CN115157806A

CN115157806A - Digital printing plate and preparation method thereof

Info

Publication number: CN115157806A
Application number: CN202210721301.8A
Authority: CN
Inventors: 唐道远
Original assignee: Anhui Sentai Wpc Technology Floor Co ltd
Current assignee: Anhui Sentai Wpc Technology Floor Co ltd
Priority date: 2022-06-24
Filing date: 2022-06-24
Publication date: 2022-10-11
Anticipated expiration: 2042-06-24
Also published as: CN115157806B

Abstract

The invention provides a digital printing plate and a preparation method thereof, when the thickness of a base material layer is not less than 5mm, the digital printing plate comprises the base material layer mainly composed of hot-melt first resin and filler, a background film layer compounded with the decorative surface of the base material layer into a whole, a 2D pattern layer arranged on the surface of the background film layer and a 3D simulation layer covering the 2D pattern layer and mainly composed of second resin; when the thickness of the base material layer is not more than 5mm, the digital printing plate further comprises an elastic stress layer which is compounded with the base surface of the base material layer into a whole besides the structure; the elastic stress layer and the background film layer are compounded with the base material layer into a whole in an online pressing or co-extrusion mode. According to the invention, through research on the thickness of the substrate layer and the product quality, two digital printing plates with different structures are provided based on the substrate layers with different thicknesses, so that the production process and the product structure can be simplified, and the product yield can be ensured.

Description

Digital printing plate and preparation method thereof

Technical Field

The invention relates to the technical field of 3D printing plates, in particular to a digital printing plate and a preparation method thereof.

Background

In the finishing of floors, floorboards are often used. In order to improve the appearance grade of floor decoration, the solid wood floor is usually the preferred object of high-grade decoration, and the formed wood grains and patterns can improve the visual aesthetic feeling. However, the solid wood floor has high requirements for wood quality, is expensive, has high maintenance cost, brings great economic expense for paving and use, and is not in accordance with the current environmental protection concept.

In order to reduce the production and maintenance costs and increase the service life of the floor, various materials have been used in place of solid wood, and these alternative products have also been provided with wood grain and patterns by some means. For example, patent document CN202011282338.2 provides a stone-plastic floor, which uses PVC and stone powder as raw materials to prepare a stone-plastic substrate, and then a color film and other film layers are attached to the substrate. Compared with solid wood, the stone-plastic base material has the advantages of water resistance, fire resistance, corrosion resistance and the like, the production cost and the maintenance cost are both lower than those of the solid wood, and the attached color film can simulate the wood grain effect, so that the wood-plastic base material can replace a wood floor to a certain extent. However, the real wood grain is formed by a 3D structure, and the 2D wood grain formed by the color film has a great visual difference from the real wood grain, so that it is difficult to obtain the real-looking simulated solid wood floor.

Patent document CN202010237877.8 discloses an indoor floor based on polyolefin biomass composite material, which uses polyolefin and biomass material as raw materials to prepare a core material, and then a wood skin is attached to the outer layer of the core material.

Patent document CN202010725836.3 discloses an SPC-based 3D printing plate, specifically, the plate comprises an SPC base layer, a 3D printing color layer and a UV protective layer; the base material layer comprises an SPC core layer and a background film layer which is compounded with the SPC core layer together through co-extrusion; the background film layer is also imprinted with textures in the form of wood grains, decorative patterns or patterns; or the SPC base material layer comprises an SPC core layer and a background film layer which is laminated and compounded with the SPC core layer on line, and further comprises a resin concave-convex effect layer, wherein the resin concave-convex effect layer is arranged between the color layer and the UV protective layer. In the patent document, a planar pattern is formed by printing a color layer, and a three-dimensional gully effect is formed by impressing textures in the form of wood grains, patterns or arranging a resin concave-convex effect layer, so that the wood imitation effect of the board is further improved, and natural materials such as wood veneer and the like are not required. However, this solution has a certain disadvantage in the implementation process, that is, the resin concave-convex effect layer needs to be formed on the substrate layer by using a material such as a photo-polymerization resin, and the surface layer stress is inevitably changed in the photo-polymerization process, so that the cracking and bending phenomena of the whole board often occur.

Patent document CN202111419020.9 provides a substrate for digital printing and a digital printing plate, in the technical scheme of the patent document, the substrate for digital printing with an elastic stress layer on a substrate surface is firstly prepared, then 3D printing operation is performed on the decorative surface of the substrate, the elastic stress layer is utilized to offset the warping stress generated in the forming process of a pattern simulation layer, and the elastic stress layer and the pattern simulation layer can be balanced to prevent the plate from being bent. The purpose of this patent is to further solve the problem of cracking and bending of the substrate layer, which requires stress cancellation between the elastic stress layer and the pattern simulation layer. In the actual production process, in order to achieve the above effects, the material formulation and thickness of the elastic stress layer and the forming process of the elastic stress layer on the substrate need to be controlled specially, and the elastic stress layer is prefabricated, so that the requirement on the elastic stress layer is particularly high during manufacturing, the process needs to be controlled strictly, the effect is not obvious when the stress is small, and the reverse warpage is easy to occur when the stress is large; although the pilot plant test of the product of the prior scheme is successful, the product cannot be produced in large products because the parameters need to be strictly controlled, the requirement on equipment is high, and the operation window is small.

Disclosure of Invention

The invention provides a digital printing plate and a preparation method thereof, which are used for solving the problems of possible cracking and bending of the integral plate and enabling the plate to be easier to implement production.

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

a digital printing plate comprises a base material layer, a background film layer, a 2D pattern layer and a 3D simulation layer, wherein the base material layer is mainly composed of hot-melt first resin and filler; the 3D simulation layer forms a three-dimensional pattern structure with concave and convex parts; the thickness of the base material layer is not less than 5mm.

