KR102247476B1 - Solvent for forming organic emitting layer and organic light emitting diode using the same - Google Patents

Abstract

The present invention discloses a solvent for forming an organic light emitting layer and an organic electroluminescent device using the same. The disclosed solvent for forming an organic light-emitting layer and an organic light-emitting device using the same include an organic light-emitting layer, a first electrode for supplying holes to the organic light-emitting layer, and a second electrode for supplying electrons to the organic light-emitting layer. In the electroluminescent device, the organic light emitting layer is formed using a solvent, the solvent includes a first solvent and a second solvent, and the first solvent is an aromatic ester, an aromatic ether, It includes two groups selected from the group consisting of an aromatic hydrocarbon or an aromatic ketone, and the second solvent includes an aromatic ether. The solvent has an effect of easy ejection due to its low viscosity.

Description

Solvent for forming organic emitting layer and organic light emitting diode using the same}

The present invention relates to a solvent for forming an organic light-emitting layer and an organic electroluminescent device using the same, and more particularly, to a solvent for forming an organic light-emitting layer and an organic electroluminescent device using the same.

Recently, various flat panel display devices capable of reducing the weight and volume, which are disadvantages of a cathode ray tube, have been developed. Such flat panel displays include liquid crystal displays (Liquid Crystal Display: hereinafter referred to as "LCD"), field emission displays (FED), plasma display panels (hereinafter referred to as "PDP"), and electric fields. There is a light emitting device (Electroluminescence Device) and the like.

Electroluminescent devices are roughly classified into inorganic light emitting diode displays and organic light emitting diode displays according to the material of the light emitting layer. As a self-luminous device that emits light, it has a fast response speed and great luminous efficiency, luminance, and viewing angle.

An organic electroluminescent device, one of the electroluminescent devices, has high luminance and low operating voltage characteristics. In addition, since it is a self-luminous type that emits light by itself, it has a large contrast ratio, enables the implementation of an ultra-thin display, and has a response time of several microseconds (µs), making it easy to implement moving images, and there is no limit on the viewing angle and is stable even at low temperatures There is an advantage.

The organic light emitting device is largely composed of an array device and an organic light emitting diode. The array device includes a switching thin film transistor connected to a gate and a data line, and a driving thin film transistor connected to an organic light emitting device. In addition, the organic electroluminescent device includes a first electrode connected to the driving thin film transistor, an organic emission layer, and a second electrode.

In the organic electroluminescent device having such a configuration, the light generated from the organic light emitting layer is emitted toward the first electrode or the second electrode to display an image. Considering the aperture ratio, etc., in recent years, it is usually emitted toward the second electrode. It is manufactured in a top emission method that displays an image using light that is generated.

In such a general organic light emitting display device, the organic light emitting layer is usually formed by a thermal evaporation method using a shadow mask. It is becoming increasingly difficult to apply to substrates.

To solve this problem, a method of forming an organic light-emitting layer using a solvent for forming an organic light-emitting layer has been proposed. Here, in order to secure the characteristics of the organic light emitting device, the organic light emitting material contained in the solvent for forming the organic light emitting layer must be maintained at a certain concentration or higher.

However, as the concentration of the organic light-emitting material of the polymer increases, the viscosity of the solvent for forming the organic light-emitting layer increases, and thus, it is difficult to discharge the solvent for forming the organic light-emitting layer when the organic light-emitting layer is formed.

The present invention is a solvent for forming an organic light emitting layer including a first solvent and a second solvent, since the second solvent has a boiling point and viscosity lower than that of the first solvent, the solvent for forming an organic light emitting layer and an organic electric field using the same It is an object to provide a light emitting device.

In order to solve the problems of the prior art as described above, the solvent for forming an organic light emitting layer and the organic electroluminescent device using the same include an organic light emitting layer, a first electrode for supplying holes to the organic light emitting layer, and electrons to the organic light emitting layer. In the organic electroluminescent device comprising a second electrode for supplying, the organic light emitting layer is formed by using a solvent, the solvent includes a first solvent and a second solvent, and the first solvent is an aromatic ester ( aromatic ester), an aromatic ether, an aromatic hydrocarbon, or an aromatic ketone, and the second solvent contains an aromatic ether. do. The solvent is characterized in that it is easy to discharge due to its low viscosity.

