JP4607212B2 - Manufacturing method of organic EL element - Google Patents

Description

The present invention relates to an organic electroluminescence using a resin relief plate (hereinafter, "organic EL") relates manufacturing method for the device.

  In recent years, organic EL elements having features such as thinness, low power consumption, and light weight have attracted attention as display elements in mobile phones and the like. This organic EL element is configured by forming an organic light emitting layer containing an organic EL light emitter between two opposing electrodes. By passing a current through the organic light emitting layer, the organic light emitting element is formed. The layer is made to emit light.

The organic EL light emitter includes a low molecular material and a high molecular material. Usually, a low molecular weight material is used, and this is vacuum-deposited on the substrate to form an organic light emitting layer. However, in this case, patterning is performed using a fine pattern mask. There is a problem that the size of the apparatus increases, and the material use efficiency, processing capacity, and yield significantly decrease. Therefore, recently, a polymer material is used as an organic EL light emitter so that it can be used for mass production even if the substrate is enlarged, and this is dissolved and dispersed in a solvent to form ink, and an organic light emitting layer is formed on the substrate by a printing method. Attempts have been made to form them (see, for example, Patent Document 1). However, since all conjugated polymer compounds known as polymer materials have low solubility, it is necessary to use an aromatic compound such as xylene or toluene as a solvent for forming an ink. Since some of these aromatic solvents are highly swellable to high molecular weight polymers, for example, when an organic light emitting layer is formed by the offset printing method, the printing plate swells with the solvent, and dimensional accuracy is obtained by repeating the printing process. May decrease.

On the other hand, there are various printing methods including the offset printing method. Since the organic EL element often uses a glass substrate as a substrate, the offset printing method uses a rubber blanket having elasticity. In addition, a relief printing method using an elastic rubber plate or resin plate is preferable. However, in the offset printing method, since the dimensional accuracy of the rubber blanket described above may be lowered, the relief printing method is often employed. Also in this letterpress printing method, a resin plate is used for rubber plates because of the above-described fear, and commercially available solid plates (for example, those manufactured by Toray Industries, Inc.) are frequently used.
JP 2006-252787 A

  However, since the solid plate is a resin relief plate obtained by evaporating and drying a soluble emulsion composition of a water-soluble polymer such as water-soluble nylon or polyvinyl alcohol and a photosensitive resin, its hardness is hard, There is a problem that damage to the substrate during printing is large.

The present invention was made in view of such circumstances, the dimensional accuracy is stabilized by repeating the printing process, moreover, damage to the substrate during printing of the method for manufacturing have organic EL elements small The purpose is to provide.

In order to achieve the above object, the present invention provides a printing ink in which an organic EL phosphor is dissolved in an aromatic solvent, which is held on a printing convex portion of a relief printing resin relief plate, and an anode is formed on the surface. This is a method for producing an organic EL element in which an organic light-emitting layer is printed by evaporating the solvent after being transferred onto a substrate, and the gist thereof is to use a relief printing plate for letterpress printing described in (A) below.
(A) a polymer addition product of a polyester polyol and a diisocyanate, and a prepolymer composed by adding acrylate, a monofunctional or polyfunctional acrylate monomers and the plate material of a photosensitive resin composition containing,耐芳incense Resin letterpress for letterpress printing having group solvent swellability .

That is, the present inventors have conducted extensive research in order to obtain a method for producing an organic EL element in which the dimensional accuracy is stable even when the printing process is repeated and the damage to the substrate during printing is small. Resin relief printing for letterpress printing using a photosensitive resin composition in which a prepolymer obtained by adding an acrylate to a polymerization addition product of polyol and diisocyanate and a monofunctional or polyfunctional acrylate monomer is used as a plate material ( (Hereinafter, abbreviated as “resin letterpress”), it was found that the initial purpose could be achieved, and the present invention was reached. The resin relief printing plate used in the method for producing an organic EL device of the present invention is a photosensitive resin composition having a polyester skeleton, so that it is more resistant to aromatic solvents than an aliphatic skeleton. It does not swell so much, so that even if the printing process is repeated, the dimensional accuracy of the resin relief printing plate is not lowered, and stable dimensional accuracy is maintained over a long period of time. Moreover, the hardness of the resin relief printing plate is soft, and damage to the substrate during printing is small.

Moreover, since the manufacturing method of the organic EL element of this invention has printed and formed the organic light emitting layer on the board | substrate using the said resin relief plate, even if it manufactures many organic EL elements with one resin relief plate, The dimensional accuracy of the organic light emitting layer of the obtained organic EL element is stable. In addition, damage to the substrate during manufacturing of the organic EL element is small, and the substrate is not damaged.

  Next, the best mode for carrying out the present invention will be described. However, the present invention is not limited to this embodiment.

