On-machine developing type treatment-free CTP plate material capable of resisting damp and hot storage and preparation method of on-machine developing type treatment-free CTP plate material

Abstract

The invention discloses an on-machine developing type treatment-free CTP plate resistant to damp and hot storage and a preparation method of the on-machine developing type treatment-free CTP plate, and belongs to the technical field of printing plate materials. The plate material comprises a plate base and a double-layer coating, wherein a cross-linking layer is a reinforcing layer containing a cross-linking acrylic acid-epoxy copolymer (Tg is more than or equal to 80 DEG C, and the molecular weight is 100,000-300,000), nano silicate and a multifunctional cross-linking agent; and the hydrophobic layer is a protective layer of a hydrophobic modified styrene-maleic anhydride copolymer (the hydrophilic group is reduced by 40-60%) and an ultraviolet absorbent. Through water control of nano silicate, damp-heat deformation resistance of high-Tg resin and multi-layer collaborative design, the storage stability and printing performance of the plate material are remarkably improved. Tests show that after the ink is stored for 6 months at 40 DEG C / 80% RH, the sensitivity attenuation is less than or equal to 5%, the pressrun is greater than or equal to 150,000, the development residual rate is less than or equal to 0.5%, and the ink is suitable for industrial printing in high-humidity and high-heat areas.

Description

Technical Field

[0001] The present invention belongs to the technical field of printing plates, and specifically discloses an on-machine developable and process-free CTP plate capable of storing under humid and hot conditions and a preparation method thereof. Background Art

[0002] After exposure and imaging, the process-free CTP plate can be directly used for printing on the machine without subsequent processing operations such as rinsing and chemical development. According to whether a special developing device is required, it can be divided into process-free CTP plates, chemical-treatment-free CTP plates, simple-treatment CTP plates, and on-machine developing CTP plates. In recent years, the process-free CTP plates have shown significant advantages in terms of environmental protection and cost control, and have gradually become the mainstream technical direction in the printing industry.

[0003] However, the process-free CTP plates still face multiple technical bottlenecks in practical applications. For example, the photosensitive material in the unexposed area is prone to "dark reaction" during storage, resulting in a decrease in sensitivity. The humid and hot environment will exacerbate the degradation of the bonding strength between the coating and the substrate. Specifically, it is manifested as follows: due to the penetration of water molecules under humid and hot conditions, the polymer molecular chain breaks or the cross-linked structure relaxes in the photosensitive layer, directly reducing the mechanical strength of the coating; the developing speed of the plate after storage in a humid and hot environment decreases significantly, and the number of transfer sheets needs to be increased (the number of transfer sheets increases to 20 - 40 after the traditional plate is stored for 6 months), affecting the printing efficiency, etc.; in addition, the protective layer (such as a hydrophilic layer or an oxygen barrier layer) of the double-layer structure plate is prone to moisture absorption and swelling. After moisture absorption, the volume of the coating expands, and the interfacial bonding strength with the aluminum substrate weakens. Scratches or dot wear are also likely to occur during the printing process. At the same time, the scratch resistance of the coating decreases under humid and hot conditions, and the printing endurance is generally lower than 100,000 impressions, which cannot meet the requirements of long-run printing. With the in-depth research, adding antioxidants (such as benzotriazoles) or oxygen barrier layers (such as polyvinyl alcohol films) is used to delay the dark reaction. For example, although the Chinese patent CN201910070878.5 uses nano-styrene monomers and antioxidants to ensure the sensitivity and shelf life of the product, it is difficult to balance scratch resistance and moisture resistance, and cannot completely cure the dark reaction. In high-temperature and high-humidity areas, it cannot prevent the damage of the coating structure caused by the penetration of water molecules; adjusting the proportion of hydrophilic groups of the resin (such as the patent CN113655690B) can improve the developing speed, but it causes the coating to be more prone to moisture absorption in a humid and hot environment, and the storage stability decreases significantly, with limited application scope. Especially in high-temperature and high-humidity areas, it is easy to cause the performance of the process-free CTP plate to decline.

