JPS61151425A - Manufacture of disc for rotary encoder - Google Patents

Abstract

PURPOSE:To obtain an inexpensive disc for an optical encoder showing almost no warpage, by applying heat treatment to a disc formed by electroplating under pressure in a state grasped by a jig. CONSTITUTION:Resist 8 is formed to a thin metal plate 7 at a part other than a disc pattern. This thin metal plate is used as a cathode and a metal 9 is precipitated by electroplating to form a disc. Subsequently, the removal of the thin metal plate 7 and the release of the resist 8 are performed. By this method, the part, where the resist 8 was present, comes to a slit part 10. The disc obtained by this process generates warpage (b) by internal strain at the time of plating. Hereupon, the metal disc having warpage is grasped by the jig 11 and subjected to heat treatment under pressure to correct warpage. According to this manufacturing process, the highly accurate and highly reliable disc for an optical rotary encoder excellent in flatness and having slits in high density arrangement is obtained by using an inexpensive metal as a base material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a disk for an optical rotary encoder.

[Conventional technology]

Rotary encoders are used in a wide range of fields as sensors that detect rotation angles.

An optical rotary encoder incorporates a rotating disk with many slits on its side. Among these, disks for high-resolution encoders are manufactured by depositing metal on a glass plate and etching the deposited metal to form slits, etc., but the manufacturing process is complicated and the product is expensive. It is. On the other hand, cheaper encoders are manufactured by mechanically punching a metal plate or by forming a resist on the metal plate and etching it, but the resolution of the encoder is inevitably low. It's a situation. For example, when forming slits in a metal plate by etching, so-called side etching becomes a problem, making it difficult to narrow the slit spacing, and the slit width also varies widely, which tends to cause protrusions (burrs) on the slit. , it becomes difficult to arrange the slits with high density. It is also known to obtain metal disks by pattern plating techniques. This method is suitable for increasing the density of the slit arrangement, but it is difficult to keep the internal stress generated during the plating process small, and if internal stress occurs during the plating process, the disk may warp. The result is that When these disks are incorporated into an encoder, as shown in Figure 2 (A), the disks are fixed to the shaft 4 by the hub 3, so although the warpage is reduced, it is not completely corrected and the warpage continues. It remains as a. Since the distance between the slit portion of the disk 1 and the fixed slit plate 21 or the light receiving element 61 changes depending on the rotation angle, the signal strength and contrast become unstable, causing malfunction. The distance between the fixed slit plate and the disk is preferably smaller than the arrangement pitch of the slits on the disk, and the warpage of the disk needs to be smaller than the distance between the light receiving element and the disk. Therefore, in a disk with a high slit density, the warpage needs to be smaller.

[Problem that the invention seeks to solve]

The present invention is made of metal and has slits arranged in a high density arrangement, and there is almost no warping, which was a problem with the conventional method.
The purpose of the present invention is to provide a method for manufacturing a high-performance and inexpensive disk for an optical rotary encoder.

[Means for solving problems]

In this invention, a resist and a turn are formed on the surface of a thin metal plate, a metal disk is formed by electroplating using the thin metal plate as a cathode, and then the thin metal plate is removed and the resist is peeled off. This is a method of manufacturing a disk for an optical rotary encoder, in which the obtained disk is held between jigs and subjected to heating and pressure treatment. The details of the process will be explained below with reference to FIG.

Reference numeral 7 in FIG. 1(A) indicates the side surface of the gold i-thin plate that serves as the cathode. If the thin metal plate is to be removed by etching in the subsequent process (D>), the thin metal plate should preferably have etching characteristics different from those of the metal deposited by electrolytic plating. Electrolytically plated metal is not etched, making it possible to perform high-precision thin metal sheet processing and notching. Suitable thin metal sheet materials for this include aluminum, tin, and zinc.

FIG. 1 CB) shows the resist forming process, and particularly shows a cross-sectional portion of the slit portion 10 of the disk. Reference numeral 8 indicates a resist, and this portion will eventually become the slit portion 10. As a method for forming the resist on the portion other than the pattern portion, screen printing or gravure printing may be used, but it is preferable to use a photoresist that can easily form a fine pattern. As a forming method, it can be obtained through coating, exposure, and development processes. As a photoresist, Eastman Kodak's KPR,
KOR, KPL, KTPR, KMER, TPR of Tokyo Ohkasha.

