Lipophilic alkali-soluble resin, preparation method and lithographic printing plate photosensitive resist

Abstract

The invention belongs to the technical field of photo-thermal functional materials, and discloses a lipophilic alkali-soluble resin, a preparation method and a lithographic printing plate photo-sensitive adhesive. The lipophilic alkali-soluble resin disclosed by the invention simultaneously contains phenolic hydroxyl groups and tetrazolyl strong electron-withdrawing groups, and is used as a base material and combined with an efficient infrared absorbent, so that a high-quality image is directly formed through infrared laser scanning without a solvent inhibitor, the contradiction between alkali resistance and photosensitive speed is successfully solved, and the application prospect is wide. And meanwhile, the developing latitude, the film retention rate and the wear resistance are remarkably improved, a new path is opened up for development of an infrared positive image thermosensitive CTP plate technology, and the method has important significance in promoting technical progress and industrial upgrading of the printing industry.

Description

Technical Field

[0001] This invention relates to the field of photothermal functional materials technology, and in particular to an oleophilic alkali-soluble resin, its preparation method, and a photosensitive emulsion for offset printing plates. Background Technology

[0002] In the printing industry, offset printing technology plays a crucial role, especially with the integration of digital technology, computer-to-plate (CTP) technology has become a key link in the modern printing process. Among them, infrared positive thermal CTP plates have received widespread attention and application in the industry due to their high resolution, high efficiency, and environmental friendliness. These printing plates form images directly on the plate material through infrared laser scanning, eliminating the need for film output and manual plate assembly steps in traditional plate making, greatly shortening the plate-making cycle and improving production efficiency.

[0003] Although existing infrared positive thermal CTP plate technology is relatively mature, it still faces certain technical challenges in practical applications. One bottleneck is how to improve the alkali resistance of the plate material while ensuring high photosensitivity to withstand the erosion of various chemicals during printing. There is often an inverse relationship between alkali resistance and photosensitivity; increasing alkali resistance reduces photosensitivity, while increasing photosensitivity may sacrifice alkali resistance. This contradiction limits further improvements in printing plate performance. Furthermore, existing technologies also have shortcomings in development latitude, film retention, and abrasion resistance. Low development latitude means stringent requirements for condition control during development, and even slight errors can lead to image quality degradation; low film retention affects the durability and clarity of printed materials; and poor abrasion resistance shortens the lifespan of the printing plate and increases production costs. In addition, some existing technical solutions rely on adding solvent inhibitors to achieve thermal imaging, which not only increases the complexity of the preparation process but may also affect the quality and stability of the final printed product. Summary of the Invention

[0004] The purpose of this invention is to propose an oleophilic alkali-soluble resin that contains both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups. As a material for preparing infrared positive thermosensitive CTP plates, it effectively solves the contradiction between strong alkali resistance and fast sensitivity.

[0005] The technical solution adopted to achieve the purpose of this invention is: A lipophilic, alkali-soluble resin, wherein the resin is an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium-based strong electron-withdrawing groups, and its structure is represented by the following structural formula I or structural formula II: I II Wherein, X and Y are H, O, S, N, phenyl, p-tolyl, aryl, C1-C10 alkyl or halogroups.

[0006] Furthermore, the resin has a weight-average molecular weight of 8,000 to 15,000, an appearance of light blue-yellow crystals, a density of 1.0 to 1.2, a glass transition temperature of 90 to 100 degrees Celsius, an acid value of less than 2, and an n value of 30 to 70.

[0007] Another object of the present invention is to provide a method for preparing an oleophilic alkali-soluble resin, which is easy to implement and suitable for large-scale production.

[0008] The technical solution adopted to achieve another objective of the present invention is: A method for preparing an oleophilic alkali-soluble resin includes the following steps: Step S1, Preparation of phenolic resin: Phenol and formaldehyde aqueous solution are heated under acidic conditions and refluxed to obtain phenolic resin; Step S2, preparation of lipophilic alkali-soluble resin: The phenolic resin obtained in step S1 is reacted with a tetrazolium derivative in an organic solvent under reflux to generate an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups; after the reaction is completed, the lipophilic alkali-soluble resin product is obtained by vacuum distillation, dissolution, precipitation, separation and drying.

