CN1685251A - Blue color filter and organic electroluminescence element using the blue color filter - Google Patents

Abstract

A blue color filter which comprises a 1 st dye represented by the structural formula in the specification, a binder resin, and a 2 nd dye which absorbs fluorescence of the 1 st dye and does not have maximum fluorescence in a visible wavelength region, and which has high blue purity and transmittance and good contrast and is suitable for an organic EL display, and an organic EL element using the blue color filter can be provided.

Description

Blue color filter and organic electroluminescence element using the blue color filter

technical field

The present invention relates to a blue color filter used in display devices of portable terminals and industrial measuring instruments, and an organic electroluminescent element (hereinafter simply referred to as "organic EL") using the blue color filter.

Background technique

As one of the multi-color or full-color methods of organic EL displays, a color conversion method is disclosed in publications such as JP-A-3-152897 and JP-A-5-258860. The fluorescent material that absorbs the light in the light-emitting region of the organic light-emitting body and emits fluorescence in the visible light range is used in the color conversion method in the color filter. According to this method, the luminous color of the organic luminescent body is not limited to white, therefore, it can be applied to use organic luminous bodies with higher brightness as light sources, for example, using blue light-emitting organic luminous bodies to convert blue light into different wavelengths. The color conversion method of green light or red light is described in JP-A-3-152897, JP-A-8-286033, and JP-A-9-208944. If the fluorescent conversion film containing this fluorescent pigment is patterned with high precision on a transparent support substrate, it is possible to construct a full-color display even with low-energy light such as near-ultraviolet light or even visible light of an organic light-emitting body. Emissive display.

In an organic EL element using a color conversion method composed of a color filter, a color conversion filter, and an organic luminescent body, heat resistance, weather resistance when used as a display, and And the quality required for high-definition images, the use of color filters made by the pigment dispersion method is the mainstream, in which red, blue or green pigments are finely dispersed in the photosensitive resin solution to a particle size of 1 μm or less, and then It is applied on a glass substrate, and pixels are formed in a predetermined pattern by photolithography (see JP-A-4-37987, JP-A-4-39041, etc.).

People have been looking forward to improving the color purity, color saturation, and light transmission of the color filter. In order to increase the light transmission, the current method is to reduce the content of the coloring pigment in the image forming material relative to the photosensitive resin. , or thinning the film thickness of the pixels formed using the image forming material.

However, in these methods, the color saturation of the color filter itself is reduced, and the overall display becomes white, sacrificing the vividness of the color necessary for display. On the contrary, if the color saturation is given priority and the coloring pigment content is increased, the overall display Dimming, in order to ensure brightness, the amount of light from the background light must be increased, thereby increasing the power consumption of the display.

For these problems, in order to increase the amount of light transmission, a well-known method is to finely disperse the particle size of the pigment particles to less than half of the color wavelength (see Kiyoshi Hashizume, Journal of Color Material Association, December 1967, p608 ), but because the blue pigment has a shorter color wavelength than other red and green pigments, in this case further microdispersion is required, resulting in increased cost and stability after dispersion.

As a blue pigment, copper phthalocyanine blue with α-type, β-type, and ε-type crystal forms is widely used (see Handbook of Color Material Engineering, Compilation of Color Material Association, p333), if in the color filter If α-type copper phthalocyanine blue is used alone as a blue pigment, its tinting strength is low. In order to achieve the target color saturation, more pigments must be mixed in the photosensitive resin. After forming a color filter, its heat-resistant Discoloration and adhesion to glass substrates are still problems. In addition, there are problems such as a large amount of transmitted light having a wavelength of 600 nm or more, and a decrease in color purity.

On the other hand, when the ε-type copper phthalocyanine blue is used alone as the blue pigment, from the perspective of its excellent tinting strength, although the amount of addition in the photosensitive resin can be reduced, if the mixing amount of the pigment is increased to obtain If the target color saturation is achieved, the light-shielding property of the photosensitive resin at the curing wavelength of 365nm is improved, the photocuring sensitivity is reduced, and problems such as reduced film thickness and unstable pattern occur during development.