[0004] Based on this, if a CTP plate capable of storing under humid and hot conditions can be designed, it will be beneficial to the development of CTP plate technology. Summary of the Invention

[0005] The invention prepares an on-press development type treatment-free CTP plate material that is resistant to moisture and heat storage, and solves the problems of sensitivity attenuation, on-press development speed reduction and press life reduction during storage.

[0006] In order to achieve the above purpose, the present invention solves the technical problem by adopting the following technical solutions:

[0007] In one aspect, the present invention provides an on-press developable, process-free CTP plate resistant to wet and hot storage, comprising a plate base;

[0008] A cross-linking layer is provided on one surface of the substrate, and the cross-linking layer comprises, by weight, 35-45 parts of a cross-linked acrylic acid-epoxy copolymer, 30-40 parts of a multifunctional acrylate monomer, 2-5 parts of a nano-silicate, 1-2 parts of an infrared absorber, 5-10 parts of a photoinitiator, 0.3-1 parts of a free radical quencher, and 1-5 parts of a multifunctional epoxy cross-linking agent;

[0009] The hydrophobic layer is arranged on the surface of the cross-linked layer facing away from the substrate. The hydrophobic layer comprises, by weight, 20-30 parts of hydrophobically modified styrene-maleic anhydride copolymer, 1-3 parts of infrared absorber, 8-12 parts of photoinitiator, 0.5-2 parts of ultraviolet absorber, and 45-55 parts of hexanediol diacrylate.

[0010] The hydrophobic layer comprises a hydrophobically modified styrene-maleic anhydride copolymer, a UV absorber, and the like. After hydrophobic modification, the hydrophilic group content of the styrene-maleic anhydride copolymer is reduced by 40%-60%, which is lower than the water content of the acrylic acid-epoxy copolymer. This effectively inhibits coating swelling and prevents interfacial peeling. Furthermore, moisture accelerates the slow polymerization (dark reaction) of the photosensitive material in the unexposed area, leading to sensitivity decay. By reducing the water content of the coating, the hydrophobic modification reduces the sensitivity decay rate to ≤5% after 6 months of storage, and the increment in the number of developed plates is controlled within 3 sheets.

[0011] In some embodiments, the substrate is an aluminum substrate.

[0012] In some embodiments, the acrylic-epoxy copolymer has a glass transition temperature Tg≥80° C. and a weight average molecular weight of 100,000-300,000.

[0013] In some embodiments, the nanosilicate is montmorillonite or attapulgite clay.

[0014] In some embodiments, the multifunctional epoxy crosslinking agent is triglycidyl isocyanurate or tetraglycidyl diphenylmethane.

[0015] In some embodiments, the ultraviolet absorber is a benzotriazole compound; and the free radical quencher is an oxime ester compound.

[0016] In some embodiments, the cross-linking layer has a dry film thickness of 1.0-1.5 μm, and the hydrophobic layer has a dry film thickness of 0.5-1.0 μm.

[0017] In some embodiments, the water content of the cross-linked layer is ≤2% (mass ratio), which is achieved by adsorbing free water molecules by nano-silicate.

[0018] In some embodiments, after the plate is stored at 40°C / 80% RH for 6 months, the sensitivity decay is ≤5%, the number of developed plates increases by ≤3 sheets, the printing run is ≥150,000 impressions, and the 50% dot wear rate is ≤1.5%.

[0019] On the other hand, the present invention also provides a method for preparing the above-mentioned on-press development type treatment-free CTP plate resistant to wet and hot storage, comprising the following steps:

[0020] S1. Electrolytic roughening, anodization and silicate sealing treatment are performed on the aluminum substrate to make its surface hydrophilic contact angle ≤10°;

[0021] S2. Apply the crosslinking layer to the surface of the aluminum substrate and dry it at a temperature of 90-110°C for 1-3 minutes;

[0022] S3. Coating the hydrophobic layer on the surface of the cross-linked layer and drying the layer at a temperature of 70-90° C. for 0.5-1.5 min.

[0023] The electrolytic roughening (Ra≤0.25 μm) and silicate sealing (contact angle≤10°) improve the adhesion of the coating, and the peel strength is ≥4.8 N / cm.

