WO2012132853A1

WO2012132853A1 - Organic electroluminescent element

Info

Publication number: WO2012132853A1
Application number: PCT/JP2012/056255
Authority: WO
Inventors: 博之佐々木; 博也辻
Original assignee: パナソニック株式会社
Priority date: 2011-03-31
Filing date: 2012-03-12
Publication date: 2012-10-04
Also published as: JP2012212778A

Abstract

An organic electroluminescent element, in which color variation on a light emitting surface is suppressed, is provided. The organic electroluminescent element is provided with an organic layer (3) containing two or more dopant-containing layers (1), and one or more non-dopant-containing layers (2). The light emitting surface (A) is divided into blocks of a predetermined size representing a plurality of elements (S). In at least one of the of the dopant-containing layers (1) of the two or more dopant-containing layers (1), the average film thickness of each element (S) in said dopant-containing layer (1) is within a range of 90 to 110% of the overall average film thickness of said dopant-containing layer. The average chromaticity of each element represented by u' and v' values in the CIE 1976 (u', v') chromaticity diagram is within a range of 98 to 102% of the overall average chromaticity of the light emitting surface (A) for both the u' and v' values. For each element (S), the total film thickness of the two or more dopant-containing layers (1) is less than the total film thickness of the one or more non-dopant-containing layers (2).

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence element having a light emitting surface.

Recently, an organic EL element that emits light in a planar shape has been developed as an organic electroluminescence element (organic EL element) used in a lighting device or the like. When the light emission is planar, there is an advantage that the light emission area can be made larger than that emitted in a spot shape and the light can be emitted brightly. And the organic EL element which has such a light emission surface attracts attention as a next-generation light emitting element since it has characteristics such as low power and long life.

JP 2007-048732 A

In an organic EL element having a light emitting surface, there is a problem that uneven chromaticity and uneven brightness called color unevenness occur in the light emitting surface of a panel or the like. That is, there may be a difference in luminance and chromaticity between one region and another region in the light emitting surface, such as the central portion and the end portion, the corner portions, the one end portion and the other end portion. In particular, as the light emitting area becomes larger, luminance unevenness and chromaticity unevenness become more prominent. If the luminance unevenness or chromaticity unevenness is large, there is a problem that uniform light emission cannot be obtained in the surface and the light emission performance is deteriorated.

Patent Document 1 discloses a technique for adjusting a film thickness to suppress a dark spot, but does not improve chromaticity unevenness and luminance unevenness on a light emitting surface.

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an organic EL element in which color unevenness in a light emitting surface is suppressed.

An organic electroluminescence device according to the present invention includes an organic layer including two or more dopant-containing layers and one or more dopant-free layers, and the light-emitting surface is divided into a plurality of elements in a predetermined size section. Sometimes, in at least one of the two or more dopant-containing layers, the average film thickness of each element in the dopant-containing layer is in the range of 90 to 110% of the average film thickness of the entire dopant-containing layer. The average chromaticity of each element represented by the u ′ value and the v ′ value in the CIE 1976 (u ′, v ′) chromaticity diagram is the entire light emitting surface in both the u ′ value and the v ′ value. The total thickness of the two or more dopant-containing layers is more than the total thickness of the one or more dopant-free layers. Is also small.

In each of the above elements, the total thickness of the two or more dopant-containing layers is preferably 25 to 35% with respect to the thickness of the organic layer.

Each dopant-containing layer in the two or more dopant-containing layers has an average film thickness of each element in each dopant-containing layer within a range of 93 to 107% of an average film thickness of the entire dopant-containing layer, Each dopant non-containing layer in the one or more dopant non-containing layers has an average film thickness of each element in each of the dopant non-containing layers within a range of 90 to 110% of an average film thickness of each of the dopant non-containing layers. Preferably there is.

Further, a reflective electrode is provided adjacent to the organic layer, and the adjacent organic layer adjacent to the reflective electrode among the organic layers has a total film thickness of 30 to 50 nm, and each element in the adjacent organic layer The average film thickness is preferably in the range of 93 to 107% of the average film thickness of the entire adjacent organic layer.

It is preferable that the element showing the minimum luminance among the plurality of elements shows 70% or more of luminance with respect to the element showing the maximum luminance.

The organic layer is provided between a reflective electrode and a transparent electrode, and the transparent electrode is provided on the inner surface of a light-transmitting substrate having a light scattering layer provided on the outer surface, and CIE 1976 (u ′, v ′) In the chromaticity diagram, the average chromaticity of each element represented by the u ′ value and the v ′ value is 98.5 to 101.10 of the average chromaticity of the entire light emitting surface in both the u ′ value and the v ′ value. It is preferable to be within the range of 5%.

According to the present invention, it is possible to obtain an organic EL element in which color unevenness in the light emitting surface is suppressed and the in-plane uniformity of light emission is improved.

It is a schematic plan view which shows an example of the light emission surface of the organic EL element of this invention. It is a schematic sectional drawing which shows an example of the organic EL element of this invention. It is the schematic which shows an example of the film thickness adjustment in a vacuum evaporation method. It is the photograph of the light emission surface, and has shown the light emission surface of the organic EL element of Example 1. FIG. It is a photograph of the light emission surface, and shows the light emission surface of the organic EL element of Comparative Example 1.

FIG. 2 is an example of a layer configuration of the organic electroluminescence element (organic EL element) of the present embodiment. This organic EL element includes an organic layer 3 including two or more dopant-containing layers 1 and one or more dopant-free layers 2.

