JPH11126689A - Manufacture of organic electroluminescent element and organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of leak current or a dark spot so as to provide an element with a long life and high reliability by previously sputtering a substrate surface by means of reverse sputtering. SOLUTION: Using a RF sputtering method, reverse sputtering is carried out for 5 minutes or more desirably. Because of reverse sputtering of a substrate surface, the substrate surface is smoothed, and as a result, an electrode surface is smoothed and its unevenness is reduced. Desirably, a transparent positive electrode is filmed after revere puttering of the substrate surface. Before the reverse sputtering process, the substrate is provided with roughness showing a maximum surface roughness Rmax of 15 nm or more, and after reverse sputtering, the maximum surface roughness becomes less than 15 nm, and preferably, its average is 10 nm or less. The electrode filmed on the substrate after reverse sputtering is provided with a maximum surface roughness Rmax of less than 15 nm, and its average is 10 nm or less desirably. As a sputtering gas, either of Ar, Kr, or Xe or a mixture gas containing one or more kinds of these gases is used desirably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an organic EL device using an organic compound, and more particularly, to a substrate on which an organic EL device is formed.

[0002]

2. Description of the Related Art In recent years, organic EL devices have been actively studied. This is because triphenyldiamine (TP
A basic structure in which a hole transport material such as D) is formed into a thin film by vapor deposition, and a fluorescent material such as an aluminum quinolinol complex (Alq3) is laminated as a light emitting layer, and a metal electrode (negative electrode) such as Mg having a small work function is formed. With several hundreds to several 10,000 at a voltage of around 10V
Attention is paid to the extremely high luminance of cd / m ² .

In such an organic EL device, a positive electrode (a negative electrode in the case of reverse lamination) is usually laminated on a substrate such as glass, and a hole injection transport layer, a light emitting layer, and an electron injection transport layer are formed thereon. And the like, and a negative electrode (a positive electrode in the case of reverse lamination) is further laminated thereon. Note that a hole injection transport layer, an electron injection transport layer, and the like are provided as necessary.

The positive electrode is formed of ITO as a transparent electrode.
(Tin-doped indium oxide), IZO (zinc-doped indium oxide), ZnO, SnO ₂ , In ₂ O _{3 and the} like are known. Among them, ITO electrodes are widely used as transparent electrodes having a visible light transmittance of 80% or more and a resistivity of 10 Ω / □ or less, and as transparent electrodes for liquid crystal displays (LCD), light control glass, solar cells, and the like. , Organic E
It is also expected as a positive electrode of the L element.

[0005] It is considered that a material used as a negative electrode is effective in injecting a large amount of electrons into the light emitting layer. In other words, it can be said that a material having a smaller work function is more suitable for the negative electrode. There are various materials having a small work function, and as a material used as a cathode of an EL element, for example, MgAg, AlLi, and the like described in JP-A-4-233194 are generally used.

When manufacturing a display using an organic EL element, how to reduce the defective rate is an important issue, particularly in a mass production process. Among them, the occurrence of current leakage is an important issue, and the current in the reverse direction (leakage current)
This causes a reduction in display quality such as crosstalk and uneven brightness, and furthermore, energy consumption that does not contribute to light emission such as unnecessary heat generation of the element occurs, and light emission efficiency is reduced. Further, as one of the important problems, a phenomenon of generating a non-light emitting region called a dark spot is also known. This dark spot is mainly caused by deterioration of the physical properties of the interface between the electrode and the organic layer, and is considered to be caused by oxidation or deterioration of the electrode interface, separation of the electrode, and the like.

Various studies have been made to prevent the occurrence of a leak current and a dark spot, and optimum conditions have been studied for the materials of the positive electrode and the negative electrode, the film forming method, the laminated structure, and the like. However, still leak current,
It is difficult to completely prevent dark spots from occurring, and further improvements are needed to reduce these defects.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a long-life and highly reliable organic EL device, which suppresses generation of a leak current and a dark spot, and an organic EL device.

[0009]

Various studies have been made in order to suppress the occurrence of leak current and dark spots. Then, it was found that irregularities (including dirt and organic substances, etc .; the same applies hereinafter) on the electrode surface formed on the substrate are closely related to the occurrence of leak current and dark spots. That is, if the unevenness on the electrode is large, a peeling phenomenon occurs between the organic layer formed thereafter and a problem that the short circuit is easily caused with the upper electrode occurs, which appears as a leak current or a dark spot. . It has been found that such irregularities on the electrode surface are partly due to the underlying substrate.

