JPH0938565A - Doctor blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a load applied on a doctor blade and to make the service life longer by forming at least the end edge part with single crystal alumina in the doctor blade for applying or scraping another substance on or from the surface of a sheet-like body. SOLUTION: A doctor blade 1 used in a process for applying a resin on the surface of a paper 30, etc., is prepd. by bonding a sheet-like body 3 consisting of single crystal alumina on the side face part of the end of a supporting plate 2 and has an edge 3a on its apex. The supporting plate 2 comprises a metal material such as a height speedsteel and it can be bent while it is used if the thickness is made at most 1mm. In addition, the thickness of the plate-like body 3 consisting of single crystal alumina is also made at most 1mm. When it is used, a coating agent 31 is placed on the paper 30 and the doctor blade 1 is moved to coat the surface of the paper 30 with the coating agent 31 by spreading the coating agent 31 thereon by the edge 3a while it is sticked.

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 coating or scraping another substance on the surface of a sheet-shaped body.

[0002]

2. Description of the Related Art Doctor blades have been used in various fields.

For example, a step of applying a resin to the surface of paper, or a step of applying a heat-sensitive agent to form a thermal paper, a step of coating the surface of a sheet-like body other than paper with a resin, and the like, attaching to the plate surface of a printing plate. A doctor blade is used in the process of scraping off the excess ink, the process of applying a ceramic slurry on a sheet with a certain thickness to produce a green sheet, the process of molding rubber, food, etc. into a sheet shape, etc. .

Of these, in the step of applying the resin to the surface of the paper, as shown in FIG. 5, the coating agent 3 placed on the paper 30 is used.
1 is extended by the blade 40.
The blade 40 is a plate-like body having an edge 40a at the tip, a thickness of 1 mm or less, a width of about 10 cm, and a total length of 7 to 7.
It is about 9 m in size and is made of a metal material such as high-speed steel. It is slightly bent and moved in the direction of the arrow to spread the coating agent 31 while closely adhering the coating agent 31 to the surface of the paper 30 at the leading edge 40a. It is designed to be applied.

[0005]

However, since the edge 40a of the blade 40 made of the metal material cannot be uniformly applied due to abrasion, the blade 40 must be replaced after about two hours of use, which is extremely inefficient. It was a thing.

Therefore, as disclosed in Japanese Patent Publication No. 2-36771, there is a blade 40 having a hard film of tungsten carbide (WC) or the like sprayed on its side surface at the tip, but the hard film is easily peeled off during use. It could only be used for about 80 hours.

Further, as shown in Japanese Patent Publication No. 2-51398 and Japanese Utility Model Laid-Open No. 7-560, at least the tip portion of the blade 40 was made of zirconia ceramics, but it was still used for about 120 hours. It was only possible, and it was not satisfactory in terms of life.

[0008]

Therefore, the present invention is characterized in that at least the tip edge portion of the doctor blade is formed of single crystal alumina.

Further, the present invention is characterized in that blades are arranged in multiple stages along the traveling direction, and at least the tip edge portion of the blade at the rearmost portion is formed of single crystal alumina.

That is, according to the present invention, by using the single crystal alumina which has significantly higher hardness and corrosion resistance than ceramics such as zirconia, the wear resistance is excellent and the life can be extended.

Further, by arranging the blades in multiple stages, the front blade can be smoothed with the coating agent, and the rear blade can finish the coating, so that a more uniform thickness can be achieved and the load applied to each blade can be reduced. It can be made lighter and its life can be extended.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

In the doctor blade 1 shown in FIGS. 1 and 2 (a), a plate-like body 3 made of single-crystal alumina is bonded to the side surface of the tip of a support plate 2 with an adhesive 4, and the edge 3a is attached to the tip thereof.
It is provided with.

As another embodiment, as shown in FIG. 2B, a step portion 2a is formed on the tip side surface portion of the support plate 2, and a plate-like body 3 of single crystal alumina is attached to the step portion 2a. Can be easily positioned. Alternatively, FIG. 2 (c)
As shown in (d), the plate-like body 3 of single crystal alumina may be bonded to the end surface of the support plate 2. In either case,
At least the leading edge 3a may be formed of single crystal alumina.