The organic layer 3 is disposed between the first electrode 4 and the second electrode 5. In the illustrated form, the dopant-containing layer 1 is composed of m dopant-containing layers 1, the dopant-containing layer 1 a is disposed closest to the first electrode 4 side, and the dopant-containing layer is closest to the second electrode 5 side. 1b is arranged. Note that m is a positive integer of 2 or more. The dopant non-containing layer 2 is composed of n dopant non-containing layers 2, the dopant non-containing layer 2 a is arranged on the most first electrode 4 side, and the dopant non-containing is most on the second electrode 5 side. Layer 2b is disposed. Note that n is a positive integer of 1 or more.

The dopant-containing layer 1 is a layer that contains a light-emitting dopant and functions as a light-emitting layer. The two or more dopant-containing layers 1 preferably include at least two dopant-containing layers 1 having different emission colors. Colors with different emission colors are likely to cause color unevenness, but in this embodiment, such color unevenness can be further reduced. Further, if there are a plurality of emission colors, particularly three or more emission colors, it is possible to create appropriate emission colors by combining red, blue and green emission, which is preferable. In this case, for example, white light emission can be obtained.

The dopant non-containing layer 2 is a layer not containing a light emitting dopant. The dopant-free layer 2 functions as an appropriate layer selected from an electron injection layer, an electron transport layer, a hole transport layer, a hole injection layer, an intermediate layer, a bonding layer, and the like. The dopant-free layer 2 is one of the layers constituting the organic layer 3 and is basically a layer containing an organic substance. In the present specification, the above-described layers such as an electron injection layer and an electron transport layer However, it is defined as the dopant non-containing layer 2 even when it is made of a metal or the like without containing organic substances. That is, the organic layer 3 refers to the entire layer sandwiched between the first electrode 4 and the second electrode 5.

The film thickness of the dopant-containing layer 1 can be set to 1 to 40 nm, for example. The film thickness of the dopant-free layer 2 can be set to 1 to 60 nm, for example. When the film thicknesses of these layers are in an appropriate range, both electrical specification and light emission characteristics can be improved.

FIG. 1 is a schematic plan view of the organic EL element as viewed from a direction perpendicular to the light emitting surface A. FIG. Light emitted by the organic layer 3 is extracted from the first electrode 4 side (or the second electrode 5 side) which is a light extraction electrode. As described above, the organic EL element of the present embodiment emits light in a planar shape, and the light emitting surface A is a planar shape having a relatively large area. Size of the light emitting surface A is, for example, may be an area to the extent 25 cm ² or more 900 cm ² or less, but is not limited thereto. The shape of the light emitting surface A is not particularly limited, and may be rectangular (square or rectangular), circular, or other shapes. However, the element division described below is easier to perform in the rectangular shape.

The light emitting surface A is divided into a plurality of elements S in sections of a predetermined size. In FIG. 1, the plurality of elements S are configured in a square shape in which each element S has the same area. The element S may have a rectangular shape, but is preferably a square shape from the viewpoint of reducing color unevenness. The light emitting surface A is divided into n elements S. Here, n is a positive integer. This n is not related to n in FIG.

The size of the element S can be appropriately set to a predetermined size. However, if the size of the element S is too large, gradients such as chromaticity and luminance within the element are averaged. There is a risk that the above will be evaluated as no gradient and will not reflect the actual situation. In addition, when used as a surface light source with a large area, what is required is uniformity of the entire surface (chromaticity, brightness, etc.), and uniformity between the minimum areas is not necessarily required, and is also unnecessary from the viewpoint of visibility. Therefore, it is not necessary to make the size of the element S too small. In this way, the size of the element S is set on the basis of the sensitivity given to the person by the light emission on the light emitting surface A.

The size of the element S can be, for example, a square of 5 mm × 5 mm, but is not limited thereto, and when configured in a square shape, for example, larger than a square of 0.2 mm × 0.2 mm, 30 mm × 30 mm It is preferably smaller than the square. The size of the element S is more preferably larger than a 1 mm × 1 mm square and smaller than a 10 mm × 10 mm square or a 20 mm × 20 mm square.

Further, the element S may be obtained by equally dividing the light emitting surface A by a predetermined number. For example, the light emitting surface A is divided into 3 × 3 (total 9) squares, divided into 4 × 4 (total 16) squares, or 5 × 5 (total 25). Or a plurality of elements S can be obtained.

In FIG. 1, p elements are arranged in the horizontal direction and q elements are arranged in the vertical direction. p and q are positive integers. Here, the element S of the upper left corner and the elements S _1, a laterally arranged elements in order from left to right of the stage (first stage), S _{2, S} _3, · · ·, as such S _p Define. Right this time, the vertical elements S of the left end of the next stage (second stage), as the next element S of S _p, if indicated as element S _{p + 1,} element arranged in the horizontal direction of the stage from the left , S _{P + 2} , S _{P + 3} ,..., S _2p in order. In this way, the arbitrary element S which is α-th in the horizontal direction and β-th in the vertical direction can be expressed as element S _m , m = (β−1) p + α. α and β are positive integers. This m is not related to m in FIG. Thus, when the elements in the horizontal direction and the vertical direction are numbered in order, the element S in the lower right corner can be expressed as element S _n , n = p × q. Thus, the light emitting surface A is divided into n elements S from the element S ₁ to the elements S _n.

In the organic EL element of this embodiment, when the element is divided in this way, at least one dopant-containing layer 1 out of two or more dopant-containing layers 1 satisfies a specific film thickness condition. The dopant-containing layer 1 that satisfies this specific film thickness condition will be described as a specific dopant-containing layer.

In the specific dopant-containing layer, the specific dopant-containing layer is divided into n elements S when viewed from the direction perpendicular to the light emitting surface A as described above. The average film thickness of the specific dopant-containing layer in each element S is in the range of 90 to 110% of the average film thickness of the entire specific dopant-containing layer.