[0010] That is, the above object is as follows.
This is achieved by the present invention of (5). (1) A method for manufacturing an organic EL element in which an organic EL element having an electrode and an organic layer is formed on a substrate, wherein when the organic EL element is formed, the surface of the substrate is subjected to reverse sputtering by a sputtering method in advance. Of manufacturing an organic EL device.
(2) The method for producing an organic EL device according to the above (1), wherein the sputtering method is RF sputtering, and reverse sputtering is performed for 5 minutes or more. (3) The method for producing an organic EL device according to claim 1 or 2, wherein a transparent positive electrode is formed after reverse sputtering the substrate. (4) An organic EL device formed on a substrate obtained by any one of the above (1) to (3). (5) The substrate has irregularities such that the maximum surface roughness Rmax is 15 nm or more before reverse sputtering, and the maximum surface roughness Rmax is less than 15 nm after reverse sputtering, and the average is 10 nm or less. The organic EL device according to (4) above. (6) an electrode formed on the substrate after the reverse sputtering, wherein the maximum surface roughness Rmax is less than 15 nm;
The organic EL device according to the above (4) or (5), whose average is 10 nm or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail. The method for manufacturing an organic EL device according to the present invention is a method for manufacturing an organic EL device having a target and a substrate, and forming an organic EL device having an electrode and an organic layer on the substrate. When the film is formed, reverse sputtering is performed on the substrate surface in advance by a sputtering method.

Before the organic EL element is formed on the substrate, the surface of the substrate is smoothed by reverse sputtering, so that the surface of the substrate is smoothed, and the surface of the electrode is smoothed, so that unevenness is reduced.

As a sputtering method, in the case of reverse sputtering,
Usually, an RF sputtering method is used, but methods such as gas etching, ion etching, and plasma etching can be considered as methods that can obtain the same effect. In this case, chemical dry etching such as reactive ion etching or the like may be particularly preferably used.

The RF sputtering apparatus used in the present invention is not particularly limited as long as it has a power supply capable of supplying a high frequency in an RF band. Usually, the frequency is 13.56 MHz and the input power is: It is about 100-500W. As the sputtering gas to be used, an inert gas used in a normal sputtering apparatus can be used, but preferably, any of Ar, Kr, and Xe, or a mixed gas containing at least one or more of these gases is used. It is preferable to use The sputtering gas pressure is preferably about 0.3 to 3.0 Pa, and more preferably about 0.5 to 1.0 Pa.

The target is generally made of an electrode constituent material, and the distance between the substrate targets is about 4 to 15 cm.

The reverse sputtering time is preferably 5 minutes or more, more preferably 5 to 30 minutes, particularly 8 to 15 minutes.
Minutes are preferred. The surface roughness Rmax of the substrate on which the reverse sputtering process is performed is not particularly limited, but preferably has at least 15 nm or more, more preferably 15 to 30 nm. Substrates having this level of surface roughness are relatively inexpensive, readily available, and can be preferably used in accordance with the present invention. The surface roughness Rmax of the substrate surface after the reverse sputtering treatment is preferably less than 15 nm, more preferably 5 to <15 nm, and particularly preferably in the range of 5 to 13 nm. The average value is preferably 10 nm
Hereinafter, it is more preferably 8 to 10 nm.

The substrate is not particularly limited, as long as the organic EL element can be laminated. In the case of the side from which emitted light is taken out, a transparent or translucent material such as glass, quartz, resin or the like is used. It is preferably used, and glass is particularly preferred. Further, the emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate. When the emitted light is not taken out, the substrate may be transparent or opaque. When the substrate is opaque, ceramics or the like may be used.

Although the size of the substrate is not particularly limited, it is preferable that the maximum length, especially the diagonal length be 100 to 200.
mm, especially in the range of 120 to 180 mm. When the size of the substrate exceeds 200 mm, the film forming apparatus becomes large, and it is difficult to obtain a uniform resistivity, the film forming efficiency is reduced, and the film thickness control becomes difficult.

The substrate may be cleaned before performing the reverse sputtering. The cleaning is usually performed by sequentially performing ultrasonic cleaning using a neutral detergent, acetone, ethanol, or the like, and finally drying and setting in a vacuum container.

On the substrate subjected to the surface treatment as described above, preferably, electrodes such as a positive electrode and a negative electrode are formed, and an organic layer is formed to form an organic EL element. .

The organic EL device obtained according to the present invention has a structure in which a positive electrode (a negative electrode in reverse lamination) is provided on a substrate, and a negative electrode (a positive electrode in reverse lamination) is provided thereon. Each has at least one organic layer such as a charge transport layer and a light emitting layer, and further has a protective layer as an uppermost layer. Note that the charge transport layer can be omitted.

The organic EL device obtained by the present invention is not limited to the above-described example, but may be of various configurations. For example, a light emitting layer is provided alone, and an electron injection / transport layer is provided between the light emitting layer and the metal electrode. May be interposed. If necessary, the hole injecting / transporting layer and the light emitting layer may be mixed.

The positive electrode and the negative electrode can be formed by vapor deposition or sputtering, and the organic layer such as the light-emitting layer can be formed by vacuum vapor deposition or the like. After the formation, patterning can be performed by a method such as etching, whereby a desired light emitting pattern can be obtained. Further, the substrate is a thin film transistor (TFT), and by forming each film according to the pattern, a display and drive pattern can be used as it is.

