WO2023216715A1 - Circuit board comprising ultra-black composite coating, display device and preparation method - Google Patents

Abstract

The present application provides a preparation method for a circuit board comprising an ultra-black composite coating. The preparation method comprises the following steps: providing a circuit board, the circuit board comprising a pad; forming a photosensitive resin layer on the circuit board; exposing the photosensitive resin layer; forming an ultra-black coating on the exposed photosensitive resin layer; forming a transparent photosensitive resin layer on the ultra-black coating; and exposing the transparent photosensitive resin layer, and developing the exposed transparent photosensitive resin layer and the exposed photosensitive resin to expose the pad to obtain the ultra-black composite coating. The ultra-black composite coating prepared in the present application has the characteristics of relatively high adhesion, relatively large insulation impedance and relatively consistent light reflectivity. The present application further provides an ultra-black composite coating prepared by the preparation method.

Description

Circuit board, display device and preparation method containing ultra-black composite coating

This application claims priority to the Chinese patent application submitted to the China Patent Office on May 13, 2022, with the application number 2022105202907 and the invention name "Ultra-black composite coating and preparation method thereof", the entire content of which is incorporated herein by reference. Applying.

Technical field

The present application relates to the technical field of display devices, and in particular to a circuit board containing an ultra-black composite coating, a display device and a preparation method.

Background technique

Display devices such as LED displays are a mainstream display product in the display industry. They have the characteristics of higher brightness, wider viewing angles and longer life. They are widely used in indoor and outdoor advertising, sports, conference displays and security command. Wait for the scene. High contrast has always been an important indicator pursued by LED displays. High contrast can make the picture display more delicate and layered, providing the ultimate viewing experience.

Currently, one way to improve the contrast of the display is to use ultra-black materials to reduce the darkness of the display when the screen is turned off. However, ultra-black materials have higher requirements for surface treatment of the PCB board substrate, poor adhesion on the PCB board substrate, and the insulation resistance of ultra-black materials is small. In addition, since it is necessary to form a micropore structure on the surface of ultra-black materials to increase the absorption of light, the micropore structure formed on the surface is relatively low-strength and is easy to fall off or produce marks when touched or lightly scratched, affecting Reflectivity consistency.

Contents of the invention

Based on this, it is necessary to provide a method for preparing circuit boards containing ultra-black composite coatings with higher adhesion, larger insulation resistance, and more consistent light reflectivity.

In addition, it is also necessary to provide a circuit board containing an ultra-black composite coating prepared by the above preparation method.

In addition, it is also necessary to provide a display device including the circuit board containing the ultra-black composite coating.

At least one embodiment of the present application provides a method for preparing a circuit board containing an ultra-black composite coating, including the following steps:

providing a circuit board, the circuit board including solder pads;

Form a photosensitive resin layer on the circuit board;

Exposing the photosensitive resin layer;

Form an ultra-black material layer on the exposed photosensitive resin layer;

forming a transparent photosensitive resin layer on the ultra-black material layer; and

Exposing the transparent photosensitive resin layer, and developing the exposed transparent photosensitive resin layer and the exposed photosensitive resin layer to expose the bonding pad to obtain an ultra-black composite coating, thereby obtaining a composite coating containing ultra-black layer of circuit board.

In one embodiment, the preparation materials of the ultra-black material layer include light-absorbing pigments, film-forming substances, additives, and dispersion media.

In one embodiment, the light-absorbing pigment includes pigment carbon black, the light-absorbing pigment further includes at least one of carbon microporous spheres, carbon nanotubes, and graphene, and the surface of the ultra-black material layer has a micropore structure. .

In one embodiment, the particle size of the pigment carbon black is 50-100 nm, and/or the particle size of the carbon microporous spheres is 2-15 μm, and/or the carbon microporous spheres include micropores, and /or the pore diameter of the micropore is 0.5-5 μm, and/or the length of the carbon nanotube is 65-85 nm, and/or the diameter of the carbon nanotube is 11-15 nm, and/or the graphene The sheet diameter size is 5~50μm.

In one embodiment, the thickness of the photosensitive resin layer is 10-30 μm, and/or the thickness of the ultra-black material layer is 5-15 μm, and/or the thickness of the transparent photosensitive resin layer is 5-15 μm.

In one embodiment, forming the photosensitive resin layer on the circuit board specifically includes the following steps:

Cover the circuit board with photosensitive resin by spraying or printing; and

heating the photosensitive resin to form the photosensitive resin layer;

Wherein, the temperature for heating the photosensitive resin is 65°C to 80°C, and the time for heating the photosensitive resin is 25 to 40 minutes.

