.C for five minutes. Cooling to room temperature to prepare the plate.

Plate making method

Plate making is then performed as with a conventional digital flexographic plate. For example, after back exposure, removing the protective film on the black film, performing laser imaging on the CDI of ESKO, exposing the black film for 15 minutes by using a common UVA lamp tube of a exposure machine of a scientific trade (the main exposure result of the LED lamp beads is better), and performing plate washing by using a commercially available environment-friendly plate washing liquid in the morning (or tetrachloroethylene plate washing liquid with the volume ratio of tetrachloroethylene to n-butanol of 3:1) at a plate washing speed of 160 mm/minute by using a common online plate washing machine of the scientific trade (or on a platform plate washing machine). After 1.5 hours of plate baking, the plate is exposed for 5 minutes and de-glued for 5 minutes.

And (3) plate testing:

150lpi, and under the condition of not adding a correction curve, the screen dot tester tests 1% of screen dots, and can restore 1%. The field part is smooth and clean. No foreign matter was attached when observed under a microscope.

In the following examples, the same procedure as in the test was conducted except that the amounts of the raw material components of the oxygen barrier layer were changed.

Example 2

The technology of the digital flexible plate is omitted.

In an embodiment of the oxygen barrier layer, the following composition is used:

Polyvinylpyrrolidone K120 100

Polyvinyl amine with molecular weight of 15 ten thousand 20

Polymerization inhibitor (phenolic compound), hydroquinone 2

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Polyvinyl pyrrolidone is prepared into 8% aqueous solution, polyvinyl amine (prepared into 5% aqueous solution in advance) is slowly added under stirring (300-500 rpm), then 1% aqueous solution of hydroquinone (prepared in advance) is added, finally sodium dodecyl sulfate is added, and the mixture is properly stirred to obtain coating liquid.

Preparation of plate

Plate making method

And (3) testing the plate:

under 150lpi, 1% of the dots can be restored to 1% under the condition of not adding a correction curve, and the field part is smooth and clean.

Example 3

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K150 100

Polyvinyl amine with molecular weight of 15 ten thousand 20

Polymerization inhibitor (phenolic compound), hydroquinone 2

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And (3) testing the plate:

under 150lpi, under the condition of not adding a correction curve, 1% of the dots can be restored to 0.8%, and the field part is smooth and clean.

Example 4

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 100

Polyvinyl amine with molecular weight of 10 ten thousand 20

Polymerization inhibitor (phenolic compound), hydroquinone 2

Sodium dodecyl sulfonate 5.

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And (3) testing the plate:

Example 5

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 100

Polyvinyl amine with molecular weight of 20 ten thousand 20

Polymerization inhibitor (phenolic compound), hydroquinone 2

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And (3) testing the plate:

Example 6

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 100

Polyvinyl amine with molecular weight of 20 ten thousand 20

Polymerization inhibitor (quinone compound), tetrachlorobenzoquinone 2

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And testing the plate.

Under 150lpi, under the condition of not adding a correction curve, 1% of the dots can be restored to 0.5%, and the field part is smooth and clean.

Example 7

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 100

Polyvinyl amine with molecular weight of 20 ten thousand 20

Polymerization inhibitor (aromatic nitro compound), nitrobenzene 2

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And testing the plate.

Under 150lpi, under the condition of not adding a correction curve, 1% of the dots can be restored to 0.3%, and the field part is smooth and clean.

Example 8

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 100

Polyvinyl amine with molecular weight of 20 ten thousand 20

Polymerization inhibitor (inorganic compound), sodium sulfate 1

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And (3) testing the plate:

at 150lpi, under the condition of not adding a correction curve, 2% of the dots can be restored to 0.5%, and the field part is smooth and clean.

Example 9

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 80

Polyvinyl amine with molecular weight of 20 ten thousand 14.9

Polymerization inhibitor (phenolic compound), hydroquinone 0.1

Sodium dodecyl sulfate 5;

preparation of oxygen barrier layer

Preparation of plate

Plate making method

And (3) testing the plate:

at 150lpi, under the condition of not adding a correction curve, 2% of the dots can be restored to 1.6%, and the field part is smooth and clean.

Example 10

The technology of the digital flexible plate is omitted.

polyvinylpyrrolidone K120 75

Polyvinyl amine with molecular weight of 20 ten thousand 15

Polymerization inhibitor (phenolic compound), hydroquinone 5

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Preparation of plate

Plate making method

And (3) testing the plate:

at 150lpi, under the condition of not adding a correction curve, 2% of the dots can be restored to 0.2%, and the field part is smooth and clean.

Comparative example

The flat-top screen dot plate is realized by adding an oxygen barrier layer on the basis of a common digital flexible plate.

An oxygen barrier layer formed by the following components is added in the Huaguang digital flexible plate:

polyvinylpyrrolidone K100 100

Polyvinyl amine with molecular weight of 15 ten thousand 20

Sodium dodecyl sulfonate 5

Preparation of oxygen barrier layer

Polyvinyl pyrrolidone is prepared into 8% aqueous solution, polyvinyl amine (prepared into 5% aqueous solution in advance) is slowly added under stirring (300-500 rpm), and finally sodium dodecyl sulfate is added, and the mixture is properly stirred to form a coating liquid.

Preparation of plate

Plate making method

And (3) testing the plate:

under 150lpi, 1% of the dots can be reduced to 1% without adding a correction curve, and residues exist in the field part and cannot be washed cleanly.

While only the preferred embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and it should be noted that equivalents and modifications, variations and improvements made according to the technical solution of the present invention and the inventive concept thereof, as well as those skilled in the art, should be considered as the scope of the present invention, without departing from the general inventive concept thereof.

Claims

1. The raw materials of the oxygen barrier comprise an oxygen barrier, an adhesive and a coating auxiliary agent, wherein the oxygen barrier and the adhesive contain polyethylene substances, and the oxygen barrier is characterized in that: the oxygen barrier layer contains a polymerization inhibitor.

2. The oxygen barrier of claim 1, wherein: the content of the polymerization inhibitor is 0.1-5% of the mass of the polyethylene substance.

3. The oxygen barrier of claim 1, wherein: the oxygen barrier is polyvinylpyrrolidone, the adhesive is polyvinylpyrrolidone, the dry weight of the oxygen barrier layer is calculated according to mass percent, the oxygen barrier layer comprises 50-80% of polyvinylpyrrolidone, the K value of the polyvinylpyrrolidone is 100-150, the mass of the polyvinylpyrrolidone is 10-50%, the content of the polymerization inhibitor is 0.1-5% of the mass of the polyvinylpyrrolidone, and the coating auxiliary agent comprises at least one of a surfactant, a flatting agent or a thickening agent.

4. The oxygen barrier of claim 1, wherein: the polymerization inhibitor comprises at least one of phenolic polymerization inhibitor, quinone polymerization inhibitor, aromatic hydrocarbon nitro compound polymerization inhibitor or inorganic compound polymerization inhibitor.

5. The oxygen barrier of claim 1, wherein: the phenolic polymerization inhibitor is hydroquinone, resorcinol, catechol or tert-butyl catechol, the quinone polymerization inhibitor is p-benzoquinone, methyl chloranil or tetrachlorobenzoquinone, and the inorganic compound polymerization inhibitor is sodium sulfate, ferric chloride, sodium sulfide or ammonium thiocyanate.

6. A flexographic plate with built-in flat top dots, characterized in that: the mask comprises a protective layer, a laser ablatable mask layer, an oxygen barrier layer, a photosensitive elastomer and a support body from top to bottom, wherein the oxygen barrier layer is as claimed in any one of claims 1 to 5.