[0024] Furthermore, in the above preparation method,

[0025] The preparation of the cross-linked layer comprises: dissolving an acrylic acid-epoxy copolymer in an organic solvent, adding other components in sequence and dispersing them uniformly;

[0026] The preparation of the hydrophobic layer comprises: dissolving the hydrophobically modified styrene-maleic anhydride copolymer in a solvent, adding other ingredients and mixing until homogeneous.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a machine-developable and process-free CTP plate with a multi-layer structure composed of a base plate, a crosslinked layer, and a hydrophobic layer. Through nano-silicates, the water content in the coating is stabilized below 2%, effectively inhibiting the decay of photosensitivity caused by dark reactions. In combination with an acrylic-epoxy copolymer with a high glass transition temperature, it ensures that the molecular chains remain rigid under humid and hot conditions, delaying crosslinking relaxation. Through the synergistic action with components such as ultraviolet absorbers and radical quenchers, and a hydrophobic layer prepared from components such as a hydrophobically modified styrene-maleic anhydride copolymer, the prepared CTP plate has good printing performance, storage stability, and mechanical properties after being stored in a high-humidity and high-temperature environment for 6 months. The increase in the number of developed offset papers is controlled within 3 sheets, far lower than the increase of 20 - 40 sheets for traditional plates, meeting the industrial application requirements under complex climate conditions.

[0029] Other features and advantages of the present invention will be described in the subsequent specification, and will be understood in part by implementing the present invention. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for implementation will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 is the overall schematic diagram of the machine-developable and process-free CTP plate in the embodiment of the present invention.

[0032] Figure 2 is the result graph of the photosensitivity decay rate (%) test of different CTP plates of the present invention;

[0033] Figure 3 is the result graph of the number of developed offset papers (after storage) test of different CTP plates of the present invention;

[0034] Figure 4 is the result graph of the water content (%) test of different CTP plates of the present invention;

[0035] Figure 5 is the result graph of the printing endurance (in ten thousands of impressions) test of different CTP plates of the present invention;

[0036] Figure 6 is the result graph of the 50% dot wear rate (%) test of different CTP plates of the present invention.

[0037] Description of the Reference Numerals:

[0038] 1. including the base plate; 2. crosslinked layer; 3. hydrophobic layer. Detailed Embodiments

[0039] The following describes the technical solutions in the embodiments of the present invention clearly and completely in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0040] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0041] In the present invention, the test methods used are all conventional methods unless otherwise specified; the materials, reagents, etc. used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0042] In the present invention, the reagents and instruments used are shown in Tables 1 and 2 below.

[0043] Table 1 Reagent Parameter Table

[0044]

[0045]

[0046]

[0047] Table 2 Experimental Instrument Parameter Table

[0048]

[0049]

[0050]

[0051] Example 1

[0052] A preparation method of an in-machine developing type processless CTP plate capable of resisting damp and heat storage includes the following steps:

[0053] 1. Preparation of the crosslinked layer:

[0054] (1) Dissolve the acrylic-epoxy copolymer in ethylene glycol monomethyl ether at 50 °C and stir for 30 min until completely dissolved;

[0055] (2) Sequentially add multifunctional acrylate monomer, infrared absorber, and photoinitiator, and stir and mix evenly;

[0056] (3) Add montmorillonite nanosheets and disperse them for 20 min using a high-speed disperser (2000 rpm);

[0057] (4) Finally, add oxime ester radical quencher and triglycidyl isocyanurate, stir for 10 min, filter and set aside to obtain a liquid crosslinked layer.

[0058] 2. Preparation of the hydrophobic layer:

[0059] Dissolve the hydrophobic modified styrene-maleic anhydride copolymer in ethyl acetate, heat to 40 °C, stir and dissolve until transparent, then add infrared absorber, photoinitiator, and benzotriazole ultraviolet absorber, mix evenly, and then slowly add hexanediol diacrylate, continuously stir at 800 rpm for 30 min, then sieve (200 mesh) and stand for defoaming for 1 h to obtain a uniform liquid hydrophobic layer.

