KR20200108740A - static-removed printing method - Google Patents

Abstract

An electrostatic gravure printing method consists of paper having a moisture content of 4-6% and a surface resistivity of 1.0×109-9.0×109Ω/m^2 in an environment of 23°C±1°C and 50%±2% RH. Therefore, the method can limit the occurrence of missing dots in a printed material and eliminate static disturbances such as the difficulty of turning pages in the bound printed material and the unpleasant noise generated by discharge when the pages are turned and separated.

Description

Static-removed printing method

The present invention generally relates to a technique for preventing damage to a printed product due to static electricity, and in particular, to a printing method for preventing various damage due to static electricity in a stack of a plurality of electrostatic printed paper sheets.

As is well known in the art, in rotogravaure printing, concave portions (cells) of dots (dots) displaying characters or pictures installed on the outer surface of the gravure plate cylinder are filled with ink. While the continuous printing paper is pressed against the outer circumferential surface of the gravure plate cylinder by the stamping cylinder, the continuous printing paper passes through the outer circumferential surface of the gravure plate cylinder, so that the ink in the cells is transferred to the contact surface of the printing paper, so that Text or pictures are developed.

Static electricity is applied to facilitate ink transfer from inside the cells of the gravure plate cylinder to the printing paper. Therefore, in the electrostatic gravure printing process, the continuous paper supplied from the paper roll is pressed against the surface of the gravure plate cylinder by the pressing cylinder that is lost while passing between the gravure plate cylinder and the stamping cylinder. The thickened printing ink is transferred to the paper surface, resulting in printing.

Gravure printing inks are composed of electrically neutral particulates. In electrostatic printing, an electric field is generated in the nip between the plate cylinder and the stamping cylinder in order to achieve effective transfer of ink from the cells of the plate cylinder to the surface of the substrate. Therefore, it is advantageous that particles of printing ink in the cells of the plate cylinder passing through the electric field are transferred from the cells to the ground surface by the force generated in the electrostatic field. Since the paper and ink pass through the electrostatic field, the printed surface of the paper subjected to electrostatic printing is negatively and positively charged non-uniformly.

In the automatic manufacturing process of magazines, catalogs and the like, continuous paper is printed on both sides, cut and folded into signatures. Then, in order to form a single book, a certain number of folding sheets are stacked in page order, and both sides are pressed to firmly combine into a single book and transferred to a bookbinding process, and finally the stacks are formed into books.

In the book manufactured by the above-described method, since facing pages are attached to each other due to electrostatic force, when readers turn the pages, each facing page cannot be easily separated. In this case, if readers omit the attached pages or skip past the attached pages without an effort to remove the attached pages, there will be pages that the readers have not read, especially in the case of sales catalogs. Also, crackling sounds when turning pages will offend readers. This discomfort is considered to be due to so-called electrical discharges induced by separation.

In a book manufactured by the above-described method, positive and negative charges due to electrostatic printing are unevenly convective on the printing surface of each page. Therefore, it is considered that the electrostatic force of f=kq1q2/r2 is small between the facing pages of a book according to Coulomb's law. Therefore, when the convective charge increases, the influence of the static power also increases. In addition, it is believed that the facing pages of the book form a single capacitor composed of a charged printing surface with air gaps posted between the pages locally. As is well known in the art, when specifying the dielectric constant of air as "ε", the space between facing pages as "d", and the facing surface area as "S", the amount of this capacitor "C" is: It is expressed as

Equation 1

In addition, when the charge of the capacitor is defined as "Q", the potential difference "V" between facing pages is expressed as in Equation 3 below from Equation 2, which is well known.

Equation 2

Equation 3

As described above, since each page of the book is pressed and tightly bound in the bookbinding process, "d" in Equation 1 is decreased to increase "C", and therefore, in Equation 3, it is applied during the printing process. "V" decreases as "C" increases because "Q" is fixed according to the voltage being applied. However, when readers turn the pages of the book, the facing pages are opened so that "d" increases rapidly, and thus "C" in Equation 1 rapidly increases. As a result of this, the voltage "V" between opposing pages constituting the capacitor is rapidly increased according to Equation 3, and the electric charge causes a so-called peeling discharge between these pages. This will be the reason for the above-described unpleasant sound.

