JP2001110567A - Manufacturing procedure for organic field light emitting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing process to form electrodes which have resistance as low as possible, in a process for patterning to the 2nd electrode with use of a shadow mask. SOLUTION: An organic field light emitting apparatus formed with the 2nd electrode having low resistance, can be manufactured. Lowering of thickness of the 2nd electrode at under part of reinforcing wire, can become possible by making the hole opening ratio of the mesh type reinforcing wire to less than 60%, and wire width of it to under 40 micrometer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an organic electroluminescent device that can be used in fields such as display elements, flat panel displays, backlights, and interiors.

[0002]

2. Description of the Related Art An organic electroluminescent device emits light when holes injected from an anode and electrons injected from a cathode recombine in an organic light emitting layer sandwiched between both electrodes.
A typical structure is a transparent first electrode (anode), hole transport layer, organic light emitting layer, and second electrode (cathode) on a glass substrate.
The light emission generated by the driving is extracted to the outside through the first electrode and the glass substrate. Such an organic electroluminescent device is capable of emitting thin, high-luminance light under low-voltage driving and multicolor light emission by selecting an organic light-emitting material, and has been actively developed for application to light-emitting devices and displays. is there.

In a method of manufacturing an organic electroluminescent device, it is necessary to form an organic light-emitting layer and a second electrode by patterning, and various methods of manufacturing have been studied.

When fine patterning is required, a photolithography method is often used as a typical method, but a wet process accompanying the photolithography may be a problem. Therefore, when a thin film is formed by a dry process such as a vacuum deposition method, a sputtering method, or a chemical vapor deposition method (CVD), a shadow mask is arranged in front of the substrate, and a thin film is formed in the opening. The patterning by the method is often desirable from the viewpoint of the number of steps, the chemical solution used, contamination of the thin film by impurities, and the like.

[0005]

In order to realize fine patterning by the mask method, the pattern of the shadow mask is inevitably fine, so that the shape of the opening is deformed and the pattern processing accuracy is deteriorated. was there.
In particular, for striped electrodes used in displays, etc., it is necessary that the electrodes have sufficiently low resistance in the length direction of the elongated electrodes and that the electrodes adjacent in the width direction are completely insulated. However, in the corresponding shadow mask, the mask portion sandwiched between the stripe-shaped openings becomes elongated like a thread, and deformation due to bending or the like becomes severe, so that fine patterning by the mask method was practically impossible. . As a method of solving such a problem and achieving fine patterning with good accuracy by a mask method, a method of forming a mesh reinforcing line on one surface of a mask portion is known. When a second electrode is patterned using a shadow mask having such a reinforcing line, there is a gap between the mask portion and the reinforcing line,
Since the second electrode material extends around the lower part of the reinforcing wire and is deposited, it is possible to form the elongated continuous strip-shaped second electrode. However, a reduction in the adhesion rate of the second electrode material to the substrate is inevitable due to the presence of the reinforcing wire, and there is a limit in reducing the resistance value of the electrode due to the restriction of the patterning method.

[0006]

SUMMARY OF THE INVENTION The present invention provides a thin film layer including a first electrode formed on a substrate, a light emitting layer formed of at least an organic compound formed on the first electrode, and a thin film layer formed on the thin film layer. A method of manufacturing an organic electroluminescent device including a second electrode and at least one opening in a mask portion, and a mesh-like reinforcement having an opening ratio of 60% or more on one surface of the mask portion. A shadow mask having a line, in a state where the other surface of the mask portion is arranged facing the substrate, by depositing the second electrode material flying from the reinforcing line side on the thin film layer through the opening. And a method of manufacturing an organic electroluminescent device, comprising patterning a second electrode.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The organic electroluminescent device of the present invention has a first electrode, a thin film layer including at least a light emitting layer made of an organic compound, and a second electrode on a substrate. The present invention relates to a shadow mask used when patterning an electrode.

