Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD OF THE INVENTION
This invention relates generally to the formation of
designs on work surfaces and more particularly concerns a novel
simplified process for forming the desired designs on surfaces
of molds, rolls and dies used in the formation of articles
generally made of de~ormable materials.
DISCUSSION OF THE PRIOR ART
The prior art is well represented by United States
patent 3,052,581. The normal practice is to reproduce the
desired design on a flat metal plate, usually made of zinc, by
photo engraving. An adherent waxy bituminous acid resistant
substance is then spread over th~ surface of the plate to fill
the design areas which have been etched out of the surface.
The design is removed frQm that surface by means of tissue
paper which has been brought in firm surface contact with the
adherent waxy material. This tissue paper is then used as a
means of transferring the design from the flat plate to the
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l ~I mold surfaces. The tissue paper is moistened with a solution
2 ¦l of alcohol and water acting as a release agent t:o facilitate its
3 II,removal leaving the waxy material in place in the mold. ~fter
4 Ithe mold is etched, the waxy material is removed by means o~ a
¦solvent and the mold is then available to be employed for ma~ing
6 ¦I plastic articles. -
I A particular disadvantage of this process is that the8 waxy acid resistant substance tends to be ~lowable i.f the pressure
9 of application to the mold surface appreciably exceeds the neces-
sary pressure. This presents a real limltation on the fineness
11 I;of pattern elements which can be transferred accurately.
12 ~¦ Processes for etching gravure printing cylinders and
13 li plates involve etching designs in metal surfaces. Ho~ever, the
14 jiconsiderations for such etching are substantially dif-Eerent from
!¦mold engraving. The former relates to what may be termed two-
16 l~dimensional uses, depth of etch being necessary only to the
17 j'extent of design delineation for printing purposes. Mold -~ j
18 ¦,engraving, on the other hand, the subject of the present inve~Icn,
19 ¦Irelates to three-dimensional uses, that is, an actual surface
Itexture in an article made with the engraved mold~ Steps to
21 ¦provide a surface etch are in many instances unsatisfactory for
22 Imaking a deeper etch for surface texturing. ~ ~
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1 _UMM~RY OF THE I-~V~ITION
It is an object of this invention to provide a
simpliEied method for producing embossed designs on work surfaces
such as on molds, rolls and dies. For purposes o~ simplification
the term "mold" will generally be used herein. This novel process
requires fewer steps and fewer materials than the prior art
method and thereby reduces both the time and cost necessary to
emboss the sur~aces of mold cavities. Not only is the present
process simpler and quicker, it allows finer designs to be
produced in a more positive manner than the prior art processes.
A master negative of the pattern to be reproduced is
prepared and this pattern is exposed to a photomechanically
imageable transfer material. Upon development, the hardened
image areas are acid resistant and are then transferred by means
of the backing sheet on which the image is formed, to the mold
surfaces. This backing sheet is rubbed or burnished with a
blunt stylus to transfer the image areas to the mold surface
which has normally been appropriately prepared prior to appli-
cation of the elements of the acid resistant image. The mold
2Q surface is then etched, the image elements removed and the mold
is then ready to be employed for makin~ plastic articles. The
term "plastic" is to be broadly interpreted herein to include
any deformable materials including rubber, metals which are
surface textured by dies, and metals, fabric or paper which are
textured or embossed by means of rolls.
In keeping with the foregoing there is provided in
accordance with the present invention a method for engraving
designs on complex curved work
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1 surfaces such as on molds, dies or the like tha-t can be etched
with a suitable etchant, said work surfaces being employed Eor
producing embossed designs on the corresponding complex curved
surfaces of products formed from deformable materials, said
method comprising the steps of:
preparing a master transparency from art work comprising
the desired design;
exposing transfer material to said design on said master
transparency, said transfer material comprising an emulsion, the
exposed portion of which is resistant upon exposure to the
etchant, said emulsion being on a backing sheet;
removing unexposed areas of said emulsion to define
discrete etchant resistant image elements on said backing sheet;
transferring said image elements from said backing sheet
to said work surfaces;
etching said work surfaces with a suitable etchant; and
removing said image elements from said work surfaces.
