JP5418400B2 - Gravure printing plate - Google Patents

Description

  The present invention belongs to the technical field of gravure printing. In particular, the present invention relates to a gravure printing plate capable of avoiding a defect in which ink is transferred to a white background portion (non-image area) in a printed matter and is lightly soiled, that is, a “fogging defect”.

In rotogravure printing, a gravure cylinder (gravure printing plate) having cells (concave portions) formed on the peripheral surface is used as a printing plate. Printing is performed as follows. First, the gravure printing plate is immersed in the ink of an ink pan, the ink is filled in the cell, and excess ink protruding from the cell is scraped off from the peripheral surface by a doctor blade. Next, the gravure printing plate and the printing paper are brought into close contact with each other, and printing pressure is applied to transfer the ink filled in the cells to the printing paper.
In this printing operation, when the ink of the gravure printing plate is scraped off by the doctor blade, the ink transferred to the printing paper should be eliminated in the non-image area. However, there is a problem that so-called “fogging” occurs in which ink scraping is incomplete and the ink is transferred to the non-image area of the printing paper. When the degree of fogging is large, a so-called “fogging defect” occurs, and the printed matter in which the fogging defect occurs is of course a defective product, and there is a lot of loss in materials such as ink and paper, the operating rate of the printing press, etc. It has occurred.

The following four methods can be cited as methods conventionally used to deal with this fogging defect.
(First method) Method to increase doctor linear pressure and reduce scraping amount (Second method) Method to reduce scraping amount by diluting ink and decreasing viscosity (Third method) Doctor A method of preventing excess ink from drying by blowing air onto the printing plate after scratching with a plate (JP-A-10-305555)
(Fourth Method) A method for discriminating plates in which fog occurs by managing the surface roughness (S value: maximum height roughness (JIS '82)) on the plate surface (Patent Document 1).
The problems of these conventional techniques are as follows.
The first method and the second method are not suitable because they are means accompanied by a change in color tone in a printed matter due to a change in conditions such as ink and doctor during printing.
In the third method, since air is blown onto the plate surface, the ink to be transferred is urged to be dried, resulting in a change in color tone in the printed matter.
In the fourth method, the evaluation is based on the S value and is a roughness parameter that takes a difference between only the maximum value of the peak and the minimum value of the valley in the roughness curve. Are not evaluated, and even when different surface shapes are taken, the same value may be obtained, and the surface shapes cannot be distinguished, which is not suitable for evaluation.

JP-A-4-133737

  The present invention has been made to solve the above problems. An object of the present invention is to provide a gravure printing plate capable of avoiding a defect in which ink is transferred to a white background portion (non-image area) in a printed material and is lightly stained, that is, a “fogging defect”.

  In the gravure printing plate according to claim 1 of the present invention, the surface roughness of the plate surface of the gravure printing plate is such that the arithmetic average roughness Ra is 0.050 μm or less, the skewness Rsk is 0.0 or less, and the kurtosis Rku is 2. 5 to 4.0.

  According to the gravure printing plate of the present invention, it is possible to avoid a defect in which ink is transferred to a white background portion (non-image area) in a printed matter and lightly stained, that is, a “fogging defect”.

It is a flowchart (the 1) which shows an example of the process of producing the gravure printing plate of this invention. It is a flowchart (the 2) which shows an example of the process of producing the gravure printing plate of this invention. It is a figure which shows the definition formula of the arithmetic mean roughness (Ra) of the roughness curve which is a parameter showing the surface roughness of the height direction in this invention. It is a figure which shows the definition formula of the skewness (Rsk) of the roughness curve which is a parameter showing the surface roughness of the height direction in this invention. It is a figure which shows the definition formula of the kurtosis (Rku) of the roughness curve which is a parameter showing the surface roughness of the height direction in this invention. It is a figure which shows the relationship between the measured value of the parameter showing the three surface roughness of arithmetic mean roughness (Ra), skewness (Rsk), and kurtosis (Rku) and the presence or absence of fogging in an Example.

Next, embodiments of the present invention will be described with reference to the drawings.
The gravure printing plate is a gravure cylinder in which cells (concave portions) are formed on the peripheral surface. The surface layer of the cylinder of the gravure printing plate has a copper plating layer formed by copper plating with a thickness of 80 to 100 μm. In the copper plating layer, cells (concave portions) are usually formed by an electronic engraving method in which engraving is performed with a diamond needle or a laser beam. Further, chromium plating is applied at a thickness of 8 to 10 μm in order to increase the hardness of the peripheral surface on which the cells (recesses) are formed to give wear resistance and to improve the lubricity between the plate surface and the doctor blade.
The surface layer of the cylinder is formed so as to be peelable, and after printing, a new copper plating layer is formed on the cylinder from which the surface layer has been peeled and reused.