[0009] Furthermore, in step S1, the temperature of the reflux reaction is 50–120°C, the reaction time is 4–8 hours, and continuous stirring is required during the reaction.

[0010] Furthermore, in step S2, the heating reflux reaction process is carried out at 80–100°C for 5–10 hours.

[0011] Furthermore, in step S2, the organic solvent is methyl isobutyl ketone, and the solvent needs to be removed under reduced pressure by a rotary evaporator after the reaction is completed.

[0012] Furthermore, in step S2, the precipitation step is achieved by dropping the reaction solution into ice water containing hydrochloric acid. After separation and drying, the precipitate yields an oleophilic alkali-soluble resin product.

[0013] Another objective of this invention is to provide an infrared positive thermal offset printing plate photosensitive emulsion that simultaneously possesses strong alkali resistance and fast sensitivity, and significantly improves development tolerance, film retention rate, and abrasion resistance.

[0014] The technical solution adopted to achieve another objective of the present invention is: An infrared thermal offset printing plate photosensitive adhesive includes an aluminum carrier and an infrared sensitive composition. The surface of the aluminum carrier is treated with electrochemical roughening and anodizing. The infrared sensitive composition is used to coat the surface of the aluminum carrier. The infrared-sensitive composition includes the above-mentioned oleophilic alkali-soluble resin, as well as an infrared absorber and additives.

[0015] Furthermore, the infrared absorber is selected from one or more of the following: cyanine dyes, squaric acid cyanine dyes, phthalocyanine dyes, cyanine dye derivatives, and metal complex infrared absorbing dyes.

[0016] Furthermore, the additives include one or more of surfactants, coloring background dyes, and solvents.

[0017] The principle of this invention lies in the interaction of phenolic hydroxyl groups and aldehyde or ketone groups in lipophilic alkali-soluble resins through hydrogen bonding, which enhances the alkali solubility of the resin. Since the alkali resistance and hydrogen bonding production efficiency and speed of conventional phenolic resins do not meet expectations, the tolerance of the printing plate is low. By introducing the special material of this invention, hydrogen bonding can be strengthened and formed rapidly, achieving higher alkali resistance. However, when the printing plate is subjected to infrared laser scanning, the infrared radiation is converted into heat energy. The added special material undergoes molecular breakage at high temperatures, disrupting the hydrogen bonds between it and the resin, and simultaneously generating microbubbles. This significantly improves the solubility and dissolution rate in alkaline solutions, simultaneously satisfying the increased sensitivity of both chemical and physical types. This effectively solves the contradiction between strong alkali resistance and rapid sensitivity, achieving both high alkali resistance and rapid sensitivity.

[0018] The beneficial effects of this invention are as follows: The oleophilic alkali-soluble resin of this invention contains both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups. Using this as a base material, combined with a highly efficient infrared absorber, it enables the direct formation of high-quality images through infrared laser scanning without the need for solvent inhibitors. This successfully solves the contradiction between alkali resistance and photosensitivity speed, while significantly improving development tolerance, film retention rate, and abrasion resistance. It opens up a new path for the development of infrared positive thermal CTP plate technology and is of great significance for promoting technological progress and industrial upgrading in the printing industry. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a comparison diagram of the development results of Embodiment 1 and the comparative example of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0021] Example 1 A method for preparing an oleophilic alkali-soluble resin includes the following steps: Step S1, Preparation of phenolic resin: In a fume hood, 70 g of phenol, 43.4 g of a 36.5% formaldehyde aqueous solution, and 0.15 g of oxalic acid were added to a 250 mL flask. The mixture was heated to reflux at 100 °C and stirred continuously under reflux for 6 hours. After reflux, the reflux condenser was removed, and a vacuum distillation apparatus was used to remove water and unreacted phenol. The remaining reactants were poured into a flat container while still hot and cooled to room temperature to obtain approximately 60 g of phenolic resin, which was reserved for the next synthesis step.

