TWI666297B - An ultra-thin white cover film and led substrate using the same - Google Patents

Abstract

A white cover film and an LED substrate. The white cover film includes an adhesive layer; and a white ink layer formed on the adhesive layer, which is selected from the group consisting of an organic pigment and a white filler, an inorganic pigment, and an organic pigment. At least one of the group consisting of: the inorganic pigment is a white pigment or a gray pigment; the organic pigment is a low-light-transmitting polymer; and its light transmittance is 0 to 1%; the white filler is selected from the group consisting of silicon dioxide, titanium dioxide, At least one powder of a group consisting of alumina and alumina, and the total thickness of the white ink layer and the adhesive layer is 4 to 50 microns. The invention has the characteristics of low dielectric constant and loss, low transmittance, low gloss, low rebound force, high ion purity, high reflectivity, high flexibility, high surface hardness, high temperature yellowing resistance and good weather resistance. Suitable for LED lighting of flexible and rigid board.

Description

   Ultra-thin white cover film and LED substrate using the white cover film   

The present invention relates to a cover film for an LED (light emitting diode), and more particularly to an ultra-thin white cover film and an LED substrate using the white cover film.

With the development of the information and communication industry, a flexible printed circuit board (FPC), which has driven the rapid development of the microelectronics industry, came into being and has developed rapidly. It has been used in many fields such as mobile phones, liquid crystal displays, and flat panels. widely used. The biggest difference between a flexible printed circuit board and a PCB (Printed Circuit Board) is that the former uses a cover film, which is different from the solder mask ink used for PCBs. It not only has a solder mask effect, but also protects the FPC from dust, moisture, Chemical attack also reduces the effects of stress during bending. In addition, with the development of the FPC market, the cover film has been given more functions. Among them, the white cover film has the characteristics of high reflectivity, low transmittance, high temperature resistance, and weather resistance. In the field of LED light bars. Given the current global energy shortage concerns, energy conservation is an important issue facing us in the future. In the lighting field, the application of LED lighting products is attracting the attention of the world. As a new type of green light source products, LED is bound to be the future The development trend, the 21st century will enter the era of new lighting sources represented by LEDs.

At present, the traditional process of white LED light strip products is selected from one of the following methods: the first type: the cover film is pressed on the substrate after opening the window, and then the surface is coated with a layer after low temperature drying White ink A100, to improve the contrast of LED products and enhance the printing effect, but the disadvantages are uneven printing thickness and poor flexibility (as shown in Figure 1); the second: as shown in Figure 2 A white ink cover film is directly attached to the flexible printed circuit board. The white ink cover film includes a first white ink layer B100, a yellow PI (polyimide) layer B200, a first adhesive layer B300, and The first release layer B400 can achieve the purpose of reducing the downstream process, but the white ink cover film has poor high temperature yellowing resistance and is difficult to achieve thinning; the third type: as shown in Figure 3, covered with white PI The film is directly attached to a flexible printed circuit board. The white PI cover film system includes a white PI layer C100, a white adhesive layer C200, and a second release layer C300. It has high temperature yellowing resistance, good weather resistance and high Characteristics of reflectivity, but its cost is high and thinning is difficult Now.

In order to meet the needs of the market, the present invention aims to develop an ultra-thin white cover film with high reflectivity, high temperature yellowing resistance, low rebound force, and low manufacturing cost, which is suitable for the field of LED lighting.

The invention provides a white cover film for an LED substrate and an LED substrate using the white cover film, which has extremely low dielectric constant and loss, low rebound force, low transmittance, low gloss, extremely high ionic purity, high Ultra-thin white cover film with high reflectivity, high flexibility, high surface hardness, high temperature yellowing resistance, and good weather resistance for high-performance LED lighting of flexible and rigid boards.

