JP2001210468A - Film forming method of organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film forming method for an organic EL element by which plural kinds of organic EL films having different luminous colors are selectively coated by simple method. SOLUTION: This method is to form a plural kinds of organic EL layers of different materials (preferably emitting red, green and blue lights) by coating selectively into a stripe-shaped pattern on a substrate of the organic EL element. Barrier ribs 43 partitioned regions 44 on which respective patterns are formed are formed on a substrate 41, while the substrate is kept aslant into longitudinal direction of the regions 44. Solutions 6R, 6G, 6B, dissolving materials for forming the organic EL films emitting red, green and blue lights, are prepared and these solutions 6R, 6G, 6B are respectively supplied at the upper end of the corresponding regions 44 and the solutions 6A, 6G, 6B flow down by dint of gravity and fill the regions 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an organic EL film in an organic electroluminescence (EL) device, and more particularly, to a method of applying an organic EL film in stripes.

[0002]

2. Description of the Related Art An organic EL device is an organic EL device having a light emitting layer.
It has a configuration in which the L film is sandwiched between an anode and a cathode. Since various luminescent colors can be obtained depending on the material used for the luminescent layer, multi-color display can be performed by separately applying organic EL films having different luminescent colors in a predetermined pattern. Further, full-color display is possible by repeatedly arranging three types of organic EL films each emitting red, green and blue light as a set. 2. Description of the Related Art Conventionally, a vacuum deposition method and an ink-jet method have been known as methods for separately applying a plurality of types of organic EL films into fine patterns.

[0003]

However, since only one kind of material can be deposited at a time by the vacuum deposition method, for example, in order to form a light emitting layer of three colors, three deposition steps are performed for each material. . Further, in each vapor deposition step, it is necessary to adjust a mask having a fine window opened in accordance with the formation pattern of each color to a predetermined position, and a process such as alignment between the substrate and the mask is complicated.

On the other hand, the ink jet method is a method in which a solution of a material for an organic EL film is sprayed in place of ink used for ordinary printing or the like (Japanese Patent Laid-Open No. 10-153967). In this method, since the pattern of the organic EL film is drawn by moving the nozzle with respect to the substrate, it is necessary to precisely control and move the nozzle and / or the substrate when applying. In addition, since fine (micro-milliliter) droplets are sprayed and applied, there is a problem that uniform film formation is not easy and pinholes are easily generated. If a pinhole is present in the light emitting layer or the like, there is a possibility that a local short circuit occurs in the obtained organic EL element, causing a problem such as generation of a non-light emitting portion.

An object of the present invention is to provide a method for forming a film of an organic EL element in which a plurality of types of organic EL films having different emission colors are separately applied by a simple method.

[0006]

According to a first aspect of the present invention, there is provided a method for forming a film of an organic EL device, in which a plurality of types of organic EL films of different materials are separately applied on a substrate of the organic EL device in a stripe pattern. The method, wherein the substrate on which the partition walls for partitioning the pattern formation region are formed is held at an angle to the longitudinal direction of the region, and the material for the organic EL film formed in each region is The method is characterized in that a plurality of dissolved solutions are supplied from the upper end of the corresponding region, and the solution is caused to flow down by gravity by flowing down the solution by gravity.

It is preferable that an electrode having a stripe pattern crossing the pattern of the organic EL film is formed on the substrate in advance. Further, it is preferable that the material dissolved in the plurality of types of solutions is a material for an organic EL film that emits red, green, and blue light, respectively. Thus, an organic EL element suitable for full-color display can be obtained.

As the above-mentioned "substrate", a substrate having a degree of transparency that does not impair the recognition of characters, figures and the like by light emission of the organic EL film can be used. Also, organic EL
As a member of the element, it is preferable that the member has a strength enough to hold the shape and has such a hardness that the surface is not easily damaged. Examples of such a material include polyethylene terephthalate, polyethersulfone, and polycarbonate in addition to glass. This transparent material may be colorless and transparent, or may be a colored and transparent material colored in an appropriate color tone.