It is preferable to determine the material and thickness of the positive electrode so that the transmittance of emitted light is 80% or more. Specifically, an oxide transparent conductive thin film is preferable. For example, tin-doped indium oxide (IT
O), zinc-doped indium oxide (IZO), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and zinc oxide (ZnO) are preferable. These oxides may deviate somewhat from their stoichiometric composition. In ITO, In ₂ O ₃ and SnO are usually used.
₂ is contained in a stoichiometric composition, but the oxygen content may be slightly deviated from this. The mixing ratio of SnO ₂ to In ₂ O ₃ is preferably 1 to 20 wt%, more preferably 5 to 12 wt%.
% Is preferred. The mixing ratio of ZnO ₂ to In ₂ O ₃ is:
The content is preferably 1 to 20% by weight, more preferably 5 to 12% by weight.

For forming a positive electrode, a sputtering method is preferable. As the sputtering method, a high-frequency sputtering method using an RF power supply or the like is also possible, but the DC sputtering method should be used in consideration of the ease of controlling the physical properties of the positive electrode to be formed and the smoothness of the film formation surface. Is preferred.

The DC sputtering apparatus is preferably a magnetron DC sputtering apparatus, and the magnetic field strength is such that the magnetic flux density B on the target is preferably B = 500 to 2000 Gauss, particularly 800 to 150 Gauss.
About 0 Gauss is preferable. The higher the magnetic flux density on the target, the better.When the magnetic flux density is increased and the magnetic field strength is increased, the number of ions that collide with the cathode target of the sputtering gas in the plasma is formed by adopting an electrode structure that traps electrons near the target. And the plasma density increases. As the plasma density increases, the frequency of collisions between the particles in the plasma increases, some of the kinetic energy is lost, and the sputtered particles deposit gently on the substrate. The method for obtaining a magnetic field on the target is not particularly limited, but it is preferable to dispose a magnet on the back side of the target, particularly in the cooling section. As a magnet for applying such a magnetic field, for example, Fe
—Nd—B, Sm—Co, ferrite, alnico, etc., among which Fe—Nd—B and Sm—Co are preferable because a large magnetic flux density can be obtained.

As the bias voltage, a voltage between the target and the substrate (bias electrode) is preferably 100 to 30.
0V, preferably in the range of 150-250V. If the bias voltage is too high, the acceleration of the particles increases, and the electrode layer is easily damaged. On the other hand, if the bias voltage is too low, the plasma discharge cannot be maintained or the plasma density becomes low, making it difficult to obtain the above effects.

It is preferable that both the magnetic field strength and the bias voltage are adjusted to optimal values within the above ranges according to the use environment, the scale of the apparatus, and the like.

The electric power of the DC sputtering device is preferably in the range of 0.1 to 4 W / cm ² , particularly 0.5 to 1 W / cm ² . The deposition rate depends on the conditions of the apparatus such as a magnet, but is preferably 5 to 100 nm / min, particularly 10 to 100 nm / min.
A range of 〜50 nm / min is preferred. The film forming conditions at the time of sputtering include a gas pressure generally used for forming an electrode, for example, 0.1 to 0.5 Pa, and a distance between the substrate and the target of 4-1.
The range may be 0 cm.

However, when the smoothness of the substrate is important, the product of the deposition gas pressure and the distance between the substrate targets should be in the range of 20 to 65 Pa · cm, preferably 20 to 60 Pa · cm, during the sputtering. It is. The sputtered atoms lose their kinetic energy on their way to the substrate, the rate of which depends on both the deposition gas pressure and the distance between the substrate targets. The above-mentioned film forming condition is good in which the kinetic energy of the sputtered atoms is lost due to the scattering by the sputter gas, and becomes almost zero. If the product of the film forming gas pressure and the distance between the substrate targets is less than 20 Pa · cm, the kinetic energy of the sputtered molecules is large, causing physical damage to the organic layer. Also, when the product of the deposition gas pressure and the distance between the substrate targets exceeds 65 Pa · cm, the deposition gas itself is scattered,
Reverse sputtering on the substrate starts, and the film surface is roughened.

The above-mentioned inter-substrate-target distance is the distance that the sputtered atoms pass before reaching the substrate, and is the process of being scattered by the sputter gas. Therefore, if the substrate is located directly above the target,
The distance between the substrate and the target is almost equal to the distance between the electrodes of the sputtering apparatus. However, when the substrate is offset from the target, the distance at which the sputtered atoms are scattered is longer than the distance between the electrodes. , You need to consider this. That is, the inter-substrate target distance described in the present invention is the distance that sputtered atoms actually travel before reaching the substrate.

The sputtering gas may be an inert gas used in a normal sputtering apparatus or a reactive gas such as N ₂ , H ₂ , O ₂ , C ₂ H ₄ , and NH ₃ in reactive sputtering. Although it can be used, it is preferable to use any of Ar, Kr, and Xe, or a mixed gas containing at least one or more of these gases. These gases are preferred because they are inert gases and have a relatively large atomic weight. Particularly, Ar, Kr, and Xe alone are preferred. Ar, K
By using the r and Xe gas, while the sputtered atoms reach the substrate, the collision with the gas is repeated,
The kinetic energy is reduced and reaches the substrate. From this, the kinetic energy of the sputtered atoms is
Physical damage to the L structure is reduced. Also,
A mixed gas containing at least one gas of Ar, Kr, and Xe may be used. When such a mixed gas is used, the total partial pressure of Ar, Kr, and Xe is set to 50% or more and used as a main sputtering gas. Used. Thus, Ar, Kr,
By using a mixed gas obtained by combining at least one kind of Xe and an arbitrary gas, reactive sputtering can be performed while maintaining the effects of the present invention.