Since the β-type copper phthalocyanine blue is a slightly greenish blue, if it is used alone as a blue pigment, the target NTSC hue will vary greatly.

In addition, it is known that a pigment mixed with copper phthalocyanine blue and dioxazine violet is used in a color filter (see JP-A-6-95211, JP-1-200353, JP-4 -37987 bulletin, etc.), if any one of the above-mentioned three kinds of copper phthalocyanine blues is used for color mixing with the I.C. Although the color purity can be improved, there is a problem that the transmission of light in the target blue region of 420 to 500 nm is suppressed, and the luminance when used as a display decreases. When used as a display, the light transmittance of the blue region is suppressed to 70% to 80% by the polarizing plate compared with other color regions, so it is required to increase the light transmittance of the blue color filter.

An object of the present invention is to provide a blue color filter having a high blue transmittance and a low green transmittance, and an organic electroluminescence element having a good blue purity.

Contents of the invention

In order to achieve the above object, in the present invention, the blue color filter contains the first pigment represented by the structural formula (1) and an adhesive resin, and also contains the fluorescence that absorbs the above-mentioned first pigment and has no color in the visible wavelength region. The second pigment for the maximum fluorescence.

[Structural formula (1)]

[In the structural formula (1), R ₁ to R ₆ each independently represent a substitutable hydrogen atom, an alkyl group, an aryl group or a heterocyclic group. R ₇ represents a chain unsaturated hydrocarbon group having 1 to 6 carbon atoms. X ^- means selected from I ^- , Br ^- , Cl ^- , F ^- , ClO ₃ ^- , BrO ₃ ^- , IO ₃ ^- , ClO ₄ ^- , BF ₄ ^- , PF _{4 - , SbF 4} ^- _, ^BrO ₄ ^- and organic The anion in the anion. ]

As mentioned above, by using the first pigment represented by the structural formula (1) as the blue dye of the blue color filter, not only can suppress the light transmittance of 500nm to 600nm and improve the blue purity, but also can be used as a light transmittance Excessive high blue color filter. In addition, while containing the first pigment, it also contains a second pigment that absorbs the fluorescence of the first pigment and does not have the maximum fluorescence below 750 nm, which is the visible wavelength region, so that the second pigment absorbs the fluorescence emitted by the first pigment. The generated 600nm~700nm fluorescence prevents the decrease of blue purity.

The blue color filter of the present invention contains the first dye represented by the structural formula (1) and a binder resin, and also contains the second dye represented by the structural formula (2).

[Structural formula (1)]

[In the structural formula (1), R ₁ to R ₆ each independently represent a substitutable hydrogen atom, an alkyl group, an aryl group or a heterocyclic group. R ₇ represents a chain unsaturated hydrocarbon group having 1 to 6 carbon atoms. X ^- means selected from I ^- , Br ^- , Cl ^- , F ^- , ClO ₃ ^- , BrO ₃ ^- , IO ₃ ^- , ClO ₄ ^- , BF ₄ ^- , PF _{4 - , SbF 4} ^- _, ^BrO ₄ ^- and organic Anions in anions. ]

[Structural formula (2)]

[In the structural formula (2), R ₁ represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group. X ^- means selected from I ^- , Br ^- , Cl ^- , F ^- , ClO ₃ ^- , BrO ₃ ^- , IO ₃ ^- , ClO ₄ ^- , BF ₄ ^- , PF _{4 - , SbF 4} ^- _, ^BrO ₄ ^- and organic Anions in anions. Y represents an O atom or an S atom. a represents an integer of 1-6. ]

In addition, the blue color filter of the present invention may contain a quencher anion that quenches the fluorescence of the above-mentioned first dye or second dye.

In the organic electroluminescence element of the present invention, the above-mentioned blue color filter is used as at least a part of the color filter.

Description of drawings

FIG. 1 is a schematic cross-sectional view of an organic EL element including a blue color filter of the present invention.

