JP5551008B2 - Forming roll and manufacturing method thereof - Google Patents

Description

  The present invention relates to a forming roll. More specifically, the present invention has an amorphous nickel alloy layer on the surface of a roll body made of carbon steel, alloy steel, stainless steel, and the like, and further has a hard chromium layer on the amorphous nickel alloy layer. The present invention relates to a roll suitable for molding a plastic sheet or a plastic film, particularly an optical sheet or an optical film.

  A roll in which a hard chrome plating layer is deposited on a metal surface, and the hard chrome plating is smoothly finished to a mirror surface by a physical polishing method such as grinder polishing, buff polishing, or grindstone polishing is well known. It is also well known that hard chromium plating films contain microcracks due to their high electrodeposition stress. Hard chrome plating has excellent properties such as high hardness, wear resistance, mold releasability, excellent light reflectivity, corrosion resistance and other metal coatings. It is covered with a piston rod and is often used as a functional coating. Also for decorative applications, it has been used in decorative fields for a long time as a decorative chrome because of its high hardness, unique metallic luster, and long lasting luster without changing its appearance. .

  However, the presence of microcracks in the metal film is sometimes a fatal defect even if the corrosion resistance of the chromium plating itself is excellent. Although corrosion-inducing components such as moisture, sulfur dioxide, and chloride ions permeate through the crack, and the chrome plating itself does not corrode, the underlying metal is corroded by the local battery action, so the product life is shortened. Shorter.

  For example, as a document disclosing the prior art of this type, Patent Document 1 discloses that between the base metal and the hard chromium plating layer for the purpose of preventing the expansion of cracks originally present in the chromium plating and the anti-corrosion measures for the roll components. A cast drum using electro-nickel plating that is free from cracks, has flexibility, and can completely protect the base metal is disclosed. However, even if there is an intermediate layer of nickel plating, the microcracks present in the chromium plating are not eliminated, and they cannot be observed visually. In this way, since the nickel plating intermediate layer is flexible, the one coated with hard chrome plating is caused by buried abrasive grains or dropped abrasive grains through various grinding and polishing processes. As a result, defects such as pits, pinholes, and scratches may be formed on the hard chrome plating surface coated on the intermediate layer. In that case, a so-called two-layer chromium plating film forming step of repairing a defect generated on the hard chromium plating surface and performing chromium plating again is necessary. As a result, in order to obtain a hard chromium plating layer having a mirror surface, a lot of processing time and labor are required.

  In Patent Document 2, an electroless plating-accepting resin thin film, an electroless plating layer, an intermediate layer of copper or nickel by electroplating, and an outermost layer made of hard chromium plating are provided on the surface of a roll made of carbon fiber reinforced resin. And a resin roller having a smooth surface finished by buffing. However, it does not actively prevent cracks in hard chrome plating, and it is not disclosed that the surface roughness is 0.1 μm Ry or less.

  Patent Documents 3, 4 and 5 disclose a method of obtaining chromium plating without cracks by controlling the tensile residual stress of chromium plating by a pulse electrolysis method to obtain residual stress on the compression side. All of the methods disclosed in these documents require special and expensive power supply equipment that can output a pulse wave as a power supply for plating, and there are restrictions on the applicable condition range. Further, as a fatal problem of the power supply equipment for pulse wave output, there is a problem of residual current that occurs when direct current is turned off when producing a large capacity power supply equipment. Larger capacity rectifiers are affected by this effect, so it is theoretically difficult to obtain an ideally shaped pulse pattern. Moreover, it is practically very difficult to make the chrome plating surface coated on the surface of the steel material with many inclusions defect-free even by using the pulse power source.

