JP4827122B2 - Method for forming printed image applied to shoulder of can body - Google Patents

Description

  The present invention relates to a can body, such as a bottle-shaped can and an aerosol can, in which the upper part of a cylindrical body is gradually reduced in diameter to form an inclined shoulder, and in particular, such a can body As a method of forming a printed image to be applied to the shoulder, it is a cylindrical can with a bottom that is an intermediate molded product of the can body. In addition, the present invention relates to a method for obtaining a print image previously applied to the outer surface as a flat image serving as a basis of a printing plate.

  Among the metal bottle-shaped cans that are integrally formed with a cylindrically-thinned body, an inclined shoulder, and a small-diameter mouth-and-neck, those having a threaded part in the mouth-and-neck, Reseal (reseal) is possible by combining with a cap with a screw, and is superior to PET bottles in terms of resource recycling rate, light shielding, gas permeation resistance, rapid cooling, etc. For this reason, in recent years, many beverage cans containing various beverages have been used in the market.

  That is, the bottom side of the bottomed cylindrical can is shaped into the mouth and neck and the shoulder (a separate bottom lid is fastened and fixed), the opening side of the bottomed cylindrical can is the mouth and neck Bottle type cans that are molded on the shoulder (the body and bottom are connected together) have been widely available in the beverage can market, but in any such type of bottle can However, for printed parts such as letters and designs provided on the outer surface, it has been usual to form an inclined shoulder and a small-diameter cylindrical mouth and neck from a bottomed cylindrical can, which is an intermediate molded product. After that, printing is performed on the outer surface of the cylindrical body. Here, “printing” includes not only the case of printing directly on the can body, but also the case of sticking a printed resin film on the can body.

  In such a bottle-type can that has been printed by a conventional method, no printed portion is provided on the shoulder that occupies a relatively large area. On the other hand, for a bottomed cylindrical can which is an intermediate molded product, after printing on the outer surface of the body portion, an inclined shoulder portion and a small diameter cylindrical mouth and neck portion are formed as follows. Patent Documents 1 to 3 are disclosed respectively. In particular, in Patent Document 3 below, printing is performed on an area including a portion formed on a shoulder portion on an outer surface of a body portion of a bottomed cylindrical can which is an intermediate molded product. It is disclosed that the printing portion is provided not only on the body portion of the bottle-type can but also on the shoulder portion by applying in advance.

However, in any type of bottle-shaped can, when printing is performed in advance on the region including the portion formed on the shoulder on the outer surface of the body of the bottomed cylindrical can which is an intermediate molded product as described above In the subsequent reduction of diameter, as part of the cylindrical body is reshaped into an inclined shoulder, images such as letters and designs previously applied to the shoulder become parts, As it goes upward (closer to the mouth / neck portion), the taper is deformed into a tapered state and becomes distorted.
This is also true for aerosol cans molded by the same molding method.

On the other hand, in Patent Document 4 below, printing is performed on the outer surface of the body portion of the bottomed cylindrical can, which is an intermediate molded product, up to the portion that is to be formed on the shoulder portion by the subsequent diameter reduction processing. In addition, print letters and designs on the part that is to be molded on the shoulder, so that the image becomes wider as it goes upward (closer to the mouth and neck) with respect to the desired shape. By preliminarily forming a distorted shape, images of characters, designs, etc. by printing on can bodies (bottle type cans and aerosol cans) after shoulder molding can be applied to the shoulder in a desired shape without distortion. To do so is disclosed.
JP-A-5-229545 JP 2000-191006 A JP 2001-ll4245 JP 2004-168346 A

  By the way, when selling products of various beverage cans on a display shelf in sales at a retail store such as a convenience store, for example, products with relatively high can height are placed on the lower shelf and the height of the can In many cases, products with a relatively low price are placed on the upper shelf, and the height of the shelf on which the products are placed is often categorized according to the can size. In some cases, they are displayed on a shelf in a prominent position and sold. In such a product display situation, when a printed image is applied to the shoulder of the can body of a beverage can product using a bottle-shaped can, the printed image applied to the inclined shoulder is visible. This differs depending on the height of the shelves arranged (that is, the angle of the line of sight of the consumer), and the tendency is particularly remarkable when the inclined surface of the shoulder is a curved surface.

  Therefore, in a bottle-shaped can having an inclined shoulder portion, when a printed image is given not only to the trunk portion but also to the shoulder portion, for the printed image of the shoulder portion, the size of the can body, Depending on the shape of the shoulders, the position of the shelf displayed as a product, etc., that is, taking into account the angle of the consumer's line of sight, it is preferable to form the printed image so that it can be seen favorably. From this point of view, the print image applied to the shoulder of the bottle-shaped can is assumed to be the most distorted when viewed from the viewing angle, assuming that the consumer views the product from a certain viewing angle. It is required to be small and recognizable.

  With respect to this point, the above-mentioned Patent Document 4 discloses that a printed image such as characters and designs applied to a cylindrical portion that is to be a shoulder portion in an intermediate molded product of a bottle-shaped can is distorted when the shoulder portion is formed. Although the method of making it become a desired shape is disclosed, this method is intended to reduce the distortion of the image itself such as characters and designs applied to the shoulder, Assuming a specific line-of-sight angle, the “look” when the consumer views the product at the line-of-sight angle is not taken into consideration.

