Improved method of making flexographic printing plates

Abstract

A method of producing a photocured structure including a backing layer for coupling to a relief image printing plate, or as an integral monolithic structure including a backing layer and a relief image printing layer. The photocured structure can be formed using a continuous liquid interface process or three-dimensional plating to selectively crosslink and cure a photocurable composition. The backing layer can include a grid or a series of openings of a grid, where the arrangement and density of the openings are controlled.

Description

Technical Field

[0001] The present invention relates to a method for fabricating a customizable backing layer for mounting a flexographic embossed image printing plate having a customizable embossed printing plate structure including an integral backing layer. Background Technology

[0002] Flexographic printing is a printing method typically used for high-volume operations. Flexographic printing plates are used to print on a variety of substrates, including paper, paperboard raw materials, corrugated cardboard, film, foil, and laminating materials.

[0003] Flexographic printing plates are raised plates, where the image elements are raised above the opening area. Generally, the plates are slightly flexible enough to wrap around the printing cylinder and durable enough to print over a million copies. These plates offer numerous advantages to printing presses primarily due to their durability and ease of manufacture. Typical flexographic printing plates delivered by their manufacturers are multi-layered products, which sequentially include: a support layer; one or more unexposed photocurable layers; optionally a protective layer or slip film; and usually a protective cover sheet.

[0004] The support layer provides support for the board. The support layer can be formed from transparent or opaque materials such as paper, cellulose film, plastic, or metal. Preferred materials include sheets made from synthetic polymer materials such as polyester, polystyrene, polyolefins, and polyamides. A widely used support layer is a flexible polyethylene terephthalate film.

[0005] Photocurable layers may include any known polymers, monomers, initiators, reactive and / or non-reactive diluents, fillers, and dyes. As used herein, the term "photocurable" refers to a composition that undergoes polymerization, crosslinking, or any other curing or hardening reaction in response to photochemical radiation, resulting in the selective separation and removal of unexposed portions of the material from the exposed (cured) portions to form a three-dimensional textured pattern of the cured material. Examples of such photocurable materials are disclosed in European patent applications 0 456 336A2 and 0 640 granted to Goss et al. U.S. Patents 878A1, 1,366,769, 5,223,375 (Berrier et al.), 3,867,153 (MacLahan), 4,264,705 (Allen), 4,323,636, 4,323,637, 4,369,246, and 4,423,135 (Chen et al.), 3,265,765 (Holden et al.), 4,320,188 (Heinz et al.), 4,427,759 (Gruetzmacher et al.), 4,622,088 (Min), and 5,135,827 (Bohm et al.) are all cited in full hereof.

[0006] Photocurable materials are typically crosslinked (cured) and hardened through free radical polymerization initiated by exposure to photochemical radiation of one or more wavelengths. As used herein, “photochemical radiation” refers to radiation capable of polymerizing, crosslinking, or curing photocurable layers. Photochemical radiation includes, for example, amplified (e.g., laser) and non-amplified light, particularly in the ultraviolet (UV) and violet wavelength ranges. Photochemical radiation sources can include, for example, various types of doped or undoped mercury lamps and bulbs, xenon lamps, visible light sources, light-emitting diodes (LEDs), laser sources, and sunlight.

[0007] The slip film is a thin layer that protects the photopolymer from dust and makes it easier to handle. In conventional (“analog”) plate-making processes, the slip film is largely transparent to UV light at the wavelengths used in the curing process. The printing press peels a cover sheet off the printing plate blank and places a negative on top of the slip film layer. The plate and the negative are then subjected to full exposure to UV light passing through the negative. The areas exposed to light cure or harden, and the unexposed areas are removed (developed) to create a raised image on the printing plate.

[0008] In "digital" or "computer-to-plate" processes, a laser is guided by an image stored in an electronic data file and used to produce an in-situ negative in a digital (i.e., laser-aberable) mask layer. This mask layer is typically a slip film modified to include a radiopaque material. The in-situ negative is produced by ablating portions of the laser-aberable layer by exposing the mask layer to laser radiation at a selected wavelength and power. Examples of laser-aberable layers are disclosed, for example, in U.S. Patent Application 5,925,500 granted to Yang et al., and U.S. Patent Applications 5,262,275 and 6,238,837 granted to Fan, the subject of which is incorporated herein by reference in its entirety.

[0009] The processing steps used to form flexographic printing plates typically include the following steps:

[0010] 1) Image generation, which may include mask ablation of digital “computer-to-plate” printing plates or negative production of conventional analog plates;

[0011] 2) Back exposure to form a base layer and establish texture depth in a photocurable layer;

[0012] 3) By exposing the front side of a mask (or negative), the photocurable layer not covered by the mask is selectively crosslinked and cured, thereby creating a raised pattern.

[0013] 4) Development to remove unexposed photopolymers by solvent (including water) or thermal development; and

[0014] 5) If necessary, perform post-exposure and / or de-adhesion.

[0015] A removable cover sheet can be provided to protect the photocurable printed element from damage during transport and handling. Before processing the printed element, the cover sheet is removed, and the photosensitive surface is exposed to photochemical radiation in an imaging manner. After imaging exposure to photochemical radiation, polymerization occurs in the exposed areas, resulting in the insolubility of the photopolymer layer. The unexposed areas of the photopolymer layer are removed by treatment with a suitable developer solvent (or alternatively, thermal development), leaving a textured surface suitable for flexographic printing.

[0016] As used herein, the term "back exposure" refers to the exposure of the photopolymer layer to photochemical radiation on the side opposite to the side that will actually or ultimately bear the texture. This step is typically accomplished with a transparent support layer and is used to form a shallow layer of photocurable material, i.e., a "baseplate," on the support side of the photocurable layer. The purpose of the baseplate is generally to sensitize the photocurable layer and determine the texture depth.