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Il BRII,F DESCRIPTION OF THE D~WI~G
1 ¦I The objects, advantages and features of this invention
2 ¦I will become readily apparent from the following detailed
3 ~i description ~hen read in conjunction w;th the accompanying
4 ¦I drawing in which:
li Fig. 1 is a perspective view of a mold cavity ~aving a
6 ¦~ pattern formed on its surfaces by means o~ the present invent;on;
7 I Fig. 2 is the original.copy of the design to be embossed
8 I, onto the mold sur~aces;
9 I Fig. 3 shows the negative made from ~.he oxig-Lnal copy o~
i Fig. 2;
11 il Fig. 4 is a fragmentary view with partial sep~ration
12 Ij showing the transfer material used or the invention;
13 1I Fig. 5 is a perspective view of the arrangement for
14 ll exposing the transfer material to the design;
, Fig. 6 shows the clear protective film being removed
16 I from exposed emulsion;
17 ! Fig. 7 is a perspective view of the developing step;
18 , Fig. 8 is an enlarged ~ragmentary perspective view of
19 the polyester backing sheet with the acid resistant design
elements thereon;
21 Fig. 9 is a fragmentary sectional view of a portion of
22 a mold showing the minutely roughened surface thereof;
23 Fig. 10 is a fragmentary sectional view of a mold surface¦
24 j on an enlarged scale showingthebacking sheet and design,elemen-ts;
~ against the mold surface together with the burnishing step ior
26 ¦ transferring the design elements from the backing sheet to the
27 j mold surface;
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1 iI ~ig. 11 shows the backing sheet being removed from the
2 , transferred design elements;
3 ll Fig. 12 is an enlarged fragmentary sectional view showing
4 1l the mold surface at the end o~ the etching step; and
I Fig. 13 shows the mold surface of Fig. 12 a~ter removal
6 I of the acid resistant design elemen~s.
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j DESC~IPTION OF THE PREFERRED EMBODIMENT
7 ! With reference now to the drawîng and more particularly
8 ¦I to Fig. 1 thereo~, there is shown a mold cavity 21 having
9 ¦l internal wall surfaces 22 with decorative patterns 23 embossed
~I therein. For purposes of this description, a relatively simple
11 ,I pattern having the letter "E" flanked by decorative areas is
12 ¦' sho~. Of course, very intricate sur~ace textures,-p,atterns or
13 ¦~ designs may be used. It will be understood by those skiiled in
14 ¦¦ the art that any design capable of being photographically or
15 ! otherwise reproduced may be formed as a design in relief on the
16 inner surface of the cavity of a mold so that articles ~ormed in
17 the cavity will have the design embossed therein as an in-tegral
18 part of their outer surface.
lg li The original copy 24 (Fig. 2) from which the master film
~j negative 25 (Fig. 3) is to be made is nor~ally black and white
21 I art work. The copy may be of any desired size and will often
22 i be larger than the actual embossed design so that it can be
23 1~ reduced photographically and stlll reta~n desired iine lino
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l ~ quality. The master film negative is made rom the original