The surface processing in the process of manufacturing the above gravure printing plate is shown in FIGS. 1 and 2 as a flow diagram. FIG. 1 shows the first half of the surface treatment (1), and FIG. 2 shows the second half of the surface treatment (2).
First, in step S101 (copper plating) in FIG. 1, a surface layer is formed by performing copper plating on the peripheral surface of the cylinder with a thickness of 80 to 100 μm.
Next, in step S102 (surface grinding), the surface layer formed on the peripheral surface of the cylinder is ground. For this grinding process, for example, a cylinder surface grinding machine (dedicated processing machine) dedicated to a gravure printing plate having a rotating disk with grinding paper attached thereto can be used. In addition, a buffing device that polishes by rotating an abrasive around the surface (surface) of a polishing wheel (buff) made of cloth or other materials and rotating to a mirror surface is also used.
Next, in step S103 (outer diameter measurement), the outer diameter of the cylinder portion of the cylinder is measured. Data for determining whether or not the entire cylinder has a desired outer diameter is obtained by measuring the outer diameters at a plurality of locations in the cylinder.
Next, in step S104 (surface roughness measurement), the surface roughness measurement of the peripheral surface of the cylinder (the surface that becomes the printing plate) is performed. Data for determining whether or not the entire cylinder has a desired surface roughness is obtained by measuring the surface roughness at a plurality of locations in the cylinder.
Next, in step S105 (OK?), It is determined whether or not the cylinder has a desired outer diameter and a desired surface roughness. When the cylinder has a desired outer diameter and a desired surface roughness, the surface processing of the cylinder is finished. When the cylinder does not have the desired outer diameter and the desired surface roughness, the process returns to step S102, and surface grinding is performed so as to obtain the desired outer diameter and the desired surface roughness.

Subsequently, for the cylinder determined to have the desired outer diameter and the desired surface roughness (OK) in step S105,
First, in step S201 (engraving) in FIG. 2, engraving is performed on the copper plating layer of the cylinder with a diamond needle or a laser beam to form a cell (concave portion).
Next, in step S202 (chrome plating), chromium plating is performed on the peripheral surface on which the cells (recesses) are formed.
Next, in step S203 (surface grinding), the surface layer formed on the peripheral surface of the cylinder is ground. For this grinding process, for example, a cylinder surface grinding machine (dedicated processing machine) dedicated to a gravure printing plate having a rotating roll with grinding paper attached thereto is used.
Next, in step S204 (surface roughness measurement), the surface roughness measurement of the peripheral surface of the cylinder (the surface to be a printing plate) is performed. Data for determining whether or not the entire cylinder has a desired surface roughness is obtained by measuring the surface roughness at a plurality of locations in the cylinder.
Next, in step S205 (OK?), It is determined whether or not the desired surface roughness is obtained. When the desired surface roughness is obtained, the surface processing of the cylinder is finished. When the cylinder does not have the desired surface roughness, the process returns to step S202, and surface grinding is performed to achieve the desired surface roughness.

In the gravure printing plate of the present invention, arithmetic average roughness (Ra), skewness (Rsk), and kurtosis (Rku) are applied as parameters for managing the surface roughness in the surface processing (2).
The arithmetic average roughness (Ra) in the present invention is the arithmetic average roughness (Ra) of a roughness curve as a parameter representing the surface roughness in the height direction. The arithmetic average roughness (Ra) is in accordance with “JIS B 0601: 2001” which is a standard of JIS (Japanese Industrial Standards).
Only the reference length is extracted from the roughness curve in the direction of the average line, the X-axis is taken in the direction of the average line of the extracted portion, the Z-axis is taken in the height direction, and the roughness curve is z = Z (x) Represent. At that time, the arithmetic average roughness (Ra) is defined as an average value of absolute values of Z (x). That is, when the range from x = 0 to lr is measured, the value obtained by integrating the absolute value of Z (x) from x = 0 to lr is divided by lr as shown by the mathematical expression in FIG. As a result, the arithmetic average roughness (Ra) can be obtained.