The invention provides an ultra-thin white cover film, which includes: an adhesive layer having a thickness of 3 to 25 microns; and a white ink layer having a thickness of 1 to 25 microns, which is formed on the adhesive layer and the white ink layer And the adhesive layer have a total thickness of 4 to 50 microns; wherein the white ink layer is at least one selected from the group consisting of a combination of an organic pigment and a white filler, an inorganic pigment, and an organic pigment, and the The inorganic pigment is a white pigment or a gray pigment. The organic pigment is a low-light-transmitting polymer with a light transmittance of 0 to 1%. The white filler is selected from the group consisting of silicon dioxide, titanium dioxide, alumina, and alumina. At least one powder of the group; wherein the hardness value of the white cover film is HB to 5H, the 60 ° gloss on the surface of the white ink layer is 0 to 50GU, and the surface roughness of the surface of the white ink layer is 50 to 10000 Nanometer, the average yellowing resistance (△ L value) at 260 ℃ is less than 3, the reflectivity is greater than 90%, the rebound force is less than 5 grams, and the light transmittance is less than 1%.

In a specific embodiment, the total thickness of the white ink layer and the adhesive layer is 6 to 15 microns, wherein the thickness of the white ink layer is 3 to 5 microns, and the thickness of the adhesive layer The thickness is 3 to 10 microns.

In a specific embodiment, the low-light-transmitting polymer is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, parylene resin, and bismaleic acid. At least one of the group consisting of an imine resin, a polyimide resin, a polyimide resin, a polyimide-fluorimide resin, and a polyurethane resin.

In a specific embodiment, the white ink layer contains a matting powder, and the D90 particle size of the matting powder is 2 to 12 microns.

In another embodiment, the matting powder system is selected from at least one of the group consisting of inorganic compounds, organic compounds, and flame retardant compounds, and the inorganic compound is selected from calcium sulfate, silicon dioxide, At least one of the group consisting of titanium dioxide, zinc sulfide, zirconia, calcium carbonate, boron nitride, aluminum hydroxide, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder, corundum and clay, the organic The compound is a polyimide-based resin, and the flame-retardant compound is at least one selected from the group consisting of a halogen-containing compound, a phosphorus-based compound, a nitrogen-based compound, and a boron-based compound.

In a specific embodiment, the adhesive layer is an adhesive layer, wherein the dielectric constant (Dk value) of the adhesive layer at a measurement frequency of 10 GHz is 2.4 to 2.8, and the adhesive layer is at a measurement frequency of 10 GHz. The dielectric loss (Df value) is 0.002 to 0.006, and its water absorption is between 0.03 to 0.2%, and its line-to-line insulation resistance is greater than 10 ¹¹ ohms (Ω), and its surface resistance is greater than 10 ¹² ohms (Ω), and Its volume resistance is greater than 10 ¹³ ohm-cm (Ω-cm).

In another specific embodiment, the adhesive layer system includes sintered silicon dioxide, Teflon, fluorine-based resin, phosphorus-based flame retardant, and low-dielectric polyfluorene imide resin having a low Dk / Df value. Wherein, the dielectric constant of the low-dielectric polyfluorene imide resin is 2.4 to 2.5, and the dielectric loss thereof is 0.002 to 0.003, and the sintered silicon dioxide, the Teflon, the fluorine-based resin, and the phosphorus-based The total proportion of the flame retardants is 8 to 50% by weight of the total solid content, and the proportion of the low-dielectric polyfluorene imine resin is 40 to 90% by weight.

In a specific embodiment, the ultra-thin white coverlay film includes a release layer formed on the white ink layer, and a release layer formed on the adhesive layer. In a specific embodiment, the upper release layer is a matting release film, and the surface roughness (Rz value) of the contact surface between the matting release film and the white ink layer is 0.2 to 10 microns.

In another embodiment, the material forming the upper release layer and the lower release layer is independently selected from the group consisting of polypropylene, biaxially oriented polypropylene, and polyethylene terephthalate. At least one of the group.

The invention further provides an LED substrate, comprising: a base layer; and any one of the above-mentioned ultra-thin white cover films, disposed on the base layer, wherein the white ink layer is located between the base layer and the adhesive layer.

The invention further provides a method for preparing an ultra-thin white cover film, which comprises: coating a white ink material on a specified release surface of an upper release layer, and curing the white ink material at 100 to 200 ° C. to form a white ink layer. Wherein, the white ink raw material is at least one selected from the group consisting of a combination of an organic pigment and a white filler, an inorganic pigment, and an organic pigment, and the inorganic pigment is a white pigment or a gray pigment, and the organic pigment is a low permeability The photopolymer has a light transmittance of 0 to 1%. The white filler is at least one selected from the group consisting of silicon dioxide, titanium dioxide, alumina, and alumina; An agent layer is formed on the white ink layer; and a lower release layer is covered on the adhesive layer, so that the adhesive layer is located between the white ink layer and the lower release layer.

