Flexographic printing method

Abstract

The invention discloses a flexographic printing method which comprises the following steps: S1, drawing an image, adjusting the resolution of the image, calculating the number of makeup, and converting the image into a positive and negative image film; s2, manufacturing a printing plate based on the positive and negative image films; s3, plate pasting is conducted on the printing plate, and proofing is conducted; and S4, the printing material is printed, and a printed product is segmented. The method has the beneficial effects that the printing precision, the color rendition degree and the production efficiency can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of printing, and in particular to a flexographic printing method. Background Art

[0002] Flexographic printing is a printing method that uses a flexible plate and transfers ink through an anilox roller. As a common printing method, flexographic printing is widely used in packaging, labeling and other fields, and the flexographic printing market is showing a rapid development trend.

[0003] In the existing technology, the flexographic printing method still has certain limitations in terms of printing accuracy, color reproduction, and production efficiency. For example, the lack of accurate algorithms for the conversion of image resolution and color mode leads to poor clarity and color accuracy of printed products, thus affecting the color reproduction of printed products; the lack of scientific tension control makes it difficult to ensure the accuracy of printing registration and sample quality; the lack of systematic adjustment of parameters such as pressure and ink supply affects the consistency of printed products. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present application proposes a flexographic printing method that can improve printing accuracy, color reproduction and production efficiency.

[0005] The following is a technical solution of the present invention, a flexographic printing method, comprising the following steps:

[0006] S1, draw the image and adjust the image resolution, calculate the number of impositions, and convert the image into positive negative film;

[0007] S2, making printing plates based on positive negative film;

[0008] S3, mount the printing plate and make proofs;

[0009] S4. Print the printing material and divide the printed matter.

[0010] As a preferred solution of the present invention, in S1, the image resolution is adjusted, and the expression is as follows:

[0011]

[0012]

[0013] In the above formula, W 原 is the original image width, H 原 is the original image height, R 原 is the original image resolution, R 目 is the target resolution.

[0014] As a preferred solution of the present invention, in S1, the number of impositions is calculated, and the expression is as follows:

[0015]

[0016] In the above formula, N is the number of panels, S is 幅面 is the printing equipment format area, S 产品 is the product area, k 出血位 Bleeding site ratio.

[0017] As a preferred solution of the present invention, S2 comprises the following steps:

[0018] S21, placing the photosensitive resin plate in a plate exposure machine, laminating it with the positive negative film, and performing back exposure;

[0019] S22, after the back exposure is completed, the main exposure is performed;

[0020] S23, after the main exposure is completed, the plate is placed in a developer and rinsed with a developer;

[0021] S24, removing the solvent by hot air drying or vacuum drying to remove impurities remaining on the plate surface;

[0022] S25, post-exposing the plate.

[0023] As a preferred solution of the present invention, the energy range of the back exposure is 50-150mJ / cm 2 , the energy range of the main exposure is 200-500mJ / cm 2 , the energy range of post-exposure is 50-100mJ / cm 2 .

[0024] As a preferred solution of the present invention, in S23, the developer is rinsed based on the developer concentration, the rinse time and the rinse temperature;

[0025] The developer concentration expression is as follows:

[0026] C 浓 =C0×K m ×K d

[0027] In the above formula, C 浓 is the developer concentration, C0 is the base developer concentration, K m is the plate type correction factor, K d is the image and text complexity correction coefficient;

[0028] The flushing time expression is as follows:

[0029] t 冲 =t0×(1+a×(C 浓 -C 标准 )+b×(DD 标准))

[0030] In the above formula, t 冲 is the flushing time, t0 is the recommended flushing time, a is the concentration influence coefficient, C 浓 is the developer concentration, C 标准 is the standard developer concentration, b is the thickness influence coefficient, D is the plate thickness, D 标准 It is the standard plate thickness;

[0031] The flushing temperature expression is as follows:

[0032]

[0033] In the above formula, T 冲 is the flushing temperature, T0 is the recommended flushing temperature, K en is the ambient temperature correction factor, K eq is the equipment performance correction factor, t 冲 is the flushing time, t 标准 This is the standard flushing time.

[0034] As a preferred solution of the present invention, in S24, the hot air drying temperature is 50-80°C and the time is 10-30 minutes.

[0035] As a preferred solution of the present invention, in S3, the printing plate is pasted, and the expression of the printing plate pasting tension is as follows:

[0036]

[0037] In the above formula, T 张 is the plate pasting tension, k1 is the viscosity coefficient of the double-sided tape or glue, L 印版 is the length of the printing plate, W 印版 is the printing plate width, S 接触 is the contact area.

