Evaporator body with titanium hydride coating, method for the production and usage thereof

Abstract

An evaporator body for a PVD coating system comprises a basic body and an evaporator surface, to which a titanium dihydride layer is applied. A titanium hydride layer comprises an organic carrier agent and titanium hydride as the single inorganic solid. The thickness of the layer is less than or equal to 10 m.

Claims

1. An evaporator body for a PVD coating system comprising a basic body, evaporator surface on the basic body, and a wetting layer over the evaporator surface, the wetting layer comprising a titanium-aluminum alloy containing one or more Ti.sub.xAl.sub.y phases.

2. The evaporator body of claim 1, wherein the titanium-aluminum alloy comprises a TiAl.sub.3 phase.

3. The evaporator body of claim 1, wherein the wetting layer is operable to achieve a homogeneous distribution of molten aluminum over the evaporator surface.

4. The evaporator body of claim 1 further comprising an intermediate layer between the evaporator surface and wetting layer.

5. The evaporator body of claim 4, wherein the intermediate layer comprises titanium diboride and titanium nitride.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Further features and advantages of the invention are derived from the following description of one non-limiting embodiment with reference to the attached drawing. The drawing shows the following:

[0043] FIG. 1 shows the schematic representation of an evaporator body of a PVD coating system in a cross-section; and

[0044] FIG. 2 shows a schematic representation of a partial view of the evaporator body in a cross-section.

DETAILED DESCRIPTION

[0045] The evaporator body 2 shown in FIG. 1 has a basic body 4, which is formed as a hot-pressed ceramic body with the main components boron nitride and titanium diboride as the electrically conductive component. The basic body 4 has a specific electrical resistance ranging from 600 to 6000 cm. The portion of each of the two components in this case is about 50% by weight.

[0046] The evaporator body 2 typically has a length of about 130 mm, a width of about 30 mm, and a height of about 10 mm. On its upper side, the evaporator body 2 has an evaporator surface 6, which, in the exemplary embodiment, is formed by a cavity 8 placed in the surface. The cavity 8 in this case is defined by a circumferential edge 10.

[0047] The base of the cavity 8 is equipped with a wetting layer 12, which is formed as a titanium/aluminum layer. An intermediate layer 14 comprising titanium diboride and titanium nitride may be formed at a boundary surface between the wetting layer 12 and the basic body 4.

[0048] During operation in a PVD coating system, aluminum is added to the evaporator surface 6, for example as a rod or wire, and melts there such that the molten aluminum is then distributed over a large surface of the evaporator surface 6 and wets it. A good wetting behavior is then achieved by the wetting layer 12. The evaporator body 2 is heated by an electrical current typically to 1400 to 1700 C., which is introduced through the evaporator body 2. The molten aluminum evaporates under a vacuum and coats a substrate, which is not shown in more detail here.

[0049] FIG. 2 shows a cutout of the evaporator body 2 according to the invention in the starting state, before delivery to the customer.

[0050] A titanium hydride layer 16 is placed onto the evaporator surface 6. The titanium hydride layer 16 comprises a matrix made up of an organic carrier agent 18 and a powder comprising titanium hydride 20 dispersed in the carrier agent 18. The titanium hydride 20 is the single inorganic solid in the titanium hydride layer 16. A titanium hydride layer 16 has a thickness of less than or equal to 10 m, or preferably from 2 to 8 m.

[0051] The powder particles of the titanium hydride 20 may have a granule size of preferably less than 0.04 mm. With powders of this granule size, a homogenous distribution can be achieved in the carrier agent matrix.

[0052] The organic carrier agent 18 preferably comprises a synthetic resin, or especially preferably a physically drying synthetic resin. Especially preferably, the organic carrier agent is a synthetic resin based on chlorinated rubber, polyvinyl chloride (PVC), vinyl polymers, styrene butadiene copolymers, and silicones, or mixtures thereof. More preferably, the organic carrier agent is a PVC synthetic resin.

[0053] In order to produce the coated evaporator body, the titanium hydride 20 and the organic carrier agent 18 are suspended in an organic solvent. The solvent is preferably selected from the group of aliphatic ketones, esters, and ethers, the mineral oils, and aromatic hydrocarbons, as well as mixtures thereof. The solvents facilitate the dispersion of the powdery titanium hydride 20 in the organic carrier agent 18. Especially preferably, the titanium hydride is suspended in a varnish, which contains the organic carrier agent as a binding agent.

[0054] The portion of titanium hydride in the suspension comprising solvent, organic carrier agent, and titanium hydride is preferably from 5 to 15% by weight in relation to the total weight of the suspension, or more preferably from 8 to 12% by weight, and especially preferably at about 10% by weight.

[0055] The suspension comprising organic carrier agent, titanium hydride, and organic solvent is preferably applied to the evaporator surface 6 in a printing process, or particularly in the so-called pad printing process. In doing so, the suspension is initially held with the assistance of a suction-capable, for example spongy, print body, and the print body is then pressed against the basic body 4 in the area of the evaporator surface 6 such that the thin, maximum 10-m-thick titanium hydride layer 16 is formed. The suspension in this case has low viscosity in the starting state and practically a watery consistency.

[0056] The coating weight of the suspension is preferably about 1 to 5 mg/cm.sup.2, or more preferably between about 1 and 3 mg/cm.sup.2, and especially preferably from about 2.1 to about 2.5 mg/cm.sup.2.

[0057] For application in a PVD coating system, the evaporator body 2 is by means of resistance heating heated to a temperature of greater than 1000 C., or preferably to a temperature ranging from 1400 to 1700 C. upon its first use in the coating system. As shown in FIG. 1, upon heating of the evaporator body 2 with a basic body 4 comprising TiB.sub.2/BN at the boundary surface to the titanium hydride layer, an intermediate layer 14 comprising TiB.sub.2/TiN is formed. The organic carrier agent is decomposed and/or evaporated due to the heating.

[0058] In the presence of aluminum, there is a conversion of the aluminum with the titanium hydride with the formation of the wetting layer 12 on the evaporator surface 6 or the intermediate layer 14. The aluminum can be placed on the evaporator surface or added to the heated evaporator body even before heating of the evaporator body.

[0059] The coating layer 12 is a titanium/aluminum alloy layer, which contains at least one or more Ti.sub.xAl.sub.y phases. In particular, a TiAl.sub.3 phase may be formed.

[0060] This wetting layer 12 promotes the initial wetting of the evaporator surface 6 with aluminum. The ability to wet the evaporator surface remains stable when additional aluminum is added. The aluminum melt follows the already existing wetting layer 12 and is distributed homogenously over the entire evaporator surface 6. Merely gradual wear occurs over the service life of the evaporator body 2, which typically comprises several operating hours.

[0061] Despite the low layer thickness, the wetting layer 12 exhibits particularly good first-wetting behavior for aluminum, such that a homogenous distribution of the molten aluminum is achieved on the evaporator surface and thus a high rate of evaporation and coating can be achieved. Simultaneously, the homogenous wetting and distribution of the aluminum on the evaporator surface 6 ensures even loading of the basic body 4, because the formation of so-called hotspots are avoided. Such type of hotspots particularly result from the lack of cooling of individual spots on the evaporator surface due to flawed wetting and can lead to premature wear. Finally, the production of the coated evaporator body is easier and more economical, because it is not necessary to use complex combined material mixtures.

[0062] The evaporator body according to the invention can thus preferably be used for the metallization of substrates such as flexible plastic films and other bodies made of plastic with aluminum through physical vapor deposition from the gas phase (PVD).