1 art work by conventional photographic procedures. The film is
3 ! sho~n herein as a negativebut a positive transparency may be used
4 ~l if desired. Photomechanîcally imageable transfer material 26
1~ sho~n in Fig. 4 is then exposed as shown in Fig. 5~ An opaque
6 ¦I masking paper28 provides the support for the transfer material 26-
7 I which is comprised of a clear protecti~e liner 27, emulsion
8 ! layer 31 and polyester backing 32, with the clear liner in
~ conronting relationship with the masking paper. On top o:E
transfer material 26 is master negative 25 and on top of that
11 is glass plate 33. A conventional light source 34 provides the
12 radiation for exposing the emulsion in the transfer material to
13 ~, the pattern of negative 25. Examples of light sources will be
14 1l, set forth hereinbelow. When exposure is complete, the clear
¦, liner 27 is peeled away from the exposed emulsion as shown in
16 I~, Fig. 6, leaving the exposed emulsion 31 on polyester backing
17 ll sheet 32. Liquid developer 35 is then poured onto the ex`posed
18 11 transfer material and an appropriate tool such as a pad or a
19 ¦ brush 36 is used to spread the developer evenly over the exposed
20 - ¦ surface to facilitate development of the emulsion as -indicated
21 ¦ in Fig. 7. ~hen the image is fully visible, the transfer
22 , material is rinsed with water and dried. At this point (see
23 ~I Fig. 8), the transfer material 26 comprises polyester backlng
24 ¦¦ sheet 32 and acid resistant transferable material 37 in discrete
¦1 areas in the form of the pattern desired. The material ~7 thus
26 ¦I formed has the proper de~ree of tackiness to enable it to adhere
27 ¦! to the mold surface without being so soft as to flow when sub3ect
28 I to pressure during ap-lication to the mold.
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1 ¦~ A fragmentary sectional view of a portion of a mold
2 1' cavity is shown in Fig. 9. Inner surface 22 of mold 21 has an
3 ~ overall "tooth" or minutely roughened surface which may be formed
4 ,¦ by subjecting the surface to a mold acid bath so as to etch the
¦I surface and condition it for reception of the acid ~esistant
6 l1 transfer material. Other suitable means for roughening the
7 ~, surface may be used, including both mechanical and chemical
8 jj means. However, it ~las been found that this process will work
9 ¦I well on roughened or Oll polished surfaces and all intermediate
¦ surface textures. The backing sheet and transfer material
ll j elements are applied to the surface of the mold as shown in
12 i Fig. lO so that the transfer material 37 makes intimate contact
13 ~i with surface 22. The transfer material is actually transferred
14 ~, from the backing sheet to the mold surface by burnishing as
l, shown. Stylus 41 has a smooth, blunt end 42 which enables the
16 ,~ operator to provide a relatively large pressure to a relatively
17 ¦ small area to thereby transfer the acid resistant material,
18 'i which is hard to the touch but adherent to the mold surface
l9 ~, ~Jhen burnished, from the backing sheet. Other stylus shapes
j may be used, but it will generally be a blunt ended instrument.
21 I As the burnishing step progresses, the image ~ill take on a gray
22 I appearance through sheet 32 indicating that the transfer material
23 elements are being separated from the skeet and transferred onto
24 li the surface of the mold. When transfer of the design elements
~ has been accomplished, the backing sheet is simply remov,ea, since
2~ ¦¦ it does not adhere to anything after transfer, as shown in
27 !I Fig~ ll, leaving the acid resistant transfer material 37 in the
28 il desired pattern on surface 22 of the mold. It has been found
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1 ! that when sufficient pressure has been applied to cause the
2 ll acid resistant material 37 to adhere to the mold surface, it has
3 ¦~ separated from the backing sheet. The acid resistant material
4 I will adhere to one surface or the other.
¦ An etching solution 43, normally acid based and having
6 I properties appropriate for the material o~ the mold, is applied
7 I to the mold surface or sufficient time to etch away the mold in
8 1l areas not protected by ~he acid resistant transfer material 37,
9 ¦¦ leaving raised areas ~4 as shown in ~'ig. 12. I~hen this has been
accomplished the acid resistant materi.al may be removed
11 mechanically by an abrasive or by an abrasive in combination
12 with a solution such as alcohol to weaken the bond with the mold ,
13 !I surface, leaving the mold with the design embossed thereon as
14 !i raised areas 4~ in Fig. 13. A typical e~ample of a completed
15 ¦I mold is shown in Fig. 1.
16 ll It will be appreciated that the present inventîon elimi- !
17 il nates several intermediate steps of the prior art, specifically
18 etching oE the zinc trans-Eer plates, pulling of the wax tissue
19 transfers therefrom, and application of a release agent to
separate the tissue from the wax pattern applied to the mold
21 surface. This invention proceeds directly from photographic
22 exposure of the transfer material to the application of the
23 ¦ design onto the surface of the mold.- Not only is processing time;
24 ¦ significantly reduced but, more lmportantly, quality can be
I improved by elimina-ting some oE the steps in the prior ar-t
26 ¦i processes, each of which may lead to loss of pattern definition.