  That is, even if the distortion of the image itself applied to the shoulder after molding is small, it is provided on the inclined shoulder, so that depending on from which direction the consumer views the image, The impression will be very different, especially when the inclined surface of the shoulder is formed as a curved surface, the appearance will change greatly due to the difference in the inclination of the viewing angle of the consumer with respect to the can axis direction. Become. On the other hand, in the method disclosed in the above-mentioned Patent Document 4, it is not considered to reduce the distortion of the image when viewed from a certain gaze angle. The problem is that the appearance of an image when viewed from a specific angle is not always optimal.

  An object of the present invention is to eliminate the above-mentioned problems. Specifically, the present invention is an intermediate molded product for a can body having an inclined shoulder such as a bottle-type can or an aerosol can. When a printed image is applied not only to the body of the can body but also to the shoulder by applying a print image to the cylindrical part including the part that will become the shoulder for the bottomed cylindrical can Assuming the viewing angle when the consumer sees, the printed image on the shoulder should be viewed in the optimal state with the least sense of discomfort when viewing the can body from that viewing angle. Is an issue.

In order to solve the above-mentioned problems, the present invention intends to form a can body having an inclined shoulder portion into a shoulder portion by a diameter reducing process with a bottomed cylindrical can which is an intermediate molded product thereof. As a method for obtaining a print image preliminarily applied to the outer surface of the cylindrical portion that is the area of the image as a flat image that is the basis of the printing plate, the original image before image conversion at the original image input stage reading the digital pixel information for each pixel, at the shoulder portion shape setting step sets the shape of the shoulder portion after molding, in line-of-sight angle setting step sets the visual line angle is a tilt angle with respect to the can axis, transform domain In the setting stage, what correction is applied to which area of the original image is set , and a plane perpendicular to the line-of-sight angle set in the line-of-sight angle setting stage is set as a virtual projection plane, and the molded image is formed on this virtual projection plane. The image projected from the shoulder is the desired image So as, by image conversion based on the digital pixel information of the original image, the method of forming a print image so as to form a planar image underlying the printing plate, in the conversion region setting step, setting the horizontal correction, At least one of setting of boundary correction, setting of height direction correction, setting of circumferential direction correction, and setting of perfect circle correction is performed .

According to the method for forming a printed image applied to the shoulder of the can body according to the present invention as described above, a desired line-of-sight angle is set for the print image applied to the shoulder of the can body, and is orthogonal to the line-of-sight angle. Since the plane is a virtual projection plane, and the plane image that forms the basis of the printing plate is formed so that the image projected from the shoulder after molding on the virtual projection plane is a desired image, this plane is formed. After printing on the bottomed cylindrical can, which is an intermediate molded product, using the printing plate that adopted the image as the shoulder image, when the inclined shoulder is formed by diameter reduction processing, When the printed image applied to the shoulder is viewed from the direction of the desired line-of-sight angle, the desired image (that is, the image with the least discomfort and the optimum state) can be obtained.
In particular, in the conversion area setting stage, what correction is applied to which area of the original image, horizontal correction setting, boundary correction setting, height direction correction setting, circumferential direction correction setting, perfect circle Since at least one of the correction settings is performed, it is possible to obtain an image with a smaller sense of incongruity in terms of human visual characteristics.

For cans with slanted shoulders such as bottle-shaped cans and aerosol cans, printed images are printed on cylindrical parts including the parts that will become shoulders, compared to bottomed cylindrical cans that are intermediate molded products When applying a print image to the shoulder as well as the body of the can body, when viewing the can body from the viewing angle, assuming the viewing angle when the consumer sees In addition, the purpose of making the printed image applied to the shoulder portion appear to be in an optimum state with the least sense of incongruity is shown in the original image input stage as specifically shown in the following embodiments as the best mode. The original image before image conversion is read as digital pixel information for each pixel, the shoulder shape after molding is set at the shoulder shape setting stage, and the line of sight is the inclination angle with respect to the can axis at the line-of-sight angle setting stage to set the angle, in the conversion region setting step, which region of the original image With what sets or corrects the applied line-of-sight angle setting and viewing angle and a plane virtual projection plane orthogonal to the set in step, the image is desired to be projected from the shoulder portion after forming the virtual projection plane In the method of forming a print image that forms a planar image that is the basis of the printing plate by converting the image based on the digital pixel information of the original image so as to become an image , horizontal correction is performed at the conversion area setting stage. This is realized by performing at least one of setting, boundary correction setting, height direction correction setting, circumferential direction correction setting, and perfect circle correction setting .

  The method of the present invention relates to a bottle-shaped can or an aerosol can having an inclined shoulder portion, and is a bottomed cylindrical can which is an intermediate molded product of such a can body, and is formed on the shoulder portion by reducing the diameter. It is a method for obtaining a print image that is preliminarily applied to the outer surface of a cylindrical portion that is a region to be formed as a flat image that is the basis of a printing plate. For example, in the case of a bottle-type can, the bottom side of a bottomed cylindrical can body is formed into a mouth neck and a shoulder (with a separate bottom lid is fastened and fixed), or a bottomed cylindrical can It can be any type of bottle-shaped can, such as a type in which the opening side of the can body is molded into the mouth and neck and shoulder (the body and bottom are integrated). Not only a type that forms a screw part, but also a bottle type can that does not form a screw part in the mouth and neck. Good.

  In such cans such as bottle-shaped cans, a bottle-shaped can that forms a shoulder (and mouth-and-neck) by diameter reduction after printing on a bottomed cylindrical can that is an intermediate molded product Since the manufacturing method itself is already known in the art (see, for example, Patent Documents 1 to 4 above), detailed description of the manufacturing method of such a bottle-shaped can and the like is omitted.

