Solid material comminution or disintegration – Processes – By operations other than force of contact with solid surface
Utility Patent
1999-03-25
2001-01-02
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
By operations other than force of contact with solid surface
Utility Patent
active
06168100
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved method for producing embossed metallic flakelets to be used as a hologram pigment.
2. Description of the Related Art
Metallic flakelets having emboss patterns have conventionally been known as the material of a hologram pigment. For example, Japanese Patent National Publication of Translated Version No. Hei 8-502301 discloses a method of producing a metallic flake pigment with an embossed pattern. This prior method will be described briefly with reference of
FIG. 8
of the accompanying drawing of the present specification. In the
FIG. 8
, a peel coating
52
soluble in a predetermined solvent is formed over an embossed surface of a carrier sheet
50
having emboss patterns at least one surface. The thickness of the peel coating
52
is uniformed by applicator
54
. On this peel coating
52
, a metallic film is adhered in such manner that the emboss patterns of the carrier sheet
50
is copied onto the metallic film. Then, the peel coating
52
is dissolved in a p redetermined solvent, whereupon the metallic film on which the emboss patterns have been formed is peeled off. The resulting embossed metallic film is then pulverized into embossed metallic flakelets whose average size is within the range of 25 &mgr;m to 50 &mgr;m. The pigment is produced using the thus prepared flakelets.
However, this prior method includes indispensable steps of forming the peel coating
52
over the embossed surface of the carrier sheet
50
, forming the metallic film over the peel coating
52
, dissolving the peel coating
52
to peel off the metallic film, and then pulverizing the peeled metallic film into flakelets. As a consequence, the whole producing process is extensive and meticulous, thus deteriorating the productivity. Especially in the process step in which the metallic film is adhered onto the peel coating
52
, it requires evaporation after vacuum drawing in a vacuum container, which additionally needs a vacuum exhaust facility, and also it takes long time to form the metallic film. Further, in the peeling step, the peeling coating
52
is dissolved using, for example, a solvent. Accordingly the whole producing process is considerably complex, from which unexpected cost saving could not be expected.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for producing embossed metallic flakelets which improves the productivity, simplifies processing steps, and ultimately reduces production costs.
In order to accomplish the above object, according to the present invention, there is provided a method of producing embossed metallic flakelets, wherein a metallic foil is pressed on its opposite surfaces between a cooperating pair of dies, which respectively have two mutually complementary embossed pattern, to thereby form on the surfaces of the metallic foil undulations corresponding to the embossed pattern of the dies.
It may be preferable for the method to comprise steps of soaking the metallic foil, which has been pressed into a thickness of less than 2 &mgr;m and left adhered to the dies, in a liquid; and pulverizing the soaked metallic foil into metal flakelets of an size of less than 50 &mgr;m by applying ultrasonic waves to the metallic foil simultaneously with removing the metallic foil from the dies.
In another preferred aspect, the liquid has a surface tension of less than 0.04 N/m.
According to still another preferred aspect, the metallic foil is previously cooled to a temperature equal to or less than −50° C. during the pulverizing step.
According to a further preferred feature, the metallic foil is heated during the pressing.
It may also be preferable for the dies and/or the metallic foil to be surface-treated so as to have a low surface energy before pressing step.
As an additional preference, the metallic foil may have pin holes of a size equal to or less than 10 nm at a density of 800 to 9,000 holes per mm
2
.
However, it may also be preferable for the method to comprise steps of applying a surface active agent over the pressed metallic foil; and then pulverizing the metallic foil into metallic flakelets by applying ultrasonic waves to the metallic foil while being soaked in a liquid.
In another aspect of the present invention, the dies are pressed against both sides of the metallic foil while gradually receiving pressure via reduction rolls.
The reduction rolls may rotate in the same direction as the longitudinal direction of the embossed metallic flakelets.
In addition, tensile stress absorbing plates may be disposed between the reduction rolls and the dies.
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Kato Akira
Katsumata Takatoshi
Nakanishi Masatsugu
Okochi Yukio
Yamamura Yoshihiro
Oliff & Berridg,e PLC
Rosenbaum Mark
Toyota Jidosha & Kabushiki Kaisha
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