Photosensitive covering film

Abstract

The present invention discloses a photosensitive cover film, which includes a photosensitive layer and an isolation layer arranged on at least one side of the photosensitive layer; the raw materials of the photosensitive layer include base resin, curing agent, active diluent, titanium dioxide, photoinitiator, auxiliary agent, filler and solvent; the reflectivity of the photosensitive layer is greater than or equal to 95%; the dispersion degree D1 of solid particles in the photosensitive layer is greater than or equal to 1 and less than or equal to 156. In the present application, the base resin without benzene ring structure and the surface-modified titanium dioxide are matched with each other, so as to solve the problem of low whiteness of the photosensitive film in the prior art, and achieve the characteristics of high whiteness and high reflectivity of the photosensitive film; in the present application, the surface-modified titanium dioxide with better dispersibility is added, so as to solve the problem of high cost of increasing the amount of titanium dioxide added in the prior art, and achieve the reduction of the amount of titanium dioxide used while improving the whiteness and reflectivity of the photosensitive film, and effectively reduce the production cost.

Description

Technical Field

[0001] The invention relates to printed circuit technology, in particular to a photosensitive cover film. Background Art

[0002] With the development of information and communication technology, the field of microelectronics is developing rapidly, and printed circuit boards have been widely used in many fields such as mobile phones, computers, and display screens. Printed circuit boards mainly include flexible printed circuit boards, rigid printed circuit boards, and rigid-flex printed circuit boards. Traditional printed circuit boards often use solder resist ink to protect the circuit boards from dust, moisture, and chemical corrosion. However, since solder resist ink is not resistant to folding, it cannot be used in flexible boards and rigid-flex boards. In addition, the coating process of solder resist ink is complicated and often takes a lot of man-hours, which greatly increases the production cost of the product.

[0003] Photosensitive cover film came into being. As a substitute for photosensitive ink and cover film, photosensitive cover film has dual advantages. It can not only meet the printed circuit production of flexible boards, but also meet the printed circuit production of rigid boards. At the same time, it can also be applied to flexible and rigid combination boards, and has a wider range of uses.

[0004] White photosensitive cover film can replace white solder mask and cover film, greatly reducing the process flow, greatly improving production efficiency, and reducing product production costs. White photosensitive cover film, like white solder mask, mainly plays the role of solder mask and light reflection. White photosensitive cover film has good light reflection effect and can reduce light loss. It can be used in luminous products to make the product more energy-efficient.

[0005] However, the inventors of this application found that there are at least the following technical problems in the above technology during the process of implementing the technical solution of the invention in the embodiment of this application:

[0006] Currently, most white photosensitive cover films are bluish white or beige, because the resin tends to turn yellow after high temperatures, and the reflectivity is not high enough, mostly only about 93%, which is difficult to meet higher requirements. Summary of the invention

[0007] The embodiments of the present application provide a photosensitive cover film, which solves the problems of low whiteness, easy yellowing and low reflectivity of the photosensitive cover film in the prior art. The photosensitive cover film has the advantages of high reflectivity, high whiteness, no yellowing, good flexibility, high temperature resistance and good thickness uniformity, can be continuously coated, has a small proportion of titanium dioxide used and low cost, etc.

[0008] The present application embodiment provides a photosensitive cover film, including:

[0009] Photosensitive layer;

[0010] An isolation layer, disposed on at least one side of the photosensitive layer;

[0011] The raw materials of the photosensitive layer include base resin, curing agent, reactive diluent, titanium dioxide, photoinitiator, additive, filler and solvent;

[0012] The reflectivity of the photosensitive layer is greater than or equal to 95%; the thickness of the photosensitive layer is 18 to 70 μm, and the resolution is 18 to 50 μm; the dispersion degree D1 of the solid particles in the photosensitive layer is greater than or equal to 1 and less than or equal to 156;

[0013] The dispersion degree D1 is measured by the following method: the photosensitive layer in the photosensitive covering film is peeled off, and 1 g of the photosensitive layer is completely dissolved in an organic solvent. The precipitate is separated after centrifugation, and the precipitate is diluted in an organic solvent that is 10 times the weight of the precipitate to obtain a dispersion. 1 mL of the dispersion is taken onto the surface of the conductive object and observed using a scanning electron microscope. The number of solid particles measured in an area of ​​5 μm × 5 μm is the dispersion degree D1.

[0014] Furthermore, the raw material of the isolation layer includes at least one of PET or PE.