[0022] Step S2, preparation of lipophilic alkali-soluble resin: In a fume hood, 21.2 g of the phenolic resin synthesized in step S1, 12 g of aniline, and 100 g of methyl isobutyl ketone were added to a four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, reflux condenser, and dropping funnel. After mixing and dissolving, the mixture was heated to 80°C and stirred at this temperature for 2 hours. 8 g of tetrazolium derivative was dissolved in 20 g of methyl isobutyl ketone to form a mixture, which was then added dropwise to the four-necked round-bottom flask over 30 minutes using a dropping funnel. The temperature of the reaction mixture was then increased to 100°C, and the reaction was continued under reflux and stirring for 3 hours to produce the final reaction solution.

[0023] After the reaction was complete, the reaction solution was transferred to a distillation flask in a rotary evaporator, and methyl isobutyl ketone was removed under reduced pressure in a 100°C water bath. Then, 100g of acetone was added to the reaction flask to dissolve the residue, followed by dropwise addition of the acetone solution into 1.5L of ice water (containing 5mL of concentrated hydrochloric acid) under stirring to precipitate the residue. After stirring continuously for 30 minutes, the precipitate was separated and dried to obtain 36g of phenolic resin HFS1 containing a tetrazolium derivative.

[0024] The HFS1 sample was analyzed using GPC (Gel Permeation Chromatography). GPC is a standard testing method in this field, primarily used for determining the molecular weight distribution and average molecular weight of polymeric compounds through high-performance liquid chromatography.

[0025] Upon testing, resin HFS1 in this embodiment is identified as an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium-based strong electron-withdrawing groups, and its structure is represented by the following structural formula:

[0026] Where X is -H and Y is -S The specific characterization results of the resin are as follows: It has a weight-average molecular weight of 9250, an appearance of light blue-yellow crystals, a molar content of 9.3%, a density of 1.12, a glass transition temperature of 93 degrees Celsius, an acid value of 1.5, and an n value of 51.

[0027] Examples 2-5 The preparation methods of Examples 2-5 are almost the same as those of Example 1. The main difference is that the tetrazolium derivative added in step S2 is different, which makes the resin product structure and characterization different. The synthetic resins prepared in Examples 2-5 are named HFS2, HFS3, HFS4 and HFS5, respectively.

[0028] In Example 2, following the steps S1 to S2 in Example 1, para-substituted phenolic resins were selected to synthesize resin HFS2.

[0029] In Examples 3-5, tetrazolium derivatives with different substituents were used to obtain synthetic resins HFS3, HFS4, and HFS5 respectively, following steps S1 to S2 in Example 1.

[0030] The structural formulas and characterization test results for each embodiment are as follows: Example 2 In this embodiment, resin HFS2 is an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups. Its structure is represented by the following structural formula:

[0031] Where X is -H and Y is -O.

[0032] The specific characterization results of the resin are as follows: It has a weight-average molecular weight of 8788, appears as light blue-yellow crystals, has a molar content of 8%, a density of 1.1, a glass transition temperature of 92.5 degrees Celsius, an acid value of 1.9, and an n value of 48.

[0033] Example 3 In this embodiment, resin HFS3 is an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups. Its structure is represented by the following structural formula:

[0034] Where X is -S and Y is -O.

[0035] The specific characterization results of the resin are as follows: It has a weight-average molecular weight of 12250, an appearance of light blue-yellow crystals, a molar content of 9%, a density of 1.21, a glass transition temperature of 96 degrees Celsius, an acid value of 1.7, and an n value of 53.

[0036] Example 4 In this embodiment, resin HFS4 is an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups. Its structure is represented by the following structural formula:

[0037] Where X is -CL and Y is -O.

[0038] The specific characterization results of the resin are as follows: It has a weight-average molecular weight of 11,850, an appearance of light blue-yellow crystals, a molar content of 8.8%, a density of 1.15, a glass transition temperature of 95 degrees Celsius, an acid value of 1.76, and an n value of 60.

