Polyurethane blue light protection optical material and preparation method thereof

Abstract

The invention discloses a polyurethane blue light protection optical material and a preparation method thereof. The polyurethane blue light protection optical material is formed by polymerizing a three-component system of isocyanate, a thiopropane trithiol compound and a light absorber mixture, has the advantages of high refractive index and high light transmittance, also has excellent blue light selective protection capability, can perform accurate regulation and control protection on blue light with different wavelengths of 385-500nm, and has good application prospects. The refractive index of an optical lens made of the blue-light-resistant material is larger than or equal to 1.71, the transmittance of short-wave blue light of 385-445 nm is smaller than or equal to 32.2%, the transmittance of long-wave blue light of 475-500 nm is larger than or equal to 70%, the transmittance of visible light of 600-780 nm is larger than or equal to 90%, and a wider material selection range is provided for application of high-end blue-light-resistant optical components.

Description

Technical Field

[0001] The present invention belongs to the technical field of polythiocarbamate optical materials, and particularly relates to a polyurethane blue light protection optical material and a preparation method thereof. Background Art

[0002] I. Blue Light Hazards and Protection Requirements

[0003] With the popularization of electronic devices, the harm of blue light to the eyes has received increasing attention. Research shows that high-energy blue light with a wavelength of 400 - 440 nm can penetrate the lens and reach the retina directly, generating free radicals, leading to the apoptosis of retinal pigment epithelial cells, and further causing vision damage. However, blue light above 460 nm has a positive effect on the regulation of the human biological clock. Therefore, blue light protection materials need to block harmful blue light while retaining the transmittance of beneficial blue light to achieve precise protection.

[0004] II. Advantages of Polyurethane Materials

[0005] In the field of optical materials, polyurethane optical materials have been widely used in high-end optical fields such as optical lenses, instrument prisms, LED lighting, intelligent vehicles, and light protection due to their unique advantages, such as high light transmittance, good mechanical properties, and processing properties. As an intermediate with a special structure in polyurethane optical materials, trithiol compounds have obvious advantages in refractive index, transparency, stability, and environmental friendliness. In recent years, the application of polyurethane optical resins in fields such as spectacle lenses and optical films has gradually increased, becoming an important development direction of blue light protection materials.

[0006] III. Existing Technical Routes and Limitations

[0007] Currently, blue light protection technologies are mainly divided into the absorption method and the reflection method. The absorption method achieves blue light blocking by adding blue light absorbers (such as benzotriazole compounds, etc.) to the material, but there are problems such as difficult dose control, easy migration, and yellowing of the lens; the reflection method achieves blue light reflection through optical coating technology, but it will cause secondary glare damage, and the process is complex and the cost is high.

[0008] In summary, aiming at the deficiencies of the existing technology, developing a new type of high-refractive-index polyurethane blue light protection optical material to achieve precise filtering and blocking of harmful blue light with a wavelength of 400 - 440 nm, while retaining the transmittance of beneficial blue light above 460 nm. Solving the above problems existing in the existing technology is of great significance for promoting the further application and development of polyurethane optical materials in the high-end optical protection field. Summary of the Invention

[0009] In view of the above problems of the prior art, the present invention provides a polyurethane blue light protection optical material and a preparation method thereof. The polyurethane blue light protection optical material is composed of a three-component system of isocyanate, thiopropane trithiol compound and light absorber mixture, which combines high refractive index and excellent blue light protection performance, and can accurately regulate and protect blue light with different wavelengths of 385-500 nm. The blue light protection optical lens made thereof has a short-wave blue light transmittance of 385-445 nm ≤ 32.2%, a long-wave blue light transmittance of 475-500 nm ≥ 70%, a visible light transmittance of 600-780 nm ≥ 90%, and a refractive index ≥ 1.71, providing a wider range of material selection for the application of high-end blue light protection optical components.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] On the one hand, the present invention provides a polyurethane blue light protection optical material, which is polymerized from the following components:

[0012] Component A: Isocyanate, 30-50 parts by weight;

[0013] Component B: The thiopropane trithiol compound shown in Formula I, 20-50 parts by weight;