When any of Ar, Kr, and Xe is used as the main sputtering gas as the sputtering gas, the product of the distance between the substrate targets is preferably 25 to 55 Pa · cm, particularly 30 to 55 Pa · cm, respectively. 50 Pa · cm, Kr
When using: 20 to 50 Pa · cm, especially 25 to 45 Pa · cm
cm, Xe: 20 to 50 Pa · cm, especially 20 to 50 Pa · cm
A range of 40 Pa · cm is preferable. Under these conditions, a preferable result can be obtained by using any sputtering gas, but it is particularly preferable to use Ar.

By forming the positive electrode under the above-mentioned conditions, the collision between the sputtered atoms and the gas is repeated while the atoms reach the substrate to reduce the kinetic energy.
By arriving at the substrate, it becomes possible to form a positive electrode having a higher amorphous property, thereby suppressing grain growth and smoothing the film surface.

The positive electrode formed under the above film forming conditions has a tendency that the resistivity increases when the film is formed in a usual substrate-target positional relationship. Can be suppressed. Note that the film may be formed together with a transparent electrode serving as a base in order to further reduce the resistivity. For this reason, it is preferable that the film thickness is relatively thin, that is, 10 to 20 nm when the film is laminated together with the transparent electrode serving as the base.

The maximum surface roughness (Rmax) of the electrode surface is preferably less than 15 nm, more preferably 13 nm or less, particularly preferably 6 to 10 nm, more preferably 6 to 8 nm. The average value is preferably 10 nm or less, particularly preferably about 8 to 10 nm. The average surface roughness (Ra) is preferably 3.0 nm or less, more preferably 2.0 nm or less, and particularly preferably 1.0 to 1.5 nm. It is preferable to make the surface of the positive electrode smooth because it is possible to further suppress the occurrence of a leak current, a dark spot, and the like. The total thickness of the positive electrode is 10
It is preferable to set it to about 500 nm. Further, it is necessary that the driving voltage be low in order to improve the reliability of the element.

In order to suppress the electric resistance of the underlying transparent conductive film, the pressure during sputtering is preferably set to 0.10.
A film formed in the range of 0.3 to 0.3 Pa, particularly 0.15 to 0.25 Pa is used. Such a transparent conductive film, especially IT
O and the like are commercially available, and can be purchased and used. A two-layer structure of the base transparent conductive film and the positive electrode is preferable because the electrode resistance can be reduced. The thickness of the underlying transparent conductive film is usually preferably about 100 to 200 nm. The thickness of the positive electrode when formed on the underlying transparent conductive film is preferably 10 nm or more, more preferably 2 nm or more.
0 nm or more is preferable, and the upper limit is not particularly limited. However, when importance is placed on light transmittance, the transmittance is set to 80%.
The thickness is preferably 100 nm or more.
The following is preferred.

When the underlying transparent conductive film and the positive electrode are formed in a laminated structure, the gas pressure during sputtering is increased in addition to the discontinuous (stepwise) formation of the positive electrode on the underlying transparent conductive film. The film may be changed continuously to form films having different film quality continuously. The effect in this case is almost the same as the above case, but the film forming process can be simplified.

When a positive electrode is formed on the underlying transparent conductive film (in the case of reverse lamination, it becomes a negative electrode), the surface of the underlying transparent conductive film is previously subjected to plasma treatment, more specifically, reverse sputtering or the like. Is preferred. By subjecting the surface of the underlying transparent conductive film to a plasma treatment, the surface of the underlying transparent conductive film is planarized, and the positive electrode formed thereafter is also planarized.
As the conditions of the reverse sputtering, preferably, the above-mentioned sputtering gas is used, the gas pressure is 0.5 to 1.0 Pa, and the input power is 0.5.
It is preferable to carry out at about 3 W / cm ^{2 for} about 1 to 10 minutes.

In a large device such as a display, since the resistance of the positive electrode such as ITO is large and a voltage drop occurs, metal wiring such as Al may be provided.