[0039] Example 5 In this embodiment, resin HFS5 is an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups. Its structure is represented by the following structural formula:

[0040] Where X is -phenyl and Y is -O.

[0041] The specific characterization results of the resin are as follows: It has a weight-average molecular weight of 14250, appears as light blue-yellow crystals, has a molar content of 9.3%, a density of 1.22, a glass transition temperature of 97 degrees Celsius, an acid value of less than 1.9, and an n value of 59.

[0042] Table 1 below compares the X and Y groups in the resins of Examples 1-5 of this invention.

[0043] Table 1 Comparison of X and Y groups in the resins of Examples 1-5

[0044] In this invention, since the molar percentage of components containing the above substituents in the resin is less than 10%, it has no qualitative impact on the fundamental properties of the original resin. Therefore, this invention does not include experiments on the effect of adding resins with different groups on product performance.

[0045] Examples 6-10 Examples 6-10 respectively use the resins from Examples 1-5 to prepare infrared positive thermal offset printing plates photosensitive emulsions.

[0046] Example 6 An infrared positive thermal offset printing plate photosensitive adhesive includes an aluminum carrier and an infrared-sensitive composition. The surface of the aluminum carrier is subjected to electrochemical roughening and anodizing treatment. The infrared-sensitive composition is used to coat the surface of the aluminum carrier. The infrared-sensitive composition includes the aforementioned oleophilic alkali-soluble resin, as well as an infrared absorber and additives.

[0047] In this embodiment, the method for preparing the photosensitive emulsion for infrared positive thermal offset printing plates includes the following steps: (a) Preparation of the infrared-sensitive composition: 1.5g of the lipophilic alkali-soluble resin (i.e., resin HFS1) in Example 1; 0.25g of infrared absorber, and the infrared absorber is selected from cyanine dye S0094; 0.2g of coloring dye, with crystal violet selected as the coloring dye; 6g of BTB-30 resin.

[0048] The components of the above infrared-sensitive composition are dissolved in a mixed solvent consisting of 70g of PM (1-methoxy-2-propanol) and 30g of methyl isobutyl ketone to form a composition solution.

[0049] (b) Coating and drying: A UV-resistant alkali-soluble resin was coated onto an aluminum substrate that had undergone electrochemical roughening and anodizing. The substrate was then dried in an oven at 140°C for 2 minutes. After cooling, the prepared composition solution was coated onto the substrate and dried in an oven at 120°C for 2 minutes. This process yielded a photosensitive emulsion sample HFL1 for offset printing, with a coating weight of approximately 1.5 g / m².

[0050] Examples 7-10 In Examples 7-10, resin HFS1 in the infrared-sensitive composition of Example 1 was replaced with resins HFS2, HFS3, HFS4, and HFS5 in Examples 2-5, respectively, while the raw material ratios and preparation methods remained completely identical. After processing the raw materials of Examples 7-10 using the preparation method of Example 1, photosensitive emulsion samples HFL2, HFL3, HFL4, and HFL5 for offset printing plates were obtained, respectively.

[0051] Comparative Example This comparative example does not contain the lipophilic alkali-soluble resins used in Examples 1-5; all examples use BTB-30 resin. The specific preparation method for the comparative example is as follows: (a) Preparation of the control composition: 0.25g of infrared absorber, and the infrared absorber is selected from cyanine dye S0094; 0.2g of coloring dye, with crystal violet selected as the coloring dye; 7.5g of BTB-30 resin.

[0052] The components of the above control composition were dissolved in a mixed solvent consisting of 70g of PM (1-methoxy-2-propanol) and 30g of methyl isobutyl ketone to form a composition solution.

[0053] (b) Coating and drying: A UV-resistant alkali-soluble resin was coated onto an aluminum substrate that had undergone electrochemical roughening and anodizing. The substrate was then dried in an oven at 140°C for 2 minutes. After cooling, the prepared composition solution was coated onto the substrate and dried in an oven at 120°C for 2 minutes. This process yielded a photosensitive emulsion sample HFDZ for offset printing plates with a coating weight of approximately 1.5 g / m².