[0015] Furthermore, the photosensitive layer is made of raw materials including the following components: 100 parts by weight of base resin, 10-35 parts by weight of curing agent, 10-35 parts by weight of active diluent, 50-100 parts by weight of titanium dioxide, 1-10 parts by weight of photoinitiator, 10-30 parts by weight of filler and 3-10 parts by weight of auxiliary agent.

[0016] Furthermore, the titanium dioxide is a surface-modified rutile titanium dioxide, and the dispersion degree D2 of the surface-modified rutile titanium dioxide is greater than or equal to 1 and less than or equal to 156;

[0017] The dispersion degree D2 is measured by the following method: 1 g of titanium dioxide is completely dispersed in an organic solvent, and the precipitate is separated after centrifugation. The precipitate is diluted in an organic solvent that is 10 times the weight of the precipitate to obtain a dispersion. 1 mL of the dispersion is applied to the surface of a conductive object and observed using a scanning electron microscope. The number of solid particles measured in an area of ​​5 μm × 5 μm is the dispersion degree D2.

[0018] Furthermore, the filler includes at least one of silicon dioxide, talc, barium sulfate, calcium carbonate or zinc oxide.

[0019] Furthermore, the base resin is a resin without a benzene ring structure; preferably, the base resin includes an alkali-soluble acrylic resin.

[0020] Furthermore, the curing agent includes at least one of alicyclic epoxy resin or aliphatic epoxy resin; and the photoinitiator includes at least one of free radical photoinitiator or cationic photoinitiator.

[0021] Furthermore, the active diluent is an acrylate monomer, which includes one or more of monofunctional (meth)acrylate, difunctional (meth)acrylate, trifunctional (meth)acrylate, and multifunctional (meth)acrylate; the molecular weight of the acrylate monomer is 200-500.

[0022] Further, the solvent includes at least one of methyl nylonate or N,N-dimethylformamide.

[0023] Furthermore, the additive includes at least one of a dispersant, a leveling agent, and a defoaming agent; wherein the dispersant includes at least one of BYK110 or BKY111, the leveling agent includes at least one of BYK333 or BYK358, and the defoaming agent includes at least one of BKY141 or BKY066N.

[0024] Therefore, the technical solution in this application has at least the following beneficial effects:

[0025] (1) The present application solves the problem of the yellowing of the photosensitive film in the prior art by adding a base resin that does not contain a benzene ring structure, so that the photosensitive film has high whiteness and is not prone to yellowing;

[0026] (2) In the present application, the base resin without a benzene ring structure and the surface-modified titanium dioxide are combined to solve the problem of low whiteness of the photosensitive film in the prior art, thereby achieving the characteristics of high whiteness and high reflectivity of the photosensitive film;

[0027] (3) In the present application, by adding surface-modified titanium dioxide with better dispersibility, the problem of high cost due to increased amount of titanium dioxide added in the prior art is solved, and the amount of titanium dioxide used is reduced while improving the whiteness and reflectivity of the photosensitive film, thereby effectively reducing production costs. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the specific implementation modes of the present application will be clearly and completely described below in combination with the implementation modes of the present invention.

[0029] The present application provides a photosensitive covering film, which solves the problem of low reflectivity of the photosensitive film in the prior art by improving the dispersion uniformity and dispersion degree of solid particles in the photosensitive covering film. The photosensitive film in the embodiment of the present application is evenly coated with few surface defects and has better whiteness and higher reflectivity.

[0030] One aspect of the present application provides a photosensitive cover film, comprising: a photosensitive layer; an isolation layer, arranged on at least one side of the photosensitive layer; the raw materials of the photosensitive layer include a base resin, a curing agent, an active diluent, titanium dioxide, a photoinitiator, an additive, a filler and a solvent; the reflectivity of the photosensitive layer is greater than or equal to 95%; the thickness of the photosensitive layer is 18 to 70 μm, and the resolution is 18 to 40 μm; the dispersion D1 of solid particles in the photosensitive layer is greater than or equal to 1 and less than or equal to 156; the dispersion D1 is measured by the following method: the photosensitive layer of the photosensitive cover film is peeled off, and 1 g of the photosensitive layer is completely dissolved in an organic solvent, centrifuged at a speed of 8000 rpm for 4 minutes, and then the precipitate is separated, the precipitate is diluted in an organic solvent 10 times the weight of the precipitate to obtain a dispersion, 1 mL of the dispersion is taken to the surface of the conductive object, and observed with a scanning electron microscope. The number of solid particles measured in an area of ​​5 μm×5 μm is the dispersion D1.

