Low-phase-difference PMMA optical film and preparation method thereof

Abstract

The invention discloses a low-phase-difference PMMA optical film and a preparation method thereof, and belongs to the field of optical film materials. The low-phase-difference PMMA optical film is prepared from the following raw materials in parts by weight: 100 parts of PMMA resin; 6-8 parts of PC resin; 2.5 to 3.5 parts of a copolymer coated catalyst; the copolymer coated catalyst is formed by copolymerizing and coating bismaleimide diphenylmethane and an acrylate monomer on the surface of the ester exchange catalyst, and the mass ratio of the ester exchange catalyst to the bismaleimide diphenylmethane to the acrylate monomer is 1: (0.3-0.55): (2.2-2.8). The PMMA film has the advantages that the PMMA film is kept low in phase difference and high in light transmittance, and meanwhile the high temperature resistance of the PMMA film is improved.

Description

Technical Field

[0001] The present application relates to the field of optical films, and particularly to a low retardation PMMA optical film and a preparation method thereof. Background Art

[0002] PMMA, that is, polymethyl methacrylate, has been widely used in many fields due to its excellent transparency and good processing performance. Especially in the application of optical films, PMMA has become an important choice for manufacturing various optical components and devices with its excellent light transmittance, low retardation and low cost, and can be applied to projector lenses and key components in various optoelectronic devices.

[0003] A main disadvantage of PMMA is its poor high-temperature resistance, which limits its application in high-temperature environments. In order to improve the high-temperature resistance of PMMA films, people will use the method of blending high-temperature-resistant polymers with PMMA to improve the high-temperature resistance of PMMA films. And in order to maintain the low retardation of PMMA films, PC (polycarbonate) is a good blending choice.

[0004] However, due to the poor compatibility between PMMA and PC, the light transmittance of the PMMA film after blending with PC is greatly reduced, affecting its use in the optical field. Summary of the Invention

[0005] In order to improve the high-temperature resistance of PMMA films while maintaining the low retardation and high light transmittance of PMMA films, the present application provides a low retardation PMMA optical film and a preparation method thereof.

[0006] In the first aspect, a low retardation PMMA optical film provided by the present application adopts the following technical solution: A low retardation PMMA optical film is prepared from raw materials comprising the following parts by weight: 100 parts of PMMA resin; 6 - 8 parts of PC resin; 2.5 - 3.5 parts of copolymer-coated catalyst; The copolymer-coated catalyst is formed by copolymer coating of bis(maleimide)diphenylmethane and acrylate monomers on the surface of a transesterification catalyst, and the mass ratio of the transesterification catalyst, bis(maleimide)diphenylmethane and acrylate monomers is 1:(0.3 - 0.55):(2.2 - 2.8).

[0007] By adopting the above technical solution, under the action of the transesterification catalyst, part of the PMMA resin and the PC resin generate a compatible copolymer through transesterification reaction. The compatible copolymer can improve the compatibility between the PMMA resin and the PC resin, thereby enhancing the interfacial bonding force between the PMMA resin and the PC resin, increasing the light transmittance of the PMMA film, and improving the optical properties.

[0008] Coating the transesterification catalyst with bismaleimide diphenylmethane and acrylate monomers during the copolymerization process can play a role in moderating the transesterification reaction, improve the dispersibility of the transesterification catalyst, reduce problems such as inhomogeneity or chain segment breakage caused by excessive local transesterification reaction in the blend system, and the copolymer has high chain segment compatibility with the PMMA resin and the PC resin, further reducing the surface tension between the two phases, reducing interface scattering caused by phase separation, thereby improving the high-temperature resistance of the PMMA film while maintaining a low retardation and high light transmittance of the PMMA film.

[0009] Optionally, the transesterification catalyst includes an organotin catalyst or an inorganic tin catalyst.

[0010] By adopting the above technical solution, the tin-based catalyst is an effective transesterification reaction catalyst, which promotes the transesterification reaction between the PMMA resin and the PC resin during blending, generates a compatible copolymer, improves the compatibility between the PMMA resin and the PC resin, and increases the light transmittance of the PMMA film.

[0011] Optionally, the transesterification catalyst is selected as stannous chloride.

[0012] By adopting the above technical solution, stannous chloride, as one of the tin-based catalysts, has a good catalytic effect on the transesterification reaction between the PMMA resin and the PC resin, and is suitable for coating on the bismaleimide diphenylmethane-acrylate copolymer, and can be evenly dispersed while gently catalyzing the transesterification reaction.