FIG. 1 shows an embodiment of a resin relief plate used in the method for producing an organic EL element of the present invention. In this embodiment, the resin relief printing plate is used for printing the organic light emitting layer 23 (see FIG. 7) on an organic EL element constituting an organic EL color display or the like (not shown) described later. As shown in FIG. 2 and FIG. 3, which is a cross-sectional view taken along the line AA of FIG. A plurality of printing convex portions 2. A plurality of minute protrusions (minute protrusions) 3 are distributed and formed on the top surface of each printing protrusion 2, and a series of grooves 4 are formed between these minute protrusions 3. Printing ink (not shown) is held in the groove 4.

The resin relief printing plate has a JIS rubber hardness in the range of Shore A 60 to 90 °, preferably in the range of Shore A 65 to 80 °. If the JIS rubber hardness is greater than Shore A 90 °, the hardness may be too hard and damage the substrate. As a result, a clear image (printed image ) may not be obtained.

  The resin letterpress can be developed with an aqueous detergent, and uncured portions are washed away with an aqueous detergent such as washing water when the resin letterpress described later is manufactured.

  Further, the above-mentioned resin relief printing is continuously immersed for 24 hours in an ambient temperature of 20-25 ° C. or less in an anisole, cyclohexylbenzene, tetralin or a mixed solvent thereof, which is an aromatic solvent for dissolving and dispersing the organic EL light emitter. And the weight change rate before and after immersion has a swelling rate within the range of 0.2 to 15%. Thus, the above-mentioned resin letterpress does not swell much with respect to the aromatic solvent. Therefore, even when using a printing ink in which an organic EL light-emitting material is dissolved and dispersed in an aromatic solvent, the resin relief printing plate does not swell so much, so that the dimensional accuracy of the resin relief printing plate does not deteriorate even when the printing process is repeated. Stable dimensional accuracy is maintained over a period.

  The weight change rate is preferably set within a range of 1 to 10%. If the weight change rate exceeds 10%, the dimensional accuracy of the resin relief printing plate may be reduced by repeating the printing process. The weight change rate is preferably as low as possible, and if it is about 1%, the dimensional accuracy is hardly reduced. In this case, there is no possibility that the dimensional accuracy is lowered. Further, when a mixed solvent of anisole, cyclohexylbenzene, or tetralin is used as the aromatic solvent, the blending ratio is arbitrarily set. In measuring the weight change rate, a resin relief plate having a thickness of 0.13 to 0.30 cm cut into a size of 2 cm × 3 cm was used.

  Moreover, it is preferable that the said resin relief plate has the resin characteristic of 15-200% of elongation at the time of cutting | disconnection, 2-100 Mpa of tensile strength, and the maximum tensile force of 30-200N. If this range is exceeded, the rubber hardness will increase, causing the adverse effect of causing damage to the substrate as described above, and if it is less than this range, the rubber hardness will decrease, causing the problem of dripping during printing as described above. Tend to occur.

For example, in the case of printing in a line shape, the shape of the microprojection 3 is preferably a truncated cone shape or a cylindrical shape (a truncated cone shape in FIGS. 2 and 3), and the transferability is better. The height H ₁ of the microprojections 3 is in the range of ₁ to 500 μm, the top surface diameter D ₁ is in the range of ₅ to 500 μm, and the interval W ₁ between the adjacent microprojections 3 is in the range of ₅ to 500 μm. Preferably there is.

Further, in place of the microprojections 3, as shown in FIG. 4 and FIG. 5 which is a BB cross-sectional view of FIG. 4, the top surface of the printing convex portion 2 is arranged in parallel at a predetermined interval. A streak-like uneven portion including a plurality of streak-like ridges 5 and a streak-like groove (streak-like recess) 6 formed between two adjacent streaky ridges 5 may be formed. . The cross-sectional shape of the streaky ridge 5 is preferably a trapezoidal shape or a rectangular shape (trapezoidal shape in FIGS. 4 and 5). The height H ₂ is in the range of 1 to 500 μm, the top width D ₂ is in the range of ₅ to 500 μm, and the groove width (recess width) W _{2 of} the streak-like groove 6 is in the range of ₅ to 500 μm. preferable. Note that when the organic light emitting layer 23 of the organic EL element is applied not for display but for illumination, etc., it can be dealt with by a printing plate with a solid pattern of the entire surface instead of the line pattern as described above.

Resin letterpress used in the manufacture of such organic EL devices is a photosensitive compound in which a prepolymer obtained by adding an acrylate to a polymerization addition product of polyester polyol and diisocyanate and a monofunctional or polyfunctional acrylate monomer are blended. The resin composition is produced using a functional resin composition as a plate material.

  Examples of the polyester polyol include a polyester copolymer obtained by condensation polymerization of a dicarboxylic acid composed of a saturated fatty acid, an unsaturated fatty acid, an aromatic acid and the like and a polyol.

  Here, the polyol means an alcohol having two or more hydroxyl groups in one molecule, and specific examples thereof include ethylene glycol, propylene glycol, diethylene glycol, and the like, which are used alone or in combination.

