JP2006114427A - Vacuum vapor-deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance uniformity of film thickness distribution on a plurality of substrate faces in a vacuum vapor-deposition method in which an organic electroluminescent element is fabricated by using a mask for vapor-depositing the substrate and pixel pattern, and using a mask holder and a vapor deposition source provided with alignment mechanism in order to carry out positioning of the substrates and the masks. <P>SOLUTION: In this vacuum vapor-deposition method, a plurality number of structures composed of the substrates, the masks, and the mask holders are concentrically arranged at the upper part of the vapor deposition source, and the vapor deposition is carried out in a state that the structures consisting of the substrates, the masks, and the mask holders are inclined toward the outside from the center part of the vapor-deposition source. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an organic electroluminescence element.

  In general, an organic electroluminescence element is an organic thin film layer between a positive electrode made of a transparent conductive film (for example, indium tin oxide) and a negative electrode made of a metal (for example, Al). Layers etc. are formed, and holes injected from the anode side and electrons injected from the cathode side are recombined in the light emitting layer through the hole transport layer and the electron injection layer, respectively, An electronic device that obtains light emission.

  A vacuum deposition method is known as one method for producing the organic electroluminescence element. The vapor deposition material, which is an organic electroluminescence material, is put in a container such as a crucible, and the vapor deposition material vaporized from the crucible is heated on the substrate on which the organic electroluminescence element is formed by heating the temperature of the crucible or the like above the vaporization temperature of the vapor deposition material. Deposit to form an organic thin film layer. At this time, the film thickness is required to be uniform. However, since the pixel pattern is generally formed on the substrate using a mask, the film thickness may not be uniform depending on the mask pattern.

  As a method of making the film thickness uniform in the vacuum evaporation method, there is a method of increasing the distance between the substrate and the evaporation source, but when the distance between the substrate and the evaporation source is increased, the distance between the substrate and the evaporation source is short. Since the deposition rate of the thin film on the substrate is slower than the case, the utilization efficiency of the vapor deposition material is greatly reduced. In particular, this method is less desirable because organic electroluminescent materials are generally expensive organic compounds.

  As a method for making the film thickness uniform, there is a vapor deposition method on a lens, as known in Japanese Patent Laid-Open No. 6-192835. Conventionally, as a means for uniformly forming a thin film on a lens having a curved substrate surface, a holder for holding a plurality of lenses is rotated with respect to a vapor deposition source, and each lens is further rotated with respect to the holder. The method is used. An example of such a vacuum deposition apparatus will be described with reference to FIG.

  In the vacuum vapor deposition apparatus 21 as shown in FIG. 3, the lens holder 24 provided on the vapor deposition source 23 inside the film forming chamber 22 is an umbrella-shaped or dome-shaped lens holder centering on the vapor deposition source 23. It has a main body 24a, holds a plurality of lenses 25 at equal intervals in the outer peripheral direction of the lens holder main body 24a, and the lenses 25 are detachably held from the lens holder main body 24a. The lens holder main body 24a has a rotation shaft 26 at the center thereof, and is rotated by a motor 27 or the like.

  The vaporized material 23a evaporated from the vapor deposition source 23 by the vacuum vapor deposition device 21 having the rotation mechanism as described above is incident on the lens 25 at a uniform incident angle, and the vapor deposition material is deposited on the surface of the lens 25 with less film thickness unevenness. 23b is deposited.

  In vapor deposition on a curved surface such as a lens, a device for improving the film thickness uniformity of the thin film has been devised as described above. On the other hand, the film thickness uniformity of the organic thin film is also required in the mask vapor deposition in the production of the organic electroluminescence element. If the film thickness is not uniform, problems such as uneven light emission of the organic electroluminescence element occur. When performing mask vapor deposition on a substrate for an organic electroluminescence element, even if a pair of structures consisting of a substrate and a mask are arranged coaxially with respect to the upper part of the opening of the vapor deposition source, the organic electroluminescence material is Due to the inherent evaporation directivity, the incident amount of the evaporating material incident on the center and the edge of the mask is different, resulting in uneven film thickness on the substrate surface. Further, even when an organic electroluminescent material is deposited on the substrate without using a mask, the film thickness unevenness occurs on the substrate surface because of the influence of evaporation directivity.