FIGS. 1 and 2 show an example of a shadow mask having a mesh reinforcing line used for patterning the second electrode. One surface 35 of the mask portion 31 and the reinforcing wire 33
And the entire mask is fixed to the frame 34. The thickness of the mask part is
Thickness is not particularly limited because the gap existing between one surface of the mask portion and the reinforcing line is widened and the amount of wraparound of the vapor deposition material is increased, but the shadow is thicker than the width of the mask portion. Since it is difficult to manufacture a mask with high accuracy, the thickness of the mask portion is preferably equal to or more than the minimum width of the mask portion and approximately three times or less. For example, if the width of the stripe-shaped opening 32 serving as the second electrode is 250 μm and the pitch is 300 μm, the width of the mask portion is 50 μm and the thickness of the mask portion is 5 μm.
It is about 0 to 150 μm.

The mesh reinforcing wire shown in FIG. 1 has a hexagonal shape, but is not limited thereto.
The shape may be a triangle, a quadrangle, another polygon, or a mixture of them. Further, the cross section of the mask portion may be tapered, and the cross section of the reinforcing wire may be uneven. To prevent the mask portion from damaging the substrate or the thin film layer already formed on the substrate when the shadow mask comes into contact with the substrate, a cushion layer exists on the surface of the mask portion on the side where the reinforcing line does not exist. May be.

The shape and material of the cushion layer are not particularly limited, and may be integrated with the mask portion. However, from the viewpoint of preventing scratches, the cushion layer is preferably formed of a relatively soft substance such as a resin. As a countermeasure for preventing scratches, there is a method of forming a portion that acts as a spacer at least partially having a height exceeding the thickness of the thin film layer on a substrate and using the portion, and this method can also be adopted.

The mesh reinforcing line is formed on the mask portion, and preferably has an aperture ratio of 60% or more.
65% or more, more preferably 70% or more. Here, the aperture ratio is defined as a ratio of the area occupied by the openings of the mesh reinforcing lines per unit area, that is, a value excluding the ratio of the area occupied by the reinforcing lines per unit area from 1. When the mesh reinforcing line has a repeating pattern, the ratio of the area occupied by the opening per unit can be geometrically calculated. For example, if the reinforcing wire is pitch 1
mm square grid mesh with a line width of 0.2 m
m, the aperture ratio is (1-0.2) × (1-
0.2) /1×1=0.64, or 64%.

In order to increase the aperture ratio of the mesh reinforcing wire, there are a method of making the mesh coarser and a method of narrowing the line width of the mesh. In order to maintain the reinforcing effect as high as possible, it is preferable that the mesh is fine. In order to maintain the finest possible mesh and achieve the purpose of increasing the aperture ratio to 60% or more, it is preferable to reduce the width of the reinforcing wire. In the present invention, the thickness is preferably less than 40 μm.

In the method of manufacturing an organic electroluminescent device according to the present invention, the second electrode material is separated from the reinforcing wire side because the second electrode material flies from the reinforcing wire side and wraps around and is deposited on the shadow of the reinforcing wire. Reinforced line is 40
In the case of less than μm, the adhesion rate of the second electrode material to the portion corresponding to the lower part of the reinforcing wire is stable, and as a result, the thickness of the formed second electrode becomes more uniform, and the entire electrode caused by the electrode thickness is reduced. Fluctuations in the resistance value can be suppressed smaller.
Further, in the plurality of second electrodes, a difference in the number of thin portions of the electrode corresponding to a portion corresponding to a lower portion of the reinforcing wire is less likely to cause a problem such as variation in resistance value of each of the electrodes. Therefore, the line width of the reinforcing wire is preferably less than 40 μm, and more preferably less than 35 μm, in order to minimize the influence of the portions having different electrode material adhesion rates as much as possible. Since the opening ratio of the reinforcing line is improved by reducing the line width of the reinforcing line, an opening ratio of 60% or more can be realized.