[0014] Component C: Light absorber mixture, 0.5-5 parts by weight;

[0015]

[0016] Among them, the light absorber mixture includes: uracil compound A, ultraviolet absorber, solvent and acrylate;

[0017]

[0018] The polyurethane blue light protection optical material as described above, preferably, the isocyanate is selected from at least one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), xylene diisocyanate (XDI), diphenyl ether diisocyanate, triphenylmethane triisocyanate, cyclohexane diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, diethylene diisocyanate, tetramethylene diisocyanate, benzylidene diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate (IPDI), dithiobispropyl diisocyanate, trimethylhexamethylene diisocyanate, thiodihexyl diisocyanate, dithiobisethyl diisocyanate, thiodipropyl diisocyanate, lysine triisocyanate, o-tolidine diisocyanate, etc.

[0019] The polyurethane blue light protection optical material as described above, preferably, the weight ratio among the uracil compound A, the ultraviolet absorber, the solvent and the acrylate is (1-3):(1-3):(7-15):(10-30).

[0020] The polyurethane blue light protection optical material as described above, preferably, the ultraviolet absorber is at least one of UV-9, UV-21, UV-326, UV-327, UV-328, UV-329, UV-360 and UV-928.

[0021] The polyurethane blue light protection optical material as described above, preferably, the solvent is selected from at least one of acetonitrile, chloroform, petroleum ether, n-hexane, dichloromethane, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, dimethylacetamide and N-methylpyrrolidone.

[0022] The polyurethane blue light protection optical material as described above, preferably, the acrylate compound is selected from at least one of methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, pentaerythritol tetraacrylate, ethoxylated nonylphenol acrylate, epoxy acrylate, bisphenol A epoxy acrylate and ethoxylated bisphenol A diacrylate, etc.

[0023] On the other hand, the present invention provides a preparation method of the polyurethane blue light protection optical material as described above, and the method comprises the following steps:

[0024] (1) Mix components A to C evenly according to the proportion, and add 0.1-1.5% of internal mold release agent phosphate ester based on the total weight.

[0025] (2) Add a catalyst to the mixture obtained in the above step (1), pre-polymerize at 35-60 °C for 30-60 min, simultaneously remove bubbles under vacuum, and inject into a lens mold.

[0026] (3) Place the mold containing the prepolymer at 50-80 °C for 3-12 hours, then raise the temperature to 80-100 °C at a rate of (5 °C - 12 °C) / 30 min, continue to place for 2-5 hours, and finally cool to room temperature and demold to obtain the polyurethane blue light protection optical material.

[0027] For the preparation method as described above, preferably, the phosphate ester is stearyl alcohol polyether-2 phosphate ester or isooctyl phosphate.

[0028] The preparation method as described above, preferably, the amount of the catalyst is 0.1 to 0.5 wt% of the isocyanate; the catalyst is selected from one of stannous octoate, dibutyltin dilaurate, dibutyltin dichloride, and dibutyltin oxide.

[0029] The preparation method as described above, preferably, step (2) further includes adding a light absorber toner, an initiator, and / or a curing agent.

[0030] The thio propane trithiol compound of the present invention can be prepared by the following method:

[0031] I. Add mercaptopropylene glycol and a solvent to a reaction vessel equipped with a stirrer, a gas pipe, and a temperature control device. Start stirring and continuously introduce nitrogen. Stir and add a sulfur halide reagent. The weight ratio of the sulfur halide reagent, mercaptopropylene glycol, and the solvent is (1 - 2):(2 - 7):(10 - 30); control the temperature at 0 - 10 °C and stir for 5 - 10 hours. Separate and wash the organic phase, and remove the solvent by vacuum distillation to obtain the thio polyol shown in formula II;

[0032]

[0033] II. Add the thio polyol, thiosemicarbazide, and hydrochloric acid to a reactor equipped with a stirrer and a temperature control microwave generator. The weight ratio of thiosemicarbazide, thio polyol, and hydrochloric acid is (1 - 2):(1 - 3):(1 - 3); after stirring evenly, heat with microwave to 75 - 110 °C, keep warm for 6 - 9 h, and then let the mixture cool naturally;

[0034] III. When the mixture cools to 30 - 45 °C, add an alkali hydrolyzing agent. The amount of the alkali hydrolyzing agent is 90 - 150 wt% of the amount of hydrochloric acid used in step II. Heat and keep warm at 45 - 65 °C for hydrolysis for 2 - 3 h, let it stand until the system is stratified. The organic phase is adsorbed and decolorized with attapulgite, filtered, and the organic solvent is removed by vacuum distillation to obtain a colorless and transparent thio propane trithiol compound.

