Light-curing release agent, low-peeling-force and high-transmittance release film, and preparation method thereof

Abstract

The present invention discloses a photocurable release agent, a release film with low peel force and high light transmittance, and a preparation method thereof, belonging to the technical field of release agents. The photocurable release agent is made from the following raw materials in parts by weight: 82–88% siloxane, of which hexenyl polydimethylsiloxane accounts for more than 60% by weight, and the remainder is hydrogen-containing siloxane; 5–10% fluorine-containing acrylic monomer; 0.1–2% catalyst; and 0.5–6% initiator. The photocurable release agent is evenly coated on a substrate and irradiated with light under a protective atmosphere to obtain a release film. The release film produced by the present invention can have a 24-hour peel force of less than 5g / 25mm at room temperature, a light transmittance greater than 90%, and good uniformity.

Description

Technical Field

[0001] The present invention relates to the technical field of release materials, and in particular to a light-curing release agent, a release film with low peeling force and high light transmittance, and a preparation method thereof. Background Art

[0002] Silicone release agents are composed of low molecular weight vinyl-containing (-CH=CH2) siloxanes, hydrogen-containing siloxanes and some auxiliary components. Under a certain curing method, hydrogen-silicon bonds (Si-H) react with vinyl (-CH=CH2) to form silane hydrogen addition reactions to generate elastomeric materials with a certain cross-linking density. This material has a wide range of applications in consumer electronic products, one of which is polarizer release film. Polarizer is an important component of the display panel. It can control the light beam to produce a specific polarization angle, thereby controlling the transmission and absorption of light, creating light and dark contrast on the screen, and achieving the function of pattern display. The release film is an important component of the polarizer. Based on the characteristics of the polarizer, higher requirements are placed on the polarizer release film: such as good light transmittance, good stability and a certain degree of hydrophobicity.

[0003] At present, the most widely used and technologically mature method for preparing release films is thermal curing, but thermal curing has certain limitations and complexities in use. For example, the heat required for thermal curing exceeds the heat that many film substrates can withstand while maintaining their dimensional stability, which greatly limits the range of applicable substrates. In addition, thermal curing not only dries and forms the release film, but also reduces the moisture in the substrate. However, moisture control in the substrate is crucial for flat laying and dimensional stability, because the release film requires a certain amount of moisture to control the curling and wrinkling of the liner. If the moisture adsorption is uneven, uncontrollable wrinkles will form over time. In addition, the thermal curing process faces a large amount of solvent volatilization, which will pollute the environment. Another disadvantage of thermal curing is that curing, cross-linking and film formation occur simultaneously, and the two compete with each other, so the possibility of film defects increases. The above problems increase the cost and complexity of thermal curing, thereby limiting the application scenarios of this technology.

[0004] Photocuring technology solves the above problems and can be applied to temperature-sensitive substrates without causing moisture loss in the substrate. In addition, photocuring technology also has the advantages of fast curing speed, simple instruments and equipment, no solvent volatilization waste, low curing temperature, and the ability to separate film formation and curing. However, precious metal catalysts (such as iridium, platinum, ruthenium, etc.) are currently often used in photocuring. The use of precious metals significantly increases production costs and is unsustainable. Therefore, the development of efficient non-precious metal catalysts is of great significance for promoting the development of release film preparation technology. Chinese patent CN112661995A discloses a method for preparing a photocurable polarizer release film. This method still uses a large amount of solvent, and the resulting polarizer release film has poor transmittance and large peeling force, and its 24-hour peeling force exceeds 7g / 25mm. Summary of the Invention

[0005] In order to solve the problems that the existing photo-induced curing uses precious metal catalysts, resulting in high production costs; the use of a large amount of solvents leads to poor product transmittance and high peeling force, which makes it difficult to meet the development needs of release films in high-end consumer electronic products, the present invention provides a photocurable release agent, a release film with low peeling force and high transmittance, and a preparation method thereof.