The negative electrode is preferably made of a material having a low work function for effectively injecting electrons, for example, K, Li, N
a, Mg, La, Ce, Ca, Sr, Ba, Al, A
g, In, Sn, Zn, Zr, Cs, Er, Eu, G
a, Hf, Nd, Rb, Sc, Sm, Ta, Y, Yb or other metal element alone, or BaO, BaS, CaO,
HfC, LaB ₆ , MgO, MoC, NbC, PbS,
SrO, TaC, ThC, ThO ₂ , ThS, TiC,
TiN, UC, UN, UO ₂ , W ₂ C, Y ₂ O ₃ , ZrC,
It is preferable to use a compound such as ZrN or ZrO ₂ . Alternatively, in order to improve the stability, two components containing a metal element,
It is preferable to use an alloy system of the components. As an alloy system, for example, Al.Ca (Ca: 5 to 20 at%), Al.Ca
In (In: 1 to 10 at%), Al.Li (Li: 0.
Aluminum alloys such as Al.R (R represents a rare earth element containing Y and Sc), and In.Mg.
(Mg: 50 to 80 at%) and the like. Among these, in particular, Al alone or Al.Li (Li: 0.4 to 6.5)
(But not including 6.5) at%) or (Li: 6.5)
１４14 at%), Al · R (R: 0.1 to 25, especially 0.1 to 25 at%).
Aluminum alloys such as 5 to 20 at%) are preferred because they do not easily generate compressive stress. Therefore, such a negative electrode constituting metal or alloy is usually used as a sputter target. These work functions are 4.0 eV or less. Particularly, metals and alloys having a small work function are preferable because more electrons can be injected into the light emitting layer.

After the negative electrode is formed, a metal thin film having better electric conductivity may be laminated. In particular, the negative electrode thin film formed according to the present invention may have a low film density after being formed of a material. In that case, water or the like easily enters from the outside, which affects the element life. Therefore, when a metal thin film having good electric conductivity is laminated, a more stable element can be formed without lowering the voltage at the electrodes of the element. Cu, Ag, Au, Ru, Fe, Ni, P
d, Pt, Ti, Ta, Cr, Mo, W, Co, Rh,
Examples thereof include Ir, Zn, Al, Ga, and In, and these metals may be mixed and used in an arbitrary composition. Also,
As long as the electric conductivity is equivalent to that of a metal, a stable compound may be used. Stable compounds include, for example, IrO ₂ ,
MoO ₂ , NbO, OsO ₂ , ReO ₂ , ReO ₃ , R
uO _{2 and the} like.

The thickness of the negative electrode thin film may be a certain thickness or more for sufficiently injecting electrons, and may be 20 nm or more, preferably 50 nm or more. Further, the thickness of the metal thin film laminated on the negative electrode may be a thickness capable of reducing electric resistance, and is 50 nm or more, preferably 1 nm or more.
The thickness may be 00 nm or more. The upper limit of the total film thickness of the negative electrode and the metal thin film layer to be laminated is not particularly limited, but usually the film thickness may be about 100 to 500 nm.

As a factor that causes abnormal grain growth of the electrode material, it is considered that the kinetic energy and heat energy of the electrode material particles themselves are high, but the strain energy and the like introduced into the thin film during the electrode formation process are also considered. there is a possibility. The strain energy includes a tensile stress and a compressive stress, and it is known that a problem such as a dark spot or a leak current hardly occurs in an electrode having a tensile stress, and that abnormal grain growth is mainly related to the compressive stress. In this case, when the electrode surface is evaluated by the X-ray diffraction method (XRD), the diffraction peak slightly shifts to a high angle or a low angle with respect to the diffraction angle observed in the bulk, so that the presence or absence of strain energy (residual stress) is determined. The type (tensile stress, compressive stress) can be checked. Then, if the film can be formed under a condition in which almost no compressive stress exists under the above conditions, damage to the organic layer and leakage can be prevented.

For example, in the case of aluminum or an aluminum alloy, it is preferable that the distance d is shifted to be substantially equal to or larger than about 0.0002 nm with respect to the plane distance d of the bulk (111) plane. Therefore, in the case of aluminum, it is preferable that the surface distance d of the bulk surface is substantially equal to 0.23380 nm or shifted to a direction larger than this by about 0.0002 nm. In the case of a transparent electrode, for example, in the case of ITO, the peak slightly varies depending on the Sn composition ratio, but the bulk of In ₂ O ₃ (222)
It is preferable that the distance is shifted in a direction equal to or larger than about 0.0002 nm with respect to the plane distance d = 0.29210 nm.

In the sputtering method, there is a phenomenon that high-energy ions incident on the target are elastically reflected on the target surface. It is known that most of the particles to be reflected are in an atomic state, but have a high kinetic energy and are mixed into the film during the film formation process. It is considered that such a mixture of the sputtering gas into the film causes a microscopic structural change of the film, and causes a compressive stress as described above. In addition, it has been confirmed that the sputter gas element concentration in the film changes depending on the film forming conditions, and decreases under the above film forming conditions.

The element concentration of the sputter gas in the electrode film varies depending on the type of the sputter gas component elements, but is preferably 0.5 at% or less, more preferably 0.1 to 0.45 at%, and particularly preferably 0 to 0.45 at%. About 0.2 to 0.4 at% is preferable. The content of such an element can be confirmed by secondary ion mass spectrometry (SIMS) or the like.

[0048] After the electrode film formation, the protective film and / or metal material such as Al, an inorganic material such as SiO _X, may be formed of other protective layer using an organic material such as Teflon. This protective film may be transparent or opaque. In general,
The thickness of the protective layer is about 50 to 1200 nm. The protective layer may be formed by a general sputtering method, a vapor deposition method, or the like, in addition to the reactive sputtering method described above.

