High-reflectivity ink with yellowing resistance

Abstract

The invention relates to high-reflectivity ink with yellowing resistance, which is composed of a main agent and a curing agent, the main agent and the curing agent are in a mass ratio of (2-4): 1, the main agent comprises the following components in parts by weight: 27-40 parts of acrylic resin, 30-40 parts of titanium dioxide, 0.1-1.2 parts of fluorescent whitening agent and 2-4 parts of photoinitiator; the acid value of the acrylic resin composition is 30-50 mgKOH / g, and the acrylic resin is styrene-free copolymerized acrylate resin; the curing agent is prepared from 6.5 to 8 parts of epoxy resin, 3.8 to 4.2 parts of triglycidyl isocyanurate and 0.2 to 0.7 part of melamine.

Description

Technical Field

[0001] This invention relates to the technical field of high reflectivity inks, and particularly to a high reflectivity ink with anti-yellowing properties. Background Technology

[0002] In optoelectronic devices such as photovoltaic cells and LEDs, high-reflectivity white ink is widely used in backplanes, encapsulation layers of LED chips, and reflectors. The core function of this ink is to efficiently reflect unused light back, thereby significantly improving the overall light output efficiency and performance of the device. Therefore, the key performance requirements for this type of ink focus on two points: first, extremely high reflectivity (typically ≥90%); and second, excellent weather resistance and yellowing resistance to ensure that the device maintains color stability and does not yellow significantly during long-term use or high-temperature processes.

[0003] In the CIE Lab colorimetric system, the yellow and blue axes are coordinated, with a positive B value indicating a yellowish tint. However, commercially available high-reflectivity white inks generally face a technical dilemma: their color parameter B value is often too high (B value is usually >1.5), resulting in a yellowish visual appearance, insufficient initial whiteness, and long-term yellowing resistance that is difficult to meet the needs of high-end applications.

[0004] To reduce the B-value and improve whiteness, the industry's conventional technique is to add blue pigments such as phthalocyanine blue for hue compensation. However, this method of using blue pigments for hue compensation has the following inherent drawbacks: blue pigments have a strong absorption effect on visible light other than the blue light band. Although the B-value is reduced by reflecting blue light, it severely sacrifices the overall light reflectivity, which contradicts the fundamental requirement of high reflectivity and affects the light reflectivity of high-reflectivity inks. Existing technologies struggle to achieve a synergistic improvement in excellent initial visual whiteness and long-term resistance to yellowing while maintaining extremely high ink reflectivity. This has become a technical bottleneck restricting further performance improvements in high-end optoelectronic devices.

[0005] Therefore, developing a white ink that can simultaneously achieve high reflectivity and low yellowing properties has both urgent market demand and significant technological value. Summary of the Invention

[0006] One embodiment of the present invention provides a high reflectivity ink with anti-yellowing properties, which is composed of a main agent and a curing agent. The main agent and the curing agent are in a mass ratio of (2-4):1. By weight, the main agent contains the following components: 27-40 parts of acrylic resin, 30-40 parts of titanium dioxide, 0.1-1.2 parts of fluorescent whitening agent, and 2-4 parts of photoinitiator; wherein the acrylic resin has an acid value of 50-60 mgKOH / g and is a styrene-free copolyacrylate resin; the curing agent contains 6.5-8 parts of epoxy resin, 3.8-4.2 parts of triglycidyl isocyanate, and 0.2-0.7 parts of melamine.

[0007] Preferably, the styrene-free copolyacrylate resin is a copolymer of methyl methacrylate and butyl acrylate.

[0008] Preferably, the titanium dioxide is rutile titanium dioxide.

[0009] Preferably, the photoinitiator is composed of 1.6-2.4 parts of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 0.8-1.2 parts of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 0.01-0.05 parts of bis2,6-difluoro-3-pyrrolephenyldicyclopentadiene.

[0010] Preferably, by weight, the main agent further includes 2.8 parts of divalent ester, 1 part of defoamer, 0.2 parts of rheology modifier, 1 part of dispersant, 7 parts of active monomer, 2 parts of fumed silica, and 2 parts of filler.

[0011] Preferably, by weight, the curing agent further includes 2 parts titanium dioxide, 2 parts active monomer, 0.06 parts dispersant, 1 part filler, and 1 part divalent ester.