[0031] In order to obtain a photosensitive layer composition with higher whiteness, it is necessary to comprehensively consider the properties of the photosensitive layer composition such as absorption, refraction, reflection, scattering and diffraction of light. The absorption of light by the photosensitive layer is mainly determined by the thickness of the photosensitive layer. If the photosensitive layer is too thick, the absorption of light will be too large, which will reduce the reflectivity of the photosensitive layer. At the same time, if the photosensitive layer is too thin, light can easily pass through the photosensitive layer, which will also cause the reflectivity of the photosensitive layer to decrease. When using the photosensitive cover film, the photosensitive layer needs to be attached to the circuit board. After exposure, the photosensitive layer is partially cured by light and combined with the circuit board. Therefore, the photosensitive cover film requires a certain resolution to ensure accuracy. In order to ensure that the photosensitive cover film is not contaminated during transportation, storage and use, an isolation layer needs to be set on at least one side of the photosensitive layer. The isolation layer can be set on both sides of the photosensitive layer to isolate the photosensitive layer, or it can be set only on one side of the photosensitive layer. After production, the photosensitive layer of the photosensitive cover film is rolled inward and stored in a roll shape.

[0032] The solid particles in the photosensitive layer include titanium dioxide, fillers and particulate matter insoluble in organic solvents in the photosensitive layer composition. The uniformity of the distribution of solid particles in the photosensitive layer, or the dispersion of solid particles, has an important influence on the whiteness and reflectivity of the photosensitive layer. Improving the dispersion of solid particles can not only improve the whiteness and reflectivity of the photosensitive layer, but also reduce the amount of fillers added to the photosensitive layer, especially the amount of titanium dioxide added, thereby reducing production costs. The type and amount of titanium dioxide and the type and amount of fillers will affect the dispersion of solid particles in the photosensitive layer. Therefore, selecting suitable titanium dioxide and fillers, and controlling the amount of titanium dioxide and fillers can effectively optimize the dispersion of solid particles and improve the whiteness and reflectivity of the photosensitive layer.

[0033] As an implementation manner, the raw material of the isolation layer includes at least one of PET or PE.

[0034] The main function of the isolation layer in the photosensitive cover film is to prevent the photosensitive layer from being contaminated and affecting its use effect. Therefore, the isolation layer needs to have stable chemical properties, no reaction with the photosensitive layer, good flexibility and low cost. In addition, the isolation layer can also protect and support the photosensitive layer. There are many options for the raw materials of the isolation layer. PET and PE can be used to make the isolation layer, and the cost is low. Using them to make the isolation layer can reduce the production cost of the product. Among them, PET is non-toxic, has high impact strength, good folding resistance and stable chemical properties. It has excellent gas, water, oil and odor barrier properties and can protect the photosensitive layer well.

[0035] As an implementation method, the photosensitive layer is made of raw materials including the following components: 100 parts by weight of a base resin, 10-35 parts by weight of a curing agent, 10-35 parts by weight of an active diluent, 50-100 parts by weight of titanium dioxide, 1-10 parts by weight of a photoinitiator, 10-30 parts by weight of a filler and 3-10 parts by weight of an auxiliary agent.

[0036] As an implementation method, the titanium dioxide is surface-modified rutile titanium dioxide, and the dispersion degree D2 of the surface-modified rutile titanium dioxide is greater than or equal to 1 and less than or equal to 156.

[0037] The dispersion degree D2 is measured by the following method: 1 g of titanium dioxide is completely dispersed in an organic solvent, and the precipitate is separated after centrifugation at 8000 rpm for 4 minutes. The precipitate is diluted in an organic solvent that is 10 times the weight of the precipitate to obtain a dispersion. 1 mL of the dispersion is taken onto the surface of a conductive object and observed using a scanning electron microscope. The number of solid particles measured in an area of ​​5 μm × 5 μm is the dispersion degree D2.

[0038] Titanium dioxide is an important inorganic chemical pigment, the main component of which is titanium dioxide. Among the commonly used white pigments, titanium dioxide has the lowest relative density, the largest surface area and the highest pigment volume among white pigments of the same mass. Titanium dioxide has high whiteness, strong hiding power, stable chemical properties and has the same degree of strong reflection of all wavelengths of visible light. It is considered to be the best white pigment in the world. Commonly used titanium dioxide is divided into two types: anatase titanium dioxide and rutile titanium dioxide. Anatase is the low-temperature phase of titanium dioxide, which generally transforms into rutile at 500℃~600℃, but has a more obvious catalytic effect than rutile titanium dioxide, which can easily age the photosensitive layer composition. Rutile is the most stable crystal form, with a high melting point, dense atomic arrangement, high density, hardness and dielectric constant, large refraction and scattering of light, and is very suitable as a reflective filler for the photosensitive layer composition. The uniformity of titanium dioxide distribution, or the dispersion of titanium dioxide, has an important influence on the whiteness and reflectivity of the photosensitive layer. The titanium dioxide is more evenly distributed and less likely to agglomerate, so less titanium dioxide can be added to achieve the same whiteness and reflectivity requirements. In this implementation, by adding titanium dioxide with a higher degree of dispersion, agglomeration between titanium dioxide is avoided, thereby avoiding the problem of reduced light scattering ability of individual particles due to particle agglomeration affecting the overall reflectivity of the photosensitive film.