[0017] Following a brief back exposure step (i.e., brief compared to the subsequent imaging exposure step), imaging exposure is performed by contacting a photocurable layer and passing through a mask or negative that directionally photochemically radiates it.

[0018] The resulting surface has a raised pattern, which typically includes multiple dots that reproduce the image to be printed. After developing the raised image, the resulting flexographic raised image printing element can be mounted on a press and printing can begin.

[0019] As an alternative to sheet polymers, flexographic printing elements can be made from liquid photopolymer resins, offering the following advantages: uncured resin can be recovered from non-image areas of the printing element and used to create additional printing plates. Liquid photopolymer resins also offer additional advantages in flexibility compared to sheet polymers, making it possible to easily produce any desired plate size by simply changing machine settings.

[0020] These plates are typically formed by placing a layer of liquid photopolymerizable resin onto a glass plate, but separating it from the glass plate by a substrate and / or a cover film. Photochemical light (i.e., UV light) is directed through a negative to the resin layer. As a result, the liquid resin is selectively crosslinked and cured to form a printed image surface that mirrors the image on the negative. When exposed to photochemical radiation, the liquid photopolymerizable resin polymerizes and changes from a liquid to a solid state to form a raised, textured image. After this process is complete, the uncrosslinked liquid resin can be recovered (i.e., recycled) from the printed plate and recycled in the process to make additional plates.

[0021] Various methods for preparing printed circuit boards using liquid photopolymer resins have been developed, as described in, for example, U.S. Patent Application 5,213,949 to Kojima et al., U.S. Patent Application 5,813,342 to Strong et al., U.S. Patent Publication Application 2008 / 0107908 to Long et al., and U.S. Patent Application 3,597,080 to Gush, the subject matter of which is incorporated herein by reference in its entirety.

[0022] Typical steps in the liquid metal plate-making process include:

[0023] (1) Casting and exposure;

[0024] (2) Recycling;

[0025] (3) Rinse;

[0026] (4) Post-exposure;

[0027] (5) Drying; and

[0028] (6) Remove the adhesive.

[0029] In the casting and exposure steps, a photographic negative is placed on a glass stage, and a cover film is placed on top of the negative in the exposure unit. All air is then removed by vacuum, allowing any wrinkles in the negative or cover film to be eliminated. A liquid photopolymer layer and a backing sheet (i.e., a thin layer of polyester or polyethylene terephthalate) are then applied on top of the cover film and negative. The backing sheet may be coated on one side to bond with the liquid photopolymer and serves as the back side of the board after exposure. The photopolymer is then exposed to photochemical radiation using upper and / or lower photochemical radiation sources (i.e., UV light) to crosslink and cure the liquid photopolymer layer in areas not covered by the negative. The upper photochemical radiation source is used to form the base layer of the printed board (i.e., back exposure), while the lower photochemical radiation source is used to expose the front side of the photopolymer to photochemical radiation through the negative, thereby producing a raised image.

[0030] After exposure is complete, the printing plate is removed from the exposure unit, and the unexposed photopolymer under photochemical radiation (i.e., the photopolymer covered by the negative) is recovered for further use. This "recovery" step typically involves scraping, vacuuming, or otherwise removing the liquid photopolymer remaining on the surface of the printing plate.

[0031] Stereolithography is another process used to create embossed printed plates and involves additive layering. Each layer of photopolymer is cured, peeled off, refilled with more resin, cured again, and the process is repeated until the desired thickness and plate properties are achieved.

[0032] Three-dimensional printing has also been proposed for producing raised-texture images on printing plates, as described, for example in U.S. Patent 10,429,736 to Bryant et al., the entire subject matter of which is incorporated herein by reference.

[0033] The use of a compressible embossed printing plate, or alternatively, mounting the embossed printing plate on a compressible backing layer that allows the layer to deform and compress. An alternative method involves making the printing plate more flexible, which can lead to undesirable character growth under the required printing pressure, particularly when printing on rough or uneven raw materials or on presses with uneven impression and / or plate cylinders.

[0034] Compressible embossed printing plates and / or compressible backing layers have found good practicality, particularly in printing on corrugated materials or similar substrates with uneven, deformable surfaces. With such substrates, the printing plate must be flexible enough to adapt to the uneven surface and deliver an ink coating evenly. However, if the plate is too soft or flexible, the image on it will deform under the pressure used to bring the plate into contact with the substrate, and therefore the image cannot be transferred with the desired fidelity.

[0035] Compressible printing plates can also be used for:

[0036] a) Printing on wide-width sheets (films of cellophane, polyethylene, polypropylene, polyester, vinyl and paper with a sheet thickness in the range of about 0.5 mil to 5 mil) to overcome sagging and deformation caused by the compressibility of foam and machine spacing variations.

[0037] b) Print security paper (in the form of checks, bonds, and stocks) in a uniform, constant tone during back-end printing; and

[0038] c) Color overprinting (4-color printing), where uniform ink deposition is crucial for proper color development.

[0039] Compressible printing plates also have a longer lifespan. During each printing cycle, the mechanical impact on the plate causes gradual wear of the embossed surface, leading to a gradual loss of print clarity. The compressible layer absorbs the mechanical impact, keeping the embossed printing surface relatively unaffected (with minimal flattening or deformation), thus resulting in a longer plate lifespan.

[0040] During the printing process, high-rigidity (i.e., hard) boards themselves can often damage deformable substrates. However, a higher-rigidity board combined with a compressible substrate layer can potentially solve both problems. In this way, a fairly hard board that will not provide a distorted image can be used, and the compressibility of the backing layer can be utilized to allow the board to bend and flex, thereby reaching all areas of the uneven substrate.

[0041] A typical compressible layer consists of a foam material (usually polyurethane or other thermoplastic materials) that can be laminated to the back of a cured printed plate carrying an image using tape or other pressure-sensitive adhesive.

