Recent years have witnessed practical use of a flat-panel display in various products and fields. This has led to a demand for a flat-panel display that is larger in size, achieves higher image quality, and consumes less power.
Under such circumstances, great attention has been drawn to an organic EL display device that (i) includes an organic electroluminescent (hereinafter abbreviated to “EL”) element which uses electroluminescence of an organic material and that (ii) is an all-solid-state flat-panel display which is excellent in, for example, low-voltage driving, high-speed response, and self-emitting.
An organic EL display device includes, for example, (i) a substrate made up of members such as a glass substrate and TFTs (thin film transistors) provided to the glass substrate and (ii) organic EL elements provided on the substrate and connected to the TFTs.
An organic EL element is a light-emitting element capable of high-luminance light emission based on low-voltage direct-current driving, and includes in its structure a first electrode, an organic EL layer, and a second electrode stacked on top of one another in that order, the first electrode being connected to a TFT. The organic EL layer between the first electrode and the second electrode is an organic layer including a stack of layers such as a hole injection layer, a hole transfer layer, an electron blocking layer, a luminescent layer, a hole blocking layer, an electron transfer layer, and an electron injection layer.
A full-color organic EL display device typically includes, aligned on a substrate as sub-pixels, organic EL elements including respective luminescent layers of red (R), green (G), and blue (B). Such a full-color organic EL display device carries out a color image display by, with use of TFTs, selectively causing the organic EL elements to each emit light with a desired luminance.
Producing an organic EL display device requires forming luminescent layers for respective organic EL elements, the luminescent layers each (i) being made of an organic luminescent material that emits light of a color and (ii) having a predetermined pattern. Further, for a layer requiring no patterns to be formed for individual organic EL elements, the above production uniformly forms a thin film entirely over a pixel region made up of organic EL elements.
The formation of a luminescent layer in a predetermined pattern is known to be carried out by a method such as a vacuum vapor deposition method, an inkjet method, and a laser transfer method. A low-molecular organic EL display (OLED), for example, is frequently produced by a vacuum deposition method.
The vacuum deposition method uses a mask (also called “shadow mask”) having an aperture in a predetermined pattern. The vacuum deposition method causes a vapor-deposited surface of a substrate to which the mask is fixed in close contact therewith to face a vapor deposition source, and then causes vapor deposition particles (film formation material) from the vapor deposition source to be deposited onto the vapor-deposited surface through the aperture of the mask. This forms a thin film in a predetermined pattern. The above vapor deposition is carried out for each color of the luminescent layers (this technique is referred to as “selective vapor deposition”).
Patent Literatures 1 and 2, for example, each disclose a method for carrying out selective vapor deposition for luminescent layers of respective colors by sequentially moving a mask relative to a substrate. Such a method uses a mask equivalent in size to the substrate, and fixes the mask during vapor deposition at such a position that the mask covers a vapor-deposited surface of the substrate.