In the method of the present invention, a plane image serving as a basis for the printing plate is formed by converting the image from the original image, but the bottom of the cylindrical can body is formed by the printing plate employing the plane image. When printing on the shoulder molding planned part, it is not limited to printing directly on the outer surface of the can body with the printing plate, but printing on the printed resin film to be stuck on the outer surface of the can body It may be made to do.
An embodiment of the method of the present invention for obtaining a planar image employed in a printing plate used for printing such a can body will be described below.

  In the method of this embodiment, as shown in FIG. 1, first, in the original image input stage, the original image before image conversion is read as digital pixel information for each pixel. Specifically, an input image file which is an electronic file in which digital pixel information of the original image is recorded is read by an image conversion computer for executing image conversion. The image conversion computer is provided with appropriate input / output devices such as a display, a scanner, and a printer, and a program for executing image conversion is installed in the image conversion computer. The input image file is created by appropriate means, such as converting the original image drawn on the paper into electronic pixel information using a scanner, or creating it directly from the original image created on the computer using image software. It is what is done.

Next, in the shoulder shape setting stage, the shape of the shoulder after the diameter reduction processing is set. Specifically, as shown in FIG.
a. In the can before molding, the position in the height direction of the shape of the can body is designated by a line X.
b. In the shoulder portion of the can after molding, the radius at the position of the line X is represented as R (X), and the height from the lower end of the shoulder portion is represented as H (X).
Correspondence of the radius R (X) and the height H (X) to the line X can be performed by two methods. One is a method of directly associating the numerical values of the radius R (X) and the height H (X) corresponding to the numerical value of each line X in a tabular form based on the actual measurement, and the other is obtained from the actual measurement value. In the case of using the approximate function and directly associating in a tabular format, the measured value data is read by an image conversion computer that performs image conversion.

On the other hand, in the case of using an approximate function, by incorporating a function for obtaining an approximate function into the image conversion computer, it is possible to read measured value data and use the approximate function obtained from the data for image conversion. In addition, it is also possible to obtain an approximate function from measured value data by a separate means in advance and input the approximate function to an image conversion computer by an appropriate means and use it for image conversion.
As an approximation function, it is not always necessary to approximate the shape of the shoulder with one approximation function, and the error can be reduced by dividing a section and using a plurality of approximation functions. In obtaining the approximate function, an appropriate method such as a least square method can be used.

  Regarding the shoulder shape setting stage, in the method of this embodiment, specifically, approximate functions of radius and height are obtained from the measured outer shape data of the bottle can by the least square method, and parameters of each approximate function are obtained. A shape data file in which (coefficient of approximate expression) and actual measurement value data are recorded in CSV format is created, and the shape of the shoulder portion of the can body is set by reading this into an image conversion computer. In this embodiment, an approximate function is used for image conversion, and an actual value is used in the result simulation of image conversion as will be described later. Therefore, the shape data file includes both the approximate function and the actual value data. It is supposed to be.

  That is, by performing image conversion using an approximate function, conversion processing can be performed at high speed, and processing time can be shortened. On the other hand, by using the actually measured value in the result simulation of image conversion, the error between the image actually formed on the can and the image of the result simulation can be reduced. In this case, as the actual measurement value, a horizontal line is printed at a certain interval in the height direction and constant in the circumferential direction with respect to the area formed on the shoulder portion of the bottomed cylindrical can body before the shoulder molding. Numerical value obtained by printing the vertical line at an angle of, measuring the distance between the intersections with the horizontal line for each vertical line and the diameter of the shoulder at the position of each horizontal line after forming the shoulder part Can be used.

In the method of this embodiment, a function that approximates R (X) itself is used for the radius. However, for height, the difference ΔH (Xn) = H (Xn) is not H (X) itself. -H (Xn-1) is used as a function to approximate, and for the approximation of H (X), a result obtained by integrating the difference ΔH (Xn) is used.
Further, if the entire shoulder portion is approximated by one function, the error increases. Therefore, the range of the line X is divided into three, and a function F ₀ (approximates ΔH (Xn) or R (X) within each range. X), F ₁ (X), F ₂ (X) were used.

ここで、Ｘ_snap0はＦ_０とＦ_１のつなぎ目の値であり、Ｘ_snap1はＦ_１とＦ_２のつなぎ目の値である。Ｆ_０（Ｘ），Ｆ_１（Ｘ），Ｆ_２（Ｘ）のパラメータａ_ｎ，ｂ_ｎ，ｃ_ｎ，ｄ_ｎの各パラメータの決定は最小自乗近似によって行なった。

Here, X _snap0 is the value at the joint between F ₀ and F ₁ , and X _snap1 is the value at the joint between F ₁ and F ₂ . _{F 0 (X), F 1} (X), the determination of the parameters of the parameter _{a n, b n, c n} , d n of _F 2 (X) was performed by the least square approximation.

  Next, in the line-of-sight angle setting stage, a line-of-sight angle that is an inclination angle with respect to the can axis is set. The line-of-sight angle is set in consideration of the line-of-sight direction by the consumer, and is arbitrarily set according to the type of the target can and the position displayed at the time of sale. In the method of this embodiment, specifically, the line-of-sight angle is expressed as an inclination angle with respect to the can axis upward from the horizontal, with 0 ° when viewed from the horizontal and 90 ° when viewed from directly above. The line-of-sight angle is set to 45 °.

