Method for measuring covering power of colored paint

Abstract

The invention provides a method for measuring the covering power of colored paint, and relates to the technical field of paints.The method comprises the steps that to-be-measured colored paint is sprayed to a test board, a film thick board and black and white check test paper in the first direction, and the test board, the film thick board and the black and white check test paper are all located on the spraying track of the to-be-measured colored paint; in the single-time spraying operation process, spraying is carried out through one-way movement along the spraying track, the color value, corresponding to the datum line, of the test plate is the datum color value, the datum line is the boundary between the area covered by the to-be-tested colored paint and the area not covered by the to-be-tested colored paint on the black-and-white check test paper, and the test area is located on the side, away from the spraying track, of the datum line; taking a plurality of color value measurement points in a second direction perpendicular to the first direction in the test area of the test plate, measuring a color difference value between each color value measurement point and the reference color value, and determining an engineering covering power line extending in the first direction based on the color difference values and a preset color difference value to obtain the engineering covering power film thickness. The method is simple, convenient to operate and high in efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, in particular to a method for measuring the hiding power of color paint. Background Art

[0002] With the popularization of automobiles and the explosive development of new energy vehicles, customers have higher requirements for car body color and paint texture. In order to meet customers' requirements for personalized and customized colors, a large number of new effect materials that can be used for car body spraying have emerged in the market to make the paint surface have glittering, transparent and other effects, such as pearlescent, colored aluminum materials, etc. The hiding power of the above colors is different from that of traditional aluminum powder paint or solid color paint, so it is particularly important to accurately test and evaluate the hiding power of new effect materials.

[0003] At present, the detection of paint hiding power mainly refers to the black and white grid spraying method in GB / T23981.2-2023. This method requires multiple spraying, repeated observation of the black and white grid masking state, and finally weighing and calculation after baking. This test method is time-consuming, and multiple spraying requires high consistency of operation, which is prone to errors. Based on the above-mentioned black and white grid spraying method, there is an improved tape masking layered spraying method. This method forms a film thickness step after spraying, and visually and in combination with instrument judgment, determines the black and white grid hiding power and engineering hiding power. Although the tape masking layered spraying method shortens the test time to a certain extent, the layering operation is relatively cumbersome, and the consistency requirements for multiple spraying have not been reduced. At the same time, the film thickness step state is artificially created, the change is more abrupt, and the accuracy of the hiding power test results is limited. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for measuring the hiding power of paint, so as to solve the problem that the method for measuring the hiding power of paint in the prior art is relatively complicated.

[0005] To achieve the above object and other related objects, the present invention provides a method for measuring the hiding power of a paint, comprising:

[0006] Spraying the paint to be tested on the test plate, the film thickness plate and the black and white grid test paper along a first direction, wherein the test plate, the film thickness plate and the black and white grid test paper are all located on the spraying track of the paint to be tested;

[0007] During a single spraying operation, the spraying is performed by unidirectionally moving along the spraying track. After the single spraying operation is completed, the black and white grid test paper is observed. If the black and white grid test paper is located in a covered area on the spraying track and includes at least one complete black grid and one complete white grid, the spraying is stopped. Otherwise, the spraying is continued.

[0008] The color value on the test plate corresponding to the reference line is the reference color value, and the reference line is the dividing line between the area covered by the paint to be tested and the area not covered by the paint to be tested on the black and white grid test paper. The film thickness plate and the test plate both have a test area, and the test area is located on the side of the reference line away from the spraying trajectory. In the test area of ​​the test plate, multiple color value measurement points are taken along a second direction perpendicular to the first direction, and the color difference value between each color value measurement point and the reference color value is measured respectively. Based on the color difference value and the preset color difference value, the engineering hiding power line extending along the first direction is determined to obtain the engineering hiding power film thickness.

[0009] In an exemplary embodiment, the film thickness of the paint to be measured on the reference line of the film thickness plate is the black and white hiding film thickness.