The existing 3D grain forming mode is as follows: the method includes the steps of forming a pattern layer with a 2D pattern on a substrate by printing and the like, covering the 2D pattern with a layer of flowing resin precursor (such as liquid formed by monomers of photo-polymerization resin and initiators thereof), then carrying out local treatment on the flowing resin precursor, and finally carrying out curing treatment on the resin precursor, wherein the part subjected to local treatment is not cured or forms polymer with low hardness, so that the part is easy to remove, and a 3D ravine structure is formed after the part is removed. Generally, the 3D resin layer formed by curing the resin precursor is transparent, so that the pattern of the pattern layer can be observed through the 3D resin layer, and the ravine structure formed by the resin layer can provide 3D visual effect for the 2D pattern, thereby forming the wood-like 3D grain. Obvious shrink can take place at the in-process of resin precursor solidification, thereby make the 3D resin layer produce by the stress of edge part to the middle part, and this stress can be dragged the substrate layer compound with the 3D resin layer, lead to substrate layer to decorative surface one side warpage, and the substrate layer is mainly made by PVC and the inorganic mineral powder more than 70%, consequently toughness is lower, produce fracture phenomenon easily under the effect of top layer stress, it can reduce fracture phenomenon to a certain extent to add more plasticizer to the substrate layer to make substrate layer toughness improve, but too much addition of plasticizer can lead to substrate layer own material softer, the angularity that produces when receiving the stress is great, lead to the product percent of pass to reduce. Therefore, in the prior art, the scheme that structures such as an elastic stress layer are adopted to offset the stress of the 3D resin layer is adopted, and the bending and the fracture of the plate are avoided. However, the inventors found that when producing 3D printed sheets with a structure of "elastic stress layer-substrate layer-background layer-3D resin layer", there was a significant yield difference between different batches of sheets. Therefore, the inventors hoped to solve the problem of large lot-to-lot variation. Through strict production management, the inventor finds that the problem between batches is not caused by misoperation. The inventors had to presume that this is due to the fact that the technical solution of "elastic stress layer-substrate layer-background layer-3D resin layer" itself has high requirements for parameter control and is difficult to implement.

During product pilot testing, the inventors found that the thickness parameter of the substrate layer had some effect on batch variation. Therefore, the inventors adjusted the thickness of the base material appropriately. In the experiment, the inventor controls the thickness of the base material to be more than 4mm, and then carries out the technical scheme of 'elastic stress layer-base material layer-background layer-3D resin layer', and finds that the difference between batches is obviously reduced, and the yield is improved. Therefore, the inventors presume that the substrate has a strong resistance to the elastic stress of the surface layer when the substrate layer reaches a certain thickness. The inventors further imagined that if the substrate layer was further thickened, the provision of the elastic stressing layer was not necessary.

The inventor carries out a series of tests and finds that when the base material is made of PVC as a base resin, calcium carbonate as a filler and the contents of the base resin and the plasticizer are not more than 25%, the thickness of the base material layer can be adjusted to 5mm without the problem of warping and cracking of the whole plate. In the above test, the inventors have conducted a series of formulation adjustments and studied different proportions of PVC resin, calcium carbonate filler and plasticizer, and found that it is difficult to achieve 5mm as a threshold, i.e., to adjust the thickness of the base material to 5mm or less without using an elastic stress layer, without causing warpage or cracking of the entire plate material.

That is to say, when the thickness of substrate layer is more than 5mm, the structural strength of substrate layer self is enough to resist the stress in the 3D resin layer forming process, consequently need not to adopt to set up the elastic stress layer and also can guarantee that the product does not take place phenomenons such as warpage or fracture to this type of product, can reduce the production processes of product for the scheme that sets up the elastic stress layer.

In the prior art, the technical scheme for shielding the color of the base material layer is that the base material layer is treated by photo-curing white paint, namely, the decorative surface of the base material layer is coated with the white paint, and then the base material layer is treated by ultraviolet light, and a hard background layer formed by the white paint can be formed after the ultraviolet light is treated. The hard background layer formed by the white paint mainly comprises a non-hot-melt high polymer material, so that the toughness is also lacked, the hard background layer is similar to the 3D resin layer, and the substrate layer is subjected to warping force towards the decorative surface side along with obvious volume shrinkage in the forming process, the warping force of the hard background layer and the 3D resin layer on the substrate layer is superposed, and the threshold value of stress damage of the plate is further reduced.

The 'elastic stress layer' arranged in the prior art can solve the influence of the problems to a certain extent, but the scheme of the invention adopts another scheme to improve the situation because the 'elastic stress layer' is not arranged, namely a background film layer formed by hot-melt second resin is compounded on the decorative surface of the substrate layer to replace the light-cured white paint so as to solve the superposition problem. The background film layer and the substrate layer can be extruded out of the die together in a co-extrusion mode; the substrate layer can be combined with the substrate layer into a whole through hot pressing when the substrate layer is extruded and is not completely cooled by adopting an online pressing and pasting mode. Preferably, the mode of pressing and pasting the prefabricated background membrane layer on line can be adopted, because the thickness of the prefabricated background membrane layer is controlled more easily, and the color is more even after the prefabricated background membrane layer is compounded with the base material layer, so that the thickness of the background membrane layer can be controlled while the color of the base material layer can be shielded, and the product quality can be controlled accurately.

In addition, the background film layer is mainly formed by hot-melt resin materials, so that certain toughness can be provided for the base material layer, the base material layer can play a role in buffering when the decorative surface side is impacted, and the effect cannot be achieved by the hard background layer formed by the white paint.

Furthermore, the transverse tensile strength of the background film layer is not lower than 25MPa, and the longitudinal tensile strength of the background film layer is not lower than 30MPa.

Further, the transverse heating size change rate of the background film layer is not more than 2%, and the longitudinal heating size change rate is not more than 6%.

Further, the thickness of the background film layer is not more than one fifth of the thickness of the substrate layer.

In general, the longitudinal tensile strength and the transverse tensile strength of the background film layer obtained by the extrusion molding method are slightly different, and similarly, the longitudinal and transverse dimensional change rates of the extrusion-molded background film layer are also slightly different.

It should be noted that the heating dimension change rate is based on the ISO23999-2021 standard, and the specific method is as follows: cutting the background film layer into 240mm samples, drawing two pairs of parallel lines with a spacing of 200mm at a position 20mm away from the edges of the samples in the transverse direction and the longitudinal direction respectively to form four intersection points, placing the samples on an aluminum plate, placing the samples for 24 hours under the conditions of 23 +/-2 ℃ and 50 +/-5% RH, measuring two initial spacings of the four intersection points in the transverse direction and two initial spacings of the four intersection points in the longitudinal direction by calipers respectively, and averaging to obtain a transverse initial spacing A1 and a longitudinal initial spacing B1; the temperature in the constant temperature drying oven was adjusted to 80 ℃, the sample was put into the constant temperature drying oven together with the aluminum plate and placed for 6h, then the sample was taken out together with the aluminum plate, placed for 24h under 23 ± 2 ℃ and 50 ± 5% rh conditions, the pitches of the four intersection points in the transverse direction and in the longitudinal direction were measured again two by a caliper, and the transverse pitch A2 and the longitudinal pitch B2 were averaged, the transverse heating dimensional change rate = (A2-A1)/A1, the longitudinal heating dimensional change rate (B2-B1)/B1.

Further, the heat conductivity coefficient of the background film layer is larger than that of the substrate layer.