  In recent years, the production of plastic films and sheets used for optical applications has increased, and the required surface properties for hard chromium plating coated on the forming rolls used in these applications are as follows. A mirror surface of 1 μm Ry or less is required. This surface roughness can be almost achieved by conventional lapping and polishing methods. In addition, the originally existing crack itself is closed. However, in the case of a molding roll that repeatedly receives thermal cycles from the molten plastic that is the molding target, the cracks inherent in the hard chrome plating are exposed early due to the thermal cycles received during molding, and the surface of the film or sheet to be molded However, there is a problem that the crack pattern is transferred. Another problem is that a crack inherent in chrome plating develops during use, and foreign matter (oligomer) adheres to and accumulates on the crack, making it difficult for the molded plastic film or sheet to peel off from the molding roll. In addition, there is a basic problem that the foreign matter adheres to the molded product.

JP-A 61-195994 JP 2001-226794 A JP 2003-147777 A JP 2004-3000522 A JP 2006-188767 A

  As described above, the conventional hard chrome plating is finished with micro cracks inherent, and the cracks are not lost. In addition, the method of obtaining chromium plating without cracks using a special pulse power supply is not applicable to any roll due to the problem of applicable current value, and to control the tensile residual stress value of chromium plating to the compression side. There are conditional constraints. Further, it does not fundamentally eliminate defects such as pits, pinholes, and scratches generated on the hard chrome plating surface due to the base metal.

  The present invention has been made in view of such problems of the prior art, and the object thereof is hard chromium plating without cracks while maintaining the high hardness and releasability inherent in hard chromium plating. It is providing the forming roll which has a layer, and its manufacturing method. Another object of the present invention is to provide a forming roll that is not easily damaged and a method for producing the same.

In order to achieve the above object, the forming roll of the present invention has an amorphous nickel alloy layer coated on the surface of a roll body made of steel, and has a surface roughness of 0.1 μm Ry or less on the amorphous nickel alloy layer. The hard chrome plating layer is covered. ΜmRy, which is a notation of surface roughness in the present invention, is based on the JIS standard established in 1994.
A hard chromium plating layer having a surface roughness of 0.1 μm Ry or less is obtained by polishing the amorphous nickel alloy layer coated on the surface of the roll body with a chromium plating layer and polishing the chromium plating layer. Is preferred.

  The amorphous nickel alloy can be selected from any of a nickel-phosphorus alloy, a nickel-tungsten alloy, and a nickel-tungsten-phosphorus alloy.

  The amorphous nickel alloy layer is coated by a plating method and is preferably polished to a surface roughness of 0.1 μmRy or less, more preferably polished to a surface roughness of 0.05 μmRy or less.

  The thickness of the hard chromium plating layer is preferably 0.1 to 1.0 μm, and more preferably 0.05 to 0.5 μm.

  The chromium plating layer is preferably polished with a polishing pad made of felt or suede cloth and free abrasive grains containing an oxide having an average particle diameter of 10 μm or less, and the surface roughness is preferably 0.05 μm Ry or less. The average particle size in the present invention refers to an arithmetic average value of the minimum particle size and the maximum particle size in the particle size distribution of the substance.

  In the method for producing a forming roll of the present invention, the surface of a roll body made of steel is coated with an amorphous nickel alloy layer, then the amorphous nickel alloy layer is polished, and the polished amorphous nickel alloy layer is formed on the surface. It is characterized by producing a forming roll in which a hard chromium plating layer having a surface roughness of 0.1 μm Ry or less is coated on the outermost surface by coating the chromium plating layer and polishing the chromium plating layer. Yes.

  The forming roll of the present invention does not contain microcracks inside the outermost chromium plating layer, so there is no transfer of cracks or adhesion of foreign substances such as oligomers to the roll surface, and it is produced to clean the roll surface. When applied to the molding of plastic films and plastic sheets for optical applications, it can greatly contribute to the stable production of films and sheets, and can greatly contribute to the development of such industries.