The effect of the present invention has at least the following points:

1. The 60 ° gloss of the white cover film of the present invention is 0 to 50GU, preferably less than 5GU; its hardness value is HB to 5H, preferably 2H to 5H; and its surface roughness is 50 to 10000 Nanometer, and its high hardness can prevent the surface from being scratched, and it is not easy to be corroded by chemical reagents in the downstream process, and has good weather resistance.

2. The white ink layer of the present invention has a matting effect when the matting powder is contained, so that the white ink layer has a matte state. In addition, the degree of matting of the coated film surface can be adjusted by controlling the particle size of the powder. The smaller the particle size of the matte powder, the larger the surface gloss (gloss) value, that is, the brighter the surface morphology. By adjusting the matte powder Particle size, type and content, etc., to obtain the desired product (such as gloss, flame resistance, hardness or cost, etc.), and the addition of matting powder to further enhance the hardness of the white ink layer, so that this product has a relatively Good mechanical properties, electrical properties and operability.

3. The upper release layer of the present invention is a matte release film, and the surface roughness (Rz value) of the contact surface with the white ink layer is 0.2 to 10 micrometers. The roughness of the matte release film is passed to cover The white ink layer of the film is easier to separate from the upper release layer, thereby improving the operability of the downstream terminal. At the same time, after the cover film is quickly pressed and the release film layer is torn off, the extinction release film helps the white The surface morphology of the ink layer is matte.

4. The adhesive layer of the present invention contains polyimide resin, sintered silicon dioxide, Teflon, fluorine-based resin, phosphorus-based flame retardant, and low-dielectric polyimide resin, which has a lower dielectric strength. Water absorption rate, not only stable performance after water absorption, good electrical performance, can reduce signal transmission insertion loss, but also has extremely low and stable Dk / Df value under high temperature and humidity environment, making the invention suitable for low temperature (below 180 ℃) Fast pressing under the environment, its process is strong, and low requirements for production equipment, thereby reducing production costs.

5. The total thickness of both the white ink layer and the adhesive layer of the present invention is 4 to 50 micrometers, preferably 6 to 15 micrometers, in order to meet the current design requirements of thin-line FPC circuits.

6. The invention has a lower rebound force and is suitable for downstream high-density assembly processes.

7. The present invention is composed of a white ink layer and an adhesive layer. The structure is reasonable and simple, reducing the process of coating a layer of white ink on the FPC on the cover film, saving man-hours and reducing production costs.

8. The white ink layer of the present invention does not cause yellowing in the process of fast pressing, cover film aging and SMT in the FPC process, and the surface has the protection of the release layer from being contaminated, discolored or containing impurities , There will be no abnormal phenomena such as etching and plating solution penetration, thereby improving product yield.

100‧‧‧white ink layer

200‧‧‧ Adhesive layer

300‧‧‧ Upper release layer

400‧‧‧ lower release layer

500‧‧‧ basal layer

A100‧‧‧White ink

B100‧‧‧The first white ink layer

B200‧‧‧Yellow PI (Polyimide) layer

B300‧‧‧The first adhesive layer

B400‧‧‧The first release layer

C100‧‧‧White PI layer

C200‧‧‧white adhesive layer

C300‧‧‧Second Release Layer

The embodiments of the present invention will be described by way of example with reference to the accompanying drawings: FIG. 1 is a schematic diagram of a structure of a white ink layer; FIG. 2 is a schematic diagram of a structure in which a conventional white ink cover film is attached to a flexible printed circuit board; Figure 3 is a schematic diagram of a conventional white PI cover film attached to a flexible printed circuit board; Figure 4 is a schematic diagram of a white cover film of the present invention; and Figure 5 is a schematic diagram of a LED substrate of the present invention. .