DESCRIPTION OF SYMBOLS: 100 organic EL element, 10 transparent support substrate, 20 blue color filter, 30 organic protective layer, 40 inorganic oxide film, 500 organic light emitting body, 50 transparent anode, 51 hole injection layer, 52 hole transport layer , 53 light emitting layer, 54 electron injection layer, 55 cathode.

Detailed ways

As shown in FIG. 1 , the organic EL element 100 of this embodiment is formed on a transparent support substrate 10 in sequence with a blue color filter 20 , an organic protective layer 30 , an inorganic oxide film 40 , a transparent anode 50 , a hole injection layer 51 , The hole transport layer 52 , the light emitting layer 53 , the electron injection layer 54 , and the cathode 55 constitute the organic EL element 100 as a whole.

Next, each material used for preparing the blue image-forming material for forming the blue color filter 20 of the present invention will be described.

[the first pigment]

The blue color filter of the present invention contains a cyanine-based dye represented by structural formula (1) as a first dye. One type of dye represented by the structural formula (1) may be used alone, or a plurality of types thereof may be used in combination. Since the cyanine-based dye represented by the structural formula (1) has high chemical and thermal stability, the heat resistance of the blue color filter is high even without using the pigment dispersion method. Furthermore, other blue pigments, such as copper phthalocyanine system, can also be mixed and used with a 1st pigment.

When obtaining the blue image forming material of the present invention, the mixing ratio of the cyanine dye represented by the structural formula (1) to the binder resin is preferably 0.1 to 40 parts by weight. Thereby, not only the transmission of light of 500 to 550 nm can be suppressed, but also the color purity can be improved. In addition, the cyanine-based dye represented by the structural formula (1) may be used after being pigmented, and a well-known method can be utilized as a method for producing a blue pigment dispersion. For example, the copper phthalocyanine blue and the cyanine pigment represented by the structural formula (1) are mixed together with an organic solvent, a pigment derivative for dispersion stabilization (added if necessary), and a dispersant, using a dispersing machine such as a sand mixer. Microdispersion and stabilization of pigments, thereby, a blue pigment dispersion containing copper phthalocyanine blue and a cyanine pigment represented by the structural formula (1) can be prepared.

[the second pigment]

A dye that absorbs the fluorescence (600 nm to 700 nm) of the first dye and does not have fluorescence in the visible wavelength region (750 nm or less) is added as a second dye. The mixing ratio of the second dye to the binder resin is preferably 0.1 to 40 parts by weight. In addition, in order to function as a blue color filter, it is preferable to have a dye that does not have absorption in the blue wavelength region. Specifically, when added to a color filter, a pigment having a transmittance of 60% or more at 450 nm can be used.

Examples include 1,1'-diethyl-4,4'-carbocyanine iodide (cryptocyanine), 1,1'-diethyl-2,2'-dicarbocyanine iodide ( DDI), 3,3′-dimethylidenetricarbocyanine iodide (Methyl DOTCI), 1,1′,3,3,3′,3′-hexamethylindoletricarbocyanine iodide (HITCI), IR125 (manufactured by Lambda Phisik), iodide 1,1′-diethyl-4,4′-carbocyanine (cryptocyanine), IR144 (manufactured by Lambda Phisik), iodide 3,3′- Diethyl-9,11-neopentenylthiazoletricarbocyanine (DNTTCI), iodide 1,1′,3,3,3′,3′-hexamethyl-4,4′,5,5 '-Dibenzo-2,2'-indoletricarbocyanine (HDITCI), 1,2'-diethyl-4,4'-dicarbocyanine iodide (DDCI-4), etc.

Alternatively, a cyanine-based dye represented by structural formula (2) can be used as the second dye. Specific examples include 3,3'-diethylthiazoletricarbocyanine iodide (DTTCI), 3,3'-diethyl-4,4',5,5'-dibenzothiazoletricarbonyl iodide Cyanine (DDTTCI), etc.