[0035] The preparation method as described above, preferably, the sulfur halide reagent in step I is selected from one of disulfur dichloride, sulfur chloride, disulfur dibromide, and sulfur bromide.

[0036] The preparation method as described above, preferably, the alkali hydrolyzing agent in step III is selected from ammonia water with a concentration of 25 - 40 wt%, sodium carbonate, or an aqueous solution of potassium carbonate.

[0037] The uracil compound A of the present invention can be prepared by the following method: Add 5-vinyluracil and a solvent with a boiling point higher than 150 °C to a reaction vessel in a weight ratio of (1-3):(100-300). After complete dissolution, add an alkaline aqueous solution dropwise to adjust the pH value ≥ 8.0. Then, introduce vinyl chloride gas into the solution, heat to 50-100 °C, add a palladium catalyst dropwise, continue the reaction for 5-12 h, stop ventilation, add water, extract with dichloromethane, combine the organic phases, dry with anhydrous sodium sulfate, and perform column chromatography of the crude product with dichloromethane / methanol to obtain a white powder of N-vinyl-5-vinyluracil compound.

[0038] The beneficial effects of the present invention are as follows:

[0039] 1. The raw materials for synthesizing the polyurethane of the present invention include a propane trithiol compound (Formula I), and a polyurethane optical material with high light transmittance and refractive index can be obtained. The visible light transmittance at 600-780 nm is ≥ 90%, and the refractive index is ≥ 1.71.

[0040] 2. The light absorber mixture of the present invention contains uracil compound A and an ultraviolet absorber. The uracil compound A has a stable N-C bond in the molecule, and the molecular structure is stable. It can remain stable during the polyurethane polymerization reaction, and has good high-temperature and ultraviolet resistance. At the same time, the π-π conjugate structure in the uracil ring enables it to absorb light of a specific wavelength. The presence of vinyl enhances the conjugate effect of the molecule, and it interacts synergistically with conventional ultraviolet absorbers. It can differentially absorb blue light of different wavelengths in the range of 385-500 nm, has high absorption and low transmittance for short-wave blue light in the range of 385-445 nm, and has low absorption and high refractive ratio for long-wave blue light in the range of 475-500 nm. Thus, precise regulation and protection of blue light are achieved, which helps to regulate the human biological clock and avoid color deviation and visual discomfort. Description of the Drawings

[0041] Figure 1 Spectral diagrams of the blue light-blocking lenses prepared in Example 1 and Example 4. Detailed Embodiments

[0042] The present invention will be further described below through specific examples, but it does not mean limiting the protection scope of the present invention.

[0043] Preparation Example 1 Preparation of Propane Trithiol Compound

[0044] Add 900 g of thiopropylene glycol, 1150 g of ethyl ether, and 1900 g of acetone to a reaction vessel equipped with a stirrer, a gas inlet pipe, and a temperature control device. Under N2 protection, slowly stir and add 245 g of sulfur dichloride within 10 min. Control the temperature with ice water at 2 °C. After stirring and reacting for 9 h, separate and wash the organic phase, and distill the solvent under reduced pressure to obtain 1010 g of a thio polyol (Formula II).