The solvent for forming an organic light-emitting layer according to the present invention and an organic electroluminescent device using the same, in the solvent for forming an organic light-emitting layer including a first solvent and a second solvent, the second solvent has a lower boiling point and viscosity than the first solvent. , It has the effect of easy dispensing.

1 is a plan view showing an organic light emitting display device according to the present invention.
2 is a diagram illustrating a cross-sectional view taken along line II′ of the organic light emitting display device of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In addition, in the drawings, the size and thickness of the device may be exaggerated for convenience. The same reference numbers throughout the specification indicate the same elements.

1 is a plan view showing an organic light emitting display device according to the present invention. Referring to FIG. 1, the organic light emitting display device of the present invention includes a plurality of pixel areas, and each of the pixel areas includes a driver and a pixel portion.

The pixel region is defined by crossing the gate wiring 20 and the data wiring 10 on the substrate 100. In addition, a driver including a thin film transistor Tr is formed in the crossing region. A pixel portion including an organic light emitting device including a first electrode 111, an organic light emitting layer, and a second electrode is formed above the driving unit.

The thin film transistor Tr includes a gate electrode 105, a semiconductor layer 101, a source electrode 107, and a drain electrode 108. The source electrode 107 of the thin film transistor Tr is formed by branching from the data line 10. In addition, the drain electrode 108 of the thin film transistor Tr is connected through a contact hole of the gate electrode 105. In addition, the drain electrode 108 is configured to come into contact with the first electrode 111 of the organic light emitting device configured in the pixel portion.

A bank pattern 112 is disposed around the pixel portion and has a closed curve shape on the slope of the pixel portion. The bank pattern 112 defines an emission area and a non-emission area of the pixel portion, and is disposed on the substrate 100 on which the first electrode 111 of the pixel portion is formed. In this case, the bank pattern 112 may be disposed above and below the pixel portion to correspond to a boundary region between the driver and the pixel portion.

A single-layer or multi-layer organic light-emitting layer 114 is disposed on the first electrode 111 on which the bank pattern 112 is not disposed. The organic light emitting layer 114 may be formed using a solvent.

When the organic light-emitting layer is formed using a solvent for forming the organic light-emitting layer, the concentration of the organic light-emitting material contained in the solvent for forming the organic light-emitting layer should be secured at a certain level or higher in order to secure the characteristics of the organic light-emitting device.

Here, the organic light-emitting material becomes a factor that increases the viscosity of the solvent for forming the organic light-emitting layer. In particular, as the molecular weight of the organic light-emitting material increases, the viscosity of the solvent for forming the organic light-emitting layer increases rapidly. For this reason, a problem arises in that it is difficult to discharge the solvent for forming an organic light-emitting layer.

To solve this, the organic light-emitting layer 114 according to the present invention is formed through a solvent for forming an organic light-emitting layer including a first solvent and a second solvent. In this case, the solvent for forming the organic emission layer includes a solvent for lowering the viscosity of the solvent for forming the organic emission layer.

Specifically, the first solvent includes a first composition and a second composition containing an aromatic ester, an aromatic ether, an aromatic hydrocarbon or an aromatic ketone. Specifically, the first solvent is a first composition containing one selected from the group consisting of an aromatic ester, an aromatic ether, an aromatic hydrocarbon, an aromatic ketone, etc. Includes. In addition, the first solvent includes a second composition containing one selected from the group consisting of an aromatic ester, an aromatic ether, an aromatic hydrocarbon, an aromatic ketone, etc. do. In addition, the second solvent includes an aromatic ether.

