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Screen printing plate making process (IX)

B. color light additive method. The method by which two or more colored lights are mixed to produce another colored light is called colored light additive method, also known as colored light additive mixing method and additive method. The experimental results show that the following color light can be obtained by mixing the two colors equally: red light + green light = yellow light

red light + blue violet light = magenta light

blue purple light + green light = blue light

when the three primary colors are mixed in equal quantities, white light can be obtained, as shown in the figure

the experiment also tells us that if the three primary colors red, green, blue and purple are added with green, magenta and yellow respectively, white light can also be obtained

red light + blue light = white light

green light + magenta light = white light

blue purple light + yellow light = white light

when the two colored lights are added to get white light, we call the two colored lights complementary to each other, that is, red ----- Jinan experimental machine factory bolt changes the experimental machine light and blue light complementary to each other; Green light and magenta light complement each other; Blue violet light and yellow light complement each other. Cyan, magenta and yellow are called complementary colors of red, green, blue and purple, as shown in the figure

c. pigment subtraction method. Method when subtracting a certain color light from white light, the complementary color light of the reduced color light can be obtained, such as:

white light red light = blue light

white green magenta

white light - blue violet light = yellow light,

cyan, magenta and yellow are also called subtractive colors

the experimental results show that when white light irradiates the yellow filter, the yellow filter absorbs the blue violet light in the white light and passes through red light and green light. The result of the addition of red light and green light gives us the feeling of yellow. When white light irradiates the magenta filter, the green light in the white light is absorbed and passes through red light and blue violet light. The result of the addition of red light and blue violet light gives us a sense of concreteness. 2. The sense of stretching experiment is magenta

when white light irradiates the green filter, the red light in the white light is absorbed and passes through green light and blue violet light. The result of the addition of green light and blue violet light gives us the feeling of green

if the white light is exposed to the Yellow + magenta color filter, the green and blue violet light in the white light can be absorbed by the filter respectively, and then red can be obtained. When white light irradiates the magenta + cyan color filter, the red and green light in the white light are absorbed by the filter respectively, and blue purple can be obtained. When white light irradiates the green + yellow color filter, the red, blue and violet light in white is absorbed by the filter respectively, and green can be obtained. When sunlight shines on the three color filters of Yellow + magenta + cyan, the red, green, blue and violet light are absorbed, and no light can pass through, so it becomes ink

from the above experiments, we can know that different colors can be obtained by superimposing magenta, yellow and green subtractive pigments in different proportions, so we call magenta, yellow and green as the three primary colors of pigments. This method of synthesizing colors by subtraction and addition is the pigment subtraction method, as shown in the figure

chromatic light addition method and pigment subtraction method are two opposite concepts. The main difference is that additive method refers to the synthesis method of adding the three primary colors of light (red, green, blue and violet) to white light or adding the two color lights to obtain a new color light that is much brighter than the original color light. Subtractive method is a synthetic method that adds the three primary colors (yellow, magenta and cyan) of pigments to black, or adds any two colors to obtain a new color much darker than the original color

in the additive method, the complementary colored light is added into white light; In the subtraction method, the complementary colors are added together, which is approximately black

there is a complementary relationship between the three primary colors of light and pigments. The hue of the pigment trichromatic mirror is the hue presented by subtracting one of the trichromatic lights from the white light. Therefore, the hue of the blue purple, green and red filters can be used to check the photographic color separation, and the color separation negatives of yellow, magenta and blue can be obtained, and then reproduced or copied into positive films

② color separation principle. Color separation is to irradiate the continuously adjusted reflection or transmission draft with white light, reflect or transmit the color light with different strengths to the color filter, and the color light complementary to the color of the filter is absorbed by the filter, while other color light passes through the filter to make the negative sensitive, and then develop and fix to obtain a color separation negative

the function of the color filter is to make the same natural color light as the color filter pass through and absorb the other two kinds of color light in the three primary colors of color light. In this way, only one kind of color light is sensitive on the photosensitive sheet, while the other two kinds of color light are absorbed and cannot be sensitive. The two colors that cannot be sensitized are the complementary colors of the hue of the color filter, that is, one of the three primary colors of the pigment, so as to obtain the required graduation negative, as shown in the figure