[0010] In an exemplary embodiment, based on the color difference value and the preset color difference value, determining the engineering hiding power line extending along the first direction to obtain the engineering hiding power film thickness includes:

[0011] When the color difference between the color value measurement point and the reference color value is greater than the preset color difference value, taking the color value measurement point on the test plate along the second direction toward the reference line;

[0012] When the color difference between the color value measurement point and the reference color value is less than the preset color difference value, taking the color value measurement point on the test plate along the second direction away from the reference line;

[0013] When the color difference between the color value measurement point and the reference color value is equal to the preset color difference value, the straight line between the film thickness plate and the test plate passing through the color value measurement point in the first direction is the engineering hiding power line, and the film thickness of the paint to be tested on the film thickness plate on the engineering hiding power line is the engineering hiding power film thickness.

[0014] In an exemplary embodiment, a long strip of black and white grid test paper extending along the second direction is provided on the film thickness plate, the length of the black and white grid test paper in the second direction is greater than or equal to the length of the film thickness plate in the second direction, and the width of the black and white grid test paper in the first direction is less than the width of the film thickness plate in the first direction.

[0015] In an exemplary embodiment, before spraying the test plate, the film thickness plate and the black and white grid test paper with colored paint, the process includes:

[0016] The test plate is subjected to a preparation process before being sprayed with color paint, wherein the preparation process includes spraying a mid-coat paint.

[0017] In an exemplary embodiment, after stopping spraying and before taking a plurality of color value measurement points in the test area of ​​the test plate, the method includes:

[0018] The test plate is subjected to a finishing process after being sprayed with color paint, wherein the finishing process includes spraying with clear varnish and drying.

[0019] Dry the film thickness plate and the black and white grid test paper.

[0020] In an exemplary embodiment, the test plate and the film thickness plate are both rectangular, the width directions of the film thickness plate and the test plate extend along the first direction, and the length directions of the film thickness plate and the test plate extend along the second direction.

[0021] In an exemplary embodiment, the spraying trajectory coincides with a center line of the film thickness plate, and the center line extends along the first direction.

[0022] In an exemplary embodiment, the film thickness plate is equal in length to the test plate.

[0023] In an exemplary embodiment, the length of each grid of the black and white grid test paper in the length direction of the film thickness plate is 1 cm to 2.5 cm.

[0024] In an exemplary embodiment, the test plate and the film thickness plate are automatically sprayed by a rotary cup or a spray gun.

[0025] As described above, the method for measuring the hiding power of paint of the present invention has the following beneficial effects:

[0026] By spraying the film thickness plate and the test plate in the first direction, the paint to be tested on the film thickness plate and the test plate can have a uniformly varying film thickness in the second direction, and more accurate film thickness data can be obtained when determining the engineering hiding power of the paint. At the same time, compared with the traditional method, the method for determining the hiding power of the paint is simpler to operate and more efficient, and has good industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown is a schematic diagram of the arrangement positions of a film thickness plate, black and white grid test paper and a test plate according to an embodiment of the present invention.

[0028] Figure 2 Shown is a schematic flow chart of a method for measuring the hiding power of a paint according to an embodiment of the present invention.

[0029] Figure 3 Shown is a schematic diagram of the change in paint film thickness during spraying of an embodiment of the present invention.

[0030] Explanation of symbols: 1. Film thickness plate; 2. Black and white grid test paper; 3. Test plate; 4. Engineering hiding power line; 5. Baseline; 6. Spraying track; 7. Test area. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] See also Figures 1 to 3 It should be noted that the diagrams provided in the present embodiment only illustrate the basic concept of the present invention in a schematic manner, so the diagrams only show the components related to the present invention rather than drawing according to the number, shape and size of the components in actual implementation. The type, quantity and proportion of each component in actual implementation can be changed at will, and the component layout type may also be more complicated. The structure, proportion, size, etc. shown in the drawings attached to this specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions that the present invention can be implemented, so they have no technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effect and purpose that the present invention can produce. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of the relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0033] like Figure 1 and Figure 2 As shown, the present invention provides a method for measuring the hiding power of a paint, comprising:

[0034] Step S110: spraying the paint to be tested on the test plate 3, the film thickness plate 1 and the black and white grid test paper 2 along the first direction, wherein the test plate 3, the film thickness plate 1 and the black and white grid test paper 2 are all located on the spraying track 6 of the paint to be tested.