Here, it represents the average thickness of a particular dopant-containing layer in any element S _m and D _Sm. Then, for example, the average thickness of a particular dopant-containing layer in the element S ₁ can be expressed as D _S1, the average thickness of a particular dopant-containing layer in the element S ₂ can be expressed as D _S2, the elements S _n The average film thickness of the specific dopant-containing layer can be expressed as _DSn .

Moreover, the average film thickness _{Dav of the} whole specific dopant content layer can be expressed as follows.

D _av = (D _S1 + D _S2 +... + D _Sn ) / n

And with respect to the average film thickness D _{av of the} entire specific dopant-containing layer, the average film thickness D _Sm of any element S _m selected from the n elements S satisfies the following relationship in all the elements S.

D _av × 0.9 ≦ D _Sm ≦ D _av × 1.1

This relationship
D _av × 0.9 ≦ D _S1 , D _S2 ,..., D _Sn ≦ D _av × 1.1
May be indicated.

Or
D _av × 0.9 ≦ D _{S1 to Sn} ≦ D _av × 1.1
May be indicated.

Thus, in the organic EL element of the present embodiment, the specific dopant-containing layer is designed to have a specific film thickness condition.

Further, the organic EL element of the present embodiment has the u ′ value and v ′ of the CIE 1976 (u ′, v ′) chromaticity diagram when the chromaticity of the light emitting surface A is measured from the direction perpendicular to the light emitting surface A. The average chromaticity of each element S represented by the value is within the range of 98 to 102% of the average chromaticity of the entire light emitting surface A in both the u ′ value and the v ′ value. Hereinafter, the u 'value of the CIE 1976 (u', v ') chromaticity diagram is referred to as CIE-u', and the v 'value of the CIE 1976 (u', v ') chromaticity diagram is referred to as CIE-v'.

Here, the average chromaticity of any element S _m can be expressed as follows.

(CIE-u ′, CIE-v ′) = (u ′ _m , v ′ _m )

Then, the average chromaticity of the element S ₁ is
(CIE-u ′, CIE-v ′) = (u ′ ₁ , v ′ ₁ )
Can be expressed as
Average chromaticity component _{S 2} is
(CIE-u ′, CIE-v ′) = (u ′ ₂ , v ′ ₂ )
Can be expressed as
Average chromaticity component _{S n} is
(CIE-u ′, CIE-v ′) = (u ′ _n , v ′ _n )
It can be expressed as.

Further, the average chromaticity of the entire light emitting surface A can be expressed as follows.

(CIE-u ′, CIE-v ′) = (u ′ ₀ , v ′ ₀ )
Where u ′ ₀ = (u ′ ₁ + u ′ ₂ +... + U ′ _n ) / n
v ′ ₀ = (v ′ ₁ + v ′ ₂ +... + v ′ _n ) / n
It is.

The average chromaticity (u ′ _m , v ′ _m ) of an arbitrary element S _m selected from the n elements S with respect to the average chromaticity (u ′ ₀ , v ′ ₀ ) of the entire light emitting surface A is The following relationship is satisfied in all elements S.

u ′ ₀ × 0.98 ≦ u ′ _m ≦ u ′ ₀ × 1.02
_{And, v '0 × 0.98 ≦ v} ' m ≦ v '0 × 1.02

This relationship
u ′ ₀ × 0.98 ≦ u ′ ₁ , u ′ ₂ ,..., u ′ _n ≦ u ′ ₀ × 1.02
And v ′ ₀ × 0.98 ≦ v ′ ₁ , v ′ ₂ ,..., V ′ _n ≦ v ′ ₀ × 1.02
May be indicated.

Or
u ′ ₀ × 0.98 ≦ u ′ _{1 to n} ≦ u ′ ₀ × 1.02
And v ′ ₀ × 0.98 ≦ v ′ _{1 to n} ≦ v ′ ₀ × 1.02
May be indicated.

That is, in both CIE-u ′ and CIE-v ′, the average chromaticity of each element S with respect to the entire light emitting surface A is within the above range.

The chromaticity is measured by, for example, a two-dimensional color luminance meter (CA-2000) manufactured by Konica Minolta.

Thus, the organic EL element of the present embodiment is designed so that the average chromaticity of the light emitting surface A is in a specific condition.

As described above, the specific dopant-containing layer has a specific film thickness condition, and the average chromaticity of the light-emitting surface A is a specific condition, so that the in-plane light emission can be made closer to uniform, and the color unevenness Is suppressed, and an excellent planar light-emitting organic EL device can be constructed.

The specific dopant-containing layer may be at least one dopant-containing layer 1 out of two or more dopant-containing layers 1, but preferably two or more, more preferably three or more dopant-containing layers 1 are specific dopant-containing layers. It will be. When some dopant content layers 1 are specific dopant content layers, it is preferred that dopant content layer 1 with high contribution in the whole luminescent color is a specific dopant content layer. For example, when graphing the relationship between the emission wavelength and the emission intensity, the dopant-containing layer 1 having a high intensity peak is preferably a specific dopant-containing layer. By setting the dopant-containing layer 1 having high emission intensity to a specific film thickness condition, color unevenness can be effectively reduced. And it is preferable that all the dopant content layers 1 in the organic layer 3 become a specific dopant content layer. When all the dopant-containing layers 1 have specific film thickness conditions, color unevenness can be further suppressed.

In the organic EL element, each element S is such that the total thickness of the two or more dopant-containing layers 1 is thinner than the total thickness of the one or more dopant-free layers 2. The total thickness of the film thickness is a total thickness obtained by adding the thicknesses of the individual layers when a plurality of layers (dopant-containing layer 1 or non-dopant-containing layer 2) are present in the organic layer 3. The total thickness is calculated by the sum of the average thickness of each element in each layer.

