JPH0321348B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a doctor used to scrape off printing ink from a synthetic resin intaglio printing plate when printing is performed using a synthetic resin intaglio printing plate. Conventional technology For example, in gravure printing and curved surface printing commonly known as pad printing, an intaglio printing plate is used, which is made of steel, copper, zinc, synthetic resin, etc., and has a concave pattern formed on the surface of the plate material. After filling the printing ink into the printing plate, a doctor (also called a doctor knife or doctor blade) is used to scrape off the excess ink from the printing plate, and the ink in the recesses that will form the image is transferred directly or indirectly to the substrate. I try to do that. Conventionally, the doctors used at this time are those shown in Fig. 1 (schematic perspective view) and Fig. 2.
The one shown in the figure (schematic cross-sectional view) is known. That is, in FIGS. 1 and 2, the doctor 1 is made of metal such as tool steel. Also,
The tip of the blade portion 2, that is, the cutting edge, is machined to be extremely sharp. However, such a doctor 1
As shown in FIG. 3 (schematic side view), the cutting edge is brought into contact with the plate surface of the intaglio printing plate 3 and moved in the scraping direction shown by the arrow, thereby scraping the printing ink on the plate surface. However, such conventional doctors have problems as explained below. That is, since the conventional doctor has a sharp cutting edge, it tends to damage the printing plate and the corner of the boundary between the printing plate and the recesses forming the pattern. However, if the plate surface or corners are damaged, high-quality printing is no longer possible. Naturally, the softer the plate material, the more noticeable the damage will be. Also, since the cutting edge is sharp, it is easy for the blade to spill. When the blade spills, ink remains in streaks on the plate surface, and the plate surface and corners are more likely to be damaged, making high-quality printing more difficult. Furthermore, steel does not have high wear resistance to begin with, so conventional doctors wear heavily and have a short lifespan. Furthermore, in recent years, doctors made of zirconia sintered bodies have been studied. That is, this doctor made of zirconia sintered body maintains the overall shape of the metal doctor shown in FIGS. 1 and 2, but only the material is changed from metal to zirconia sintered body. According to this doctor, zirconia sintered bodies generally have better wear resistance than metals, so
The wear problem mentioned above is somewhat improved. However, since the cutting edge is still sharp, problems such as damage to the plate surface and corners and spillage of the blade still remain, and high-quality printing is still difficult. On the other hand, in European Patent Application No. 61093,
To prevent galvanic corrosion, the blade has a thickness of 1 to 20 μm.
A metal doctor blade formed with an extremely thin ceramic coating is described. Therefore, the cutting edge is rounded with a radius of curvature of 10 to 70 μm. This doctor has a rounded cutting edge, which at first glance seems to prevent damage to the plate and corners. However, this is definitely not the case. In other words, the above-mentioned film is usually formed by coating or thermal spraying, but the film formed by such methods is less dense and has countless pores, which can cause damage to the plate surface and corners. is likely to occur. There are also problems of corrosion of the base metal due to printing ink etc. that enters through the pores and peeling of the coating. Furthermore, although it has a ceramic coating, it is extremely thin to prevent electrolytic corrosion as mentioned above, and is essentially made of metal, so the ceramic coating slightly improves wear resistance. However, the overall mechanical properties such as strength and toughness are almost the same as those made of metal, and there are still concerns about the lifespan. Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned problems of the conventional doctor, to be able to smoothly scrape off ink, and to improve the ability to remove ink from the printing plate and the boundaries between the printing plate and the recesses. Uses synthetic resin intaglio printing plates, which not only prevent damage to the corners and provide high-quality printing, but also have excellent mechanical properties such as strength, toughness, and abrasion resistance, and have a long lifespan. Provide it to the doctor for printing. Means for Solving the Problems In order to achieve the above object, the present invention provides a doctor for printing using a synthetic resin intaglio printing plate, which contains at least 70% of zirconia having a tetragonal crystal structure. It has a blade part made of a zirconia sintered body containing 20 mol% or less of zirconia with a monoclinic crystal structure, and the cutting edge of the blade part is rounded with a radius of curvature of 5 to 100 μm. The invention is characterized by a printing doctor using an intaglio printing plate, in which the center line average roughness of the zirconia sintered body at the cutting edge is 0.3 to 1 μm. To explain this invention in more detail based on one embodiment thereof, in FIG. 4, a doctor 1 has a blade portion 2. As shown in FIG. Further, the tip of the blade portion 2, that is, the cutting edge, is rounded. Further, the doctor 1 has a thickness of 0.03 to 2 mm, preferably 0.05 to 1.5 mm.