[0035] In an exemplary embodiment, the test plate 3 and the film thickness plate 1 are both rectangular, the width directions of the film thickness plate 1 and the test plate 3 are both extended in the first direction, and the length directions of the film thickness plate 1 and the test plate 3 are both extended in the second direction. The film thickness plate 1 is provided with a long black and white grid test paper 2 extending in the second direction, the length of the black and white grid test paper 2 in the second direction is greater than or equal to the length of the film thickness plate 1 in the second direction, and the width of the black and white grid test paper 2 in the first direction is less than the width of the film thickness plate 1 in the first direction, and the black and white grid test paper 2 has at least one column of black grids and one column of white grids in the first direction. The rectangular test plate 3 and the film thickness plate 1 have regular shapes, which are convenient for production, and are also convenient for finding the corresponding positions between the test plate 3 and the film thickness plate 1, so as to determine the black and white grid hiding power film thickness and the engineering hiding power film thickness. It should be noted here that the line connecting the "corresponding positions" of the test plate 3 and the film thickness plate 1 in the above text extends in the first direction. The shapes of the test plate 3 and the film thickness plate 1 can be adjusted according to the test needs. In an exemplary embodiment, the black-and-white grid test paper 2 is pasted on the film thickness plate 1. In another exemplary embodiment, the black-and-white grid test paper 2 is pinned to the film thickness plate 1 using a thumbtack. By placing the black-and-white grid test paper 2 on the film thickness plate 1, the placement pieces for placing the black-and-white grid test paper 2 can be reduced, the test steps can be simplified, and it is convenient to correspond the covering conditions on the black-and-white grid test paper 2 to the film thickness plate 1 and the test plate 3. The way in which the black-and-white grid test paper 2 is placed on the film thickness plate 1 can be adjusted according to specific test requirements.

[0036] In an exemplary embodiment, the material of the test plate 3 is a steel plate, a galvanized plate or an aluminum plate that has been electrophoresed. The material of the test plate 3 should be the same as that of the painted vehicle and electrophoresed to present a real effect close to the actual spraying scene.

[0037] Step S120: During a single spraying operation, the spraying is performed by unidirectional movement along the spraying track 6. After the single spraying operation is completed, the black and white grid test paper 2 is observed. If the black and white grid test paper 2 is located in the covering area on the spraying track 6 and includes at least one complete black grid and one complete white grid, the spraying is stopped. Otherwise, the spraying is continued.

[0038] It should be noted that the above-mentioned "masked area" is the area where the black and white grid background color cannot be seen, and the spraying amount is uniform in each spraying operation.

[0039] In an exemplary embodiment, the black-and-white grid test paper 2 has at least one black grid and one white grid along the first direction.

[0040] In an exemplary embodiment, the length of each grid of the black and white grid test paper 2 in the length direction of the film thickness plate 1 is 1cm to 2.5cm. The length of each grid of the black and white grid test paper 2 in the length direction of the film thickness plate 1 can be adjusted according to the actual test requirements. The length of the black and white grid in the black and white grid test paper will affect the amount of the paint to be tested sprayed during the test. By spraying the paint to be tested on the black and white grid test paper 2 for many times, after each spraying of the paint to be tested, the thickness of the paint to be tested accumulated on the black and white grid will become thicker, and the covering degree of the black and white grid will be enhanced. When the black and white grid on the black and white grid test paper 6 is sprayed until it is invisible, the dividing line between the black and white grid covered area by the paint to be tested and the area not covered by the paint to be tested can be obtained. The above-mentioned dividing line is the reference line 6. By measuring the thickness of the paint to be tested on the reference line 6, the black and white hiding power of the paint to be tested can be determined, and the reference color value is measured on the reference line 6 of the test plate 3.

[0041] In an exemplary embodiment, before spraying the test plate 3, the film thickness plate 1 and the black and white grid test paper 2 with the paint to be tested, step S210 is included.

[0042] Step S210: Perform a preparatory process before spraying the color paint on the test plate 3, the preparatory process including spraying the intermediate paint. The above preparatory process should be the same as the preparatory process in the color paint spraying process in the actual spraying scenario.