[0045] The prepared thio-polyol was added to a reactor equipped with a stirrer and a temperature-controlled microwave generator. 650 g of thiosemicarbazide and 920 g of 35% hydrochloric acid were added with stirring. After stirring evenly, it was heated to 95 °C by microwave, kept warm for 7 h and then cooled naturally. When the mixed solution was cooled to 45 °C, 1300 g of 36 wt% sodium carbonate aqueous solution was added dropwise, and the addition was completed within 30 min. It was heated to 60 °C for hydrolysis for 2.5 h, allowed to stand for layering, the organic phase was washed with water and then adsorbed and decolorized with attapulgite, filtered, and the organic solvent was removed under reduced pressure to obtain 1120 g of a colorless and transparent thio-propane trithiol compound (Formula I).

[0046] FT-IR test of infrared spectrum: The product prepared in Preparation Example 1 was tested by Fourier transform infrared spectrum (FT-IR). At 2944 cm -1 was the absorption peak of methylene (-CH2-), and the absorption peak at 2560 cm -1 was the characteristic peak of mercapto group. The absorption peak at 915 - 632 cm -1 was the bending vibration absorption peak of S-H group, and the absorption peak at 710 cm -1 was the stretching vibration of C-S bond.

[0047] 1H NMR nuclear magnetic resonance hydrogen spectrum analysis: The multiplet at δ = 2.97 - 3.06 ppm was the CH peak adjacent to S, the mixed peak displacement caused by mercapto H atom and secondary carbon H atom was at 2.50 - 2.82 ppm, and the characteristic triplet of SH appeared at δ = 1.78 - 1.82 ppm.

[0048] Preparation Example 2 Preparation of uracil compound A

[0049] 100 g of 5-vinyluracil was added to a reaction vessel containing 25000 g of dimethylformamide solvent. After stirring until completely dissolved, 36 wt% NaOH solution was added dropwise to adjust the pH value ≥ 8.0. Vinyl chloride gas was introduced into the solution, and the reaction was carried out at 85 °C. 0.2 g of dibenzylideneacetone dipalladium catalyst was added dropwise within 50 min, and the reaction was continued for 8 h and then the gas supply was stopped. After adding water, it was extracted with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, and the crude product was subjected to column chromatography of dichloromethane / methanol to obtain 112.3 g of white N-vinyl-5-vinyluracil (Formula A) powder. The yield was 88.2%.

[0050] FT-IR test of infrared spectrum: The product prepared in Preparation Example 2 was tested by Fourier transform infrared spectrum (FT-IR). From the curve analysis, the N-H stretching vibration peak (broad peak) was at 3240 - 3397 cm -1 ; the stretching vibration absorption peak of C-H bond was at 2852 - 3100 cm -1 ; and the absorption peak at 1705 - 1752 cm -1It is the stretching vibration absorption peak of the carbonyl group (C=O) on the uracil ring; 1623 - 1682 cm -1 The region at is the stretching vibration absorption peak of C=C; 1523 - 1601 cm -1 The absorption peak at is for the pyrimidine ring skeleton vibration; 1260 - 1365 cm -1 The absorption peak at is for the C-N stretching vibration.

[0051] 1H NMR nuclear magnetic resonance hydrogen spectrum analysis: δ = 10.71 - 10.13 (br s, 1H, N-H); 7.82 (s, 1H, C-H); 5.12 - 5.74 (d, 3H, CH2=CH); 5.89 - 6.46 (dd, 3H, CH2=CH).

[0052] Preparation Example 3 Preparation of the light absorber mixture

[0053] 5.5 g of uracil compound A and 4.2 g of UV-326 ultraviolet absorber were added to a mixed solvent of 6.8 g of dichloromethane and 12 g of N-methylpyrrolidone solvent, and then 40 g of methyl acrylate was added thereto, and the mixture was stirred evenly to obtain 68.5 g of the light absorber mixture.

[0054] The thiopropane trithiol compound and the light absorber mixture required for the following examples were all taken from Preparation Example 1 and Preparation Example 3.

[0055] Example 1 Preparation of anti-blue light lenses

[0056] 180 g of diphenylmethane diisocyanate, 170 g of thiopropane trithiol compound and 4.2 g of the light absorber mixture were mixed evenly, and 1.75 g of polyoxyethylene (2) stearyl ether phosphate and 0.5 g of dibutyltin dilaurate were added; the temperature was raised to 45 °C for pre-polymerization for 40 min, the bubbles were removed under vacuum, and then it was injected into the lens mold; the mold containing the prepolymer was placed at 60 °C for 8 hours, then raised to 90 °C at a rate of 10 °C / 30 min, and continued to be placed for 2.5 hours, and finally cooled to room temperature and demolded to obtain a high refractive index polyurethane anti-blue light lens.