[0038] As a preferred solution of the present invention, in S3, proofing is performed based on the pressure, proofing speed and proofing ink supply of the proofing device;

[0039] The pressure expression is as follows:

[0040]

[0041] In the above formula, P 压 is pressure, P0 is standard pressure, K m is the plate material coefficient, S 印版 is the printing plate area, K r is the roller surface roughness coefficient;

[0042] The proofing speed expression is as follows:

[0043] V打样 =V0×K i ×K y ×K s

[0044] In the above formula, V 打样 is the proofing speed, V0 is the basic proofing speed, K i K is the plate run coefficient, y is the ink drying speed coefficient, K s is the speed adaptability coefficient of the printing material;

[0045] The expression of proofing ink supply is as follows:

[0046]

[0047] In the above formula, Q 油墨 is the proofing ink supply, Q0 is the standard ink supply, C 覆盖 is the printing plate image coverage, K a is the ink absorption coefficient of the printing material, V 打样 is the proofing speed, K e is the ink transfer efficiency coefficient.

[0048] As a preferred solution of the present invention, in S4, the die-cutting knife cuts the printed matter according to the die-cutting pressure through the pressure device, and the die-cutting pressure is expressed as follows:

[0049] P 模切 =S 抗 ×L 刀 ×W 刀

[0050] In the above formula, P 模切 is the die cutting pressure, S 抗 is the shear strength of printed materials, L 刀 is the die cutting knife length, W 刀 The width of the die cutter.

[0051] Beneficial effects of the present invention:

[0052] 1. The present invention improves the clarity and material utilization of printed products by adopting precise resolution adjustment and imposition layout algorithm in the pre-press design and graphic processing stages;

[0053] 2. The plate making process is based on accurate exposure energy formula and precise parameter control of each step, which improves the quality and durability of the plate;

[0054] 3. The printing plate mounting and proofing process uses scientific tension control formulas and sample evaluation standards to ensure printing registration accuracy and sample quality;

[0055] 4. Systematically adjust the pressure during the printing process to improve the consistency of the printed product;

[0056] 5. Accurate calculation of die-cutting pressure in the post-printing process reduces product damage and improves production efficiency and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a flow chart of the flexographic printing method of the present invention;

[0058] Figure 2 A flow chart for making a printing plate for the flexographic printing method of the present invention; DETAILED DESCRIPTION

[0059] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0060] Example:

[0061] like Figure 1 and Figure 2 As shown, a flexographic printing method comprises the following steps:

[0062] S1, draw the image and adjust the image resolution, calculate the number of impositions, and convert the image into positive negative film;

[0063] S2, making printing plates based on positive negative film;

[0064] S3, mount the printing plate and make proofs;

[0065] S4. Print the printing material and divide the printed matter.

[0066] In step S1, the image is drawn and the image resolution is adjusted, the number of impositions is calculated, and the image is converted into a positive negative film.

[0067] Draw images based on the purpose of the printed material. After the image is drawn, adjust the image resolution based on the original image; enter text in the vector graphics software, select the appropriate font and then convert it to curve to prevent font loss; calculate the number of plate types based on the format of the printing equipment and the product area, so as to arrange the position of the image and text and improve material utilization.

[0068] Adjust the image resolution based on the original image. The expression is as follows:

[0069]

[0070] In the above formula, W 原 is the original image width, H 原 is the original image height, R 原 is the original image resolution, R 目 is the target resolution.

[0071] The number of impositions is calculated based on the format of the printing equipment and the product area. The expression is as follows:

[0072]

[0073] In the above formula, N is the number of panels, S is 幅面 is the printing equipment format area, S 产品 is the product area, k 出血位 Bleeding site ratio.

[0074] Convert the image color mode to CMYK mode, and use tools such as curves and levels to correct color balance, contrast, and brightness. If the original image color mode is RGB mode, convert the RGB mode to CMYK mode, and calculate the four channel values ​​of C, M, Y, and K. The expression is as follows:

[0075]

[0076] K=min(C′,M′,Y′)

[0077]

[0078]

[0079] In the above formula, R, G, B are the values ​​of the original image in RGB mode, and C, M, Y, K are the values ​​of the original image converted to CMYK mode.

[0080] The color-separated digital image information is exposed to the photosensitive film by a photosetter through a laser, and then processed by development and fixing to form a color-separated film, that is, a positive negative film.

[0081] S2. Make a printing plate based on positive negative film.