In one embodiment, forming the ultra-black material layer on the exposed photosensitive resin layer specifically includes the following steps:

Cover the ultra-black material on the exposed photosensitive resin layer by spraying or printing; and

heating the ultra-black material to form the ultra-black material layer;

Wherein, the temperature for heating the ultra-black material is 60°C to 80°C, and the time for heating the ultra-black material is 3 to 5 minutes.

In one embodiment, forming the transparent photosensitive resin layer on the ultra-black material layer specifically includes the following steps:

The transparent photosensitive resin is formed on the ultra-black material layer by spraying or printing; and

heating the transparent photosensitive resin to form the transparent photosensitive resin layer;

Wherein, the temperature for heating the transparent photosensitive resin is 65°C to 80°C, and the time for heating the transparent photosensitive resin is 25 to 40 minutes.

At least one embodiment of the present application provides a circuit board containing an ultra-black composite coating. The circuit board containing an ultra-black composite coating is prepared by the above preparation method.

At least one embodiment of the present application provides a display device, which includes the circuit board containing the ultra-black composite coating.

The ultra-black composite coating in the circuit board containing the ultra-black composite coating provided by this application includes a bottom layer of photosensitive resin layer, an intermediate layer of ultra-black material layer, and a top layer of transparent photosensitive resin layer. The bottom layer of photosensitive resin layer gives the The ultra-black composite coating has sufficient support strength, adhesion and insulation resistance, which avoids the problems of insufficient support strength and adhesion and too small insulation resistance of simple ultra-black material directly coated on the circuit board; the transparent photosensitive resin The top layer of the layer provides effective protection for the micropore structure on the surface of the ultra-black material layer, preventing the fragile surface structure of the ultra-black material layer from being damaged and causing inconsistent light reflectivity on the surface.

Description of the drawings

In order to explain the technical solution of the present application more clearly, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of a circuit board containing an ultra-black composite coating provided by this application;

Figure 2 is a 3D microscope image of the surface of the ultra-black material layer provided in Example 1 of the present application;

Figure 3 is a 3D microscope image of the surface of the ultra-black material layer provided in Example 2 of the present application;

Figure 4 is a 3D microscope image of the surface of the ultra-black material layer provided in Example 3 of the present application;

Figure 5 is an apparent blackness diagram of the ultra-black material layer provided in Example 1 of the present application under a 200x microscope dark field mode;

Figure 6 is an apparent blackness diagram of the ultra-black material layer provided in Example 2 of the present application under a 200x microscope dark field mode;

Figure 7 is an apparent blackness diagram of the ultra-black material layer provided in Example 3 of the present application under a 200x microscope dark field mode;

Figure 8 is an apparent blackness diagram of the ordinary black material layer provided in Comparative Example 1 of the present application under a 200x microscope dark field mode.

Explanation of reference symbols:
10-circuit board; 11-soldering pad; 20-photosensitive resin layer; 30-super black material layer; 40-transparent photosensitive resin layer; 50-super black composite coating.

To better describe and illustrate embodiments and/or examples of those applications disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the figures should not be construed as limiting the scope of any of the disclosed applications, the embodiments and/or examples presently described, and the best mode currently understood of these applications.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the accompanying drawings. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided for the purpose of making the disclosure of the present application more thorough and comprehensive.

In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number or order of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of this application, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing specific embodiments only and is not intended to limit the application.

This application provides a method for preparing a circuit board containing an ultra-black composite coating, which includes the following steps:

In step S11, please refer to Figure 1 to provide a circuit board 10.

In one embodiment, the circuit board 10 includes pads 11 .

Step S12 , forming a photosensitive resin layer 20 on the circuit board 10 .

Specifically, photosensitive resin may be formed on the circuit board 10 by printing or spraying, and the photosensitive resin may be heated to form the photosensitive resin layer 20 . Wherein, the photosensitive resin layer 20 covers the pad 11 .

In one embodiment, the temperature for heating the photosensitive resin can be 65°C to 80°C, and the time for heating the photosensitive resin can be It is 25~40min.

In one embodiment, the thickness of the photosensitive resin layer 20 may be 10-30 μm.

In one embodiment, the photosensitive resin layer 20 may be made of epoxy resin.

Step S13, exposing the photosensitive resin layer 20.

Specifically, the photosensitive resin layer 20 can be exposed using UV with an energy of 500 to 700 mJ/cm ² , so as to facilitate the subsequent peelability of the photosensitive resin layer 20 as the bottom layer of the ultra-black composite coating and provide subsequent graphics.

Step S14: Form an ultra-black material layer 30 on the exposed photosensitive resin layer 20.

Specifically, an ultra-black material can be formed on the photosensitive resin layer 20 after exposure by printing or spraying, and the ultra-black material can be heated to form the ultra-black material layer 30 . Among them, the ultra-black material layer 30 serves as the middle layer of the subsequent ultra-black composite coating to provide a higher black contrast background for the LED module.