[0042] A persistent problem is the difficulty in securing the backing material (i.e., the compressible foam layer) to the back of the board. It is also difficult to apply the adhesive evenly. Furthermore, the foam material exhibits the problem of stretching during installation onto the board and, if stable, causing buckling when the board flexes.

[0043] In many cases, the printing plate has already been fully exposed and developed before the compressible layer is attached to it. The compressible layer is formed in a separate step and then pretreated with an adhesive or some type of bonding coating to laminate the compressible layer to the printing plate.

[0044] Examples of backing materials are described, for example, in U.S. Patent 3,903,794 to Grupe et al., U.S. Patent 4,303,721 to Rodriguez, U.S. Patent 4,574,697 to Feeley, and U.S. Patent 5,325,776 to Rather, Sr. et al., the subject of each of which is incorporated herein by reference in its entirety.

[0045] However, many of these existing composite and foam materials lack deformability, or if they are easily deformable, they lack sufficient elasticity to spring back to their original size quickly and repeatedly.

[0046] To compensate for these problems, the current practice is to use composite materials and foam materials to print the screen portion of the reproduced copy, but not the solid portion, because they lack sufficient density and thickness accuracy to reproduce the solid portion without a granular or incomplete (snowflake) appearance. Additionally, these composite materials can be difficult to construct.

[0047] Therefore, there remains a need in the art for improved customizable compression backing layers for flexible raised image printing plates to overcome the deficiencies of the prior art. Summary of the Invention

[0048] The object of this invention is to provide an improved backing layer for flexographic printing plates.

[0049] Another objective of this invention is to simplify the process of manufacturing the backing layer.

[0050] Another object of the present invention is to provide a customizable backing layer for flexographic printing plates.

[0051] Another object of the present invention is to provide a customizable backing layer with a grid structure.

[0052] Another object of the present invention is to produce such customizable backing layers using a continuous liquid interface 3D manufacturing method.

[0053] Another object of the present invention is to produce a structure as an integral configuration comprising a customized backing layer and a textured image printing layer made of the same photocurable composition.

[0054] Another object of the present invention is to use a 3D production method to produce customizable backing layers, wherein the physical and chemical properties of the backing layers formed in situ are customized to achieve the beneficial properties of the printed circuit board during printing, manufacturing and / or storage.

[0055] Another object of the present invention is to customize the physical and chemical properties of the in-situ formed backing layer by selectively altering the properties of the cured photopolymer or by gradient altering the properties of the cured photopolymer according to the depth or location in the backing layer by changing the composition of the photocurable composition and / or the curing conditions during the formation of the backing layer.

[0056] Therefore, in one embodiment, the present invention relates to a method for fabricating photocurable structures via continuous liquid interface printing, the method comprising the following steps:

[0057] a) Providing a liquid photocurable composition in a reservoir, wherein the photocurable composition comprises:

[0058] i) Adhesive resin;

[0059] ii) one or more monomers; and

[0060] iii) Photoinitiator package;

[0061] The reservoir includes a transparent bottom, and a photochemical radiation source is positioned to irradiate the transparent bottom with photochemical radiation, thereby selectively crosslinking and curing the liquid photocurable composition; and

[0062] b) Provide a carrier plate including the substrate on a substrate, wherein the substrate provides a surface on which a structure is formed, wherein the reservoir is below the carrier plate;

[0063] c) Contacting the substrate with a liquid photocurable composition in a reservoir;

[0064] d) Selectively expose the liquid photocurable composition to photochemical radiation below the transparent bottom of the reservoir, wherein the photochemical radiation crosslinks and cures selected areas of the liquid photocurable composition in the reservoir.

[0065] e) Moving the carrier plate away from the reservoir while photochemical radiation continuously crosslinks and cures the photocurable composition, thereby forming a photocurable structure on the carrier plate while it is being removed from the reservoir. Detailed Implementation

[0066] This invention relates to an improved method for fabricating a customized compressible backing layer for flexographic printing plates using a continuous liquid interface additive manufacturing method. Furthermore, this invention also relates to a method for fabricating a customized backing layer and a textured printing layer structure as an integrated configuration.

[0067] By using additive manufacturing, and in a preferred embodiment, 3D printing, the inventors of this invention have discovered that it is possible to produce backing layers comprising a mesh structure, wherein both the hardness of the material and the density of the mesh can be controlled to produce an optimal backing layer for a variety of printed circuit boards. Therefore, mesh structures combined with the physical properties of the resin can be combined to produce optimized and customized backing layers that possess the desired properties of compressibility, modulus, and mobility for a specific application.

[0068] Compared to existing backing layers using adhesive foams or solids, the present invention provides a method for customizing the compressibility of different regions of a board with varying densities based on the specific requirements of the printed circuit board. For example, within a single board, the backing layer may include both solid regions and high-resolution areas to produce a 3D-printed backing layer with optimized regions that mirror the embossed image features of the printed circuit board.

[0069] The target properties of the backing layer can be matched to the existing foam or tape properties, which can vary depending on the application. For example, different properties may be required, and therefore can be optimized for printed corrugated boards versus thinner board applications. In other words, the same photocurable composition can be used to create different target properties in the backing layer and produce custom backing layers for the feature portions of embossed image printing plates that are mirrored on them.

[0070] The properties of the backing layer are primarily controlled by printability, including solid density and dot gain. Because this structure is unique, the target properties can vary depending on the aforementioned existing materials.

[0071] The macroscopic target properties of the backing layer are dual. First, the initial UV-curable resin is additively formed into a cured photopolymer, and then, for the resulting mesh structure. The resulting physical property variables include: resin properties, including hardness, modulus, tensile strength, and elongation; UV curing conditions, including temperature, lamp type selection, curing wavelength, emissivity, and total energy density; post-curing technology; mesh layer thickness; and the mesh structure itself, including density and structure.