  Then, after passing through the original image input stage, the shoulder shape setting stage, and the line-of-sight angle setting stage as described above, a plane orthogonal to the line-of-sight angle (line-of-sight direction) is set as a virtual projection plane as shown in FIG. The flat image serving as the basis of the printing plate is formed so that the uncomfortable feeling of the image projected from the shoulder on the virtual projection plane is reduced. In other words, a plane orthogonal to the line-of-sight angle (set at the line-of-sight angle setting stage) is used as a virtual projection plane, and an image projected from the molded shoulder (set at the shoulder shape setting stage) onto the virtual projection plane is desired. Image conversion is performed based on digital pixel information of the original image (input at the original image input stage) so that an image is obtained.

  This image conversion is performed for the half circumference of the shoulder portion of the can body as seen from the viewing angle direction because the intended print image is one that takes into account the consumer's viewing line. Therefore, when an image covering the entire circumference of the shoulder is converted, a printing plate is created by synthesizing the planar images obtained by performing the conversion for each half circumference. In addition, when an image is formed in the entire area of the original image, image conversion is applied to the entire area. However, when an image is formed in a one-point mark or a certain area. Alternatively, image conversion can be applied only to a region where an image is formed.

  Prior to such image conversion processing, in the method of the present embodiment, in the conversion area setting stage, what correction is applied to which area of the read original image is set in advance. . The correction condition setting in this conversion area setting stage will be described in detail later. However, the correction of the height direction and the correction of the circumferential direction are applied to a specific area, or a circular image element is applied to the original image. If it is included, set which correction method is applied to which area according to the configuration of the original image. I can do it.

  As described above, after the correction conditions are set at the conversion area setting stage, the image conversion process is performed. In this image conversion process, the position of the pixel of the original image corresponding to each pixel of the converted image Is determined by a conversion formula, the pixel information (information about color, density, etc.) is recorded as the converted pixel information, and the conversion operation is performed for all the pixels of the converted image by performing this conversion operation. Later plane images can be obtained.

  In addition, by a conversion formula for obtaining an image on the virtual projection plane from the converted plane image, the shoulder image after molding formed from the plane image is displayed as an image projected on the virtual projection plane. The result of image conversion can be simulated. The appearance of the image projected on the virtual projection plane (printed image of the shoulder after molding viewed from the set viewing angle) is displayed on the display as a simulation image or printed on the paper by a printer. Or can be output by an appropriate means, and can also be saved as an electronic file. In addition, about such a planar image and a simulation image, FIG. 11 shows an example of a planar image, and FIG. 12 shows a simulation image obtained from the planar image shown in FIG. (When the printed image is viewed).

  Since the image of the shoulder formed from the converted planar image can be displayed as a simulation image in a state of being projected on the virtual projection plane, the simulation image is viewed, the image conversion condition is changed, and again, By repeating the operation of performing image conversion, it is possible to obtain a printed image with a less uncomfortable feeling. Therefore, it is possible to obtain an optimal printed image without the need to actually manufacture a can and make a prototype, thereby reducing the development cost.

Now, the concept of image conversion in the method of the present embodiment as described above will be described in more detail. In order to express the position of the pixel on the image before conversion, as shown in FIG. Let p be the position in the left-right direction with respect to the origin, and q be the position in the height direction. Similarly, the pixel position is expressed by P and Q in the converted image. Further, a position corresponding to (P, Q) in the image projected on the virtual projection plane after printing the converted image on the can body and projecting on the shoulder is defined as (u, v). Further, F is a map that maps (p, q) to (P, Q), and G is a map that maps (P, Q) to (u, v). In other words,
(P, Q) = F (p, q)
(U, v) = G (P, Q) = G (F (p, q))
Then, in order to achieve the purpose of image conversion, F may be determined so that (u, v) is close to (p, q). That is, if F is a reverse mapping of G, the target state “the image after projection becomes the same as the original image” can be achieved.

A conversion formula for performing such image conversion will be described below. In this image conversion, when the mapping F is determined, each pixel (pixel) of the converted image is located at its position (P, Q). If the position (p, q) of the corresponding original image is determined, the color of the pixel can be determined. That is, what is necessary for the image conversion process is not the mapping F itself that associates (p, q) of the pre-conversion image with (P, Q), but the inverse mapping F ⁻¹ thereof.
In order to obtain the inverse map F- ¹ , the converted image is applied to the outer surface of the cylindrical can body, and then the diameter of the portion is reduced to form a shoulder portion, which is applied to the shoulder portion. A mapping G representing the deformation caused by projecting the image onto the virtual projection plane must be determined.

Therefore, as shown in FIG. In the can before molding, the position in the height direction is designated by line X, b. In the shoulder portion of the can after molding, the radius is R (X) and the height from the lower end of the shoulder portion is H (X) at a position corresponding to the position of the line X. And the position of the circumferential direction is designated by angle (theta) with the can front (direction of a line of sight) defined arbitrarily.
At this time, between (P, Q) and (X, θ), X = Q + X _p (X _p is the pasting position of the lower end of the image)
θ = P / R ₀ (R ₀ is the radius of the bottle-shaped can at the lower end of the shoulder).
And the corresponding position after molding is
x = R (X) · sin θ (x is the right direction when viewed from the front in the horizontal plane)
y = R (X) · cos θ (y is the front direction when viewed from the front in the horizontal plane)
z = H (X) (the vertical direction of the bottle is z)
It becomes.