[0006] The technical solution adopted in the present invention is:

[0007] A light-curing release film comprises the following raw materials in parts by weight:

[0008] Siloxane 82–88%, of which hexenyl polydimethylsiloxane accounts for more than 60wt% and the rest is hydrogen-containing siloxane;

[0009] Fluorinated acrylic monomer 5–10%;

[0010] Catalyst 0.1–2%;

[0011] Initiator 0.5–6%.

[0012] The structural formula of hexenyl polydimethylsiloxane is:

[0013]

[0014] R1=vinyl or allyl, R2=C 0–8 Hydrocarbyl, n is an integer from 10 to 1000;

[0015] The structural formula of hydrogen siloxane is:

[0016]

[0017] R3=H or methyl, and m is an integer from 10 to 1000.

[0018] Furthermore, the number average molecular weight of the siloxane is 200,000-1,000,000.

[0019] Furthermore, the initiator is one or more of diphenylacetophenone alcohol, 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0020] Furthermore, the molecular structure of the catalyst is as shown in formula (1) or formula (2):

[0021]

[0022] Wherein, M is selected from metal zinc, iron or copper; R4 is selected from 4-pyridyl or phenyl, R5 is selected from ethyl, and R6 is selected from ethyl or methyl.

[0023] Furthermore, the structural formula of the fluorine-containing acrylic monomer is shown in formula (3):

[0024]

[0025] Wherein, R7 is selected from H or methyl, and R8 is selected from H or methyl.

[0026] A release film with low peeling force and high light transmittance comprises a substrate and any one of the above-mentioned light-curing release agents coated on one side of the substrate.

[0027] Furthermore, the material of the substrate is PET, and the thickness of the release agent layer is 30-50 μm.

[0028] The method for preparing the above-mentioned release film with low peeling force and high light transmittance comprises the following steps:

[0029] (1) mixing siloxane, fluorinated acrylic monomer, catalyst, and initiator according to a ratio, and stirring uniformly to obtain a release agent;

[0030] (2) The release agent prepared in step (1) is evenly coated on the substrate and irradiated under a protective atmosphere to obtain a release film. The reaction principle is as follows:

[0031]

[0032] Furthermore, the molar ratio of the initiator to the catalyst is (3–16):1.

[0033] Furthermore, the protective atmosphere is nitrogen or argon.

[0034] Furthermore, the reaction temperature of the illumination is 5-50°C, and the reaction time is 1-10 hours.

[0035] Furthermore, the light source of the illumination is visible light.

[0036] Beneficial effects of the present invention:

[0037] The present invention uses non-precious metal photocatalysts, initiators, siloxanes and fluorine-containing acrylic monomers to prepare photocurable release agents, which simplifies the operating process, greatly reduces the use of solvents, and reduces production costs. At the same time, the use of photocuring technology makes the reaction conditions milder, which can effectively avoid the adverse effects of temperature on the material structure and performance, and is beneficial to improving the stability of the product. In addition, the introduction of fluorine-containing acrylic monomers helps to improve the hydrophobicity of the release film and further improve the stability of the product. Thanks to the good light absorption performance of the photocatalyst used in the present invention in the visible light region, visible light (wavelength ≥ 420nm) can be used as a light source, which is less harmful than ultraviolet light. The photocuring method used in the present invention has the characteristics of high curing efficiency, high product uniformity, and simple process. The 24-hour peeling force of the release film prepared by the present invention can be less than 5g / 25mm at room temperature; and it has a transmittance greater than 90% and good uniformity. The release film produced by the present invention can be used in the field of polarizers. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the infrared spectrum of the release film A prepared in Example 1 before and after photocuring.

[0039] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the release film A prepared in Example 1 before and after photocuring.

[0040] Figure 3 Thermal analysis data of release film A prepared in Example 1.

[0041] Figure 4 This is an electron microscope image of the release film A prepared in Example 1. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0043] The raw materials used in the following examples and comparative examples are commercially available.

[0044] Hexenyl polydimethylsiloxane was purchased from Dow Corning (PH112) and was used after removing the solvent.