Because the scheme of the invention does not contain the elastic stress layer and the back surface of the substrate layer lacks reverse balance force, the product quality problem in the composite molding process of the substrate and the background film layer needs to be considered, otherwise, the risk of cracking of the substrate layer still exists when the stress generated by the background film layer is large enough. Generally speaking, two layers of thermoplastic materials are compounded in two ways, one is to perform the prefabrication molding of two layers of structures respectively and then compound the two layers of structures into a whole in a hot pressing mode, the other is to co-extrude the raw materials of the two layers of structures into the same mold to compound the two layers of structures into a whole structure, and because the physical parameters of the two layers of structures in all aspects are different, some aspects which need to be considered exist in the molding process. For the hot pressing method, the two layers of structures need to be heated and then cooled in the compounding process, and then a process from thermal expansion to cooling restoration exists in the process, so that the two layers of structures can respectively generate different volume changes. The base material layer contains a large amount of filler, so that the thermal expansion coefficient is small, and if the thermal expansion coefficient of the background film layer is large, the background film layer generates larger shrinkage and forms stress compared with the base material layer in the cooling and recovering process, so that the structural stability of the base material layer is influenced. For the co-extrusion method, a process of cooling from a molten state to a solid state exists in a two-layer structure, and the process generally also has a parameter of molding shrinkage, namely, the volume of the thermoplastic material after cooling and molding has a certain shrinkage relative to the volume of the molten state in a mold, and when the molding shrinkage of the substrate layer and the background film layer has a large difference, a large stress is also generated, but in the actual production process, the molding shrinkage of the film generally made of materials such as PVC, EVA and the like is less than 1%, so that relatively obvious influence cannot be generated. That is, in the case of the present invention, when the base layer and the background film layer are laminated by the co-extrusion method or the hot-press method, it is generally necessary to consider the dimensional change rate of the film. In addition, on the premise of shielding the color of the substrate layer, the thinner the background film layer is, the better the background film layer is, but some problems may exist in the subsequent 2D pattern layer and 3D resin layer molding process of the excessively thin background film layer, so that the background film layer needs to be kept with a certain thickness to ensure sufficient structural strength, and preferably, the thickness is one fifth to one tenth of the substrate layer.

It should be considered that, for the single substrate layer, both sides of the substrate layer directly contact with air during the cooling process, so the cooling rate is substantially equivalent, and after the single-side background film layer is compounded, the side of the substrate layer cannot directly exchange heat with air, so the cooling rate is reduced, so the thermal conductivity of the background film layer needs to be improved, and the thermal conductivity of the background film layer is larger than that of the substrate layer, thereby the defect is compensated. Because the thermal conductivity coefficients of different resin materials are different, in order to more conveniently and simply ensure the thermal conductivity coefficient size relationship between the background film layer and the substrate layer, the invention preferably can ensure that the base resins contained in the background film layer and the substrate layer are of the same type, for example, the base resins in the background film layer and the substrate layer are both PVC, and simultaneously the substrate layer contains fillers with the thermal conductivity coefficient lower than that of the base resins, such as heavy calcium carbonate and the like, thereby being capable of more easily forming the state that the thermal conductivity coefficient of the background film layer is greater than that of the substrate layer.

Further, the first resin is polyolefin resin or polyvinyl chloride resin.

Further, the background film layer is light color and can shield the color of the substrate layer. In the invention, the background film layer needs to cover the color of the substrate layer to avoid the influence of the color, lines and the like formed by the substrate layer on the visual effects of the 2D pattern layer and the 3D resin layer, and the color of the background film layer cannot influence the visual effects of the 2D pattern layer and the 3D resin layer, so that the background film layer needs to be made of a non-transparent or semitransparent light-colored material, and is preferably an opaque white film layer.

Further, a surface protection layer is compounded on the surface of the 3D resin layer. The surface protective layer is generally formed of an abrasion resistant material, such as a photo-curable paint, and the like, for protecting the concave-convex structure of the 3D resin layer from abrasion.

The invention also aims to provide another digital printing plate.

A digital printing plate comprises a base material layer mainly composed of first resin and filler, a first background film layer compounded with the decorative surface of the base material layer into a whole, an elastic stress layer compounded with the basal surface of the base material layer into a whole, a 2D pattern layer arranged on the surface of the first background film layer, and a 3D simulation layer which covers the 2D pattern layer and is mainly composed of second resin; the 3D simulation layer forms a three-dimensional pattern structure with concave and convex parts; the thickness of the base material layer is not more than 5mm.

Furthermore, the elastic stress layer is the same as the first background film layer, and the thickness of the elastic stress layer is not more than one fifth of the thickness of the base material layer.

The inventors found in actual production that when the SPC substrate layer thickness is less than 5mm, the board having the structure of "substrate layer-background layer-3D resin layer" produced has a certain defect in yield, and the substrate layer is likely to crack. The method for solving the problem in the prior art is to arrange an elastic stress layer, namely a product structure is elastic stress layer-substrate layer-background layer-3D resin layer, and the elastic stress layer is utilized to counteract the stress generated by the background layer and the 3D resin layer. However, in actual operation, because the elastic stress layer corresponds to the "background layer +3D resin layer" and the background layer is formed by compounding a plurality of light-curable lacquer layers, theoretically, the shrinkage rates of various materials need to be considered, and thus the required thickness of the elastic stress layer in actual production is difficult to control. The inventors have analyzed that the main cause of substrate layer cracking is insufficient toughness of the substrate layer, and the SPC substrate layer becomes hard but brittle because it contains a large amount of mineral powder fillers, and in the conventional 3D printing technology, it is necessary to coat primer, white paint, and 3D resin layer materials on the substrate layer, which all undergo significant shrinkage during molding to generate stress, and the brittle SPC substrate layer is difficult to withstand the stress when the thickness is 4mm or less. Therefore, in order to solve the problem of cracking of the substrate layer, improvement needs to be performed from two aspects, one is to enhance the toughness of the substrate layer and improve the stress resistance of the substrate layer, and the other is to reduce the stress generated in the 3D printing process and reduce the stress of the substrate layer. Based on the analysis, the invention provides a digital printing plate, wherein a background film layer and an elastic stress layer are arranged on two sides of a substrate layer of the plate in a co-extrusion or online laminating mode, and the preferable material and thickness of the background film layer and the elastic stress layer are the same, namely before 3D printing is carried out, the substrate layer forms a composite substrate of 'background film layer-substrate layer-background film layer', the overall toughness of the composite substrate is obviously enhanced compared with that of the substrate layer due to the elastic film layer structures arranged on two sides, and the stress resistance threshold value is improved. On the other hand, because the thickness of the base material layer is lower, the influence of the background film layer is obvious, and when the two surfaces are compounded with the film layers, the stress between the two background film layers can be offset, so that the structure of the compound base material is more stable.