[0043] It should be noted here that Figure 3 In the figure, the ordinate is the thickness of the paint film after spraying, and the abscissa is the distance between the measuring point in the spraying area and the spraying track 6 in the second direction. The second direction is perpendicular to the first direction, that is, Figure 3 It is displayed as the film thickness value of different measuring points in the spraying area in the second direction. The horizontal axis has positive and negative values, that is, with the spraying track 6 as the boundary, one side of the spraying track 6 is positive, and the other side of the spraying track 6 is negative. The maximum film thickness at the spraying track 6 is the peak film thickness point. The spraying track 6 mentioned above is the straight line formed by the peak film thickness point when the color paint to be tested is sprayed. Figure 3 It can be seen that the closer the distance to the peak film thickness point is, the thicker the film thickness of the paint to be tested is, and the farther the distance to the peak film thickness point is, the thinner the film thickness of the paint to be tested is. It can be seen that after the test plate 3 and the film thickness plate 1 are sprayed multiple times, since the spraying track 6 extends along the first direction, in the second direction, the closer the film thickness of the paint to be tested is to the spraying track 6 on the test plate 3 and the film thickness plate 1, the thicker the film thickness of the paint to be tested is, and the farther the film thickness of the paint to be tested is from the spraying track 6, the thinner the film thickness of the paint to be tested is. Therefore, the film thickness of the paint to be tested at any two points on the test plate 3 and the film thickness plate 1 along the first direction is the same.

[0044] It should be noted that the test plate 3 needs to be sprayed according to the paint spraying process of the actual spraying scenario. The color value on the test plate 3 is more consistent with the spraying effect of the actual spraying area of ​​the vehicle, so the test plate 3 is used to measure the color value; because the film thickness plate 1 only sprays the paint to be tested, the film thickness of the paint to be tested can be accurately measured on the film thickness plate 1. By measuring the color difference value on the test plate 3 and measuring the film thickness at the corresponding position of the film thickness plate 1, the engineering hiding film thickness of the paint to be tested corresponding to the actual spraying scenario can be obtained to determine its engineering hiding power. The actual spraying scenario includes spraying methods, such as air spraying or electrostatic spraying, and different spraying methods will produce different measurement results. In an exemplary embodiment, the test plate 3 and the film thickness plate 1 are automatically sprayed by a rotary cup or a spray gun, wherein, when using a rotary cup for spraying, the spray mist width can be adjusted by adjusting the forming air volume. When measuring the engineering hiding film thickness, the size of the mist width of the paint to be tested will affect the measurement accuracy. Please refer to Figure 3 , the vertical axis is the thickness of the paint to be tested after spraying, the horizontal axis is the distance between the measuring point in the second direction in the spraying area and the spraying track 6, the second direction is perpendicular to the first direction, the solid line shows the film thickness change of narrow mist spraying, and the dotted line shows the film thickness change of wide mist spraying. Figure 3 It can be seen from the figure that when performing narrow mist spraying, the film thickness variation rate along the second direction in the spraying area is relatively large; Figure 3 It can be seen that when a wide mist width is sprayed, the rate of change of the film thickness in the spraying area along the second direction is small. Therefore, when a wide mist width is used to measure the hiding power of the paint, the resolution is higher and the obtained film thickness value is more accurate. However, when a wide mist width is used during spraying, the length required for the test plate 3 and the film thickness plate 1 in the second direction is longer than that of a narrow mist width. Therefore, when selecting the size of the spray mist width, it is necessary to adjust it according to the accuracy and cost of the measurement.

[0045] From the above, it can be understood that, since the spraying track 6 extends along the first direction, the boundary between the area of ​​the black and white grid test paper covered by the paint to be tested and the area not covered by the paint to be tested should also extend along the first direction.

[0046] In an exemplary embodiment, the moment when the black and white grids of the black and white grid test paper 2 located on the spraying track 6 are covered is determined by visual inspection or equipment, and spraying is stopped. At the same time, the areas covered by the paint to be tested and the areas not covered by the paint to be tested on the black and white grids are determined by visual inspection or equipment to determine the reference line 5. The film thickness of the paint to be tested on the film thickness plate 1 on the reference line 5 is the black and white hiding power film thickness. It should be noted that the reference line 5 is an artificially designed dividing line, which is affected by the subjectivity of the visual observer and the resolution of the equipment. The definition of the reference line 5 is that the black and white grids near one side of the reference line 5 are covered by the paint to be tested, and the black and white grids near the other side of the reference line 5 are not covered by the paint to be tested, that is, the black and white grids on the reference line 5 are just covered by the paint to be tested, and the reference line 5 indicates the minimum film thickness of the paint to be tested that can cover the black and white grids.

