A Process for Manufacturing a Grain Chill Roller

Europaisches Patentamt 0 360 192 European Patent Office GO Publication number: A1 Office europeen des brevets

EUROPEAN PATENT APPLICATION

© Priority: 23.09.88 US 248469 © Applicant: EASTMAN KODAK COMPANY 343 State Street © Date of publication of application: Rochester New York 14650(US) 28.03.90 Bulletin 90/13 © Inventor: Lioy, Daniel C. c/o EASTMAN © Designated Contracting States: KODAK COMPANY DE FR GB Patent Department 343 State Street Rochester New York 14650(US) Inventor: Haas, Roger S. c/o EASTMAN KODAK COMPANY Patent Department 343 State Street Rochester New York 14650(US) Inventor: McKim, Arlin L. c/o EASTMAN KODAK COMPANY Patent Department 343 State Street Rochester New York 14650(US) Inventor: DeGrave, Gilbert F. c/o EASTMAN KODAK COMPANY Patent Department 343 State Street Rochester New York 14650(US)

© A grain chill roller (10) is manufactured by elec- 18 *Ttroplating a layer of copper onto the surface of the ^roller. The layer of copper is then abrasively blasted C>Jwith glass beads to produce surface features of a C substantially uniform depth, and then the surface is *"" abrasively blasted with small particles of silicon diox- Oide to modify the pattern of features formed by the 22 ^previous blasting operation. The resulting surface is electroplated with a layer of bright nickel to level the Odown pattern of the surface without eliminating the Q^down pattern. The roller is used in the manufacture HI of resin coated photographic paper, for example. 12 FIG. I

Xerox Copy Centre EP0 360 192 A1

A PROCESS FOR MANUFACTURING A GRAIN CHILL ROLLER

The present invention relates to the manufac- over, engraving is an expensive process that con- ture of grain chill rollrs of the kind used for manu- stitutes a significant portion of the total cost of facturing resin coated photographic paper, for ex- manufacture of a grain chill roller. Accordingly, it is ample. desirable to eliminate the engraving step in the It is known to produce photographic paper hav- 5 manufacture of grain chill rollers. ing a resin coated on one surface thereof with the It is an object of the present invention to elimi- resin having a surface texture. This kind of paper is nate the need for the mechanical engraving step in made by a thermoplastic embossing process in the manufacture of grain chill rollers while maintain- which raw (uncoated) paper stock is coated with a ing a surface texture on the roller surface that molten resin, such as polyethylene. The paper with 10 produces the desired texture in resin coated paper the molten resin thereon is brought into contact produced using the roller. This object is accom- with a grain chill roller having a surface pattern. plished by manufacturing the roller with a process Chilled water is pumped through the roller to ex- including the steps of electroplating a layer of tract heat from the resin, causing it to solidify and copper onto the surface of a roller, and then abra- adhere to the paper. During this process the sur- 75 sively blasting the surface of the copper layer with face texture on the chill roller's surface is em- glass beads to create a surface texture with hemi- bossed into the resin coated paper. Thus, the sur- spherical down features having a substantially uni- face pattern on the chill grain roller is critical to the form depth. Then the surface of the copper layer is surface produced in the resin on the coated paper. abrasively blasted with particles of silicon dioxide One known prior process for preparing grain 20 to modify the pattern formed during the step of chill rollers comprises several major steps. These blasting with glass beads. The resulting blasted steps include electroplating copper over a steel surface is bright nickel electroplated to a depth that shell, creating a main surface pattern using a me- results in a leveling of the down pattern of the chanical engraving process and then abrasively surface but without eliminating the down pattern in blasting the engraved surface to disguise tool lines 25 order to provide a high gloss in the surface formed caused by misalignment of the engraving tool. Fi- during the thermoplastic embossing process. nally, the roller is bright nickel electroplated to In the detailed description of the invention pre- produce a durable glossy surface. sented below, reference is made to the accom- During the mechanical engraving step, an en- panying drawings, in which: graving tool, essentially a knurl, is forced against 30 Figure 1 is a diagrammatic view illustrating the roller surface to deform the copper. The pattern the use of a grain chill roller of the invention in a on the engraving tools have been specially de- resin coating process; signed for the manufacture of grain chill rollers. Figure 2 is an enlarged, fragmentary cross The engraving process has many limitations. For section of an electroplated roller after it has been example, any misalignment of the tool will always 35 diamond turned and polished; cause tool lines in the surface. Tool lines produce a Figure 3 is a topograph of the surface of the directional or linear appearance to the surface tex- Figure 2 roller; ture leading to a non-uniform paper product. Also, Figure 4 is a fragmentary cross section of a the engraving process previously used requires roller in which the surface shown in Figure 2 has that the copper layer have a hardness of between 40 been abrasively blasted with glass beads; 45 HRB and 55 HRB. If the copper layer is too Figure 5 is a view similar to Figure 4 show- hard the tool is unable to plastically deform the ing the roller after its surface has been abrasively copper enough to completely emboss the pattern blasted with silicon dioxide particles; and on the chill roller surface. On the other hand, if the Figure 6 is a cross section view of the Figure copper is too soft any slight misalignment of the 45 5 roller after it has been bright nickel electroplated. engraving tool will cause unacceptable tool lines. The present invention relates to the manufac- The prior engraving process requires a layer of ture of a grain chill roller as generally designated copper having a minimum thickness of about 0.014 10 in Figure 1. This Figure illustrates the use of the inches. The engraving process typically needs to roller for applying a coating of resin to a web of be performed by an outside vendor having the so photographic paper. More specifically, a web 12 of necessary engraving equipment to provide the high uncoated paper is fed between the roller 10 and a quality surface required for grain chill rollers. Be- nip roller 14, and travels approximately 180 de- cause such rollers may be three feet or so in grees around the roller 10 to a stripping roller 16. diameter and about eight feet long, the engraving After the paper passes between rollers 10 and 16 it step can take several weeks to complete. More- is pulled away from the chill roller. EP0 360 192 A1