[0072] Several options exist for the backing layer described herein, including an integrated grid substrate and plate surface structure, as well as a separate grid substrate that can be joined or applied to various plate structures in a suitable manner.

[0073] The hardness and density of the backing layer can be adjusted during additive manufacturing by regulating the curing time and duration of the compressible material. The properties of the compressible material in the backing layer can be optimized to produce the desired compressibility.

[0074] In one embodiment of the invention, the chemical and resulting physical properties of the cured photopolymer composition constituting the backing layer are controlled and vary according to the XY position in the plane of the backing layer and / or the Z position orthogonal to the plane of the backing layer (i.e., according to the depth / height in the layer). The property differences can be sequentially located within the backing layer as a continuous or discontinuous series of sublayers and / or sequentially located across the plane of the backing layer or across a continuous gradient of thickness.

[0075] The present invention envisions one or more methods for controlling the composition of a backing layer based on a position within or orthogonal to the plane, which is achieved by changing the composition of the photocurable material over time during an additive manufacturing process.

[0076] The present invention also envisions one or more methods for controlling the properties of a photocurable structure, the photocurable structure comprising a backing layer and / or an integral configuration, achieved by varying curing conditions according to the XY and / or Z positions within the photocurable structure. Such curing conditions may include variables, such as:

[0077] a) The type and / or wavelength of the photochemical radiation source used to achieve crosslinking and curing of the photocurable composition;

[0078] b) Emissivity (intensity) of photochemical radiation;

[0079] c) Energy density (dose) of photochemical radiation;

[0080] d) Exposure type, including full film, moving bed, or moving light source;

[0081] e) Ambient gas conditions (i.e., the oxygen content in the ambient air);

[0082] f) The temperature of the photocurable composition; and

[0083] g) Pre-curing and / or post-curing of photocurable compositions.

[0084] Other variables will also be known to those skilled in the art and can be optimized and controlled to achieve the chemical and / or physical properties of the photocurable structure.

[0085] In a preferred embodiment, the macroscopic design of the grid including the backing layer can be continuous (e.g., isotropic) in the XY plane of the backing layer and in the Z vertical direction of the backing layer (i.e., across the thickness). This type of embodiment can include a backing layer similar to an isotropic foam layer, which is formed by the additive manufacturing process.

[0086] Other preferred embodiments of the invention optionally include one or more backing layers, wherein the macroscopic structure of the mesh may be anisotropic in the XY plane of the backing layer and / or in the Z-direction of the backing layer. In one example of such an embodiment, the size and density of the pores in the microporous backing layer may systematically vary across the thickness of the backing layer, thereby providing a more rigid outer layer and a more flexible top layer attached to the textured layer. In yet another example of such an embodiment, the backing layer may include an array of vertical pillars, wherein the shape, number, and / or diameter of the pillars may vary depending on their location across the thickness of the backing layer.

[0087] In another embodiment of the invention, the density, structure, and composition of the backing layer can be customized across the XY plane of the backing layer. For example, the front edge, rear edge, and / or side edges of the board backing can be designed to have more or less durability and / or elasticity to customize energy absorption / dissipation at portions of the board subjected to higher mechanical impact during the printing process.

[0088] The surface of the cushioning backing layer may include continuous portions and perforated, textured portions that may be a grid structure. Other surface configurations may include protrusions, and the cushioning backing layer may be mounted such that the protrusions engage the bottom of the flexographic printing plate, or conversely, such that the protrusions engage the surface of the printing cylinder. In one embodiment, the protrusions engage the surface of the printing cylinder and are substantially opposite to the surface of the flexographic printing plate.

[0089] In one embodiment and as described herein, the present invention relates to an improved method for fabricating a compressible backing layer for a flexographic embossed image printing plate using a continuous liquid interface method. Therefore, in one embodiment, the present invention generally relates to a method for fabricating a photocurable structure by continuous liquid interface printing, the method comprising the steps of:

[0090] a) Providing a liquid photocurable composition in a reservoir, wherein the photocurable composition comprises:

[0091] i) Adhesive resin;

[0092] ii) one or more monomers; and

[0093] iii) Photoinitiators;

[0094] The reservoir includes a transparent bottom, and a photochemical radiation source is positioned to irradiate the transparent bottom with photochemical radiation, thereby selectively crosslinking and curing the liquid photocurable composition; and

[0095] b) Provide a carrier plate including the substrate on a substrate, wherein the substrate provides a surface on which a structure is formed, wherein the reservoir is below the carrier plate;

[0096] c) Contacting the substrate with a liquid photocurable composition in a reservoir;

[0097] d) Selectively expose the liquid photocurable composition to photochemical radiation below the transparent bottom of the reservoir, wherein the photochemical radiation crosslinks and cures selected areas of the liquid photocurable composition in the reservoir.

[0098] e) Moving the carrier plate away from the reservoir while photochemical radiation continuously crosslinks and cures the photocurable composition, thereby forming a photocurable structure on the carrier plate while it is being removed from the reservoir.

[0099] Continuous liquid interface manufacturing processes are additive manufacturing methods that use photopolymerization to produce solid objects. Alternatively, the continuous liquid interface method described herein can be used to produce integrated backing layer and embossed image printing plate structures by adjusting the properties of the photocurable composition during curing to produce both the unique structure of the backing layer and the textured structure of the embossed image printing layer.

[0100] The continuous process begins with a reservoir of liquid photopolymer, the bottom of which is transparent to photochemical radiation. First, a carrier plate (on which a flexographic printing plate is to be constructed) is brought into direct contact with the liquid photocurable composition, and then a backing layer (or an integrated structure including a backing layer and a textured printing layer) is removed from the reservoir during polymerization. A photochemical radiation source irradiates through the transparent bottom of the reservoir, selectively crosslinking and curing the liquid photocurable resin to form the desired structure. As the photocured structure selectively forms at the bottom of the reservoir, the carrier plate moves away from the bottom of the reservoir to move the photocured structure. The liquid photocurable composition continues to polymerize at the bottom of the reservoir until the photocured structure is fully formed.