[0039] As an implementation method, the titanium dioxide is selected from at least one of Chuntai TS-6300 titanium dioxide and Chuntai TS-6200 titanium dioxide.

[0040] Chuntai TS-6300 titanium dioxide has a Fluffy structure on the surface, good dispersion, and a certain distance between particles. In a high filling state, it can also avoid the particles from agglomerating together, which can significantly improve the reflectivity. The dispersion D2 of Chuntai TS-6300 titanium dioxide is in the range of 1 to 156, which can meet the addition requirements in this implementation. The use of titanium dioxide with better dispersion can effectively improve the dispersion of solid particles in the photosensitive layer, so that the photosensitive layer has higher whiteness and reflectivity.

[0041] As an implementation, the filler includes at least one of silicon dioxide, talc, barium sulfate, calcium carbonate or zinc oxide.

[0042] In order to increase the whitening effect of titanium dioxide and reduce the production cost of the product, a certain amount of silicon dioxide, barium sulfate or talcum powder is added to the photosensitive composition. At the same time, the filler can also increase the dimensional stability, rigidity and heat resistance of the photosensitive layer composition, improve the dispersibility of titanium dioxide, and obtain a higher reflectivity. Among them, talcum powder is in the form of flakes, has higher rigidity, dimensional stability and heat resistance, and has a good reinforcing effect on the photosensitive layer composition. Barium sulfate can provide the photosensitive layer composition with scratch resistance, high gloss and high hardness surface, and its properties are more stable.

[0043] As an implementation method, the base resin is a resin without a benzene ring structure. Further, the base resin includes an alkali-soluble acrylic resin. Further, the alkali-soluble acrylic resin includes at least one of a carboxylic acid-modified bisphenol A epoxy resin, a carboxylic acid-modified bisphenol F epoxy resin, or a carboxylic acid-modified phenolic epoxy resin. Specifically, the base resin can select bisphenol-type alkali-soluble acrylate FST-3-1 (Shanghai Showa Chemical).

[0044] In the prior art, the main reason for the yellowing of the photosensitive layer is that the base resin contains a benzene ring structure. When the photosensitive layer is heated, it is easy to turn yellow. In this implementation, the base resin uses an alkali-soluble acrylic resin without a benzene ring structure, so that the photosensitive layer composition does not turn yellow. It can effectively improve the whiteness and reflectivity when combined with the surface-modified titanium dioxide. At the same time, the alkali-soluble acrylic resin is copolymerized by three high-temperature resistant monomers and contains a high-hindered six-membered ring, which makes the alkali-soluble acrylic resin have excellent high-temperature resistance.

[0045] As an implementation, the curing agent includes at least one of bisphenol epoxy resin, biphenyl epoxy resin, novolac epoxy resin, epoxy resin containing naphthalene ring, alicyclic epoxy resin or aliphatic epoxy resin. Further, the curing agent can be selected from bisphenol epoxy resin. Further, the bisphenol epoxy resin can be selected from at least one of Nan Ya 128E, Nan Ya 501H or Nan Ya 901.

[0046] Epoxy resin has excellent physical and mechanical properties, heat resistance, chemical resistance and electrical insulation properties, and can greatly improve the electrical properties and various resistances of the photosensitive layer composition, which is beneficial to the application of the photosensitive layer composition in the field of printed circuits. In order for the photosensitive layer composition to achieve good performance, the addition of epoxy resin is necessary. When the amount of epoxy resin added is insufficient, it is difficult for the photosensitive layer composition to have good heat resistance, chemical resistance and electrical insulation properties. However, if the amount of epoxy resin added is too high, the toughness of the photosensitive layer composition will decrease after curing. Therefore, the amount of epoxy resin added must be controlled within a certain range.

[0047] As an implementation method, the active diluent is an acrylate monomer, including one or more of monofunctional (meth)acrylate, difunctional (meth)acrylate, trifunctional (meth)acrylate, and multifunctional (meth)acrylate. The molecular weight of the acrylate monomer is 200-500.