An extruder 18 delivers a curtain of hot, molten After the machining and optional polishing op- resin material 20, such as molten polyethylene, into eration, surface 34 of the copper layer 32 is abra- the nip between rollers 10 and 14 so that the upper sively blasted with glass beads to create a surface surface of the uncoated web 12 receives the mol- texture illustrated in Figure 4. More specifically, the ten resin. Cold water is circulated through the chill 5 surface texture comprises a multiplicity of hemi- roller so that the molten resin is cooled as it travels spherical down features 36 that extend throughout between the nip roller 14 and the stripping roller the length and the circumference of the surface 34 16. When the web 12 is pulled away from the chill of layer 32. roller the coating 22 of resin material is firmly The glass bead blasting operation preferably is adhered to the upper surface of the paper. As the w carried out using an automated direct pressure resin cools, the surface texture on the chill roller's system in which the nozzle feed rate, nozzle dis- surface is embossed into the resin on the paper. tance from the roller surface 34, the roller rotation The resin coating process as generally illustrated in rate during the blasting operation and the velocity Figure 1 and described hereinabove has been used of the glass particles are accurately controlled to for a number of years to coat photographic paper 15 essentially constant values. with resinous material. The hemispherical down features 36 formed The process of the present invention for manu- during the glass bead blasting operation have a facturing a roller 10 can be applied to cylindrical depth that is determined by the momentum of the shells or base rollers of various kinds, for example, glass beads as they strike the copper surface. a steel shell designated 30 in Figure 2. A typical 20 Preferably the size of the glass beads is substan- roller shell used for a chill roll can be approxi- tially uniform so that the mass of each bead is also mately three feet in diameter and eight feet or constant. Thus, the momentum of the glass bead is more in length. However, the process of the inven- dependent only on the velocity of the beads. The tion is applicable to roller shells of substantially any velocity of the beads, in turn, is influenced by the size. 25 nozzle geometry and the blasting pressure utilized. Initially shell 30 is electroplated with a layer of Since the nozzle geometry is constant, the air copper 32 that substantially completely covers the pressure is the only variable that determines the surface of the shell 30. The electroplated copper depth of the down features 36. Air pressure is layer seals any imperfections in the steel shell and controlled to a substantially constant pressure. provides a good bonding layer for the nickel layer 30 Thus, the depth of the down features can be ac- described later. The hardness of the copper layer curately controlled and a substantially uniform can vary over a wide range of values. More specifi- depth is obtained. Air pressures ranging from 3 to cally, a layer hardness of between 45 HRB to 73 7 psig are preferred for the process of the inven- HRB has been found to be satisfactory for the tion. process of this invention. A hardness of from 60-65 35 The number of the down features 36 is deter- HRB is preferred. The copper layer 32 preferably mined by the bead size and the pattern depth. has an average thickness of 0.010 to 0.015 inches, Larger bead diameters and deeper patterns result and can have an average thickness as small as in fewer numbers of features in a given area. 0.008 inches. In the prior manufacturing process Therefore the number of features is inherently de- described earlier in which layer 32 was engraved, a 40 termined by the bead size and the pattern depth. minimum thickness of 0.014 inches of copper was Preferably the glass beads used conform to mili- considered essential. tary size and shape specification MIL-G-9954A No. The copper layer 32 is machined, preferably 4. by using a diamond lathe cutting tool, to establish The pattern depth obtained by bead blasting the cylindrical geometry of the chill roller and to 45 can be varied between about 500 to 700 microin- produce a good surface finish 34. The finish of ches, but preferably is between 550 and 650 surface 34 after diamond turning is approximately microinches. Because of the ductility of copper and 20 to 25 microinches Ra. The term Ra refers to the the mass of the glass beads, extremely low pres- roughness average and is sometimes referred to as sures are required to achieve pattern depth within C.L.A. or AA. The roughness average is the 50 this range. Pattern depth within this range can be arithmetic average of all departures of the rough- obtained with pressures of between 3 and 7 psig ness profile from the mean line. It is measured in using a direct pressure blasting system. microinches. A topograph of the diamond turned The process of the invention utilizing glass surface is illustrated in Figure 3. Drawing Figures 2 bead blasting is relatively insensitive to the hard- and 3 are aligned so that the surface characteris- 55 ness of the copper layer 32 as compared to the tics shown in Figure 2 in section are directly above engraving step used in the prior process described the corresponding portion of the surface shown in at the beginning of this specification. As indicated Figure 3. previously, copper hardness varying from 45 to 73 EP0 360 192 A1