[0057] Example 2

[0058] 170 g of tolylene diisocyanate, 180 g of thiopropane trithiol compound and 3.5 g of the light absorber mixture were mixed evenly, and 1.7 g of phosphate ester and 0.5 g of dibutyltin dilaurate were added; the temperature was raised to 45 °C for pre-polymerization for 40 min, the bubbles were removed under vacuum, and then it was injected into the lens mold; the mold containing the prepolymer was placed at 60 °C for 8 hours, then raised to 90 °C at a rate of 10 °C / 30 min, and continued to be placed for 2.5 hours, and finally cooled to room temperature and demolded to obtain a high refractive index polyurethane anti-blue light lens.

[0059] Example 3

[0060] Mix 180 g of xylene diisocyanate, 175 g of thiopropane trithiol compound and 2.8 g of light absorber mixture evenly, add 1.8 g of phosphate ester and 0.6 g of dibutyltin dilaurate; raise the temperature to 45 °C and pre-polymerize for 40 min, while removing bubbles under vacuum, and inject into the lens mold; place the mold containing the prepolymer at 60 °C for 8 hours, then raise the temperature to 90 °C at a rate of 10 °C / 30 min, continue to place for 2.5 hours, and finally cool to room temperature and demold to obtain a high refractive index polyurethane anti-blue light lens.

[0061] Example 4

[0062] Mix 170 g of diphenylmethane diisocyanate, 200 g of thiopropane trithiol compound and 6.5 g of light absorber mixture evenly, add 1.85 g of phosphate ester and 0.55 g of dibutyltin dilaurate, raise the temperature to 45 °C and pre-polymerize for 40 min, while removing bubbles under vacuum, and inject into the lens mold. Place the mold containing the prepolymer at 60 °C for 8 hours, then raise the temperature to 90 °C at a rate of 10 °C / 30 min, continue to place for 2.5 hours, and finally cool to room temperature and demold to obtain a high refractive index polyurethane anti-blue light lens.

[0063] Example 5

[0064] Mix 170 g of toluene diisocyanate, 190 g of thiopropane trithiol compound and 5.5 g of light absorber mixture evenly, add 1.85 g of phosphate ester and 0.5 g of dibutyltin dilaurate; raise the temperature to 45 °C and pre-polymerize for 40 min, while removing bubbles under vacuum, and inject into the lens mold; place the mold containing the prepolymer at 60 °C for 8 hours, then raise the temperature to 90 °C at a rate of 10 °C / 30 min, continue to place for 2.5 hours, and finally cool to room temperature and demold to obtain a high refractive index polyurethane anti-blue light lens.

[0065] Example 6

[0066] Mix 180 g of diphenylmethane diisocyanate, 165 g of thiopropane trithiol compound and 5 g of light absorber mixture evenly, add 1.85 g of phosphate ester and 0.6 g of dibutyltin dilaurate; raise the temperature to 40 °C and pre-polymerize for 45 min, while removing bubbles under vacuum, and inject into the lens mold; place the mold containing the prepolymer at 60 °C for 8 hours, then raise the temperature to 90 °C at a rate of 10 °C / 30 min, continue to place for 2.5 hours, and finally cool to room temperature and demold to obtain a high refractive index polyurethane anti-blue light lens.

[0067] Optical Property Detection Experiment of Anti-Blue Light Lens in Example 7

[0068] The optical properties of the anti-blue light lenses prepared in Examples 1-6 were respectively detected. For the transmittance detection, a UV-8000 type ultraviolet-visible spectrophotometer produced by Shanghai Yuanxi Instruments Co., Ltd. was used. Detection method: directly apply the compound monomer on the prism of the ultraviolet-visible spectrophotometer to measure the transmittance; for the refractive index detection, a WZS1 type refractometer produced by Shanghai Optical Instrument Equipment Co., Ltd. was used. Detection method: directly place the lens on the prism of the refractometer to measure the refractive index. The detection results are shown in Table 1 and Figure 1 .