[0013] Optionally, the acrylate monomer includes one or more of methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate.

[0014] By adopting the above technical solution, the above acrylate monomers form the chain segments of the copolymer, which are similar and compatible with the PMMA resin, improving the interfacial compatibility between the PMMA resin and the PC resin.

[0015] Optionally, the acrylate monomer is selected as propyl acrylate.

[0016] By adopting the above technical solution, using propyl acrylate as the acrylate monomer can effectively improve the flexibility of the chain segments while ensuring the interfacial bonding force of the blend system, playing a role in dispersing the stress, thereby improving the toughness of the PMMA film.

[0017] In a second aspect, the preparation method of a low retardation PMMA optical film provided by this application adopts the following technical solution: A preparation method of a low retardation PMMA optical film includes the following steps: Dissolve the acrylate monomer in an organic solvent, add bis(maleimide)diphenylmethane after heating, add a transesterification catalyst after dispersing evenly, then gradually add an initiator, filter, wash, and dry after the reaction ends to obtain a copolymer-coated catalyst; mix the PMMA resin, PC resin, and the copolymer-coated catalyst, melt the obtained blend, extrude, plasticize, calender, and draw and cool to shape to obtain a PMMA optical film.

[0018] By adopting the above technical solution, copolymerization is initiated to achieve the coating of the copolymer and the transesterification catalyst, and the PMMA resin and the PC resin are compatibilized by melt extrusion.

[0019] Optionally, in the step of preparing the copolymer-coated catalyst, add bis(maleimide)diphenylmethane after heating to 75 - 85 °C, add a transesterification catalyst after dispersing evenly, then raise the temperature to 90 - 95 °C and keep it warm for 1 - 1.5 h, while gradually adding an initiator, then raise the temperature to 100 - 105 °C and keep it warm for 0.5 - 1 h, end heating, cool, and filter.

[0020] By adopting the above technical solution, the method of gradient heating helps to improve the stability of the copolymer-coated catalyst, and it is not easy for the copolymer and the catalyst to separate during the high-speed mixing of the blend.

[0021] Optionally, in the step of preparing the copolymer-coated catalyst, the organic solvent includes one or more of benzene, toluene, and xylene.

[0022] Optionally, in the step of preparing the copolymer-coated catalyst, the initiator includes one or both of benzoyl peroxide and azobisisobutyronitrile.

[0023] Optionally, in the step of preparing the PMMA optical film, heat to 100 - 120 °C during the mixing process.

[0024] By adopting the above technical solution, heating during the mixing process helps to improve the blending uniformity.

[0025] In summary, this application has the following beneficial effects: 1. Under the action of the transesterification catalyst, in the blend system of the present application, part of the PMMA resin and the PC resin generate a compatible copolymer through transesterification reaction. The compatible copolymer can improve the compatibility between the PMMA resin and the PC resin, increase the light transmittance of the PMMA film, and encapsulate the transesterification catalyst during the copolymerization of bismaleimide diphenylmethane and acrylate monomer, which can play a role in moderating the transesterification reaction, improve the dispersion of the transesterification catalyst, and reduce problems such as inhomogeneity or chain segment breakage caused by excessive local transesterification reaction in the blend system. Moreover, the copolymer has high segment compatibility with the PMMA resin and the PC resin, further reducing the surface tension between the two phases and reducing the interfacial scattering caused by phase separation. Thus, while maintaining a low retardation and high light transmittance of the PMMA film, the high-temperature resistance of the PMMA film is improved.

[0026] 2. The present application uses propyl acrylate as the acrylate monomer, which can effectively improve the chain segment flexibility while ensuring the interfacial bonding force of the blend system, play a role in dispersing the stress, and thus improve the toughness of the PMMA film. Detailed implementation mode

[0027] The following further elaborates on the present application.

[0028] Example 1 A preparation method of a low retardation PMMA optical film includes the following steps: Weigh 100 g of transesterification catalyst, 30 g of bismaleimide diphenylmethane, 220 g of acrylate monomer, 30 g of initiator solution, and 1 L of organic solvent.

[0029] Among them, the transesterification catalyst is specifically stannous chloride; the acrylate monomer is specifically methyl methacrylate; the initiator solution is specifically a toluene solution containing 10 wt% initiator, and the initiator is specifically benzoyl peroxide; the organic solvent is specifically toluene.