HRB have been used successfully with little effect on historical results and experience. on the blasting pressure required to obtain the Online inspection equipment can be used to desired pattern depth. By comparison, the prior indicate when the desired surface texture of elec- process using an engraving step required a copper troplated nickel layer 40 has been achieved, and hardness of between 45 and 55 HRB. If the copper 5 thus when to stop the plating step. This equipment layer were too hard, the engraving tool was unable may comprise a gloss meter capable of detecting to plastically deform the copper sufficiently to em- small changes in specular reflection of the surface boss the pattern on the roll surface, but if the covered with a thin layer of liquid. The final surface copper was too soft any slight misalignment of the texture achieved can be varied depending upon the engraving tool caused unacceptable tool lines. 10 characteristics that the manufacturer desires to im- Also, the glass bead blasting step enables the part to the resin coating applied to the web 12 by thickness of the copper layer to be as small as the process described hereinbefore with regard to 0.008 inches with no adverse effects whereas the Figure 1. prior engraving step required a minimum thickness Coated paper produced by the process de- of 0.014 inches of copper. 15 scribed relative to Figure 1 using the chill grain The next step in the manufacture of the grain roller 10 of the invention has a surface texture chill roll 10 is a surface texturing step for the characteristic that is similar to prior grain chill roll- copper layer 32. The preferred surface texturing ers manufactured using a mechanical engraving process comprises abrasively blasting the surface step. However, eliminating the engraving step pro- of layer 32 with particles of silicon dioxide to modi- 20 vides a number of desirable advantages. For exam- fy the surface pattern shown in Figure 4 to the ple, any misalignment of the tool used for engrav- pattern shown in Figure 5. As in the glass bead ing produces tool lines in the surface which result blasting operation previously described, the pattern in a directional or linear appearance to the surface depth resulting from the silicon dioxide blasting texture leading to non-uniform paper product. Such step is controlled by the air pressure used since 25 lines are eliminated by the glass bead abrasive other factors such as bead size, mass of particle, blasting step. In addition, the engraving process etc., are constant. The surface texturing step can required a copper hardness within narrow limits, use silicon dioxide particles of between 100 and and a thicker copper layer. More specifically, the 150 U.S. standard mesh size particles. The result- prior process required a hardness of about 45 to 55 ing surface, designated 38 in Figure 6 retains the 30 HRB and a minimum thickness of 0.014 inches for general pattern of down features shown at 36 in the copper layer compared to a hardness of about Figure 4, but introduces an increased number of 45 to 73 HRB and a thickness of 0.008 inches for smaller down patterns within the overall surface the process of the present invention. configuration. Another important advantage resulting from The final step in the process comprises bright 35 elimination of the mechanical engraving step is a nickel electroplating the blasted copper surface 38 significant cost reduction. The cost of the engrav- to provide a surface layer of bright nickel des- ing step is about 10 to 12 times more expensive ignated 40 in Figure 6. Preferably, the thickness of than the bead blasting step that replaces it. In layer 40 is about 350 to 450 microinches. The addition, the engraving step required 8 to 10 times bright nickel deposited during the electroplating 40 as many man hours to complete as does the glass step smoothes out the surface 38 of the copper bead blasting step that replaces it. layer and produces a reflective and durable surface. Because of the release characteristics of the bright nickel surface, the resin 20 will not adhere to Claims the surface of the roller. Preferably the electroplat- 45 ing step is carefully controlled so that the final 1 . A manufacturing process for preparing a depth of the electroplated surface