JP4239438B2 - Can manufacturing method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a process for the preparation of the can subjected to printing in the main body, in particular, an image having a gradation by halftone dot relates reproduced method of manufacturing a can which is printed on the body without the tone jump occurs.
[0002]
[Prior art]
In recent years, the types of products (especially foods and drinks) sold in the form of cans have diversified, and in order to express the products filled in the cans with a good image, there are various kinds of products Printing is applied.
[0003]
Under such circumstances, for a seamless can comprising a main body formed by deep drawing or drawing ironing, etc., and a lid, a dry plate using a photosensitive resin relief plate is usually used as a printing plate. Printing is performed by the offset method.
However, in the case of this dry offset method, if the size of the halftone dot formed on the plate (the diameter in the case of a circular halftone dot) is smaller than about 50 μm, the plate making process and the printing process due to the strength characteristics of the plate material. In this case, the halftone dots formed on the plate are lost. For this reason, in the case of printing that reproduces gradation of a continuous tone image, a portion that needs to be reproduced with a halftone dot of 50 μm or less is not reproduced, and so-called tone jump occurs. In particular, as shown in FIG. 9, since the halftone dots are regularly and continuously printed along the boundary between the printed portion and the portion not printed, the boundary is formed as a continuous linear connection. It is visually recognized and the tone jump appears clearly.
[0004]
Such a tone jump deteriorates the quality of printing and lowers the product image of the canned product itself. Therefore, a technique for preventing this as much as possible and making the tone jump inconspicuous is required.
[0005]
Conventionally, as a method for preventing a tone jump, for example, disclosed in Japanese Patent No. 3131524, “Threshold Matrix Generation Method and Image Binarization Method and Apparatus”, and Japanese Patent Application Laid-Open No. 7-73310. There is a “frequency modulation halftone screen and its processing method”.
[0006]
In the technique disclosed in Japanese Patent No. 311524, when binarizing multi-gradation image data, a threshold matrix region to be used is divided into a plurality of sub-matrices having the same size, and each sub-matrix is divided. The difference between the plurality of included threshold values is set to a predetermined value, and the plurality of threshold values are randomly arranged in each sub-matrix. According to this technique, the spatial frequency of the threshold distribution is higher than the threshold matrix for a conventional halftone dot. Therefore, if binarization is performed using such a threshold matrix, the technique using the conventional halftone dot is achieved. Compared to this, sharp edges in an image can be reproduced well.
[0007]
Further, the technique disclosed in Japanese Patent Application Laid-Open No. 7-73310 is a technique of “mesh screen processing of a continuous tone image using frequency modulation mesh screen processing”, which is often seen in the conventional frequency modulation method. , Preventing unwanted patterns or textures and eliminating tone tone instability.
[0008]
[Problems to be solved by the invention]
However, since the technology of Japanese Patent No. 3113524 requires complicated signal processing, dedicated software and a processing device are required, which increases the cost. Further, since the technique of Japanese Patent Laid-Open No. 7-73310 uses halftone dots in a random arrangement for the entire image, the minimum size of halftone dots must be about 10 to 30 μm so as not to make the roughness noticeable. , Halftone dots having a size of 50 μm or less are lost, and tone jump cannot be eliminated.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a can which is printed at a low cost and inconspicuous tone jump by using a conventional processing apparatus and software. And
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a method of manufacturing a can comprising a main body and a lid , and having a relief printing of relief printing on the main body, and digitizing a document to be printed on the main body to produce a digital gradation image. Then, the digital gradation image is duplicated, the duplicated digital gradation image is binarized by halftone conversion to create a mask image, and the digital gradation image is covered with the mask image. The digital gradation image is thinned, a printing plate is created based on the thinned digital gradation image, and the main body is printed by a printing machine using the printing plate. This is a method for manufacturing a can which is composed of a set of halftone dots larger than 50 μm, and whose gradation changes visually smoothly.
[0011]
Further, the present invention provides a method for adjusting the thinning process by using an adjustment tone curve for the duplicated digital gradation image before binarizing the duplicated digital gradation image. is there.
[0012]
According to such a can manufacturing method, a can in which the gradation of the printing portion applied to the main body is visually and smoothly changed can be easily and inexpensively manufactured.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described, but the present invention is of course not limited to this embodiment.
[0014]
The seamless can includes a main body 1 including a can body and a bottom, and a lid (not shown) that closes an opening of the main body 1. For this seamless can, a material obtained by applying physical and chemical treatments to aluminum, steel, laminated steel plate or the like is used.
[0015]
The body of a seamless can is usually formed by a process of forming the body by deep drawing or drawing ironing with a molding machine, a process of printing a predetermined image on the body surface of the body using printing ink, and a thermosetting paint. It is formed through a step of forming a thermosetting coating film on the body surface of the main body used, a step of solidifying the printing ink and the thermosetting coating by heating, and an inner surface coating step. In addition, as a printing ink and a body surface coating material, you may use a ultraviolet curing type, and in this case, a printing ink and a body surface coating material are solidified using an ultraviolet irradiation device.
[0016]
Here, printing on the body surface of the seamless can is performed by a relief printing dry offset method, but the printing plate is created by the printing machine in the procedure shown in FIG. 2 using the apparatus shown in FIG. In FIG. 1, 11 is an input unit, 12 is an image conversion unit, 13 is an image processing unit, 14 is a synthesis unit, 15 is a negative film creation unit, and 16 is a plate creation unit.
[0017]
A document image to be printed and displayed on the body surface of the can is input by the input unit 11, digitized by the image conversion unit 12 to be a digital gradation image (S 1), and stored in a memory (not shown) of the image conversion unit 12. Here, the digital gradation image refers to a digital image having gradation values corresponding to light and shade such as photographs and paintings, and the light and shade gradation is, for example, an image as shown in FIG.