[0045] Hydrogen-containing siloxane was purchased from Dow Corning (HH127) and was used after removing the solvent.

[0046] The photocatalyst 5,10,15,20-tetraphenyl-21H,23H-porphine zinc was purchased from Myrel (M62099), 5,10,15,20-tetrakis(4-pyridyl)porphyrin iron was purchased from MacLean (T982843), and tris(2-phenylpyridyl)iridium was purchased from Tianjin Xiensiopude Technology Co., Ltd. (T-0443654).

[0047] Fluorinated acrylic monomers 2,2,2-trifluoroethyl acrylate (A20836) and trifluoroethyl methacrylate (A67405) were purchased from Beijing Inokai Technology Co., Ltd.

[0048] The initiator 2,2-diethoxyacetophenone was purchased from Myrel (M37290), and diphenylacetophenone alcohol was purchased from Beijing Yinuokai Technology Co., Ltd. (A78805).

[0049] Example 1

[0050] The photocatalyst used in this embodiment is 5,10,15,20-tetraphenyl-21H,23H-porphine zinc, and its structural formula is as follows:

[0051]

[0052] The preparation method of the light-curing release film A is as follows:

[0053] (1) 6 g of hexenyl polydimethylsiloxane with a number average molecular weight of about 40W and 4 g of hydrogen-containing siloxane were mixed evenly, 0.8 mL of fluorinated acrylic monomer 2,2,2-trifluoroethyl acrylate, 20 mg of photocatalyst 5,10,15,20-tetraphenyl-21H,23H-porphine zinc, and 50 μL of initiator 2,2-diethoxyacetophenone were added, the molar ratio of photocatalyst to initiator was 1:8, and the amount of photocatalyst was 0.20% (mass ratio) of the amount of siloxane. The above components were mixed evenly to obtain release agent A;

[0054] (2) The release agent A was evenly coated on the surface of the PET substrate layer, and irradiated with visible light at a temperature of 20°C under argon as a protective atmosphere for 3 hours to obtain a photocurable release film A, the thickness of which was 38 μm.

[0055] The light-curing release film A was characterized, and the results of infrared testing are shown in Figure 1 , H NMR spectrum see Figure 2 , thermal stability test results are shown in Figure 3 ,from Figure 1 It can be found that after photocatalysis, the 2167cm- -1 The infrared absorption band at 1639 cm-1 is significantly weakened, and the 1639 cm-1 absorption band unique to olefins in the hexenyl group is significantly weakened. -1The infrared absorption band at 100 nm disappears significantly, indicating that the curing reaction has occurred. Figure 2 It can be found that after photocatalysis, the signal at δ4.75ppm is weakened, which corresponds to the protons in the hydrogen-containing siloxane, indicating that a curing reaction has occurred and the H content has decreased. The signal at δ5.00ppm is slightly weakened, which corresponds to the vinyl groups in the siloxane, indicating that a curing reaction has occurred. Figure 3 It shows that the prepared release film has good thermal stability. Figure 4 It can be found that the prepared release film has good surface uniformity. The prepared release film A shows a static water contact angle of about 99°, indicating high hydrophobicity.

[0056] Example 2

[0057] The catalyst used is the same as in Example 1

[0058] The preparation method of the light-curing release film B is as follows:

[0059] (1) 8 g of hexenyl polydimethylsiloxane with a number average molecular weight of about 40W and 2 g of hydrogen-containing siloxane were mixed evenly, and 1.6 mL of fluorinated acrylic monomer trifluoroethyl methacrylate, 10 mg of photocatalyst 5,10,15,20-tetraphenyl-21H,23H-porphine zinc, and 50 μL of initiator 2,2-diethoxyacetophenone were added. The molar ratio of the photocatalyst to the initiator was 1:16, and the amount of the photocatalyst was 0.10% (mass ratio) of the amount of the siloxane. The above components were mixed evenly to obtain a release agent B.