The following is a description of specific embodiments of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this specification are only used to match the content disclosed in the specification for the understanding and reading of those skilled in the art, and are not intended to limit the implementation of the present invention. The limited conditions are not technically significant. Any modification of the structure, change of the proportional relationship, or adjustment of the size should still fall within the scope of this invention without affecting the effects and goals that can be achieved by the present invention. The technical content disclosed by the invention can be covered. At the same time, the references such as “一”, “下” and “上” in this specification are for clarity only, and are not intended to limit the scope of the present invention. Substantially changing the technical content should also be regarded as the scope in which the present invention can be implemented. In addition, all ranges and values herein are inclusive and combinable. Any value or point that falls within the range described herein, for example, any integer can be used as the minimum or maximum value to derive the lower range, etc.

As shown in FIG. 4, the present invention provides an ultra-thin white cover film including: an adhesive layer 200 having a thickness of 3 to 25 μm; and a white ink layer 100 having a thickness of 1 to 25 μm, which is formed on the adhesive The top surface of the adhesive layer 200, and the total thickness of the white ink layer 100 and the adhesive layer 200 is 4 to 50 microns.

The white ink layer 100 is at least one selected from the group consisting of a combination of an organic pigment and a white filler, an inorganic pigment, and an organic pigment, and the inorganic pigment is a white pigment or a gray pigment, and the organic pigment is low-light transmission The polymer has a light transmittance of 0 to 1%. The white filler is at least one powder selected from the group consisting of silicon dioxide, titanium dioxide, alumina, and alumina.

The hardness value of the white cover film is HB to 5H, and preferably 2H to 5H.

The 60 ° gloss of the surface of the white ink layer of the white cover film is 0 to 50 GU, particularly preferably 0 to 5 GU.

The surface roughness (Rz value) on the side of the white ink layer of the white cover film is 50 to 10,000 nanometers, particularly preferably 600 to 800 nanometers.

The average high temperature yellowing resistance (ΔL value) of the white cover film at 260 ° C is less than 3, and preferably 0.5 to 1.5.

The reflectance of the white cover film is greater than 90%, and preferably 90 to 95%.

The rebound force of the white cover film is less than 5 grams, and preferably 4.0 to 4.2 grams.

The light transmittance of the white cover film is less than 1%, and preferably 0.2 to 0.4.

In a specific embodiment, the total thickness of the white ink layer 100 and the adhesive layer 200 is 6 to 15 microns, wherein the thickness of the white ink layer 100 is 3 to 5 microns, and the adhesive The thickness of the agent layer 200 is 3 to 10 micrometers.

In one embodiment, the white ink layer is preferably a combination of an organic pigment and a white filler.

The low-light-transmitting polymer is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, parylene resin, bismaleimide resin, and polyfluorene. At least one of the group consisting of an amine resin, a polyamide resin, a polyamide-amimine resin, and a polyurethane resin.

In a specific embodiment, the white ink layer is an ink layer containing a matting powder, and the D90 particle size of the matting powder is 2 to 12 microns.

In another embodiment, the matting powder system is selected from at least one of the group consisting of inorganic compounds, organic compounds, and flame retardant compounds, and the inorganic compound is selected from calcium sulfate, silicon dioxide, At least one of the group consisting of titanium dioxide, zinc sulfide, zirconia, calcium carbonate, boron nitride, aluminum hydroxide, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder, corundum and clay, the organic The compound is a polyimide-based resin, and the flame-retardant compound is at least one selected from the group consisting of a halogen-containing compound, a phosphorus-based compound, a nitrogen-based compound, and a boron-based compound.

In yet another specific embodiment, the matting powder includes only silicon dioxide, talc, calcium carbonate, glass powder, quartz powder, and phosphorus compounds, and the silicon dioxide, talc, calcium carbonate, and glass The powder and quartz powder account for 10 to 50% by weight of the total solid content, and the addition ratio of the phosphorus-based compound accounts for 2 to 40% by weight of the total solid content.

The addition ratio of the matting powder is different, and the performance of the white ink layer is also different. Specifically, in order to meet the requirements of high flame resistance, the matting powder is selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, phosphorus-containing compounds, halogen-containing compounds, nitrogen-containing compounds, and boron-containing compounds. The addition ratio of at least one of the group consisting of the compounds needs to be high. In order to meet the requirements of high hardness, the matting powder needs to have a higher addition ratio of at least one selected from titanium dioxide and silicon dioxide.