Here, the second solvent has a lower boiling point than the first solvent. Specifically, the boiling point of the first solvent is 230 ^o C to 330 ^o C, and the boiling point of the second solvent is 110 ^o C to 230 ^o C. In addition, the viscosity of the second solvent is lower than that of the first solvent. Specifically, the viscosity of the first solvent is 3 cPs to 10 cPs, and the viscosity of the second solvent is 1.5 cPs or less.

Since the solvent for forming the organic light-emitting layer includes a first solvent and a second solvent, the organic light-emitting material has high solubility and low viscosity. Specifically, since the solvent for forming the organic light-emitting layer includes a first solvent including the first composition and the second composition, the solubility of the organic light-emitting material can be increased, and high flatness of the organic light-emitting layer 114 can be secured. I can. In addition, since the solvent for forming the organic light-emitting layer includes a second solvent having a lower boiling point and viscosity than the first solvent, the viscosity of the solvent for forming the organic light-emitting layer may be lowered.

When the solvent for forming an organic light-emitting layer has a characteristic of low viscosity, it becomes easy to discharge the solvent for forming an organic light-emitting layer. When the low-viscosity organic light-emitting layer-forming solvent is discharged onto the first electrode 111, the second solvent of the discharged organic light-emitting layer-forming solvent is rapidly evaporated due to its low boiling point. In addition, since the solvent for forming the organic emission layer includes the first solvent, the organic emission layer 114 formed through the solvent for forming the organic emission layer may have a high flatness.

Since the solvent for forming an organic light-emitting layer used in the organic light-emitting display device according to the present invention includes a first solvent and a second solvent, the organic light-emitting material has high solubility and low viscosity. Through this, the solvent for forming the organic light-emitting layer may contain a high-concentration organic light-emitting material. In addition, even when the solvent for forming the organic light-emitting layer contains a high-concentration organic light-emitting material, since it has a low viscosity, the solvent for forming the organic light-emitting layer can be easily discharged. This will be described with reference to FIG. 2, which is a cross-sectional view taken along line II′.

2 is a diagram illustrating a cross-sectional view taken along line II′ of the organic light emitting display device of the present invention. Referring to FIG. 2, a semiconductor layer 101 is disposed on a substrate 100. The semiconductor layer 101 includes a source region 101a, a channel region 101b, and a drain region 101c. A gate insulating layer 104 is disposed on the semiconductor layer.

A gate electrode 105 is disposed on the gate insulating layer 104. The gate electrode 105 may be an alloy formed from Cu, Ag, Al, Cr, Ti, Ta, Mo, or a combination thereof. In addition, although it is formed as a single metal layer in the drawing, it may be formed by stacking at least two or more metal layers in some cases.

An interlayer insulating layer 106 is disposed on the gate electrode 105. A contact hole is formed in the interlayer insulating layer 106 and the gate insulating layer 104 to expose the source region 101a and the drain region 101c.

Thereafter, a source electrode 107 and a drain electrode 108 are formed on a portion of the contact hole and the upper surface of the interlayer insulating layer 106 to be spaced apart from each other. The source electrode 107 and the drain electrode 108 are connected to the source region 101a and the drain region 101c of the semiconductor layer 101 through the contact hole.

Here, the source electrode 107 and the drain electrode 108 may be an alloy formed from Cu, Ag, Al, Cr, Ti, Ta, Mo, or a combination thereof. In addition, although the source electrode 107 and the drain electrode 108 are formed of a single metal layer in the drawing, in some cases, at least two or more metal layers may be stacked to form a layer.

In this way, the thin film transistor Tr is formed on the substrate 100. Here, a plurality of thin film transistors Tr may be formed on the substrate 100 to be spaced apart from each other. In addition, the data line 10 is disposed on the same layer as the source electrode 107 and the drain electrode 108.

A protective layer 109 and a planarization layer 110 are disposed on the substrate 100 including the thin film transistor Tr and the data line 10. A contact hole exposing the drain electrode 108 of the thin film transistor Tr is formed in the passivation layer 109 and the planarization layer 110.