[0054] In Examples 6-10 and the Comparative Examples, some of the raw materials were sourced as follows: BTB-30 resin was purchased from Weihai Tiancheng Chemical Co., Ltd. This resin is widely used in positive PS plates, thermal CTP plates, chemically amplified printing plates, and other applications, and has been recognized by a wide range of users. Its application has played a significant role in promoting the domestic printing industry to catch up with international standards.

[0055] The UV-resistant alkali-soluble resin was purchased from Zhejiang Jixiang New Materials Co., Ltd., model: G2.

[0056] For aluminum plate bases, double-coated plate bases from Huafeng Dijiete Printing Materials Co., Ltd. are preferred.

[0057] Table 2 below shows the raw material comparison for Examples 6-10 and the comparative examples of this invention.

[0058] Table 2. Comparison of raw materials for Examples 6-10 and Comparative Examples.

[0059] I. Performance Testing The HFL1, HFL2, HFL3, HFL4, HFL5 and the control sample HFDZ were scanned and exposed using an 830nm laser on a Screen 8600 CTP plate-making machine at a drum rotation speed of 800rpm and a laser power of 50%–95%. After exposure, the original plates were developed at 24℃ for 25s with KS+ developer (from Huafeng Dijet Printing Materials Co., Ltd.). The film retention rate of the test samples is compared in Table 3 below, and the halftone dots and clean spots of the samples are compared in Table 4 below.

[0060] Table 3 Comparison of film retention rates of samples

[0061] Table 4 Comparison of Sample Spots and Clean Spots

[0062] II. Conclusion Figure 1 This is a comparison diagram of the development results of Example 1 and the comparative example of the present invention. Figure 1 The results show that the coating of the exposed part of the photosensitive emulsion of the offset printing plate obtained in the embodiment of the present invention is completely dissolved, and the coating of the non-exposed part is retained. The plate image is clear and the edges are sharp and neat. In contrast, the control sample HFDZ has a blurry plate surface, fuzzy edges, and low film retention rate.

[0063] As shown in Table 3, the film retention rate of the control sample HFDZ was 88.1%. Compared to the control sample HFDZ prepared with resins containing neither phenolic hydroxyl nor tetrazolium groups (strong electron-withdrawing groups), the infrared positive thermal lithography plates HFL1 to HFL5 prepared with the oleophilic alkali-soluble resin containing both phenolic hydroxyl and tetrazolium groups (strong electron-withdrawing groups) of this invention exhibited significantly higher film retention rates, ranging from 96.9% to 98.0%. Film retention rate reflects the ability of the plate material to retain the coating in non-exposed areas during development. A high film retention rate indicates that the resin is stably soluble in alkaline developer and is not excessively eroded by the developer, directly demonstrating the strong alkali resistance of the resin of this invention. This indicates that the resin of this invention, through the synergistic effect of phenolic hydroxyl and tetrazolium groups, forms a stable hydrogen bond network, significantly improving the resin's alkali resistance, thereby retaining more coating after development. Furthermore, the control sample HFDZ lacks a rapid response mechanism of tetrazolium groups, resulting in low film retention and blurred images; while the resin of this invention significantly improves the development and dissolution speed through photothermal conversion and microbubble effect, achieving a response of "rapid dissolution even with low exposure", indicating that the sensitivity of this invention is fast.

[0064] As shown in Table 4, the infrared positive thermal offset printing plates HFL1 to HFL5 prepared using the special resin of this invention outperform the control sample HFDZ in both dot reproduction and clean dot performance. Specifically, the 50% and 3% dot reproduction of samples HFL1 to HFL5 are more accurate, and the corresponding exposure power for clean dots is lower, indicating that the plates of Examples 6-10 can better control dot transfer during imaging, achieving clear image edges and detail reproduction. Dot reproduction accuracy and clean dot exposure power reflect the plate's sensitivity and accuracy to laser energy. Plates with high sensitivity can accurately respond to the energy distribution of laser scanning, forming sharp image edges; while plates with low sensitivity will have insufficient exposure due to insufficient energy absorption, resulting in residue and ultimately causing smudges on the print. Based on this, the control sample HFDZ, due to its resin structure lacking rapid photothermal response capability, exhibited uneven coating dissolution after development, resulting in blurred dots and an unclean background. The resin of this invention, through photothermal conversion of tetrazolium groups and microbubble-assisted dissolution, achieves efficient absorption and rapid response to laser energy, thereby forming clear dots and a clean background after development, further directly demonstrating the technical advantage of the fast sensitivity of this invention.