In one embodiment, the temperature for heating the ultra-black material may be 60°C to 80°C, and the time for heating the ultra-black material may be 3 to 5 minutes.

In one embodiment, the thickness of the ultra-black material layer 30 may be 5-15 μm. Wherein, the surface of the ultra-black material layer 30 has a micropore structure.

In one embodiment, the ultra-black material layer 30 includes light-absorbing pigments, film-forming substances, additives, and dispersion media.

Wherein, the light-absorbing pigment includes pigment carbon black. In one embodiment, the particle size of the pigment carbon black may be 50 to 100 nm. The pigment carbon black can be dispersed inside or on the surface of the ultra-black material layer 30 , and the pigment carbon black can absorb light to provide a black effect.

In one embodiment, the light-absorbing pigment further includes at least one of carbon microporous spheres, carbon nanotubes and graphene.

In one embodiment, the particle size of the carbon microporous spheres may be 2-15 μm. Wherein, the carbon microporous spheres include micropores. In one embodiment, the pore diameter of the micropores may be 0.5-5 μm. The carbon microporous balls form a microporous structure on the surface of the ultra-black material layer 30 , and light can be reflected back and forth in the microporous structure to reduce the light reflectivity of the surface of the ultra-black material layer 30 .

In one embodiment, the length of the carbon nanotube may be 65-85 nm, and the diameter of the carbon nanotube may be 11-15 nm. The carbon nanotubes form a vertical array tube structure to form a micropore structure on the surface of the ultra-black material layer 30 to increase the absorption of light by the surface of the ultra-black material layer 30 .

In one embodiment, the graphene may be graphene oxide with a large diameter. In one embodiment, the sheet diameter of the graphene may be 5-50 μm. The graphene forms a lamellar structure on the surface of the ultra-black material layer 30 to increase the pores on the surface of the ultra-black material layer 30 and thereby reduce the light reflectivity of the surface of the ultra-black material layer 30 .

The light-absorbing pigments in this application reduce the ultra-black material layer 30's resistance to light by being dispersed in the interior of the ultra-black material layer 30 and on the surface of the ultra-black material layer 30 in different particle sizes and structural forms. The reflectivity thereby improves the blackness of the ultra-black material layer 30 .

In one embodiment, the film-forming material includes at least one of acrylic resin, silicone resin, epoxy modified resin and polyurethane. The film-forming substance in this application gradually wraps or bonds the light-absorbing pigment during the evaporation process of the solvent or dispersion medium, thereby forming a continuous layer of the ultra-black material.

In one embodiment, the auxiliary agents include dispersants, defoaming agents and thickeners. In one embodiment, the dispersant includes at least one of acrylate dispersants, polyacrylic acid and cellulose derivatives. In one embodiment, the defoaming agent includes mineral oil defoaming agent. In one embodiment, the thickener includes cellulose thickener. The additives in this application can increase the compatibility of each component, improve the stability of the material system, and reduce problems such as bubbles and leveling during the spraying process.

In one embodiment, the dispersion medium includes at least one of an alcohol dispersion medium, an ester dispersion medium and an ether dispersion medium. In one embodiment, the alcohol dispersion medium includes at least one of isobutanol, n-butanol and ethanol. In one embodiment, the ester dispersion medium includes at least one of ethyl acetate, butyl acetate and isopropyl acetate. In one embodiment, the ether dispersion medium includes at least one of dipropylene glycol methyl ether, dipropylene glycol butyl ether and ethylene glycol butyl ether. The dispersion medium in this application provides a dispersion carrier for the light-absorbing pigment, the film-forming substance and the auxiliary agent to form a mixture, thereby facilitating subsequent construction.

In one embodiment, the preparation method of the ultra-black material includes the following steps:

Step S141: First add a dispersant to the dispersion medium and mix well, then add pigment carbon black, grind and disperse at a rotation speed of 900-1200 r/min for 10-15 minutes, and filter with a 200 mesh mesh to obtain a pigment carbon black slurry for later use.

In one embodiment, in the pigment carbon black slurry, the mass ratio of the dispersion medium to the pigment carbon black may be 7:1˜3:1.

Step S142, add another light-absorbing pigment and dispersant into the dispersion medium, and stir at a rotation speed of 700 to 800 r/min. Disperse for 10 to 15 minutes, and filter with a 200-mesh mesh to obtain a light-absorbing pigment dispersion for later use.

In one embodiment, in the light-absorbing pigment dispersion, the mass ratio of the dispersion medium to the light-absorbing pigment may be 12:1˜8:1.

Step S143, add a dispersion medium to the stirring film-forming material for dilution, and then add the prepared pigment carbon black slurry and the prepared carbon nanotube dispersion in sequence at a mass ratio of 6:1 to 3:1. , stir evenly at a speed of 500-700r/min, add defoaming agent, and finally add thickener to adjust to a suitable viscosity to obtain ultra-black material.