When this is projected onto a virtual projection plane in which the angle φ is orthogonal to the direction of the line of sight from obliquely above in the front direction of the can (θ = 0 direction), the horizontal position U on the virtual projection plane and the vertical position on the virtual projection plane Each V is represented by the following equation.
U = x = R (X) · sin θ = R (Q + X _p ) · sin (P / R ₀ )
V = z · cosφ-y · sinφ
= H (X) ・ cosφ-R (X) ・ cosθ ・ sinφ
_{= H (Q + X p)} · cosφ-R (Q + X p) · cos (P / R 0) · sinφ
If U and V are translated so that the origins coincide, G is determined.
G: (u, v) = G (P, Q)
u = {R (Q + _Xp ) -R ( _Xp )}. sin (P / _R0 )
_{v = {H (Q + X} p) -H (X p)} · cosφ
_{- {R (Q + X p} ) · cos (P / R 0) -R (X p)} · sinφ

Therefore, the inverse mapping F ⁻¹ for performing image conversion so that the image projected on the virtual projection plane at the line-of-sight angle φ is the same as the original image is F ⁻¹ : (p, q) = F ⁻¹ (P , Q)
p = R (Q + X _p ) · sin (P / R ₀ )
_{q = {H (Q + X} p) -H (X p)} · cosφ
_{- {R (Q + X p} ) · cos (P / R 0) -R (X p)} · sinφ
As a result, a conversion formula for performing image conversion so that the image projected on the virtual projection plane with the line-of-sight angle φ is the same as the original image is obtained.

  By the way, even if image conversion is performed so that the image projected on the virtual projection plane is completely the same as the original image by the conversion formula as described above, the discomfort is not necessarily reduced due to the characteristics of human vision. Not exclusively. On the other hand, the final purpose of the method of the present embodiment is that when the consumer looks at the can body from a certain line-of-sight angle, the feeling of discomfort due to the “human vision” of the printed image given to the shoulder is felt. For that purpose, not only image conversion so that the projected image is exactly the same as the original image, but also image conversion taking into account human visual characteristics. It may be necessary to do.

  Therefore, in the method of the present embodiment, as already described, what correction is to be performed on which area of the original image is set in advance in the conversion area setting stage prior to the image conversion process. In addition, it is possible to obtain an image with a smaller sense of incongruity from the characteristics of human vision. This point will be described in more detail below.

  In the case where an image includes a horizontal line, it is empirically known that it is less strange to convert the horizontal line as it is horizontal. On the other hand, in the method of this embodiment, the horizontal line is included in the image. 5, the horizontal line in the original image is kept horizontal in the converted planar image, as shown in FIG. 5, that is, the pixels in the horizontal positional relationship in the original image are Image conversion is performed so that the coordinate value in the height direction of each pixel does not depend on the coordinate value in the horizontal direction so that the horizontal positional relationship is maintained even in the planar image. For this purpose, horizontal correction is performed as a constraint condition (1) that gives a condition that “Q depends only on q and does not depend on p”.

For such horizontal correction, P in the equation of q described in the above “paragraph 0036” is set to 0 so that the constraint condition (1) is satisfied for F ⁻¹ described in the above “paragraph 0036”. To determine F- ¹ .
F ⁻¹ : (p, q) = F ⁻¹ (P, Q)
p = R (Q + X _p ) · sin (P / R ₀ )
_{q = {H (Q + X} p) -H (X p)} · cosφ- {R (Q + X p) -R (X p)} · sinφ
As a result, an inverse map F ⁻¹ satisfying the constraint condition (1) is obtained.

  When printing a continuous image from the body of the can to the shoulder, convert the shoulder so that the printed image of the shoulder projected onto the virtual projection plane is exactly the same as the original image. The width of the image of the part and the width of the image of the body part may be different, and both images may not be smoothly connected. On the other hand, in the method of the present embodiment, boundary correction for smoothly connecting the shoulder image and the torso image after conversion can be performed.

  In such boundary correction, as the constraint condition (2), as shown in FIG. 8, “(i) the width measured along the circumference at the lower end of the shoulder is matched with the original image. (Ii) In the original image. The image is converted under the condition that the width equal to the width at the lower end of the image is the same as the width at the lower end of the shoulder in the projected image.

Considering this constraint condition (2), if “reverse mapping F ⁻¹ satisfying constraint condition (1)” described in “paragraph 0040” above is used, an image is printed as shown in FIG. the width L ₁ obtained by projecting the image after forming a shoulder in the plane is not consistent with the original image, the actual width L2 measured along the circumference of the can will be different from the original image. That is, when printing a pattern of continuous toward the shoulder portion from the barrel, while the width of the image by the image conversion at the shoulder portion lower end is converted from L ₁ to L _2, the image conversion in the body portion Nasarezu, because the original image is printed directly on the can, a width measured along the circumference of the body portion of the image after printing and molding has a width L ₁ that matches the original image.

Therefore, in this state, both images are not smoothly connected at the boundary between the trunk and the shoulder. Therefore, in order to match the image of the shoulder portion and the barrel, the shoulder portion lower end, it is necessary to the width L ₂ along the circumferential direction of the can is consistent with the original image. For this purpose, the image conversion processing is performed from the previous “the width when the image after molding is projected onto the plane matches the original image” to “the width measured along the circumference of the image after molding into the original image. If it is changed to “Match”, both the shoulder and torso images can be combined.

  However, since the radius of the circumference of the shoulder of the can varies depending on the position, and the projected width is different even if the width along the circumference is the same, if this processing method is adopted, as shown in FIG. Even if the width is the same, the width of the projected image varies depending on the position of the can. This is not desirable because it does not meet the purpose of boundary correction. Therefore, as described above (see FIG. 8), as the processing method in accordance with the purpose of boundary correction, “(i) The width measured along the circumference at the lower end of the shoulder is matched with the original image (ii). ) The same width as the width at the lower end of the image in the original image should be the same as the width at the lower end of the shoulder in the projected image.