On the other hand, in the invention, the elastic stress layer and the background film layer can be arranged simultaneously or sequentially, because even if the two layers cause asymmetric stress on the base material layer due to sequential compounding, the stress of the composite substrate can be released by means of hot rolling and the like, and because the elastic stress layers on two sides of the composite substrate subjected to hot rolling treatment are the same as the material and the thickness of the background film layer, the stress generated in the cooling process is basically symmetric, so that warping is not easy to occur.

The invention also aims to provide a preparation method of the digital printing plate.

A preparation method of a digital printing plate comprises the following steps:

s1, mixing a first hot-melt resin with a filler and heating to form a first melt, and introducing the first melt into a mold to form a substrate layer precursor;

s2, conveying the prefabricated film to one side surface of the base material layer precursor or conveying two layers of prefabricated films to two side surfaces of the base material layer precursor respectively, carrying out online hot-pressing on the film and the base material layer precursor when the base material layer precursor is not completely cooled and solidified, and then carrying out setting treatment to obtain a composite base material containing the film and the base material layer; or heating the raw materials for forming the background film layer or the raw materials for forming the background film layer and the elastic stress layer to form a second melt, introducing the second melt into a mold, coating the second melt on one side surface or two side surfaces of the substrate layer precursor which is not completely cooled, and compounding and shaping the second melt in the mold to obtain a composite substrate comprising the background film layer and the substrate layer or obtain a composite substrate comprising the background film layer, the elastic stress layer and the substrate layer;

s3, forming a 2D pattern layer on the background film layer of the composite base material through first printing equipment to obtain a first printed board;

s4, uniformly applying a non-solid second resin composition to the surface of the 2D pattern layer of the first printing plate; the non-solid second resin composition is a mixed liquid containing a prepolymer capable of being crosslinked to form a second resin, a monomer and an initiator; or the non-solid second resin composition is a molten second resin;

s5, applying a surface treatment liquid containing a polymerization inhibitor or a coagulation inhibitor to the surface of the second resin composition according to a pattern shape through a second printing device, curing the second resin composition in a cross-linking polymerization manner to form a 3D simulation layer precursor, and removing the surface treatment liquid or a mixture of the second resin composition and the surface treatment liquid to form a 3D simulation layer with a concave-convex three-dimensional pattern structure; the anticoagulant is a mixed liquid containing a prepolymer and a monomer which can form a third resin through crosslinking, and the tg value of the third resin is lower than that of the second resin;

and S6, coating a protective coating on the surface of the 3D simulation layer, and curing to form a surface protective layer, so as to obtain the digital printing plate.

In the method provided by the invention, the substrate layer precursor can be compounded with a background film layer, or a background film layer and an elastic stress layer, and the specific process depends on the thickness of the substrate layer; if the thickness of the base material layer is more than 5mm, only one background film layer is compounded, and one side surface compounded with the background film layer is called as a decorative surface; if the thickness of the base material layer is less than or equal to 5mm, the background film layer and the elastic stress layer are compounded, when the background film layer and the elastic stress layer are compounded, the elastic stress layer and the background film layer are preferably made of the same material and thickness, one side of the elastic stress layer and one side of the background film layer can be printed optionally during subsequent 3D printing, the layer structure compounded by the side subjected to the 3D printing and the base material layer is called the background film layer, the layer structure compounded by the side not subjected to the 3D printing and the base material layer is called the elastic stress layer, and therefore the naming of the background film layer and the elastic stress layer depends on the implementation mode of the subsequent 3D printing process.

The second resin is a photopolymerisable resin, the second resin composition is a prepolymer, a monomer and an initiator which form the photopolymerisable resin, and when the second resin composition is not polymerized, the second resin composition is in a liquid paint shape, so that the second resin composition can be uniformly coated on the surface of a background film layer with a 3D pattern. The surface treatment liquid can be a liquid substance containing a polymerization inhibitor, when the surface treatment liquid is applied to the second resin composition, a mixture containing the polymerization inhibitor, a prepolymer, a monomer and an initiator is formed at a part where the surface treatment liquid is in contact with the second resin composition, when the second resin composition is subjected to photopolymerization treatment, the second resin composition which is not in contact with the surface treatment liquid is normally cured to form hard photopolymerization resin, and the mixture is not cured or cured to form low-hardness oligomeric resin due to the existence of the polymerization inhibitor and is removed in the follow-up treatment by flushing and the like; or the surface treatment liquid is a mixed liquid of a prepolymer and a monomer, the prepolymer and the monomer can be crosslinked to form a third resin with a lower tg value, the second resin composition and the surface treatment liquid are respectively cured during photocuring, the second resin composition forms a harder second resin with a higher tg value, the surface treatment liquid forms a softer third resin with a lower tg value, the third resin can be removed from the surface of the second resin through an apparatus such as a steel brush in subsequent treatment, and a ravine structure formed by the space originally occupied by the third resin is formed on the surface of the second resin after removal. Before the surface treatment liquid is applied, the second resin composition may preferably be subjected to an ultraviolet light pretreatment to reduce the fluidity of the second resin composition, so as to facilitate the setting of the 3D simulation layer and the formation of a boundary between the second resin composition and the surface treatment liquid, and the ultraviolet light intensity and treatment time should be controlled to avoid an excessively high curing degree of the second resin composition.

In summary, the following beneficial effects can be achieved by applying the technical scheme of the invention:

according to the invention, the thickness of the base material layer is adjusted, so that the product yield can be ensured while the production process and the product structure are simplified. When the base material layer is more than 5mm, the plate structure is a base material layer-background film layer-2D pattern layer-3D simulation layer, an elastic stress layer does not need to be attached to the back surface of the base material layer to offset stress generated by the 3D simulation layer, the structural strength of the base material layer is matched with the elastic background film layer made of resin materials, so that the aim of preventing the base material layer from cracking can be fulfilled, and the stress generated by molding shrinkage of the white primer in the existing scheme of covering the color of the base material layer through the white primer is eliminated; when the base material layer is less than 5mm, the plate structure is an elastic stress layer-base material layer-background film layer-2D pattern layer-3D simulation layer, wherein the elastic stress layer, the background film layer and the base material layer are pre-compounded and molded, and then the 2D pattern layer and the 3D simulation layer are processed, the problems of cracking and the like of the base material layer in the follow-up 3D printing process are avoided by utilizing the toughening effect of the elastic stress layer and the background film layer, and preferably, the elastic stress layer and the background film layer are made of the same material and have the same thickness, so that the stress on two sides of the base material layer is symmetrical, the probability of warping and cracking of the base material layer is reduced, meanwhile, when the base material layer and the background film layer are made of the same material and the thickness, the composite base material can be printed and processed by 3D by selecting any surface, and the production and the processing are more convenient.