[0065] Based on the results in Tables 3 and 4 above, it can be concluded that the resin of the present invention has excellent performance in enhancing the alkali resistance of the printing plate, while ensuring high photosensitivity under infrared laser scanning. It achieves the technical effect of strong alkali resistance and fast sensitivity, effectively solving the contradiction between alkali resistance and photosensitivity in traditional technology.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A lipophilic, alkali-soluble resin, characterized in that, This resin is an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium-based strong electron-withdrawing groups, and its structure is represented by the following structural formula I or structural formula II: I II Wherein, X and Y are H, O, S, N, phenyl, p-tolyl, aryl, C1-C10 alkyl or halogroups.

2. The lipophilic alkali-soluble resin according to claim 1, characterized in that, The resin has a weight-average molecular weight of 8,000 to 15,000, appears as light blue-yellow crystals, has a density of 1.0 to 1.2, a glass transition temperature of 90 to 100 degrees Celsius, an acid value of less than 2, and an n value of 30 to 70.

3. A method for preparing an oleophilic alkali-soluble resin, characterized in that, Includes the following steps: Step S1, Preparation of phenolic resin: Phenol and formaldehyde aqueous solution are heated under acidic conditions and refluxed to obtain phenolic resin; Step S2, preparation of lipophilic alkali-soluble resin: The phenolic resin obtained in step S1 is reacted with a tetrazolium derivative in an organic solvent under reflux to generate an alkali-soluble polymer containing both phenolic hydroxyl groups and tetrazolium groups, which are strong electron-withdrawing groups; after the reaction is completed, the lipophilic alkali-soluble resin product is obtained by vacuum distillation, dissolution, precipitation, separation and drying.

4. The method for preparing the lipophilic alkali-soluble resin according to claim 3, characterized in that, In step S1, the temperature of the reflux reaction is 50-120°C, the reaction time is 4-8 hours, and continuous stirring is required during the reaction.

5. The method for preparing the lipophilic alkali-soluble resin according to claim 3 or 4, characterized in that, In step S2, the heating and reflux reaction process is carried out at 80-100°C for 5-10 hours.

6. The method for preparing the lipophilic alkali-soluble resin according to claim 3 or 4, characterized in that, In step S2, the organic solvent is methyl isobutyl ketone, and the solvent needs to be removed under reduced pressure by rotary evaporator after the reaction is completed.

7. The method for preparing the lipophilic alkali-soluble resin according to claim 3 or 4, characterized in that, In step S2, the precipitation step is achieved by dropping the reaction solution into ice water containing hydrochloric acid. After separation and drying, the precipitate yields an oleophilic alkali-soluble resin product.

8. An infrared positive thermal offset printing plate photosensitive emulsion, characterized in that, The product includes an aluminum carrier and an infrared-sensitive composition. The surface of the aluminum carrier is treated with electrochemical roughening and anodizing, and the infrared-sensitive composition is used to coat the surface of the aluminum carrier. The infrared-sensitive composition includes the oleophilic alkali-soluble resin as described in any one of claims 1 to 2, and further includes an infrared absorber and additives.

9. The infrared positive thermal offset printing plate photosensitive emulsion according to claim 8, characterized in that, The infrared absorber is selected from one or more of the following: cyanine dyes, squaric acid cyanine dyes, phthalocyanine dyes, cyanine dye derivatives, and metal complex infrared absorbing dyes.

10. The infrared positive thermal offset printing plate photosensitive emulsion according to claim 8 or 9, characterized in that, Additives include one or more of surfactants, coloring background dyes, and solvents.

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