[0047] In an exemplary embodiment, the film thickness plate 1 and the test plate 3 are rectangular, the length directions of the film thickness plate 1 and the test plate 3 extend along the second direction, and are arranged side by side along the first direction. The spraying trajectory 6 coincides with the center line of the film thickness plate 1, and the center line extends along the first direction. The above-mentioned spraying method can make the film thickness of the color paint to be tested on both sides of the spraying trajectory 6 of the film thickness plate 1 and the test plate 3 show a trend of changing from thick to thin in the second direction. In this way, after one spraying, a group of black and white hiding film thickness and engineering hiding film thickness can be obtained on both sides of the spraying trajectory 6 to increase the confidence of the measurement.

[0048] Step S130: the color value of the test plate 3 corresponding to the reference line 5 is the reference color value, the reference line 5 is the dividing line between the area covered by the paint to be tested and the area not covered by the paint to be tested on the black and white grid test paper 6, the film thickness plate 1 and the test plate 3 both have a test area, the test area is located on the side of the reference line 5 away from the spraying trajectory 6, a plurality of color value measurement points are taken in the test area of ​​the test plate 3 along a second direction perpendicular to the first direction, and the color difference value between each color value measurement point and the reference color value is measured respectively, based on the color difference value and the preset color difference value, the engineering hiding power line 4 extending along the first direction is determined to obtain the engineering hiding power film thickness.

[0049] In an exemplary embodiment, after stopping spraying and before taking a plurality of color value measurement points along the second direction in the test area 7 of the test plate 3, step S310 is included.

[0050] Step S310: Finishing process after color paint spraying on the test board 3, the finishing process includes varnish spraying and drying; drying the film thickness plate 1 and the black and white grid test paper 2. The above preparation process should be the same as the finishing process in the color paint spraying process in the actual spraying scenario.

[0051] It should be noted that the black and white grid hiding film thickness is used to characterize the hiding ability of the tested paint on the black and white grid, that is, the thinner the black and white grid hiding film thickness, the better the black and white grid hiding power; the engineering hiding film thickness is used to characterize the hiding ability of the tested paint corresponding to the actual spraying scenario, that is, the thinner the engineering hiding film thickness, the better the engineering hiding power.

[0052] In an exemplary embodiment, based on the color difference value and the preset color difference value, determining the engineering hiding power line 4 extending along the first direction to obtain the engineering hiding power film thickness includes steps S410, S420 and S430:

[0053] Step S410 : when the color difference between the color value measurement point and the reference color value is greater than the preset color difference value, a color value measurement point is taken on the test plate 3 along the second direction toward the reference line 5 .

[0054] Step S420 : when the color difference between the color value measurement point and the reference color value is less than the preset color difference value, a color value measurement point is taken on the test plate 3 along the second direction away from the reference line 5 .

[0055] Step S430: When the color difference between the color value measurement point and the reference color value is equal to the preset color difference value, the straight line passing through the color value measurement point in the first direction between the film thickness plate 1 and the test plate 3 is the engineering hiding power line 4, and the film thickness of the paint to be tested on the film thickness plate 1 on the engineering hiding power line 4 is the engineering hiding power film thickness.

[0056] In an exemplary embodiment, the color difference value is measured by a colorimeter, and the film thickness of the color paint to be tested on the film thickness plate 1 is measured by an electromagnetic film thickness measuring instrument. The types of the colorimeter and the film thickness measuring instrument can be adjusted according to the needs of use.

[0057] It should be noted that the preset color difference value is a universal value, which is generally set to 1.4 or 1.7.