  In addition, the intermediate layer is made of an amorphous nickel alloy layer, has a hardness of HV500-600, is as hard as hardened steel, and can withstand loads from the outside, so the outermost chromium plating layer is reinforced. This makes it easier to prevent deformation due to external stress. Furthermore, since the intermediate layer is made of an amorphous nickel alloy layer, there are almost no film defects, and defects such as pits, pinholes, and scratches are unlikely to occur on the surface of the hard chromium plating layer coated on the intermediate layer. If the outermost thin chrome plating layer is damaged, the damaged outermost thin chrome plating layer can be easily removed by chemical methods (eg, dissolution), and new chrome is applied to the intact intermediate layer. By covering the plating layer, it can be economically regenerated.

FIG. 1 is a photograph (photo magnification is 100 times) showing a plated surface where cracks occur when the chromium plating film thickness is 2.0 μm. FIG. 2 is a photograph (photo magnification is 100 times) showing a plated surface where cracks are not generated when the chromium plating film thickness is 1.0 μm. FIG. 3 is a plan view showing an example of the forming roll of the present invention. FIG. 4 is a diagram showing the measurement depth from the chromium plating surface in Table 3 on the horizontal axis and the hardness measurement value (GPa) in Table 3 on the vertical axis.

(1) Prior examination In order to obtain a mirror roll having a surface roughness of 0.1 μmRy or less, the present inventors selected a method that does not depend on the pulse electrolysis method. As a chromium plating bath, an experiment was performed by changing the numerical values of parameters such as bath temperature and current density, using the most utilized surge bath. As a result, when chromium plating was performed at a high temperature of 70 ° C. or higher, a crack-free chromium plating film was obtained, but it had a hardness of HV500 or less and could not be said to be hard chromium. Thus, from the viewpoint of scratch resistance, it cannot be applied to the molding of plastic films and plastic sheets that are the subject of the present invention.

  On the other hand, the deposition mechanism of chromium plating has been studied for a long time, and the mechanism of crack generation has also been clarified, and the large residual tensile stress of chromium plating is the cause of cracks. For example, according to a well-known document called chrome plating (published June 20, 1964 by Nikkan Kogyo Shimbun, author Matsudaira Kishi), cracks in chrome plating are caused by the internal stress of the plating layer attracting each other's chrome atoms. It is said that if it exceeds, the plating is continued as it is, and if the internal stress of the plating layer exceeds the mutual attractive force of chromium atoms, cracks are supposed to occur. Therefore, when the chromium plating film is thin, cracks should not occur. However, in this case, although the upper limit value of the plating layer thickness that can obtain chromium plating without cracks is not clarified, at least up to 0.25 μm thickness standardized by JIS for decorative chromium plating, It is a common recognition to those skilled in the art that no exists.

(2) Film thickness of plating layer and generation of cracks Therefore, in order to find out hard chrome plating conditions in which no cracks were generated, the following experiment was performed. As a test piece, a S50C carbon steel having a length of 50 mm and a width of 50 mm and a thickness of 10 mm was used, and the surface of the test piece was polished to a roughness of 0.1 μm Ry. Then, the S50C test piece was immersed in a chromium plating bath having a composition of chromic anhydride of 250 g / liter and sulfuric acid of 2.5 g / liter, and the bath temperature was 50 ° C. and the current density was 25 A / dm ^2. The thickness of the chrome plating was changed by changing the electrolysis time. And the presence or absence of a crack was investigated and the surface roughness was measured by magnifying and observing the surface of the test piece of S50C after chromium plating with a microscope (100 times). Then, after holding the chrome-plated S50C test piece at 100 ° C., 200 ° C., 300 ° C., and 350 ° C. for 1 hour and then putting it into cold water at 20 ° C., after the thermal shock test The presence or absence of cracks was investigated by magnifying and observing the surface of the S50C test piece with a microscope (100 times). The presence or absence of the above cracks and the measurement results of the surface roughness are shown in Table 1 below. In Table 1, the symbol “◯” indicates that no crack was generated in the test piece, “Δ” indicates that a crack was generated in a part of the test piece, and “×” indicates that the test piece was clearly cracked. Indicates that this occurred. The surface roughness was measured with Surfcom 480A manufactured by Tokyo Seimitsu Co., Ltd.