texture is within surface of a roller for use in a thermoplastic em- plus or minus 50 microinches. This will assure bossing process, the manufacturing process being proper gloss and sensitometry of the resin coated characterized by the steps of: paper prepared by the process described in con- 50 electroplating a layer (32) of copper onto the sur- nection with Figure 1. face of a roller (30), The leveling characteristics of the bright nickel abrasively blasting the surface of the copper layer plating process cause the resulting surface texture with glass beads to create a surface texture with to be an inverse function of the plating time. More hemispherical down features (36) having a substan- specifically, the longer plating time produces 55 tially uniform depth, smoother, higher gloss surfaces. Knowing the sur- abrasively blasting the copper surface with par- face texture of surface 38 before the plating pro- ticles of silicon dioxide to modify the pattern cess, the duration of plating is determined based formed during the step of blasting with glass beads EP0 360 192 A1 and create a textured surface (38), and bright nickel electroplating the blasted surface to a depth that results in a leveling of the down pattern of the surface without eliminating the down pattern in order to avoid a high gloss surface in the surface 5 formed during the thermoplastic embossing process. 2. The process as set forth in Claim 1 further comprising machining the copper layer to establish a cylindrical geometry and then polishing the layer 10 to produce a smooth surface (34) prior to glass blasting the layer. 3. The process as set forth in Claim 1 wherein the glass bead blasting step produces hemispherical down features (36) having a depth of between 75 about 500 to 700 microinches, and the silicon dioxide blasting step is carried out with particles of silicon dioxide of between 100 and 150 U.S. standard mesh size. 4. The process as set forth in Claim 1 wherein 20 the step of electroplating a layer (32) of copper onto the roller is controlled to produce a copper layer of about 0.008 inches or greater and a hardness of about 45 to 73 HRB. 5. A manufacturing process for preparing a 25 surface of a roller for use in a thermoplastic embossing process, the manufacturing process being characterized by the steps of: electroplating onto the surface of a roller a layer (32) of copper having a thickness of 0.008 inches 30 or greater and a layer hardness of about 45 to 73 HRB machining the surface of the layer to establish a cylindrical geometry, polishing the machined surface to smooth the sur- 35 face, abrasively blasting the surface of the copper layer with glass beads to create a surface texture with hemispherical down features (36) having a substantially uniform depth of between 550 and 650 40 microinches, abrasively blasting the copper surface with particles of silicon dioxide having a particle size of between 100 and 150 U.S. standard mesh size to modify the pattern formed during the step of blast- 45 ing with glass beads and create a textured surface (38), and bright nickel electroplating the blasted surface to a depth that results in a leveling of the down pattern of the surface without eliminating the down pattern so in order to avoid a high gloss surface in the surface formed during the thermoplastic embossing process.

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FIG. 6 European Patent Application number J» EUROPEAN SEARCH REPORT Office

EP 89117221.5 DOCUMENTS CONSIDERED TO BE RELEVANT Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE Category of relevant passages to claim APPLICATION (Int Cl ■* ) X PATENT ABSTRACTS OF JAPAN, 1,5 C 25 D 5/12 unexamined applications, C 25 D 1/10 section P, vol. 6, no. 171, September 4, 1982 THE PATENT OFFICE JAPANESE GOVERNMENT page 62 P 140 * Kokai-no. 57-88 449 (MITSUBISHI) *

TECHNICAL FIELDS SEARCHED (Int. CM)

C 25 D

The present search report has been drawn up tor all claims Place of search Date of completion of the search Examiner VIENNA 18-12-1989 LUX

CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on. or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A' : technological background O : non-written disclosure & : member of the same patent family, corresponding a.o P : intermediate document document