There are negative types such as 0MR81 and F8H manufactured by Fuji Pharmaceutical Co., Ltd., and positive types such as KADR manufactured by Eastman Kodanok and AZ-1350 manufactured by Shipley. Although dry film resists can also be used, liquid resists are superior in terms of resolution.

FIG. 1(C) shows the electrolytic plating process, and 9 indicates the deposited metal. As for the type of electrolytic plating, any metal that can be plated may be used, but from the viewpoint of hardness, rigidity, corrosion resistance, economical efficiency, and heat treatment characteristics, nickel alloys and nickel alloys are preferable. The plating method allows a high-density slit arrangement and is particularly suitable for manufacturing disks with a slit density of 3, 5, or more.

FIG. 1(D) shows the process of removing the thin metal plate.

The thin metal plate is removed by etching or mechanically peeled off, but in order to avoid damage to the disk and make the process more reliable, etching is preferred and partial etching is performed during etching removal. In some cases, it is also possible to leave a part of the thin plate on the disk side as a reinforcing plate. As mentioned above, when aluminum, tin, or zinc is used as the thin metal plate, the etching solution is an acidic aqueous solution such as dilute hydrochloric acid,
Alternatively, an alkaline aqueous solution such as a sodium hydroxide solution is used. Note that when etching removal is performed, the resist remains on the disk side as shown in FIG. 3D, but when peeling and removal is performed, most of the resist remains on the thin metal plate side.

FIG. 1(E) is a side view showing the resist stripping process, and shows the end face when the slit portion of the disk is cut along the dotted line as shown in FIG. 1(E'). To remove the resist, use a commercially available resist stripping solution, such as Nagase Sangyo Co., Ltd.'s resist strip rJ-100J.
, rN-500J, etc. are used. Even when the thin metal plate is peeled off in step (D), it is preferable to peel off the resist because partial residues of the resist remain on the disk.

Note that the steps (D) and (E) may be performed in reverse order.

The disk obtained through the above steps is warped due to internal stress during plating. The degree of warpage varies depending on the type of plating and operating conditions, but is usually at least 100 μm. Note that the warpage mentioned here is
The warp b of the disc itself shown in Figure 2 (B), that is, the distance between the true planes when the flat part of the disc is sandwiched between two mutually parallel geometric planes and the distance between the two palmar surfaces is the minimum. This refers to the value obtained by subtracting the thickness of the disk from the distance. Hereinafter, unless otherwise specified, warpage refers to b.

Therefore, in the present invention, the obtained metal disk is further sandwiched between jigs and subjected to heat and pressure treatment to correct the warpage. Figure 1 (
F) shows a step in which a warped metal disk is held between the jig 11 and the warp is corrected by heat and pressure treatment.

The heating temperature is 0.3 to 0.9 times, preferably 0.35 to 0.9 times the melting point or eutectic temperature of the metal expressed in absolute temperature.
0.7 times, more preferably 0.37 to 0.6 times. If the heating temperature is lower than the appropriate temperature range, the warpage is often not corrected, and if it is higher, the fine shape of the slit part of the disc is deformed, often leading to disc deterioration. In the case of heating, oxidation of the metal is accelerated unnecessarily. The heating time is preferably 1 minute to 3 hours, particularly 5 minutes to 1 hour from the viewpoint of reliability and workability.

At least one of the surfaces of the jig that holds the disk in contact with the disk must be a rigid body with good flatness, but the other surface may be made of a flexible material such as fluororesin. The above flatness needs to be equal to or higher than the required flatness of the disk, but jigs with flatness that can be used in the present invention, such as those with a warp of about 10 u, are relatively easily available. As for the heating method, a heater may be attached to the main body of the jig for heating, or the disk may be sandwiched between the jig and heated by placing it in an oven, electric furnace, etc. The rigid material of the jig must not melt or soften at the temperature at which it will be used, and in order to prevent the jig from deforming due to heating, it should have a low coefficient of thermal expansion, especially at high temperatures of 500℃ or higher. When used in
'The following are preferred. Examples include ceramics, porcelain, quartz glass, etc. At low temperatures, metals, soda glass, etc. can also be used.

Pressure is applied at the same time as heating. Pressure is 0.5g/-
The pressure may be in the range of ~100 kg/-, but in order to avoid deformation of the slit portion of the disk, the pressure is preferably such that the warpage of the disk is corrected, and a pressure of 1 g/- to 500 g/- is appropriate.

In order to further clarify aspects of the present invention, examples will be given and explained below, but this invention can also be applied to the manufacture of moving slit plates for linear gauges, fixed slit plates for encoders, etc. It is not limited to this, and various modifications are possible.