  According to Table 1, there is a correlation between the film thickness of the chrome plating layer and the thermal shock test temperature, and if it is a film thickness (0.2 to 1.0 μm) that does not cause cracks as it is plated, the plastic film In the thermal shock test in the temperature range up to 300 ° C., which is generally performed in the manufacturing process of plastic sheets, it was found that no cracks occur. FIG. 1 is an enlarged photograph of a surface having a chromium plating film thickness of 2.0 μm, and FIG. 2 is an enlarged photograph of a surface having a chromium plating film thickness of 1.0 μm. FIG. 1 clearly shows the occurrence of cracks (several lines from the upper left to the lower right), but FIG. 2 does not show such cracks.

From Table 1, the relationship between the chrome plating thickness and the surface roughness after chrome plating coating tends to increase as the chrome plating thickness increases. (0.1 μm Ry) was not achieved.
Therefore, the experiment was repeated with respect to the relationship between the plating film thickness and crack generation, the plating film thickness and crack generation after the thermal shock test, and the relationship between the plating film thickness and the surface roughness by changing the chromium plating conditions. As a result, regarding the relationship between the plating film thickness and the occurrence of cracks, the chromic anhydride is 200 to 300 g / liter, the sulfuric acid is 2 to 3 g / liter, the bath temperature is 45 to 55 ° C., and the current density is 10 to 35 A. In the range of / dm ² , it was found that the results of the thermal shock test shown in Table 1 can be almost reproduced. Moreover, it turned out that 0.2-1.0 micrometer is preferable as a range of chromium plating thickness.

(3) Means for achieving a surface roughness of 0.1 μm Ry or less In order to solve the problem of providing a forming roll coated with a hard chromium plating layer having a surface roughness of 0.1 μm Ry or less, Choose between increasing the smoothness of the metal base of the chrome plating layer, providing an intermediate layer that is easy to smooth as a lower layer of the chrome plating layer and is free of cracks, or polishing the thin chrome plating layer be able to. Among them, the method of increasing the smoothness of the metal base of the chrome plating layer is because the steel material is originally non-uniform in composition and contains non-metallic inclusions. There is a drawback that it is easy to cause defects. Further, in order to polish and smooth the chrome plating layer, the film thickness is too thin to use a normal polishing method.
Therefore, the present inventors examined the intermediate layer on which a hard chromium plating layer having a surface roughness of 0.1 μm Ry or less can be formed on the upper portion thereof as follows.

(4) Examination of intermediate layer Same as above, S50C test piece was subjected to copper plating or nickel-phosphorus alloy plating with phosphorus content of 8 wt% or more, and cut to a mirror surface with a surface roughness of 0.06 μm Ry or less by diamond cutting processed. The film thicknesses of the copper plating and nickel-phosphorus alloy plating are both 100 μm. Then, the S50C test piece is immersed in a chromium plating bath having the bath composition of (2) above, and the electrolysis time is changed at the same bath temperature (25 ° C.) and the same current density (25 A / dm ² ). The chromium plating thickness coated on the intermediate layer of copper plating or nickel-phosphorus alloy plating was changed. And the presence or absence of a crack was investigated and the surface roughness was measured by magnifying and observing the surface of the test piece of S50C after chromium plating with a microscope (100 times). Then, after holding the chrome-plated S50C test piece at 100 ° C., 200 ° C., 300 ° C., and 350 ° C. for 1 hour and then putting it into cold water at 20 ° C., after the thermal shock test The presence or absence of cracks was examined by magnifying the surface of the S50C test piece with a microscope (100 times). The measurement results of the surface roughness and the presence or absence of cracks are shown in Table 2 below. The meanings of symbols “◯”, “Δ”, and “x” in Table 2 are the same as those in Table 1. The surface roughness was measured with Surfcom 480A manufactured by Tokyo Seimitsu Co., Ltd.