[Structural formula (2)]

[In the structural formula (2), R ₁ represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group. X ^- means selected from I ^- , Br ^- , Cl ^- , F ^- , ClO ₃ ^- , BrO ₃ ^- , IO ₃ ^- , ClO ₄ ^- , BF ₄ ^- , PF _{4 - , SbF 4} ^- _, ^BrO ₄ ^- and organic Anions in anions. Y represents an O atom or an S atom. a represents an integer of 1-6. ]

[quencher]

Since the dye used is a cationic dye, an anionic singlet oxygen quencher can be used as the quencher, for example. Specifically, transition metal chelates and bis-iminium salts disclosed in JP-A-59-55795 and JP-A-60-234892 can be used.

[glue]

As the adhesive resin used for the blue color filter of the present invention, as long as it has visible light transmittance and good adhesion to the substrate, known thermoplastic resins, thermosetting resins, photocurable resins, etc. can be used. resin etc. Photosensitive resins are especially ideal because they make it easier to create fine patterns for color filters.

[Production of blue color filter and organic EL element]

The blue color filter layer 20 is formed by applying a blue image-forming material composed of each of the above-mentioned materials on the transparent support substrate 10 in a predetermined pattern. The coating method is not particularly limited, and the usual spin coating method, roll coating method, pour coating method, screen printing method, inkjet method, etc. can be used. The curing method is not particularly limited, and not only thermal curing (considering the deterioration of the fluorescent material, preferably curing at a temperature not exceeding 150° C.), moisture curing, chemical curing, and light curing (considering the deterioration of the fluorescent material, preferably curing at Curing under visible light conditions), and these curing methods can also be used in combination.

Before or after forming the blue pixels, red or/and green pixel forming materials are used as required to form red or/and green color filters, so that a multi-color color filter can be produced. In addition, the organic luminescent body 500 is laminated on the color filter via the organic protective layer 30 and the inorganic oxide film 40, so that a multi-color organic EL element can be produced. As a lamination method of the organic luminescent body 500, a method in which a transparent anode 50, a hole injection layer 51, a hole transport layer 52, a light emitting layer 53, an electron injection layer 54, and a cathode 55 are sequentially formed on a color filter can be mentioned. Method; a method of attaching the organic luminescent body 500 formed on other substrates to the inorganic oxide film 40 . The organic EL element 100 produced by this method can be applied to both a passive drive organic EL display and an active drive organic EL display.

Embodiments of the present invention will be described below.

(Example 1)

[Making of black mask]

Although it is not shown in FIG. 1, in order to eliminate the influence of reflected light from the ends of the blue color filter 20 and the transparent electrode 50 when evaluating the contrast, a black mask is first arranged, the purpose of which is to remove the light from the transparent support substrate 10. The end of the blue color filter 20 cannot be seen from the surface.

A black mask coating solution (CK8400L, manufactured by Fujifilm ARCH) was applied on the entire surface of a glass transparent support substrate 10 by spin coating, and after heating and drying at 80°C, by photolithography, A stripe-shaped black mask pattern with a pitch of 0.13 mm and a gap of 0.10 mm was obtained.

[Production of blue color filter]

Using a transparent photopolymerizable resin (manufactured by Nippon Steel Chemical Co., Ltd., 259PAP5) as an adhesive, 2 parts by weight of the compound represented by the structural formula (3) was added to 100 parts by weight of the solid content of the transparent photopolymerizable resin. As a blue dye, 1 part by weight of a second dye (HDITCI manufactured by Lambda Physik) represented by the structural formula (4) was added as a coating solution for a blue color filter.

[Structural formula (3)]

[Structural formula (4)]

This blue color filter coating solution was applied to a transparent support substrate 10 by spin coating to form a film, and after heating and drying at 80°C, 0.13 mm pitch and 0.01 mm gap were formed by photolithography. striped blue color filter pattern.

