WO2008135318A1

WO2008135318A1 - Device for dynamically controlling the temperature of a mould

Info

Publication number: WO2008135318A1
Application number: PCT/EP2008/053790
Authority: WO
Inventors: Eggo Sichmann; Marco Huber; Frank Martin; Peter Wohlfahrt; Michael Reising
Original assignee: Singulus Technolgies Ag
Priority date: 2007-05-07
Filing date: 2008-03-31
Publication date: 2008-11-13
Also published as: DE102007021250A1

Abstract

The invention relates to a device for the alternate heating and cooling of a component. The device has a unit for holding a component, a unit for cooling said component by means of a cooling surface that is in thermal contact with the component, the latter being held at a distance from the cooling unit by a spring unit, and a heating unit for heating the component.

Description

Device for the dynamic tempering of a die

The present invention relates to an apparatus for patterning a substrate, in particular for embossing an information layer of an optical data carrier.

The individual information layers of multilayer optical data carriers, in particular BIUrray Dual Layer Discs (BD DL), are generally produced by embossing into a polymer layer by means of a die having the information coded as pits.

For embossing the structure, the template is pressed into the polymer layer, for example a cured or partially cured lacquer, which has previously been applied to a substrate by a spin-coating process and cured. In the case of a UV-curable lacquer, a crosslinking polymerization reaction is started for this purpose, for example by UV radiation. In multilayer optical data carriers, the individual information layers are usually separated by separating layers which are a few micrometers thick. Also, the release layers are usually prepared from a curable varnish, which is applied by spin coating on an already prepared information layer. The structure of the following information layer can then formed by a stamping process on the free surface of the cured paint.

In order to be able to emboss structures into the polymers, the template must be heated to a temperature above the glass transition point TQ of the polymer before embossing. In order to maintain the embossed structure permanently, the template must be cooled to temperatures well below T _Q before removal from the polymer layer. For a stamping process so a dynamic temperature of the die is necessary.

hi known embossing devices, the die is mounted on an anvil, which has a good thermal conductivity. For example, the anvil can be made of copper. The anvil itself is tempered with water. The temperature of the die is effected by heat conduction and heat transfer between anvil and die. Since not only the workpiece to be tempered, namely the die, but the entire anvil is tempered, the heat capacity of the anvil must be overcome in addition to each heating and cooling cycle; this requires a relatively long time. In addition, there are the necessary switching times between cooling and heating. The process time of such a tempering cycle is on the whole of the order of one minute. Since the actual embossing only takes about one second, the time required solely for cooling and heating the die slows down the embossing process considerably.

The prior art DE 197 37 471 Al has become known. It is therefore an object of the present invention to provide an apparatus for patterning a substrate in which the heating and cooling times, and thus the process times are abbreviated.

This object is solved by the features of the claims.

The invention is based on the basic concept of providing a device for alternately heating and cooling a component, in which the component is spaced apart from the device for cooling the component by means of a spring device. According to a preferred embodiment of the invention, the device is a Structuring device, which is particularly suitable for embossing Blu-Ray dual layer discs. The component and in particular the die is thus separated by the spring means of the cooling device. This is preferably done by a spring-mounted storage of an internally centering die holder, as well as a spring-mounted ring that holds the die at the outer edge. The distance between the die and the cooling device or the anvil forming the cooling device in a relaxed state is preferably a few millimeters. In order to ensure a good thermal decoupling of the die from the anvil, the die holder is preferably made of a thermally insulating material, such as plastic. Thus, the anvil during the entire embossing process at a constant temperature, namely the cooling temperature can be maintained. The heating of the thermally decoupled from the anvil die is done by an additional heater. This can be for example an induction heater, which is pivoted in front of the die during heating. The inductive heating is particularly efficient for ferromagnetic materials, so that the power of the inductive heating is almost completely absorbed by the matrix. Due to the direct heating of the matrix by induction and by a sufficiently large air gap between the die and the anvil, there is no significant heating of the anvil, so that only the die and no additional parts of the device is heated.

During each stamping process, the die must be cooled again after heating. According to the present invention, die and anvil are thermally contacted for cooling. This happens automatically when the means for holding the substrate brings the die into contact with the substrate. Once the substrate is driven against the die, the springs are tensioned and the die pressed against the cooled anvil. Cooling therefore starts automatically at exactly the time of the process from which it is needed.

When the desired demolding temperature is reached, the substrate is separated from the die. The springs press the die again at a distance from the anvil, so that the cooling of the die, and thus the substrate automatically takes place only up to the desired demolding temperature. The die is thus not unnecessarily undercooled. Optionally, the necessary cooling time of the die can be further reduced by metallizing the layer to be embossed prior to embossing. This can be done by applying a few nanometers thick layer, such as aluminum or silver by sputtering. The additional metal layer can support demoulding or demoulding at higher temperatures. A higher demolding temperature reduces the necessary cooling time, thus reducing the total process time.

The forced decoupling or contacting between the die and the anvil during the structuring process guarantees an exact dosage of the required cooling capacity, as well as an instantaneous start and stop of the cooling. Since the die shields the anvil from the inductive heater, only the die is heated. Furthermore, this shield allows the use of electrically conductive materials, such as metals, for the execution of the cooling anvil. The anvil is therefore preferably made of copper.

Since the anvil is kept permanently at a constant temperature, preferably the cooling temperature or even below, no heating or cooling power is wasted for him.