[0012] Preferably, the epoxy resin has a molecular weight of 280-310, and the epoxy resin is o-cresol epoxy resin.

[0013] Preferably, by weight, the main agent comprises 27-40 parts of styrene-free copolyacrylate resin, 30-40 parts of titanium dioxide, 0.1-1.2 parts of fluorescent whitening agent, and 2-4 parts of photoinitiator; wherein the acid value of the acrylic resin composition formed by the styrene-free copolyacrylate resin and the acrylic resin with a narrow molecular weight distribution is 50-60 mgKOH / g; the curing agent comprises 6.5-8 parts of epoxy resin, 3.8-4.2 parts of triglycidyl isocyanurate, and 0.2-0.7 parts of melamine.

[0014] A method for preparing the aforementioned white high-reflectivity, yellowing-resistant ink is also provided, comprising the following steps:

[0015] S1. Preparation of the main agent: Acrylic resin, titanium dioxide, fluorescent whitening agent, photoinitiator and additives are mixed, dispersed at high speed and ground until the particle size is ≤20μm, then a diluent is added to adjust the viscosity to 200-300 dPa·s, and filtered to obtain the main agent; wherein, the high-speed dispersion speed is 600-1000 rpm and the time is 30-60 minutes, and the filter screen used for filtration is 150-300 mesh;

[0016] S2. Preparation of curing agent: Epoxy resin, curing aid, pigment and additives are mixed, dispersed at high speed and ground until the particle size is ≤20μm, then a diluent is added to adjust the viscosity to 50-150 dPa·s, and filtered to obtain the curing agent; wherein, the grinding is carried out by a three-roll mill for 2-5 times or by a sand mill, and the filter screen used for filtration has a mesh size of 150-300 mesh;

[0017] S3. Mix the main agent and the curing agent evenly in proportion to obtain the white high-reflectivity anti-yellowing ink.

[0018] Preferably, when the coating thickness formed after the ink is cured is 25μm, its reflectivity is ≥90%; after three reflow solderings at 280℃, the ΔB value is <1.

[0019] This invention provides a high-reflectivity ink with yellowing resistance. By optimizing the resin composition and pigment addition ratio, and introducing a fluorescent whitening agent, the B value can be effectively reduced, thereby solving the problem of yellowing in the visual effect of high-reflectivity ink, while ensuring and improving reflectivity. Attached Figure Description

[0020] The above and other objects, features, and advantages of the invention will become clearer through a more detailed description of the preferred embodiments illustrated in the accompanying drawings. The same reference numerals denote the same parts throughout the drawings, and the drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the gist of the invention.

[0021] Figure 1 This is a comparison diagram of the reflectance spectra of the ink in this embodiment and the comparative example. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention. All raw materials involved in the embodiments, unless otherwise specified, are commercially available; all percentages are mass percentages, and all parts are parts by weight.

[0023] One embodiment of the present invention provides a white high-reflectivity ink with anti-yellowing properties, which is composed of a main agent and a curing agent. The main agent and the curing agent are in a mass ratio of (2-4):1. By weight, the main agent contains the following components: 27-40 parts of acrylic resin, 30-40 parts of titanium dioxide, 0.1-1.2 parts of fluorescent whitening agent, and 2-4 parts of photoinitiator; wherein, the acrylic resin has an acid value of 50-60 mgKOH / g, and the acrylic resin is a styrene-free copolyacrylate resin; the curing agent contains 6.5-8 parts of epoxy resin, 3.8-4.2 parts of triglycidyl isocyanurate, and 0.2-0.7 parts of melamine.

[0024] While increasing the L value by adding more titanium dioxide, adding an appropriate amount of fluorescent whitening agent to the whole system can not only absorb ultraviolet rays below 400nm and increase the reflectivity above 420nm, but also reflect blue light, which combines with yellow light to emit white light visible to the naked eye, thus removing yellowing and whitening, thereby reducing the B value to below 1.

[0025] Optical brighteners can absorb short-wave electromagnetic waves and convert them into long-wave waves, thus reducing ultraviolet light and reflecting blue light, while also increasing reflectivity. The optical brightener is a high-temperature resistant optical brightener. In the formulation of this invention, the optimal amount of optical brightener added is 1 / 1000 to 12 / 12.

