JP2004039319A - Metal mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal mask capable of forming a precise pattern film as a metal mask for vapor deposition for an organic EL display or the like. <P>SOLUTION: This metal mask having a plurality of through holes and with a plurality of metal layers formed therein is provided preferably with an open-hole forming layer for determining an open-hole dimension, a support layer, and a joining layer for joining the open-hole forming layer and the support layer. At least one of the the open-hole forming layer, the support layer and the joining layer is preferably different from the other layers in its etching characteristic, in the mask. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a metal mask capable of forming a pattern with high precision as a metal mask for vapor deposition of an organic EL display or the like.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a display device represented by a portable information device has been rapidly advanced to full color, small size, and high definition. In the manufacturing process of low-molecular-weight organic EL displays, which are being put into practical use, fine patterns such as light-emitting layers are formed using a vapor deposition mask having a plurality of through-holes. In addition, the metal mask is required to have a small opening pattern and high precision.
The metal mask is a plate-shaped metal provided with a plurality of through-holes, and is formed by depositing an organic substance, an electrode material, and the like on the substrate by a vapor deposition method or the like through a metal mask provided in front of the substrate. Pattern formation corresponding to the hole shape is performed.
[0003]
Such a metal mask having a plurality of through holes is generally manufactured by the following manufacturing method.
First, a metal plate serving as a metal mask is prepared, and after a photoresist film having a desired pattern is formed on the surface of the metal plate and then etched, only a portion not covered with the resist is etched to form a through hole.
At this time, the direction of erosion of the metal mask material by the etching solution is not a single method, but proceeds not only in the thickness direction but also in the plane direction of the plate. Therefore, there is a problem that the through-hole formed by etching has a larger opening area than the original resist pattern.
[0004]
Since the degree of erosion in the plane direction is a major controlling factor in processing time, it is considered that the most effective means to accurately form the hole shape is to reduce the thickness of the metal plate used as the metal mask. Can be
However, if the thickness of the metal plate serving as the metal mask is set to 20 μm or less, the following new problem occurs.
Specifically, the weight of the deposited material becomes excessively heavy with respect to the metal plate serving as the metal mask due to the deposited deposition of the deposited material, causing distortion. Further, since the heat capacity becomes extremely small, there is a problem that distortion due to thermal expansion causes deterioration of positional accuracy of the mask and insufficient separation of patterns due to wraparound of vapor deposition.
When a metal mask is used, a tension is applied in advance to prevent distortion. However, a thin metal mask having a thickness of 20 μm or less has a large elongation with respect to the tension, and a slight non-uniformity of the tension may occur. This causes distortion and makes it difficult to adjust the tension.
As a means for solving the above problems, a method of forming an opening with a thin plate material and reinforcing the opening is disclosed in, for example, JP-A-10-50478.
[0005]
[Problems to be solved by the invention]
The method described in the above-mentioned Japanese Patent Application Laid-Open No. 10-50478 is to partially provide a reinforcing metal wire to prevent bending of a thin metal mask. In such a part, the deposition amount of the deposition material was smaller than that in the part without the reinforcing metal wire, and there was a disadvantage that the thickness of the film became non-uniform.
An object of the present invention is to provide a metal mask capable of forming a pattern with high precision as a metal mask for vapor deposition of an organic EL display or the like.
[0006]
[Means for Solving the Problems]
The present inventor has studied diligently about a method that does not use a wire as a reinforcing material, and a combination of a thin plate material for forming a through hole and a plate material for reinforcement is most suitable. As a result of studying the method of separately etching plate materials for reinforcement, it was found that by adopting a laminated structure of a plurality of plate materials having different etching characteristics as a metal mask plate material, the accuracy of the opening shape was improved, and the metal shape was improved. The inventors have found that the strength of the mask can be greatly improved, and have reached the present invention.
[0007]
That is, the present invention is a metal mask having a plurality of through holes, and the metal mask is a metal mask formed of a plurality of metal layers.
Preferably, the metal mask includes an opening forming layer that determines the opening size, a support layer, and a bonding layer that joins the opening forming layer and the support layer.
Preferably, at least one of the hole forming layer, the support layer, and the bonding layer is a metal mask having etching characteristics different from those of the remaining layers.
More preferably, the bonding layer is a dry film forming layer, and the opening forming layer and the supporting layer are metal masks having different etching characteristics.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
As described above, an important feature of the present invention is that a laminated structure of a plurality of metals is employed as a metal mask plate.
Hereinafter, the present invention will be described in detail.
First, the structure of the metal mask of the present invention will be described with an example.
FIG. 1 is a schematic view showing an example of a cross-sectional structure of the metal mask of the present invention. The metal mask shown in FIG. 1 includes a thin hole forming layer (1), a relatively thick support layer (3), and a bonding layer (2) for bonding the hole forming layer (1) and the support layer (3). Formed of three metal layers of A metal mask can be formed by forming through holes (4) penetrating these layers in the opening forming layer (1), the support layer (3), and the bonding layer (2) by etching.