[0048] The excellent comprehensive performance of acrylate monomers is conducive to improving the film-forming property of the composition and the high temperature resistance after film formation. When the content of acrylate monomers is low, the chemical resistance is insufficient. When the content of acrylate monomers is too much, although the chemical resistance is improved, the toughness is reduced and the flexibility is insufficient. During curing, the epoxy resin, acrylate monomers and alkali-soluble acrylic resin are cross-linked with each other to form the main body of the photosensitive layer composition. The prepared photosensitive layer composition does not yellow, has good flexibility and excellent heat resistance.

[0049] It should be noted that the above-mentioned "multi-functional group" refers to the number of functional groups being greater than 3. The above-mentioned acrylate monomers have excellent comprehensive performance and are more suitable for use in photosensitive cover film compositions. Furthermore, the monofunctional (meth)acrylate includes at least one of (ethoxy)phenol (meth)acrylate, stearic acid acrylate, ethoxy (propoxy) nonylphenol (meth)acrylate or ethoxy (propoxy) tetrahydrofurfuryl (meth)acrylate, and the difunctional (meth)acrylate includes 1,6-hexanediol diacrylate, tricyclohexane dimethanol diacrylate, dioxanediol diacrylate, ethoxylated (propoxylated) bisphenol A di(meth)acrylate, polyethylene glycol. The present invention relates to a monomer comprising at least one of polyol (400) diacrylate or polypropylene glycol (600) diacrylate, the trifunctional (meth) acrylate comprises at least one of ethoxy (propoxy) trimethylolpropane tri(meth) acrylate, pentaerythritol triacrylate or tris (2-hydroxyethyl) isocyanuric acid triacrylate, and the multifunctional (meth) acrylate comprises at least one of pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ethoxylated pentaerythritol tetraacrylate or dipentaerythritol hexaacrylate. Furthermore, the acrylate monomer is pentaerythritol tetraacrylate or triethoxypropane triacrylate.

[0050] The photoinitiator includes at least one of a free radical photoinitiator or a cationic photoinitiator. Further, the free radical photoinitiator includes at least one of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-[4-(2-hydroxy)-phenyl]-3-hydroxy-2-methyl-1-propanone-1-one, 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide, 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, 2-methyl-1-(4-methylthiophenyl)-2-morphinyl-1-propanone or 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone; the cationic initiator includes at least one of a diazonium salt, a diaryliodonium salt, a triarylsulfonium salt, an alkylsulfonium salt, an iron arene salt, a sulfonyloxy ketone or a triarylsiloxane. Furthermore, the free radical photoinitiator is the photoinitiator TPO (ethyl 2,4,6-trimethylbenzoylphenylphosphonate), and the cationic initiator is Irgacure 250 (2-hydroxy-2-methyl-1-phenyl-1-propanone, BASF).

[0051] An increase in the content of photoinitiators can easily cause yellowing. Insufficient content of photoinitiators will lead to incomplete curing of the photosensitive layer composition, and the prepared photosensitive layer will have insufficient chemical resistance, heat resistance, and solder resistance, etc., resulting in a decrease in the practical performance of the photosensitive cover film. Adding rutile titanium dioxide to the photosensitive layer composition can significantly improve the reflectivity of the photosensitive layer composition. In the embodiment of the present application, a small amount of titanium dioxide can achieve a higher reflectivity, and in order to improve the reflectivity while avoiding the problems of insufficient curing and yellowing resistance caused by it, it is necessary to select some suitable photoinitiators, so that the photosensitive layer composition provided in the embodiment of the present application has more outstanding comprehensive performance. Photoinitiators are a class of compounds that can absorb energy of a certain wavelength in the ultraviolet light region or the visible light region, produce free radicals, cations, etc., thereby initiating monomer polymerization and cross-linking curing. In the embodiment of the present application, the photosensitive layer composition needs to be illuminated for curing when used, and it is necessary to select an appropriate active photoinitiator according to the type of prepolymer or monomer. Acrylate monomers are free radical active diluents, so free radical photoinitiators should be selected during curing. At the same time, in order to ensure product performance and reduce costs, the selection of photoinitiators needs to meet the requirements of non-toxicity, pollution-free, low cost, low solubility and high reaction activity.

[0052] As an implementation, the solvent includes at least one of methyl nylonate or N,N-dimethylformamide (DMF).