  As a method for solving the above problems, a vacuum deposition method of the present invention includes a substrate, a mask for depositing a pixel pattern on the substrate, and an alignment mechanism for aligning the substrate and the mask. In a vacuum vapor deposition method for producing an organic electroluminescence element using a mask holder provided with a vapor deposition source, a plurality of structures comprising the substrate, the mask, and the mask holder are concentrically formed above the vapor deposition source. It is characterized in that vapor deposition is performed in a state where the structure including the substrate, the mask, and the mask holder is tilted outward from the central portion of the vapor deposition source.

  According to the vacuum deposition method of the present invention configured as described above, a plurality of structures including a substrate, a mask, and a mask holder provided with an alignment mechanism are arranged concentrically above the deposition source, and Since the structure composed of the substrate, the mask, and the mask holder is disposed with an inclination from the center of the deposition source toward the outside, the uniformity of the amount of the evaporated material deposited on the substrate surface through the mask is improved. . Furthermore, since it becomes possible to perform mask vapor deposition simultaneously on a plurality of substrates, the material utilization efficiency of expensive organic electroluminescent materials is improved.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a vacuum deposition apparatus used for carrying out the vacuum deposition method of the present invention.

  A vacuum vapor deposition apparatus 1 in FIG. 1 includes a vapor deposition source 3 provided inside a film formation chamber 2 and a substrate holder 4 disposed above the vapor deposition source 3. The substrate holder 4 is centered on the vapor deposition source 3. And holding a structure including a substrate 5, a mask 6, and a mask holder 7 having an alignment mechanism. The structure including the substrate 5, the mask 6, and the mask holder 7 having the alignment mechanism is detachable from the substrate holder 4, and the substrate 5, the mask 6, and the mask holder 7 having the alignment mechanism are also detachable.

  A plurality of structures including the substrate 5, the mask 6, and the mask holder 7 having the alignment mechanism are arranged concentrically on the upper part of the vapor deposition source 3, from the center of the vapor deposition source 3 toward the outside, and It is held by the substrate holder 4 with an optimum inclination according to the film thickness distribution of the vapor deposition material 3b for forming the organic electroluminescence element.

  In order to form an organic electroluminescence pixel pattern on the substrate 5, the mask holder 7 is provided with an alignment mechanism. On the substrate 5 aligned by the mask holder 7, a part of the evaporating material 3 a evaporated from the vapor deposition source 3 is deposited through the mask 6, and a pixel pattern of the organic electroluminescence element is formed on the surface of the substrate 5.

  As a vacuum exhaust system (not shown) for exhausting the inside of the film forming chamber 2, it is desirable to use a pump having a capability of exhausting quickly to a high vacuum region.

  As described above, the vacuum vapor deposition apparatus 1 includes the vapor deposition source 3 provided in the film forming chamber 2, the substrate holder 4 disposed above the vapor deposition source 3, and the substrate 5 held by the substrate holder 4. The structure is composed of a mask 6 and a mask holder 7 having an alignment mechanism. The film forming chamber 2 is evacuated by a vacuum exhaust system (not shown) to perform vacuum deposition.

  A specific example of the vacuum deposition method of the present invention will be described below using the apparatus shown in FIG.

First, in order to obtain the film thickness distribution of the vapor deposition material 3b, vapor deposition was performed on the sample substrate using the vacuum vapor deposition apparatus 1 under the following conditions. A commercially available vapor deposition source 3 is arranged in the film forming chamber 2, and tris (8-hydroxyquinolinato) aluminum (hereinafter referred to as Alq ₃ ) used as an electron transporting material and a light emitting material for an organic electroluminescence element as a vapor deposition material 3b. 5.0 g). Then, the pressure in the film forming chamber 2 and the vapor deposition source 3 was set to 1.3 × 10 ⁻⁴ Pa (1 × 10 ⁻⁶ Torr) through a vacuum exhaust system (not shown). A 200 mm × 200 mm glass substrate was used as the sample substrate. The distance h from the opening of the vapor deposition source 3 to the center of the glass substrate was set to 200 mm.