As shown in FIG. 2, in the organic EL element, the dopant-containing layer 1 has a film thickness D. Here, the film thicknesses are defined as D ₁ , D ₂ ,..., D _{m in} order from the dopant-containing layer 1 on the first electrode 4 side. Then, the total thickness of the dopant-containing layer 1 can be expressed as follows.

T _D = D ₁ + D ₂ +... + D _m

Also, in order from the dopant-free layer 2 of the first electrode 4 side, the film _thickness, d _1, d 2, · · ·, defined as _{d n.} Then, the total thickness of the dopant non-containing layer 2 can be expressed as follows.

_{_{_{T d = d 1 + d 2}}} + ··· + d n

At this time, in the organic EL element, it is preferable that all the individual elements S satisfy the following relationship.

T _d > T _D

If the above relationship is satisfied, color unevenness is further suppressed.

Furthermore, in each element S, the total thickness of the two or more dopant-containing layers 1 is preferably 25 to 35% with respect to the thickness of the organic layer 3.

The film thickness T _all of the organic layer 3 is the sum of the total thickness of the dopant-containing layer 1 and the total thickness of the non-dopant-containing layer 2. That is,
T _all = T _D + T _d
It becomes the relationship.

0.25 × T _all ≦ T _D ≦ 0.35 × T _all

If the above relationship is satisfied, color unevenness is further suppressed.

In the organic EL element, each of the dopant-containing layers 1 in the two or more dopant-containing layers 1 has an average film thickness of each element S in each of the dopant-containing layers 1 and an average film thickness of each of the dopant-containing layers 1 as a whole. Preferably, it is within the range of 93 to 107%. That is, in a preferable form, when the element is divided, all the dopant-containing layers 1 of the two or more dopant-containing layers 1 satisfy a specific film thickness condition. In other words, all of the dopant-containing layers 1a, ..., 1b in the organic layer 3 satisfy a specific film thickness condition.

In each dopant-containing layer 1, the dopant-containing layer 1 is divided into n elements S when viewed from the direction perpendicular to the light emitting surface A as described above. The average film thickness of each dopant-containing layer 1 in each element S is in the range of 93 to 107% of the average film thickness of the entire dopant-containing layer 1 to which the element S belongs.

Here, as in the case described above, if indicated an average film thickness of the dopant-containing layer 1 in any element _{S m} and _{D Sm,} each element _S _1, S 2, · · ·, the dopant-containing layer 1 in the _{S n} The average film thickness can be expressed as D _S1 , D _S2 ,..., D _Sn , respectively.

Further, the average film thickness D _{av of the} entire individual dopant-containing layer 1 can be expressed as follows.

D _av = (D _S1 + D _S2 +... + D _Sn ) / n

The average film thickness D _Sm of any element S _m selected from the n elements S satisfies the following relationship in all the elements S with respect to the average film thickness D _{av of the} entire individual dopant-containing layer 1. .

D _av × 0.93 ≦ D _Sm ≦ D _av × 1.07

This relationship may be shown as follows.

D _av × 0.93 ≦ D _S1 , D _S2 ,..., D _Sn ≦ D _av × 1.07
May be indicated.

Or
D _av × 0.93 ≦ D _{S1 to Sn} ≦ D _av × 1.07
May be indicated.

Thus, in a preferable form of the organic EL element, all the dopant-containing layers 1 are designed to have a specific film thickness condition. In that case, color unevenness is further suppressed.

Moreover, each dopant non-containing layer 2 in the one or more dopant non-containing layers 2 is such that the average film thickness of each element S in each of the dopant non-containing layers 2 is 90 of the average film thickness of each of the dopant non-containing layers 2 as a whole. It is preferably in the range of ~ 110%. That is, in a preferable embodiment, when the element is divided, all the dopant-free layers 2 of the one or more dopant-free layers 2 satisfy a specific film thickness condition. In other words, the dopant-free layers 1a,..., 1b in the organic layer 3 all satisfy a specific film thickness condition.

In each dopant non-containing layer 2, the dopant non-containing layer 2 is divided into n elements S when viewed from the direction perpendicular to the light emitting surface A as described above. The average film thickness of the individual dopant-free layer 2 in each element S is in the range of 90 to 110% of the average film thickness of the entire dopant-free layer 2 to which it belongs.

Here, as in the case described above, if indicated an average film thickness of the dopant-free layer 2 at an arbitrary element _{S m} and _{d Sm,} each element _S _1, S 2, · · ·, dopants in _{S n-free} layer 2 can be expressed as d _S1 , d _S2 ,..., D _Sn , respectively.

Moreover, the average film thickness _dav of each individual dopant non-containing layer 2 can be expressed as follows.

d _av = (d _S1 + d _S2 +... + d _Sn ) / n

Then, the average thickness d _av of the entire non-dopant-containing layer 2, an average thickness d _Sm of n for any chosen from the elements S component S _m is satisfied in all the elements S the following relation.

d _av × 0.9 ≦ D _Sm ≦ D _av × 1.1

Or
d _av × 0.9 ≦ d _{S1 to Sn} ≦ d _av × 1.1
May be indicated.

Thus, in a preferable form of the organic EL element, all the dopant-free layers 2 are designed to have a specific film thickness condition. In that case, color unevenness is further suppressed.

In the organic EL element, it is preferable that one of the electrodes is formed as a transparent electrode and the other electrode is formed as a reflective electrode. Thereby, light can be reflected in a reflective electrode, and the direct light and reflected light of a light emitting layer can be taken out from a transparent electrode. A transparent electrode is an electrode that transmits light. A reflective electrode is an electrode having a function of reflecting light. In the form of FIG. 2, for example, the first electrode 4 is a transparent electrode and the second electrode 5 is a reflective electrode.

