Emboss pattern processing apparatus

Details Emboss pattern processing apparatus Emboss pattern processing apparatus

2001-05-31

2003-05-27

Mackey, James P. (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

With apparatus assembly or dismantling means or with idle part

For press shaping surface

C425S363000, C425S373000, C425S385000

Reexamination Certificate

active

06568931

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of an emboss pattern process, emboss pattern processing apparatus, and an embossed sheet, which is used for the production of an optical precision embossed sheet, such as a reflector, a prism sheet, a fresnel lens and so on.
2. Description of the Related Art
In recent years, a reflective ability sheet (a plastic reflection sheet), undergoing a micro-prism process on the surface of a thermoplastic resin sheet, has been employed in the reflection panel field, the fashion field, an architecture field and so on.
In the United States, the use of a glass bead type and a cube corner type are approved as the aforementioned reflective ability sheet. Commonly, the reflective ability sheet of the glass bead type is superior in short-distance visibility, and the reflective ability sheet of the cube corner type is superior for long-distance visibility and luminance created by optical reflection.
In the production of the reflective ability sheet of the cube corner type, an emboss pattern on an emboss pattern forming die (or a pattern embossing die) should be precisely transferred onto the thermoplastic resin sheet.
Therefore, it is especially important that the thermoplastic resin sheet is pressed onto the emboss pattern forming die (or the pattern embossing die) with appropriate pressure, and further, the pressure is continuously added for a predetermined period of time.
As conventional methods for producing the reflective ability sheet serving the above requirement, for example, a continuously pressing method (Japanese Patent Application Publication No. Sho60-56103), a belt method (Japanese Patent Application Publication No. Hei5-17023), and a roller method (an example relating to
FIG. 9
in Japanese Patent Application Publication No. Hei3-43051) are proposed.
With the continuously pressing method, emboss pattern forming dies (or pattern embossing dies) are sequentially pressed onto a sheet material of solid phase, laid on a belt and continuously supplied with plural pressing means having a heating or cooling function to transfer patterns onto the sheet material.
With the belt method, a belt having an emboss pattern and a thermoplastic resin sheet are pressed between a pair of rollers to transfer patterns onto the sheet.
With the roller method, an emboss pattern is transferred onto a sheet by using a roller forming the emboss pattern on its outer circumferential face.
According to the aforementioned continuously pressing method, the production speed is slow and apparatus is complicated and large in size.
According to the belt method, the belt itself carries the emboss pattern, so that apparatus is large in size, and a disadvantage arises concerning the endurance of the belt as a pattern embossing die.
And, according to the roller method, the production speed is faster and the endurance is better. But, the temperature of the sheet is not effectively controlled to increase when the emboss pattern is transferred onto the sheet and decreased when the sheet after being embossed is peeled from the roller, resulting in disadvantages concerning the pattern reproducibility and the peeling properties. In other words, the apparatus is not structured to have a large difference in temperature between an area of the roller where the pattern is transferred, and an area of the roller where the sheet is peeled, thus not allowing the precise pattern reproducibility and the smoothly peeling properties to be obtained.
And further, the reflective ability sheets obtained by the conventional producing methods are not satisfied in regard to the reflecting properties.
SUMMARY OF THE INVENTION
A method of an emboss pattern process according to the present invention is characterized by including the following steps of: transferring an emboss pattern onto a thermoplastic resin sheet by using an emboss patterning roller; lustering (setting a gloss on) the opposite face of the embossed face of the thermoplastic resin sheet by using a lustering means having a mirror face member; and peeling the thermoplastic resin sheet from the emboss patterning roller at a lower temperature than a temperature for transferring the emboss pattern.
It is advisable that the temperature for transferring the emboss pattern is defined to be more than the Vicat softening point of the thermoplastic resin sheet, though also depending upon the type of resin used, the temperature of the thermoplastic resin sheet before being embossed, and so on. The Vicat softening point is a softening temperature of the thermoplastic resin sheet, in which the measuring method of the above temperature is based on JIS K7206.
A difference in the temperature in the pattern transfer step and the lower temperature than that in the pattern transfer step can be properly defined, for example, more than 10° C., preferably more than 20° C., also depending on the pressure or the type of resin. The difference in temperature of less than 10° C. causes the lack of cooling ability in the peeling step, so that the precise embossed pattern cannot be obtained. The upper limit of the difference in temperature is not especially defined, but it is preferable to be less than 150° C. In the difference in temperature of more than 150° C., the endurance of the roller becomes inferior or the production speed becomes slower, resulting in higher cost.
When the thermoplastic resin sheet is lustered by the lustering means, the face-pressure is more than 0.01 MPa. If the face-pressure decreases less than 0.01 MPa, the uniformity of gloss is likely to deteriorate.
Incidentally, a thermoplastic resin film having a relatively different thickness from the then no plastic resin sheet can be used.
Emboss pattern processing apparatus according to this present invention is characterized by including: an emboss patterning roller for transferring the emboss pattern onto a thermoplastic resin sheet; a lustering means, having a mirror face member, for lustering the opposite face of the embossed face of the thermoplastic resin sheet; and a cooling means for cooling the thermoplastic resin sheet peeled from the emboss patterning roller, to a lower temperature than a temperature for transferring the emboss pattern.
In the emboss pattern processing apparatus according to the present invention, it is advisable that the emboss patterning roller has a roller body having a face for embossing a pattern; and a sealing ring attached on each side face of the roller body, in which the roller body and the sealing ring are formed with a passage for flowing a temperature controlling medium for cooling from the one sealing ring through the roller body to the other sealing ring.
As the temperature controlling medium, water, silicone oil, oil for controlling temperature, or the like can be selectively used.
According to the present invention, the passage is formed along an area of the roller body which is required to be cooled, and the temperature controlling medium with the suitable temperature is flown into the passage, thereby the temperature when the thermoplastic resin sheet is peeled off the emboss patterning roller is decreased to be lower than the temperature when the pattern is embossed. In other words, the aforementioned passage for flowing the temperature controlling medium comprises a cooling means.
The temperature controlling medium with the fixed temperature is continuously flowed from one sealing ring through the roller body to the other sealing ring, thereby allowing the temperature of the area of the roller body which is required to be cooled to be accurately controlled.
The passage in the roller body can be plural passage-tubes formed along and in the vicinity of the outer circumferential face of the roller body.
The diameter of the passage-tube and the number of passage-tubes are selectively decided so that the temperature of the area of the roller body which is required to be cooled is effectively controlled by the temperature controlling medium flown through the aforementioned passage-tubes. And, the suitable dia

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