An "organic EL laminated film" is formed by laminating an anode, an organic EL film and a cathode on this substrate. The organic EL film disposed between both electrodes includes at least a light emitting layer,
It may have a hole transport layer and / or an electron transport layer in addition to this light emitting layer, and may further have a hole injection layer and / or an electron injection layer. Materials constituting the anode and the cathode include:
Various known materials can be used for each. The formation method is a vacuum deposition method, a spin coating method, a casting method,
What is necessary is just to select suitably from methods, such as a sputtering method and LB method.

In the present invention, a plurality of types of organic EL films made of different materials are separately formed in a stripe pattern. The width and length of each pattern constituting the stripe, the number of patterns, and the like are not particularly limited. The shapes of the patterns may be the same or different, but it is preferable that the patterns on which the same type of organic EL film is formed have the same shape. It is preferable that the pattern of the organic EL film is provided so as to intersect with the pattern of the striped electrodes formed on the substrate in advance. The angle between the pattern of the organic EL film and the pattern of the electrode is 60 ° to 9 °.
It is preferably 0 °, and more preferably both patterns are orthogonal.

[0011] These plural kinds of organic EL films form partition walls on the substrate for partitioning the pattern formation region, and hold the substrate at an angle to the longitudinal direction of the pattern formation region (the direction in which each pattern extends). Then, a solution of the material for the organic EL film is supplied from the upper end of the pattern forming region, and the solution is applied by gravity to apply the solution in the pattern forming region. Then, the solvent is removed from the solution to form the organic EL film. Each of the pattern formation areas has a corresponding organic E
A solution in which a material for forming the L film is dissolved is supplied. The solvent used for this solution is not particularly limited as long as it can dissolve the material for the organic EL film. However, a solvent that does not damage the electrodes and the partition walls and can be easily removed at normal temperature and pressure is preferable. For example, 1,3-dichloropropane, chloroform, toluene and the like can be used.

The plurality of types of organic EL films are preferably organic EL films having different emission colors, more preferably organic EL films emitting red, green and blue light, respectively. A material for an organic EL film that emits light of each color, that is, a light emitting material for obtaining each light emitting color, a hole and / or electron transport layer material and a hole and / or injection layer for efficiently emitting these light emitting materials. As a material (a different material may be used depending on a light emitting material or a common material), various known materials may be used. The following are typical examples of the light emitting material. Yellow light emission: Doping rubrene with an aluminum quinolium complex as a host. Green light emission: Doping quinacridone using an aluminum quinolium complex as a host. Red light emission: DCM using aluminum quinolium complex as host
1 [4-dicyanomethylene-6- (p-dimethylaminostyryl) -2-methyl-4H-pyran] is doped.

The material and method of forming the partition are not particularly limited as long as the transparent electrode formed on the substrate is not damaged. For example, it can be manufactured by a known patterning process using a general photoresist material or the like. The thickness of the partition is not particularly limited, but may be, for example, about 10 to 300 μm. The angle at which the substrate is inclined depends on the shape of the pattern and the organic E to be formed.
The thickness varies depending on the thickness of the L film, the viscosity of the supplied solution, the solid content concentration, and the like.
Is more preferable, and more preferably -45 ° to +45.
°, and more preferably -30 ° to + 30 °. The inclination angle from the vertical direction to the direction in which the surface on which the organic EL film is formed is upward is represented by +, and the inclination angle to the direction in which this surface is downward is represented by-.