In one embodiment, in the ultra-black material, the mass ratio of the light-absorbing pigment (including pigment carbon black) to the film-forming material may be 1:1.2˜1:0.5, and the mass ratio of the light-absorbing pigment to the film-forming material The ratio of film-forming substances to the total mass of the ultra-black material can be 15% to 44%.

In step S15, a transparent photosensitive resin layer 40 is formed on the ultra-black material layer 30.

Specifically, a transparent photosensitive resin can be formed on the ultra-black material layer 30 by printing or spraying, and the transparent photosensitive resin can be heated to form the transparent photosensitive resin layer 40 .

In one embodiment, the temperature for heating the transparent photosensitive resin can be 65°C to 80°C, and the time for heating the transparent photosensitive resin can be 25 to 40 minutes.

In one embodiment, the thickness of the transparent photosensitive resin layer 40 may be 5-15 μm. The transparent photosensitive resin layer 40 serves as the top layer of the subsequent ultra-black composite coating to protect the micropore structure on the surface of the ultra-black material layer 30 .

In one embodiment, the photosensitive resin layer 40 may be made of epoxy resin.

Step S16, expose the transparent photosensitive resin layer 40, and develop the exposed transparent photosensitive resin layer 40 and the exposed photosensitive resin layer 20 to expose the bonding pad 11 to obtain an ultra-black composite coating 50 , thereby obtaining a circuit board containing an ultra-black composite coating.

Specifically, the transparent photosensitive resin layer 40 can be exposed by UV with an energy of 400 to 600 mJ/cm ² , and the exposed transparent photosensitive resin can be exposed to a Na ₂ CO ₃ aqueous solution with a mass fraction of 1% as a developer. The layer 40 and the exposed photosensitive resin layer 20 are developed to expose the pad 11 .

It can be understood that since the ultra-black material layer 30 in the middle layer is thin and has low strength, the ultra-black material layer 30 can be washed with appropriate pressure airflow or cleaning liquid after development to remove part of the ultra-black material layer. 30 to peel off, thereby exposing the pad 11, which facilitates the subsequent mounting of chips or solid crystal PCB boards.

In this application, the photosensitive resin layer 20 and the transparent photosensitive resin layer 40 are exposed by UV to depict precise patterns, and the photosensitive resin layer 20, the ultra-black material layer 30 and the transparent layer on the pad 11 are The photosensitive resin layer 40 is peeled off together to expose the pad 11, which improves the precision of the etching pattern of the ultra-black composite coating 50 and avoids the direct attachment of black light-absorbing material to the pad or light-emitting chip in traditional technology. This improves the uniformity of the chip's light emission.

Please refer to Figure 1 again. The present application also provides a circuit board containing an ultra-black composite coating prepared by the above preparation method. The circuit board containing an ultra-black composite coating includes a circuit board 10 and a circuit board located on the circuit board 10 Ultra black composite coating on 50.

In one embodiment, the circuit board 10 includes pads 11 .

In one embodiment, the ultra-black composite coating 50 includes a photosensitive resin layer 20, an ultra-black material layer 30, and a transparent photosensitive resin layer 40 that are stacked in sequence.

In one embodiment, the thickness of the photosensitive resin layer 20 may be 10-30 μm.

In one embodiment, the photosensitive resin layer 20 may be made of epoxy resin.

In one embodiment, the thickness of the ultra-black material layer 30 may be 5-15 μm. Wherein, the surface of the ultra-black material layer 30 has a micropore structure.

In one embodiment, the ultra-black material layer 30 includes light-absorbing pigments, film-forming substances, additives, and dispersion media.

Wherein, the light-absorbing pigment includes pigment carbon black. In one embodiment, the particle size of the pigment carbon black may be 50 to 100 nm. The pigment carbon black can be dispersed inside or on the surface of the ultra-black material layer 30 , and the pigment carbon black can absorb light to provide a black effect.

In one embodiment, the light-absorbing pigment further includes at least one of carbon microporous spheres, carbon nanotubes and graphene.

In one embodiment, the particle size of the carbon microporous spheres may be 2-15 μm. Wherein, the carbon microporous spheres include micropores. In one embodiment, the pore diameter of the micropores may be 0.5-5 μm. The carbon microporous balls form a microporous structure on the surface of the ultra-black material layer 30 , and light can be reflected back and forth in the microporous structure to reduce the light reflectivity of the surface of the ultra-black material layer 30 .

In one embodiment, the length of the carbon nanotube may be 65-85 nm, and the diameter of the carbon nanotube may be 11-15 nm. The carbon nanotubes form a vertical array tube structure to form a micropore structure on the surface of the ultra-black material layer 30 to increase the absorption of light by the surface of the ultra-black material layer 30 .