[0101] The bottom of the reservoir includes a surface that is semi-permeable to polymerization inhibitors present in the photocurable composition. A gradient is formed within the reservoir, wherein solid material resulting from crosslinking of the photocurable composition at least partially overlaps with non-polymerized material. There are no sharp interfaces in the reservoir defined by the amount of polymerization reaction that has occurred and the amount of uncured photocurable composition.

[0102] The reservoir is substantially stationary or at rest, while the carrier plate moves away from the reservoir during the production of the photocurable structure. Being substantially stationary or at rest means that only minute movements are possible that will not interfere with the continuous production of the photocurable composition during the production of the photocurable structure. If disturbed, however, division lines may form, although polymerization can continue. This may be desirable in the production of, for example, an integral photocurable structure comprising a backing layer and a textured image printing layer. Therefore, predetermined division lines can be formed at locations deemed desirable before further continuous formation can proceed.

[0103] The photochemical radiation source is located below the reservoir and irradiates the transparent bottom of the reservoir. Any conventional photochemical radiation source can be used for this crosslinking and curing of photocurable compositions, including, for example, carbon arcs, mercury vapor arcs, fluorescent lamps, electron flash units, LEDs, and photographic floodlights. Although less common, electron beams or other ionizing radiation sources may optionally be used alone or in combination with UV / visible radiation sources to cure photocurable compositions.

[0104] The formation of the polymeric material on the surface of the carrier plate is continuous, and the polymeric material remains in contact with the photocurable composition in the reservoir until the structure is formed. As described above, the resulting photocurable structure can be a backing layer optimized in the manner described above, such as including a grid structure with a desired pattern and density. Alternatively, the resulting photocurable structure can be an integrated configuration including a backing layer and an overall embossed image printing structure. Additionally, optionally but preferably, the photocurable structure can include a base layer that establishes a embossed depth between the backing layer and the embossed image printing structure, and the structure, properties, and thickness of the base layer can be optimized in the manner described above.

[0105] In one embodiment, the backing layer includes a grid or a series of openings to provide a compressible or resilient backing layer. The shape and size of the openings in the grid, as well as the location and density of the openings that make up the backing layer within the grid, can be controlled to achieve the desired result.

[0106] Photocurable compositions typically comprise one or more resins, binders and / or plasticizers, as well as one or more photoinitiators and one or more polymerization inhibitors. In one embodiment, the photocurable composition is optimized to produce or control an integrated structure of a mesh backing layer and a textured printing layer. In this case, the photocurable composition is selected such that its properties are optimized for suitability as both a mesh backing layer and a textured image printing layer.

[0107] The resins suitable for use in this invention are generally addition-polymerizable olefinically unsaturated compounds. The photocurable compositions may comprise a single resin or a mixture of resins, and the resins are generally reactive monomers, particularly acrylates and methacrylates. Such reactive monomers include, but are not limited to, trimethylolpropane triacrylate, hexanediol diacrylate, 1,3-butanediol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol (200) diacrylate, tetraethylene glycol diacrylate, triethylene glycol diacrylate, pentaerythritol tetraacrylate, tripropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, trimethylolpropane triacrylate, bis(trimethylolpropane) tetraacrylate, and triacrylates of tri(hydroxyethyl)isocyanurate. Dipentaerythritol hydroxypentaacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol (200) dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol (600) dimethacrylate, 1,3-butanediol dimethacrylate, ethoxylated bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, diethylene glycol dimethacrylate. 1,4-Butanediol diacrylate, diethylene glycol dimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, trimethylolpropane dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol diacrylate, urethane methacrylate, or acrylate oligomers, etc., can be added to photopolymerizable compositions to modify the cured product. Monoacrylates, including, for example, cyclohexyl acrylate, isobornyl acrylate, lauryl acrylate, and tetrahydrofurfuryl acrylate, and their corresponding methacrylates, can also be used in the practice of this invention. In some embodiments of this invention, one or more other olefinically unsaturated monomers and / or oligomers, including, for example, monomers selected from the following types: vinyl esters, vinyl ethers, N-vinylamides, maleimides, fumarates, maleates, and other types known to those skilled in the art. Generally preferred, one or more resins are present in an amount of at least 20% by weight of the photocurable composition.

[0108] Binders such as acrylic copolymers, polyolefins, styrene block copolymers, and other polymers known to those skilled in the art can also be used in the compositions of the present invention. Specific suitable binder materials include natural or synthetic polymers and copolymers of conjugated dienes, including 1,2-polybutadiene, 1,4-polybutadiene, butadiene / acrylonitrile, butadiene / styrene, and thermoplastic elastomer block copolymers, such as styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, etc. Generally, it is preferred that the styrene block copolymer is present in an amount of at least 5% by weight of the photocurable composition.

[0109] In one embodiment, the adhesive resin is functionalized with polymerizable moieties distributed or randomly along the polymer or oligomer backbone. In this case, the adhesive resin comprises copolymers based in whole or in part on acrylates, methacrylates, styrene, isoprene, butadiene, vinyl acetate, maleate, fumarate, maleimide, vinyl ether, N-vinylamide, and vinyl esters, wherein polymerizable double bonds are side-attached to the copolymer chain.

[0110] Functionalized binder resins are used as reactive plasticizers, compatibilizers, and / or polymerizable matrix components in photocurable compositions. Additionally, when functionalized binder resins are used in one or more photocurable structures, the one or more layers are selected from the group consisting of: embossed layers, substrate layers, and backing layers.