[0026] By using styrene-free copolyacrylic resin as the matrix, and through the synergistic effect of low-B-value titanium dioxide and optical brighteners, the industry challenge of simultaneously achieving high reflectivity and low yellowing has been solved. Optical brighteners, acting as optical compensation agents, replace traditional light-absorbing blue pigments, reducing the B-value without affecting reflectivity.

[0027] This application improves the transparency and gloss of the ink film by using a styrene-free copolyacrylic resin, while reducing the tendency to yellow. By optimizing the resin formulation and pigment addition ratio, and introducing a fluorescent whitening agent, the B value can be effectively lowered while ensuring high reflectivity. It should be noted that low yellowing characteristics refer to low B value and high stability. This invention optimizes pigment dispersion stability by controlling the resin acid value, reducing light scattering loss caused by pigment agglomeration and ensuring the achievement of reflectivity. This white ink is suitable for applications such as photovoltaic cell backsheets and LED bracket reflector cups, where extremely high reflectivity and color stability are required, exhibiting good stability and excellent applicability.

[0028] In a preferred embodiment, the styrene-free copolyacrylate resin is a copolymer of methyl methacrylate and butyl acrylate. It should be noted that the styrene-free copolyacrylate resin refers to a non-styrene-type acrylic resin, that is, a styrene-free (meth)acrylate copolymer resin, which is a resin copolymerized from (meth)acrylate alkyl ester monomers and optionally other vinyl monomers that can copolymerize with (meth)acrylate under the action of an initiator. The monomer composition does not contain styrene or its derivatives; for example, the styrene-free (meth)acrylate copolymer resin also does not contain styrene derivatives such as α-methylstyrene.

[0029] Preferably, the alkyl methacrylate monomer is selected from one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate. Other copolymerizable vinyl monomers are selected from one or more of (meth)acrylic acid, maleic anhydride, vinyl acetate, and acrylonitrile, but styrene monomers are also excluded.

[0030] In a preferred embodiment, the titanium dioxide is rutile titanium dioxide, and more specifically, it is low-B-value rutile titanium dioxide. It should be noted that a low B-value means a B-value less than 1.5, or a negative B-value. The fluorescent whitening agent is a compound capable of absorbing ultraviolet light below 400 nm and converting it into blue-violet light emitted at 420-480 nm.

[0031] Low-B-value titanium dioxide is selected and combined with a fluorescent whitening agent. It absorbs 420nm ultraviolet light and converts the absorbed ultraviolet energy into 420-480nm blue-violet light, achieving a visual whitening and brightening effect. The amount of fluorescent whitening agent added is controlled within the range of 0.1-1.2% to avoid quenching effects caused by excessive fluorescent whitening agent. Ultimately, the ink has a B-value ≤1.1, reflectivity ≥90%, excellent weather resistance, and good resistance to yellowing. The white high-reflectivity, yellowing-resistant ink provided by this invention, when the coating thickness formed after curing is 25μm, can simultaneously achieve high reflectivity (≥90%) and low yellowing characteristics (ΔB≤1 after high-temperature aging). This method has stable processes and is suitable for industrial production.

[0032] In a preferred embodiment, the photoinitiator is composed of 1.6-2.4 parts of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 0.8-1.2 parts of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 0.01-0.05 parts of bis2,6-difluoro-3-pyrrolephenyldipentadienyltitanium oxide.

[0033] In a preferred embodiment, the main agent further comprises, by weight, 2.8 parts of divalent ester, 1 part of defoamer, 0.2 parts of rheology modifier, 1 part of dispersant, 7 parts of active monomer, 2 parts of fumed silica, and 2 parts of filler.

[0034] In a preferred embodiment, the curing agent further comprises, by weight, 2 parts titanium dioxide, 2 parts active monomer, 0.06 parts dispersant, 1 part filler, and 1 part divalent ester.

[0035] Preferably, the active monomer is selected from one or more of the following: pentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, hexanediol diacrylate, butanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propionyl methacrylate, and propionyl methacrylate.

[0036] Preferably, the filler is selected from one or more of barium sulfate, talc, calcium carbonate, and quartz powder.

[0037] In a preferred embodiment, the epoxy resin has a molecular weight of 280-310, and the epoxy resin is o-cresol epoxy resin.