It is made of a zirconia sintered body of mm. The overall shape of the cross section of the blade portion 2 may be a so-called wedge shape as shown in FIG. 4, or a so-called rectangular shape as shown in FIG. The cutting edge angle, that is, the angle θ formed by the surfaces of the blade portion 2 forming the cutting edge, can be arbitrarily set within the range of 10 to 90°. In the case of a wedge shape, 10 to 60° is appropriate. The degree of roundness of the cutting edge is 5 to 5 in radius of curvature.
It needs to be 100 μm. Preferably,
It is 10 to 30 μm. By selecting the roundness within this range, damage to the plate surface can be almost completely prevented. The roughness of the zirconia sintered body at the cutting edge must be 0.3 to 1 μm in terms of center line average roughness. By keeping the roughness within this range, the frictional resistance against the plate surface can be extremely reduced, making it possible to prevent damage to the plate surface and extend the life of the doctor. Most preferably, the zirconia sintered body is composed only of zirconia having a tetragonal crystal structure (tetragonal zirconia). It may also contain zirconia with other crystal structures, that is, zirconia with a cubic crystal structure (cubic zirconia) or zirconia with a monoclinic crystal structure (monoclinic zirconia). However, even in that case, the content of tetragonal zirconia must be 70 mol% or more and the monoclinic zirconia content must be 20 mol% or less. That is, tetragonal zirconia transforms into monoclinic zirconia when subjected to stress. When this stress-induced transformation occurs, the applied stress is relaxed by the amount of energy required for the transformation. However, in a zirconia sintered body containing a large amount of tetragonal zirconia of 70 mol% or more, the stress-induced transformation mechanism works sufficiently, a large stress relaxation effect is obtained, and the mechanical strength is greatly improved. Improved strength also means improved toughness and wear resistance. 70 mol% of tetragonal zirconia
If it is less than this, there may be no problem in terms of strength, but the toughness will be insufficient and the cutting edge will be more likely to chip or wear unevenly. On the other hand, the fact that it contains monoclinic zirconia means that microcracks are formed around or near it due to the transformation of the crystal structure from tetragonal to monoclinic. When such a zirconia sintered body is subjected to stress, fracture starting from microcracks may proceed rapidly. Therefore, in this invention, the amount of monoclinic zirconia is limited to 20 mol% or less. . In this way, the tetragonal zirconia is at least 70
A zirconia sintered body containing 20 mol% or less of monoclinic zirconia has excellent mechanical properties such as strength, toughness, and wear resistance, and is extremely excellent as a constituent material for a doctor. For example, the mechanical properties of a zirconia sintered body that contains 70 mol% of tetragonal zirconia, 20 mol% of monoclinic zirconia, and the remainder is cubic zirconia are
The toughness and wear resistance are about twice as high as those of a zirconia sintered body containing 60 mol% of monoclinic zirconia and 30 mol% of monoclinic zirconia with the remainder being cubic zirconia. In terms of strength, it reaches about three times as strong. Here, the amount C _T (mol%) of tetragonal zirconia is determined by the diffraction intensity of cubic zirconia 400 plane obtained by X-ray diffraction of the blade, the diffraction intensity of tetragonal zirconia 004, and the diffraction intensity of tetragonal zirconia 400 It is determined from the diffraction intensity of the surface using the following formula. However, as the diffraction intensity, a correction value based on the Lorentz factor is used. C _T = [(I _T004 + I _T400 ) / (I _C400 + I _T004 + I _T400 )] × 100 Where, I _C400 : Diffraction intensity of cubic zirconia 400 plane I _T004 : Diffraction intensity of tetragonal zirconia 004 plane I _T004 : Square Diffraction intensity of 400 planes of crystalline zirconia The amount C _M (mol%) of monoclinic zirconia is also determined from the following formula in the same manner. C _M = [(I _T111 + I _M111 ) / (I _T111 + I _M111 + I _M111 )] × 100 However, I _T111 : Diffraction intensity of tetragonal zirconia 111 plane I _M111 : Diffraction intensity of monoclinic zirconia 111 plane I _M111 : Diffraction intensity of monoclinic zirconia 111 plane The zirconia sintered body used in the present invention preferably has an average crystal grain size of 0.1 to 5 μm, more preferably 0.1 to 1 μm. That is, when the average crystal grain size is within the above range, the crystals are dense, so that mechanical strength, and eventually toughness and wear resistance, are further improved. Similarly, in order to further improve mechanical strength, toughness, and wear resistance, the porosity P (%) expressed by the following formula