Therefore, p of the inverse transformation formula that satisfies the constraint (1) is changed as follows: p = arcsin {R (Q + X _p ) · sin (P / R ₀ ) / R ₀ } · R ₀
At the lower shoulder, R (Q + _Xp ) is equal to _R0 . Therefore, when substituting this into the above formula,
p = arcsin {R (Q + X p) · sin (P / R 0) / R 0} · R 0
= Arcsin {R ₀ · sin (P / R ₀ ) / R ₀ } · R ₀
= Arcsin {sin (P / R ₀ )} · R ₀
= P / R ₀・ R ₀
= P
As described above, the width of the image is equal to the original image at the lower end of the shoulder.

Further, since the horizontal position u when the transformed coordinates (P, Q) are projected is given by u = R (Q + X _p ) · sin (P / R ₀ ),
p = arcsin {R (Q + X p) · sin (P / R 0) / R 0} · R 0
= Arcsin (u / R ₀ ) · R ₀
u = sin (p / R ₀ ) · R ₀
If the horizontal position p of the original image is equal, u is constant regardless of Q (or q).
From the above, it can be seen that the above conversion equation satisfies the conditions (i) and (ii).

  The pixel of each coordinate of the original image corresponding to the coordinate of each pixel of the converted planar image is obtained by the conversion formula obtained as described above, and the pixel information of each pixel after conversion is determined. A planar image is formed. Based on the planar image of the shoulder portion, a printing image of the body portion is appropriately synthesized to produce a printing plate, and then the cylindrical can body, which is an intermediate molded product, is applied to the outer surface of the can body by the printing plate. After applying the print image, the desired shape can be reduced by reducing the diameter of the region (the end on the opening end side or the end on the bottom side) that is to be formed on the shoulder of the cylindrical can. A can body can be obtained.

The conversion equation _{q = {H (Q + X} p) -H (X p)} of the following as described in "paragraph 0040" above _{· cosφ- {R (Q + X} p) -R (X p)} · sinφ
And, conversion equation p = arcsin {R (Q + X p) · sin (P / R 0) / R 0} below that is described in the "Paragraph 0046" above · _{R 0}
Is a conversion formula in the case where horizontal correction in the height direction and boundary correction in the width direction are simultaneously applied to the original image.

  It is also possible to apply such conversion only in the height direction of the image or only in the circumferential direction. For example, in an image that is arranged so that images are continuously connected in the circumferential direction of the shoulder, there is a case where no sense of incongruity is generated even if the transformation is not applied in the circumferential direction. It only needs to be applied in the height direction. When performing height direction correction in which image conversion is applied only to the height direction of an image, or in performing circumferential direction correction to be applied only in the circumferential direction, the following conversion equation is obtained.

When correcting in the height direction p = P
_{q = {H (Q + X} p) -H (X p)} · cosφ- {R (Q + X p) -R (X p)} · sinφ
By setting the height direction correction as described above, the length measured in the height direction of the image projected on the virtual projection plane is substantially the same as the length measured in the height direction of the original image. Image conversion can be performed.

When correcting in the circumferential direction: p = R (Q + X _p ) · sin (P / R ₀ )
q = Q
By setting the circumferential direction correction as described above, the image is converted so that the length measured in the width direction of the image projected on the virtual projection plane is substantially the same as the length measured in the width direction of the original image. be able to. Further, when the boundary correction is applied to the circumferential direction, the following conversion formula is obtained.
p = arcsin {R (Q + X p) · sin (P / R 0) / R 0} · R 0
q = Q

Further, as described above, even when both horizontal correction and boundary correction are performed, the projected image does not completely match the original image. When comparing the conversion formula in the height direction of G described in the above "paragraph 0035" with the conversion formula in the height direction of F- ¹ that performs horizontal correction and boundary correction described in the above "paragraph 0049", The difference between
v−q = R (Q + X _p ) · {1-cos (P / R ₀ )} · sinφ
It becomes.
Due to this difference, as shown in FIG. 9, the projected image is distorted into a shape in which the left and right are raised with respect to the original image. Such distortions can cause great discomfort as a characteristic of human vision, particularly when this image transformation is applied to circular image elements.

  On the other hand, in the method of the present embodiment, when the original image includes a circular image element, perfect circle correction can be applied. In this case, as shown in FIG. 10, image conversion is performed without applying horizontal correction and boundary correction so that a circular image element maintains a circular shape after projection. This perfect circle correction does not eliminate distortion itself. Since perfect circle correction cannot be compatible with the previous constraint condition (2), the constraint condition (2) is ignored when performing perfect circle correction.

  According to the method of this embodiment in which a planar image serving as the basis of a printing plate is formed by image conversion as described above, a desired line-of-sight angle is set for the print image to be applied to the shoulder of the can body. The plane perpendicular to the line-of-sight angle is defined as a virtual projection plane, and a plane image serving as the basis of the printing plate is formed so that the image projected from the shoulder after molding on the virtual projection plane becomes a desired image. Therefore, using a printing plate that includes this planar image as an image of the shoulder portion, after printing is performed on a cylindrical can body that is an intermediate molded product, the inclined shape is reduced by diameter reduction processing. When the shoulder is molded, when the printed image given to the shoulder after molding is viewed from the direction of the desired line-of-sight angle, the desired image (the image that looks the most uncomfortable and looks optimal) ).