A first electrode 111 of an organic light emitting diode is disposed on the contact hole and a part of the top surface of the planarization layer 110. The first electrode 111 may serve to supply holes to the organic emission layer 114 of the organic electroluminescent device.

In addition, a bank pattern 112 exposing a part of the upper surface of the first electrode 111 is disposed. In addition, an organic emission layer 114 is disposed on the first electrode 111 exposed by the bank pattern 112. The organic light emitting layer 114 may be formed using a solvent.

In this case, the solvent for forming the organic light-emitting layer used to form the organic light-emitting layer 114 may include a first solvent and a second solvent. In this case, the first solvent includes a first composition and a second composition containing an aromatic ester, an aromatic ether, an aromatic hydrocarbon, or an aromatic ketone.

In detail, the first solvent is a first composition containing one selected from the group consisting of an aromatic ester, an aromatic ether, an aromatic hydrocarbon, an aromatic ketone, etc. Includes. In addition, the first solvent includes a second composition containing one selected from the group consisting of an aromatic ester, an aromatic ether, an aromatic hydrocarbon, an aromatic ketone, etc. do. In addition, the second solvent includes an aromatic ether.

Here, the second solvent has a lower boiling point than the first solvent. Specifically, the boiling point of the first solvent is 230 ^o C to 330 ^o C, and the boiling point of the second solvent is 110 ^o C to 230 ^o C.

Here, when the boiling point of the first solvent is ^{less than 230 o} C, stains may occur due to a high drying speed of the solvent for forming an organic light emitting layer including the first solvent. In addition, when the boiling point of the first solvent ^{exceeds 330 o} C, the drying speed of the solvent for forming an organic light emitting layer including the first solvent may be too slow.

In addition, when the boiling point of the second solvent is ^{less than 110 o} C, it may be difficult to prepare a solvent for forming an organic light emitting layer including the second solvent due to rapid evaporation of the second solvent. In addition, when the boiling point of the second solvent ^{exceeds 230 o} C, stains may occur in the organic emission layer formed using the solvent for forming the organic emission layer.

In addition, the viscosity of the second solvent is lower than that of the first solvent. Specifically, the viscosity of the first solvent is 3 cPs to 10 cPs, and the viscosity of the second solvent is 1.5 cPs or less.

Here, when the viscosity of the first solvent is less than 3 cPs, the solubility of the organic light emitting material may decrease. In addition, when the viscosity of the solvent exceeds 10 cPs, it may be difficult to discharge the solvent for forming the organic light emitting layer. In addition, when the viscosity of the second solvent exceeds 1.5, the viscosity of the solvent for forming the organic light-emitting layer increases, so that it may be difficult to discharge the solvent for forming the organic light-emitting layer.

Since the solvent for forming the organic light-emitting layer has a low viscosity characteristic due to the second solvent, the solvent for forming the organic light-emitting layer can be easily discharged. When the solvent for forming an organic light emitting layer having a low viscosity is discharged onto the first electrode 111, the second solvent of the solvent for forming an organic light emitting layer is rapidly evaporated due to a low boiling point. Accordingly, the second solvent lowers the viscosity of the solvent for forming the organic light-emitting layer, and does not affect the flatness of the organic light-emitting layer 114 formed by rapidly evaporating after discharge.

Accordingly, the flatness of the organic light-emitting layer 114 formed through the solvent for forming the organic light-emitting layer is determined by the first solvent. In detail, since the solvent for forming the organic emission layer includes the first solvent, the organic emission layer 114 formed through the solvent for forming the organic emission layer may have a high flatness. That is, when the organic light-emitting layer 114 is formed using the organic light-emitting layer forming solvent, a difference between the thickness of the central part of the organic light-emitting layer 114 and the thickness of the outer part of the organic light-emitting layer 114 can be reduced.

The solvent for forming the organic light emitting layer includes 35 vol% to 85 vol% of the first composition of the first solvent, 5 vol% to 45 vol% of the second composition of the second solvent, and the second It may contain 10 vol% to 30 vol% of the solvent. In this case, the vol% of each of the first composition and the second composition of the first solvent may be determined according to the flatness characteristic of the organic light-emitting layer.