27 Ij Further, by proceeding directly from the photographic step to
28 applic-tion of tbe patte n to the mold surfacc, exceplionally
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1 ll fine detail can be included in the design which will faithfully
2 ¦l be reproduced on the item made and surface textured within the
3 ¦I mold cavity.
4 ! Ano~her factor in being able to maintain the fine detail
5 ! of the original art work in the finished mold is the exposure
6 I parameters. For example, over exposure, either in time or in
7 I light intensity, can result in the transfer material being too
8 ¦ hard to properly adhere to -the mold sur~ace, that is, it will be
9 ~ lacking the necessary characteristic of tac~iness. On the other
I hand, too little exposure, while sufficient to create pattern
11 ¦ definition on the transfer material, may resuLt i.n soft acid
12 j resistant pattern material 37 which does not readily separate
13 li from the backing sheet as a consequence of the burnishing step,
14 ¦~ and at the same time is flowable under burnishing pressure.
¦' This could effectively destroy fine pattern definition. Further- i
16 ¦ more, under exposure may prevent proper development o the
17 ~'~ pattern material so that its acid resistant characteristic is
lS !¦ inadequate, that is, even if it could be transerred to the mold
19 ¦ surface, it would not function properly in masking the desired
I areas of that surface against acid etching. Thus, if the correc~
21 degree o~ tackiness is not achieved, the resist may fail during
22 the etching step resulting in a damaged mold. Optimum tackiness
23 for a làrge majority of applications, using an 11 inch by 14 inch
24 film (27.94 by 35.56 mm) may be achieved by means o- a light
¦ source consisting of four &0 watt, 120 volt, ultraviolet
26 ! fluorescent tubes spaced from the transfer material by 1.5 inches
27 I (3.81 mm) for about 45 seconds. The exposure time may vary
2~ 1l between 30 and 90 seconds in actual practice. A typical,
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1 '; suitable, commercially available exposure unit is 3M ~odel
2 ll, EU-~000, which may be employed to achieve the desired exposure
3 ll, characteristics specified abovè. It should be recognized that
4 ~I the above exposure parameters are examples only and many combi-
1i nations of light sources, distances and exposure times may
6 i! produce useful results.
7 ~! An example of the material suitable for use as the
8 ~I trans~er material is a product sold under the name I.N.T. by
9 ¦¦ 3~1 Company. A suitable developing solution for the material is
¦¦ the 32~ Brand In~age'N Transfer Developer. Tests have shown that
~ the trans~er material 37 is cibout 0.5 mil (0.0127 mm) thick and
12 ¦I can withstand various etching formulations which are known for
13 1i, particular mold surface materials which etch to a depth appro-
14 I priate for the particular pattern requirements and type o~ metal
15 li being etched. It will be readily appreciated by ~hose skilled
16 ! in the art that the depths of etch required for embossed or
17 , molded-in textured patterns are signi~icantly greater -than the
~8 i! depths required for gravure or lithographic printing suraces
l9 ¦~, so that the processing considerations are significantly dif-ferent~
~¦ when preparing a mold for textured patterns. The typical dep-~h
21 1l of etch ranges between 0.003 inch (0.00762 mm) to 0,015 inch-
22 I (0.038l mm), depending upon type of pattern, product application,
23 ! and aesthetic considerations, among others. However, heavier,
~4 ! coarser patterns may be etched to depths at least as great
, as 0.05 inch (0.127 mm). It may be said that etching in~olved
26 I in graphic techniques relates to two dimensional considerations
27 I while the textured molds of this invention are concerned with
28 1l three dimens}ons.
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l l' The process of this invention may be used on all co~on
2 ¦ mold-making materials, such as pre-hardened steel (an example
3 ~ being P20), hardened tool steels (such as S-7), aluminum (6061
4 I for example)t and beryllium copper, among others.
5 I It should be recognized that the above materials and
6 ! specifications are examples only and are not definitive of the
7 ¦ present invention. In light of the above disclosure, it is
8 ¦ likely that modifications and i~provements will occur to those
9 1 skilled in the art which are within the scope o~ this in~ention.
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