In one embodiment, the graphene may be graphene oxide with a large diameter. In one embodiment, the graphene The sheet diameter size can be 5~50μm. Wherein, the graphene forms a two-dimensional intercalated layer structure on the surface of the ultra-black material layer 30 to increase the pores on the surface of the ultra-black material layer 30 and thereby reduce the light reflection on the surface of the ultra-black material layer 30 Rate.

The light-absorbing pigments in this application reduce the ultra-black material layer 30's resistance to light by being dispersed in the interior of the ultra-black material layer 30 and on the surface of the ultra-black material layer 30 in different particle sizes and structural forms. The reflectivity thereby improves the blackness of the ultra-black material layer 30 .

In one embodiment, the film-forming material includes at least one of acrylic resin, silicone resin, epoxy modified resin and polyurethane. The film-forming substance in this application gradually wraps or bonds the light-absorbing pigment during the evaporation process of the solvent or dispersion medium, thereby forming a continuous layer of the ultra-black material.

In one embodiment, the auxiliary agents include dispersants, defoaming agents and thickeners. In one embodiment, the dispersant includes at least one of acrylate dispersants, polyacrylic acid and cellulose derivatives. In one embodiment, the defoaming agent includes mineral oil defoaming agent. In one embodiment, the thickener includes cellulose thickener. The additives in this application can increase the compatibility of each component, improve the stability of the material system, and reduce problems such as bubbles and leveling during the spraying process.

In one embodiment, the dispersion medium includes at least one of an alcohol dispersion medium, an ester dispersion medium and an ether dispersion medium. In one embodiment, the alcohol dispersion medium includes at least one of isobutanol, n-butanol and ethanol. In one embodiment, the ester dispersion medium includes at least one of ethyl acetate, butyl acetate and isopropyl acetate. In one embodiment, the ether dispersion medium includes at least one of dipropylene glycol methyl ether, dipropylene glycol butyl ether and ethylene glycol butyl ether. The dispersion medium in this application provides a dispersion carrier for the light-absorbing pigment, the film-forming substance and the auxiliary agent to form a mixture, thereby facilitating subsequent construction.

In one embodiment, the thickness of the transparent photosensitive resin layer 40 may be 5-15 μm. The transparent photosensitive resin layer 40 serves as the top layer of the subsequent ultra-black composite coating to protect the micropore structure on the surface of the ultra-black material layer 30 .

In one embodiment, the photosensitive resin layer 40 may be made of epoxy resin.

The present application will be further described below through specific examples and comparative examples.

Example 1

In the first step, select pigment carbon black with a particle size of 50 to 100 nm, add the pigment carbon black and dispersant to the dispersion medium, and pre-disperse it into a pigment carbon black slurry for later use. In the pigment carbon black slurry, the pigment carbon black is dispersed The mass ratio of medium to pigment carbon black is 5:1.

In the second step, carbon nanotubes with a diameter of 65 to 85 nm and a length of 11 to 15 μm are selected, and the carbon nanotubes and dispersant are added to the dispersion medium to predisperse them into a carbon nanotube dispersion for later use. In the liquid, the mass ratio of dispersion medium and carbon nanotubes is 10:1.

In the third step, add dispersion medium to the stirring epoxy resin for dilution, and then add the pigment carbon black slurry in the first step and the carbon nanotube dispersion in the second step in sequence at a mass ratio of 5:1. Among them, add the defoaming agent after stirring evenly, and finally add the thickening agent to adjust to the appropriate viscosity to obtain the ultra-black material.

The fourth step is to provide a PCB board with a pad, spray a layer of photosensitive resin on the pad surface, and pre-bake the photosensitive resin at 75°C for 30 minutes to obtain a photosensitive resin layer with a thickness of 10 to 30 μm, and then bake the photosensitive resin layer. The photosensitive resin layer is UV exposed at an energy of 500-700mJ/ ^cm2 .

In the fifth step, the above-mentioned ultra-black material is sprayed onto the above-mentioned exposed photosensitive resin layer by spraying, and the ultra-black material is pre-baked at 60°C to 80°C for 3 minutes to obtain an ultra-black layer with a thickness of 5-15 μm. material layer.

The sixth step is to spray a layer of transparent photosensitive resin on the above-mentioned ultra-black material layer, and pre-bake the transparent photosensitive resin at 75°C for 30 minutes to obtain a transparent photosensitive resin layer with a thickness of 5 to 15 μm. Then the transparent photosensitive resin layer is UV exposure is performed at an energy of 400~600mJ/ ^cm2 .