In a specific embodiment, the adhesive layer 200 is an adhesive layer, wherein a dielectric constant (Dk value) of the adhesive layer at a measurement frequency of 10 GHz is 2.4 to 2.8, and a measurement frequency thereof at 10 GHz The dielectric loss (Df value) below is 0.002 to 0.006, and its water absorption is between 0.03 and 0.2%, and its line-to-line insulation resistance is greater than 10 ¹¹ ohms (Ω), and its surface resistance is greater than 10 ¹² ohms (Ω), And its volume resistance is greater than 10 ¹³ ohm-cm (Ω-cm).

In a specific embodiment, the adhesive layer 200 series includes sintered silicon dioxide, Teflon, fluorine-based resin, phosphorus-based flame retardant, and low-dielectric polyimide resin, and the sintered silicon dioxide, The total ratio of the Teflon, the fluorine-based resin, and the phosphorus-based flame retardant accounts for 8 to 50% by weight of the total solid content, and the ratio of the low-dielectric polyfluorene imide resin is 40 to 90% by weight.

In a specific embodiment, the ultra-thin white cover film includes a release layer, wherein the release layer includes: an upper release layer 300, which is an extinction layer formed on a surface of the white ink layer 100. A release film, and a surface roughness (Rz value) of a side of the extinction release film in contact with the white ink layer 100 is 0.2 to 10 μm; and a lower release layer 400 is formed on a lower surface of the adhesive layer 200 .

In a specific embodiment, the upper release layer 300 and the lower release layer 400 are each selected from at least a group consisting of polypropylene, biaxially oriented polypropylene, and polyethylene terephthalate. One is a release film or release paper.

As shown in FIG. 5, the present invention further provides an LED substrate including: a base layer 500; and any one of the above-mentioned ultra-thin white cover films disposed on the base layer 500, wherein the white ink layer 100 is located on the base layer 500. Between the base layer 500 and the adhesive layer 200.

The invention further provides a method for preparing an ultra-thin white cover film, which comprises: coating a white ink material on a specified release surface of an upper release layer, and curing the white ink material at 100 to 200 ° C. to form a white ink layer. Wherein, the white ink raw material is at least one selected from the group consisting of a combination of an organic pigment and a white filler, an inorganic pigment, and an organic pigment, and the inorganic pigment is a white pigment or a gray pigment, and the organic pigment is a low permeability The photopolymer has a light transmittance of 0 to 1%. The white filler is at least one selected from the group consisting of silicon dioxide, titanium dioxide, alumina, and alumina; An agent layer is formed on the white ink layer; and a lower release layer is covered on the adhesive layer, so that the adhesive layer is located between the white ink layer and the lower release layer.

Example 1:

White ink raw materials include inorganic pigments and organic pigments. Among them, aniline black and peptide cyan blue are used as organic pigments, and the sum of the proportion of organic pigments accounts for 10% by weight of the total solids content, and titanium dioxide and carbon black are used as inorganic pigments. The sum of the proportions of its inorganic pigments accounts for 35% by weight of the total solid content, and the remaining proportions are mixed with butadiene rubber, methyl ethyl ketone solvent and resin to make a white ink raw material.

The above-mentioned white ink raw material is coated on a specified release surface of the upper release layer, and the white ink raw material is cured at 120 ° C. to form a white ink layer with a thickness of 3 μm, and the surface roughness of the white ink layer ( Rz value) is about 6.4 microns.

Next, sintered silicon dioxide, Teflon, fluorine-based resin, phosphorus-based flame retardant, and polyimide resin are selected as the material of the adhesive layer. The dielectric of the polyimide resin at a frequency of 10 GHz is measured. The constant (Dk) is 2.4 and the dielectric loss (Df) is 0.003, the water absorption is 0.05%, the insulation resistance between the wires is> 10 ¹¹ ohms (Ω), the surface resistance is> 10 ¹² ohms (Ω), and the volume resistance is> 10 ¹³ ohms -Cm (Ω-cm). The total ratio of the sintered silicon dioxide, the Teflon, the fluorine-based resin, and the phosphorus-based flame retardant accounted for 15% by weight of the total solids content of the adhesive layer, and the ratio of the polyfluorene imide resin was 50% by weight. %; The adhesive layer is formed on the white ink layer by a coating method to form a 3 μm-thick adhesive layer. Finally, the white ink layer is coated with polypropylene as an upper release layer, and the polypropylene coated on the adhesive layer is used as a lower release layer to obtain an ultra-thin white cover film finished product. The upper release layer is a matte release film, and the surface roughness (Rz value) of the contact surface between the matte release film and the white ink layer is about 6.7 microns.