At this time, the adjacent organic layer 3a adjacent to the reflective electrode in the organic layer 3 has a total film thickness of 30 to 50 nm, and the average film thickness of each element S in the adjacent organic layer 3a is equal to the adjacent organic layer. It is preferably in the range of 93 to 107% of the average film thickness of the entire 3a. Thereby, color unevenness is further suppressed.

In the form of FIG. 2, the adjacent organic layer 3 a adjacent to the reflective electrode (second electrode 5) in the organic layer 3 is not included in the dopant non-containing layer 2 and is located closest to the second electrode 5. Layer 2b. In a preferred embodiment, the film thickness of the dopant-free layer 2b is 30 to 50 nm.

Then, as in the case described above, if indicated an average film thickness of the dopant-free layer 2b at an arbitrary element _{S m} and _{d Sm,} each element _S _1, S 2, · · ·, dopants in _{S n-free} layer 2b Can be expressed as d _S1 , d _S2 ,..., D _Sn , respectively.

Moreover, the average film thickness _dav of each individual dopant non-containing layer 2b can be expressed as follows.

d _av = (d _S1 + d _S2 +... + d _Sn ) / n

Then, the average thickness d _av of the entire non-dopant-containing layer 2b, the average thickness d _Sm of n for any chosen from the elements S component S _m is satisfied in all the elements S the following relation.

d _av × 0.93 ≦ D _Sm ≦ D _av × 1.07

This relationship
d _av × 0.93 ≦ d _S1 , d _S2 ,..., d _Sn ≦ d _av × 1.07
May be indicated.

Or
d _av × 0.93 ≦ d _{S1 to Sn} ≦ d _av × 1.07
May be indicated.

Thus, in a more preferable form of the organic EL element, the dopant non-containing layer 2b which is a layer adjacent to the reflective electrode is designed to have a specific film thickness condition. In that case, color unevenness is further suppressed.

In addition, the layer in contact with each electrode in the organic layer 3 may be the dopant-containing layer 1, but is preferably the dopant-free layer 2. In particular, the adjacent organic layer 3 a that is a layer adjacent to the reflective electrode is preferably the dopant-free layer 2. This facilitates injection of charges (electrons or holes) into the light-emitting layer, and can improve light-emitting properties.

In the organic EL element, when the luminance is measured in a direction perpendicular to the light emitting surface A, the element S indicating the minimum luminance among the plurality of elements S indicates 70% or more luminance with respect to the element S indicating the maximum luminance. Is preferred. The luminance at each element S is measured as the average luminance of the segment range of element S.

Here, according to the case described above, it represents the average luminance for arbitrary elements S _m and L _Sm. Then, each element _S _1, S 2, · · ·, average luminance for _{S n,} _{respectively,} L _S1, L S2, · · _·, can be expressed as _{L Sn.} Of the n elements S, the average luminance of the element S having the highest luminance is expressed as L _max, and the average luminance of the element S having the lowest luminance is expressed as L _min . Then, in the preferred embodiment, the following relationship is satisfied.

L _min ≧ L _max × 0.70

As described above, in a more preferable form of the organic EL element, the luminance of the light emitting surface A approaches uniformly and color unevenness is further suppressed.

The luminance is measured, for example, with a two-dimensional color luminance meter (CA-2000) manufactured by Konica Minolta.

In the organic EL element, when one of the electrodes is formed as a transparent electrode and the other electrode is formed as a reflective electrode, the transparent electrode has an inner surface of a light-transmitting substrate provided with a light scattering layer on the outer surface (back surface). It is preferably provided on the (surface). Thereby, the extracted light is scattered and color unevenness is suppressed.

For example, in the embodiment of FIG. 2, if the first electrode 4 is a transparent electrode and the second electrode 5 is a reflective electrode, the first electrode 4 is formed on the surface of the light transmissive substrate. That is, in the form as shown in FIG. 2, the entire layer of the organic EL element composed of the two electrodes and the organic layer 3 is formed on the surface of the light-transmitting substrate. A light scattering layer is provided on the surface of the light transmissive substrate opposite to the first electrode 4. Thus, the emitted light passes through the light transmissive electrode and the light scattering layer and is emitted from the element. At this time, the emitted light is scattered by the light scattering layer. The light transmissive electrode is not particularly limited as long as it transmits light and is preferably transparent, but may be translucent.

The average chromaticity of each element S represented by CIE-u ′ and CIE-v ′ is 98.5 to about the average chromaticity of the entire light emitting surface A in both CIE-u ′ and CIE-v ′. It is preferable to be within the range of 101.5%. That is, the average chromaticity (u ′ _m , v ′ _m ) of an arbitrary element S _m selected from the n elements S with respect to the average chromaticity (u ′ ₀ , v ′ ₀ ) of the entire light emitting surface A is The following relationship is preferably satisfied in all the elements S.

u ′ ₀ × 0.985 ≦ u ′ _m ≦ u ′ ₀ × 1.015
And v ′ ₀ × 0.985 ≦ v ′ _m ≦ v ′ ₀ × 1.015

This relationship
u ′ ₀ × 0.985 ≦ u ′ ₁ , u ′ ₂ ,..., u ′ _n ≦ u ′ ₀ × 1.015
And v ′ ₀ × 0.985 ≦ v ′ ₁ , v ′ ₂ ,..., V ′ _n ≦ v ′ ₀ × 1.015
May be indicated.

Or
u ′ ₀ × 0.985 ≦ u ′ _{1 to n} ≦ u ′ ₀ × 1.015
And v ′ ₀ × 0.985 ≦ v ′ _{1 to n} ≦ v ′ ₀ × 1.015
May be indicated.