[0038] In a preferred embodiment, the main agent, by weight, comprises 15-25 parts of styrene-free copolyacrylate resin, 8-15 parts of acrylic resin with a narrow molecular weight distribution, 30-40 parts of titanium dioxide, 0.1-1.2 parts of fluorescent whitening agent, and 2-4 parts of photoinitiator; wherein the acid value of the acrylic resin composition composed of the styrene-free copolyacrylate resin and the acrylic resin with a narrow molecular weight distribution is 30-50 mgKOH / g; the curing agent comprises 6.5-8 parts of epoxy resin, 3.8-4.2 parts of triglycidyl isocyanate, and 0.2-0.7 parts of melamine.

[0039] A method for preparing the aforementioned white, high-reflectivity, yellowing-resistant white ink is also provided, comprising the following steps:

[0040] S1. Preparation of the main agent: Acrylic resin, titanium dioxide, fluorescent whitening agent, photoinitiator and other additives are mixed, dispersed at high speed and ground until the particle size is ≤20μm, then a diluent is added to adjust the viscosity to 200-300 dPa·s, and filtered to obtain the main agent; wherein, the high-speed dispersion speed is 600-1000 rpm and the time is 30-60 minutes, and the filter screen used for filtration is 150-300 mesh;

[0041] S2. Preparation of curing agent: Epoxy resin, curing aid, pigment and other additives are mixed, dispersed at high speed and ground until the particle size is ≤20μm, then a diluent is added to adjust the viscosity to 50-150 dPa·s, and filtered to obtain the curing agent; wherein, the grinding is carried out by a three-roll mill for 2-5 times or by a sand mill, and the filter screen used for filtration has a mesh size of 150-300 mesh;

[0042] S3. Mix the main agent and the curing agent evenly in proportion to obtain the white high-reflectivity anti-yellowing ink.

[0043] The above preparation method is used for the production of inks according to the formulation of this invention. The parameters are clear, the controllability is strong, and it is easy to achieve large-scale production.

[0044] In a preferred embodiment, when the coating thickness formed after the ink cures is 25 μm, its reflectivity is ≥90% and its B value is ≤1.1; after three reflow solderings at 280℃, the ΔB value is <1. The resulting ink, when forming a 25 μm thick coating, achieves a reflectivity of over 90% and a B value ≤1.1, exhibiting excellent neutral white color. Especially after undergoing the rigorous heat aging test of three reflow solderings at 280℃, its color change ΔB value is less than 1, demonstrating excellent resistance to high-temperature yellowing and superior performance.

[0045] It should be noted that reflow soldering is a specific form of high-temperature process, and LED refers to a light-emitting diode. The B value refers to the b* value in the CIE 1976 Lab color space; the LAB value is a color space model used to represent the position and color difference of a color in the color space. It consists of three components: L, a, and b. L represents the lightness or brightness of the color, with positive values ​​indicating a whitish hue and negative values ​​indicating a darker hue; a represents the red-green value, with positive values ​​indicating a reddish hue and negative values ​​indicating a greenish hue; and b represents the yellow-blue value, with positive values ​​indicating a yellowish hue and negative values ​​indicating a bluish hue.

[0046] To better illustrate the technical solution of the present invention, several preferred embodiments are now described in further detail.

[0047] The component and weight proportions of Example 1 and Comparative Example 1 are shown in Table 1 below:

[0048] Table 1. Formulations of Examples and Comparative Examples (Unit: Parts by Weight)

[0049]

[0050] In Table 1, photoinitiator 1 is diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, photoinitiator 2 is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and photoinitiator 3 is bis(2,6-difluoro-3-pyrrolidinyl)titanium oxide; among them, photoinitiator 1 is GR-TPO produced by Gurun Company, photoinitiator 2 is GR-XBPO produced by Gurun Company, and photoinitiator 3 is GR-FMT produced by Gurun Company.

[0051] The styrene-free copolyacrylate resin is produced by Guangzhou Starly Co., Ltd., GF-211-6.

[0052] Titanium dioxide R-706 is DuPont's R-706.

[0053] The fluorescent whitening agent is Tinopal OB CO from BASF.