Detailed Description

Comparative example 1

S1, mixing PVC resin, coarse whiting, a plasticizer and other additives, heating the mixture through a first extruder, and introducing the mixture into a mold to form a base material layer precursor; the base material layer comprises 15 parts of PVC resin, 75 parts of triple superphosphate, 3 parts of plasticizer, 3 parts of compatilizer, 1.5 parts of stabilizer, 1 part of lubricant and 0.5 part of antioxidant;

s2, mixing PVC resin and other additives, heating, melting and guiding the mixture into a secondary flow channel of a mold through a second extruder to form an elastic stress layer precursor, coating the basal plane of the substrate layer precursor, and guiding a composite structure formed by the substrate layer precursor and the elastic stress layer precursor out of the mold after shaping and cooling to obtain a substrate with the basal plane compounded with an elastic stress layer; wherein, the thickness of the base material layer is 3mm, and the thickness of the elastic stress layer is 0.5mm;

s3, coating adhesion primer on the decorative surface of the base material by using a roller coater, wherein the coating weight is 10g/m ² Curing by ultraviolet light; in this example, 395 nm, 8W/cm was used ² Irradiating by an ultraviolet lamp;

s4, coating a white primer 30g/m on the surface with the primer by using a roller coater ² Curing by ultraviolet light; setting the illumination intensity as the previous step;

s5, guiding the base material into 2D printing equipment, guiding a pattern to be printed on the 2D printing equipment, setting the size of a plate, setting the height of a printing head, and turning on a vacuum adsorption device, an LED and an ultraviolet curing lamp; printing a required 2D plane pattern on the decorative surface of the base material obtained in the last step; the color paste of the printed pattern is ultraviolet curing color paste; after printing, the pattern is shaped through the irradiation of an ultraviolet curing lamp to obtain a first printing substrate; the equipment in the step is 2D printing equipment purchased in the market;

s6, coating a wear-resistant layer on the 2D plane pattern of the first printing base material by using a roller coater, wherein the wear-resistant coating amount is 50g/m ² Ultraviolet curing; setting the operation of the illumination intensity is the same as that of the operation;

s7, coating a second resin composition on the surface of the wear-resistant layer by using a roll coater, wherein the second resin composition mainly comprises acrylic acid, methacrylic acid and oligomers thereof, and acrylic acid and methacrylic acid monomers account for about 70vol%; allowing a small amount of other monomers or their oligomers such as methyl methacrylate, ethyl acrylate, etc.; necessarily containing a small amount of photoinitiator; the coating amount of the second resin composition was 180g/m ² (ii) a Carrying out photocuring treatment by using ultraviolet curing equipment to ensure that the first resin layer on the surface is not completely cured when a product passes through the equipment;

s8, selectively spraying surface treatment liquid on the pattern simulation layer precursor at fixed points according to the printing pattern by using 3D printing equipment, and then respectively curing the second resin composition and the surface treatment liquid through ultraviolet treatment; in this step, the surface treatment liquid is a photocurable monomer, but is different from the monomer in the third resin composition; in this example, the 3D ink is mainly composed of n-butyl methacrylate, n-hexyl methacrylate, and oligomers thereof; substances formed by allowing a small amount of other monomers or their oligomers, such as methyl acrylate, ethyl acrylate, and butyl acrylate, to be mixed; necessarily containing a small amount of photoinitiator; wherein the n-butyl methacrylate and the n-hexyl methacrylate monomer account for about 85vol%;

s9, removing substances formed by solidifying the surface treatment liquid by using a roller brushing machine; in the process, the hardness of the brush roller steel brush needs to be adjusted, substances formed by curing of the surface treatment liquid are removed while no scratch is generated, and the substances are cleaned; thus, a three-dimensional structure is generated in the printed area by using the surface treatment liquid to form surface textures with a 3D effect, and a formed 3D simulation layer is obtained;

s10, coating 10g/m on the surface of the 3D simulation layer ² And carrying out photocuring treatment on the UV finish paint to form a surface protection layer, thus obtaining the digital printing plate.

Comparative example 2

Essentially the same as in comparative example 1, except that the substrate layer was 3.5mm thick.

Comparative example 3

Essentially the same as in comparative example 1, except that the substrate layer was 4mm thick.

Comparative example 4

Essentially the same as in comparative example 1, except that the substrate layer was 5mm thick.

Comparative example 5

Essentially the same as in comparative example 1, except that the substrate layer was 5.5mm thick.

Comparative example 6

Essentially the same as in comparative example 1, except that the substrate layer was 6mm thick.

Comparative example 7

Essentially the same as in comparative example 1, except that the substrate layer was 7mm thick.

And (3) product testing: respectively producing 50 square plates with the length and width specification of 500mm multiplied by 500mm in batches according to the methods in the comparative examples 1 to 7, observing whether the plates crack and delaminate, measuring the initial warping degree and the heating warping degree of the plates, and counting the product percent of pass, wherein the results are shown in table 1. Wherein, the plates with quality problems observable by naked eyes and the plates with the heating warping degree larger than 1mm/m are marked as unqualified.

Warping degree detection process: cutting the plate into 240mm samples, placing the wear-resistant layer upwards above an aluminum plate, placing for 24h under the conditions of 23 +/-2 ℃ and 50 +/-5% RH, and measuring the initial warping degree of the plate by a caliper; the temperature in the oven was adjusted to 80 ℃, the sample was placed in the oven together with the aluminum plate for 6 hours, then the sample was taken out together with the aluminum plate, placed for 24 hours under conditions of 23 ± 2 ℃ and 50 ± 5% rh, and the thermal warping degree of the plate was measured by a caliper.

The comparative examples 1 to 7 adopt a method for producing a 3D printed board by adopting a scheme of setting an elastic stress layer to form a reverse warping force in the prior art, and the results in Table 1 show that when the thickness of a base material layer is less than 4mm, the product percent of pass is reduced, and the initial warping degree is higher, because the thickness of the base material layer is thinner, in the process of compounding the elastic stress layer on the base material layer, the structural strength of the base material layer is difficult to resist the stress generated by the elastic stress layer and the reverse warping is easy to generate, the thinner the base material layer is, the larger the reverse warping degree is, even the base material layer is cracked, when the thickness of the base material layer is more than 4mm, the product percent of pass can reach 100%, and the warping degree is smaller. Accordingly, the inventors propose that when the thickness of the substrate layer is sufficiently large, the substrate layer can directly resist the stress formed in the 3D printing process without cracking and the warpage is acceptable without providing an elastic stress layer.