[0082] Place the photosensitive resin plate in the platemaking machine, attach it to the positive negative film, and perform back exposure first. The purpose of back exposure is to make the photosensitive resin at the bottom of the plate slightly polymerize, form a support layer of a certain thickness, and enhance the printing resistance of the printing plate. The energy calculation expression for back exposure is as follows:

[0083] E 背 =I 背 ×t 背

[0084] In the above formula, E 背is the back exposure energy, I 背 is the UV intensity during back exposure, t 背 is the back exposure time.

[0085] In this embodiment, the back exposure energy E 背 The energy range is 50-150mJ / cm2.

[0086] After the back exposure is completed, the main exposure is performed. At this time, the ultraviolet rays pass through the transparent part of the positive negative film, causing the photosensitive resin on the surface of the plate to undergo a full polymerization reaction, forming a cross-linked structure corresponding to the image. The energy calculation expression for the main exposure is as follows:

[0087] E 主 =I 主 ×t 主

[0088] In the above formula, E 主 is the main exposure energy, I 主 UV intensity during main exposure, t 主 Main exposure time.

[0089] In this embodiment, the main exposure energy E 主 The energy range is 200-500mJ / cm 2 .

[0090] After the main exposure is completed, the plate is placed in the developer and rinsed with developer. The developer dissolves the unexposed photosensitive resin, forming a relief image on the plate surface that is opposite to the positive negative film image. Parameters such as developer concentration, rinse time and rinse temperature are calculated and accurately controlled based on the parameters to ensure the development effect.

[0091] Calculate developer concentration C based on plate type and image complexity 浓 , the expression is as follows:

[0092] C 浓 =C0×K m ×K d

[0093] In the above formula, C 浓 is the developer concentration, C0 is the base developer concentration, K m is the plate type correction factor, K d is the image complexity correction factor.

[0094] In this embodiment, K m It is related to the photosensitive resin plate, and the value range is between 0.8-1.2; K d The value range is between 1-1.5.

[0095] Based on the developer concentration C浓 Calculate the flushing time t based on the plate thickness 冲 , the expression is as follows:

[0096] t 冲 =t0×(1+a×(C 浓 -C 标准 )+b×(DD 标准 ))

[0097] In the above formula, t 冲 is the flushing time, t0 is the recommended flushing time, a is the concentration influence coefficient, C 浓 is the developer concentration, C 标准 is the standard developer concentration, b is the thickness influence coefficient, D is the plate thickness, D 标准 is the standard plate thickness. The recommended washing time t0 is at the standard developer concentration C 标准 And standard plate thickness D 标准 The recommended washout time is provided by the plate manufacturer.

[0098] Based on the flushing time t 冲 Calculate the flushing temperature T based on environmental factors 冲 , the expression is as follows:

[0099]

[0100] In the above formula, T 冲 is the flushing temperature, T0 is the recommended flushing temperature, K en is the ambient temperature correction factor, K eq is the equipment performance correction factor, t 冲 is the flushing time, t 标准 is the standard washing time. The recommended washing temperature T0 is the recommended washing temperature under standard conditions, which is provided by the developer or plate manufacturer.

[0101] The plate material after development and washing contains a large amount of solvent, and the solvent is removed by hot air drying or vacuum drying to restore the plate material to normal hardness and dimensional stability. In this embodiment, the hot air drying temperature is 50-80° C. and the time is 10-30 minutes.

[0102] The dried plate is post-processed, such as using a special cleaning agent to remove impurities remaining on the plate surface to further improve the surface quality of the plate.

[0103] After the post-processing is completed, the plate is exposed to ultraviolet light for a short time again, which is called post-exposure. The role of post-exposure is to further improve the hardness and printing durability of the plate surface. The energy calculation expression for post-exposure is as follows:

[0104] E 后 =I后 ×t 后

[0105] In the above formula, E 后 is the post-exposure energy, I 后 is the ultraviolet intensity during post-exposure, t 后 is the post-exposure time.

[0106] In this embodiment, the post-exposure energy E 后 The energy range is 50-100mJ / cm 2 .

[0107] S3. Mount the printing plate and make proofs.

[0108] The prepared printing plate is accurately pasted to the printing cylinder with double-sided tape or special plate glue to ensure that the printing plate fits tightly to the cylinder without bubbles or wrinkles. Calculate and control the plate pasting tension to ensure the printing registration accuracy. The plate pasting tension T 张 The expression is as follows:

[0109]

[0110] In the above formula, T 张 is the plate pasting tension, k1 is the viscosity coefficient of the double-sided tape or glue, L 印版 is the length of the printing plate, W 印版 is the printing plate width, S 接触 is the contact area.