[0111] The photocurable composition may also optionally contain a compatible plasticizer. Suitable plasticizers include, but are not limited to, dialkyl phthalates, alkyl phosphates, polyethylene glycol, polyethylene glycol esters, polyethylene glycol ethers, polybutadiene, polybutadiene-styrene copolymers, hydrogenated heavy naphthenic oils, hydrogenated heavy paraffin oils, and polyisoprene. Other available plasticizers include oleic acid, lauric acid, etc. If used, the plasticizer is typically present in an amount of at least 5% by weight based on the total solids weight of the photocurable composition.

[0112] Photoinitiators used in photocurable compositions include benzoin alkyl ethers, such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether. Another class of photoinitiators is dialkoxyacetophenone, such as 2,2-dimethoxy-2-phenylacetophenone and 2,2-diethoxy-2-phenylacetophenone. Yet another class of photoinitiators are aldehyde and ketone carbonyl compounds having at least one aryl nucleus directly linked to a carboxyl group. These photoinitiators include, but are not limited to, benzophenone, acetophenone, o-methoxybenzophenone, acenaphthoquinone, methyl ethyl ketone, pentobenzophenone, hexabenzophenone, α-phenylbutanedione, p-morpholinoacetophenone, dibenzo[a]sulfoxide, 4-morpholinobenzophenone, 4'-morpholinodeoxybenzoin, p-diacetylphenyl, 4-aminobenzophenone, 4'-methoxyacetylacetone, benzaldehyde, α-tetrahydronaphthone, 9-acetylbenzophenanthrene, and 2-acetylphenanthrene. Examples of photoinitiators include 10-thioxanthone, 3-acetylphenanthrene, 3-acetylindenone, 9-fluorenone, 1-indenone, 1,3,5-triacetylphenylene, 9-thioxanthone, 9-xanthine, 7-H-benzo[de]-anthracene-7, 1-naphthaldehyde, 4,4-dimethylamino)benzophenone, fluoren-9, 1'-acetylnaphthone, 2'-acetylnaphthalene, 2,3-butanedione, acetylnaphthalene, benzo[a]anthracene 7,12-dione, etc. Phosphine, such as triphenylphosphine and tris(tolyl)phosphine, can also be used as photoinitiators. Both free radical and cationic photopolymerization initiators can be used. Generally, it is preferred that the photoinitiator is present in an amount of at least 0.1% by weight of the photocurable composition.

[0113] In some embodiments, hydrogen atom donor synergists can be used to improve the efficiency of photoinitiators. Such synergists known to those skilled in the art include, but are not limited to, amines, amides, alkyl ethers, thioethers, thiols, and others.

[0114] In some implementations, the photosensitizer may be used in combination with one or more photoinitiators to improve the efficiency of certain photoinitiators when exposed to specific photochemical radiation wavelengths.

[0115] In one embodiment, the photocurable composition comprises a polymerization inhibitor. Polymerization inhibitors used in the photocurable composition include, for example, p-methoxyphenol, hydroquinone and alkyl and aryl-substituted hydroquinones and quinones, tert-butylcatechol, pyrogallol, copper resin, naphthylamine, β-naphthol, cuprous chloride, 2,6-di-tert-butyl-p-cresol, butylated hydroxytoluene (BHT), oxalic acid, phenothiazine, pyridine, nitrobenzene and dinitrobenzene, methyl-p-benzoquinone and tetrachlorobenzoquinone. While in some cases it may be desirable to include polymerization inhibitors (such as BHT or similar polymerization inhibitors) in the photopolymerizable composition, care must be taken to use BHT and other similar polymerization inhibitors, and combinations with other additives, only in amounts that do not impair the imaging properties of the photopolymerizable resin. If used, the polymerization inhibitor may be used in the photocurable composition in amounts from about 0.05% by weight to about 5% by weight.

[0116] Various dyes and / or colorants may also be optionally used in the practice of this invention, but the inclusion of dyes and / or colorants is not essential to obtaining the beneficial effects of this invention. Suitable colorants are designated as “window dyes”, which do not absorb photochemical radiation in the spectral region where the initiator present in the composition can be activated. These colorants include, for example, CI109 red dye, methylene violet (CI basic violet 5), and “Luxol”. Solid Blue MBSN (CI Solvent Blue 38), "Phosphogym" Wool Blue BL (CI Acid Blue 59 or CI 50315), "Phosphogym" Wool Blue GL (CI Acid Blue 102 or CI 50320), Victoria Pure Blue BO (CI Basic Blue 7 or CI 42595), Rhodamine 3GO (CI Basic Red 4), Rhodamine 6GDN (CI Basic Red I or CI 45160), 1,1'-Diethyl-2,2'-Iodine Cyanide, Magenta Dye (CI 42510), Acid Green S (CI 44090), Anthraquinone Blue 2GA (CI Acid Blue 58), Solvaperm Red BB (Solvent Red 195), etc.

[0117] Depending on the desired final properties, other additives may be included in the photocurable composition, including antiozonants, fillers or reinforcing agents, UV absorbers, etc. Such additives are generally well known in the art. However, care must be taken to ensure that the use of these other additives does not impair the crosslinking properties of the photocurable composition.

[0118] Suitable fillers and / or reinforcing agents include immiscible, polymeric or nonpolymeric organic or inorganic fillers or reinforcing agents that are substantially transparent and do not scatter photochemical radiation at the wavelengths used to cure the photocurable composition, such as polystyrene, silicone, bentonite, silica, powdered glass, colloidal carbon, and various types of dyes and pigments. The amount of such materials used varies depending on the desired properties of the elastomer composition. Fillers can be used to improve the strength of the elastomer layer, reduce tackiness, and can also be used as colorants.

[0119] The compressible backing layer described herein is produced using a continuous liquid interface 3D method, resulting in a structure with a Shore A hardness between 25 and 95, preferably between about 45 and about 70, and more preferably between about 50 and about 65. The resulting structure also preferably has an elastomer elongation greater than 50%.

