CD four-color screen printing overview

The screen printing of optical discs is performed on a dedicated automatic multicolor disc screen printing machine. The ink is a UV (ultraviolet) curing ink. Therefore, there are multiple stations for special optical printers. For example, a six-color printer has 32 work stations and is enclosed. Each station has 80 W/ UV (ultraviolet light) curing devices (UV lamps and light reflectors) with cm to 120 W/cm are used. When the ink is silk-screened on the disc, the ink is then dried by UV light. Therefore, special printing optical disc screen printing machine, once the pre-press debugging can be fully automatic printing, printing 1000 ~ 3600 per hour or more.

1) Projects that need to be debugged before screen printing for special optical discs include:

a.Adjust the distance between the four printing color stencils and the optical disc (called the static grid distance) and achieve the same. The grid distance is controlled at the value of 1 to 2 discs; in addition, the retina must be firmly fixed and stable. Otherwise, after the screen printing will produce a trace consistent with the squeegee blade at a certain position on the disc;

b. Adjust the suitable squeegee pressure of the squeegee and the squeegee angle of the squeegee. At the same time, the contact state of the ink squeegee and the stencil should be adjusted so as to ensure the uniform ink on the stencil and the squeegee process. .

C. According to the requirements of each printing color, the hardness of the squeegee can be changed from 80 to 90 degrees. For example, in VCD and CD discs, the printing of color blocks or bottoming white ink can be selected with about 80” right-angle squeegee, and the same template can be used with more than 140 mesh/cm～180 mesh/cmPW, PET screen, and the resolution is high. Dot printing with a 90° hardness squeegee printing, no matter what, the edge of the squeegee must be strictly flat, straight, smooth, otherwise, uneven, curved, blunt, hair can reflect the printed ink marks scratches or Graphically colors phase deviations.

2) To prevent moiré, the angle between the screen angle and the dot line should be reasonably matched. The color of the four-color positive negative film is generally Y- 0°, C- 15°, M-75°, and K-45°. It should also be properly adjusted according to the characteristics of the printed graphics and texts: for example, mainly people, mainly Highlight the character's face, so Y-0°”, C—15°, M-45°, and K-75° arrange Y and M by 45°, which highlights the ruddyness of the face; When the theme is Y - 0 °, K - 15 °, C - 45 °, M - 75 °, the C is set to 45 ° to make outdoor scenery better, the picture is more realistic.

3) The color sequence of CD-ROM screen printing is commonly used CM-Y-K.

4) Screen printing ink:

a. UV ink color density adjustment:

The better ink color purity is high, transparency is good, and has good thixotropic properties and moderate UV curing. In general, the ink can be used directly without adjustment. However, due to the four-color UV ink on the disc, due to the large number of brands on the market, the quality varies, and four-color overprintable special ink, the optical disc factory still needs to color, therefore, the need for the ink viscosity color density, concentration Even the special color is to be adjusted or the dots on the disc will be affected by the difference in the ink's color density and viscosity, and the printing effect will be biased. For example, Y and M in the three primary colors should be red (R) if they are superimposed in equal proportions, no matter who overprints them. However, due to the ink's own density, darkness, and brand differences, it sometimes appears as reddish or yellowish red. Therefore, we must adjust the color density of the inks appropriately. Methods are: You can change the printing color sequence test printing, or when the color sequence is fixed, when changing the order of the printing color, then you should change the color density of the overprint ink, so that the color density decreases, the transparency of the ink increases. The method of changing the color density of the ink is to add the gloss oil (colorless ink) of this series of inks to the source ink. The amount of varnish added is determined by the color density of the color ink. In summary, when adjusting, the varnish is added to the color ink while stirring, and the amount of varnish that has just been added to the color ink but has not changed the original color is added. Stop immediately and you can use it.

b. The ink particles should be fine and uniform. The pigment particle size should be 1/3 to 1/4 of the mesh opening. Therefore, the ink used must be able to pass through the mesh mesh used well when the color particles are used. When the fineness is uneven or does not match with the screen, the color difference will be produced at the beginning of printing and after printing to a certain number of discs, which is common in the light stack printing factory.