[0111] Select proofing equipment with the same or simulated conditions as the formal printing, and prepare the printing materials, ink, etc.; set the pressure, proofing speed, proofing ink supply and other parameters of the proofing equipment; send the printing materials into the proofing equipment for printing to obtain the sample; use tools such as a densitometer and a magnifying glass to check the color density, dot quality, image clarity, registration accuracy, etc. of the sample according to the preset sample evaluation standards.

[0112] Calculation of pressure P based on plate and cylinder 压 , the expression is as follows:

[0113]

[0114] In the above formula, P 压 is pressure, P0 is standard pressure, K m is the plate material coefficient, S 印版 is the printing plate area, K r is the surface roughness coefficient of the roller. Among them, the standard pressure P0 is the basic pressure value set by the equipment.

[0115] In this embodiment, K m The value range is 0.8-1.2.

[0116] Calculate the proofing speed V based on the printing plate, ink and substrate 打样 , the expression is as follows:

[0117] V 打样 =V0×K i ×K y ×K s

[0118] In the above formula, V 打样 is the proofing speed, V0 is the basic proofing speed, K i K is the plate run coefficient, y is the ink drying speed coefficient, K s It is the speed adaptability coefficient of printing materials.

[0119] In this embodiment, the plate run coefficient K i The value range is 0.8-1.2. Ink drying speed coefficient K y The value range is 1-1.5. Inks with fast drying speed allow for higher proofing speeds. Printing material speed adaptability coefficient K s It is 0.9-1.1.

[0120] Calculate the proofing ink supply Q based on the printing material, proofing speed and ink 油墨 , the expression is as follows:

[0121]

[0122] In the above formula, Q 油墨 is the proofing ink supply, Q0 is the standard ink supply, C 覆盖 is the printing plate image coverage, K a is the ink absorption coefficient of the printing material, V 打样 is the proofing speed, K e is the ink transfer efficiency coefficient.

[0123] In this embodiment, the ink absorption coefficient of the printing material K a The value range is 1-1.5. Ink transfer efficiency coefficient K e The value range is 0.8-1.2.

[0124] S4. Print the printing material and divide the printed matter.

[0125] The printing material is continuously fed into the printing press, and the ink is evenly coated on the printing plate through the ink feeding, ink transfer and ink leveling systems. Under the pressure of the impression cylinder, the ink on the printing plate is transferred to the printing material. The printing quality is continuously monitored during the printing process, and the color, registration, etc. are checked every certain number of sheets.

[0126] Calculate printing speed V based on printing requirements, ink and equipment 印刷 , the expression is as follows:

[0127] V 印刷 =V1×K dot ×K col ×K y ×K eq

[0128] In the above formula, V 印刷 is the printing speed, V1 is the basic printing speed, K dot is the dot restoration quality coefficient, K col is the color uniformity coefficient, K y is the ink drying speed coefficient, K eq is the equipment performance correction factor.

[0129] In this embodiment, the dot restoration quality coefficient K dot The value range is 0.8-1.2. For high-precision image printing, such as art albums, K dot It can be taken as 0.8. For general text and simple pattern printing, K dot It can be 1.2. Color uniformity coefficient K col The value range is 0.9-1.1. For high-end packaging printing, to ensure uniform color, K col 0.9 is acceptable, for ordinary leaflet printing, K col 1.1 is recommended.

[0130] According to the shape of the product, a die-cutting knife is embedded on a wooden or metal plate to make a die-cutting plate. The printed matter is placed on the workbench of the die-cutting machine, the die-cutting pressure is calculated and controlled, and the die-cutting knife cuts the printed matter through the pressure device.

[0131] Calculate the die-cutting pressure P based on the printed material and the die-cutting knife 模切 , the expression is as follows:

[0132] P 模切 =S 抗 ×L 刀 ×W 刀

[0133] In the above formula, P 模切 is the die cutting pressure, S 抗 is the shear strength of printed materials, L 刀 is the die cutting knife length, W 刀 The width of the die cutter.

[0134] The present invention improves the clarity and material utilization rate of printed products by adopting precise resolution adjustment and plate layout algorithms in the pre-press design and graphic processing stages; the plate making process is based on a precise exposure energy formula and precise parameter control of each step to improve the quality and printing durability of the printing plate; the plate mounting and proofing processes use scientific tension control formulas and sample evaluation standards to ensure printing registration accuracy and sample quality; the pressure is systematically adjusted during the printing process to improve the consistency of printed products; the precise calculation of die-cutting pressure in the post-press process reduces product damage and improves production efficiency and product quality.