[0030] Under nitrogen protection, dissolve the acrylate monomer in the organic solvent. After heating to 80 °C, add bismaleimide diphenylmethane. After dispersing evenly, add the transesterification catalyst. Then raise the temperature to 90 °C and keep it warm for 1.5 h. While keeping warm, gradually dropwise add the initiator solution, and the initiator solution is added dropwise within 0.5 h. Then raise the temperature to 100 °C and keep it warm for 1 h. End the heating, cool, filter, wash with toluene, and dry to obtain the copolymer-coated catalyst.

[0031] Weigh 10 kg of PMMA resin, 0.6 kg of PC resin, and 0.25 kg of copolymer-coated catalyst.

[0032] Among them, the PMMA resin is specifically Evonik 8N; the PC resin is specifically Teijin 1250Y.

[0033] Put PMMA resin, PC resin and copolymer-coated catalyst into a mixer and mix for 30 minutes. Heat to 100 °C during the mixing process. Put the obtained blend into an extruder for melting and extrusion. The temperature of the extruder is 260 °C, and the rotation speed of the extruder is 60 r / min. The extruded film is plasticized, calendered, and traction-cooled to a thickness of 50 μm to obtain a PMMA optical film.

[0034] Example 2 A method for preparing a low retardation PMMA optical film, comprising the following steps: Weigh 100 g of transesterification catalyst, 55 g of bismaleimide diphenylmethane, 280 g of acrylate monomer, 35 g of initiator solution, and 1 L of organic solvent.

[0035] Among them, the transesterification catalyst is specifically tin(II) chloride; the acrylate monomer is specifically methyl methacrylate; the initiator solution is specifically a toluene solution containing 10 wt% initiator, and the initiator is specifically benzoyl peroxide; the organic solvent is specifically toluene.

[0036] Under nitrogen protection, dissolve the acrylate monomer in the organic solvent. After heating to 80 °C, add bismaleimide diphenylmethane. After dispersing evenly, add the transesterification catalyst. After heating to 95 °C, keep warm for 1 h. While keeping warm, gradually dropwise add the initiator solution, and finish dropping the initiator solution in 0.5 h. Then heat to 105 °C and keep warm for 0.5 h. End the heating, cool, filter, wash with toluene, and dry to obtain a copolymer-coated catalyst.

[0037] Weigh 10 kg of PMMA resin, 0.8 kg of PC resin, and 0.35 kg of copolymer-coated catalyst.

[0038] Among them, the PMMA resin is specifically Evonik 8N; the PC resin is specifically Teijin 1250Y.

[0039] Put PMMA resin, PC resin and copolymer-coated catalyst into a mixer and mix for 30 minutes. Heat to 120 °C during the mixing process. Put the obtained blend into an extruder for melting and extrusion. The temperature of the extruder is 260 °C, and the rotation speed of the extruder is 60 r / min. The extruded film is plasticized, calendered, and traction-cooled to a thickness of 50 μm to obtain a PMMA optical film.

[0040] Example 3 A method for preparing a low retardation PMMA optical film, comprising the following steps: Weigh 100 g of transesterification catalyst, 0.5 g of bismaleimide diphenylmethane, 2.5 g of acrylate monomer, 3.5 g of initiator solution, and 1 L of organic solvent.

[0041] Among them, the transesterification catalyst is specifically stannous chloride; the acrylate monomer is specifically methyl methacrylate; the initiator solution is specifically a toluene solution containing 10 wt% initiator, and the initiator is specifically benzoyl peroxide; the organic solvent is specifically toluene.

[0042] Under nitrogen protection, the acrylate monomer is dissolved in the organic solvent. After heating to 80 °C, bis(maleimide)phenylmethane is added. After dispersing evenly, the transesterification catalyst is added. After raising the temperature to 90 °C, it is kept warm for 1.5 h. While keeping warm, the initiator solution is gradually added dropwise, and the initiator solution is added dropwise within 0.5 h. Then the temperature is raised to 100 °C and kept warm for 1 h. The heating is ended, cooled, filtered, washed with toluene, and dried to obtain the copolymer-coated catalyst.

[0043] Weigh 10 kg of PMMA resin, 0.7 kg of PC resin, and 0.29 kg of copolymer-coated catalyst.

[0044] Among them, the PMMA resin is specifically Evonik 8N; the PC resin is specifically Teijin 1250Y.

[0045] Put the PMMA resin, PC resin, and copolymer-coated catalyst into a mixer and mix for 30 min. During the mixing process, heat to 100 °C. The obtained blend is put into an extruder for melting and extrusion. The temperature of the extruder is 260 °C, and the rotation speed of the extruder is 60 r / min. The extruded film is plasticized, calendered, and traction-cooled to a thickness of 50 μm to obtain the PMMA optical film.