The organic EL device obtained according to the present invention may be provided with one or more oxides, nitrides or carbides of the constituent material of the negative electrode as a protective film by utilizing the reactive sputtering as described above. . In this case, the raw material of the protective film usually has the same composition as the negative electrode material, but may have a different composition ratio from the negative electrode material, or may lack one or more of the material components. In this manner, by using the same material or the like as the negative electrode, continuous film formation with the negative electrode becomes possible.

The amount of O in the oxide, the amount of N in the nitride or the amount of C in the carbide may deviate from this stoichiometric composition, and may be in the range of 0.5 to 2 times the composition. I just need.

As a target, a sintered body of the same material as that of the negative electrode is preferably used, and as a reactive gas, O ₂ , CO or the like is used when forming an oxide, and N 2 is used when forming a nitride. ₂ , NH ₃ , NO, NO ₂ , N ₂ O and the like. When forming a carbide, CH ₄ , C ₂ H ₂ , C _2
2 H _{4 and the} like. These reactive gases may be used alone or as a mixture of two or more.

The thickness of the protective film may be a certain thickness or more, preferably 50 nm or more, more preferably 100 nm or more, particularly preferably in the range of 100 to 1000 nm, in order to prevent entry of moisture, oxygen or an organic solvent.

The total thickness of the negative electrode and the protective film is not particularly limited, but may be generally about 100 to 1000 nm.

By providing such a protective film, oxidation of the negative electrode and the like are further prevented, and the organic EL element can be driven stably for a long period of time.

Further, it is preferable to form a sealing layer on the device in order to prevent oxidation of the organic layers and electrodes of the device. The sealing layer is made of an adhesive resin layer such as a commercially available low-moisture-absorbing light-curing adhesive, an epoxy-based adhesive, a silicone-based adhesive, and a cross-linked ethylene-vinyl acetate copolymer adhesive sheet to prevent moisture from entering. Is used to adhere and seal a sealing plate such as a glass plate. Besides a glass plate, a metal plate, a plastic plate or the like can be used.

Next, the organic layer of the organic EL device obtained according to the present invention will be described. The light emitting layer is a hole
And a function of injecting electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The charge transport layer has a function of facilitating injection of holes from the positive electrode, a function of transporting holes, and a function of blocking electrons, and is also called a hole injection transport layer.

In addition, if necessary, for example, when the electron injecting / transporting function of the compound used for the light emitting layer is not so high, injection of electrons from the negative electrode between the light emitting layer and the negative electrode as described above. May be provided with an electron injecting and transporting layer having a function of facilitating electron transport, a function of transporting electrons, and a function of blocking holes.

The hole injection transport layer and the electron injection transport layer
Increases and confines holes and electrons injected into the light emitting layer,
Optimize the recombination region and improve luminous efficiency.

The hole injecting / transporting layer and the electron injecting / transporting layer may be provided separately for a layer having an injection function and a layer having a transport function.

The thickness of the light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited, and vary depending on the forming method.
It is preferable that the thickness be 0 to 200 nm.

The thickness of the hole injecting / transporting layer and the thickness of the electron injecting / transporting layer depend on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. . When the injection layer and the transport layer for electrons or holes are separated from each other, it is preferable that the injection layer has a thickness of 1 nm or more and the transport layer has a thickness of 1 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and 500 nm for the transport layer.
It is about. For such a film thickness, the injection / transport layer is 2
The same applies when providing layers.

By controlling the film thickness in consideration of the carrier mobility and carrier density (determined by ionization potential and electron affinity) of the combined light emitting layer, electron injection transport layer and hole injection transport layer, recombination is achieved. It is possible to freely design the region and the light emitting region, and it is possible to design the light emission color, control the light emission luminance and light emission spectrum by the interference effect of both electrodes, and control the spatial distribution of light emission.

The light emitting layer of the organic EL device of the present invention contains a fluorescent substance which is a compound having a light emitting function. Examples of the fluorescent substance include, for example, JP-A-63-26469.
And metal complex dyes such as tris (8-quinolinolato) aluminum [Alq3] as disclosed in Japanese Patent Publication No. 2 (1993) -210, and the like. In addition, quinacridone, coumarin, rubrene, styryl dyes, tetraphenylbutadiene, anthracene, perylene, coronene, 12-phthaloperinone derivatives, and the like can be used in addition or alone. The light emitting layer may also serve as the electron injection / transport layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. These fluorescent substances may be deposited.

The electron injecting and transporting layer provided as necessary includes an organic metal complex such as tris (8-quinolinolato) aluminum, an oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoline derivative, and a quinoxaline derivative. , A diphenylquinone derivative,
Nitro-substituted fluorene derivatives and the like can be used.
As described above, the electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The formation of the electron injecting and transporting layer may be performed by vapor deposition or the like, similarly to the light emitting layer.