Example 1

A preparation method of a digital printing plate comprises the following steps:

s1, mixing PVC resin with coarse whiting and other additives, heating the mixture through a first extruder to form a hot melt, and introducing the hot melt into a mold to form a substrate layer; the base material layer comprises 15 parts of PVC resin, 75 parts of triple superphosphate, 3 parts of plasticizer, 3 parts of compatilizer, 1.5 parts of stabilizer, 1 part of lubricant and 0.5 part of antioxidant;

s2, when the base material layer is not completely cooled and solidified, preheating the prefabricated film and respectively unreeling the prefabricated film to one side of the precursor of the base material layer, and then carrying out online hot-pressing to form a background film layer on the surface of one side of the base material layer so as to obtain a double-layer composite base material; the thickness of the base material layer in the composite base material is 3.0mm, and the thickness of the background film layer is 0.5mm; the background film layer and the elastic stress layer are formed by mixing, extruding and calendaring 2.0 parts of CPE resin, 60 parts of polyvinyl chloride, 0.8 part of polyethylene wax and 4.0 parts of rigid filler; the longitudinal tensile strength of the background film layer is 42.79MPa, the transverse tensile strength is 32.37MPa, the change rate of the longitudinal heating dimension is 4.81 percent, and the change rate of the transverse heating dimension is 1.53 percent;

s3, guiding the composite base material into 2D printing equipment, guiding a pattern to be printed on the 2D printing equipment, setting the size of a plate, setting the height of a printing head, and turning on a vacuum adsorption device, an LED and an ultraviolet curing lamp; printing a required 2D plane pattern on any background film layer of the composite base material obtained in the last step; the color paste of the printed pattern is ultraviolet curing color paste; after printing, the pattern is shaped through the irradiation of an ultraviolet curing lamp to obtain a first printing substrate; the equipment in the step is 2D printing equipment purchased in the market;

s4, after the 2D plane pattern is solidified, coating an abrasion-resistant layer on the SPC base material with the 2D plane pattern by using a roller coater, wherein the abrasion-resistant coating amount is 50g/m & lt 2 & gt, and carrying out ultraviolet curing; the setting of the operation of the illumination intensity is the same as above;

s5, coating a second resin composition on the surface of the wear-resistant layer by using a roll coater to form a pattern simulation layer precursor, wherein in the embodiment, the second resin composition is mainly an oligomer composed of methyl methacrylate and a monomer thereof, and the methyl methacrylate monomer accounts for about 70vol%; allowing a small amount of other monomers or their oligomers to be mixed, such as acrylic acid, methacrylic acid and their oligomers; necessarily containing a small amount of photoinitiator; the coating amount of the second resin composition was 200g/m ² (ii) a Carrying out photocuring treatment by using ultraviolet curing equipment, so that incomplete curing occurs on the first resin layer on the surface when a product passes through the equipment;

s6, selectively spraying surface treatment liquid on the pattern simulation layer precursor at fixed points according to the printing pattern by using 3D printing equipment, and then respectively curing the second resin composition and the surface treatment liquid through ultraviolet curing; in this example, the surface treatment liquid was composed of a photosensitive polymerization inhibitor and a solvent therefor, and the components thereof were 8% of tris (N-nitroso-N-phenylhydroxylamine) aluminum salt and 92% of 2-phenolethoxyacrylate;

s7, removing substances formed by solidifying the surface treatment liquid by using a roller brushing machine; in the process, the hardness of the brush roll steel brush needs to be adjusted, substances formed by curing the surface treatment liquid are removed while no scratch is generated, and the substances are cleaned; then spraying cleaning liquid to remove residual liquid which is remained on the surface and is not solidified due to the surface treatment liquid, and drying; thus, a three-dimensional structure is generated in the printed area by using the surface treatment liquid to form surface textures with a 3D effect, and a formed 3D simulation layer is obtained;

s8, coating 10g/m on the surface of the 3D simulation layer ² And carrying out photocuring treatment on the UV finish paint to form a surface protection layer, thus obtaining the digital printing plate.

Example 2

Essentially the same as in example 1, except that the substrate layer was 3.5mm thick.

Example 3

Essentially the same as in example 1, except that the substrate layer had a thickness of 4mm.

Example 4

Essentially the same as in example 1, except that the substrate layer was 4.5mm thick.

Example 5

Essentially the same as in example 1, except that the substrate layer had a thickness of 5mm.

Example 6

Essentially the same as in example 1, except that the substrate layer had a thickness of 6mm.

The results of testing the product yield and the average warpage of examples 1 to 6 are shown in Table 2. Warpage test method is the same as table 1.

Embodiments 1 to 6 are schemes in which no elastic stress layer is provided, and as can be seen from table 2, when the thickness of the substrate layer is gradually increased from 3mm to 5mm, the yield of the product is gradually increased, and the average warping degree of the product is reduced, and when the thickness of the substrate layer is not less than 5mm, the yield of the product reaches 100%, so that the thickness of the substrate layer is not less than 5mm, the production of the 3D printing plate can be realized without providing an elastic stress layer, which is simpler in comparison with the prior art, and the reverse warping and cracking of the substrate layer caused by the provision of the elastic stress layer are avoided.

Example 7

A preparation method of a digital printing plate comprises the following steps:

s1, mixing PVC resin with coarse whiting and other additives, heating the mixture through a first extruder to form a hot melt, and introducing the hot melt into a mold to form a substrate layer; the base material layer comprises 20 parts of PVC resin, 70 parts of triple superphosphate, 4 parts of plasticizer, 3 parts of compatilizer, 1.5 parts of stabilizer, 1 part of lubricant and 0.5 part of antioxidant;

s2, when the base material layer is not completely cooled and solidified, preheating the prefabricated film and respectively unreeling the prefabricated film to one side of the precursor of the base material layer, and then carrying out online hot-pressing to form a background film layer on the surface of one side of the base material layer so as to obtain a double-layer composite base material; the thickness of the base material layer in the composite base material is 3.0mm, and the thickness of the background film layer is 0.5mm; the background film layer and the elastic stress layer are formed by mixing, extruding and calendaring 2.0 parts of CPE resin, 1 part of EVA resin, 60 parts of polyvinyl chloride, 0.8 part of polyethylene wax and 3.0 parts of rigid filler; the longitudinal tensile strength of the background film layer is 43.42MPa, the transverse tensile strength is 32.56MPa, the change rate of the longitudinal heating dimension is 4.85 percent, and the change rate of the transverse heating dimension is 1.56 percent;

s3, guiding the composite base material into 2D printing equipment, guiding a pattern to be printed on the 2D printing equipment, setting the size of a plate, setting the height of a printing head, and turning on a vacuum adsorption device, an LED and an ultraviolet curing lamp; printing a required 2D plane pattern on any background film layer of the composite base material obtained in the last step; the color paste of the printed pattern is ultraviolet curing color paste; after printing is finished, the pattern is shaped through irradiation of an ultraviolet curing lamp to obtain a first printing substrate; the equipment in the step is 2D printing equipment purchased in the market;