  From Table 2, the thickness of the chromium plating film on the surface layer is determined by setting the surface roughness after cutting to about 0.03 to 0.06 μm in both the copper plating and the nickel-8 wt% phosphorus alloy plating. When the thickness is up to 1.0 μm, it has been found that there is no crack and a chromium plating layer having a target surface roughness can be obtained.

On the other hand, the thermal shock test results vary depending on the plating type of the intermediate layer. The difference in thermal shock test between copper plating and nickel-8 wt% phosphorus alloy plating is because the respective thermal expansion coefficients are different. If copper having a large coefficient of thermal expansion is used as the intermediate layer, it becomes difficult to withstand thermal expansion during heating in the thermal shock test, and cracks are likely to occur. The thermal expansion coefficient in the vicinity of room temperature and the thermal expansion coefficient at 230 ° C. are “4.9 × 10 ⁻⁶ , 8.8 × 10 ⁻⁶ ” for chromium, copper, and nickel-8 wt% phosphorus alloy, They are “16.5 × 10 ⁻⁶ , 18.3 × 10 ⁻⁶ ” and “12.9 × 10 ⁻⁶ , 11.5 × 10 ⁻⁶ ”.

  Since it was found that the thermal expansion coefficient of the intermediate layer tends to influence the presence or absence of cracks in the surface chromium plating layer, while considering the thermal expansion coefficient as a requirement for selecting a preferred film type as the intermediate layer, A film type that can make the surface roughness after polishing or cutting approximately 0.05 μm Ry was selected.

Specifically, various plating films such as nickel plating, bright nickel, nickel-cobalt alloy plating, nickel-tungsten alloy plating, nickel-tungsten-phosphorus alloy plating, nickel-iron alloy plating, nickel-phosphorus alloy were examined. It was.
As a result, as the film type of the intermediate layer that easily satisfies the surface roughness after polishing or cutting of 0.1 μmRy or less and hardly causes cracks in the surface chromium plating layer, nickel-phosphorus alloy, nickel-tungsten It has been found that alloy plating types such as alloys and nickel-tungsten-phosphorus alloys that tend to be amorphous or quasi-amorphous are most suitable. The reason is that since it is amorphous, it does not take a crystal form, and the surface can be smoothed by polishing or cutting. Even if the surface of these amorphous alloys is coated with 1.0 μm of chromium plating without cracks and subjected to a thermal shock test at 300 ° C. (held at 300 ° C. for 1 hour and then put into 20 ° C. cold water), copper remains in the middle. It was confirmed that no cracks were generated as in the case of the layer.

  The film thickness suitable for the intermediate layer is such that the metal base is not exposed even if the intermediate layer is removed by post-processing such as polishing, grinding, cutting, and lapping to improve the shape accuracy and surface roughness of the roll. If it is more than thickness, there will be no restriction | limiting in particular in thickness. However, in order for the intermediate layer to serve this function as a quenching substitute layer to prevent plastic deformation of the roll material, the intermediate layer has a hardness of HV500 or more, and the intermediate layer has a thickness of at least 50 μm, preferably The thickness of the intermediate layer is more preferably 100 μm or more.

  Examples of the composition of the plating solution suitable for obtaining the nickel-phosphorus alloy, nickel-tungsten alloy, nickel-tungsten-phosphorus alloy as the intermediate layer and the application conditions thereof are as follows, but are not limited thereto. Is not to be done.