The seventh step is to develop the exposed photosensitive resin layer and the exposed transparent photosensitive resin layer in a Na ₂ CO ₃ aqueous solution with a mass fraction of 1% for 30 to 60 seconds, and then clean and peel off the ultra-black material layer on the pad to expose pad, and then bake the developed photosensitive resin layer and the developed transparent photosensitive resin layer at 150°C for 30 minutes to obtain a fully cured ultra-black composite coating, thereby obtaining a circuit board containing an ultra-black composite coating. Among them, circuit boards containing ultra-black composite coatings can be used for subsequent chip mounting or die bonding to prepare high-contrast LED modules.

Example 2

The preparation method of Example 2 is basically the same as that of Example 1, except that:

In the second step, carbon microporous balls with a diameter of 65 to 85 nm and a length of 11 to 15 μm are selected, and the carbon microporous balls and dispersant are added to the dispersion medium to pre-disperse into a carbon microporous ball dispersion for later use; accordingly , in the third step, add the pigment carbon black slurry and carbon microporous ball dispersion to the epoxy resin at a mass ratio of 5:1.

Example 3

The preparation method of Example 3 is basically the same as that of Example 1, except that:

In the second step, graphene oxide with a sheet diameter of 5 to 50 μm is selected, and graphene oxide and dispersant are added to the dispersion medium to predisperse it into a graphene oxide dispersion for later use; accordingly, in the third step, Add the pigment carbon black slurry and graphene oxide dispersion to the epoxy resin at a mass ratio of 5:1.

Comparative example 1

In the first step, select pigment carbon black with a particle size of 50 to 100 nm, add the pigment carbon black and dispersant to the dispersion medium, and predisperse it into a pigment carbon black slurry for later use.

In the second step, add the dispersion medium to the stirring epoxy resin to dilute it, then add the pigment carbon black slurry in the first step in sequence with a mass ratio of 5:1, stir evenly and add the defoaming agent, and finally Add thickener to adjust to appropriate viscosity to obtain ordinary black material.

The third step is to provide a PCB board with a pad, spray a layer of photosensitive resin on the pad surface, and pre-bake the photosensitive resin at 75°C for 30 minutes to obtain a photosensitive resin layer with a thickness of 10 to 30 μm, and then apply the photosensitive resin layer to the pad surface. The photosensitive resin layer is UV exposed at an energy of 500-700mJ/ ^cm2 .

The fourth step is to spray the above-mentioned ordinary black material onto the above-mentioned exposed photosensitive resin layer by spraying, and pre-bake the ordinary black material at 60℃~80℃ for 3 minutes to obtain an ordinary black with a thickness of 5~15μm. material layer.

The fifth step is to develop the above-exposed photosensitive resin layer in a Na ₂ CO ₃ aqueous solution with a mass fraction of 1% for 30 to 60 seconds, then clean and peel off the ordinary black material layer on the pad to expose the pad, and then remove the developed The photosensitive resin layer is baked at 150°C for 30 minutes to obtain a fully cured ordinary black material composite coating, thereby obtaining a circuit board with an ordinary black material composite coating. Among them, ordinary black material composite-coated circuit boards can be used for subsequent chip mounting or die bonding to prepare high-contrast LED modules.

Comparative example 2

In the first step, select pigment carbon black with a particle size of 50 to 100 nm, add the pigment carbon black and dispersant to the dispersion medium, and pre-disperse it into a pigment carbon black slurry for later use. In the pigment carbon black slurry, the pigment carbon black is dispersed The mass ratio of medium to pigment carbon black is 5:1.

In the second step, carbon nanotubes with a diameter of 65 to 85 nm and a length of 11 to 15 μm are selected, and the carbon nanotubes and dispersant are added to the dispersion medium to predisperse them into a carbon nanotube dispersion for later use. In the carbon nanotube dispersion, , dispersion medium and carbon nanotubes The mass ratio is 10:1.

In the third step, add dispersion medium to the stirring epoxy resin for dilution, and then add the pigment carbon black slurry in the first step and the carbon nanotube dispersion in the second step in sequence at a mass ratio of 5:1. Among them, add the defoaming agent after stirring evenly, and finally add the thickening agent to adjust to the appropriate viscosity to obtain the ultra-black material.

The fourth step is to provide a PCB board with a pad, spray a layer of photosensitive resin on the pad surface, and pre-bake the photosensitive resin at 75°C for 30 minutes to obtain a photosensitive resin layer with a thickness of 10 to 30 μm, and then bake the photosensitive resin layer. The photosensitive resin layer is UV exposed at an energy of 500-700mJ/ ^cm2 .

In the fifth step, the above-mentioned ultra-black material is sprayed onto the above-mentioned exposed photosensitive resin layer by spraying, and the ultra-black material is pre-baked at 60°C to 80°C for 3 minutes to obtain an ultra-black layer with a thickness of 5-15 μm. material layer.