[0053] In order to better disperse the components such as the matrix resin and titanium dioxide, it is necessary to select a suitable solvent to disperse the components. The components of the photosensitive layer composition include organic and inorganic substances. The selected solvent needs to have high solubility to dissolve and disperse the components, and non-polymerization ensures that the components are evenly mixed, the properties of the photosensitive layer composition are uniform and stable, and the prepared photosensitive cover film has excellent uniformity. At the same time, the high solubility of the solvent is also conducive to improving the dispersibility of titanium dioxide, so that the photosensitive cover film can achieve a higher reflectivity. And because the photosensitive cover film needs to play a solder mask and reflective role when used, the solvent also needs to have good stability to ensure that the photosensitive cover film will not decompose or volatilize at high temperature during solder mask to produce performance degradation. Therefore, the solvent selection needs to meet the requirements of high solubility, non-polymerization, stable chemical properties, high temperature resistance and low toxicity. Nylon acid methyl ester and N, N-dimethylformamide are both good solvents that meet the use requirements of the solvent in the present invention. Among them, methyl nylonate has low toxicity, is safe to use, has high solubility, high boiling point and high stability, and can promote the improvement of the flexibility and adhesion of the photosensitive layer composition, improve the gloss of the photosensitive layer composition, has good leveling performance, and can also improve the hiding power of titanium dioxide. N,N-dimethylformamide has good solubility for a variety of organic and inorganic compounds, good chemical stability, low toxicity and no polymerization.

[0054] As an implementation manner, the auxiliary agent includes at least one of dispersant BYK110, dispersant BKY111, leveling agent BYK333, leveling agent BYK358, defoamer BKY141 or defoamer BKY066N.

[0055] Additives refer to those ingredients added in small amounts to the formulation of the photosensitive layer composition, which can control or enhance the performance of the coating. Although the amount added is small, it has a great impact on the performance of the photosensitive layer composition. Adding a dispersant to the photosensitive layer composition can effectively improve the dispersibility of the reflective filler, improve the whiteness and film-forming properties of the photosensitive layer composition. Adding a leveling agent to the photosensitive layer composition can make the photosensitive layer composition form a flat, smooth and uniformly thick photosensitive layer, thereby improving the use effect of the photosensitive layer composition. Defoaming agents can effectively reduce the generation of foam during the preparation of the photosensitive layer composition, eliminate the adverse effects of foam, and improve the quality of the photosensitive layer composition.

[0056] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific embodiments.

[0057] Example:

[0058] The components used in Examples 1-10 and the contents of the corresponding components are shown in Table 1 below.

[0059] The components used in Examples 11-20 and the contents of the corresponding components are shown in Table 2 below.

[0060] Comparative Example:

[0061] The components used in Comparative Examples 1-10 and the contents of the corresponding components are shown in Table 3 below.

[0062] Table 1 Components of Examples 1-10 in parts by weight

[0063]

[0064]

[0065] Table 2 Components of Examples 11-20 in parts by weight

[0066]

[0067] Table 3 Comparative Examples 1-10 Components by weight

[0068]

[0069] Note: In Tables 1 to 3 above, A is bisphenol type alkali-soluble acrylic resin FST-3-1 (Shanghai Showa Chemical), B1 is aliphatic epoxy resin ERL-4221, B2 is 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexyl methyl ester, C1 is pentaerythritol tetraacrylate (Zhi De Chemical), C2 is triethoxypropane triacrylate, E1 is photoinitiator TPO, E2 is photoinitiator Irgacure 250, F1 is leveling agent BYK333, F2 is leveling agent BYK358, F3 is dispersant BYK110, F4 is dispersant BKY111, F5 is defoamer BKY141, and F6 is defoamer BKY066N.

[0070] Photosensitive cover film preparation:

[0071] The photosensitive layer was prepared according to the following method using the components and contents of the photosensitive layer described in Tables 1, 2 and 3 above; at the same time, a 25 μm thick PET support film was set on one side of the photosensitive layer, and a 25 μm thick PE protective film was set on the other side of the photosensitive layer.

[0072] Alkali-soluble acrylic resin, epoxy resin, acrylate monomer, photoinitiator, titanium dioxide, filler, additive and solvent are mixed and stirred to obtain a mixture;

[0073] The mixed material is sequentially subjected to coating, laminating, exposure, development and curing treatments to obtain a photosensitive cover film.

[0074] The coating method is the wire rod method; the film pasting method is vacuum pasting; during the exposure process, the energy is 100-300mJ.cm -2; During the development process, the developer is a 1.0-1.5wt% Na2CO3 solution, the development time is 60-90s, the development temperature is 28-30°C, and the spray pressure is 0.2-0.4Mpa; during the curing process, the treatment temperature is 150-200°C, and the treatment time is 1-1.5h.