s4, after the 2D plane pattern is cured, coating an abrasion-resistant layer on the SPC base material with the 2D plane pattern by using a roll coater, wherein the abrasion-resistant coating amount is 50g/m & lt 2 & gt, and performing ultraviolet curing; setting the operation of the illumination intensity is the same as that of the operation;

s5, coating a second resin composition on the surface of the wear-resistant layer by using a roll coater to form a pattern simulation layer precursor, which is shown in the embodimentThe second resin composition is an oligomer composed mainly of methyl methacrylate and a monomer thereof, wherein the methyl methacrylate monomer accounts for about 70vol%; allowing a small amount of other monomers or their oligomers to be mixed, such as acrylic acid, methacrylic acid and their oligomers; necessarily containing a small amount of photoinitiator; the coating amount of the second resin composition was 200g/m ² (ii) a Carrying out photocuring treatment by using ultraviolet curing equipment, so that incomplete curing occurs on the first resin layer on the surface when a product passes through the equipment;

s6, selectively spraying surface treatment liquid on the pattern simulation layer precursor at fixed points according to the printing pattern by using 3D printing equipment, and then respectively curing the second resin composition and the surface treatment liquid through ultraviolet curing; in this example, the surface treatment liquid was composed of a photosensitive polymerization inhibitor and a solvent therefor, and its components were 8% of tris (N-nitroso-N-phenylhydroxylamine) aluminum salt and 92% of 2-phenolethoxyacrylate;

s7, removing substances formed by curing the surface treatment liquid by using a roller brush machine; in the process, the hardness of the brush roller steel brush needs to be adjusted, substances formed by curing of the surface treatment liquid are removed while no scratch is generated, and the substances are cleaned; then spraying cleaning liquid to remove residual liquid which is remained on the surface and is not solidified because of the surface treatment liquid, and drying; thus, a three-dimensional structure is generated in the printed area by using the surface treatment liquid to form surface textures with a 3D effect, and a formed 3D simulation layer is obtained;

Example 8

Substantially the same as in example 7 except that the substrate layer was 4mm in thickness.

Example 9

Essentially the same as in example 7, except that the substrate layer had a thickness of 5mm.

Example 10

Basically the same as the embodiment 7, except that the base material layer comprises 25 parts of PVC resin, 65 parts of triple superphosphate, 5 parts of plasticizer, 3 parts of compatilizer, 1.5 parts of stabilizer, 1 part of lubricant and 0.5 part of antioxidant;

example 11

The same as in example 10 except that the thickness of the substrate layer was 4mm.

Example 12

The same as in example 10 except that the thickness of the substrate layer was 5mm.

The results of testing the product yield and the average warpage of examples 7 to 12 are shown in Table 3. Warpage test method is the same as table 1.

In examples 7 to 9 and examples 10 to 12, base material layer schemes different from those in comparative examples 1 to 6 are respectively adopted, the proportions of the PVC resin, the plasticizer and the heavy calcium in the base material layer are changed, and as seen from the results in table 3, the adjustment of the proportions of the PVC resin, the plasticizer and the heavy calcium has no obvious influence on the overall yield trend, and the product yield can be ensured only when the thickness of the base material reaches 5mm, so that a method without an elastic stress layer can be adopted when the thickness of the base material is more than 5mm.

Example 13

A preparation method of a digital printing plate comprises the following steps:

s2, when the base material layer is not completely cooled and solidified, preheating two layers of prefabricated films with the same material and thickness, respectively unreeling the prefabricated films to two side surfaces of the precursor of the base material layer, and then carrying out online hot-pressing to respectively form two sides of the base material layer to obtain a three-layer composite base material; the thickness of the base material layer in the composite base material is 3.0mm, and the thickness of the background film layer is 0.3mm; the background film layer is formed by mixing, extruding and calendaring 2.0 parts of CPE resin, 60 parts of polyvinyl chloride, 0.8 part of polyethylene wax and 4.0 parts of rigid filler; the longitudinal tensile strength of the background film layer is 42.79MPa, the transverse tensile strength is 32.37MPa, the longitudinal heating size change rate is 4.81%, and the transverse heating size change rate is 1.53%;

s5, coating a second resin composition on the surface of the wear-resistant layer by using a roll coater to form a pattern simulation layer precursor, wherein in the embodiment, the second resin composition is mainly an oligomer composed of methyl methacrylate and a monomer thereof, and the methyl methacrylate monomer accounts for about 70vol%; allowing a small amount of other monomers or their oligomers, such as acrylic acid, methacrylic acid and their oligomers to be mixed; necessarily containing a small amount of photoinitiator; the coating amount of the second resin composition was 200g/m ² (ii) a Carrying out photocuring treatment by using ultraviolet curing equipment, wherein the illumination intensity or the passing time is properly reduced, so that the first resin layer on the surface is not completely cured when the product passes through the equipment; such as adjusting the illumination intensity down to 0.8 times the original intensity or setting the transit time to 0.8 times the original intensity;

s7, removing substances formed by solidifying the surface treatment liquid by using a roller brushing machine; in the process, the hardness of the brush roll steel brush needs to be adjusted, substances formed by curing the surface treatment liquid are removed while no scratch is generated, and the substances are cleaned; then spraying cleaning liquid to remove residual liquid which is remained on the surface and is not solidified because of the surface treatment liquid, and drying; thus, a three-dimensional structure is generated in the printed area by using the surface treatment liquid, and surface textures with a 3D effect are formed, so that a formed 3D simulation layer is obtained;

Example 14

S1, mixing PVC resin with heavy calcium carbonate and other additives, heating the mixture through a first extruder to form a hot melt, and introducing the hot melt into a mold to form a base material layer precursor; the base material layer comprises 20 parts of PVC resin, 70 parts of triple superphosphate, 4 parts of plasticizer, 3 parts of compatilizer, 1.5 parts of stabilizer, 1 part of lubricant and 0.5 part of antioxidant;

s2, when the base material layer is not completely cooled and solidified, heating the background film layer raw material through a second extruder to form a second melt, introducing the second melt into a mold to enable the second melt to coat the decorative surface of the precursor of the base material layer, then heating the elastic stress layer raw material through a third extruder to form a third melt, introducing the third melt into the mold to enable the third melt to coat the basal surface of the precursor of the base material layer, and cooling and shaping to obtain a three-layer composite base material; the thickness of the base material layer in the composite base material is 3.0mm, and the thickness of the background film layer is 0.3mm; the background film layer and the elastic stress layer are respectively mixed, extruded and formed by 2.0 parts of CPE resin, 60 parts of polyvinyl chloride, 0.8 part of polyethylene wax and 4.0 parts of rigid filler; the longitudinal tensile strength of the background film layer is 42.79MPa, the transverse tensile strength is 32.37MPa, the change rate of the longitudinal heating dimension is 4.81 percent, the change rate of the transverse heating dimension is 1.53 percent, and the molding shrinkage rate is 0.62 percent;