The sixth step is to develop the above-exposed photosensitive resin layer in a Na ₂ CO ₃ aqueous solution with a mass fraction of 1% for 30 to 60 seconds, then clean and peel off the ultra-black material layer on the pad to expose the pad, and then remove the developed The photosensitive resin layer is baked at 150°C for 30 minutes to obtain a completely cured ultra-black composite coating, thereby obtaining a circuit board containing an ultra-black composite coating. Among them, circuit boards containing ultra-black composite coatings can be used for subsequent chip mounting or die bonding to prepare high-contrast LED modules.

Comparative example 3

In the first step, select pigment carbon black with a particle size of 50 to 100 nm, add the pigment carbon black and dispersant to the dispersion medium, and pre-disperse it into a pigment carbon black slurry for later use. In the pigment carbon black slurry, the pigment carbon black is dispersed The mass ratio of medium to pigment carbon black is 5:1.

In the second step, carbon nanotubes with a diameter of 65 to 85 nm and a length of 11 to 15 μm are selected, and the carbon nanotubes and dispersant are added to the dispersion medium to predisperse them into a carbon nanotube dispersion for later use. In the liquid, the mass ratio of dispersion medium and carbon nanotubes is 10:1.

In the third step, add dispersion medium to the stirring epoxy resin for dilution, and then add the pigment carbon black slurry in the first step and the carbon nanotube dispersion in the second step in sequence at a mass ratio of 5:1. Among them, add the defoaming agent after stirring evenly, and finally add the thickening agent to adjust to the appropriate viscosity to obtain the ultra-black material.

The fourth step is to provide a PCB board with a soldering pad, spray the above-mentioned ultra-black material onto the pad surface by spraying, and pre-bake the ultra-black material at 60°C to 80°C for 30 minutes to obtain a thickness of An ultra-black material layer of 5 to 15 μm is obtained, thereby obtaining a circuit board containing an ultra-black material layer.

The ultra-black composite coating in the cured circuit boards containing ultra-black composite coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 3 and the cured circuit boards containing ordinary black material composite coatings were compared. The ordinary black material composite coating was subjected to brightness test, adhesion test and scratch resistance test respectively. The test results are shown in Table 1 below.

The specific brightness test is: the brightness value 1 to brightness value 4 in Table 1 refers to testing the brightness values of different ultra-black composite coating surfaces or ordinary black material composite coating surfaces at the same position under four different illumination environments. (reflected brightness). The adhesion test is the hundred grid method. The scratch resistance test standard is customized by yourself, scratch it lightly with your fingernail, and then wipe it gently with a dust-free cloth to see if there are any traces.

Table 1

From the test results in Table 1 above, it can be seen that the tested surface reflection brightness values of the ultra-black composite coatings prepared in Examples 1 to 3 under four illumination environments are lower than those of the ordinary black material composite coating prepared in Comparative Example 1. Brightness value, the brightness ratio of Comparative Example 1 and Examples 1 to 3 under different illumination environments is between 1.2 and 2.5, according to the display contrast ratio in the standard "Light Emitting Diode (LED) Display Test Method" (SJ/T11281-2017) The calculation method shows that under the same brightness, when any ultra-black material layer in Examples 1 to 3 is used as a black background, the contrast is 1.2 to 2.5 times that of the ordinary black material layer in Comparative Example 1 when it is used as a black background. When the black background material is the ultra-black material layer in Embodiment 3, the contrast can be increased to 2.5 times under an illumination environment with a brightness value of 1, and can be used as a black background in the gap between LED module chips to effectively improve its contrast.

Referring to Figures 2 to 4, it can be seen that the surfaces of the ultra-black material layers prepared in Examples 1 to 3 all have microstructures.

Referring to Figures 5 to 8, it can be seen that the blackness of the ultra-black material layers prepared in Examples 1 to 3 is better than the blackness of the ordinary black material layer prepared in Comparative Example 1.

Please refer to Table 1 again. It can be seen from the adhesion and scratch resistance test results in Comparative Example 2 and Comparative Example 3 that the adhesion and surface scratch resistance of a separate ultra-black material layer are relatively poor. Adding a photosensitive resin layer It can improve the adhesion of the ultra-black material layer on the PCB substrate to level 0; it can be seen from Comparative Example 2 and Examples 1 to 3 that adding a transparent photosensitive resin layer can improve the scratch resistance of the ultra-black material layer. It reduces the risk of inconsistent light reflectivity caused by damage to the surface structure of the ultra-black material layer.