[0135] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0136] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A flexographic printing method, characterized in that: The following steps are involved: S1, draw the image and adjust the image resolution, calculate the number of impositions, and convert the image into positive negative film; S2, making printing plates based on positive negative film; S3, mount the printing plate and make proofs; S4. Print the printing material and divide the printed matter.

2. A flexographic printing method according to claim 1, characterized in that: In S1, the image resolution is adjusted, and the expression is as follows: In the above formula, W 原 is the original image width, H 原 is the original image height, R 原 is the original image resolution, R 目 is the target resolution.

3. A flexographic printing method according to claim 1, characterized in that: In S1, the number of impositions is calculated, and the expression is as follows: In the above formula, N is the number of panels, S is 幅面 is the printing equipment format area, S 产品 is the product area, k 出血位 Bleeding site ratio.

4. A flexographic printing method according to claim 1, characterized in that: S2 includes the following steps: S21, placing the photosensitive resin plate in a plate exposure machine, laminating it with the positive negative film, and performing back exposure; S22, after the back exposure is completed, the main exposure is performed; S23, after the main exposure is completed, the plate is placed in a developer and rinsed with a developer; S24, removing the solvent by hot air drying or vacuum drying to remove impurities remaining on the plate surface; S25, post-exposing the plate.

5. A flexographic printing method according to claim 4, characterized in that: The energy range of back exposure is 50-150mJ / cm 2 , the energy range of the main exposure is 200-500mJ / cm 2 , the energy range of post-exposure is 50-100mJ / cm 2 .

6. A flexographic printing method according to claim 5, characterized in that: In S23, the developer is rinsed based on the developer concentration, the rinse time and the rinse temperature; The developer concentration expression is as follows: C 浓 =C0×K m ×K d In the above formula, C 浓 is the developer concentration, C0 is the base developer concentration, K m is the plate type correction factor, K d is the image and text complexity correction coefficient; The flushing time expression is as follows: t 冲 =t0×(1+a×(C 浓 -C 标准 )+b×(D-D 标准 )) In the above formula, t 冲 is the flushing time, t0 is the recommended flushing time, a is the concentration influence coefficient, C 浓 is the developer concentration, C 标准 is the standard developer concentration, b is the thickness influence coefficient, D is the plate thickness, D 标准 It is the standard plate thickness; The flushing temperature expression is as follows: In the above formula, T 冲 is the flushing temperature, T0 is the recommended flushing temperature, K en is the ambient temperature correction factor, K eq is the equipment performance correction factor, t 冲 is the flushing time, t 标准 This is the standard flushing time.

7. A flexographic printing method according to claim 4, characterized in that: In S24, the hot air drying temperature is 50-80°C and the time is 10-30 minutes.

8. A flexographic printing method according to claim 1, characterized in that: In S3, the printing plate is pasted, and the expression of the printing plate pasting tension is as follows: In the above formula, T 张 is the plate pasting tension, k1 is the viscosity coefficient of the double-sided tape or glue, L 印版 is the length of the printing plate, W 印版 is the printing plate width, S 接触 is the contact area.

9. A flexographic printing method according to claim 8, characterized in that: In S3, proofing is performed based on the pressure of the proofing device, the proofing speed, and the supply of the proofing ink; The pressure expression is as follows: In the above formula, P 压 is pressure, P0 is standard pressure, K m is the plate material coefficient, S 印版 is the printing plate area, K r is the roller surface roughness coefficient; The proofing speed expression is as follows: In 打样 =V0×K i ×K y ×K s In the above formula, V 打样 is the proofing speed, V0 is the basic proofing speed, K i K is the plate run coefficient, y is the ink drying speed coefficient, K s is the speed adaptability coefficient of the printing material; The expression of proofing ink supply is as follows: In the above formula, Q 油墨 is the supply of proofing ink, Q0 is the standard ink supply, C 覆盖 is the printing plate image coverage, K a is the ink absorption coefficient of the printing material, V 打样 is the proofing speed, K e is the ink transfer efficiency coefficient.

10. A flexographic printing method according to claim 1, characterized in that: In S4, the die-cutting knife cuts the printed matter according to the die-cutting pressure through the pressure device. The die-cutting pressure is expressed as follows: P 模切 =S 抗 ×L 刀 ×W 刀 In the above formula, P 模切 is the die cutting pressure, S 抗 is the shear strength of printed materials, L 刀 is the die cutting knife length, W 刀 The width of the die cutter.

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