[Production of organic EL elements]

By the above-mentioned method, after the blue color filter 20 is formed on one main surface of the transparent support substrate 1 made of glass, an organic protective layer 30 and an inorganic oxide layer 40 are sequentially formed on it, and an organic light-emitting body is formed thereon. layer 500 to form the organic EL element 100. The organic light emitter layer 500 is formed using six layers consisting of a transparent anode 50 /hole injection layer 51 /hole transport layer 52 /light emitting layer 53 /electron injection layer 54 /cathode 55 . Next, the specific production process thereof will be described.

On the transparent support substrate 10 on which the above-mentioned blue color filter 20 is formed, a transparent photopolymerizable resin (manufactured by Nippon Steel Chemical Co., Ltd., 259PAP5) is coated and dried. An organic protective layer 30 with a thickness of 5 μm was formed, and an inorganic oxide layer 40 made of SiO ₂ with a thickness of 100 nm was formed thereon by sputtering. Next, a layer made of ITO was formed on the entire surface of the above-mentioned inorganic oxide layer 40 by the same sputtering method, and the transparent anode 50 was obtained by performing patterning as described below. That is, after coating a photoresist with a film thickness of 100 nm (manufactured by Tokyo Ohka Co., Ltd., OFRP-800) on the above-mentioned ITO film, a transparent film with a stripe pattern of 0.13 mm line pitch and 0.01 mm gap is formed by photolithography. Anode 50.

Next, the substrate was placed in a resistance heating vapor deposition apparatus, and the hole injection layer 51, the hole transport layer 52, the light emitting layer 53, the electron injection layer 54, and the cathode 55 were formed into films under vacuum conditions in this order. The internal pressure of the vacuum chamber during film formation was reduced to 1×10 ^-4 Pa. Specifically, the hole injection layer 51 is a copper phthalocyanine (CuPc) layer with a thickness of 100 nm, and the hole transport layer 52 is a 4,4'-bis[N-(1-naphthyl)-N- Anilino] biphenyl (-NPD) layer, light-emitting layer 53 is a 4,4'-bis(2,2'-diphenylvinyl) biphenyl (DPVBi) layer with a thickness of 30 nm, and an electron injection layer 54 with a thickness of 30 nm. It is a 20nm tris(8-quinolinolato)aluminum complex (Alq) layer. The cathode is Mg/Ag (weight ratio: 1:10) with a thickness of 20nm, and a striped pattern with a pitch of 0.33mm and a gap of 0.05mm perpendicular to the anode line is formed by mask evaporation technology.

After the film formation of the above-mentioned various layers is completed, the organic EL element 100 is taken out from the vapor deposition device, and under nitrogen conditions, the element is sealed so that it does not directly contact with air (not shown in the figure) by using sealing glass and UV adhesive. out). The finished organic EL element 100 emits blue light having a peak at a wavelength of 470 nm.

(Example 2)

In the formation of the blue color filter in Example 1, except that the second pigment used in Example 1 was replaced with a pigment represented by structural formula (5) as the second pigment, and the transparent photopolymerizable resin An organic EL device was produced in the same manner as in Example 1 except that 1 part by weight was added to 100 parts by weight of the solid content.

[Structural formula (5)]

(Example 3)

In the formation of the blue color filter in Example 2, except that the nickel complex compound represented by the structural formula (6) was added as a quencher at a ratio of 0.3 mol to 1 mol of the first pigment, the rest were carried out according to the same procedure. A blue color filter coating solution was prepared in the same manner as in Example 2, and an organic EL element was obtained in the same manner.

[Structural formula (6)]

(comparative example 1)

A coating material for a blue color filter was prepared in the same manner as in Example 1, except that copper phthalocyanine blue was used as a pigment instead of the first and second colorants used in Example 1. In addition, the amount of pigment added was adjusted so that the light transmittance at a wavelength of 470 nm was the same as that of Example 1 when the blue color filter was formed with the same film thickness as in Example 1.