s4, after the 2D plane pattern is solidified, coating an abrasion-resistant layer on the SPC base material with the 2D plane pattern by using a roller coater, wherein the abrasion-resistant coating amount is 50g/m & lt 2 & gt, and carrying out ultraviolet curing; setting the operation of the illumination intensity is the same as that of the operation;

s7, removing substances formed by solidifying the surface treatment liquid by using a roller brushing machine; in the process, the hardness of the brush roller steel brush needs to be adjusted, substances formed by curing of the surface treatment liquid are removed while no scratch is generated, and the substances are cleaned; then spraying cleaning liquid to remove residual liquid which is remained on the surface and is not solidified because of the surface treatment liquid, and drying; thus, a three-dimensional structure is generated in the printed area by using the surface treatment liquid, and surface textures with a 3D effect are formed, so that a formed 3D simulation layer is obtained;

Example 15

Substantially the same as in example 13 except that the substrate layer was 3.5mm in thickness.

Example 16

Essentially the same as in example 13, except that the substrate layer had a thickness of 4mm.

Example 17

Essentially the same as in example 13, except that the substrate layer was 4.5mm thick.

The results of testing the product yields and the average warpage of examples 13 to 17 are shown in Table 4. Warpage testing methods are the same as table 1.

It can be seen from table 4 that by arranging the background film layer and the elastic stress layer which are made of the same material and have the same thickness on the two side surfaces of the base material layer, and then performing 3D printing on the composite base material, the yield of the base material with the thickness of less than 5mm can reach the standard. In the scheme of the invention, because the two sides of the composite base material are basically balanced in stress, the problem of easy reverse warping in sequence in the prior art is avoided, meanwhile, the elastic stress layers and the background film layers on the two sides provide toughness for the base material layer, so that the base material layer is not easy to crack, and when the base material layer is influenced by stress in the 3D printing process, the elastic stress layers can also form internal tension to resist warping. From the perspective of the heating warping degree, compared with the scheme of only arranging the single-sided background film layers in embodiments 1 to 12, the double-sided background film layers are arranged, so that one of the background film layers serves as an elastic stress layer, and the heating warping degree of the product can be reduced to a certain extent, because the two background film layers can synchronously generate volume changes in the heating process.

In summary, according to the digital printing plate with high yield and the production method thereof, which are obtained by the product with the structure of "elastic stress layer-substrate layer-background layer-3D resin layer" in the prior art and the product yield and warping degree data in actual production, specifically, when the thickness of the substrate is more than 5mm, the basic structure of the digital printing plate is "substrate layer-background film layer-3D resin layer", and when the thickness of the substrate is less than 5mm, the basic structure of the digital printing plate is "elastic stress layer (background film layer) -substrate layer-background film layer-3D resin layer".

The above embodiments are merely illustrative and not restrictive, and those skilled in the art can modify the embodiments without inventive contribution as required after reading this specification, but the invention is protected by the claims only.

Claims

1. A digital printing plate is characterized in that: the decorative film comprises a base material layer mainly composed of hot-melt first resin and filler, a background film layer, a 2D pattern layer and a 3D simulation layer, wherein the background film layer is compounded with the decorative surface of the base material layer into a whole, the 2D pattern layer is arranged on the surface of the background film layer, and the 3D simulation layer is covered on the 2D pattern layer and mainly composed of second resin; the 3D simulation layer forms a three-dimensional pattern structure with concave and convex parts; the thickness of the base material layer is not less than 5mm.

2. The digital printing plate of claim 1, wherein: the transverse tensile strength of the background film layer is not lower than 25MPa, and the longitudinal tensile strength of the background film layer is not lower than 30MPa.

3. The digital printing plate of claim 2, wherein: the transverse heating size change rate of the background film layer is not more than 2%, and the longitudinal heating size change rate is not more than 6%.

4. A digital printing plate according to claim 3, wherein: the thickness of the background film layer is not more than one fifth of that of the substrate layer.

5. A digital printing plate according to claim 3, wherein: the heat conductivity coefficient of the background film layer is larger than that of the substrate layer.

6. A digital printing plate according to claim 1, wherein: the first resin is polyolefin resin or polyvinyl chloride resin.

7. A digital printing plate is characterized in that: the device comprises a substrate layer mainly composed of first resin and filler, a first background film layer compounded with the decorative surface of the substrate layer into a whole, an elastic stress layer compounded with the basal surface of the substrate layer into a whole, a 2D pattern layer arranged on the surface of the first background film layer, and a 3D simulation layer covering the 2D pattern layer and mainly composed of second resin; the 3D simulation layer forms a three-dimensional pattern structure with concave and convex parts; the thickness of the base material layer is not more than 5mm.

8. The digital printing plate of claim 7, wherein: the elastic stress layer is the same as the first background film layer, and the thickness of the elastic stress layer is not more than one fifth of the thickness of the base material layer.

9. A preparation method of a digital printing plate comprises the following steps:

s2, conveying the prefabricated film to one side surface of the precursor of the base material layer or conveying two layers of prefabricated films to two side surfaces of the precursor of the base material layer respectively, carrying out online hot pressing on the film and the precursor of the base material layer when the precursor of the base material layer is not completely cooled and solidified, and then carrying out sizing treatment to obtain the composite base material containing the film and the base material layer; or heating the raw materials for forming the background film layer or the raw materials for forming the background film layer and the elastic stress layer to form a second melt, introducing the second melt into a mold, coating the second melt on one side surface or two side surfaces of the substrate layer precursor which is not completely cooled, and compounding and shaping the second melt in the mold to obtain a composite substrate comprising the background film layer and the substrate layer or obtain a composite substrate comprising the background film layer, the elastic stress layer and the substrate layer;

s5, applying a surface treatment liquid containing a polymerization inhibitor or a coagulation inhibitor to the surface of the second resin composition according to a pattern shape through a second printing device, curing the second resin composition in a cross-linking polymerization manner to form a 3D simulation layer precursor, and removing the surface treatment liquid or a mixture of the second resin composition and the surface treatment liquid to form a 3D simulation layer with a concavo-convex three-dimensional pattern structure; the anticoagulant is a mixed liquid containing a prepolymer and a monomer which can form a third resin through crosslinking, and the tg value of the third resin is lower than that of the second resin;