When this doctor blade 1 is used, for example, in the step of coating the surface of paper with resin, a coating agent 31 is placed on the paper 30 and the doctor blade 1 is moved in the direction of the arrow as shown in FIG. Then, the coating agent 31 can be spread and applied while closely adhering the coating agent 31 to the surface of the paper 30 at the leading edge 3a.

The support plate 2 is made of a metal material such as high-speed steel or ceramics such as zirconia. It is preferable that the support plate 2 be thin so as to have a thickness of 1 mm or less so that it can be bent during use.

Similarly, the plate-like body 3 made of single crystal alumina has a thickness of 1 mm or less, and its tip has an angle of 8 mm.
It has an edge 3a of about 0 to 120 °. When the doctor blade 1 is long, the plate-shaped body 3 may be divided in the lengthwise direction and formed, and bonded to the support plate 2 so that the edges 3a are aligned.

Further, the plate-like body 3 and the support plate 2 are adhered to the entire joint surface via an adhesive agent 4. As the adhesive agent 4, for example, an epoxy type adhesive is used, and its thickness is 50 to 1
When the thickness is within the range of 00 μm, the adhesive strength can be increased. At this time, the bonding surface between the plate-like body 3 and the support plate 2 can be a rough surface with a center line average roughness (Ra) of 0.5 μm or more, or by forming fine irregularities, the adhesive strength can be increased. .

All the surfaces of the plate-shaped body 3 other than the bonding surface are smooth surfaces having a center line average roughness (Ra) of 0.5 μm or less, preferably 0.03 μm or less. In this way, single crystal alumina can have an extremely smooth surface, so that the edge 3a is sharpened and
It is possible to prevent adhesion of a coating agent or the like.

Here, the above-mentioned single crystal alumina is a single crystal of alumina (Al ₂ O ₃ ), and as shown in the characteristic values in Table 1, the hardness is extremely higher than that of other ceramics. The edge 3a has excellent wear resistance and can be used satisfactorily for a long period of time. In addition, single-crystal alumina has high bending strength and is therefore less likely to be damaged during use, and since it is a single-crystal body having no grain boundaries, it has high corrosion resistance,
Can be used satisfactorily for a long time even when used in chemicals.

Further, the single crystal alumina has C-axis, A-axis,
There is a crystal axis of R axis, and the plane perpendicular to each axis is the C plane,
They are called the A surface and the R surface. Further, as shown in Table 1, since the hardness differs depending on each surface, it is preferable that the A surface having the highest hardness is the edge 3a. For that purpose, as shown by an arrow in FIG. Should match the C-axis direction. Here, matching the length direction with the C-axis direction means that the angle between them is within 20 °.

Such single-crystal alumina can be produced by inserting a seed crystal into an alumina melt and pulling it up to grow the crystal by the EFG method or the Czochralski method. At this time, it can be manufactured in a plate shape according to the shape of the pulling die, and if the crystal axis of the seed crystal is arranged so that the pulling direction is the C axis, the obtained single crystal alumina is also obtained. The pull-up direction (length direction) can be the C-axis direction.

[0023]

[Table 1]

Next, another embodiment of the present invention will be described.

The doctor blade 10 shown in FIG. 4 is provided with two stages of blades in the traveling direction (arrow direction), and has a first support plate 11 and a second support plate 12,
The single crystal alumina plate-like body 13 is provided on each side surface of the tip,
14 is adhered. The tip of the first support plate 11 is
The second support plate 12 is arranged at a position slightly higher than the tip of the second support plate 12, and the step a and the distance b between the two are set to optimum values according to the usage conditions.

When the doctor blade 10 is moved in the direction of the arrow to apply the coating agent 31 onto the paper 30, first, the first support plate 11 side is left to some extent, and the second support plate 12 side is finished. Therefore, the coating agent 31 can be applied to a more uniform thickness. Moreover, each plate 1
Since the load applied to 3 and 14 is reduced, the life can be extended.