When the electron injecting and transporting layer is provided separately for the electron injecting layer and the electron transporting layer, a preferable combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having the higher electron affinity from the cathode side. This stacking order is the same when two or more electron injection / transport layers are provided.

The hole injecting and transporting layer is described in, for example, JP-A-63-295695 and JP-A-2-191694.
JP, JP-A-3-792, JP-A-5-2346
No. 81, JP-A-5-239455, JP-A-5
JP-A-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100
Various organic compounds described in JP-A-172, EP0650955A1, and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, polythiophene, etc. . Two or more of these compounds may be used in combination, and when they are used in combination, they may be stacked as separate layers or mixed.

When the hole injecting and transporting layer is provided separately as a hole injecting layer and a hole transporting layer, a preferred combination can be selected from the compounds for the hole injecting and transporting layer. At this time, it is preferable to stack the layers of the compound having the smaller ionization potential in order from the positive electrode (ITO or the like) side. It is preferable to use a compound having a good thin film property on the surface of the positive electrode. Such a stacking order is the same when two or more hole injection / transport layers are provided. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In the case of forming an element, a thin film having a thickness of about 1 to 10 nm can be made uniform and pinhole-free because evaporation is used, so that the hole injection layer has a small ionization potential and has absorption in the visible region. Even when such a compound is used, it is possible to prevent a change in the color tone of the emission color or a decrease in efficiency due to reabsorption.

The above-mentioned compound may be deposited on the hole injection / transport layer in the same manner as the light emitting layer.

As the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL to optimize the extraction efficiency and the color purity.

When a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance of the element and the contrast of display are improved.

Further, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film absorbs EL light and emits light from the phosphor in the fluorescence conversion film, thereby performing color conversion of the emission color. It is formed from a fluorescent material and a light absorbing material.

As the fluorescent material, basically, a material having a high fluorescence quantum yield may be used, and it is desirable that the fluorescent material has strong absorption in the EL emission wavelength region. Actually, laser dyes are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalo, etc.) naphthaloimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds, A styryl compound, a coumarin compound, or the like may be used.

Basically, a material that does not extinguish the fluorescence may be selected as the binder, and a material that can be finely patterned by photolithography, printing, or the like is preferable.
Further, a material that does not suffer damage during the deposition of ITO is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

For forming the hole injection transport layer, the light emitting layer and the electron injection transport layer, it is preferable to use a vacuum deposition method since a uniform thin film can be formed. When a vacuum deposition method is used, a homogeneous thin film having an amorphous state or a crystal grain size of 0.1 μm or less can be obtained. If the crystal grain size exceeds 0.1 μm, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the charge injection efficiency is significantly reduced.

The conditions for vacuum deposition are not particularly limited.
The degree of vacuum is 0 ^-4 Pa or less, and the deposition rate is 0.01 to 1 nm /
It is preferable to set it to about sec. Further, it is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained. Further, the driving voltage of the element can be reduced, and the growth and generation of dark spots can be suppressed.

In the case where a plurality of compounds are contained in one layer when a vacuum evaporation method is used for forming each of these layers, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

If the surface of the electrode film is reverse-sputtered for about 1 to 2 minutes under the above-described reverse sputtering conditions immediately before the organic layer is vacuum-deposited, it is possible to remove stains such as organic substances and moisture attached to the surface. .

The organic EL device obtained according to the present invention is usually used as a DC-driven EL device, but it can also be driven by AC or pulse. The applied voltage is
Usually, it is about 2 to 20V.

[0082]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention together with comparative examples. <Example 1> A glass substrate (Corning: 7059) having a length of 50 mm, a width of 50 mm and a thickness of 1.1 mm was set in an RF sputtering apparatus, and the surface of the substrate was reverse-sputtered for 5 minutes by self-bias. At this time, the RF power source was 13.56 MHz in frequency, the power was 250 W, the sputtering gas was Ar, and the pressure during reverse sputtering was 1.0 Pa.

When the maximum surface roughness Rmax of the reverse-sputtered substrate surface was measured at 10 points, it was as shown in Table 1, and the average value was 8.99 nm.

Further, a positive electrode having a thickness of 200
nm of ITO was formed by a sputtering method. At this time, ITO (Sn: 10 wt%) was used as the target, the sputtering gas pressure was 0.15 Pa, and the distance between the target and the substrate (Ts) was 9.0 cm. Input power is 1.2W / cm
^{2. The} film formation rate was 16.0 nm / min.

The maximum surface roughness of the positive electrode formed on the substrate was measured at 10 points, as shown in Table 1, and the average value was 9.80 nm.

Thereafter, patterning was performed, ultrasonic cleaning was performed using a neutral detergent, acetone, and ethanol, and then the resultant was pulled out of boiling ethanol and dried. This transparent electrode surface is
After washing with V / O ₃ , the inside of the tank was evacuated to 1 × 10 ⁻⁴ Pa or less by fixing with a substrate holder of a vacuum evaporation apparatus.

Next, N, N'-
Diphenyl-m-tolyl-4,4'-diamine-1,
1′-biphenyl (TPD) was deposited at a deposition rate of 0.2 nm / sec to a thickness of 55 nm to form a hole injection transport layer.