Suitable materials for the mask include, but are not particularly limited to, metallic materials such as stainless steel, copper alloy, iron-nickel alloy, and aluminum alloy, and various resin materials. When the strength is not sufficient because the pattern is fine and the adhesion to the substrate of the organic electroluminescent device needs to be improved by magnetic force, a magnetic material may be used as a mask material. Preferable examples include hardened hardening magnet materials such as pure iron, carbon steel, W steel, Cr steel, Co steel, and KS steel, MK steel, Alnico steel, NKS steel, and Cuni steel.
precipitation hardening magnet material such as co steel, OP ferrite, Ba
Sintered magnet materials such as ferrite, metal core materials such as Sm-Co and Nd-Fe-B alloys (Permalloy), ferrite core materials such as Mn-Zn, Ni-Zn and Cu-Zn, carbonyl Iron, Mo permalloy,
A dust core material obtained by compression-molding a fine powder such as sendust together with a binder is exemplified. It is desirable to manufacture a mask from a material obtained by molding these magnetic materials into a thin plate shape, but a material obtained by mixing a magnetic material powder into rubber or resin and molding the film into a film shape can also be used.

The material for the reinforcing wire may be the same as or different from the mask material. In order to facilitate the microfabrication, a photosensitive resin such as an acrylic resin or a polyimide resin can be used. However, the resin may be selected as needed and is not particularly limited.

The thinner the reinforcing line, the easier the wraparound of the deposited material, but it may be difficult to manufacture a mask having a thin reinforcing line from the beginning. In such a case, a mask having a relatively thick reinforcing line may be prepared, and then the line may be thinned by an appropriate method. In the process, thinning by etching is easy, and the mask portion may be etched simultaneously with the reinforcing line. The thinning method is not particularly limited, and an appropriate means may be used depending on the material of the reinforcing wire. Alternatively, a photosensitive resin sheet such as a film resist is attached to one surface of the mask portion, and the photosensitive resin sheet is patterned by a photolithography method, whereby a reinforcing line can be formed or thinned.

The method of manufacturing the shadow mask of the present invention is not particularly limited, but a method of separately forming the mask portion and the reinforcing wire and connecting the reinforcing wire to one surface of the mask portion is easy in process. . When the reinforcing wire has a mesh structure, the mask portion and the reinforcing wire can be overlapped and connected at one time.

As a method for connecting the mask portion and the reinforcing wire, an adhesive or a pressure-sensitive adhesive can be used, or pressure bonding or welding can be used. In the case of a resin material, heat compression bonding or fusion can be used. In the case where is a conductive material like a metal-based material, it is preferable to use the electrodeposition phenomenon from the viewpoint of processing accuracy. That is, the mask portion and the reinforcing wire are immersed in an electrolytic solution in contact with each other, and an electrodeposit is deposited on the contact portion by energization to connect the two. Generally, a metal material typified by Ni is selected for the electrodeposit, but an organic material such as polyaniline can also be used.

Examples of the method of forming the mask portion include an etching method, mechanical polishing, a sand blast method, a sintering method, a laser processing method, use of a photosensitive resin, and the like. It is preferable to use an electroforming method that can relatively easily form a thick film. The same can be said for the method of forming the reinforcing wire, but the forming method is not particularly limited, and an optimum method may be selected as needed.

In a preferred organic electroluminescent device of the present invention, a thin film layer including at least a light emitting layer made of an organic compound is formed on a plurality of transparent first electrodes patterned in a stripe shape formed on a transparent substrate. And a second electrode patterned thereon in a stripe pattern crossing the first electrode. The second electrode is characterized in that it is patterned in stripes, and the width of the second electrode is not more than 500 μm. The intersection between the first electrode and the second electrode patterned in a stripe form one luminescent pixel. In a full-color display, three light-emitting pixels of red, green, and blue become one display pixel. The width of the second electrode is related to the size of these luminescent pixels, and is preferably 500 μm or less for performing high-definition display. Another factor that determines the pixel size is the width of the first electrode,
This is usually smaller than the width of the second electrode.