Further, in this example, the plate-like body 13 on the first support plate 11 side is not necessarily made of single crystal alumina,
It may be a ceramic such as alumina or zirconia, or a metal material. Further, the tip shape thereof does not necessarily have to be a sharp edge and may be a curved surface.

On the other hand, the plate-like body 14 on the second support plate 12 side is always made of single crystal alumina, and its tip is provided with a sharp edge, so that uniform coating can be performed for a long period of time.

Further, as shown in the plan views of FIGS. 5A and 5B, the first support plate 11 has a shape such that the central portion thereof protrudes toward the traveling direction side. The resistance at the time of smoothing can be reduced, and the coating work can be performed smoothly. At this time, the protrusion angle θ of the first support plate 11 shown in FIG. 5A is set in the range of 90 to 180 °.
The radius of curvature R of the first support plate 11 shown in (b) is set to T / 2 or more with respect to the width T of the paper 30.

In the above example, an example in which two stages of blades are provided is shown, but it is also possible to provide three or more stages of blades. Also in this case, the tip edge of the last blade should be formed of single crystal alumina.

In the above embodiment, only the step of applying the coating agent 31 such as resin or heat sensitive agent on the paper 30 has been described, but the doctor blade 1 of the present invention can be used for various other purposes. You can For example, a step of coating a resin or the like on the surface of a sheet-shaped body other than paper, a step of scraping off excess ink adhering to the plate surface of a printing plate, a ceramic slurry is applied to the sheet with a constant thickness to produce a green sheet. It can be suitably used for applying other substances to the sheet-like body or scraping it off, such as in the step of forming rubber or food products into a sheet shape.

[0032]

EXAMPLE As an example of the present invention shown in FIG. 1, a 0.5 mm thick and 75 mm wide metal supporting plate 2 is formed on a tip side surface portion of a single crystal alumina having a thickness of 0.5 mm and a width of 12 m.
A doctor blade 1 was manufactured by adhering a plate-shaped body 3 having a m and an edge angle of 90 °. As a comparative example, a support plate 2 only and a plate body 3 formed of zirconia ceramics were prepared, and a test of applying a resin coating agent 31 on the paper 30 was continuously conducted under the same conditions. The time until it became unusable due to wear was compared.

As shown in the results in Table 2, it is understood that the doctor blade 1 of the present invention can have a very long life as compared with the one using zirconia ceramics.

[0034]

[Table 2]

[0035]

As described above, according to the present invention, since at least the leading edge of the doctor blade is made of single crystal alumina, the hardness and corrosion resistance are high, so that the doctor blade can be used satisfactorily for a long time and has a long life. Can be lengthened.

According to the present invention, the doctor blade has a multi-stage structure, and at least the front edge of the rearmost blade is formed of single crystal alumina, so that when the coating agent is applied, for example, the front blade is coated. By smoothing the agent and finishing it with the blade on the rear side, it is possible to apply the agent to a more uniform thickness and to reduce the load applied to each blade, so that the life can be extended.

[Brief description of drawings]

FIG. 1 is a perspective view showing a doctor blade of the present invention.

2 (a) to 2 (d) are views showing various embodiments corresponding to a cross section taken along line XX in FIG.

FIG. 3 is a diagram showing a process of applying a coating agent on paper using the doctor blade of the present invention.

FIG. 4 is a sectional view showing another embodiment of the doctor blade of the present invention.

5 is a view showing various embodiments corresponding to a section taken along line YY in FIG.

FIG. 6 is a cross-sectional view showing a conventional doctor blade.

[Explanation of symbols]

 1, 10: Doctor blade 2, 11, 12: Support plate 3, 13, 14: Plate 3a: Edge 4: Adhesive 30: Paper 31: Coating agent

Claims (2)

[Claims] 1. A doctor blade, wherein at least a tip edge portion is made of single crystal alumina. 2. A doctor blade in which blades are arranged in multiple stages along the traveling direction, and at least the tip edge portion of the rearmost blade is made of single crystal alumina.