[0009]
One of the important features in the cross-sectional structure of the metal mask of the present invention is that all the layers constituting the metal mask can be easily etched, so that the opening (4-a) on the opening forming layer side and the supporting layer side The opening portion (4-b) is etched by a different etching pattern, and the hole shape of each hole is different.
In other words, the hole forming layer side opening (4-a) forms a small diameter through hole in the through hole (4), and the hole forming layer side opening (1) has a small thickness. By providing (4-a), it is possible to form an opening with high dimensional accuracy.
The thickness of the hole forming layer (1) is preferably as thin as possible in order to minimize erosion in the planar direction when the opening is formed by etching. By setting the thickness to at least 10 μm or less, the thickness of the through hole is reduced. The dimensional accuracy of the portion (4) can be suppressed to ± several μm.
[0010]
It is preferable that the thickness of the support layer (3) is large in terms of strength. However, if the thickness is too large, a shadow is formed on the through hole (4) at the time of vapor deposition, resulting in non-uniform deposition film thickness. Therefore, it is appropriate to set the length to about 100 to 30 μm which is equal to or less than the minimum length of the through hole (4).
The bonding layer (2) plays the role of a binder for bonding the pore forming layer (1) and the support layer (3), and at the same time, the bonding layer is formed of the pore forming layer (1) and the support layer (3). When the metal having different etching characteristics is used, when forming the through hole (4) by etching, the opening (4-a) on the side of the opening forming layer (1) and the opening (4-b) on the support layer side are formed. ) Also serves as a barrier for etching separately.
In the present invention, since it is necessary to match the thermal expansion characteristics except for the bonding layer, it is preferable that the thin bonding layers have different etching characteristics.
[0011]
Although the above-described three-layer structure is shown as an example of the metal mask of the present invention, a two-layer structure may be used, for example. The combination in this case becomes the hole forming layer and the support layer.
When manufacturing a metal mask having such a two-layer structure, a method in which ordinary metal plates are overlapped and joined to each other to reduce the thickness by rolling, or a method in which a metal is laminated on a support layer by a film forming method may be used. In a method in which ordinary metal plates are overlapped and joined together to reduce the thickness by rolling, in a method in which the thickness of an aperture forming layer is not uniform, or in a method of laminating a metal on a support layer by a film forming method, The metal to be formed is limited, the strip cannot be manufactured continuously, or the manufacturing cost increases.
Therefore, in order to manufacture a metal mask having a two-layer structure, a method of unwinding two metal strips, performing dry etching on the surface to be joined to form an activation surface, and pressing the roll with a roll having a low reduction ratio is used. Is the most preferable method because not only can the strip be manufactured continuously, but also the thickness change between the hole forming layer and the support layer is small.
However, the two-layer structure tends to be warped during pattern deposition due to the difference in thermal expansion coefficient. Therefore, the metal mask of the present invention preferably has a three-layer structure.
Hereinafter, a metal mask having a three-layer structure will be described.
[0012]
As a method of manufacturing a laminated plate for a metal mask having a three-layer structure, a method in which the above-described metal plates are overlapped and joined to each other to reduce the thickness by rolling, a method in which metal is sequentially formed on the surface of the metal foil, a laminated material is used. Unwinding two metal lamination strips as a material, performing dry etching on the surface to be joined, forming an activation surface, and crimping with a roll or the like with a low reduction ratio, a method of forming one or more metal foils in a low pressure atmosphere There is a method in which a third metal is attached and formed on the surface and then joined with a pressure roll.
Among them, a method of dry-forming a third metal on a surface of a pair of metal foils in a low-pressure atmosphere described in Japanese Patent Application No. 2001-162382 proposed by the present applicant and then joining the third metal by a pressure roll is the most productive. Since it is high and the surface roughness of the hole forming layer is better than plating, it is suitable as a method for manufacturing the metal mask laminate.
In addition, since a dry film formation layer is formed by adhesion, a bonding layer having a uniform thickness can be obtained, which is particularly preferable.
[0013]
In the present invention, when at least one of the hole forming layer, the support layer, and the bonding layer has an etching characteristic different from that of the remaining layers, the etching process can be selectively performed.
Among the above-mentioned layers, as a metal material constituting the hole forming layer and the support layer, any metal material having a small coefficient of thermal expansion can be used in order to prevent a deposition pattern from shifting due to thermal expansion. Among them, in consideration of availability and etching characteristics, it is particularly desirable to use an Fe—Ni alloy such as an invar alloy or a 42% Ni alloy. Further, a super-invar alloy to which Cr or Co is added, or an Fe-Ni-Cr-based alloy can also be applied.
[0014]
At this time, if the metal materials used for the hole forming layer and the support layer are different metals and alloys, respectively, and the bonding layer is of the same kind as the metal material used for the hole forming layer and the support layer, the hole forming layer and the support layer are formed. Can be etched separately.