(5) Preferred composition of plating solution and application conditions for obtaining the intermediate layer of the present invention
a. Nickel-phosphorus alloy plating (P content is 8wt% or more)
pH 1-4
Nickel sulfate 100-200g / liter
Sodium citrate 80-120g / liter
Phosphorous acid 30-80g / liter
Boric acid 20-40g / liter
Bath temperature 40-60 ° C
Current density 1-5A / dm ²

b. Nickel-tungsten alloy plating (W content 35wt% or more)
pH 5-8
Nickel sulfate 40-65g / liter
Sodium tungstate 50-80g / liter
Diammonium citrate 35-55 g / liter
Sodium formate 5-20g / liter
Bath temperature 55-65 ° C
Current density 5-20A / dm ²

c. Nickel-tungsten-phosphorus alloy plating pH 4-5
Nickel sulfate 25-75g / liter
Sodium tungstate 30-90g / liter
Diammonium citrate 80-100g / liter
Phosphorous acid 2-4g / liter
Bath temperature 40-70 ° C
Current density 5-20A / dm ²

  As a result of the above basic experiments, the intermediate layer plating type that does not crack in the chromium plating layer even when subjected to thermal shock is amorphous such as nickel-phosphorus alloy plating, nickel-tungsten alloy plating, nickel-tungsten-phosphorus alloy plating, etc. It was found that a nickel-like alloy was preferable, and the plating thickness of the intermediate layer was preferably 100 μm or more. At the same time, it was found that the surface roughness of the intermediate layer requires a smooth specularity of 0.06 μm Ry or less.

(6) Trial manufacture of mirror-finished chrome plating roll Therefore, as shown in FIG. 3, STKM13A is used as the roll body 1, S45C is used as the roll shaft 2, and the diameter of the roll body 1 is 450 mm. An example of a forming roll of the present invention (hereinafter referred to as a test roll) having a diameter of 1800 mm was actually produced. The body 1 of the test roll is precisely processed to finish the surface roughness to 1.0 μm Ry, and the surface of the body 1 of the test roll is degreased and activated, followed by 200 μm-thick nickel—10 wt. % Phosphorus alloy plating was coated. And the body part 1 of the test roll which coat | covered the nickel- phosphorus alloy plating is cut with a single crystal diamond bite, and after finishing to the surface roughness of 0.03-0.05 micrometer Ry, electrolytic degreasing and activation process Then, using a standard sergeant bath with chromic anhydride of 250 g / liter and sulfuric acid of 2.5 g / liter, electroplating was performed at a bath temperature of 48 ° C. and a current density of 25 A / dm ^2. A mirror roll coated with 0.8 μm thick chromium plating was manufactured. The surface roughness of the body part 1 of the test roll coated with this chromium plating was 0.07 to 0.09 μm Ry, and no cracks were observed even when the surface was magnified. In this way, the object of providing a forming roll having a chromium plating layer having a surface roughness of 0.10 μm Ry or less and having no cracks could be achieved.

  However, if the surface is rubbed with a gauze or clean room wiper (cupra long-fiber nonwoven fabric, for example, Bencott manufactured by Asahi Kasei Co., Ltd.) to wipe off dust on the roll surface, normal chrome plating is polished into a mirror surface roll. It was found that it is easily damaged. The scratches referred to here are small scratches having a size of less than about 30 μm that can be discriminated with the naked eye, and scratches exceeding about 0.2 to 0.3 μm that do not affect optical applications. pointing.

(7) Increasing the hardness of the chrome plating layer The surface roughness is 0.10 μm Ry in the state of chrome plating by carrying out super smoothing of the intermediate layer surface and controlling the chrome plating film thickness on the intermediate layer. Although it was found that the following mirror surface was obtained, it was found that the scratch resistance was slightly inferior. Therefore, in order to improve the scratch resistance, the inventor of the present invention has an amorphous nickel-phosphorus having a thickness of 100 μm on one side of a square S50C test piece having a vertical and horizontal size of 50 mm and a thickness of 10 mm. An alloy is coated to form an intermediate layer, and the surface of the intermediate layer is cut with a diamond cutting tool to have a surface roughness of 0.05 μm Ry. As plating conditions, the bath temperature is 50 ° C. and the current density is 25 A / dm ^2. Two types of chromium plating with a film thickness of 2 μm and 20 μm were applied.