Thus, the organic EL element is preferably designed so that the average chromaticity of the light emitting surface A is in a specific condition. Thereby, in-plane light emission can be made more uniform, color unevenness can be suppressed, and an excellent planar light-emitting organic EL element can be constructed.

The material constituting the organic EL element and the production of the organic EL element will be described.

The first electrode 4 and the second electrode 5 are formed using an appropriate conductive material. Thereby, the 1st electrode 4 and the 2nd electrode 5 are formed as a transparent electrode or a reflective electrode.

The material for the transparent electrode is not limited, but includes, for example, ITO, tin oxide, zinc oxide, IZO (IndiumZinc Oxide), copper iodide, conductive polymers such as PEDOT and polyaniline, and arbitrary acceptors. And conductive light-transmitting materials such as carbon nanotubes and the like.

Examples of the material of the reflective electrode include, but are not limited to, aluminum, silver, magnesium, gold, copper, chromium, molybdenum, palladium, tin, and alloys of these with other metals, such as magnesium Examples thereof include a silver mixture, a magnesium-indium mixture, and an aluminum-lithium alloy. Moreover, it consists of a metal, a metal oxide, etc., and a mixture of these and other metals, for example, an ultra-thin film made of aluminum oxide (here, a thin film of 1 nm or less capable of flowing electrons by tunnel injection) and aluminum. A laminated film with a thin film can be used.

The dopant-containing layer 1 is formed including a dopant compound and a host material containing the dopant compound.

The dopant compound is not limited, but, for example, a fluorescent light emitting dopant or a phosphorescent light emitting dopant can be used as appropriate. Since the phosphorescent dopant emits light from the triplet state, it has a luminous efficiency approximately four times higher than that of the fluorescent dopant that emits light only from the singlet state, and ideally has an internal quantum efficiency of 100%. High efficiency light emission becomes possible. Examples of the fluorescent light-emitting dopant include TBP (1-tert-butyl-perylene), BCzVBi, perylene, C545T (coumarin C545T; 10-2- (benzothiazolyl) -2,3,6,7-tetrahydro-1,1 , 7,7-tetramethyl-1H, 5H, 11H- (1) benzopyrrolopyrano (6,7, -8-ij) quinolidin-11-one)), DMQA, coumarin6, rubrene, and the like. Is not to be done. Examples of phosphorescent dopants include Ir (ppy) 3 (factory (2-phenylpyridine) iridium), Ir (ppy) 2 (acac), Ir (mppy) 3, Btp2Ir (acac) (bis- (3 -(2- (2-pyridyl) benzothienyl) mono-acetylacetonate) iridium (III))), Bt2Ir (acac), PtOEP, and the like, but are not limited thereto. In order to obtain white light emission, these dopants may be appropriately combined.

The host material is not limited, and for example, any of an electron transporting material, a hole transporting material, and a material having both electron transporting property and hole transporting property can be used. As the host material, an electron transporting material and a hole transporting material may be used in combination. Examples of the host material include Alq ₃ (tris (8-oxoquinoline) aluminum (III)), TBADN (2-tert-butyl-9,10-di (2-naphthyl) anthracene), ADN, BDAF, CBP, CzTT, TCTA, mCP, CDBP and the like can be mentioned.

The dopant non-containing layer 2 is formed of an electron injecting material, an electron transporting material, a hole transporting material, a hole injecting material, or the like according to the purpose.

Examples of the electron injecting material and the electron transporting material include, but are not limited to, Alq3, oxadiazole derivatives, starburst oxadiazoles, triazole derivatives, phenylquinoxaline derivatives, silole derivatives, and the like. Specific examples of the electron transporting material include fluorene, bathophenanthroline, bathocuproine, anthraquinodimethane, diphenoquinone, oxazole, oxadiazole, triazole, imidazole, anthraquinodimethane, 4,4′-N, N′-dicarbazole. Biphenyl (CBP) and the like, compounds thereof, metal complex compounds, nitrogen-containing five-membered ring derivatives and the like can be mentioned. Specific examples of the metal complex compound include tris (8-hydroxyquinolinato) aluminum, tri (2-methyl-8-hydroxyquinolinato) aluminum, tris (8-hydroxyquinolinato) gallium, bis ( 10-hydroxybenzo [h] quinolinato) beryllium, bis (10-hydroxybenzo [h] quinolinato) zinc, bis (2-methyl-8-quinolinato) (o-cresolate) gallium, bis (2-methyl-8-quinolinato) ) (1-naphtholato) aluminum, bis (2-methyl-8-quinolinato) -4-phenylphenolate and the like, but are not limited thereto. As the nitrogen-containing five-membered ring derivative, oxazole, thiazole, oxadiazole, thiadiazole, triazole derivatives and the like are preferable. Specifically, 2,5-bis (1-phenyl) -1,3,4-oxazole, 2 , 5-bis (1-phenyl) -1,3,4-thiazole, 2,5-bis (1-phenyl) -1,3,4-oxadiazole, 2- (4′-tert-butylphenyl) -5- (4 ″ -biphenyl) 1,3,4-oxadiazole, 2,5-bis (1-naphthyl) -1,3,4-oxadiazole, 1,4-bis [2- (5 -Phenylthiadiazolyl)] benzene, 2,5-bis (1-naphthyl) -1,3,4-triazole, 3- (4-biphenylyl) -4-phenyl-5- (4-t-butylphenyl) ) -1,2,4-Triazo Or the like can be mentioned Le.

The hole transporting material and the hole injecting material are not limited, and examples thereof include polyaniline, 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD). ), N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD), 2-TNATA, 4,4 ′, 4 ″ -tris (N— (3-methylphenyl) N-phenylamino) triphenylamine (MTDATA), 4,4′-N, N′-dicarbazole biphenyl (CBP), spiro-NPD, spiro-TPD, spiro-TAD, TNB, etc. Representative examples include triarylamine compounds, amine compounds containing carbazole groups, amine compounds containing fluorene derivatives, starburst amines (m-MTDATA), TDA 1-TMATA, 2-TNATA as an A-based materials, p-PMTDATA, and the like TFATA.