C. Requirements for UV screen printing inks:

UV inks used in CD, VCD discs, in addition to the above requirements, the ink should also have good adhesion with PC (polycarbonate) materials, if used on DVD discs, when dealing with writing/reading, the laser deflects the beam The tilt angle (cannot be greater than ±0.8° in the direction of radiation or not more than 0.3° in the direction of the tangent) is less affected. Therefore, the shrinkage of the ink and ink after drying is small; therefore, the flatness of the optical disk can be guaranteed: Simultaneous printing The ink layer on the DVD disc is required to be thin and uniform, so as to minimize the influence of the IR component in the UV on the flatness of the DVD when the UV is rapidly cured. To print a thin, even layer of ink on a disc, the ink must have a high color density and the thickness of the photosensitive layer on the stencil should be controlled.

d. Basic conditions for photo-curing of UV inks for optical discs:

Fast UV curing under low power, especially for UV ink on DVD, usually about 1 second for 80W C power. If UV ink requires >80W/cm for UV irradiation on CD printer Prolonged time can not reach the bottom of the ink layer curing, while extending the curing duration even if cured, but the UV exposure of the disc at the same time, IR in the UV also radiates on the disc, which is subject to optical discs, especially DVD performance constraints;

Because UV inks are required to be cured at low power, the printing environment, especially over the stencil, should avoid the direct exposure of white “harmful” light, resulting in a chronic photocross-linking reaction of the ink on the reticular film, making the beginning of printing the graphic. , Hue deviation in the end, the final difficulty in ink;

The conditions of the printing environment: UV light-cured inks are subject to changes in temperature, and the ink's viscosity also changes. At high temperatures, the viscosity of the ink drops, and the printed ink layer is thinned and the hue is shifted. At low temperatures, the viscosity of the ink is increased and the printing ink is thick and dark. Therefore, when printing UV inks, the temperature of the printing environment should be controlled from 18 to 25, and about 23aC is appropriate. The relative humidity is about 65%. When the humidity is high, the ink will increase in viscosity and gel, so the printing environment is warm and humid. When stable, the viscosity of the UV ink is also stable, the viscosity is stable, the thixotropy of the ink is relatively stable, the printing adaptability of the ink is good, the ink layer is suitable, and the printing quality is easily ensured. Therefore, the fine graphic color UV ink Printing must provide constant temperature and humidity in the printing environment.

At present, UV screen printing inks used on optical discs include domestic Fuji ink, French Dolby ink, Selenium disc series ink and German RVCO (Digo), etc., which are printed on CD-R, CD, VCD and DVD respectively. Special silk/offset UV ink meets requirements.

Fourth, disc offset (flat) printing:

l. Compared with screen printing:

Offset printing is an indirect transfer method. It transfers the images on the blanket (rubber cylinder) to the disc. Therefore, the pressure of the offset printed on the disc is small. Therefore, the deformation of the graphic and network dots is small, and the offset is offset at the same time. The printing plate is a PS plate, and the PS plate has a finer structure, so the resolution of the produced graphic is high. It can print >80L/cm, and because the offset printing dots are small, the hue reappears well. High sharpness, strong texture, thin offset ink (2 ~ 3U or so). Therefore, offset printing speed and ink curing speed are faster. The UV ink used for offset printing has a high color density and is relatively larger than the screen-printed UV ink. Therefore, it is desirable that the coloring material in the UV ink be higher in light transmittance. Given the above characteristics of offset printing, offset printing is more suitable for printing CDs, VCDs, and DVDs than screen printing.

2. The uniqueness of UV offset printing discs:

a. thin ink layer: generally about 2 micrometers of flying, so the dry and solid ink shrinkage has little effect on the flatness of the disc, especially the printing of DVD discs.

b. The printing template is composed of fine PS plates and so on, so the picture and color dots are fine, the resolution is good, the resolution is high, the texture is strong, and the color reproduction of the graphic and text is good.

c. The number of wires can be higher than screen printing, and one can print more than eight m color graphics for M80L.

d. Compared to other printing methods, offset printing has a low printing pressure and is therefore suitable for printing on DVD discs. Because the thickness of a DVD disc is equivalent to the construction of two 0.6mm CD discs, the flatness is high except that the thickness tolerance is small (CD is 200 microns and DVD is about 100 microns). Therefore, the offset pressure of offset printing is small. , the impact of disc distortion in printing?