The skewness (Rsk) in the present invention is the skewness (Rsk) of a roughness curve as a parameter representing the surface roughness in the height direction. The skewness (Rsk) is in accordance with “JIS B 0601: 2001” which is a standard of Japanese Industrial Standards (JIS).
Only the reference length is extracted from the roughness curve in the direction of the average line, the X-axis is taken in the direction of the average line of the extracted portion, the Z-axis is taken in the height direction, and the roughness curve is z = Z (x) Represent. At that time, the skewness (Rsk) is defined as an average value of the cube of Z (x). That is, when the range from x = 0 to lr is measured, the value obtained by integrating the cube of Z (x) to x = 0 to lr is expressed as the cube of Rq, as shown by the mathematical expression in FIG. Skewness (Rsk) can be obtained as a divided value. As shown in FIG. 4, Rq is a height represented by the square root of the mean square of the roughness curve.

The kurtosis (Rku) in the present invention is a kurtosis (Rku) of a roughness curve as a parameter representing the surface roughness in the height direction. The kurtosis (Rku) is in accordance with “JIS B 0601: 2001” which is a standard of JIS (Japanese Industrial Standards).
Only the reference length is extracted from the roughness curve in the direction of the average line, the X-axis is taken in the direction of the average line of the extracted portion, the Z-axis is taken in the height direction, and the roughness curve is z = Z (x) Represent. At that time, kurtosis (Rku) is defined as the average value of the fourth power of Z (x). That is, when the range from x = 0 to lr is measured, the value obtained by integrating the fourth power of Z (x) from x = 0 to lr is expressed as the fourth power of Rq, as shown by the mathematical expression in FIG. The kurtosis (Rku) can be obtained as a divided value. As shown in FIG. 4, Rq is a height represented by the square root of the mean square of the roughness curve.

(Example)
Next, examples will be described. In the process of the gravure printing plate manufacturing factory corresponding to step S204 (surface roughness measurement) of the surface processing (2) described above, arithmetic average roughness (Ra), skewness are used as parameters for managing the surface roughness of the gravure printing plate. (Rsk) and kurtosis (Rku) are measured.
The following apparatus was used as a measuring apparatus for the actual measurement.
Surface roughness measuring instrument ・ Measuring instrument: Surfcoder SE1200 (product of Kosaka Laboratory Ltd.)
・ Measurement method: 2D ・ Measurement range: 4mm
・ Measurement magnification: 20K
・ Λs filter: Gauss
・ Cutoff type: Gaussian ・ Cutoff wavelength: 0.80mm
・ Inclination correction: least square line ・ Measurement speed: 0.20 mm / s
・ Pickup type: Standard pickup

In the step corresponding to step S204 (surface roughness measurement), the above surface roughness measuring machine is used to calculate three surface roughnesses: arithmetic average roughness (Ra), skewness (Rsk), and kurtosis (Rku). FIG. 6 shows a table showing a relationship between an example of actual measurement values obtained by measuring parameters to be expressed and the presence or absence of fogging. Judgment on the presence or absence of fogging was made by visually observing the printed matter and when fogging was observed, and when it was not observed.
The actual measurement values shown in FIG. 6 are examples, and the determination was made based on an extremely large number of actual measurement values (2000 or more examples). As a result, in a three-dimensional space with three variables of arithmetic average roughness (Ra), skewness (Rsk), and kurtosis (Rku), a region where fogging occurs is distinguished from a region where fogging does not occur. Is possible.
That is, the surface roughness of the plate surface of the gravure printing plate is such that the arithmetic average roughness (Ra) is 0.050 μm or less, the skewness (Rsk) is 0.0 or less, and the kurtosis (Rku) is 2.5 to 4.0. There is no occurrence of fogging in the area of.

In the comparative example 1 of FIG. 6, the measured value of the skewness (Rsk) is 0.013 and the condition that the skewness (Rsk) is 0.0 or less is not satisfied. When the gravure plate of Comparative Example 1 was used for printing, it was determined that fogging occurred in the printed material.
In Comparative Example 2, the measured value of kurtosis (Rku) is 6.226, and kurtosis (Rku) does not satisfy the condition of 2.5 to 4.0. When the gravure plate of Comparative Example 2 was used for printing, it was determined that fogging occurred in the printed material.
In Comparative Example 3, the measured value of kurtosis (Rku) is 8.940, and the kurtosis (Rku) does not satisfy the condition of 2.5 to 4.0. When the gravure plate of Comparative Example 3 was used for printing, the determination of the occurrence of fog in the printed material was yes.
In Comparative Example 4, the measured value of kurtosis (Rku) is 8.015, and the kurtosis (Rku) does not satisfy the condition of 2.5 to 4.0. When the gravure plate of Comparative Example 4 was used for printing, it was judged that fogging occurred in the printed matter.
In Example 1, the measured value of arithmetic average roughness (Ra) is 0.026 μm, the measured value of skewness (Rsk) is −0.291, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. Further, the measured value of kurtosis (Rku) is 3.857, and the kurtosis (Rku) satisfies the condition of 2.5 to 4.0. When the gravure plate of Example 1 was used for printing, there was no determination of the occurrence of fog in the printed matter.