[0046] Example 4 A preparation method of a low birefringence PMMA optical film.

[0047] The difference between this example and Example 3 is that the acrylate monomer is specifically propyl methacrylate.

[0048] Example 5 A preparation method of a low birefringence PMMA optical film.

[0049] The difference between this example and Example 3 is that the acrylate monomer is specifically ethyl acrylate.

[0050] Example 6 A preparation method of a low birefringence PMMA optical film.

[0051] The difference between this example and Example 3 is that the acrylate monomer is specifically propyl acrylate.

[0052] Comparative Example 1 A preparation method of a PMMA optical film, including the following steps: Weigh 10 kg of PMMA resin and 0.7 kg of PC resin.

[0053] Among them, the PMMA resin is specifically Evonik 8N; the PC resin is specifically Teijin 1250Y.

[0054] Put the PMMA resin and PC resin into a mixer and mix for 30 min. During the mixing process, heat to 100 °C. Put the obtained blend into an extruder for melting and extrusion. The temperature of the extruder is 260 °C, and the rotation speed of the extruder is 60 r / min. The extruded film is plasticized, calendered, and traction-cooled to a thickness of 50 μm to obtain a PMMA optical film.

[0055] Comparative Example 2 A method for preparing a PMMA optical film includes the following steps: Weigh 10 kg of PMMA resin, 0.7 kg of PC resin, and 0.29 kg of catalyst.

[0056] Among them, the PMMA resin is specifically Evonik 8N; the PC resin is specifically Teijin 1250Y, and the catalyst is stannous chloride.

[0057] Put the PMMA resin, PC resin, and catalyst into a mixer and mix for 30 min. During the mixing process, heat to 100 °C. Put the obtained blend into an extruder for melting and extrusion. The temperature of the extruder is 260 °C, and the rotation speed of the extruder is 60 r / min. The extruded film is plasticized, calendered, and traction-cooled to a thickness of 50 μm to obtain a PMMA optical film.

[0058] Comparative Example 3 A method for preparing a PMMA optical film includes the following steps: Weigh 100 g of transesterification catalyst, 0.5 g of styrene, 2.5 g of acrylate monomer, 3.5 g of initiator solution, and 1 L of organic solvent.

[0059] Among them, the transesterification catalyst is specifically stannous chloride; the acrylate monomer is specifically methyl methacrylate; the initiator solution is specifically a toluene solution containing 10 wt% initiator, and the initiator is specifically benzoyl peroxide; the organic solvent is specifically toluene.

[0060] Under nitrogen protection, dissolve the acrylate monomer in the organic solvent. After heating to 80 °C, add styrene. After dispersing evenly, add the transesterification catalyst. After heating to 90 °C, keep warm for 1.5 h. While keeping warm, gradually dropwise add the initiator solution, and the initiator solution is added dropwise within 0.5 h. Then heat to 100 °C and keep warm for 1 h. End the heating, cool, filter, wash with toluene, and dry to obtain a copolymer-coated catalyst.

[0061] Weigh 10 kg of PMMA resin, 0.7 kg of PC resin, and 0.29 kg of copolymer-coated catalyst.

[0062] Among them, the PMMA resin is specifically Evonik 8N; the PC resin is specifically Teijin 1250Y.

[0063] Put the PMMA resin, PC resin and copolymer-coated catalyst into a mixer and mix for 30 min. During the mixing process, heat to 100 °C. The obtained blend is put into an extruder for melting and extrusion. The temperature of the extruder is 260 °C, and the rotation speed of the extruder is 60 r / min. The extruded film is plasticized, calendered, and traction-cooled to a thickness of 50 μm to obtain a PMMA optical film.

[0064] Performance testing Heat resistance stability test: Use a differential scanning calorimeter to test the glass transition temperature (Tg) of the PMMA optical film. The test process includes, under nitrogen protection, first heating each sample from 30 °C to 240 °C and keeping it at 240 °C for 4 min to eliminate the thermal history. Then cool down to 30 °C, and then heat up to 240 °C again. The heating rate and cooling rate are both 10 °C / min, and the test results are shown in Table 1.

[0065] Light transmittance test: Use a light transmittance tester to test the light transmittance of the PMMA optical film. The test results are shown in Table 1.