[0069] Table 1 Detection of the optical properties of the sample lenses

[0070]

[0071] Conclusion: It can be seen from the detection spectral curve that the polyurethane anti-blue light lenses prepared by the present invention can differentially absorb blue light in the range of 385-500 nm, among which the transmittance of short-wave blue light of 385-445 nm is ≤ 32.2%, the transmittance of long-wave blue light of 475-500 nm is ≥ 70%, the transmittance of visible light of 600-780 nm is ≥ 90%, and the refractive index is ≥ 1.71. While maintaining a high refractive index and high transmittance, it has the performance of precisely regulating and protecting blue light of different wavelengths.

Claims

1. A polyurethane blue light protection optical material, characterized in that, It is polymerized from the following components: Component A: Isocyanate, 30-50 parts by weight; Component B: The thiopropane trithiol compound shown in Formula I, 20-50 parts by weight; Component C: Light absorber mixture, 0.5-5 parts by weight; Among them, the light absorber mixture includes: Uracil compound A, Ultraviolet absorber, Solvent and Acrylate; 2. The polyurethane blue light protection optical material according to claim 1, wherein The isocyanate is selected from at least one of toluene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, diphenyl ether diisocyanate, triphenylmethane triisocyanate, cyclohexane diisocyanate, 4,4'-diisocyanatodicyclohexylmethane, diethylenediisocyanate, tetramethylene diisocyanate, benzylidene diisocyanate, m-xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dithiodipropyl diisocyanate, trimethylhexamethylene diisocyanate, thiodihexyl diisocyanate, dithiodiethyl diisocyanate, thiodipropyl diisocyanate, lysine triisocyanate, o-tolidine diisocyanate, etc.

3. The polyurethane blue light protection optical material according to claim 1, characterized in that, The weight ratio among the Uracil compound A, Ultraviolet absorber, Solvent and Acrylate is (1-3):(1-3):(7-15):(10-30).

4. The polyurethane blue light protection optical material according to claim 1, wherein The Ultraviolet absorber is at least one of UV-9, UV-21, UV-326, UV-327, UV-328, UV-329, UV-360 and UV-928.

5. The polyurethane blue light protection optical material according to claim 1, wherein The Solvent is selected from at least one of acetonitrile, chloroform, petroleum ether, n-hexane, dichloromethane, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, dimethylacetamide and N-methylpyrrolidone.

6. The polyurethane blue light protection optical material according to claim 1, characterized in that, The Acrylate compounds are selected from at least one of methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, pentaerythritol tetraacrylate, ethoxylated nonylphenol acrylate, epoxy acrylate, bisphenol A epoxy acrylate and ethoxylated bisphenol A diacrylate, etc.

7. The preparation method of the polyurethane blue light protection optical material according to any one of claims 1-6, characterized in that, This method includes the following steps: (1) Mix components A to C evenly in proportion, and add 0.1-1.5% of internal mold release agent phosphate ester based on the total weight; (2) Add a catalyst to the mixture obtained in the above step (1), pre-polymerize at 35-60 °C for 30-60 min, and at the same time remove bubbles under vacuum, and inject it into the lens mold; (3) Place the mold containing the prepolymer at 50-80 °C for 3-12 hours, then raise the temperature to 80-100 °C at a rate of (5 °C - 12 °C) / 30 min, continue to place for 2-5 hours, and finally cool to room temperature and demold to obtain the polyurethane blue light protection optical material.

8. The preparation method according to claim 7, characterized in that, The phosphate ester is stearyl alcohol polyether-2 phosphate ester or isooctyl phosphate ester.

9. The preparation method according to claim 7 or 8, characterized in that, The dosage of the catalyst is 0.1-0.5 wt% of the isocyanate; the catalyst is selected from one of stannous octoate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin oxide.

10. The preparation method according to claim 7 or 8, characterized in that, The step (2) further includes adding a light absorber toner, an initiator, and / or a curing agent.

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