  After that, the test piece with a plating thickness of 2 μm is left as chrome plating, and the test piece with a plating thickness of 20 μm is polished by changing the count with a polishing machine dedicated to a flat plate and finished to a surface roughness of 0.1 μm Ry. It was. In addition, the surface roughness of the test piece with a film thickness of 2 μm and the test piece with a film thickness of 20 μm as-plated was 0.09 μm Ry and 0.4 μm Ry, respectively. Subsequently, in order to measure the hardness from the surface of the test piece in a stepwise manner, an ultra micro hardness was measured using a nanoindenter. Then, although it differs from the display by a normal Vickers hardness meter, it discovered that the chromium plating surface after grinding | polishing becomes remarkably higher hardness than the surface as it is, as shown in Table 3 below. A value obtained by multiplying GPa by 100 is substantially equal to Vickers hardness (HV).

  FIG. 4 illustrates the numerical values in Table 3 with the measurement depth (μm) from the chromium plating surface in Table 3 as the horizontal axis and the hardness measurement value (GPa) in Table 3 as the vertical axis. In FIG. 4, the symbol “●” indicates the chrome plating surface as plated, and the symbol “◯” indicates the chrome plating surface after polishing. From Table 3 and FIG. 4, it can be seen that the hardness is increased by polishing the chromium plating surface, and in particular, the increase in the hardness of the extreme surface layer is significant. In this way, it can be seen that polishing the chromium plating layer significantly increases the hardness and can improve the scratch resistance.

(8) Achievement of smoothing and high hardness of thin chrome plating layer As described above, it was found that when the chrome plating layer was physically polished, the extreme surface layer was extremely hardened. Various methods were studied for the purpose of achieving a further smoothing and higher hardness by physically polishing a thin film having a thickness of about 1.0 μm without exposure and without cracks. As a result, the intermediate layer of the amorphous nickel alloy is cut or polished to a surface roughness of 0.1 μm Ry, preferably 0.05 μm Ry or less, and after the surface is degreased and activated, 1.0 μm or less Then, the chrome-plated surface is polished with a polishing pad such as felt or suede chrome, and free abrasive grains having an average particle diameter of 20 μm or less, preferably 10 μm to 0.1 μm. As a result, it is possible to obtain a mirror-finished chrome-plated surface having a surface roughness of 0.1 μm Ry or less and without the occurrence of scratches associated with polishing, with almost no decrease in the chrome-plated film thickness. It came to do.
The free abrasive is a suspension of at least one of chromium oxide, alumina, and silicon carbide, or a mixture of two or more selected from these, water, and a suitable amount of a dispersion aid. A polishing method is preferred. When the surface hardness of the chromium plating layer polished with the polishing pad and the loose abrasive grains is measured by the nanoindentation method, the range where the depth from the surface is 0.1 μm or less is always high hardness of 20 GPa or more. I was able to confirm that. The hardness by the nanoindentation method and the micro Vickers hardness were almost approximate.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples, and changes and modifications can be made as appropriate without departing from the technical scope of the present invention.

  The surface of the test roll having the diameter of 450 mm and the cylinder length of 1800 mm is grinder-polished and then the surface roughness is about 1 μm Ry by buffing. In use, a 150 μm nickel-phosphorus alloy interlayer was coated. Then, using a # 1000WA resin bond grindstone with a cylindrical precision mirror finisher, the grindstone head rotation speed is 200 rpm, the test roll rotation speed is 100 rpm, the grindstone head feed speed is 300 mm / min, and the water supply amount is 2 liter / min. The surface of the nickel-phosphorous alloy coated on the body of the test roll was polished to a surface roughness of 0.4 μm Ry.