[0066] Phase difference: Use an Axoscan phase difference tester to test the phase difference of the PMMA optical film. The test results are shown in Table 1.

[0067] Toughness test: Make dumbbell-shaped specimens according to the composition of the PMMA optical film, and use a universal testing machine to test the elongation at break of the specimens. The test results are shown in Table 1.

[0068] Table 1 Combined with the test analysis in Table 1, compared with the film prepared by directly blending PMMA resin and PC resin in Comparative Example 1, the PMMA optical film in Example 3 has a higher light transmittance, and at the same time has a higher glass transition temperature and a lower phase difference. Therefore, the PMMA optical film has good optical properties and good high-temperature resistance.

[0069] Compared with Comparative Example 2, the PMMA optical film in Example 3 has a higher light transmittance and a greater advantage in glass transition temperature, indicating that the coating of the copolymer on the transesterification catalyst can reduce problems such as inhomogeneity or chain segment breakage caused by excessive local transesterification reactions in the blending system, thereby improving the high-temperature resistance.

[0070] Compared with Comparative Example 3, Example 3 has a higher glass transition temperature and a greater advantage in the light transmittance of the PMMA optical film, indicating that the copolymer is formed by copolymerizing bismaleimide diphenylmethane with acrylate monomers, has high compatibility with the blend system, further reduces the interfacial scattering caused by phase separation, and thus improves the light transmittance of the PMMA optical film.

[0071] Compared with Example 3, Example 4, and Example 5, the PMMA optical film of Example 6 has a greater improvement in the elongation at break, indicating that when the acrylate monomer in the copolymer is propyl acrylate, the toughness of the PMMA optical film is improved due to the increased flexibility of the chain segments.

[0072] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this specific embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A low phase difference PMMA optical film, characterized in that: It is prepared from the following raw materials in parts by weight: 100 parts of PMMA resin; 6~8 parts of PC resin; 2.5-3.5 parts of copolymer-coated catalyst; The copolymer-coated catalyst is formed by copolymerizing and coating bismaleimide diphenylmethane and acrylate monomer on the surface of an ester exchange catalyst. The mass ratio of the ester exchange catalyst, bismaleimide diphenylmethane and acrylate monomer is 1:(0.3-0.55):(2.2-2.8).

2. The low phase difference PMMA optical film according to claim 1, characterized in that: The transesterification catalyst includes an organic tin catalyst or an inorganic tin catalyst.

3. The low phase difference PMMA optical film according to claim 1, characterized in that: The transesterification catalyst is stannous chloride.

4. The low phase difference PMMA optical film according to claim 1, characterized in that: The acrylic acid ester monomer includes one or more of methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate and propyl methacrylate.

5. The low phase difference PMMA optical film according to claim 1, characterized in that: The acrylic acid ester monomer is selected from propyl acrylate.

6. A method for preparing a low phase difference PMMA optical film according to any one of claims 1 to 5, characterized in that: The following steps are involved: The acrylate monomer is dissolved in an organic solvent, bismaleimide diphenylmethane is added after heating, and after being evenly dispersed, an ester exchange catalyst is added, and then an initiator is gradually added. After the reaction is completed, the catalyst is filtered, washed, and dried to obtain a copolymer-coated catalyst. PMMA resin, PC resin and copolymer-coated catalyst are mixed, the obtained blend is melted, extruded, plasticized, calendered, pulled, cooled and shaped to obtain a PMMA optical film.

7. The method for preparing a low phase difference PMMA optical film according to claim 6, characterized in that: In the step of preparing the copolymer-coated catalyst, bismaleimide diphenylmethane is added after heating to 75-85°C, and after being evenly dispersed, an ester exchange catalyst is added, and then the temperature is raised to 90-95°C and kept warm for 1-1.5 hours, and an initiator is gradually added at the same time, and then the temperature is raised to 100-105°C and kept warm for 0.5-1 hour, and the heating is terminated, cooled, and filtered.

8. The method for preparing a low phase difference PMMA optical film according to claim 6, characterized in that: In the step of preparing the copolymer-coated catalyst, the organic solvent includes one or more of benzene, toluene and xylene.

9. The method for preparing a low phase difference PMMA optical film according to claim 6, characterized in that: In the step of preparing the copolymer-coated catalyst, the initiator includes one or both of benzoyl peroxide and azobisisobutyronitrile.

10. The method for preparing a low phase difference PMMA optical film according to claim 6, characterized in that: In the step of preparing the PMMA optical film, the material is heated to 100-120° C. during the mixing process.

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