The methods for preparing the ultra-thin white cover films of Examples 2 to 3 and Comparative Examples 1 to 3 are the same as those in Example 1, except that only the thickness of the white ink layer and the adhesive layer was changed as shown in Table 1. The ultra-thin white cover films were tested. Surface hardness, high temperature resistance to yellowing ΔL value, 60 ° gloss, and reflectance at 500 nm wavelength are recorded in Table 1.

Test Methods:

(1) Surface hardness: The surface hardness is measured according to the colored paint and varnish pencil method of GB / T 6739-2006.

(2) High temperature resistance to yellowing △ L value: Performed in accordance with the standard test method of ASTM E308. After placing the product at 265 ° C for 15 to 20 minutes, use a color difference measuring instrument (model: CM-2300D; purchased from KONICA MINOLTA) Measure the △ L value before and after the test. The △ L value should be less than 1.5 to achieve high temperature and yellowing resistance.

(3) Gloss at 60 °: Gloss instrument (model 4440; purchased from BYK, Germany) and implemented according to ISO 2813 or JIS Z 8741 standard test method. The gloss instrument uses an angle of 60 ° from the normal of the incident surface. The surface of the white ink layer was measured by the incident light, and the surface gloss value was read and recorded.

(4) Reflectance at 500nm wavelength: Reflectance is measured with an integrating sphere spectrometer (SP60; X-Rite) and according to the standard test method of GB9271-88.

(5) Light transmittance: Measured with a haze meter device (model NDH-2000; purchased from Nippon Denshoku).

As can be seen from Table 1, the white cover film of the present invention is formed by stacking a white ink layer and an adhesive layer, and has not only an ultra-thin thickness, but also high surface hardness, low gloss, and low temperature resistance. Yellowish and has a high reflectance greater than 85%.

The preparation methods of the ultra-thin white cover films of the samples 1 to 3 are the same as those of the embodiment 1, except that the type, content, average particle size and surface roughness of the release layer on the surface of the matte powder are shown in Table 1. A commercially available white polyimide film was used as a comparative example, and its ultra-thin white cover film was tested for 60 ° gloss and recorded in Table 2.

As can be seen from Table 2, the roughened upper release layer contributes to reducing the gloss of the finished product, and adding a powder having a large average particle size to the white ink layer can also reduce the gloss of the white ink layer.

The upper and lower release layers of the ultra-thin white cover films of the above-mentioned samples 1 to 3 and comparative examples 1 to 3 were torn off, and a flexible printed circuit board (FPC) was used as a base layer, and white ink was used. The layer is directly attached to a flexible printed circuit board (FPC). As shown in the structure of FIG. 5, the white ink layer is positioned between the FPC and the adhesive layer to make an LED substrate. The rebound force and The thickness is also reported in Table 3.

As can be seen from Table 3, the rebound force of the LED substrate product obtained by combining the ultra-thin white cover film with FPC is much smaller than that of the comparative example, and the rebound force is less than 5.0 grams.

The above-mentioned embodiments are merely illustrative and not intended to limit the present invention. Anyone skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention is defined by the scope of the patent application attached to the present invention, as long as it does not affect the effect and implementation purpose of the present invention, it should be covered in this disclosed technical content.

Claims (11)