The thickness of the organic EL film formed by the method of the present invention is not particularly limited. For example, an organic EL film having a thickness of about 50 to 1000 ° (preferably about 100 to 500 °).
A film can be made. Methods for adjusting the thickness of the organic EL film include the viscosity and solid concentration of the solution used, the inclination angle of the substrate, and the like. In addition, the viscosity of the solution is usually preferably 500 mPa · s (cp) / 25 ° C. or less, more preferably in the range of 1 to 200 mPa · s / 25 ° C. If the viscosity of the solution is too high, it is difficult to use gravity to spread the solution to the pattern formation region. In addition, the solid content concentration of the solution is usually preferably 30% by weight or less, more preferably 0.1 to 15% by weight. If the solid concentration is too high, the viscosity of the solution tends to be excessively high, and it is difficult to control the film thickness. The supply speed of the solution is not particularly limited, but is preferably a speed at which the solution does not overflow beyond the partition walls and a speed at which the solution is supplied as a continuous flow.

After the organic EL film is formed on the substrate in this way, electrodes are formed on the organic EL film, and if necessary, the light emitting layer and the electrodes constituting the organic EL laminated film are further removed with water or oxygen. (Hereinafter, also referred to as “moisture or the like”).
An L element can be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to experimental examples. (Experimental example 1) Experimental example 1 is a reference example performed for examining the accuracy of a film obtained by the film forming method of the present invention. As shown in FIG. 2, a substrate 11 made of a 10 cm × 10 cm glass plate was held at an angle θ from a vertical direction. On the film forming surface 115 of the substrate 11, an ITO film 1 having a thickness of 1800 mm and a width of 1 mm extending in parallel with this side at a position 3 cm from the upper side of the inclined substrate 11.
2, two Kapton adhesive tapes 13 each having a width of 2 mm, which are orthogonal to the ITO film 12, are attached to each other in parallel at an interval of 1 mm ("Kapton").
Is a product name of an adhesive tape manufactured by Dupont Toray. ).
Thus, a pattern forming region 14 having a width of 1 mm is formed between the two adhesive tapes 13. In addition, the adhesive tape 1
The thickness of 3 is 200 as the total thickness of the pressure-sensitive adhesive layer and the base material.
μm.

On the other hand, 5 g of polyvinyl carbazole (PVK) was dissolved in 1 liter of 1,3-dichloropropane to prepare a PVK solution. The viscosity of this PVK solution was 20 mPa · s / 25 ° C. This PVK solution is taken in a syringe, and the angle θ for holding the substrate 11 is + 10 °
And + 20 °, and the angle between the needle of the syringe and the substrate 11 is 90 °.
From 41, the PVK solution was continuously supplied. The PVK solution quickly flowed down the area 14 without reaching the lower end 142 without overflowing from the pattern formation area 14. After that, while keeping the substrate 11 at the same angle θ, the PVK solution was dried at room temperature to obtain a PVK film. The adhesive tape 13 was peeled off from the substrate 11, and the uniformity of the obtained PVK film was evaluated by the following method.

(1) Uniformity of Film in Casting Direction At a position 0 cm (upper end), 5 cm and 10 cm (lower end) in the casting direction of the PVK solution from the upper end 141 of the pattern forming region 14, use a pointed metal rod. The PVK film is scraped off, and the level difference between the substrate 11 and the PVK film at the site is measured with a level difference meter (trade name “Dektak” manufactured by Sloan Company).
The uniformity of the film thickness was evaluated by measuring the above. Table 1 shows the results. As can be seen from Table 1, there is no large difference in the film thickness in the casting direction, and a PVK solution supplied from one end of the pattern formation region can form a PVK film having a uniform thickness over the entire region. Was. Further, it was found that when the angle θ at which the substrate was inclined with respect to the vertical direction was increased, the formed PVK film became thicker, and the thickness of the PVK film could be controlled by adjusting the angle θ.

[0019]

[Table 1]

(2) Film uniformity near the ITO film As shown in FIG. 3, the PVK formed on the ITO film 12
Step between the membrane 2 (position indicated by arrow a in FIG. 3) and the PVK membrane 2 on the upstream side (position of arrow b) and downstream side (position of arrow c) of the ITO film 12 with respect to the casting direction. Was measured with the above-mentioned step meter. As a result, the step between the upper side of the ITO film 12 and the upstream side was 1852 °, and the step between the upper side of the ITO film 12 and the downstream side was 1830 °. 18 of these
Since 00Å is a step derived from the thickness of the ITO film 12, the presence of the ITO film 12 formed on the
It can be seen that the effect on the thickness uniformity of the VK film 2 is small.