[0060] (2) The release agent B was evenly coated on the surface of the PET substrate layer, and irradiated with visible light at a temperature of 20°C under argon as a protective atmosphere for 3 hours to obtain a photocurable release film B, the thickness of which was 38 μm.

[0061] Example 3

[0062] The catalyst used is the same as in Example 1

[0063] The preparation method of the light-curing release film C is as follows:

[0064] (1) 6 g of hexenyl polydimethylsiloxane with a number average molecular weight of about 40W and 4 g of hydrogen-containing siloxane were mixed evenly, 0.8 mL of fluorinated acrylic monomer 2,2,2-trifluoroethyl acrylate was added, 20 mg of photocatalyst 5,10,15,20-tetraphenyl-21H,23H-porphine zinc was added, and 50 μL of initiator diphenylacetophenone alcohol was added. The molar ratio of the photocatalyst to the initiator was 1:8, and the amount of the photocatalyst was 0.20% (mass ratio) of the amount of the siloxane. The above components were mixed evenly to obtain a release agent C;

[0065] (2) The release agent C was evenly coated on the surface of the PET substrate layer, and irradiated with visible light at a temperature of 40°C under argon as a protective atmosphere for 1 hour to obtain a photocurable release film C, the thickness of which was 45 μm.

[0066] Example 4

[0067] The photocatalyst used in this embodiment has the following structural formula:

[0068]

[0069] The preparation method of the light-curing release film D is as follows:

[0070] (1) 6 g of hexenyl polydimethylsiloxane with a number average molecular weight of about 40 W and 4 g of hydrogen-containing siloxane were mixed evenly, 0.8 mL of fluorinated acrylic monomer 2,2,2-trifluoroethyl acrylate, 20 mg of photocatalyst 5,10,15,20-tetra(4-pyridyl)porphyrin iron, and 50 μL of initiator 2,2-diethoxyacetophenone were added, the molar ratio of photocatalyst to initiator was 1:8, and the amount of photocatalyst was 0.20% (mass ratio) of the amount of siloxane. The above components were mixed evenly to obtain a release agent D;

[0071] (2) The release agent D was evenly coated on the surface of the PET substrate layer, and irradiated with visible light at a temperature of 20°C under argon as a protective atmosphere for 3 hours to obtain a photocurable release film D, the thickness of which was 38 μm.

[0072] Comparative Example 1

[0073] Comparative Example 1 is based on Example 1, except that no catalyst is added to the release agent.

[0074] Comparative Example 2

[0075] Comparative Example 2 is based on Example 1, except that no fluorine-containing acrylic monomer is added to the release agent.

[0076] The prepared release film E showed a static water contact angle of about 80°. Compared with Example 1, it can be found that the addition of fluorine-containing acrylic monomer can significantly improve the hydrophobicity of the release film.

[0077] Comparative Example 3

[0078] The photocatalyst used is tris(2-phenylpyridyl)iridium.

[0079] The preparation method of the light-curing release film F is as follows:

[0080] (1) 6 g of hexenyl polydimethylsiloxane with a number average molecular weight of about 40 W and 4 g of hydrogen-containing siloxane were mixed evenly, 0.8 mL of fluorinated monomer 2,2,2-trifluoroethyl acrylate, 16 mg of photocatalyst tris(2-phenylpyridyl)iridium, and 50 μL of initiator 2,2-diethoxyacetophenone were added, the molar ratio of the photocatalyst to the initiator was 1:10, and the amount of the photocatalyst was 0.16% (mass ratio) of the amount of the siloxane. The above components were mixed evenly to obtain a release agent E;

[0081] (2) The release agent F was evenly coated on the surface of the PET substrate layer, and irradiated with visible light at a temperature of 20° C. under argon as a protective atmosphere for 3 hours to obtain a light-curable release film F.

[0082] The photocurable release films obtained in Examples 1-4 and Comparative Examples 1-3 were subjected to peel force testing. Thickness range and transmittance testing were performed on Example 1, Example 4, and Comparative Example 3. The results are shown in Table 1. The peel force test was conducted using the standard GB / T 25256-2010, and the thickness test was conducted using the standard ASTM D882-18-2018.