Here, when the first composition of the first solvent, the second composition, and the second solvent are combined, it may be 100 vol%. That is, when 35 vol% of the first composition of the first solvent and 35 vol% of the second composition are included in the solvent for forming the organic light emitting layer, the second solvent may contain 30 vol%.

In this case, when the first composition of the first solvent is included in the solvent for forming the organic light-emitting layer in less than 35 vol% or more than 85 vol%, the solubility of the organic light-emitting material may decrease or the flatness of the organic light-emitting layer may decrease. In addition, when the second composition of the first solvent is included in the solvent for forming the organic light-emitting layer in less than 5 vol% or more than 45 vol%, the solubility of the organic light-emitting material may decrease or the flatness of the organic light-emitting layer may decrease. In addition, when the second solvent is included in less than 10 vol% of the solvent for forming the organic emission layer, the viscosity of the solvent for forming the organic emission layer may not be lowered. In addition, when the second solvent is contained in an amount exceeding 30 vol% in the solvent for forming the organic light emitting layer, the flatness of the organic light emitting layer may decrease.

The second electrode 120 of the organic light emitting device is disposed on the substrate 100 including the organic light emitting layer 114. The second electrode 120 may serve to supply electrons to the organic emission layer 114.

A second substrate 151 may be disposed facing the first substrate 100 on which the second electrode 120 is formed. In addition, the first substrate 100 and the second substrate 151 may be bonded together using a bonding agent. Here, the bonding agent may be a photocurable resin or a thermosetting resin, and the spaced space 113 between the bonded first and second substrates 100 and 151 may be filled with air, nitrogen, or a bonding agent.

Since the solvent for forming an organic light-emitting layer used in the organic light-emitting display device according to the present invention includes a first solvent and a second solvent, the organic light-emitting material has high solubility and low viscosity. Through this, the solvent for forming the organic light-emitting layer may contain a high-concentration organic light-emitting material. In addition, even when the solvent for forming the organic light-emitting layer contains a high-concentration organic light-emitting material, since it has a low viscosity, the solvent for forming the organic light-emitting layer can be easily discharged.

Hereinafter, it will be described in more detail using Examples and Comparative Examples of the present invention. However, the following Examples and Comparative Examples are for illustrating the present invention, and the present invention is not limited to the following Examples and Comparative Examples, and may be variously modified and changed.

<Examples 1 to 2 and Comparative Examples 1 to 4>

Each component was mixed with the component contents shown in Table 1 to prepare a solvent for forming an organic light emitting layer of Examples 1 to 2 and Comparative Examples 1 to 4 according to the present invention.

Example
And
Comparative example First solvent
(First composition) First solvent
(2nd composition) Second solvent Mixing ratio density
(wt%) Viscosity
(cPs) Example 1 CHB VP MA 35:35:30 One 11 Example 2 CHB MN MA 35:35:30 One 12 Comparative Example 1 CHB VP - 5:5 One 14 Comparative Example 2 CHB MN - 5:5 One 15 Comparative Example 3 CHB VP - 8:2 One 15 Comparative Example 4 CHB MN - 8:2 One 15

CHB: cyclohexyl benzene

MN: 1-methylnaphthalene

VP: valerophenone

MA: 4-methylanisole

As can be seen in Table 1, it can be seen that the solvents for forming an organic light emitting layer of Examples 1 to 2 according to the present invention have a lower viscosity than Comparative Examples 1 to 4. Through this, it can be confirmed that the viscosity of the solvent for forming the organic light emitting layer can be lowered by including the second solvent having a lower boiling point and viscosity than that of the first solvent.