As an alternative to heating the matrix by means of induction, other types of heating, for example radiant heating, can also be used. This can be used, for example, if the die consists of electrically non-conductive substances.

The present invention will be explained in more detail below with reference to the single figure, wherein Figure 1 shows schematically a preferred embodiment of a device according to the present invention.

According to FIG. 1, the die 1 is held by a die holder 2. The die holder 2 is spring mounted in the embodiment shown in Fig. 1. To the die holder 2 an anvil 3 is arranged. The anvil 3 is cooled by a cooling device (not shown). This can be realized, for example, by providing cooling channels in the anvil 3. In order to securely space a die 1 held by the die holder 2 from the anvil 3, in addition to the sprung mounting of the die holder itself, a spring-mounted ring 6 is provided which holds the die 1 at the outer edge.

The die holder 2 opposite a press 4 is arranged, on which the substrate 5 is located, in which the desired structure is to be embossed. Fig. 1 indicates the movement of the press 4 during the patterning operation, wherein the left side of the figure shows the state during pressing, and the right side shows the state in which the press 4 is separated from the die hardner 2. On the right side of Fig. 1 is thus seen that the die 1 is held in the relaxed state at a certain distance from the anvil 3. If the press 4 presses the substrate against the die I _3, as shown in the left-hand part of FIG. 1, the die 1 and the anvil 3 come into contact and the cooling of the die 1 and thus also of the substrate 5 begins. Alternatively, the device for holding the die 1 can be designed to be movable, so that it is pressed against the substrate 5 when pressed, which is arranged on a (stationary) substrate holder.

For heating the die 1 in the relaxed state, ie in the state shown on the right side of FIG. 1, a heating device is additionally provided, which is not shown in FIG. Preferably, in the case of an electrically conductive, in particular ferromagnetic die 1, an induction heater for heating is pivoted in front of the die 1, so that the die 1 is located between the heater and the anvil 3.

Due to the direct heating of the die 1, without the anvil 3 must be mitgesheizt, a heating time of about 0.5 s can be achieved. Further, since the cooling of the die 1 by the anvil 3 automatically starts as needed, the time required for patterning a substrate 5 is greatly shortened over known devices. By appropriate design of the inductor power almost any embossing temperatures can be achieved in heating times of less than 1 s. The device according to the invention can thus be used for embossing a large number of fusible materials. With the device according to the present invention, any nano or microstructures can be embossed. The use is therefore not limited to the embossing by means of cylindrically symmetric matrices, as is the case with the embossing of optical data carriers. By a corresponding geometric design of the inductor also arbitrarily shaped workpieces can be heated.

The device according to the present invention can be used in addition to the embossing for other methods of surface structuring, if they require dynamic temperature control in a short cycle time. Examples include the injection molding of small structures or structures of high aspect ratio, or the injection molding of thin-walled bodies having a high ratio of the areas to the wall thicknesses. The use of the device according to the invention for structuring the information layer of Blu-Ray dual-layer discs is preferred. However, the method also allows the construction of optical data storage with any number of layers.

Claims

claims

Anspruch [en] An apparatus for alternately heating and cooling a die (1) for patterning a substrate (5), comprising (a) holding means (2) for holding the die (1),

(b) cooling means for cooling the die (1) via a cooling surface in thermal contact with the die (1), the die (1) being spaced from the cooling means by spring means (6), and

(c) a heater for heating the die (1).

2. Device according to claim 1, wherein the cooling device comprises an anvil (3).

A device according to any one of claims 1 or 2, further comprising holding means (4) for holding the substrate (5) and bringing the substrate (5) into contact with the die (1).

4. The device according to claim 3, wherein the holding device (4) for holding the substrate (5) is adapted to press the substrate (5) against the die and thus to emboss the structure in the substrate (5).

5. Device according to one of claims 1 to 4, wherein the holding device (2) for holding the die (1) is spring-loaded, and the spring means (6) has a spring-mounted ring which holds the die (1) at its outer edge.

6. Device according to one of the preceding claims, wherein the spring means (6) holds the die (1) at a distance of less than 10 mm, preferably 2-7 mm from the cooling device.

7. Device according to one of claims 1 to 6, wherein the cooling device is cooled by means of cooling water.

8. Device according to one of the preceding claims, wherein the holding device (2) for holding the die (1) is made of a thermally insulating material.

9. Device according to one of the preceding claims, wherein the die (1) is made of a ferromagnetic material and the heating means heats the die (1) by means of induction.

10. Device according to one of the preceding claims, wherein the heating device for heating the die (1) in front of the die (1) can be pivoted.

11. Device according to one of the preceding claims, wherein the substrate (5) is a blank for producing an optical data carrier, in particular a Blu-Ray

Dual Layer Disc is.

12. A method of structuring a substrate (5) by means of the device according to one of the preceding claims, comprising the steps of: - heating the die (1) by means of the heating device;

- Pressing the substrate (5) against the die (1) and thereby cooling the die (1) by bringing the cooling surface in thermal contact with the die (1) by bringing the cooling surface in thermal contact with the die (1), so that the substrate (5) is cooled by contact with the die (1).

The method of claim 12, wherein the substrate (5) is metallized prior to the patterning process.

14. The method of claim 12 or 13, wherein by the method, an information layer is embossed in a blank for producing an optical data carrier.