또는 그 이상의 표면 저항률을 갖는다. 그러나, 만일 이러한 지 사에 의하여 정전 인쇄가 이루어진다면 전하(electric charge)로 인하여 상술한 바와 같은 정전기 장애가 발생할 것이다. 지의 표면 저항률이 감소되어 전하가 감소되고 정전기가 급하게 감쇠되기 때문에 지의 표면 도전성 이 증가되고 상술한 닙부의 자계 강도가 약해진다. 결과적으로, 인쇄 표면 상에 소위 "누락된 도트(missing dot)"가 발생하 기 쉽고 인쇄물의 품질이 저하된다. 최근의 상품 카탈로그에서, 페이지의 수가 증가되는 경향이 있고 인쇄, 운송비 면에 서 얇은 지를 사하는 요구가 일어나고 있다. 그러나, 지의 견고성이 약하기 때문에 이러한 얇은 지는 인쇄물의 페 이지를 넘기는 과정에서 전하의 영향을 크게 받는다.Paper commonly used for gravure printing is usually 1010Ω/

Or higher surface resistivity. However, if electrostatic printing is performed by such a branch, an electrostatic failure as described above will occur due to electric charge. Since the surface resistivity of the paper is reduced, the charge is reduced, and static electricity is abruptly attenuated, the surface conductivity of the paper is increased, and the magnetic field strength of the nip portion is weakened. As a result, so-called "missing dots" are liable to occur on the printing surface and the quality of the print is deteriorated. In recent product catalogs, the number of pages tends to increase, and there is a demand for thinness in terms of printing and shipping costs. However, since the firmness of the paper is weak, such thin paper is greatly affected by the electric charge in the process of turning the page of the printed material.

The present invention suppresses the occurrence of missing dots on the printing surface by refusing to have a surface resistivity in a predetermined range in electrostatic gravure printing, and prevents the above-described electrostatic failure caused by convection of electric charges in electrostatic printing.

, 바람직하게는 1.0×109 내지 7.0×109Ω/

,가장 바람직하게는 1.0×109 내지 5.0×109

인 지가 사된다. 이러한 표면 저항률 값들은 지의 수분 함유율이 4% 내지 6% 범위 내의 조건하에 측정된 것이다. 수분 함유율은 온도 23℃±1℃, RH(상대 습도) 50%±2%의 환경 조건 하에서 측정되었다.According to the method of the present invention, the surface resistivity is 1.0×109 to 9.0×109Ω/

, Preferably 1.0×109 to 7.0×109Ω/

, Most preferably 1.0×109 to 5.0×109

Recognition is killed. These surface resistivity values are measured under conditions in which the moisture content of the paper is in the range of 4% to 6%. The moisture content was measured under environmental conditions of a temperature of 23°C±1°C and 50%±2% of RH (relative humidity).

Fig. 1 is a diagram showing the relationship between the surface resistivity of a printing paper and a total potential of a printed product obtained from the paper.
Fig. 2 is a diagram showing the relationship between the surface resistivity of printing paper and the intensity of crackle of a printed material obtained from the paper.

In general, paper has a structure in which a coating layer is applied on both sides of a paper subjected to a surface sizing treatment after a papermaking process. The above-described surface resistivity preferred in the present invention can be realized by adding an inorganic salt to a sizing agent. As the sizing agent, those known in the art may be used. As the inorganic salt, various types and amounts capable of realizing the surface resistivity within the above-described range can be appropriately selected. For example, by preparing a paper having a thickness of 50 μm to 55 μm subjected to surface sizing with a sizing agent containing sodium chloride in a ratio of 0.15 g to 0.2 g per 60 g of paper, the surface resistivity of 1.0×109 to 9.0×109Ω You can get paper with

In order to select the range of the surface resistivity, the measurement of the total potential and the intensity of the page turning sound (the sound generated when turning the pages of a printed book) was obtained by electrostatic gravure printing on various types of paper with different surface resistivity. It was done on print. The results are shown in FIGS. 1 and 2. This measurement was made under environmental conditions of a temperature of 23°C±1°C and RH (relative humidity) of 50%±2%.

In order to perform the above-described measurement, 200 rolls of continuous paper having a quantity of 64 g/m2, a thickness of 55 μm, a width of 2,450 mm and a length of 25,000 m were prepared. Of these rolls, 100 rolls were prepared from paper (hereinafter abbreviated as "natrium chloride") that was added with 0.2 g of sodium chloride per 60 g of paper and was surface-sized with a mixed sizing agent. The other 100 rolls were prepared from general gravure printing paper (hereinafter, abbreviated as "free paper") to which sodium chloride was added and surface-sized with an unmixed sizing agent.

Surface resistivity was measured using a resistivity meter manufactured by Mitsubishi Chemical Corporation for each of 6 sheets of A4 paper cut just before printing from a portion near the outermost circumference of each 200 rolls immediately before printing, and the average value of the 6 measurements It is evaluated by the surface resistivity of the paper of each roll.

The moisture content of the paper was determined by cutting about 1 g of six paper specimens from the portion of each roll from which the six papers were cut; Weigh each specimen while drying the specimen in an oven at 100° C.; The condition in which the weight is no longer changed is regarded as an absolute dry condition; It is determined by calculating the moisture content according to the following equation.

[Specimen weight (g)-Specimen weight (g) under absolute dry conditions] / Specimen weight (g)

For the measurement, an electronic moisture meter manufactured by Shimadzu Corporation was used. For each roll, the average value of the moisture content of the six paper pieces is evaluated as the moisture content of each paper roll. It was found that all rolls had a moisture content in the range of 4% to 6%.