Subsequently, the vapor deposition source 3 is heated to a temperature of 280 ° C. by a heater of the vapor deposition source 3 (not shown), and Alq ₃ is sublimated at a vapor deposition rate of 2 に よ り / sec by a film thickness monitor (not shown). A 1 μm thick Alq ₃ thin film was deposited on the sample substrate. Then, a film thickness distribution as shown in FIG. 2 was obtained. In FIG. 2, X = 0 mm is a portion corresponding to the central portion of the sample substrate, and the film thickness from the central portion to the left and right 90 mm was measured. The value on the vertical axis is the film thickness ratio when the film thickness at the center of the substrate is 1. As a result, the film thickness distribution was linear in the region from X = ± 40 mm to X = ± 90 mm.

Based on the above results, the substrate holder 4 having an inclination from the region of X = ± 40 mm to X = ± 90 mm was produced, and the sample substrate (50 mm × 50 mm) was held in the region. When vacuum deposition was performed using the substrate holder 4 under the conditions of Example 1, the Alq ₃ film thickness distribution in the sample substrate was ± 2%.

  In Example 1, N, N′-diphenyl-m-tolyl-4,4′-diamine-1,1′biphenyl (hereinafter referred to as TPD) used as a hole transporting material in the organic electroluminescence device as the vapor deposition material 3b. The vacuum deposition was carried out in the same manner as in Example 1 except that 5.0 g of the mixture was charged and the deposition source 3 was heated to 240 ° C. The film thickness distribution of TPD obtained by the above experiment was linear in the region from X = ± 30 mm to X ± 80 mm. When the substrate holder 4 was produced based on the above results and vacuum deposition was performed under the conditions of Example 1, the TPD film thickness distribution in the sample substrate (50 mm × 50 mm) was ± 2%.

  In Example 1, Mg and Ag used as cathodes for the organic electroluminescence elements as the vapor deposition material 3b are filled in the independent vapor deposition sources 3, respectively, so that the concentration of Ag is 5 at% during vapor deposition. The temperature of was adjusted. The film thickness distribution of Mg: Ag obtained by the above experiment was linear in the region from X = ± 20 mm to X = ± 90 mm. Based on the above results, the substrate holder 4 was prepared and vacuum deposition was performed under the conditions of Example 1. As a result, the Mg: Ag film thickness distribution on the sample substrate (50 mm × 50 mm) became ± 2%. .

A bottom emission type organic electroluminescence element was produced based on the above Examples 1 to 3. The vacuum deposition apparatus 1 of FIG. 1 is prepared for each material, and the respective film forming chambers 2 are coupled by a transport system mechanism (not shown), and ITO (1500Å) / TPD (500Å) / Alq _{3 is} consistently vacuum-exposed without being exposed to the atmosphere. A bottom emission type organic electroluminescence device having a (500Å) / Mg: Ag (1000Å) structure was produced.

  A glass substrate (50 mm × 50 mm) having a thickness of 0.7 mm is used as the substrate 5, and ITO (indium tin oxide) is deposited on the surface of the substrate 5 by a sputtering method in advance, and the substrate is cleaned before UV. Ozone treatment was performed, and the mask 6 and the mask holder 7 were fixed.

  The substrate holder 4 that holds the structure composed of the substrate 5, the mask 6, and the mask holder 7 is manufactured based on the experimental results of Examples 1 to 3, and is disposed in the film forming chamber 2. The vapor deposition source 3 was placed on the top. Four structures including a substrate 5, a mask 6, and a mask holder 7 are arranged concentrically on the upper part of the vapor deposition source 3, and the substrate holder 4 holds the structure from the center of the vapor deposition source to the outside. The distance h from the opening of the vapor deposition source 3 to the center of the substrate holder 4 was set to 200 mm as in the above experiment.