(evaluate)

The following evaluations were performed on the prepared samples. The evaluation results are shown in Table 1. Here, the CIE chromaticity is to evaluate the chromaticity of the fabricated device by emitting light. Measurement was performed using a colorimeter (manufactured by Otsuka Electronics Co., Ltd., MCPD-1000). Contrast is compared when fluorescent light (1000lx) is irradiated on the display surface of the device from an oblique angle of 45 degrees. The numerical values in the table are relative values when the result of the comparative example is set to 1.0, and if the numerical value is greater than 1.0, the contrast improves. For the transmittance, an absorption spectrum was obtained using an absorptiophotometer (UV-2100PC manufactured by Shimadzu Corporation), and the light transmittance at wavelengths of 470 nm and 510 nm were compared.

[Table 1] Example 1 Example 2 Example 3 Comparative example 1 ①CIE chromaticity (x, y) 0.12, 0.09 0.12, 0.10 0.13, 0.10 0.16, 0.18 ② Contrast 1.4 1.4 1.6 1.0 ③Transmittance (470nm) 85% 85% 85% 85% (510nm) 50% 48% 46% 60%

As shown in Table 1, the light transmittance under the wavelength condition of 510 nm when the film was formed by uniforming the light transmittance under the wavelength condition of 470 nm was higher in the examples than in the comparative example. This means that the color filter of the example has a higher light-shielding performance in the wavelength region where the blue purity is lowered than that of the color filter of the comparative example. In addition, in the color filter of the comparative example in which the pigment is dispersed in the binder, scattering tends to occur in the color filter and at the interface. On the contrary, the color filters of the Examples showed values of high transparency and high contrast in which the pigment was completely dissolved in the adhesive.

Industrial availability

According to the present invention, it is possible to provide a blue color filter suitable for an organic EL display having high blue purity and transmittance and good contrast, and an organic EL element using the blue color filter.

Claims (4)

1. blue color filter is characterized in that: contains the 1st pigment and the adhering resin of useful structural formula (1) expression, also contains fluorescence that absorbs described the 1st pigment and the 2nd pigment that in visible wavelength area, does not have maximum fluorescence simultaneously,

Structural formula (1):

In structural formula (1), R ₁～R ₆Hydrogen atom, alkyl, aryl or the heterocyclic radical that can replace of expression independently respectively, R ₇The expression carbon number is 1～6 chain unsaturated alkyl, X ^-Expression is selected from I ^-, Br ^-, Cl ^-, F ^-, ClO ₃ ^-, BrO ₃ ^-, IO ₃ ^-, ClO ₄ ^-, BF ₄ ^-, PF ₄ ^-, SbF ₄ ^-, BrO ₄ ^-And the negative ion in the organic system negative ion.

2. blue color filter is characterized in that: contains the 1st pigment and the adhering resin of useful structural formula (1) expression, also contains the 2nd pigment of useful structural formula (2) expression simultaneously,

Structural formula (1):

In structural formula (1), R ₁～R ₆Hydrogen atom, alkyl, aryl or the heterocyclic radical that can replace of expression independently respectively, R ₇The expression carbon number is 1～6 chain unsaturated alkyl, X ^-Expression is selected from I ^-, Br ^-, Cl ^-, F ^-, ClO ₃ ^-, BrO ₃ ^-, IO ₃ ^-, ClO ₄ ^-, BF ₄ ^-, PF ₄ ^-, SbF ₄ ^-, BrO ₄ ^-And the negative ion in the organic system negative ion,

Structural formula (2):

In structural formula (2), R ₁Expression hydrogen atom, alkyl, aryl or heterocyclic radical.X ^-Expression is selected from I ^-, Br ^-, Cl ^-, F ^-, ClO ₃ ^-, BrO ₃ ^-, IO ₃ ^-, ClO ₄ ^-, BF ₄ ^-, PF ₄ ^-, SbF ₄ ^-, BrO ₄ ^-And the negative ion in the organic anion, Y represents O atom or S atom.A represents 1～6 integer.

3. blue color filter according to claim 1 and 2 is characterized in that: the quencher negative ion that contains the fluorescence delustring that makes described the 1st pigment or the 2nd pigment.

4. organic electroluminescent device that organic luminorphor and color filter are laminated, it is characterized in that: at least a portion of described color filter is each described blue color filter in the claim 1～3.