An ultra-thin white cover film includes: an adhesive layer having a thickness of 3 to 25 microns; and a white ink layer having a thickness of 1 to 25 microns, formed on the adhesive layer, and the white ink layer and the adhesive The total thickness of the two agent layers is 4 to 50 microns; wherein the white ink layer is at least one selected from the group consisting of a combination of an organic pigment and a white filler, an inorganic pigment, and an organic pigment, and the inorganic pigment is White pigment or gray pigment, the organic pigment is a low-light-transmitting polymer and its light transmittance is 0 to 1%, and the white filler is selected from the group consisting of silica, titania, alumina, and alumina At least one powder; wherein the hardness of the white cover film is HB to 5H, the 60 ° gloss on the surface of the white ink layer is 0 to 50GU, and the surface roughness of the surface of the white ink layer is 50 to 10,000 nm The average yellowing resistance (△ L value) at 260 ° C is less than 3, the reflectivity is greater than 90%, the rebound force is less than 5 grams, and the light transmittance is less than 1%. The ultra-thin white cover film according to item 1 of the scope of the patent application, wherein the low-light-transmitting polymer is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, and polypair At least one selected from the group consisting of a xylene resin, a bismaleimide resin, a polyimide resin, a polyimide resin, a polyimide-fluorimide resin, and a polyurethane resin. The ultra-thin white cover film according to item 1 of the patent application scope, wherein the white ink layer contains a matting powder, and the D90 particle diameter of the matting powder is 2 to 12 microns. The ultra-thin white cover film according to item 3 of the scope of patent application, wherein the matting powder system is at least one selected from the group consisting of an inorganic compound, an organic compound, and a flame-retardant compound, and the inorganic compound is selected Composed of calcium sulfate, silicon dioxide, titanium dioxide, zinc sulfide, zirconia, calcium carbonate, boron nitride, aluminum hydroxide, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder, silicon carbide and clay The organic compound is at least one of the group, the organic compound is a polyimide-based resin, and the flame-retardant compound is at least one selected from the group consisting of a halogen-containing, a phosphorus-based compound, a nitrogen-based compound, and a boron-based compound. The ultra-thin white cover film according to item 1 of the scope of patent application, wherein the dielectric constant (Dk value) of the adhesive layer at a measurement frequency of 10 GHz is 2.4 to 2.8, and the dielectric constant at a measurement frequency of 10 GHz The loss (Df value) is 0.002 to 0.006, the water absorption is 0.03 to 0.2%, the insulation resistance between the wires is greater than 10 ¹¹ ohms (Ω), the surface resistance is greater than 10 ¹² ohms (Ω), and the volume resistance is greater than 10 ¹³ ohm-cm (Ω-cm). The ultra-thin white cover film according to item 1 of the scope of patent application, wherein the adhesive layer includes sintered silicon dioxide, Teflon, fluorine-based resin, phosphorus-based flame retardant, and a low Dk / Df value. Dielectric polyfluorene imide resin; wherein, the low dielectric polyfluorene imide resin has a dielectric constant (Dk) of 2.4 to 2.5, a dielectric loss (Df) of 0.002 to 0.003, and the sintered silicon dioxide, The total ratio of the Teflon, the fluorine-based resin, and the phosphorus-based flame retardant accounts for 8 to 50% by weight of the total solid content, and the ratio of the low-dielectric polyfluorene imide resin is 40 to 90% by weight. The ultra-thin white cover film according to item 1 of the scope of the patent application, which includes a release layer formed on the white ink layer, and a release layer formed on the adhesive layer. The ultra-thin white cover film according to item 7 of the scope of the patent application, wherein the upper release layer is a matte release film, and the surface roughness (Rz value) of the contact surface of the matte release film and the white ink layer ) Is 0.2 to 10 microns. The ultra-thin white cover film according to item 7 of the scope of patent application, wherein the material forming the upper release layer and the lower release layer is independently selected from polypropylene, biaxially oriented polypropylene, and polyterephthalic acid At least one of the groups consisting of ethylene glycol. An LED substrate includes: a base layer; and the ultra-thin white cover film described in item 1 of the scope of patent application, which is provided on the base layer, wherein the white ink layer is located on the base layer and the adhesive layer between. A method for preparing an ultra-thin white cover film as described in item 1 of the scope of patent application, comprising: coating a white ink material on a specified release surface of an upper release layer; and curing the white ink material at 100 to 200 ° C. To form a white ink layer, wherein the white ink raw material is at least one selected from the group consisting of a combination of an organic pigment and a white filler, an inorganic pigment and an organic pigment, and the inorganic pigment is a white pigment or a gray pigment, The organic pigment is a low-light-transmitting polymer and has a light transmittance of 0 to 1%. The white filler is at least one selected from the group consisting of silicon dioxide, titanium dioxide, alumina, and alumina; Or a transfer method to form an adhesive layer on the white ink layer; and apply a lower release layer on the adhesive layer so that the adhesive layer is located between the white ink layer and the lower release layer.