[Example 1] A negative resist "Microresist-'147" manufactured by Eastman Co., Ltd. was applied on a thin aluminum plate with a thickness of 80 μm.
-110cStJ is applied to a film thickness of 3μ, pre-baked, exposed to a high-pressure mercury lamp through an encoder disk pattern, developed using a special developer and rinse solution, and post-baked to form an aluminum thin plate. A resist was formed on the area other than the disk pattern on one side of the disk.

Then, using a nickel-phosphorus electrolytic plating solution "Ninkelin B" manufactured by Jitsukei Pharmaceutical Industries Co., Ltd., and using the aluminum thin plate as a cathode, a nickel-phosphorus alloy having a thickness of 35 μm was formed on the patterned portion of the surface by electrolytic plating. After removing the thin aluminum plate by etching with 18% by weight hydrochloric acid, the resist was removed using a resist strip rN-500J manufactured by Nagase Sangyo Co., Ltd. The resulting nickel-phosphorus alloy disk 1 has an outer diameter of 24mφ and a thickness of 35I! M, and the number of slits was 400. A total of 100 disks were made in the same manner and the warp b was measured.
All values were in the range of 150 μm to 2 μl.

Next, these disks were tested in order on commercially available temporary glass, a pressure of 38 g weight/crA was applied, and heating was performed at 250° C. for 35 minutes, followed by natural air cooling. the result,
The warpage of each disk was reduced to values ranging from 3 to 20 IIM. As a result, 100 metal disks for optical rotary encoders with excellent flatness were obtained.

[Example 2] After forming a resist pattern on a thin aluminum plate in the same manner as in Example 1, electrolytic plating was performed in a Watt-type nickel bath containing Acuna SXJ manufactured by Jitsukei Pharmaceutical Industries Co., Ltd. The thin aluminum plate was removed by etching with an aqueous solution of sodium hydroxide, and then the resist was removed using a resist strip rN-500J manufactured by Nagase Sangyo Co., Ltd.

The obtained disk had a thickness of 25μ and an outer diameter of 22111φ.
The number of slits was 768. A total of 100 disks of the same size were produced by the same operation and the warpage b was measured, and the warpage values were all in the range of 150 to 500p. Next, these disks were sandwiched between ceramic plates with polished surfaces, and a pressure of 3 g/ant was applied.
Heating was performed at 70° C. for 45 minutes, and then air cooling was performed. As a result, the warpage of each disk was 3 to 20
．． It decreased to a value in the range of u. As a result of the above, 100 metal disks for optical rotary encoders with excellent flatness were obtained.

[Example 3] The electrolytic plating process was carried out in the same manner as in Example 2, and then the resist was removed using "Resist Strip rN-500" manufactured by Nagase Sangyo Co., Ltd. After that, an aluminum thin plate was coated with a 5% by weight sodium hydroxide solution. 100 disks having a thickness of 25 μm, an outer diameter of 22 mm, and 768 slits were obtained through the process of etching and removing the disks. All of these warpage values were in the range of 150 to 500n. Next, when these disks were subjected to the same heat and pressure treatment as in Example 2, the warpage of each disk was reduced to a value in the range of 3 to 20 u. As a result, 100 metal disks for optical rotary encoders with excellent flatness were obtained.

〔Effect of the invention〕

According to the manufacturing method of the present invention, it is possible to obtain a highly accurate and highly reliable optical rotary encoder disk having a high density arrangement of slits with excellent flatness and using an inexpensive metal as a material.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the steps of the method for manufacturing a metal disk of the present invention, FIG. 2 (A) is a side view of the metal disk incorporated in an optical rotary encoder, and FIG.
) is a diagram showing the definition of warpage of a metal disk. i - m - Metal disk 2 - Fixed slit plate 3 - Hub 4 - Rotating shaft 5 - Light emitting element 6 - Light receiving element 7 - Thin metal plate 8 - Resist 9 - Electrodeposited metal 10 - Slit part 11--Jig a ・-Warpage of metal disc when fixed to hub

Claims (1)

[Claims] A resist is formed on a thin metal plate in areas other than the disk pattern, and a disk is formed by electroplating using the thin metal plate as a cathode.Then, the thin metal plate is removed and the resist is peeled off, and the resulting disk is placed in a jig. A method for producing a disc for an optical rotary encoder, which is characterized by sandwiching the disc between the two and subjecting it to heat and pressure treatment.