The organic electroluminescent device of the present invention is manufactured by the following steps, but is not limited thereto. The substrate is selected from a transparent material, but a glass substrate is usually used, and a transparent electrode film made of indium tin oxide (ITO) is often patterned thereon to form a first electrode. In some cases, an insulating layer covering a part of the first electrode is formed on the substrate on which the first electrode is formed, and in some cases, a spacer having at least a part having a height exceeding the thickness of the thin film layer is formed. Next, a thin film layer including a light emitting layer is formed on the first electrode. The structure of the thin film layer includes 1) a hole transport layer / a light emitting layer, and 2) a hole transport layer /
A light-emitting layer / electron transport layer, 3) a light-emitting layer / electron transport layer, and a light-emitting layer in which 4 or more layer constituent materials are mixed in a single layer are conceivable. Known materials are used for the organic layers such as the hole transport layer, the light emitting layer, and the electron transport layer. Various evaporation methods using a shadow mask can be applied to pattern formation of these thin film layers. Thereafter, the second electrode material is deposited by using a shadow mask having an opening ratio of the reinforcing wire of 60% or more according to the present invention to form a stripe-shaped second electrode, whereby an intended organic electroluminescent device can be obtained. . Further, after formation of the second electrode, formation of a protective film or sealing may be performed by a known technique.

[0022]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A shadow mask for patterning the second electrode was prepared as follows. First, an outer shape 120 × 8 as a mask part
A Ni—Co alloy sheet having a thickness of 4 mm and a thickness of 100 μm was provided with a striped opening. The stripe-shaped opening has a length of 100 mm and a width of 250 μm, and has a pitch of 3
200 pieces are arranged in the width direction at 00 μm. This mask portion was formed by depositing a Ni-Co alloy on an electroformed master by electroforming. Next, a mesh structure composed of regular hexagons was formed as a reinforcing wire. The reinforcing wire is also formed by using the electroforming method, and the material is Ni. Before the mask portion was removed from the electroformed mold, the reinforcing wire was overlaid on the mask portion, and the two were connected by electrodeposition of Ni. This was removed from the electroformed mold, fixed to a 4 mm-wide stainless steel frame having the same outer shape as the mask portion using an adhesive, and an extra reinforcing wire protruding from the frame was cut. During the period from connection with the mask portion to fixing to the frame, tension was applied to the reinforcing wire, and care was taken not to impair the flatness of the shadow mask. In addition, the surface of the shadow mask having the reinforcing line was bonded to the frame. There is a gap of 100 μm between the substrate contact surface of the shadow mask and the reinforcing line. The line width of the reinforcing wire is 36 μm, and the interval between the reinforcing lines on two sides facing each other in the regular hexagon is 200 μm. The opening ratio of this mesh-like reinforcing wire calculated and calculated geometrically was 63%.

The organic electroluminescent device was manufactured as follows. An ITO glass substrate (manufactured by Geomatic) having a 130 nm-thick ITO transparent electrode film formed on a 1.1 mm-thick non-alkali glass surface by a sputtering deposition method.
Was cut into a size of 120 × 100 mm. A photoresist was applied on the ITO substrate, and was patterned by exposure and development by a normal photolithography method. I
After removing unnecessary portions of TO by etching, the ITO film was patterned into a stripe shape having a length of 90 mm and a width of 70 μm by removing the photoresist. 816 of the striped first electrodes are arranged at a pitch of 100 μm.

Next, a positive photoresist (OFPR-800, manufactured by Tokyo Ohka Co., Ltd.) was applied by spin coating to a thickness of 3 μm on the substrate on which the first electrode was formed. The coating film was exposed to a pattern through a photomask, developed, and patterned to form a photoresist. After development, the coating was cured at 160 ° C. In the photomask used for this patterning, 816 openings of an insulating layer having a width of 65 μm and a length of 235 μm were formed at a pitch of 100 μm in the width direction.
In the length direction, 200 pieces are arranged at a pitch of 300 μm.

After washing this substrate, it was set in a vacuum evaporation machine. In this vapor deposition machine, the position of the substrate and the shadow mask can be adjusted with a precision of about 10 μm in vacuum, respectively.
The shadow mask can be replaced.