As for the film formation conditions, a commercially available vapor deposition source is used as the vapor deposition source 3 and Alq ₃ , TPD, Mg, and Ag are used as the vapor deposition material 3b as in the case of vapor deposition of the above-described sample substrate. The internal pressure was 1.3 × 10 ⁻⁴ Pa (1 × 10 ⁻⁶ Torr). The vapor deposition source 3 is heated by a heater (not shown) and is sublimated by a film thickness monitor (not shown) so that the vapor deposition rate of each material is 2 Å / sec, and held by the substrate holder 4 in each film formation chamber 2. A thin film was deposited on the surface of the substrate 5 of the structure including the substrate 5, the mask 6, and the mask holder 7 through the mask 6.

When the bottom emission type organic electroluminescence device obtained by the above method was evaluated by applying a DC voltage in an N 2 atmosphere, light emission with little light emission unevenness was confirmed. When driven at a constant current density of about 8 mA / cm ² , light emission of 7 V, 200 cd / cm ² was confirmed in the early stage of light emission. The half life of luminance was about 3000 hours. After that, stable light emission was obtained without growth of dark spots.

10 samples obtained by the vacuum vapor deposition method of Example 4 and 10 samples obtained by the above-described method except that the conventional vacuum vapor deposition method was used were applied with a DC voltage in an N ₂ atmosphere to emit light. A comparative evaluation of unevenness was performed. Judgment of light emission unevenness was visual, and the evaluation was shown in three stages. The results are shown in Tables 1 and 2. Table 2 shows the evaluation results of the bottom emission type organic electroluminescence device produced by the conventional vapor deposition method under the same conditions as described above.

○: Light emission is not uneven △: Light emission unevenness is slightly observed ×: Light emission unevenness is observed

表１及び表２からわかるように、従来の真空蒸着方法に比べて、本発明の真空蒸着方法を用いることにより発光むらの少ない素子を得る事ができている。

As can be seen from Tables 1 and 2, by using the vacuum deposition method of the present invention as compared with the conventional vacuum deposition method, it is possible to obtain an element with less uneven emission.

Of course, the vapor deposition material used in the present invention is not limited to Alq ₃ , TPD, Mg, and Ag described above, and any vapor deposition material may be used as long as it is used for forming an organic electroluminescence element. Further, the vapor deposition source is not limited to a commercially available one.

An example of an embodiment of the present invention is shown. _{2 is} a film thickness distribution of Alq ₃ obtained in Example 1. An example of a conventional example is shown, and (a) is a view of the substrate holder as viewed from the vapor deposition source side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum evaporation apparatus 2 Deposition chamber 3 Deposition source 3a Evaporation substance 3b Evaporation material 4 Substrate holder 5 Substrate 6 Mask 7 Mask holder 21 Vacuum deposition apparatus 22 Deposition chamber 23 Deposition source 23a Evaporation substance 23b Evaporation material 24 Lens holder 25 Lens 26 Rotating shaft 27 Motor

Claims (2)

  An organic electroluminescence element is formed using a substrate, a mask for depositing a pixel pattern on the substrate, a mask holder having an alignment mechanism for aligning the substrate and the mask, and a deposition source. In the vacuum deposition method to be fabricated, a structure comprising a plurality of concentrically arranged structures composed of the substrate, the mask, and the mask holder, and a structure composed of the substrate, the mask, and the mask holder. A vacuum vapor deposition method comprising performing vapor deposition in a state where the body is inclined toward the outside from the center of the vapor deposition source.   2. The vacuum deposition method according to claim 1, wherein the deposition is performed by changing an inclination angle of a structure including the substrate, the mask, and the mask holder for each deposition material for forming an organic electroluminescence element.

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