Then, an organic EL element having a layer structure as shown in FIG. 2 can be manufactured by sequentially forming and stacking the above materials in an appropriate order by an appropriate method.

The film thickness of each electrode can be about 10 to 300 nm, for example. The total film thickness of the organic layer 3 can be, for example, about 60 to 300 nm.

The film forming method is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, and a coating method.

Here, it is preferable to form the film so that the in-plane thicknesses of the layers approach uniformly so as to satisfy the film thickness conditions as described above. For example, in the vacuum deposition method, the thickness variation can be reduced by appropriately adjusting the evaporation source angle, the distance between the substrate and the evaporation source (height), the distance between the substrate rotation center and the evaporation source (offset), and the like. And a layer having a desired film thickness condition can be obtained.

FIG. 3 is a schematic view showing an example of film thickness adjustment in the vacuum deposition method.

When a material is stacked on the substrate 11 by vapor deposition, the substrate 11 is horizontally rotated around a rotation center C that is an axis perpendicular to the surface of the substrate 11. Then, the material is evaporated from the vapor deposition source 12 toward the substrate 11. At this time, the distance in the vertical direction between the emission port 12a of the evaporation source 12 from which the material is emitted and the substrate 11 is the distance (height) H between the substrate and the evaporation source. Further, the horizontal distance between the emission port 12a of the evaporation source 12 and the rotation center C is the distance (offset) δ between the substrate rotation center and the evaporation source. Further, the emission direction of the evaporation source 12 may form a predetermined angle from the vertical direction, and the angle formed by the emission direction of the evaporation source 12 and the vertical direction becomes the evaporation source angle θ. Note that the emission direction of the evaporation source 12 is preferably directed upward from the intersection of the rotation center C and the surface of the substrate 11. As described above, by appropriately setting the evaporation source angle θ, the substrate-evaporation source distance H, and the substrate rotation center-evaporation source distance δ, a layer having a small thickness variation is formed on the surface of the substrate 11. be able to.

The design logic for the organic EL element as described above will be described. Of course, the present invention is not limited by this logic.

The organic EL element has different light emission characteristics depending on the electrical / optical design. Here, the following three were considered as factors of color unevenness on the light emitting surface A, that is, luminance unevenness and chromaticity unevenness. These three are all due to in-plane variations in the light emitting surface A.
(1) Voltage variation.
(2) Variation in film thickness of each layer.
(3) Variation in temperature distribution.

In the organic EL element of the present embodiment, the element was designed by paying attention to the above (2).

Organic EL elements are roughly classified into high-molecular EL elements and low-molecular EL elements, and the former is generally manufactured by a coating process and the latter by a vapor deposition process. In addition, a hybrid element structure has been proposed in which a high molecular material is formed by a coating process and a low molecular material is formed by a vapor deposition process. Regardless of which process is used, uniform film formation within the panel is difficult (film thickness / concentration), which causes variations in the characteristics of the in-plane organic EL elements. In an organic EL element such as a display, it is relatively possible to reduce the influence of the characteristic variation of the organic EL element of each pixel by compensation in a drive circuit. On the other hand, organic EL elements such as lighting are required to emit light in a single area with a large area. For this reason, it is impossible to compensate for the in-plane characteristic variation, causing a deterioration in quality.

It is conceivable that the electrical characteristics and optical characteristics change between a certain part and another part in the plane due to variations in the film thickness of each layer in the organic EL element (changes in one layer). In particular, in an organic EL element, optical characteristics are governed by an index called an optical film thickness (n × d) obtained by multiplying a film thickness d and a refractive index n. The film thickness nd is greatly affected. In addition, the organic EL element which is a charge injection type element is greatly affected in light emission characteristics by changing the injection / transport state of charges (holes, electrons) due to a change in the physical film thickness d. The film thickness governing such electrical characteristics and optical characteristics is set by the management width setting by the robust design.

The organic EL element is formed by stacking multilayer films, and each layer dominates the light emission characteristics through interaction. Thus, each layer has an interaction, and the light emission characteristic and the characteristic influence of each layer cannot be clearly defined on a one-to-one basis. However, although the layers cannot be considered separately because of the interaction between the layers, it has been found that there is a clear difference in the degree of contribution that each layer affects the characteristics.

Therefore, the element design described above was performed as an element structure that reduces the influence of in-plane variation. That is, conditions such as the film thickness are defined for a layer having a greater contribution to the optical characteristics and electrical characteristics. For example, the dopant-containing layer 1 that directly participates in light emission has a higher contribution to light emission than the dopant-free layer 2. Moreover, in the organic layer 3, the contribution degree of the adjacent organic layer 3a adjacent to a reflective electrode is larger than another layer. Thus, the organic EL element of this embodiment is completed, and thereby the in-plane uniformity of light emission is improved.