[0075] Performance Testing and Results

[0076] Performance Test:

[0077] 1. Test of the dispersion of solid particles in the photosensitive film: peel off the photosensitive layer in the photosensitive film, take 1g of the photosensitive layer and completely dissolve it in an organic solvent, centrifuge it at 8000rpm for 4 minutes to separate the precipitate, dilute the precipitate in an organic solvent 10 times the weight of the precipitate to prepare a dispersion, take 1mL of the dispersion on the surface of the conductive object, observe it with a scanning electron microscope, and the number of the solid particles measured in an area of ​​5μm×5μm is the dispersion D1;

[0078] Titanium dioxide dispersion test: Take 1g of titanium dioxide and completely disperse it in an organic solvent. Centrifuge it at 8000rpm for 4 minutes to separate the precipitate. Dilute the precipitate in an organic solvent that is 10 times the weight of the precipitate to prepare a dispersion. Take 1mL of the dispersion on the surface of a conductive object and observe it with a scanning electron microscope. The number of solid particles measured in an area of ​​5μm×5μm is the dispersion D2.

[0079] 2. Whiteness test: The yellowing instrument test L value is greater than 94, b<2.

[0080] 3. Reflectivity test: The reflectivity of the sample is tested using a spectrophotometer with a wavelength range of 460nm.

[0081] 4. Solder resistance test

[0082] Refer to IPC-TM650.2.6.8. Immerse the cured film vertically in a 300°C tin furnace for 30 seconds and observe whether the surface has blistering, discoloration, floating, peeling, etc. The changes in appearance are evaluated according to the following criteria.

[0083] ◎: No change in appearance

[0084] ○: The surface of the cured film is discolored

[0085] ×: Cured film is floating, thinning, and solder penetration

[0086] 5. Cured film bending resistance test

[0087] With reference to JIS-C-5-016 standard 8.7, evaluation was performed based on the following criteria.

[0088] ◎: There are no cracks on the cured film.

[0089] ○: The cured film has some cracks.

[0090] ×: There are cracks on the cured film

[0091] 6. Chemical gold resistance test: Soak in 90 degrees Celsius chemical gold solution for 30 minutes and evaluate based on the following criteria.

[0092] ◎: No shedding;

[0093] ○: Slight shedding;

[0094] ×: Extensive shedding.

[0095] Performance test results:

[0096] The performance test results of the photosensitive cover films in Examples 1-20 and Comparative Examples 1-10 are shown in Table 4 below.

[0097] Table 4 Performance test results of the photosensitive cover films in Examples 1-20 and Comparative Examples 1-10

[0098]

[0099]

[0100] The following conclusions can be drawn from the comparison of the compositions of the photosensitive layers of the embodiments and comparative examples in Tables 1-3 and the performance test results of the photosensitive films of the embodiments and comparative examples in Table 4:

[0101] 1. Although increasing the amount of curing agent added can make the curing effect better and the curing more thorough, when the curing agent is excessive, the toughness of the cured photosensitive film decreases and the bending resistance decreases; as in Example 3, compared with Example 1, the curing agent is excessive, and its bending resistance decreases slightly. When the amount of curing agent added is insufficient, the soldering resistance and the gold resistance of the photosensitive film will decrease; as in Example 2, compared with Example 1, the amount of curing agent added is insufficient, and its soldering resistance and the gold resistance are reduced to varying degrees.

[0102] 2. Reactive diluents can improve the chemical resistance of the photosensitive film, but excessive addition of reactive diluents will also cause the photosensitive film's bending resistance to decrease; as in Example 5, compared with Example 1, the excessive addition of reactive diluents causes the resulting photosensitive film to have slightly inferior bending resistance than the photosensitive film in Example 1.

[0103] 3. The photoinitiator and curing agent work together to achieve the purpose of curing. Too little photoinitiator will affect the curing effect and reduce the heat resistance and solder resistance of the photosensitive film; while too much photoinitiator will cause adverse effects such as yellowing of the photosensitive film, affecting the appearance quality of the photosensitive film.

[0104] 4. The dispersion D2 of titanium dioxide added to the photosensitive film will directly affect the dispersion D1 of solid particles in the photosensitive film. After being mixed with other components and processed through a series of preparation processes, the dispersion D1 of solid particles in the photosensitive film is greater than or equal to the dispersion D2 of titanium dioxide added to the photosensitive film, and the dispersion D1 of solid particles in the photosensitive film directly affects the reflectivity and other properties of the photosensitive film. When the dispersion D1 of solid particles in the photosensitive film is in the range of 1-156, it can satisfy the requirement of making the photosensitive film have better reflectivity under the premise of adding as little titanium dioxide as possible; that is, when adding the same amount of titanium dioxide, the photosensitive film with D1 in the range of 1-156 has better reflectivity than the photosensitive film with D1 greater than 156. When D1 exceeds 156, it means that the dispersion of solid particles in the photosensitive film is poor, and agglomeration occurs between particles, which in turn affects the reflectivity of the photosensitive film. Insufficient addition of titanium dioxide will result in insufficient reflectivity of the photosensitive film. Increasing the content of titanium dioxide can increase the reflectivity of the photosensitive film, but increasing the content of titanium dioxide will inevitably significantly increase the production cost. Adding fillers can reduce production costs, but excessive addition of fillers will affect both reflectivity and chemical resistance, reducing reflectivity and chemical resistance. At the same time, the larger the particle size of the filler, the lower the dispersibility of the solid particles and the lower the reflectivity.