  Note that even if image conversion is performed so that the image projected on the virtual projection plane is completely the same as the original image, the sense of discomfort may not necessarily be reduced due to the characteristics of human vision. In some cases, it may be necessary to perform image conversion in consideration of the visual characteristics of the image, but in the method of this embodiment, before the image conversion process, any of the original images is converted at the conversion area setting stage. What kind of correction is applied to the area is set in advance, whereby it is possible to obtain an image with a smaller sense of incongruity from human visual characteristics.

  That is, in the method of this embodiment, the horizontal correction at the conversion area setting stage converts the image so that the coordinate value in the height direction of each pixel does not depend on the coordinate value in the horizontal direction, and the horizontal line in the original image However, by adopting such horizontal correction, when the image includes a horizontal line, an image that is less uncomfortable due to the characteristics of human vision is used. Obtainable.

  Further, in the method of the present embodiment, the length measured in the circumferential direction of the width of the shoulder image after molding by the boundary correction in the conversion area setting stage is the image at the lower end of the original image at the lower end of the shoulder. And the width of the image projected on the virtual projection plane above the lower end of the shoulder is substantially the same as the width of the image of the same width at the lower end of the shoulder of the original image projected on the virtual projection plane. The images are converted so as to be the same, but by adopting such boundary correction, when images are continuously formed from the can body to the shoulder, the shoulder and the torso The width of the image can be matched at the boundary portion, and the series of images at the boundary between the shoulder portion and the trunk portion can be made smooth and natural.

  In the method of the present embodiment, image elements that are substantially circular on the original image are subjected to image conversion so that the substantially circular shape is maintained on the virtual projection plane by the perfect circle correction at the conversion region setting stage. However, by adopting such perfect circle correction, when the original image includes a circular image element, the circular image element is converted into a circular shape even in the converted image, so that there is no sense of incongruity. Can be formed.

  In the method of this embodiment, the inclined shoulder portion is intended for a can body having a substantially hemispherical shape, but the inclined shoulder portion can also be applied to a can body having a substantially conical surface shape. Further, the present invention is not limited to a smoothly inclined shoulder portion, and even a shoulder portion having a stepped step portion can be applied as long as the shape is axisymmetric with respect to the can axis. In such a case, it is difficult to sufficiently correct the image distortion by the conventional method. However, according to the method of the present embodiment, the shoulder shape is set at the shoulder shape setting stage and image conversion is performed. Therefore, even when the shoulder portion has such a complicated shape, it is possible to form an image having no sense of incongruity when viewed from a desired viewing angle.

  Further, in the method of the present embodiment, when the conversion formula for image conversion is derived, since the basic shape of the can body is axisymmetric, it is expressed by a mathematical expression on the assumption that the shape of the shoulder is axisymmetric. Therefore, it is a conversion formula that can be applied when the shoulder shape is axisymmetric, but even if the shoulder shape is not axisymmetric, conversion can be achieved by appropriately defining the conversion formula. Is possible. Specifically, the case where a vertical groove is formed on the inclined shoulder, the case where a spiral groove is formed, or the case where unevenness is formed is more complicated. It can also be applied to shapes.

As described above, one embodiment of the method for forming a printed image to be applied to the shoulder of the can body of the present invention has been described, but the present invention is not limited only to the specific embodiment as described above, for example, In the above-described embodiment, in the conversion area setting stage, it is possible to set in advance which area of the original image is to be subjected to correction, so that height direction correction and circumferential direction correction are performed, horizontal correction and boundary Although as can be adopted correction and roundness correction, etc. depending on the image of interest, such correction every employed need to have rather name and may require only one of them, as appropriate Needless to say, it can be changed.

The flowchart which shows each step | level in one Example of the method of this invention. Explanatory drawing which shows the relationship between the change of the shape of a can before and behind shaping | molding of a shoulder part, and conversion of the pixel position of a printed image. Explanatory drawing which shows the state which projected the image of the shoulder part on the virtual plane orthogonal to the direction of a gaze angle. Explanatory drawing which shows the concept of image conversion. Explanatory drawing which shows the relationship between each image before conversion and after conversion regarding horizontal correction. Explanatory drawing which shows the relationship between the length of the circumferential direction of the image provided to the shoulder part of the can body, and the width | variety of the image on a virtual projection surface. Explanatory drawing which shows about the width | variety of the image on a virtual projection surface when the width | variety of the circumferential direction is made the same width as an original image. Explanatory drawing which shows boundary correction. Explanatory drawing which shows the distortion of the image at the time of performing image conversion. Explanatory drawing shown about perfect circle correction. Explanatory drawing which shows an example of the plane image obtained by the method of this invention. A simulation that displays an “appearance” image (an image on a virtual projection plane) when the printed image applied to the shoulder of the can body is viewed from the direction of a predetermined viewing angle based on the planar image shown in FIG. Explanatory drawing which shows an image.