The total potential and the page turning sound intensity are printed by electrostatic gravure printing on the entire 200 paper rolls under the same conditions; 20,000 copies of the AB edition product catalog of 72 pages were produced for each roll; Among them, 3 parts were arbitrarily selected and measurement was carried out.

Regarding the total potential, for each of the three prints to be measured selected from the prints of the rolls, the measurer turned the pages sequentially from the first page by hand. The measurer should be placed 10cm away from the printout to be measured and

The maximum value of the electric potential generated during steaming was measured, and the sum of the absolute values of the measured values of 35 measurements for each printed material was calculated. Thereafter, the average value of each sum of the absolute values of the three prints was determined as the total potential of the prints of each roll. For the measurement, a potential meter manufactured by Shiseido Electrostatic Co., Ltd. Solvent was used.

Regarding the intensity of the page turning sound, along with the above-described total potential measurement, the measurer listened to the sound generated every time the page of each printout of the three-part printout was turned, and the volume was set to loud, medium, low, and silent. Classified. The measurer assigned evaluation values of 3, 2, 1 and 0 for each classification and calculated the total evaluation value for each print. The average value of the total evaluation values of each of the three prints is determined as the page turning sound intensity of the prints of each roll.

In the graphs shown in FIGS. 1 and 2, white circles represent measurement values for 100 rolls of sodium chloride, and black circles represent measurement values for 100 rolls of non-garden described above. Since some of the measured values are weighted approximately each other, the number of each circle is 100 or less. The horizontal axis represents the log scale.

No differences were observed by visual inspection in all the prints to be measured, especially in prints of papers with low surface resistivity, in terms of occurrence of missing dots compared to other prints.

의 표면 저항률을 갖는 지의 경우, 인쇄물의 총전위와 책장 넘김 소리 강도의 값은 상기 범위를 초과하는 표면 저항률을 갖는 용지, 특히 대부분의 무가 지의 총전위와 책장 넘김 소리 강도보다는 적어 실질적인 장애가 발생하지 않는다. 1.0×109 내지 7.0×109Ω/

의 표면 저항률을 갖는 용지의 경우에, 인 쇄물의 총전위와 책장 넘김 소리 강도의 값은 거의 모든 무가 지의 총전위와 책장 넘김 소리 강도보다는 적으며, 1.0×109 내지 5.0×109Ω/

의 표면 저항률을 갖는 지의 경우에, 인쇄물의 총전위와 책장 넘김 소리 강도의 값은 실질적 으로 무시할만 한다. 예를 들어, 8.6kV의 총전위, 0.5V의 최대 측정 전위 및 3.3의 페이지 넘김 소리 강도를 갖기 위하여 결정된 4.8×109Ω/

의 표면 저항률을 갖는 용지로부터의 인쇄물(72페이지의 카탈로그)의 예는 페이지 넘김 측정에서 단 일 인쇄물당 평가치가 1인 페이지 넘김 소리를 3 또는 4회 발생시켜 거의 불쾌감을 야기하지 않으며 페이지의 부착을 야기 하지 않는다.As is apparent from the above, there is a relationship between the paper surface resistivity before printing and the total potential of the printed material using the corresponding paper and the sound intensity of turning over the bookshelf, and 1.0×109 to 9.0×109Ω/

In the case of paper having a surface resistivity of, the total potential of the printed material and the value of the sound intensity of turning over a bookshelf are less than that of the paper having a surface resistivity exceeding the above range, in particular, the total potential and the intensity of the sound of turning over a bookcase, so that practical obstacles do not occur. . 1.0×109 to 7.0×109Ω/

In the case of paper having a surface resistivity of, the total potential of the printed material and the value of the sound intensity of turning over a bookshelf are less than that of almost all the total potentials and the sound intensity of turning over a bookshelf, and 1.0 × 109 to 5.0 × 109 Ω/

In the case of paper having a surface resistivity of, the total potential of the print and the value of the volume of the bookshelf turning is practically negligible. For example, 4.8×109 Ω/determined to have a total potential of 8.6 kV, a maximum measured potential of 0.5 V, and a page turning sound intensity of 3.3.

An example of a print (catalog on page 72) from a paper having a surface resistivity of 3 or 4 times a page turning sound with an evaluation value of 1 per single print in the page turning measurement, causing almost no discomfort and causing the page to stick. I never do that.

As described above, the printing method of the present invention not only suppresses the occurrence of missing dots in printed matter, but also eliminates electrostatic disturbances, it has excellent utility in gravure printing using thin paper as a fabric.

Claims (3)

Under environmental conditions of temperature 23°C±1°C and RH (relative humidity) 50%±2%, it has a moisture content of 4% to 6% and a surface resistivity of 1.0×109 to 9.0×109Ω to perform electrostatic printing. Gravure printing method, characterized in that.
The gravure printing method according to claim 1, wherein the paper is surface-sized with a sizing agent containing 0.15 g to 0.2 g of inorganic salt per 60 g of paper.
3. The gravure printing method according to claim 2, wherein the inorganic salt is sodium chloride.

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