[0083] Table 1 Summary of performance results of release films prepared in Examples 1-4 and Comparative Examples 1-2

[0084]

[0085] It can be seen from the performance data in Table 1 that the release film provided by the present invention has low peeling force, good light transmittance and uniform thickness distribution.

[0086] Comparing the results of Example 1, Example 2, and Comparative Example 1 reveals that the catalyst plays a crucial role in curing. Without the addition of a catalyst, curing failed. However, increasing the amount of catalyst significantly improved the performance of the resulting release film. When using 20 mg of the catalyst, 5,10,15,20-tetraphenyl-21H,23H-porphine zinc, the 24-hour peel force was as low as 4.7 g / 25 mm at room temperature, and 6.7 g / 25 mm at 70°C.

[0087] Comparing the results of Examples 1 and 4 with Comparative Example 3 demonstrates that the non-precious metal catalysts used in this invention perform at least as well as precious metal catalysts. The release film prepared using the zinc-based catalyst outperforms the precious metal iridium, while the release film prepared using the iron-based catalyst performs similarly to the precious metal iridium. This demonstrates the excellent performance of the non-precious metal catalysts used in this invention and their potential to replace precious metal catalysts. The resulting release films all exhibited transmittance exceeding 90% and a uniform thickness distribution, suitable for use near polarizers.

[0088] Comparing the results of Example 1 and Example 3 reveals that the performance of the release films obtained differs when different initiators are used. This may be due to the differences in the initiators, but the performance of the release films remains at a leading level. Comparing the results of Example 1 and Comparative Example 2 shows that the fluorinated acrylic monomer added in the present invention has little effect on the release film's peel force, but the fluorinated acrylic monomer affects the film's hydrophobicity.

[0089] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A light-curing release agent, characterized in that: Including the following raw materials by weight: Siloxane 82–88%, of which hexenyl polydimethylsiloxane accounts for more than 60wt% and the rest is hydrogen-containing siloxane; Fluorinated acrylic monomer 5–10%; Catalyst 0.1–2%; Initiator 0.5–6%; The molecular structure of the catalyst is shown in formula (1) or formula (2): Wherein, M is selected from metal zinc, iron or copper; R4 is selected from 4-pyridyl or phenyl, R5 is selected from ethyl, and R6 is selected from methyl or ethyl.

2. The light-curing release agent according to claim 1, characterized in that: The number average molecular weight of the siloxane is 200,000-1,000,000.

3. The light-curing release agent according to claim 1, characterized in that: The initiator is one or more of diphenylacetophenone alcohol, 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropanone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

4. The light-curing release agent according to claim 1, characterized in that: The structural formula of the fluorinated acrylic monomer is shown in formula (3): Wherein, R7 is selected from H or methyl, and R8 is selected from H or methyl.

5. A release film with low peeling force and high light transmittance, characterized in that: The invention comprises a substrate and a light-curing release agent as claimed in any one of claims 1 to 4 coated on one side of the substrate.

6. The low peeling force and high transmittance release film according to claim 5, characterized in that: The substrate material is PET, and the thickness of the release agent layer is 30–50 μm.

7. A method for preparing a release film with low peel force and high light transmittance according to claim 5 or 6, comprising the following steps: (1) Mixing siloxane, fluorinated acrylic monomer, catalyst, and initiator according to the ratio, stirring evenly to obtain a release agent; (2) The release agent prepared in step (1) is evenly coated on the substrate and exposed to light under a protective atmosphere to obtain a release film.

8. The method for preparing a release film with low peeling force and high light transmittance according to claim 7, wherein: The molar ratio of initiator to catalyst was (3–16):

1.

9. The method for preparing a release film with low peeling force and high light transmittance according to claim 7, wherein: The reaction temperature for illumination is 5–50°C, and the reaction time is 1–10 hours.

10. The method for preparing a release film with low peeling force and high light transmittance according to claim 7, wherein: The light source of the illumination is visible light.

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