The thin film layer including the light emitting layer was formed by a vacuum evaporation method using a resistance wire heating method. The degree of vacuum at the time of vapor deposition was 2 × 10 ⁻⁴ Pa or less, and the substrate was rotated with respect to the vapor deposition source during vapor deposition.

For patterning the light emitting layer, a shadow mask (shown in FIG. 3) in which a mask portion and a reinforcing line were formed in the same plane was used. The outline of the shadow mask is 12
0 × 84 mm, the thickness of the mask portion is 25 μm, and 272 stripe-shaped openings having a length of 64 mm and a width of 100 μm are arranged at a pitch of 300 μm. Each stripe-shaped opening has a width of 20 μm orthogonal to the opening and a thickness of 25 μm.
μm reinforcing lines are formed at 1.8 mm intervals. The shadow mask is fixed to a stainless steel frame having the same outer shape and a width of 4 mm.

First, in the arrangement as shown in FIG. 4, copper phthalocyanine was deposited to a thickness of 15 nm, and bis (N-ethylcarbazole) was deposited to a thickness of 60 nm to form a hole transport layer 5 on the entire surface of the substrate.

Next, a shadow mask for a light emitting layer was disposed in front of the substrate so that they were in close contact with each other, and a ferrite plate magnet (YBM-1B, manufactured by Hitachi Metals, Ltd.) was disposed behind the substrate. At this time, as shown in FIGS. 5 and 6, the stripe-shaped first electrode 2 is located at the center of the stripe-shaped opening of the shadow mask, the reinforcing line is located on the insulating layer, and the reinforcing line and the insulating layer Are arranged to be in contact with each other. 8-hydroxyquinoline doped with 0.3% by weight of 1,3,5,7,8-pentamethyl-4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene (PM546) in this state - aluminum complex (Alq ₃₎ was 21nm deposited and patterned green emission layer.

Next, the shadow mask is aligned with the first electrode pattern at a position shifted by one pitch,
Alq ₃ doped with 4- (dicyanomethylene) -2-methyl-6- (julolidylstyryl) pyran (DCJT) was deposited to a thickness of 15 nm to pattern the red light emitting layer.

Further, the shadow mask is aligned with the first electrode pattern at a position shifted by one pitch, and
-Bis (2,2'-diphenylvinyl) diphenyl (D
PVBi) was deposited to a thickness of 20 nm to pattern the blue light-emitting layer. The green, red, and blue light emitting layers are arranged for every three stripe-shaped first electrodes, and completely cover the exposed portions of the first electrodes.

Next, in the arrangement shown in FIG.
i was deposited on the entire surface of the substrate to a thickness of 35 nm and Alq ₃ to a thickness of 10 nm. Thereafter, the thin film layer was exposed to lithium vapor for doping (0.5 nm in equivalent film thickness).

The second electrode was formed by a vacuum evaporation method using a resistance wire heating method. The degree of vacuum at the time of deposition was 3 × 1
0 ^-4 and a Pa or less, during the deposition is rotated substrate for the two deposition sources. Similarly to the patterning of the light-emitting layer, the above-mentioned shadow mask for the second electrode was arranged in front of the substrate so that they were in close contact with each other, and a magnet was arranged behind the substrate. At this time, as shown in FIGS. 8 and 9, both are arranged so that the insulating layer matches the position of the mask portion. In this state, a second electrode was patterned by evaporating aluminum to a thickness of 400 nm. The second electrode is arranged orthogonally to the first electrode patterned in a plurality of stripes arranged at intervals, and is patterned in stripes arranged at intervals.

In this manner, the patterned green, red and blue light emitting layers are formed on the ITO striped first electrode having a pitch of 100 μm and 816 lines, and are formed so as to be orthogonal to the first electrode. , Pitch 300μ
A simple matrix type color organic electroluminescent device in which 200 m-shaped second electrodes were arranged was fabricated. Red,
Since the three light emitting regions of green and blue form one pixel, the light emitting device has 272 × 200 pixels at a pitch of 300 μm.