is preferably 1% or less. P=[1-(actual density/theoretical density)]×100 The zirconia sintered body as described above is obtained by dissolving a stabilizer such as itria, calcia, magnesia, etc. in zirconia. Among these, ittria and calcia are preferably used because they can be sintered at relatively low temperatures and can form dense crystals. In that case, itria may be dissolved in a solid solution of 1 to 5 mol%, and calcia may be dissolved in a solid solution of 2 to 9 mol%. Of course, ittria and calcia can also be used in combination, and in that case, it is preferable that they each be within the above ranges and that the sum of the two be 3 to 10 mol%. Now, in this invention, as mentioned above,
The radius of curvature of the cutting edge must be 5 to 100 μm. Table 1 below shows the lengths of zirconia sintered bodies made almost entirely of tetragonal zirconia.
Regarding a doctor with a width of 110 mm, a width of 18 mm, a thickness of 1 mm, a cutting edge angle of 90°, and an average center line roughness of the cutting edge of 0.6 μm,
This shows the results of actual printing using a synthetic resin intaglio printing plate.

[Table] As is clear from Table 1, blades with rounded edges exceeding 100 μm in radius of curvature cause uneven scraping of ink and damage to the plate surface, and are used as printing doctors using synthetic resin intaglio printing plates. Can not.
From Table 1, the preferable upper limit is 30 μm. On the other hand, if the lower limit of the radius of curvature is less than 10 μm, processing becomes difficult, and if it becomes less than 5 μm, it becomes almost impossible.
m, preferably 10 μm. Further, in this invention, the center line average roughness of the zirconia sintered body at the cutting edge must be 0.3 to 1 μm. The following Table 2 shows the length of 110 mm, width of 18 mm, thickness of 1 mm, and cutting edge angle using a zirconia sintered body consisting almost exclusively of tetragonal zirconia.
Regarding a doctor with a radius of curvature of 90° and a cutting edge of 20 μm,
This shows the results of actual printing using a synthetic resin intaglio printing plate.

[Table] As is clear from Table 2, when the centerline average roughness of the zirconia sintered body at the cutting edge exceeds 1 μm, uneven scraping of ink and damage to the plate surface are significant, and synthetic resin intaglio printing plates cannot be used. It cannot be used as a printing doctor. On the other hand, the lower limit of roughness is set to 0.3 μm in consideration of ease of processing. The doctor of the present invention can be manufactured by various methods. Next, a preferable example will be explained. That is, first, zirconyl oxychloride having a purity of 99.9% or more and yttrium chloride and/or calcium chloride are mixed at a desired molar ratio to prepare an aqueous solution. Next, the above aqueous solution is gradually heated to about 200°C to drive off the water, and then heated at a rate of about 50 to 150°C/hour.
It is heated to 1000°C and maintained at that temperature for several hours to obtain a mixed powder of zirconia and ittria and/or calcia. Next, after grinding and drying the above mixed powder, approx.
It is calcined at 1000°C for several hours, pulverized, an organic binder such as polyvinyl alcohol is added, granulated, and dried to obtain a raw material powder with an average particle size of about 80 μm. Next, the raw material powder is put into a molding machine to obtain a doctor-shaped molded body. Next, the above molded body is heated at a rate of about 100 to 200℃/hour.
It is heated to 1000°C, further heated at a rate of 50 to 200°C/hour to about 1550°C, and kept at that temperature for several hours for firing. Next, the fired body is heated at 200 to 300℃/up to approximately 1000℃.