[0060] 3. Coating process

[0061] (1) The aluminum plate base is subjected to electrolytic roughening (surface roughness Ra = 0.18 μm), anodic oxidation, and silicate sealing treatment, and the hydrophilic contact angle ≤ 8°;

[0062] (2) The crosslinked layer is coated by microgravure, the wet film thickness is 1.5 μm, the drying temperature is 100 °C / 2 min, and the dry film thickness is 1.2 μm;

[0063] (3) The hydrophobic layer is coated by slot die coating, the wet film thickness is 1.0 μm, the drying temperature is 80 °C / 1 min, and the dry film thickness is 0.8 μm to obtain a CTP plate.

[0064] In this example, the crosslinked layer, by weight, includes 40 parts of acrylic-epoxy copolymer (model BASF 682, acrylic / epoxy mass ratio 6:4, Tg = 85 °C, weight average molecular weight 250,000), 35 parts of multifunctional acrylate monomer, 1.5 parts of infrared absorber (cyanine dye), 8 parts of photoinitiator (iodonium salt), 3 parts of montmorillonite nanosheets, 0.5 part of oxime ester radical quencher, 2 parts of triglycidyl isocyanurate (crosslinking agent).

[0065] In this example, the hydrophobic layer, by weight, includes 25 parts of hydrophobic modified styrene-maleic anhydride copolymer (model Krevalin 1440, maleic anhydride content 40%, hydrophobically modified with dodecyl glycidyl ether, hydrophilic groups reduced by 50%), 2 parts of infrared absorber (polymethine dye), 10 parts of photoinitiator (sulfonium salt), 1 part of benzotriazole ultraviolet absorber, 50 parts of hexanediol diacrylate.

[0066] Example 2

[0067] The differences between Example 2 and Example 1 are as follows:

[0068] Formula adjustment (parts by weight)

[0069] Cross-linked layer:

[0070] Acrylic acid-epoxy copolymer (model BASF 690, acrylic acid / epoxy mass ratio 5:5, Tg = 92 ° C, weight average molecular weight 300,000) is 42 parts; the content of montmorillonite nanosheets is 4 parts; and the crosslinking agent (triglycidyl isocyanurate) is 3 parts.

[0071] In step (3) of preparing the cross-linked layer, the dispersion time is 25 min to ensure that the montmorillonite is evenly dispersed.

[0072] During the coating process, the cross-linking layer is dried at a temperature of 110°C / 3 min to enhance cross-linking.

[0073] The rest is the same as Example 1.

[0074] Example 3

[0075] The differences between Example 3 and Example 1 are as follows:

[0076] Formula adjustment (parts by weight)

[0077] Hydrophobic layer:

[0078] Styrene-maleic anhydride copolymer (Polyscope SZ08300, maleic anhydride content 30%, hydrophobically modified by octadecyl isocyanate, hydrophilic group reduced by 60%) is 28 parts; benzotriazole UV absorber is 1.5 parts.

[0079] In the preparation of the hydrophobic layer, the dissolving temperature was 45 °C and the stirring time was 40 min to improve the resin compatibility.

[0080] In the coating process, the dry film thickness of the hydrophobic layer is 1.0 μm, and the drying temperature is 85°C / 1.5 min.

[0081] The rest is the same as Example 1.

[0082] Example 4

[0083] The differences between Example 4 and Example 1 are as follows:

[0084] Formula adjustment (parts by weight)

[0085] Cross-linked layer:

[0086] The montmorillonite nanosheets are replaced with attapulgite clay (specific surface area ≥ 300 m 2 / g), and the weight part is 3 parts.

[0087] The triglycidyl isocyanurate is replaced with tetraglycidyl diphenylmethane, and the weight part is 2.5 parts.

[0088] In the preparation of the crosslinked layer: The attapulgite clay needs to be pre-activated in an 80°C oven for 2 h and then mixed and dispersed with the resin.

[0089] Coating process: The drying temperature of the crosslinked layer is adjusted to 95°C / 2.5 min.

[0090] The rest is the same as in Example 1.