(Experimental Example 2) In Experimental Example 2, an organic EL film was formed by a film forming method of the present invention using a film forming machine.
The light emitting state of the obtained organic EL film was examined. As shown in FIG. 1, the film forming machine 5 includes containers 51R, 51G, and 5B containing red, blue, and green luminescent material solutions 6R, 6G, and 6B, respectively.
1B. The pressure of a gas (nitrogen) cylinder 53 can be applied to each of the containers 51R, 51G, and 51B via a pressure regulator 52, whereby the luminescent material solutions 6R, 6G,
6B is a supply line 55 having a stopper 54 corresponding to each color.
Nozzle 5 corresponding to each color through R, 55G, 55B
Discharged from 6R, 56G, 56B respectively. As shown in FIG. 4, the nozzles 56R, 56G, and 56B are arranged in a line at the same height and direction, and are regularly and repeatedly arranged in this order.

The above-mentioned luminescent material solutions 6R, 6G, and 6B are obtained by dissolving 5 g of PVK in 1 liter of chloroform and further adding Nile Red as a material for emitting red light, Coumarin 540 as a material for emitting green light, or a material for emitting blue light. Respectively as tetraphenylcyclobutadiene.
It was adjusted by dissolving 01 g. The viscosity of each solution was 15 to 20 mPa · s / 25 ° C. On the other hand, 150
1 mm thick ITO film (10Ω / □)
A substrate 41 made of a glass plate of 00 mm × 100 mm is prepared. As shown in FIG. 5, the width of the ITO film line 42 extending parallel to one piece of the substrate 41 is 100 μm, and the gap between the ITO film lines 42 is 30 μm. Was patterned. After ultrasonic cleaning the substrate 41 with a solvent and distilled water, a photoresist is applied to a thickness of 100 μm, and the width of a resist line (partition) 43 extending perpendicular to the ITO film line 42 is 30 μm, and each resist line 43 The width of the pattern formation region 44 formed between the two is 100 μm.
It patterned so that it might become.

After the substrate 41 is washed and dried, the surface on which the organic EL film is to be formed is further washed by an ozone (UV / O ₃ ) washing machine. The camera was mounted so as to have a height difference in the direction and inclined at an angle θ from the vertical direction. A position 5 mm from the upper end of the substrate 41 was set as the upper end 441 of the pattern formation region 44, and the nozzles 56R, 56G, and 56B were set close to the position up to a distance of 100 μm from the resist line 43. The pressure regulator 5 was adjusted so that the nitrogen gas pressure applied to the solutions 6R, 6G, and 6B was 1.1 kg / cm ^2.
2 was adjusted, and each stopper 54 was opened. At this time, the nozzle 5
The directions of 6R, 56G, 56B (the spraying directions of the solutions 6R, 6G, 6B) are horizontal, the angle θ of the substrate 41 is + 20 °,
0 ° and −20 °. Three seconds after the start of the spraying, the solutions 6R, 6G, and 6B started dripping from the lower end of the substrate 41, so that the stopper 54 was closed to end the discharge. After holding for 2 minutes, the substrate 41 was removed from the film forming machine 5. At this time, there was no odor of chloroform and the substrate 41 was dry. The substrate 41 was placed in a 95 ° C. constant temperature bath and dried for 1 hour to obtain a striped organic EL film having a line pattern emitting red, blue, and green light, respectively.

The substrate on which the organic EL film was formed by the above process was inserted into a vacuum evaporation apparatus, and an aluminum quinolium complex was evaporated to form an electron transport layer having a thickness of 20 nm. further,
A back electrode (cathode) having a thickness of 100 nm was formed by depositing an Mg-Ag alloy. Thereafter, current was applied to the transparent electrode and the back electrode, and the state of light emission was confirmed.