[0018]
Next, the image processing unit 13 inputs image data obtained by copying a digital gradation image, performs binarization processing based on the gradation value of the digital gradation image, and creates a mask image.
Note that the image processing unit 13 adjusts the tone of the digital gradation image by using an adjustment tone curve for the copied digital gradation image before the binarization processing, if necessary, and then A binarization process is performed to create a mask image for performing a thinning process suitable for the printing conditions. Various adjustment tone curves can be selected and used. For example, when a tone curve as shown in FIG. 4 is used for a digital gradation image, the tone of the digital gradation image is a halftone. It rises in the upper part, for example, as shown in FIG.
In this way, the image processing unit 13 performs tone adjustment on the digital gradation image before binarization as necessary. Since the image after the binarization process is not a grayscale image with light and shade, adjustment using a tone curve cannot be performed.
[0019]
In the binarization processing in the image processing unit 13, the copied digital gradation image is converted into halftone dots using a halftone screen, and this is used as a mask image for thinning processing (S4). That is, when a digital gradation image is converted into a halftone dot using a halftone screen, the gradation image is converted into a monochrome two gradation halftone dot having a different area corresponding to the gradation value.
6A shows an image diagram converted into halftone dots, and FIG. 6B shows an enlarged image diagram of a part of FIG. 6A.
[0020]
The synthesizing unit 14 reads the digital gradation image stored in the image conversion unit 12, and also reads the mask image created by the image processing unit 13 and puts it on the digital gradation image (S5). As a result, the mask image hides a range (halftone dot) to be thinned out in the digital gradation image, and thinning processing is performed.
FIG. 7A shows an image when a mask image (dotted data) is put on a digital gradation image (gradation image data), and FIG. 7B shows an opaque white portion of the mask image. FIG. 6 is an image diagram showing a result when a digital gradation image is thinned out with a black portion transmitted.
[0021]
The negative film creating unit 15 creates a negative film based on the image data thinned out by the synthesizing unit 14 (S6), and the plate creating unit 16 creates a printing plate using the negative film (S7).
Here, creation of a negative film and creation of a printing plate are performed by a negative film creation unit 15 and a plate creation unit 16 which have been conventionally used, in the same manner as in the past.
[0022]
Next, a printing machine (not shown) uses the printing plate created by the plate creating unit 16 to print a document image on the body surface of the seamless can as in the conventional case. As shown in FIG. 8, the main body 1 printed on the cylinder surface using the printing plate subjected to the thinning process as described above has a visually smooth gradation reproduction, and tone jump is seen. Absent.
[0023]
As a result, the body of the seamless can manufactured by the above method prints irregularly and discontinuously halftone dots by thinning-out processing, particularly in light-colored areas in areas where dark and light gradations are printed and reproduced. Therefore, even if the size of the halftone dot to be printed is larger than 50 μm, the boundary between the portion where the halftone dot is printed and the portion where the halftone dot is not printed is visually recognized as a continuous linear connection. Disappears. As a result, tone jumps can be eliminated, and visually smooth gradation reproduction is realized from a dark portion to a light portion.
[0024]
【The invention's effect】
According to the can manufacturing method of the present invention, conventionally used plate making machines and printing machines can be used, and general-purpose image processing software can be used, and printing can be performed by a simple and inexpensive method. Cans can be manufactured. Further, the can produced by the production method of the present invention has a gradation smoothly reproduced from a dark portion to a light portion in the printing section of the main body, and can improve the quality of the can.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a printing plate making apparatus used when a seamless can according to an embodiment of the present invention is manufactured.
FIG. 2 is a block diagram showing an embodiment of a printing plate making procedure when a seamless can according to an embodiment of the present invention is manufactured.
FIG. 3 is an image diagram of a digital gradation image according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of an adjustment tone curve according to an embodiment of the present invention.
FIG. 5 is an image diagram of a digital gradation image after using an adjustment tone curve according to an embodiment of the present invention.
FIG. 6A is an image diagram of a halftone dot mask image according to an embodiment of the present invention. (B) is the image figure which expanded a part of mask image of (a).
FIG. 7A is an image diagram showing a state in which a mask image is put on a digital gradation image. (B) is an image diagram showing a result of thinning processing by covering a digital gradation image with a mask image.
FIG. 8 is a perspective image view of a seamless can body manufactured by a method according to an embodiment of the present invention.
FIG. 9 is a perspective image view of a conventional seamless can body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Input part 12 Image conversion part 13 Image processing part 14 Composition part 15 Negative film creation part 16 Plate creation part

Claims (2)

In the manufacturing method of the can which consists of a main body and a lid, and has performed dry offset printing of a relief printing on the main body,
Digitize the original to be printed on the main body to create a digital gradation image,
Next, the digital gradation image is duplicated, and the duplicated digital gradation image is binarized by halftone conversion to create a mask image,
Covering the digital gradation image with the mask image, thinning the digital gradation image,
A printing plate is created based on the thinned digital gradation image, and the main body is printed by a printing machine using the printing plate,
A method for producing a can, characterized in that a printing part is made of a set of halftone dots larger than 50 μm, and the can has a gradation that visually changes smoothly.   2. The thinning process is adjusted using a tone curve for adjustment for the duplicated digital gradation image before binarizing the duplicated digital gradation image. A method for manufacturing cans.

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