JPH08197711A - Doctor blade - Google Patents

Abstract

PURPOSE: To improve wear resistance by coating the surface of a plate-like parent body formed with a material with elasticity with a wear-resistant layer formed of a harder material than the parent body, and specifying the spring const. of a doctor blade and Vickers hardness of the wear-resistant layer respectively to scrape off surely ink by following the rotation of a plate cylinder. CONSTITUTION: A doctor blade 1 consists of a plate-like body material 11 formed of a material with elasticity and a wear-resistant layer 12 with which the surface of the body material is coated. In addition, the spring const. of the doctor blade 1 is 2.5-5.0N/mm. When the value is under 2.5N/mm, as the blade can not completely scrape the ink on a plate cylinder, doctor stripes are generated and when it exceeds 5.0N/mm, as the doctor blade 1 can not follow the vibration under a tightly contact condition, leakage of scraping of the ink occurs. As the wear-resistant layer 12 of the doctor blade 1, a material harder than the parent body 11 is used and the Vickers hardness is in the range of 1,000-3,800. As the method for coating the body material 11 with the wear-resistant layer 12, a CVD method and a PVD method are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a doctor blade used for gravure printing or the like, and more particularly to a doctor blade capable of withstanding long-term use.

[0002]

2. Description of the Related Art Generally, an intaglio printing apparatus is constructed so that a doctor blade is pressed against a circumferential surface of a plate cylinder with a predetermined pressing force to remove ink adhering to a non-image area of the plate cylinder. ing. The purpose of using the doctor blade is to completely remove the excess ink adhering to the non-image area of the plate cylinder while leaving a predetermined amount of ink in the image area. Since the tip edge of such a doctor blade constantly slides on the plate cylinder, abrasion resistance is required. Particularly in recent years, there has been a demand for doctor blades having high abrasion resistance and high printing speed and high-volume printing.

However, a conventional doctor blade uses a steel plate and has low wear resistance. Therefore, in order to improve wear resistance, doctor blades having a hard coating on the surface have been developed. For example, special table Sho 62-503085
In order to improve wear resistance, the doctor blade shown in No. 3 has a hard base material laminated on the surface of the doctor blade by wire flame spraying or plasm spraying. In this method, a smooth layer cannot be laminated on the surface of the doctor blade, and the surface becomes uneven. If the surface of the doctor blade has an uneven shape, the ink cannot be sufficiently scraped off, and a printing defect called a doctor streak occurs, which leads to a defective printed matter. Therefore, the surface needs to be polished.

Further, since the hard coating is provided only on a part of the doctor blade, corrosion may occur from the part not coated with the wear resistant layer and the doctor blade may be broken.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to maintain a predetermined hardness for removing ink adhering to the non-image area of the plate cylinder, but to have no irregular shape on the surface of the doctor blade. An object of the present invention is to provide a doctor blade having abrasion resistance that follows the rotation of the plate cylinder.

[0006]

Means for Solving the Problems The inventors of the present invention have completed the present invention as a result of earnest efforts for the above problems.

According to the present invention, there is provided a plate-shaped base body made of a material having elasticity, and a wear resistant layer formed on the surface of the base body and made of a material harder than the base material. A doctor blade having a spring constant of 2.5 to 5.0 N / mm and a Vickers hardness of the wear resistant layer of 1000 to 3800 Hv.

Further, the present invention also provides a doctor blade in which the entire doctor blade is covered with a wear resistant layer formed of a material harder than the base material.

[0009]

[Operation] The spring constant of the doctor blade is 2.5-5.0 N / mm
By doing so, the ink can be reliably scraped off following the rotation of the plate cylinder. Further, by coating the surface with a material harder than the base material, the wear resistance is improved and the life of the doctor blade is extended.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings.

FIG. 1 shows a specific example of an intaglio printing apparatus using the doctor blade of the present invention. In FIG. 1, the doctor blade 1 of the present invention is held laterally of the plate cylinder 3 by a holding mechanism 2. An ink supply tank 4 is provided below the plate cylinder, and ink 5 is stored in the ink supply tank. When the plate cylinder 3 rotates, ink adheres to the periphery of the plate cylinder 3, and the ink adhered to the non-image area of the plate cylinder is removed by the doctor blade 1 pressed against the plate cylinder at a predetermined angle and pressing force. It is configured to remove. An impression cylinder 6 is rollingly contacted above the plate cylinder 3 and paper sheets 7 supplied between them.
The ink held in the image area is transferred to.

FIG. 2 is a sectional view showing a specific example of the doctor blade of the present invention. In FIG. 2, the doctor blade 1
Is composed of a plate-shaped base 11 made of an elastic material and a wear resistant layer 12 attached to the surface of the base. The mother body is ground so that both edges thereof are thinner, and blade edges 13a and 13b are formed.

As the base material of the doctor blade of the present invention, a material having elasticity is preferable. For example, as a material of a conventional doctor blade such as a heat-treated metal material such as carbon steel, stainless steel, titanium alloy or various composite materials. Any known one can be used.

The base material has a thickness of 100 to 200 μm.
It is a thin plate shape and is cut so that the length is 750 to 2000 mm, and both edges are further ground to have a thickness of 40 to 150 μm and a length of 0.1 to 0.5 mm to form a cutting edge portion. It is preferably formed.

When the thickness of the base body of the doctor blade is less than 100 μm, a spring constant of 2.5 N / mm or more cannot be obtained,
Since the ink on the plate cylinder cannot be completely scraped off, doctor streaks occur, which is not preferable. On the other hand, the thickness is 200μ
If it exceeds m, the rigidity of the plate cylinder will be too great, and the plate cylinder will be worn too much. Also, since the spring constant will exceed 5.0 N / mm and it will be too large, the doctor blade will not follow it while sticking to the runout of the plate cylinder It is not preferable because a defect such as scratching and leakage of ink occurs.