The sintered body is then cooled at a rate of 100 to 200°C/hour from about 1000°C to about 500°C, and further cooled to room temperature to obtain a sintered body. The thus obtained doctor-shaped zirconia sintered body is processed using a grinder or the like, and at the same time, the blade portion and the cutting edge are processed. In the above, an injection molding method or a rubber press method may be used instead of the molding method, and the molded product obtained thereby may be machined and fired. Moreover, if the compact is fired at a relatively low temperature of 1300 to 1500°C and then sintered at 1200 to 1450°C under a pressure of 500 to 3000 Kg/cm ² , the crystals can be made more dense. Results of the Invention The doctor of this invention used for printing using a synthetic resin intaglio printing plate is made of zirconia sintered body, has a rounded cutting edge, and has a radius of curvature of 5 to 100 μm, preferably 10 μm. ~30μm, and the centerline average roughness of the zirconia sintered body at the cutting edge is 0.3~1μm,
Not only does the rubbing against the plate surface become extremely smooth, allowing printing ink to be scraped off evenly, but
There is almost no need to worry about damaging the printing plate or damaging the corners of the boundary between the printing plate and the recesses that form the pattern when scraping. Preventing damage to the plate surface and corners also extends the life of the printing plate. In addition, such a rounded cutting edge is thick, hard to chip, and contains at least 70 mol% of tetragonal zirconia, but monoclinic zirconia
Since it uses a zirconia sintered body with a content of less than 20 mol%, which has excellent strength, toughness, and wear resistance, there is almost no worry about blade spillage, etc., and it also prevents uneven wear of the cutting edge. Now you can
Damage to the printing plate and the above-mentioned corner damage can be prevented, and it is also possible to prevent streaks of printing ink from remaining on the printing plate. Therefore, by using the doctor of the present invention, it becomes possible to perform high-quality printing over a long period of time. From the above features, the doctor of this invention is the most suitable for printing using a relatively soft synthetic resin intaglio printing plate, such as a photosensitive synthetic resin intaglio printing plate, among synthetic resin intaglio printing plates. Are suitable. A photosensitive synthetic resin intaglio printing plate is a synthetic resin that has a photosensitive peak in the ultraviolet region, preferably around 360 nm, and is cured by light of such a wavelength, and is coated on a synthetic resin film or metal plate for 5 to 50 minutes. It is like applying a film to a thickness of 70 μm, exposing the coated surface with a positive film, and then making a plate using a developer that dissolves or swells only the exposed areas. In addition, the doctor of this invention has a diameter of 5 to 100 μm,
Preferably, the rounded cutting edge with a radius of curvature of 10 to 30 μm not only allows for smooth movement from the plate surface, but also contains at least 70 mol% of tetragonal zirconia, but not more than 20 mol% of monoclinic zirconia. Since a zirconia sintered body with excellent wear resistance is used, wear caused by rubbing against the plate surface, especially initial wear, is greatly reduced, extending the life. Furthermore, since the doctor of this invention uses a zirconia sintered body that never rusts because it is essentially an oxide, there are inconveniences such as damage to the plate surface and damage to the corners mentioned above due to rust. It is possible to prevent inconveniences such as streaks of printing ink remaining on the plate surface due to a decrease in the straightness of the cutting edge, and not only the printing quality is improved but also the lifespan is further extended.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams showing a conventional doctor, with Figure 1 being a perspective view and Figure 2 being a cross-sectional view.
FIG. 3 is a schematic side view showing how a doctor is used to scrape off printing ink from a printing plate, and FIGS. 4 and 5 are schematic cross-sectional views showing different embodiments of the doctor of the present invention. be. 1: Doctor, 2: Blade, 3: Intaglio printing plate.

Claims (1)

[Claims] 1 A doctor for printing using a synthetic resin intaglio printing plate, containing at least 70 mol% of zirconia with a tetragonal crystal structure, but 20 mol% of zirconia with a monoclinic crystal structure. It has a blade part made of a zirconia sintered body as follows,
Printing using an intaglio printing plate, characterized in that the cutting edge of the blade portion is rounded with a radius of curvature of 5 to 100 μm, and the average roughness of the center line of the zirconia sintered body at the cutting edge is 0.3 to 1 μm. Doctor for.