In Example 2, the measured value of arithmetic average roughness (Ra) is 0.031 μm, the measured value of skewness (Rsk) is −0.287, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. Moreover, the measured value of kurtosis (Rku) is 2.760, and the kurtosis (Rku) satisfies the condition of 2.5 to 4.0. When the gravure plate of Example 2 was used for printing, the occurrence of fogging in the printed material was not judged.
In Example 3, the measured value of arithmetic average roughness (Ra) is 0.030 μm, the measured value of skewness (Rsk) is −0.203, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. Further, the measured value of kurtosis (Rku) is 2.968, and the condition that kurtosis (Rku) is 2.5 to 4.0 is satisfied. When the gravure plate of Example 3 was used for printing, there was no determination of the occurrence of fog in the printed material.
In Example 4, the measured value of the arithmetic average roughness (Ra) is 0.024 μm, the measured value of the skewness (Rsk) is −0.235, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. Further, the measured value of kurtosis (Rku) is 3.062, and the kurtosis (Rku) satisfies the condition of 2.5 to 4.0. When the gravure plate of Example 4 was used for printing, the occurrence of fogging in the printed material was not judged.
In Example 5, the measured value of arithmetic average roughness (Ra) is 0.035 μm, the measured value of skewness (Rsk) is −0.350, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. The measured value of kurtosis (Rku) is 2.883, and the kurtosis (Rku) satisfies the condition of 2.5 to 4.0. When the gravure plate of Example 5 was used for printing, there was no determination of the occurrence of fog in the printed material.
In Example 6, the measured value of arithmetic average roughness (Ra) is 0.018 μm, the measured value of skewness (Rsk) is −0.007, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. Further, the measured value of kurtosis (Rku) is 2.921, and the kurtosis (Rku) satisfies the condition of 2.5 to 4.0. When the gravure plate of Example 6 was used for printing, there was no determination of the occurrence of fog in the printed material.

In Example 7, the measured value of arithmetic average roughness (Ra) is 0.045 μm, the measured value of skewness (Rsk) is −0.215, and the arithmetic average roughness (Ra) is 0.050 μm or less. In addition, the condition that the skewness (Rsk) is 0.0 or less is satisfied. Further, the measured value of kurtosis (Rku) is 3.829, and the condition that kurtosis (Rku) is 2.5 to 4.0 is satisfied. When the gravure plate of Example 7 was used for printing, there was no determination of fog generation in the printed matter.
In Comparative Example 5, the measured value of the skewness (Rsk) is 0.099, and the condition that the skewness (Rsk) is 0.0 or less is not satisfied. When the gravure plate of Comparative Example 5 was used for printing, the determination of the occurrence of fog in the printed material was yes.
In Comparative Example 6, the measured value of the skewness (Rsk) is 0.006 and the condition that the skewness (Rsk) is 0.0 or less is not satisfied. When the gravure plate of Comparative Example 6 was used for printing, it was determined that fogging occurred in the printed material.
In Comparative Example 7, the actually measured value of skewness (Rsk) is 0.506, and the condition that the skewness (Rsk) is 0.0 or less is not satisfied. When printing with the gravure plate of Comparative Example 7, the determination of the occurrence of fogging in the printed material was yes.
In Comparative Example 8, the measured value of arithmetic average roughness (Ra) is 0.052 μm, and the arithmetic average roughness (Ra) does not satisfy the condition of 0.050 μm or less. When the gravure plate of Comparative Example 8 was used for printing, the occurrence of fogging in the printed material was judged to be good.
In Comparative Example 9, the measured value of kurtosis (Rku) is 2.458, and the kurtosis (Rku) does not satisfy the condition of 2.5 to 4.0. When the gravure plate of Comparative Example 9 was used for printing, it was determined that fogging occurred in the printed material.

  In the table | surface shown in FIG. 6, the paper particle size used for the surface grinding process is shown. The paper grain number, for example, # 600 is a number indicating the size of the abrasive grains. The number corresponds to the number of sieves that are 1 inch long (25.4 mm). The larger the number, the smaller the abrasive grain size.

  It can be used in the printing industry that uses gravure printing plates.

Ra arithmetic mean roughness Rsk skewness Rku kurtosis

Claims (1)

A gravure having a surface roughness on a plate surface of a gravure printing plate having an arithmetic average roughness Ra of 0.050 μm or less, a skewness Rsk of 0.0 or less, and a kurtosis Rku of 2.5 to 4.0. Printed version.

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