Further, when the opening forming layer (1) and the supporting layer (3) are made of the same material and the joining layer is made of a different metal, not only the opening forming layer and the supporting layer can be simultaneously etched, but also the joining layer can be formed. Other than that, it is necessary to match the thermal expansion characteristics, so it is better to make the thin bonding layer have different etching characteristics. Preferably, the metal material used for the hole forming layer and the support layer is the same kind of metal or alloy, and the bonding is performed. The layers may be of different metals.
[0015]
The material constituting the bonding layer of the present invention is appropriately selected from various metals as needed. For example, when an Fe-Ni alloy is used for the hole forming layer and the support layer as described above, a material having a high adhesive strength to the Fe-Ni alloy and having a different etching property is preferable, so that Ti, Sn, Ag, etc. It is preferable to use metals or alloys containing these as main components.
The thickness of the bonding layer only needs to be able to secure a thickness required as an etching barrier, and a thickness of about 1 μm is sufficient.
In addition, in bonding the hole forming layer and the support layer by the bonding layer, a diffusion heat treatment may be combined to further increase the bonding force. At this time, a diffusion layer is newly formed. In the present invention, this diffusion layer is also defined as a bonding layer.
[0016]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples and drawings.
FIG. 1 is a schematic view showing an example of the metal mask of the present invention. The metal mask shown in FIG. 1 includes a thin hole forming layer (1), a relatively thick support layer (3), and a bonding layer (2) for bonding the hole forming layer (1) and the support layer (3). Formed of three metal layers of
Table 1 shows the material and thickness of the metal mask manufactured as an example of the present invention. FIG. 2 shows a cross-sectional microscope image. The three-layer metal plate of FIG. 2 is a cross-sectional micrograph of a material serving as a metal mask and a schematic view thereof. The upper side has an opening forming layer (1) made of an Fe-42% Ni alloy having a thickness of 10 μm, and the lower side has a 90 μm thickness. A support layer (3) made of an Fe-42% Ni alloy and an extremely thin layer at the center are a bonding layer (2) made of 1 μm Ti.
[0017]
As a method of manufacturing a laminate of a material serving as a metal mask, a Fe-42% Ni alloy (10 μm) serving as a hole forming layer and a Fe-42% Ni alloy (90 μm) serving as a support layer are formed in a low-pressure atmosphere. Of pure Ti was dry-formed (evaporated) on the joining surface of No. 1 and then joined by a pressure roll.
Before joining, each Fe-42% Ni alloy is washed with hydrochloric acid to improve joining strength. Although cleaning with hydrochloric acid is performed in this embodiment, a method such as dry etching that can be processed in a low-pressure atmosphere is also effective in addition to acid cleaning.
[0018]
The three-layer metal plate joined by the above-described method has slightly weaker joining strength as it is, and it was 0.1 kN / m or less in the peeling test. Therefore, by performing diffusion heat treatment in an inert gas atmosphere, the joining strength was increased. It was taken.
In the peeling test after the heat treatment, the 10-μm side Fe-42% Ni alloy, which is the hole forming layer, was broken and could not be peeled off. The heat treatment temperature for diffusion bonding of Ti of the bonding layer to each Fe-42% Ni alloy may be 400 ° C. or higher.
However, when the heat treatment is performed at about 650 ° C., the Fe-42% Ni alloy is rapidly softened. Is good.
[0019]
Openings were formed by selective etching using the above-mentioned three-layer metal plate, and the metal mask shown in FIG. 1 was prepared. Separate etching patterns were used for the openings of the opening forming layer and the support layer. The etching pattern was a delta arrangement, and the width of the opening on the opening forming layer side was 100 μm.
As the etchant, ferric chloride was used for the hole forming layer and the support layer, and 3% of dilute hydrofluoric acid was used for stripping the Ti layer.
The dimensions of the apertures were all within the range of 100 μm ± 5 μm, and a metal mask with high dimensional accuracy could be manufactured for high-definition displays.
[0020]
【The invention's effect】
According to the present invention, the accuracy of a deposition pattern using a metal mask can be remarkably improved, and this is an indispensable technique for practical use of a high-definition organic EL display.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an example of the present invention.
FIG. 2 is a cross-sectional micrograph of a three-layer metal plate for a metal mask of the present invention and a schematic diagram thereof.
[Explanation of symbols]
1. 1. aperture forming layer; 2. bonding layer; 3. support layer; Through hole, 4-a. An opening forming layer side opening, 4-b. Support layer side opening

Claims (4)

A metal mask having a plurality of through holes, wherein the metal mask is formed of a plurality of metal layers. The metal mask according to claim 1, further comprising: an opening forming layer that determines an opening size; a support layer; and a bonding layer that joins the opening forming layer and the support layer. . 3. The metal mask according to claim 2, wherein at least one of the opening forming layer, the support layer, and the bonding layer has an etching characteristic different from that of the remaining layers. 4. The metal mask according to claim 2, wherein the bonding layer is a dry film-forming layer, and the hole forming layer and the support layer have different etching characteristics.

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