[0105] The present application adds titanium dioxide with better dispersion to improve the overall dispersion of solid particles in the photosensitive film. On the premise of improving the performance of the photosensitive film such as reflectivity, the addition amount of titanium dioxide is reduced to reduce production costs.

[0106] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A photosensitive cover film, characterized in that: include: Photosensitive layer; An isolation layer, disposed on at least one side of the photosensitive layer; The raw materials of the photosensitive layer include base resin, curing agent, active diluent, titanium dioxide, photoinitiator, auxiliary agent, filler and solvent; the titanium dioxide is surface-modified rutile titanium dioxide, and the base resin is a resin without a benzene ring structure; The reflectivity of the photosensitive layer is greater than or equal to 95%; The thickness of the photosensitive layer is 18 to 70 μm, and the resolution is 18 to 50 μm; The dispersion degree D1 of the solid particles in the photosensitive layer is greater than or equal to 1 and less than or equal to 156; The dispersion degree D1 is measured by the following method: peeling off the photosensitive layer in the photosensitive covering film, taking 1g of the photosensitive layer and completely dissolving it in an organic solvent, separating the precipitate after centrifugation, diluting the precipitate in an organic solvent that is 10 times the weight of the precipitate to obtain a dispersion, taking 1mL of the dispersion onto the surface of the conductive object, observing with a scanning electron microscope, and the number of the solid particles measured in an area of ​​5μm×5μm is the dispersion degree D1.

2. A photosensitive cover film according to claim 1, characterized in that: The material of the isolation layer includes at least one of PET and PE.

3. A photosensitive cover film according to claim 1, characterized in that: The photosensitive layer is made of raw materials including the following components: 100 parts by weight of base resin, 10-35 parts by weight of curing agent, 10-35 parts by weight of active diluent, 50-100 parts by weight of titanium dioxide, 1-10 parts by weight of photoinitiator, 10-30 parts by weight of filler and 3-10 parts by weight of auxiliary agent.

4. A photosensitive cover film according to claim 1, characterized in that: The dispersion degree D2 of the surface modified rutile titanium dioxide is greater than or equal to 1 and less than or equal to 156; The dispersion degree D2 is measured by the following method: 1 g of titanium dioxide is completely dispersed in an organic solvent, the precipitate is separated after centrifugation, the precipitate is diluted in an organic solvent 10 times the weight of the precipitate to prepare a dispersion, 1 mL of the dispersion is taken to the surface of a conductive object, and observed with a scanning electron microscope. The number of solid particles measured in an area of ​​5 μm×5 μm is the dispersion degree D2.

5. The photosensitive cover film according to claim 1, characterized in that: The filler includes at least one of silicon dioxide, talc, barium sulfate, calcium carbonate or zinc oxide.

6. A photosensitive cover film according to claim 1, characterized in that: The base resin includes an alkali-soluble acrylic resin.

7. The photosensitive cover film according to claim 1, characterized in that: The curing agent includes at least one of a cycloaliphatic epoxy resin or an aliphatic epoxy resin; The photoinitiator includes at least one of a free radical photoinitiator or a cationic photoinitiator.

8. The photosensitive cover film according to claim 1, characterized in that: The reactive diluent is an acrylate monomer, and the acrylate monomer includes one or more of monofunctional (meth)acrylate, difunctional (meth)acrylate, trifunctional (meth)acrylate, and multifunctional (meth)acrylate; The molecular weight of the acrylic acid ester monomer is 200-500.

9. The photosensitive cover film according to claim 1, characterized in that: The solvent includes at least one of methyl nylonate or N,N-dimethylformamide.

10. The photosensitive cover film according to claim 1, characterized in that: The auxiliary agent includes at least one of a dispersant, a leveling agent, and a defoaming agent; wherein the dispersant includes at least one of BYK110 or BKY111, the leveling agent includes at least one of BYK333 or BYK358, and the defoaming agent includes at least one of BKY141 or BKY066N.

Images