[0120] In another embodiment, the present invention also relates throughout to a method for fabricating photocurable structures by three-dimensional printing, the method comprising:

[0121] a) A liquid photocurable composition is provided in the reservoir of a 3D printer, wherein the liquid photocurable composition comprises:

[0122] i) Adhesive resin;

[0123] ii) monomers; and

[0124] iii) Photoinitiators; and

[0125] b) Providing a carrier plate including a substrate, wherein the substrate provides a surface on which the photocurable structure is formed; and

[0126] c) Using a 3D printer, a liquid photocurable composition is printed onto a substrate, and the printed photocurable composition is exposed to photochemical radiation to cure the printed photocurable composition and form a photocurable structure.

[0127] The hardness of the backing layer and the embossed image printing layer is controlled by adjusting the composition of each layer so that these layers have the desired relative hardness after curing. This can be achieved, for example, by controlling the amount of crosslinking that occurs during photopolymerization. The amount of crosslinking in the polymer composition is proportional to its hardness, which can be controlled by selecting or preparing polymers with different degrees of unsaturation. The higher the degree of unsaturation within the polymer composition, the more the polymer will crosslink once cured, and therefore the harder it will be. This and other methods for achieving different degrees of hardness and other desired physical and chemical properties of the cured photopolymer resin, including embossed image flexographic printing plates, are well known to those skilled in the art.

[0128] The photocurable layer of the present invention shall be cross-linked (cured) and thereby hardened in at least some photochemical wavelength regions. As used herein, photochemical radiation is radiation capable of causing chemical changes in the exposed portion. Photochemical radiation includes, for example, amplified (e.g., laser) and non-amplified light, particularly in the ultraviolet and infrared wavelength ranges. The preferred photochemical wavelength range for curing the photocurable material of the present invention is from about 250 nm to about 450 nm, more preferably from about 300 nm to about 400 nm, and even more preferably from about 320 nm to about 380 nm. A suitable photochemical radiation source is a UV lamp, although other sources are generally known to those skilled in the art.

[0129] The photocurable structure described herein can be processed as is typically done with conventional liquid photopolymers, including steps such as recovery, rinsing, post-exposure, drying, and finishing to remove the unexposed photopolymer layer.

[0130] In one embodiment, the thickness of the backing layer is between about 0.015 inches and about 0.125 inches, and the thickness of the integrated structure including the backing layer and the embossed image printing layer is between about 0.045 inches and about 0.250 inches.

[0131] As used in this article, unless the context clearly indicates otherwise, “a,” “an,” and “the” refer to both the singular and plural forms.

[0132] As used herein, the term “about” refers to a measurable value, such as a parameter, quantity, duration, etc., and is intended to include variations of + / -15% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and even more preferably + / -0.1% or less, provided such variations are suitable for implementation in the invention described herein. Furthermore, it should be understood that the values ​​referred to by the modifier “about” are themselves specifically disclosed herein.

[0133] As used herein, for ease of description, spatially relative terms such as “below,” “under,” “lower,” “above,” and “upper” are used to describe the relationship between one element or feature structure and one or more other elements or features structures, as shown in the figure. It should also be understood that the terms “before” and “after” are not intended to be restrictive and are intended to be interchangeable where appropriate.

[0134] As used herein, the term "comprising and / or including" specifies the presence of the described feature structure, integer, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other feature structures, integers, steps, operations, elements, components, and / or groups thereof.

[0135] As used herein, unless otherwise defined for a specific element or compound, the terms "substantially free" or "largely free" mean that a given element or compound cannot be detected by conventional analytical methods using bath analysis familiar to those skilled in the art of metal plating. Such methods typically include atomic absorption spectrometry, titration, ultraviolet-visible analysis, secondary ion mass spectrometry, and other commonly used analytical methods.

[0136] Finally, it should be understood that the following claims are intended to cover all general and specific features of the invention as described herein, as well as all statements of the invention's scope that may fall between them in language.

Claims

1. A method for fabricating photocurable structures via continuous liquid interface printing, the method comprising the following steps: a) Providing a liquid photocurable composition in a reservoir, wherein the liquid photocurable composition comprises: i) One or more adhesive resins; ii) One or more monomers; and iii) Photoinitiators; The photochemical radiation source is used to selectively crosslink and cure the liquid photocurable composition, the reservoir includes a bottom that is transparent to photochemical radiation of a certain wavelength for curing the liquid photocurable composition, and wherein the photochemical radiation source is positioned to irradiate the photochemical radiation through the transparent bottom of the reservoir. as well as b) A carrier plate including a substrate, wherein the substrate provides a surface on which the photocurable structure is formed, and wherein the reservoir is located beneath the carrier plate; c) Contact the substrate with the liquid photocurable composition in the reservoir; d) Selectively exposing the liquid photocurable composition below the transparent bottom of the reservoir to photochemical radiation, wherein the photochemical radiation crosslinks and cures selected areas of the liquid photocurable composition in the reservoir; e) Moving the carrier plate away from the reservoir while the photochemical radiation continuously crosslinks and cures the liquid photocurable composition, thereby forming the photocurable structure on the carrier plate as it is being removed from the reservoir. The photocurable structure includes a backing layer for bonding to the embossed image printing plate, and The backing layer includes a grid or a series of openings to provide a compressible or elastic backing layer, and the grid is optimized to provide the desired properties of compressibility, modulus, and mobility.

2. The method of claim 1, wherein the substrate comprises a cured photopolymer layer on the surface of the substrate on which the photocurable structure is formed.

3. The method of claim 1, wherein the carrier plate transports the photocurable structure away from the reservoir as the cross-linked and cured photocurable composition layer is continuously formed.

4. The method according to claim 1, wherein steps c) and d) are repeated until the formation of the photocured structure is complete.