<Organic light emitting layer flatness test>

In order to evaluate the effect of the solvent for forming an organic light-emitting layer according to the present invention, the solvent for forming the organic light-emitting layer of Example 1 and the solvent for forming the organic light-emitting layer of Comparative Example 1 were discharged onto a glass substrate. Thereafter, in order to form the organic light emitting layer, the glass substrate to which the solvent for forming the organic light emitting layer was discharged ^{was dried at 120°} C. for 1 hour using a hot-plate.

In order to check the flatness of the organic light-emitting layer after formation of the organic light-emitting layer through this process, the outer portion of the organic light-emitting layer is compared to the thickness of the central part of the organic light-emitting layer formed by the solvent for forming the organic light-emitting layer of Example and the solvent for forming the organic light-emitting layer of Comparative Example 1. The thickness was compared.

At this time, the thickness of the central portion and the outer portion of the organic light emitting layer was observed using a confocal microscope (Confocal Laser Scanning Microscopy, Keyence Corporation, VK-9500). Table 2 shows the experimental results.

Example
And
Comparative example Central thickness
(㎛) Outer shell thickness
(㎛) Outside thickness compared to center thickness Example 1 2 3.1 1.6 Comparative Example 1 1.3 2.2 1.7

As can be seen in Table 2, the flatness of the organic light-emitting layer using the solvent for forming the organic light-emitting layer of Example 1 according to the present invention is superior to the flatness of the organic light-emitting layer using the solvent for forming the organic light-emitting layer of Comparative Example 1. I can confirm.

The above results show that when the organic light-emitting layer of an organic light-emitting device is formed, when the solvent for forming the organic light-emitting layer of the present invention is used, a flat organic light-emitting layer can be formed.

10: data wiring 20: gate wiring
111: first electrode 112: bank pattern
114: organic light emitting layer

Claims (9)

A first substrate;
A passivation layer and a planarization layer disposed on the first substrate;
A first electrode disposed on upper surfaces of the passivation layer and the planarization layer;
A bank pattern disposed while exposing a portion of an upper surface of the first electrode;
An organic light emitting layer disposed on the first electrode exposed by the bank pattern;
A second electrode disposed on the organic emission layer while facing the first electrode;
A second substrate disposed on the second electrode while facing the first substrate; And
An organic light emitting display device comprising a space formed by bonding the first substrate and the second substrate,
The spaced space is filled with air, nitrogen or a bonding agent,
The first electrode supplies holes to the organic light emitting layer,
The second electrode supplies electrons to the organic light emitting layer,
The organic light-emitting layer is formed by using a solvent for forming an organic light-emitting layer, and the solvent includes a first solvent and a second solvent,
The first solvent includes a first composition and a second composition containing an aromatic ester, an aromatic ether, an aromatic hydrocarbon or an aromatic ketone,
The second solvent contains an aromatic ether,
The first composition of the first solvent contains 35 vol% to 85 vol%,
The second composition of the first solvent contains 5 vol% to 45 vol%,
The second solvent is characterized in that it contains 10 vol% to 30 vol%,
Organic light emitting display device.
The method of claim 1,
The organic light emitting display device, wherein the boiling point of the second solvent is lower than the boiling point of the first solvent.
The method of claim 2,
The boiling point of the first solvent is 230 ^o C to 330 ^o C,
The organic electroluminescent display device, wherein the boiling point of the second solvent is 110 ^o C to 230 ^{o C.}
The method of claim 1,
The organic electroluminescent display device, wherein the viscosity of the second solvent is lower than that of the first solvent.
The method of claim 4,
The viscosity of the first solvent is 3 cPs to 10 cPs,
The organic electroluminescent display device, wherein the viscosity of the second solvent is 1.5 cPs or less.
The method of claim 1,
The first solvent,
An organic electroluminescent display device comprising a benzoate series in the aromatic ester group and a benzyl group or two phenyl groups in the aromatic ether group.
delete delete The method of claim 1,
A thin film transistor is disposed on the first substrate,
The thin film transistor includes a gate electrode, a semiconductor layer, a source electrode and a drain electrode,
The first electrode is an organic light emitting display device, characterized in that connected to the drain electrode of the thin film transistor.

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