[0091] Example 5

[0092] The differences between Example 5 and Example 1 are as follows:

[0093] Formulation adjustment (weight parts)

[0094] Crosslinked layer: Add 1 part of silane coupling agent (KH-570)

[0095] Hydrophobic layer: Add 0.5 part of fluorocarbon surfactant (sodium perfluorooctane sulfonate)

[0096] Coating solution preparation:

[0097] Crosslinked layer: The silane coupling agent needs to be added dropwise after the resin is dissolved to avoid local agglomeration;

[0098] Hydrophobic layer: The fluorocarbon surfactant and the photoinitiator are added synchronously, and the stirring speed is 2500 rpm.

[0099] Coating process: The coating interval between the crosslinked layer and the hydrophobic layer is 10 min to ensure sufficient curing of the bottom layer.

[0100] The rest is the same as in Example 1.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 1 is that montmorillonite nanosheets are not added in Comparative Example 1, and the weight part of the acrylic-epoxy copolymer is 43 parts, and the rest is the same as in Example 1.

[0103] Comparative Example 2

[0104] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, an equal amount of ordinary acrylic resin (Tg = 65°C) is used to replace the acrylic-epoxy copolymer, and the rest is the same as in Example 1.

[0105] Comparative Example 3

[0106] The difference between Comparative Example 3 and Example 1 is that no oxime ester free radical quencher is added in Comparative Example 3, the weight portion of the acrylic acid-epoxy copolymer is 40.5 parts, and the rest is the same as Example 1.

[0107] Test Example 1

[0108] The CTP plates prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were respectively placed in a constant temperature and humidity chamber and stored at 40° C. / 80% RH for 6 months to analyze the wet heat storage stability of the CTP plates.

[0109] Test indicators:

[0110] Sensitivity test: Use a laser energy meter (model OphirVega) to measure the minimum imaging energy (mJ / cm2) of the plate at the beginning and after storage. 2 ), decay rate = (storage energy - initial energy) / initial energy × 100%;

[0111] Number of developed plates: The developer (model Kodak Magnus 800) was operated at a speed of 1.5 m / min, and the number of plates required to completely remove the unexposed areas was counted.

[0112] Coating moisture content: Karl Fischer moisture analyzer (model Metrohm 831) was used to measure the coating moisture content.

[0113] Table 3 Wet heat storage stability test results

[0114]

[0115]

[0116] From Table 3, Figure 2-4 It can be seen that the CTP plate coatings prepared in Examples 1 and 2 with the addition of nanosilicate (montmorillonite nanosheets) have a moisture content of ≤1.8%, which delays the dark reaction and has a sensitivity decay rate of ≤5%; while in Comparative Example 1 without nanosilicate, the moisture content of the coating reaches 3.2%, and moisture accelerates the degradation of the photosensitive layer, with a decay rate of 12.3%. At the same time, in Comparative Example 2 using a low Tg resin (Tg = 65°C), the molecular chains relax under wet heat, the binding force decreases, the moisture content is 4.1%, and the decay rate is 15.6%; and after storage, the number of developed plates in Comparative Examples 1 and 2 is higher than that in Examples 1 and 2, which means that the CTP plates of Comparative Examples 1 and 2 have a slower development speed, indicating that the CTP plates of the present invention have good wet heat storage stability.

[0117] Test Example 2

[0118] Analyze the press run and dot wear of different CTP plates.

[0119] Equipment: Heidelberg printing press (model Speedmaster XL 106), printing pressure 0.2 MPa, dampening solution pH = 4.8 (ethanol-based);

[0120] Printing durability: Total number of impressions until the wear rate of 50% dot area reaches ≥ 5%;

[0121] Dot wear rate: Measure the change in dot area before and after printing using a spectrophotometer densitometer (model X-Rite eXact).