[0058] In summary, by spraying the film thickness plate 1 and the test plate 3 along the first direction, the paint to be tested on the film thickness plate 1 and the test plate 3 can have a uniformly varying film thickness in the second direction, and more accurate film thickness data can be obtained when determining the engineering hiding power of the paint. At the same time, compared with the traditional method, the method for determining the hiding power of the paint is simpler to operate and more efficient, and has good industrial promotion value.

[0059] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for measuring the hiding power of a paint, characterized in that: include: Spraying the paint to be tested on the test plate, the film thickness plate and the black and white grid test paper along a first direction, wherein the test plate, the film thickness plate and the black and white grid test paper are all located on the spraying track of the paint to be tested; During a single spraying operation, the spraying is performed by unidirectionally moving along the spraying track. After the single spraying operation is completed, the black and white grid test paper is observed. If the black and white grid test paper is located in a covered area on the spraying track and includes at least one complete black grid and one complete white grid, the spraying is stopped. Otherwise, the spraying is continued. The color value on the test plate corresponding to the reference line is the reference color value, and the reference line is the dividing line between the area covered by the paint to be tested and the area not covered by the paint to be tested on the black and white grid test paper. The film thickness plate and the test plate both have a test area, and the test area is located on the side of the reference line away from the spraying trajectory. In the test area of ​​the test plate, multiple color value measurement points are taken along a second direction perpendicular to the first direction, and the color difference value between each color value measurement point and the reference color value is measured respectively. Based on the color difference value and the preset color difference value, the engineering hiding power line extending along the first direction is determined to obtain the engineering hiding power film thickness.

2. The method for measuring the hiding power of a paint according to claim 1, wherein: The film thickness of the color paint to be measured on the reference line of the film thickness plate is the black and white hiding film thickness.

3. The method for measuring the hiding power of a paint according to claim 1, characterized in that: Based on the color difference value and the preset color difference value, determining the engineering hiding power line extending along the first direction to obtain the engineering hiding power film thickness includes: When the color difference between the color value measurement point and the reference color value is greater than the preset color difference value, taking the color value measurement point on the test plate along the second direction toward the reference line; When the color difference between the color value measurement point and the reference color value is less than the preset color difference value, taking the color value measurement point on the test plate along the second direction away from the reference line; When the color difference between the color value measurement point and the reference color value is equal to the preset color difference value, the straight line between the film thickness plate and the test plate passing through the color value measurement point in the first direction is the engineering hiding power line, and the film thickness of the paint to be tested on the film thickness plate on the engineering hiding power line is the engineering hiding power film thickness.

4. The method for measuring the hiding power of a paint according to claim 1, wherein: The film thickness plate is provided with a long strip of black and white grid test paper extending along the second direction, the length of the black and white grid test paper in the second direction is greater than or equal to the length of the film thickness plate in the second direction, and the width of the black and white grid test paper in the first direction is less than the width of the film thickness plate in the first direction.

5. The method for measuring the hiding power of a paint according to claim 1, characterized in that: Before spraying the test panels, film thickness panels and black and white grid test papers, the following steps should be performed: The test plate is subjected to a preparation process before being sprayed with color paint, wherein the preparation process includes spraying a mid-coat paint.

6. The method for measuring the hiding power of a paint according to claim 1, characterized in that: After stopping spraying and before taking a plurality of color value measurement points along the second direction in the test plate, the method comprises: Performing a finishing process on the test plate after spraying the color paint, the finishing process including varnish spraying and drying; Dry the film thickness plate and the black and white grid test paper.

7. The method for measuring the hiding power of a paint according to any one of claims 1 to 6, characterized in that: The test plate and the film thickness plate are both rectangular, the width directions of the film thickness plate and the test plate extend along the first direction, and the length directions of the film thickness plate and the test plate extend along the second direction.

8. The method for measuring the hiding power of a paint according to claim 7, wherein: The spraying trajectory coincides with a center line of the film thickness plate, and the center line extends along the first direction.

9. The method for measuring the hiding power of a paint according to any one of claims 1 to 6, characterized in that: The length of each grid of the black and white grid test paper in the length direction of the film thickness plate is 1 cm to 2.5 cm.

10. The method for measuring the hiding power of a paint according to any one of claims 1 to 6, characterized in that: The test plate and the film thickness plate are automatically sprayed by a rotary cup or a spray gun.

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