[0054] Preparation method: Both Example 1 and Comparative Example 1 were prepared according to the following method:

[0055] Step 1: Add the main agent components to the first dispersion tank according to the proportions in Table 1, and disperse at high speed of 800 rpm for 45 minutes. Grind the dispersed slurry three times using a three-roll mill until the fineness is below 20 μm, thus obtaining the ground main agent slurry.

[0056] Simultaneously, the components of the curing agent epoxy resin were added to the second dispersion tank according to the proportions in Table 1, and dispersed at high speed at 800 rpm for 45 minutes. The dispersed slurry was then ground three times using a three-roll mill to achieve a fineness of less than 20 μm, resulting in the ground curing agent slurry.

[0057] Step 2: First, add appropriate amounts of divalent esters to the ground main agent slurry and curing agent slurry respectively, adjusting the viscosity of the main agent to 250 dPa·s and the curing agent to 100 dPa·s. Then, filter the main agent slurry and curing agent slurry separately using a 200-mesh filter cloth to obtain filtered main agent slurry and curing agent slurry respectively.

[0058] Step 3: Mix the filtered main agent slurry and curing agent slurry in Step 2 at a mass ratio of 3:1 to obtain the white ink samples of Example 1 and Comparative Example 1.

[0059] The ink sample of Comparative Example 1 was prepared using the same process as that of Example 1. See Table 1. The formulation of Comparative Example 1 does not contain the characteristic resin combination and fluorescent whitening agent of the present invention.

[0060] Example of effect

[0061] The performance of the ink products prepared in Example 1 and Comparative Example 1 will be tested and analyzed below:

[0062] 1. Reflectivity and B-value test

[0063] Test method: The white ink samples of Example 1 and Comparative Example 1 were coated onto a standard test plate, and the dry film thickness was controlled to be 25±2 μm. After UV curing, an ink dry film with a thickness of 25±2 μm was obtained. The ink dry films of Example 1 and Comparative Example 1 were subjected to the following tests:

[0064] (1) Initial reflectance: The overall reflectance of light in the wavelength range of 400-700 nm was measured using a spectrophotometer, and the measured reflectance was plotted as shown in the attached figure. Figure 1 The reflectance spectrum is shown; the specific model of the spectrophotometer used in the reflectance test is CM-26d spectrophotometer.

[0065] (2) Initial B value: The b* value (i.e. B value) of the dry ink film in the CIE Lab colorimetric system is measured using a colorimeter.

[0066] 2. Heat resistance yellowing test:

[0067] Test method: The standard sample that has undergone the above reflectivity and initial B value tests was placed in a reflow oven and subjected to three reflow soldering simulation processes at a peak temperature of 280℃. Then, the standard sample was cooled at room temperature. The peak temperature of each reflow soldering process was 280℃ and 6 minutes. After cooling to room temperature, its reflow soldering B value was measured again, and the change ΔB was calculated. The change ΔB = B value after reflow soldering - initial B value.

[0068] The test and calculation results are shown in Figure 2:

[0069] Table 2 shows the changes in B-values ​​measured after baking and reflow soldering.

[0070]

[0071] As shown in Table 2, the ink prepared in Example 1 of this invention has a reflectivity exceeding 90%, and its initial B value is ≤1.1, indicating high whiteness and no obvious yellowing. After three rigorous reflow soldering tests, the B value is close to 1, and the ΔB value is less than 1, indicating excellent resistance to high-temperature yellowing.

[0072] In contrast, Comparative Example 1, which uses a traditional formulation containing styrene resin and without added fluorescent whitening agents, has a lower reflectance, a higher initial B value, and a yellowish visual effect. After three reflow soldering tests as in Example 1, the ΔB value reached as high as 2.21, indicating severe yellowing after thermal aging. Its overall performance is significantly different from the ink prepared in Example 1 of this invention.

[0073] Depend on Figure 1It is known that by absorbing ultraviolet light below 400nm, the absorbed ultraviolet light energy is converted into blue-violet light at 420-480nm, achieving a visual whitening and brightening effect. The amount of fluorescent whitening agent added is controlled between 0.1-1.2% to avoid quenching effects caused by excessive amounts. The final solution achieves an optimal ink B value ≤1.1, reflectivity ≥90%, and excellent weather resistance and yellowing resistance.