[0122] Table 4 Test results of printing durability and dot wear rate

[0123]

[0124]

[0125] From Table 4, Figure 5-6 it can be seen that the high-Tg resin (Tg = 85 °C) in Example 1 and the crosslinking agent synergistically enhance the coating hardness, with a printing durability of 152,000 impressions and a wear rate of 1.3%; further in Example 3, by selecting a styrene-maleic anhydride copolymer with a 60% reduction in hydrophilic groups to reduce the penetration of the dampening solution, the printing durability is increased to 165,000 impressions; while in Comparative Example 3, there is no free radical quencher, resulting in residual polymerization in the unexposed area, leading to incomplete development and easy peeling of the coating during printing, with a printing durability of only 87,000 impressions, indicating that the CTP plate of the present invention has a lower dot wear rate after printing 150,000 impressions, superior to the wear rate of traditional plates (traditional plate wear rate ≥ 3%).

[0126] Test Example 3

[0127] Analyze the mechanical properties of different CTP plates.

[0128] Scratch hardness: Scratch tester (model Elcometer 3096), load 5 N, scratch speed 10 mm / s, evaluate the pencil hardness grade according to ASTM D3363;

[0129] Crosslink density: Dynamic mechanical analyzer (model TA Q800), frequency 1 Hz, heating rate 3 °C / min, calculate the storage modulus (E’) and crosslink density (ν = E’ / 3RT).

[0130] Table 5 Test results of the mechanical properties of CTP plates

[0131] Group Scratch hardness (H) <![CDATA[Crosslink density (mol / m 3 )]]> Example 1 3H <![CDATA[2.8×10 3 > Example 4 4H <![CDATA[3.1×10 3 ]]> Comparative Example 2 1H <![CDATA[1.2×10 3 >

[0132] As can be seen from Table 5, in Example 1, adding a crosslinked acrylic-epoxy copolymer (Tg = 85 °C) forms a dense network, with a crosslink density of 2.8×10 3 mol / m 3, scratch hardness 3H; further, in Example 4, attapulgite clay was added to enhance the resin-filler interface bonding, and the crosslinking density was increased to 3.1×10 3 mol / m 3 , the hardness reaches 4H; while the crosslinking density of comparative example 2 using low Tg resin is only 1.2×10 3 mol / m 3 , the coating is loose, and the scratch hardness is 1H, indicating that the CTP plate of the present invention has good mechanical properties.

[0133] Test Example 4

[0134] Analyze the long-term humidity and heat cycle test of different CTP plates.

[0135] Equipment: Humidity cycle chamber (model Espec SH-642), cycle conditions: 40°C / 80% RH 12 h → 25°C / 50% RH 12 h, for 30 days;

[0136] Peel strength: universal material testing machine (model Instron 5967), 90° peel test, speed 50 mm / min.

[0137] Table 6 Long-term humidity and heat cycle test results

[0138] Group Sensitivity attenuation rate Coating peel strength (N / cm) Example 1 5.2％ 4.8 Example 2 4.1％ 5.3 Comparative Example 1 18.7％ 2.1

[0139] As can be seen from Table 6, the nanosilicate and the crosslinking agent in Example 1 synergistically stabilize the coating-substrate interface, and the peel strength is 4.8 N / cm. Furthermore, Example 2 uses a resin with a Tg of 92°C to inhibit wet heat deformation, so that the peel strength is increased to 5.3 N / cm; while Comparative Example 1 does not add nanosilicate (montmorillonite nanosheets), resulting in deterioration of the interfacial bonding force, so that the peel strength is only 2.1 N / cm, which proves that the CTP plate of the present invention has good long-term wet heat cycle stability and durability.

[0140] In summary, the present invention provides a machine-developable, treatment-free CTP plate with a multi-layer structure consisting of a base, a cross-linked layer, and a hydrophobic layer. Free water is adsorbed by montmorillonite or attapulgite clay, and the moisture content of the coating is ≤2%, thereby suppressing sensitivity decay caused by dark reaction. In addition, an acrylic acid-epoxy copolymer (Tg ≥ 80°C) is used to maintain molecular chain rigidity under wet heat, delay cross-linking relaxation, and synergize with components such as ultraviolet absorbers and free radical quenchers, thereby not only enhancing wet heat storage stability but also having good printing performance. After storage for 6 months, the number of developed sheets of the CTP plate of the present invention increases by 20-40 sheets compared to traditional plates, and the number of developed sheets increases by ≤3 sheets.