In this application, the ultra-black composite coating 50 is prepared by using the photosensitive resin layer 20 as the bottom layer, the ultra-black material layer 30 as the middle layer, and the transparent photosensitive resin layer 40 as the top layer. Coated circuit boards are used in high-contrast LED modules. Wherein, the photosensitive resin layer 20 in the ultra-black composite coating 50 can provide insulation resistance, support strength, and enhance the adhesion of the ultra-black material layer 30 for the ultra-black material layer 30; The black material layer 30 can greatly reduce the reflectivity of the ultra-black composite coating 50 and improve the blackness of the ultra-black composite coating 50; the transparent photosensitive resin layer 40 can cover the ultra-black material layer 30 , so as to effectively protect the micropore structure on the surface of the ultra-black material layer 30 without having a great impact on the reflectivity of the ultra-black material layer 30 . In addition, the bottom layer and the top layer of the ultra-black composite coating 50 are both photosensitive resins. Through UV exposure and development and then peeling off the ultra-black composite coating 50 on the pad 11, a high-definition pattern can be formed. The bonding pad 11 is accurately exposed, thereby effectively applying the ultra-black material layer 30 to the LED module, while avoiding the inconsistent luminescence caused by the material adhering to the bonding pad or the light-emitting chip in the existing ordinary black material printing process. problem, which greatly improves the contrast of the LED module.

The technical features of the above-described embodiments can be combined in any way. To simplify the description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, All should be considered to be within the scope of this manual.

The above-described embodiments only express several implementation modes of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims (10)

1. A method for preparing a circuit board containing an ultra-black composite coating, which is characterized by including the following steps:

   providing a circuit board, the circuit board including solder pads;

   Form a photosensitive resin layer on the circuit board;

   Exposing the photosensitive resin layer;

   Form an ultra-black material layer on the exposed photosensitive resin layer;

   forming a transparent photosensitive resin layer on the ultra-black material layer; and

   Exposing the transparent photosensitive resin layer, and developing the exposed transparent photosensitive resin layer and the exposed photosensitive resin layer to expose the bonding pad to obtain an ultra-black composite coating, thereby obtaining a composite coating containing ultra-black layer of circuit board.
2. The method for preparing a circuit board containing an ultra-black composite coating according to claim 1, wherein the preparation materials for the ultra-black material layer include light-absorbing pigments, film-forming substances, additives and dispersion media.
3. The method for preparing a circuit board containing an ultra-black composite coating according to claim 2, wherein the light-absorbing pigment includes pigment carbon black, and the light-absorbing pigment further includes carbon microporous spheres, carbon nanotubes and graphene. At least one of the above, the surface of the ultra-black material layer has a micropore structure.
4. The method for preparing a circuit board containing an ultra-black composite coating according to claim 3, wherein the particle size of the pigment carbon black is 50-100 nm, and/or the particle size of the carbon microporous spheres is 2 to 15 μm, and/or the carbon microporous spheres include micropores, and/or the pore diameter of the micropores is 0.5 to 5 μm, and/or the length of the carbon nanotubes is 65 to 85 nm, and/or the The diameter of the carbon nanotube is 11-15 nm, and/or the sheet diameter of the graphene is 5-50 μm.
5. The method for preparing a circuit board containing an ultra-black composite coating according to any one of claims 1 to 4, wherein the thickness of the photosensitive resin layer is 10-30 μm, and/or the ultra-black material The thickness of the layer is 5-15 μm, and/or the thickness of the transparent photosensitive resin layer is 5-15 μm.
6. The method for preparing a circuit board containing an ultra-black composite coating according to any one of claims 1 to 4, wherein forming the photosensitive resin layer on the circuit board specifically includes the following steps:

   Cover the circuit board with photosensitive resin by spraying or printing; and

   heating the photosensitive resin to form the photosensitive resin layer;

   Wherein, the temperature for heating the photosensitive resin is 65°C to 80°C, and the time for heating the photosensitive resin is 25 to 40 minutes.
7. The method for preparing a circuit board containing an ultra-black composite coating according to any one of claims 1 to 4, wherein forming the ultra-black material layer on the exposed photosensitive resin layer specifically includes the following steps: step:

   Cover the ultra-black material on the exposed photosensitive resin layer by spraying or printing; and

   heating the ultra-black material to form the ultra-black material layer;

   Wherein, the temperature for heating the ultra-black material is 60°C to 80°C, and the time for heating the ultra-black material is 3 to 5 minutes.
8. The method for preparing a circuit board containing an ultra-black composite coating according to any one of claims 1 to 4, wherein forming the transparent photosensitive resin layer on the ultra-black material layer specifically includes the following steps:

   Form the transparent photosensitive resin on the ultra-black material layer by spraying or printing; and heat the transparent photosensitive resin to form the transparent photosensitive resin layer;

   Wherein, the temperature for heating the transparent photosensitive resin is 65°C to 80°C, and the time for heating the transparent photosensitive resin is 25 to 40 minutes.
9. A circuit board containing an ultra-black composite coating, characterized in that the circuit board containing an ultra-black composite coating is prepared by the preparation method according to any one of claims 1 to 8.
10. A display device, characterized in that the display device includes a circuit board containing an ultra-black composite coating as claimed in claim 9.