(Layer configuration example 1)
The laminated materials are shown in the order of lamination.
-Light transmissive substrate: alkali-free glass, thickness 0.7 mm.
First electrode 4 (transparent electrode): ITO, film thickness 110 nm.
Hole transport layer (dopant non-containing layer 1): triphenylamine derivative, film thickness 60 nm.
First light emitting layer (dopant-containing layer 1): material triphenylamine derivative (host), distyrylarylene derivative (dopant), film thickness 30 nm.
Electron transport layer (dopant-free layer 2): phenanthroline derivative, film thickness 30 nm.
Intermediate layer (dopant-free layer 3): Li ₂ O (lithium oxide) / quinoline complex / hexaazatriphenylene derivative, film thickness 1.5 nm / 3 nm / 10 nm.
Hole transport layer (dopant-free layer 4): triphenylamine derivative, film thickness 40 nm.
Second light emitting layer (dopant-containing layer 2): carbazole derivative (host), Ir complex (dopant), film thickness 3 nm.
Third light emitting layer (dopant-containing layer 3): carbazole derivative (host), Ir complex (dopant), film thickness 40 nm.
Electron transport layer (dopant-free layer 5): phenanthroline derivative, film thickness 40 nm.
Electron injection layer (dopant-free layer 6): LiF (lithium fluoride), film thickness 1.5 nm.
Second electrode 5 (reflective electrode): Al (aluminum) film thickness 150 nm.

Example 1
An organic EL element having a light emitting surface A of 100 × 100 mm was produced by the above-described layer structure example 1.

Here, in manufacturing, when the size of the element S was 20 × 20 mm and the light emitting surface A was divided into elements, the film was formed so as to satisfy the following conditions.
In all dopant-containing layers 1, each dopant-containing layer 1 has a range in which the average film thickness of each element S in each dopant-containing layer 1 is 93 to 107% of the average film thickness of each dopant-containing layer 1 Is within.
In all the dopant non-containing layers 2, each dopant non-containing layer 2 has an average film thickness of each element S in each dopant non-containing layer 2 of 90 to the average film thickness of each of the dopant non-containing layers 2 Within the range of 110%.
The average chromaticity of each element S is in the range of 98 to 102% of the average chromaticity of the entire light emitting surface A in both CIE-u ′ and CIE-v ′.

(Comparative Example 1)
An organic EL element having a light emitting surface A of 100 × 100 mm was produced by the above-described layer structure example 1.

Here, in manufacturing, when the size of the element S was 20 × 20 mm and the light emitting surface A was divided into elements, the film was formed so as to satisfy the following conditions.
In all the dopant-containing layers 1, each dopant-containing layer 1 has an average film thickness of 93 to 107% of the average film thickness of each dopant-containing layer 1 in each element S in each dopant-containing layer 1 There are about 30% or more elements S that are not within the range.
Of the elements S, the average chromaticity of either CIE-u ′ or CIE-v ′ is about 30% of elements S that are not within the range of 98 to 102% of the average chromaticity of the entire light emitting surface A. It exists in the above number.

(Evaluation)
A voltage was applied, and light emission on the light emitting surface A was visually confirmed.

4A and 4B are photographs of the light emitting surface A, FIG. 4A shows the organic EL element of Example 1, and FIG. 4B shows the organic EL element of Comparative Example 1. The light emitting area is 100 mm □, and the size of each element S is 20 mm □. 4A and 4B, the boundary lines of the elements S with respect to the light emitting surface A are indicated by dotted lines. As shown in FIG. 4A and FIG. 4B, the light emission according to Example 1 is close to uniform with reduced chromaticity unevenness as compared with the light emission according to Comparative Example 1 that is not uniform. As described above, it was confirmed that the organic EL device of Example 1 was excellent in in-plane uniform light-emitting properties with suppressed color unevenness (luminance unevenness and chromaticity unevenness).

A light emitting surface S element 1 dopant containing layer 2 dopant free layer 3 organic layer 4 first electrode 5 second electrode

Claims

Comprising an organic layer comprising two or more dopant-containing layers and one or more dopant-free layers;
When the light-emitting surface is divided as a plurality of elements into sections of a predetermined size,
In at least one of the two or more dopant-containing layers, the average film thickness of each element in the dopant-containing layer is in the range of 90 to 110% of the average film thickness of the entire dopant-containing layer. ,
In the CIE 1976 (u ′, v ′) chromaticity diagram, the average chromaticity of each element represented by the u ′ value and the v ′ value is the average chromaticity of the entire light emitting surface in both the u ′ value and the v ′ value. Of 98 to 102% of
Each element is an organic electroluminescence element in which the total thickness of the two or more dopant-containing layers is smaller than the total thickness of the one or more dopant-free layers.
2. The organic electroluminescence device according to claim 1, wherein each of the elements has a total thickness of the two or more dopant-containing layers of 25 to 35% with respect to the thickness of the organic layer.
Each dopant-containing layer in the two or more dopant-containing layers has an average film thickness of each element in each dopant-containing layer within a range of 93 to 107% of the average film thickness of each dopant-containing layer as a whole.
Each of the non-dopant-containing layers in the one or more non-dopant-containing layers has an average film thickness of each element in each of the non-dopant-containing layers within a range of 90 to 110% of the average film thickness of each of the non-dopant-containing layers. The organic electroluminescence device according to claim 1 or 2, wherein
A reflective electrode adjacent to the organic layer;
Among the organic layers, the adjacent organic layer adjacent to the reflective electrode has an overall film thickness of 30 to 50 nm, and the average film thickness of each element in the adjacent organic layer is the average film thickness of the entire adjacent organic layer. The organic electroluminescence device according to any one of claims 1 to 3, which is within a range of 93 to 107% of the above.
The organic electroluminescence element according to any one of claims 1 to 4, wherein an element showing the minimum luminance among the plurality of elements shows a luminance of 70% or more with respect to an element showing the maximum luminance.
The organic layer is provided between a reflective electrode and a transparent electrode,
The transparent electrode is provided on the inner surface of a light transmissive substrate provided with a light scattering layer on the outer surface,
In the CIE1976 (u ′, v ′) chromaticity diagram, the average chromaticity of each element represented by the u ′ value and the v ′ value is the average color of the entire light emitting surface in both the u ′ value and the v ′ value. The organic electroluminescence device according to any one of claims 1 to 5, which is within a range of 98.5 to 101.5% of the degree.