5. The method of claim 1, wherein the shape and size of the openings in the mesh, as well as the arrangement and density of the openings, are controlled. The backing layer comprises: solid regions, and High-resolution network cable or mesh opening. The high-resolution screen or the mesh opening mirror image can be mounted on the feature portion of the embossed image printing plate.

6. The method of claim 1, wherein the photocurable structure further comprises a textured image printing layer formed on the backing layer, and steps c) and d) are repeated to form both the backing layer and the textured image printing layer. The backing layer comprises: solid regions, and High-resolution network cable or mesh opening. The high-resolution screen or the screen opening mirror image can be mounted on the feature portion of the embossed image printing plate.

7. The method of claim 6, wherein the liquid photocurable composition is optimized to produce both the backing layer and the embossed image printing layer.

8. The method of claim 6, wherein the textured image printing layer comprises a plurality of printing dots.

9. The method of claim 1, wherein the thickness of the backing layer is between 0.015 inches and 0.125 inches.

10. The method of claim 6, wherein the total thickness of the backing layer and the embossed image printing layer is between 0.045 inches and 0.250 inches.

11. The method of claim 1, wherein the liquid photocurable composition further comprises a polymerization inhibitor, wherein the polymerization inhibitor is selected from the group consisting of: p-methoxyphenol, hydroquinone and alkyl and aryl substituted hydroquinones and quinones, tert-butylcatechol, pyrogallol, copper resin, naphthylamine, β-naphthol, cuprous chloride, 2,6-di-tert-butyl-p-cresol, butylated hydroxytoluene (BHT), oxalic acid, phenothiazine, pyridine, nitrobenzene and dinitrobenzene, methyl-p-benzoquinone, tetrachlorobenzoquinone or combinations thereof.

12. The method of claim 1, wherein the photocurable structure includes different properties that vary with the in-plane depth of the layer of the photocurable structure and / or across the thickness of the layer of the photocurable structure.

13. The method of claim 12, wherein the different properties of the photocurable structure are achieved by changing the formulation composition in the reservoir during the process of making the photocurable structure.

14. The method of claim 1, wherein the photocurable structure comprises controlled chemical and / or physical properties that vary with the position of the photocurable structure in the XY plane and / or across the Z direction of the photocurable structure, wherein such control is established by varying one or more curing condition variables selected from the group consisting of: The type and / or wavelength of the photochemical radiation source used to achieve crosslinking and curing of the liquid photocurable composition; The emissivity of the photochemical radiation; The energy density of the photochemical radiation; Exposure types include full film, moving bed, or moving light source; The temperature of the liquid photocurable composition; and Pre-curing and / or post-curing of the liquid photocurable composition.

15. The method of claim 14, wherein different cured photopolymer properties are achieved by a discontinuous or continuous gradient across the XY plane of the layer of the photocurable structure or across the Z thickness.

16. The method of claim 14, wherein different cured photopolymer properties are achieved by a segment or block pattern spanning the XY plane of the layer of the photocurable structure or spanning the Z thickness.

17. The method of claim 1, wherein the adhesive resin is functionalized with polymerizable portions distributed or randomly along the polymer or oligomer backbone.

18. The method of claim 1, wherein the adhesive resin comprises, in part or in whole, a copolymer based on acrylates, methacrylates, styrene, isoprene, butadiene, vinyl acetate, maleate, fumarate, maleimide, vinyl ether, N-vinylamide, and vinyl esters, wherein polymerizable double bonds are attached to the copolymer chain.

19. The method of claim 18, wherein the functionalized binder resin is used as a reactive plasticizer, compatibilizer, and / or polymerizable matrix component in the liquid photocurable composition.

20. The method of claim 19, wherein the functionalized adhesive resin is used in one or more layers of the photocurable structure, wherein the one or more layers are selected from the group consisting of: a textured image printing layer, a substrate layer, and a backing layer.

21. A method for fabricating photocurable structures by three-dimensional printing, the method comprising the following steps: a) A liquid photocurable composition is provided in a reservoir of a 3D printer, wherein the liquid photocurable composition comprises: i) Adhesive resin; ii) Monomers; and iii) Photoinitiators; and b) Provides a carrier plate including a substrate, wherein the substrate provides a surface on which the photocurable structure is formed; as well as c) Using the aforementioned 3D printer, the liquid photocurable composition is printed onto the substrate, while the printed liquid photocurable composition is exposed to photochemical radiation to cure the printed liquid photocurable composition and form the photocured structure. The photocurable structure includes a backing layer for bonding to the embossed image printing plate, and The backing layer includes a grid or a series of openings to provide a compressible or elastic backing layer, and the grid is optimized to provide the desired properties of compressibility, modulus, and mobility.

22. The method of claim 21, wherein the substrate comprises a cured photopolymer layer on the surface of the substrate on which the photocurable structure is formed.

23. The method of claim 21, wherein the shape and size of the openings in the mesh, as well as the arrangement and density of the openings, are controlled. The backing layer comprises: solid regions, and High-resolution network cable or mesh opening. The high-resolution screen or the mesh opening mirror image can be mounted on the feature portion of the embossed image printing plate.

24. The method of claim 21, wherein the photocurable structure further comprises a textured image printing layer formed on the backing layer, and the steps are repeated to form both the backing layer and the textured image printing layer. The backing layer comprises: solid regions, and High-resolution network cable or mesh opening. The high-resolution screen or the screen opening mirror image can be mounted on the feature portion of the embossed image printing plate.

25. The method of claim 24, wherein the liquid photocurable composition is optimized to produce both the backing layer and the embossed image printing layer.

26. The method of claim 24, wherein the textured image printing layer comprises a plurality of printing dots.

27. The method of claim 21, wherein the thickness of the backing layer is between 0.015 inches and 0.125 inches.

28. The method of claim 24, wherein the total thickness of the backing layer and the embossed image printing layer is between 0.045 inches and 0.250 inches.