The thickness of the portion of the second electrode formed in this embodiment, which was shaded by the reinforcing line, was measured by an atomic force microscope (AFM). The maximum value of the difference was 70 nm. Further, the width of the region where the thickness was 90% or less of the predetermined thickness portion due to the shadow of the reinforcing line was 25 μm.

Embodiment 2 The line width of the reinforcing wire was set to 32 μm, and the opening ratio of the mesh-shaped reinforcing wire obtained by geometric calculation was set to 66%.
Was repeated. The thickness of the portion of the second electrode formed in the present embodiment, which was shaded by the reinforcing line, was measured by an atomic force microscope (AFM).
Was 50 nm. The width of the region where the thickness was 90% or less of the predetermined thickness portion due to the shadow of the reinforcing line was 15 μm. Further, the resistance value of the second electrode was reduced by about 10% as compared with Example 1.

Comparative Example 1 Example 1 was repeated except that the line width of the reinforcing wires was 40 μm and the opening ratio of the mesh reinforcing wires was 59%. For the second electrode obtained in this comparative example, the film thickness of the portion shaded by the reinforcing line was measured with an atomic force microscope (AFM). The maximum value was 80 nm. In addition, the width of the region where the film thickness was 90% or less of the predetermined film thickness portion due to the shadow of the reinforcing line was 30 μm.
Met. Further, the resistance value of the obtained second electrode was obtained in Example 1.
Approximately 15% increase.

[0039]

When the patterning of the second electrode is performed using a shadow mask having a mesh-like reinforcing line,
By setting the opening ratio of the reinforcing wire to 60% or more and further reducing the line width of the reinforcing wire to less than 40 μm, it is possible to reduce the decrease in the thickness of the second electrode below the reinforcing wire, and to reduce the resistance value. An organic electroluminescent device having the second electrode can be manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a shadow mask for patterning a second electrode used in the present invention.

FIG. 2 is a sectional view taken along line XX ′ of FIG. 1;

FIG. 3 is a plan view showing an example of a shadow mask for patterning a light emitting layer used in the present invention.

FIG. 4 is a cross-sectional view XX ′ illustrating an example of a method for forming a hole transport layer.
Sectional view.

FIG. 5 illustrates an example of a light emitting layer patterning method X
X 'sectional view.

FIG. 6 illustrates an example of a light emitting layer patterning method.
Y ′ sectional view.

FIG. 7 is a cross-sectional view XX ′ illustrating an example of a method for forming an electron transport layer.
Sectional view.

FIG. 8 illustrates an example of a second electrode patterning method.
X 'sectional view.

FIG. 9 illustrates an example of a second electrode patterning method.
Y ′ sectional view.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 first electrode 4 insulating layer (spacer) 5 hole transport layer 6 light emitting layer 7 electron transport layer 8 second electrode 10 thin film layer 11 hole transport material 12 light emitting material 13 electron transport material 14 second electrode material 30 shadow Mask 31 Mask part 32 Opening 33 Reinforcement line 34 Frame 35 One surface of mask 36 Gap

Claims (4)

[Claims] A first electrode formed on a substrate, a thin film layer formed on the first electrode, the light emitting layer including at least an organic compound, and a second electrode formed on the thin film layer. A method for manufacturing an organic electroluminescent device, comprising: a shadow mask having at least one or more openings in a mask portion, and having a mesh reinforcing line having an aperture ratio of 60% or more on one surface of the mask portion; In a state where the other surface of the mask portion is arranged facing the substrate, the second electrode material flying from the reinforcing wire side is vapor-deposited on the thin film layer through the opening to thereby form the second electrode. A method for manufacturing an organic electroluminescent device, comprising patterning. 2. The method according to claim 1, wherein the width of the reinforcing wire is less than 40 μm. 3. The method according to claim 1, wherein the second electrode is patterned in a stripe shape. 4. The method according to claim 1, wherein the width of the second electrode is 500 μm or less.