Further, when the thickness of the cutting edge portion is thinner than 40 μm, defects such as breakage occur when pressed against the plate cylinder, ink cannot be sufficiently scraped off, and doctor streaks are generated to cause defects in printed matter. Invite. On the other hand, when the thickness exceeds 150 μm, on the contrary, the plate cylinder wears more quickly and the life of the plate cylinder is shortened.

A material harder than the base material is used for the wear resistant layer of the doctor blade of the present invention, and the Vickers hardness is 1000 to 38.
It is preferably in the range of 00 Hv. Examples of such a material include TiN, ZnO ₂ , TiC, TiCN,
Al ₂ O ₃ , W ₂ C, CrN, TiAlN, SiO ₂ , Ti
Examples thereof include ceramic materials such as O ₂ and hard metal materials such as Mo and Ni.

As a method of coating the wear resistant layer on the base material, a CVD method, a PVD method, a low pressure plasma spraying method or the like can be used, and a CVD method or a PVD method is particularly preferable. When coated by CVD method or PVD method,
The roughness of the coating surface is much smaller than one-fifth or less as compared with the thermal spraying method and the like, and there is an advantage that doctor streaks do not occur.

The coating thickness of the wear resistant layer is preferably 5 to 50 μm. If the wear-resistant layer has a coating thickness of less than 5 μm, predetermined wear resistance cannot be obtained, which is not preferable. Further, if the coating thickness of the wear resistant layer exceeds 50 μm, the spring constant of the doctor blade itself becomes too high, and the plate cylinder wears, which is not preferable.

Next, a predetermined doctor blade (steel plate: EBE
RLE (Germany, thickness 150 μm) coated with the following hard coating by the CVD method (Test Nos. 1 to 1)
5) was evaluated. The evaluation results are shown in Table 1.

The Vickers hardness in the table was measured with a Vickers hardness meter. The spring constant of the doctor blade of the present invention was measured by the following method. A schematic diagram is shown in FIG. First, the support bases 22 are placed under the roots of the two blade tips of the doctor blade 1. Then, a load: P is applied from above the center point of the doctor blade 1 in the longitudinal direction by the indenter 23, the deflection of the doctor blade 1 at that time: δ is measured, and the spring constant from P / δ:
I asked for k.

K = P / δ = (4Ebt ³ ) / l ³ where l is the distance between supporting bases (mm), b is the width of the doctor blade (mm), and t is the thickness of the doctor blade (mm). E represents Young's modulus. In the present invention, the distance l between the supports is
Was 30 mm and the width b of the doctor blade was 25 mm.

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Abrasion resistant layer ──── ───────────── Test No. Coating material Thickness Vickers hardness Spring constant evaluation ^a) (μm) (Hv) (N / mm) ───────────────────────────── ─────── 1 ZrO ₂ 2 1100 2.9 A 2 ZrO ₂ 5 1100 3.7 B 3 ZrO ₂ 10 1200 1200 4.1 B 4 ZrO ₂ 14 1150 4.3 B 5 ZrO ₂ 20 1150 4. 8 B 6 ZrO ₂ 60 1150 5.3 C 7 Al ₂ O ₃ 10 1300 4.5 B 8 ZrO ₂ 10 900 3.9 D 9 Al ₂ O ₃ 10 1100 4.2 B 10 TiN 10 1100 4.4 B 11 CrN 5 2100 2.5 B 12 TiC 10 3800 3.9 B 13 TiCN 10 2500 3.9 B 14 TiAlN 5 2500 3.9 B 15 W ₂ C 10 2200 3.9 B ━━━━━━━━━━━━━━━━━━ ━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━ a) Evaluation criteria A: Since the thickness is thin, there was a problem in wear resistance.

B: Abrasion resistance was also good, and no doctor streak was generated.

C: There was no problem in wear resistance, but since the spring constant became too high, the life of the plate cylinder was shortened.

D: The wear resistance of the doctor blade was poor and the life was short.

[0027]

By using the doctor blade of the present invention, the wear resistance is improved. Further, by applying the CVD method and the PVD method to the formation of the wear resistant layer of the doctor blade, the unevenness of the surface was eliminated and the generation of the doctor stripe was eliminated. Furthermore, by coating the entire doctor blade with a wear resistant layer, corrosion of the doctor blade did not occur and the life of the doctor blade was extended.

[Brief description of drawings]

FIG. 1 is a specific example of an intaglio printing apparatus using a doctor blade of the present invention.

FIG. 2 is a sectional view showing a specific example of a doctor blade of the present invention.

FIG. 3 is a schematic diagram showing a method for measuring a spring constant of a doctor blade.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Doctor blade 2 Holding mechanism 3 Plate cylinder 4 Ink supply tank 5 Ink 6 Pressure cylinder 7 Paper sheet 11 Base 12 Wear resistant layer 13a Blade tip 13b Blade tip 22 Support base 23 Indenter

Claims (2)

[Claims] 1. A doctor blade comprising a plate-shaped base body formed of a material having elasticity and a wear-resistant layer formed on the surface of the base body and formed of a material harder than the base material. And the spring constant of the doctor blade is 2.5-5.0 N / m
m, and the Vickers hardness of the wear resistant layer is 1000 to
Doctor blade that is 3800 Hv. 2. The doctor blade according to claim 1, wherein the entire doctor blade is covered with a wear-resistant layer formed of a material harder than the base material.