Subsequently, the surface of the nickel-phosphorous alloy coated on the body of the test roll was further polished using felt and loose abrasive grains. That is, as free abrasive grains, 10 wt% of alumina having an average particle diameter of 10 μm, and a polishing liquid composed of 10% aluminum nitrate and a small amount of dispersion aid are continuously dropped at a rate of 5 ml / sec. On the other hand, the surface of the nickel-phosphorus alloy was polished under the conditions that the rotational speed of the felt mounting head was 150 rpm, the rotational speed of the test roll was 100 rpm, the feed speed of the felt mounting head was 300 mm / min, and the processing surface pressure was 100 g / cm ^2. A surface having a surface roughness of 0.06 μm Ry was obtained. After immersing the test roll in a 20% sulfuric acid solution for 5 minutes, using a chromium plating bath having a composition of 250 g / liter of chromic anhydride and 2.3 g / liter of sulfuric acid, the bath temperature is 50 ° C., and the current density is 50 ° C. Was 30 A / dm ² , and a chromium plating with a thickness of 0.5 μm was coated on the nickel-phosphorus alloy layer. The surface roughness after chromium plating was 0.08 μm Ry.

  Again, the test roll was mounted on the same cylindrical precision mirror finisher, and the polishing head rotation was 150 rpm, the test roll rotation speed was 80 rpm, and the polishing head feed speed was 300 mm / min. As a free abrasive, 10 wt% of alumina having an average particle diameter of 10 μm is contained, and a test solution containing 10% aluminum nitrate and a small amount of a dispersion aid is continuously dropped at an appropriate speed of 3 ml / sec. The roll chrome-plated surface was polished.

  About the roughness of the test roll surface after grinding | polishing, when the surface roughness of a roll trunk | drum part both ends and center part was measured with the stylus-type roughness meter, it was contained in the range of 0.03-0.04 micrometer Ry. Further, when the plating film thickness in the vicinity of the roll end is measured with an electrolytic film thickness meter, the average of the measured values for each of the three times at both ends of the body portion is 0.42 μm, which is compared with the initial plating thickness of 0.5 μm The thickness could be reduced to less than 0.1 μm. In order to check the scratch resistance, after scrubbing with gauze and rubbing the surface of the body of the test roll, scratches were confirmed with an optical fiber light guide, but no particular scratch was observed. No cracks inherent to chrome plating were observed even with double magnification observation.

  Especially this invention can be utilized as a shaping | molding roll of an optical sheet or an optical film.

1 Roll body 2 Roll shaft

Claims (6)

A roll body surface made of steel is coated with an amorphous nickel alloy layer, and a hard chromium plating layer having a surface roughness of 0.1 μmRy or less is coated on the amorphous nickel alloy layer .
Amorphous nickel alloy layer, forming rolls, characterized in Rukoto to have a surface roughness of less than 0.1MyumRy. Amorphous nickel alloy, a nickel - phosphorus alloy, a nickel - tungsten alloy and nickel - tungsten - claim 1 Symbol mounting molding rolls, characterized in that from any of a phosphorus alloy is obtained by selecting. The forming roll according to claim 1 or 2 , wherein the thickness of the hard chromium plating layer is 0.1 to 1.0 µm. Hard chromium plating layer forming roll of any one of claims 1 to 3, wherein the front surface roughness is less than 0.05MyumRy. The surface of the roll body made of steel is coated with an amorphous nickel alloy layer, then the amorphous nickel alloy layer is polished or cut , and the chromium plating layer is coated on the polished or cut amorphous nickel alloy layer and further characterized that you coating outermost hard chrome plating layer having a surface roughness of less than 0.1μmRy by polishing the chrome plating layer, any one of claims 1 4 The manufacturing method of the forming roll of description . Chromium plating layer and a polishing pad made of felt or suede cloth, The method according to claim 5 Symbol mounting characterized by being polished average particle size by free abrasive grains comprise the following oxide 10 [mu] m.