[0074] The above experimental results fully demonstrate the effectiveness of the technical solution of this invention. The ink solution of this invention, through specific resin combinations, acid value control, and the introduction of fluorescent whitening agents, successfully achieves a perfect balance between high reflectivity and low yellowing performance in white ink. In summary, the high reflectivity ink of this invention, by selecting appropriate raw materials and proportions, achieves better yellowing resistance and high reflectivity performance in the ink coating.

[0075] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A high-reflectivity ink with anti-yellowing properties, characterized in that, Composed of a main agent and a curing agent, wherein the main agent and the curing agent are in a mass ratio of (2-4):

1. By weight, the main agent comprises the following components: 27-40 parts acrylic resin, 30-40 parts titanium dioxide, 0.1-1.2 parts fluorescent whitening agent, and 2.4-3.65 parts photoinitiator; wherein the acrylic resin has an acid value of 50-60 mgKOH / g and is a styrene-free copolyacrylate resin; the curing agent comprises 6.5-8 parts epoxy resin, 3.8-4.2 parts triglycidyl isocyanate, and 0.2-0.7 parts melamine.

2. The high reflectivity ink as described in claim 1, characterized in that, The styrene-free copolyacrylate resin is a copolymer of methyl methacrylate and butyl acrylate.

3. The high reflectivity ink as described in claim 1, characterized in that, The titanium dioxide is rutile titanium dioxide.

4. The high reflectivity ink as described in claim 1, characterized in that, The photoinitiator is composed of 1.6-2.4 parts of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 0.8-1.2 parts of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 0.01-0.05 parts of bis2,6-difluoro-3-pyrrolephenyldicenoctane.

5. The high reflectivity ink as described in claim 1, characterized in that, By weight, the main agent further includes 2.5-2.9 parts of divalent ester, 0.8-1.5 parts of defoamer, 0.1-0.4 parts of rheology modifier, 0.5-1.3 parts of dispersant, 5-8 parts of active monomer, 2-3 parts of fumed silica, and 2-5 parts of filler.

6. The high reflectivity ink as described in claim 1, characterized in that, By weight, the curing agent further includes 1.5-2.5 parts of titanium dioxide, 2-3 parts of active monomer, 0.04-0.08 parts of dispersant, 0.5-1.2 parts of filler and 0.6-1.4 parts of divalent ester.

7. The high reflectivity ink as described in claim 1, characterized in that, The epoxy resin has a molecular weight of 280-310, and the epoxy resin is o-cresol epoxy resin.

8. The high reflectivity ink as described in claim 1, characterized in that, By weight, the main agent comprises 27-40 parts of styrene-free copolyacrylate resin, 30-40 parts of titanium dioxide, 0.1-1.2 parts of fluorescent whitening agent, and 2.4-3.65 parts of photoinitiator; wherein the acid value of the styrene-free copolyacrylate resin is 50-60 mgKOH / g; the curing agent comprises 6.5-8 parts of epoxy resin, 3.8-4.2 parts of triglycidyl isocyanate, and 0.2-0.7 parts of melamine.

9. A method for preparing a white, high-reflectivity, yellowing-resistant ink as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Preparation of the main agent: Acrylic resin, titanium dioxide, fluorescent whitening agent, photoinitiator and additives are mixed, dispersed at high speed and ground until the particle size is ≤20μm, then a diluent is added to adjust the viscosity to 200-300 dPa·s, and filtered to obtain the main agent; wherein, the high-speed dispersion speed is 600-1000 rpm and the time is 30-60 minutes, and the filter screen used for filtration is 150-300 mesh; S2. Preparation of curing agent: Epoxy resin, curing aid, pigment and additives are mixed, dispersed at high speed and ground until the particle size is ≤20μm, then a diluent is added to adjust the viscosity to 50-150 dPa·s, and filtered to obtain the curing agent; wherein, the grinding is carried out by a three-roll mill for 2-5 times or by a sand mill, and the filter screen used for filtration has a mesh size of 150-300 mesh; S3. Mix the main agent and the curing agent evenly in proportion to obtain the white high-reflectivity anti-yellowing ink.

10. The method for preparing high reflectivity ink as described in claim 9, characterized in that, When the coating thickness formed after the ink is cured is 25μm, its reflectivity is ≥90%; after three reflow solderings at 280℃, the ΔB value is <1.

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