[0141] Then, the hydrophobic layer of the present invention uses a hydrophobic modified styrene-maleic anhydride copolymer with fewer hydrophilic groups, reducing the penetration of dampening solution. The 50% dot wear rate ≤ 1.5%, and the crosslinked layer uses a multifunctional epoxy crosslinking agent with a printing endurance ≥ 150,000 impressions, which is 50% higher than that of traditional plates, improving the printing efficiency.

[0142] The hydrophobic layer of the CTP plate of the present invention further includes a fluorocarbon surfactant, which effectively reduces the surface energy of the coating, making the development residue rate ≤ 0.3%, and the minimum imaging energy as low as 175 mJ / cm 2 。

[0143] The present invention effectively extends the service life of the CTP plate by replacing the traditional protective layer with a multi-functional coating layer, reduces the printing quality problems caused by environmental changes, thus ensuring the high quality and consistency of printed products, and reducing the maintenance cost.

[0144] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An in-machine developing type processless CTP plate capable of resisting damp heat storage, characterized in that It includes a substrate; A crosslinking layer is provided on one surface of the substrate. By weight, the crosslinking layer includes 35-45 parts of a crosslinkable acrylic-epoxy copolymer, 30-40 parts of a polyfunctional acrylate monomer, 2-5 parts of nano-silicate, 1-2 parts of an infrared absorber, 5-10 parts of a photoinitiator, 0.3-1 part of a radical quencher, and 1-5 parts of a polyfunctional epoxy crosslinking agent; A hydrophobic layer is provided on the surface of the crosslinking layer facing away from the substrate. By weight, the hydrophobic layer includes 20-30 parts of a hydrophobically modified styrene-maleic anhydride copolymer, 1-3 parts of an infrared absorber, 8-12 parts of a photoinitiator, 0.5-2 parts of an ultraviolet absorber, and 45-55 parts of hexanediol diacrylate.

2. The on-machine developing type processless CTP plate according to claim 1, characterized in that, The substrate is an aluminum substrate.

3. The on-machine developing type processless CTP plate according to claim 1, wherein The glass transition temperature Tg of the acrylic-epoxy copolymer is ≥80 °C, and the weight-average molecular weight is 100,000-300,000.

4. The on-machine developing type processless CTP plate according to claim 1, wherein, The nano-silicate is montmorillonite or attapulgite clay.

5. The on-machine developing type processless CTP plate according to claim 1, characterized in that, The polyfunctional epoxy crosslinking agent is triglycidyl isocyanurate or tetraglycidyl diphenylmethane.

6. The on-machine developing type processless CTP plate according to claim 1, wherein The ultraviolet absorber is a benzotriazole compound; the radical quencher is an oxime ester compound.

7. The on-machine developing type processless CTP plate according to claim 1, characterized in that, The dry film thickness of the crosslinking layer is 1.0-1.5 μm, and the dry film thickness of the hydrophobic layer is 0.5-1.0 μm.

8. The on-machine developable and processless CTP plate according to claim 1, wherein The water content of the coating of the crosslinking layer is ≤2% (mass ratio), which is achieved by the nano-silicate adsorbing free water molecules.

9. The on-machine developing type processless CTP plate according to claim 1, characterized in that, After the plate material is stored under the conditions of 40 °C / 80% RH for 6 months, the sensitivity attenuation is ≤5%, the number of developed transfer papers increases by ≤3 sheets, the printing resistance is ≥150,000 impressions, and the wear rate of 50% of the dots is ≤1.5%.

10. A method for preparing an on-machine developing type processless CTP plate according to any one of claims 1-9, characterized in that, It includes the following steps: S1. The substrate is subjected to electrolytic roughening, anodic oxidation, and silicate sealing treatment to make the hydrophilic contact angle of its surface ≤10°; S2. The crosslinking layer is coated on the surface of the substrate and dried. The drying temperature is 90-110 °C, and the time is 1-3 min; S3. The hydrophobic layer is coated on the surface of the crosslinking layer and dried. The drying temperature is 70-90 °C, and the time is 0.5-1.5 min.

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