Claims (5)

For a can body with an inclined shoulder, a cylindrical can with a bottom, which is an intermediate molded product, on the outer surface of the cylindrical portion that is to be molded into the shoulder by diameter reduction. As a method for obtaining a pre-printed image as a flat image that is the basis of the printing plate, at the original image input stage, the original image before image conversion is read as digital pixel information for each pixel, and the shoulder shape is set. At the stage, the shape of the shoulder after molding is set. At the line-of-sight angle setting stage, the line-of-sight angle, which is an inclination angle with respect to the can axis, is set . At the conversion area setting stage, what correction is applied to which area of the original image. and sets whether applied to a flat virtual projection plane perpendicular to the line of sight angle set by the line-of-sight angle setting step, so that the image projected from the shoulder portion after forming the virtual projection plane has a desired image Based on the digital pixel information of the original image Te By the image conversion, the method for forming a print image so as to form a planar image underlying the printing plate,
By setting the horizontal correction at the conversion area setting stage, each pixel is set so that pixels in the horizontal positional relationship in the original image maintain the horizontal positional relationship in the converted planar image during the image conversion process. A method for forming a printed image to be applied to a shoulder portion of a can body , wherein the image conversion is performed so that the coordinate value in the height direction of the can does not depend on the coordinate value in the horizontal direction . For a can body with an inclined shoulder, a cylindrical can with a bottom, which is an intermediate molded product, on the outer surface of the cylindrical portion that is to be molded into the shoulder by diameter reduction. As a method for obtaining a pre-printed image as a flat image that is the basis of the printing plate, at the original image input stage, the original image before image conversion is read as digital pixel information for each pixel, and the shoulder shape is set. At the stage, the shape of the shoulder after molding is set. At the line-of-sight angle setting stage, the line-of-sight angle, which is an inclination angle with respect to the can axis, is set. At the conversion area setting stage, what correction is applied to which area of the original image. A plane perpendicular to the line-of-sight angle set in the line-of-sight angle setting stage is set as a virtual projection plane, and an image projected from the shoulder portion after molding on the virtual projection plane becomes a desired image. Based on the digital pixel information of the original image Te By the image conversion, the method for forming a print image so as to form a planar image underlying the printing plate,
By setting boundary correction at the conversion area setting stage, the length measured in the circumferential direction of the width of the shoulder image after molding in the image conversion process is the lower end of the original image at the lower end of the shoulder. The width of the image projected on the virtual projection plane is equal to the width of the image at the lower end of the shoulder, and the width of the image of the same width at the lower end of the shoulder of the original image is projected onto the virtual projection plane. The method of forming a print image to be applied to the shoulder portion of the can body , wherein the image conversion is performed so as to be the same . For a can body with an inclined shoulder, a cylindrical can with a bottom, which is an intermediate molded product, on the outer surface of the cylindrical portion that is to be molded into the shoulder by diameter reduction. As a method for obtaining a pre-printed image as a flat image that is the basis of the printing plate, at the original image input stage, the original image before image conversion is read as digital pixel information for each pixel, and the shoulder shape is set. At the stage, the shape of the shoulder after molding is set. At the line-of-sight angle setting stage, the line-of-sight angle, which is an inclination angle with respect to the can axis, is set. At the conversion area setting stage, what correction is applied to which area of the original image. A plane perpendicular to the line-of-sight angle set in the line-of-sight angle setting stage is set as a virtual projection plane, and an image projected from the shoulder portion after molding on the virtual projection plane becomes a desired image. Based on the digital pixel information of the original image Te By the image conversion, the method for forming a print image so as to form a planar image underlying the printing plate,
By setting the height direction correction at the conversion area setting stage, the length measured in the height direction of the image projected on the virtual projection plane during the image conversion process is measured in the height direction of the original image A method for forming a print image to be applied to a shoulder portion of a can body , wherein the image is converted so as to have the same length as the length . For a can body with an inclined shoulder, a cylindrical can with a bottom, which is an intermediate molded product, on the outer surface of the cylindrical portion that is to be molded into the shoulder by diameter reduction. As a method for obtaining a pre-printed image as a flat image that is the basis of the printing plate, at the original image input stage, the original image before image conversion is read as digital pixel information for each pixel, and the shoulder shape is set. At the stage, the shape of the shoulder after molding is set. At the line-of-sight angle setting stage, the line-of-sight angle, which is an inclination angle with respect to the can axis, is set. At the conversion area setting stage, what correction is applied to which area of the original image. A plane perpendicular to the line-of-sight angle set in the line-of-sight angle setting stage is set as a virtual projection plane, and an image projected from the shoulder portion after molding on the virtual projection plane becomes a desired image. Based on the digital pixel information of the original image Te By the image conversion, the method for forming a print image so as to form a planar image underlying the printing plate,
By setting the circumferential direction correction at the conversion area setting stage, the length measured in the width direction of the image projected on the virtual projection plane during the image conversion processing is the same as the length measured in the width direction of the original image. A method for forming a print image to be applied to a shoulder of a can body , wherein the images are converted so as to be the same . For a can body with an inclined shoulder, a cylindrical can with a bottom, which is an intermediate molded product, on the outer surface of the cylindrical portion that is to be molded into the shoulder by diameter reduction. As a method for obtaining a pre-printed image as a flat image that is the basis of the printing plate, at the original image input stage, the original image before image conversion is read as digital pixel information for each pixel, and the shoulder shape is set. At the stage, the shape of the shoulder after molding is set. At the line-of-sight angle setting stage, the line-of-sight angle, which is an inclination angle with respect to the can axis, is set. At the conversion area setting stage, what correction is applied to which area of the original image. A plane perpendicular to the line-of-sight angle set in the line-of-sight angle setting stage is set as a virtual projection plane, and an image projected from the shoulder portion after molding on the virtual projection plane becomes a desired image. Based on the digital pixel information of the original image Te By the image conversion, the method for forming a print image so as to form a planar image underlying the printing plate,
By setting perfect circle correction at the conversion area setting stage, image conversion is performed so that a circular image element on the original image is maintained on the virtual projection plane during image conversion processing. A method for forming a printed image applied to a shoulder portion of a can body, characterized in that it is configured as described above.

Images