In this experimental example, the angle θ of the substrate is set to −20 °.
The light emission state of the organic EL film formed as the best is the best, and when observed by an optical microscope in the energized state, all the light emitting portions in the substrate emit light, and the light emission of the color tone corresponding to each pattern can be confirmed. Was. On the other hand, if the angle θ is 0
In the case of °, a point or a pattern where no light was emitted was observed in some places, and it is considered that a short circuit or coating abnormality occurred in any part of the pattern. Angle θ is +2
When the angle was set to 0 °, the number of points or patterns that did not emit light was larger than in the case of θ = 0 °, and portions emitting light of a color different from the intended light emission color were recognized. This is considered to be because the viscosity of the solution in this experimental example is relatively low, and if the substrate is tilted too much in the + direction, the solution supplied to each pattern formation region overflows beyond the partition.

(Experimental Example 3) An organic EL film was formed in the same manner as in Experimental Example 2 except that the amount of PVK dissolved in 1 liter of chloroform was 8 g, and the light emission state was examined. The viscosity of each solution used in Experimental Example 3 was 20 to 30 mPa ·
s / 25 ° C. In this experimental example, the angle θ of the substrate was set to 0.
Organic E formed in ° (by placing the substrate vertically)
The L film has the best light emitting state, followed by −20 ° and +
The order was 20 °. Further, since the viscosity of the solution was higher than that of Experimental Example 2, the organic EL film formed at θ = −20 ° was thicker than that of Experimental Example 2, and the driving voltage was higher.

In the first to third experimental examples, the film-forming state is adjusted by changing the inclination angle θ of the substrate or the viscosity of the solution. In addition, the film-forming state is also controlled by the discharge direction of the nozzle and the discharge pressure. You can control.

[0028]

According to the film forming method of the present invention, the solution supplied to the upper end of the pattern forming region is made to flow in the region by flowing down by gravity. As described above, since the solution is applied in the region by flowing the solution by its own weight, it is not necessary to move the position of the nozzle and / or the substrate, and the control is easy. Further, there is an advantage that the apparatus is simpler than the method by vapor deposition, and a plurality of types of organic EL films can be manufactured in one process. Further, the stopper can be closed when the solution reaches the lower end of the substrate as in Experimental Example 2, and the organic EL film is formed because it is not deposited on unnecessary parts such as on a mask. Useless consumption of materials can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a film forming machine used in Experimental Examples 2 and 3.

FIG. 2 is a perspective view showing a film forming method of Experimental Example 1.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a perspective view showing a discharge unit of a film forming machine used in Experimental Examples 2 and 3.

FIG. 5 is a plan view showing a substrate used in Experimental Examples 2 and 3.

[Explanation of symbols]

 41; substrate 42; ITO film line (transparent electrode) 43; resist line (partition wall) 44; pattern formation region 441; upper end 5; , 6B; solution

Claims (3)

[Claims] 1. A method for forming a plurality of types of organic EL films of different materials on a substrate of an organic EL element by separately applying the same in a striped pattern, wherein a partition for partitioning a pattern formation region is formed. Holding the substrate inclined with respect to the longitudinal direction of the region,
A plurality of types of solutions in which the material for the organic EL film formed in each of the regions is dissolved are supplied from the upper end of each of the corresponding regions, and the solutions are allowed to flow down by gravity to spread throughout the regions. A method for forming a film of an organic EL device, comprising: 2. The method for forming a film of an organic EL device according to claim 1, wherein an electrode having a stripe pattern crossing the pattern of the organic EL film is formed on the substrate in advance. 3. The material dissolved in the plurality of types of solution,
3. The method for forming a film of an organic EL device according to claim 1, wherein the material is a material for an organic EL film that emits red, green, and blue light.