Further, while maintaining the reduced pressure, Alq3: tris (8-quinolinolato) aluminum was evaporated at a deposition rate of 0,1.
Evaporation was performed at a thickness of 50 nm at 2 nm / sec to form an electron injection / transport / light-emitting layer.

Next, the wafer was transferred from the vacuum evaporation apparatus to a sputtering apparatus, and a Mg / Ag alloy (Ag: 5 at
%) As a target, and a negative electrode was formed to a thickness of 200 nm. At this time, Ar was used as the sputtering gas, the gas pressure was 4.5 Pa, the distance between the target and the substrate (Ts) was 9.0 cm, and the input power was 1.2 W / cm ² .

Finally, SiO ₂ was sputtered to a thickness of 200 nm to obtain an organic EL device as a protective layer. This organic E
In the L element, two parallel striped negative electrodes and eight parallel striped positive electrodes are orthogonal to each other,
Element elements (pixels) of 2 × 2 mm in length and width are arranged at an interval of 2 mm from each other to form an 8 × 2 16-pixel element.

With respect to the obtained organic EL element, the number of current leaks between electrodes of 160 pixels (10 elements) was examined. In addition, when the resistance value between the electrodes was 200 MΩ or less, the leakage was determined. As a result, the number of leaks was 1/160.

A direct current voltage was applied to the organic EL device in a dry argon atmosphere, and the organic EL device was treated at a constant current density of 10 mA / cm ² for 30 minutes.
It was driven continuously for 0 hours. The dark spot after continuous driving was visually evaluated. As a result, out of 160 pixels,
Five dark spots having a diameter of 200 μm or less were confirmed.

[0093]

[Table 1]

Example 2 Reverse sputtering was performed in the same manner as in Example 1 except that the time for reverse sputtering on the substrate surface was changed to 10 minutes. When the maximum surface roughness of the substrate surface subjected to the reverse sputtering treatment was measured at 10 points, it was as shown in Table 1, and the average value was 9.02 nm.

Next, an ITO transparent electrode was formed in the same manner as in Example 1. When the maximum surface roughness of the positive electrode formed on the substrate was measured at 10 points, it was as shown in Table 1,
Its average value was 8.97 nm.

Further, an organic EL device was manufactured in the same manner as in Example 1. With respect to the obtained organic EL device, the number of current leaks between electrodes of 160 pixels (for 10 devices) was examined. As a result, the number of leaks was 0/160.

The organic thin film light emitting device was continuously driven in the same manner as in Example 1, and the dark spot after driving was visually evaluated. As a result, the diameter 20 out of 160 pixels
Three dark spots of 0 μm or less were confirmed.

<Comparative Example 1> In the same manner as in Example 1, except that the substrate surface was not subjected to reverse sputtering, ITO was used.
A transparent electrode was formed. When the maximum surface roughness of the untreated substrate surface was measured at 10 points, it was as shown in Table 1, and the average value was 12.0 nm. Further, when the maximum surface roughness of the positive electrode formed on the substrate was measured at 10 points, the average value was 16.6 nm. Compared with the ITO film formed on the substrate subjected to the reverse sputtering treatment, there is not much difference in the average value of the surface roughness, but the film on the untreated substrate is partially roughened to about 30 nm. Existed.

Further, an organic EL device was manufactured in the same manner as in Example 1. With respect to the obtained organic EL device, the number of current leaks between electrodes of 160 pixels (for 10 devices) was examined. As a result, the number of leaks was 158/160.

The organic thin film light emitting device was continuously driven in the same manner as in Example 1, and the dark spot after driving was visually evaluated. As a result, the diameter 20 out of 160 pixels
135 dark spots of 0 μm or less were confirmed.

[0101]

As described above, according to the present invention, it is possible to provide a method for manufacturing an organic EL device having a long life and high reliability by suppressing the occurrence of a leak current and a dark spot, and an organic EL device.

Claims (6)

[Claims] 1. A method for manufacturing an organic EL element, comprising forming an organic EL element having an electrode and an organic layer on a substrate, wherein the organic EL element is formed by inverting the surface of the substrate in advance by a sputtering method. A method for manufacturing an organic EL element to be subjected to a sputtering process. 2. The method for manufacturing an organic EL device according to claim 1, wherein said sputtering method is RF sputtering, and reverse sputtering is performed for 5 minutes or more. 3. The method for manufacturing an organic EL device according to claim 1, wherein a transparent positive electrode is formed after reverse sputtering the substrate. 4. An organic EL device formed on a substrate obtained by the method according to claim 1. 5. The substrate has irregularities such that the maximum surface roughness Rmax is 15 nm or more before reverse sputtering, and the maximum surface roughness Rmax is less than 15 nm after reverse sputtering, and the average is The organic EL device according to claim 4, which has a thickness of 10 nm or less. 6. The organic EL device according to claim 4, wherein the electrode formed on the substrate after the reverse sputtering treatment has a maximum surface roughness Rmax of less than 15 nm and an average of 10 nm or less. .