  Examples of the diisocyanate include aliphatic, alicyclic, and aromatic diisocyanates. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′- Diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, dianisidine isocyanate, 3,3'-ditolylene-4.4'-diisocyanate, p-xylylene diisocyanate, 1,3-cyclohexanedimethyl isocyanate, 1,5-naphthalene diisocyanate , Transvinylene diisocyanate, 2,6-diisocyanate methylcaproate, diphenyl ether-4,4'-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. As a method for polymerizing and adding such polyester polyol and diisocyanate, conventionally known methods are used.

  Examples of the acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyethylene glycol mono (meth) acrylate.

Addition of acrylate with respect to the prepolymer, for example, by conventional grayed rafts polymerization (Tsugiki polymerization method). Here, the ratio of addition of acrylate to prepolymer is usually set within a range of 0.5 to 5.0 mol of acrylate with respect to 1 mol of prepolymer. When the addition ratio of acrylate exceeds the above range, there is a problem that the rubber hardness of the resin letterpress increases, and when it is lower, there is a tendency that a problem that the resin letterpress cannot be formed.

Examples of the monofunctional or polyfunctional monopolymer include 1,3 or 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, and trimethylol. Various acrylate monomers including propane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate Is given.

The blending ratio of the prepolymer obtained by adding acrylate to the above-mentioned polymerization addition product and the monofunctional or polyfunctional acrylate monomer depends on the purpose of achieving a predetermined hardness, flexibility, and swelling rate. Optionally blended. These prepolymers, against the monomer blend, a photopolymerization initiator 0. It mix | blends within the range of 001-10 weight%.

  The photosensitive resin composition may be in the form of a liquid, solid, or powder. When it is in the form of a solid or powder, the photosensitive resin composition is made liquid at the time of use.

Using such a plate material, a resin relief plate used for the production of the organic EL element can be produced, for example, as follows. That is, first, a negative film 11 as shown in FIG. 6 is prepared. The negative film 11 has a portion corresponding to the fine projections 3 of the relief plate formed in the round hole 11a in the region corresponding to the resin relief plate, the inside of the round hole 11a is transparent, and the other portion. Is black. Next, this negative film 11 is laminated on the surface of the lower glass substrate 12, and then a liquid photosensitive resin composition having a polyester skeleton is formed on the surface of the negative film 11 to have a certain thickness. Apply to. In FIG. 6, this coating layer is indicated by reference numeral 13, a portion that is to be uncured, which will be described later, is indicated by reference numeral 13 a in this coating layer 13, and a portion that is to be cured is indicated by a hatched portion S. Next, a transparent base film (not shown) is laminated on the surface of the coating layer 13, and the upper glass substrate 14 is laminated on the surface of the base film.

Next, as shown in FIG. 6, a lamp 15 is used to irradiate light such as ultraviolet rays through the upper glass substrate 14 and the base film, and ultraviolet rays through the lower glass substrate 12 and the negative film 11. Etc. Light is irradiated. Thereby, the part (the hatched part S in FIG. 6) where the light entering from the entire upper surface of the layer made of the photosensitive resin composition 13 and the light entering from the round hole 11a of the negative film 11 arrives is cured. . At this time, the depth at which the light reaches is adjusted by the intensity of the irradiated light. Next, the upper and lower glass base plate 12, the removed negative film 11, a portion (uncured portion) became uncured not reach the light for the black portion of the negative film 11, and washed with developer To remove. And after drying the hardened | cured part, a fine line etc. are hardened reliably by irradiating light, such as an ultraviolet-ray, to the formation side of the microprotrusion 3 (post-exposure). In this way, a resin relief plate as shown in FIG. 1 can be produced.

As described above, in this embodiment, since the plate material of the relief printing resin relief plate used in the method for producing an organic EL element is a photosensitive resin composition having a highly polar polyester skeleton, the plate material The resin relief printing plate produced using is hardly swollen with respect to the aromatic solvent. Therefore, even if the printing process is repeated, the dimensional accuracy of the resin relief printing plate is not lowered, and stable dimensional accuracy is maintained over a long period of time. Moreover, the hardness of the resin relief printing plate is relatively soft, and there is almost no damage to the substrate of the printing medium during printing.

  FIG. 7 shows an embodiment of an organic EL element manufactured using the above-mentioned resin relief plate. In this embodiment, the organic EL element is configured by forming a transparent or translucent anode 22, an organic light emitting layer 23, and a cathode 24 on the surface of a glass substrate 21. This element emits light when a current flows through the organic light emitting layer 23 formed between the two electrodes 22 and 24 by a voltage supplied from a power source 25 connected between the two electrodes 22 and 24. The EL light is displayed through the glass substrate 21. The organic light emitting layer 23 has three types of red (R), green (G), and blue (B). Each color of the organic light emitting layer 23 is formed in a strip shape and arranged in parallel at a predetermined interval. The red, green, and blue are repeated in this order. In printing the organic light emitting layer 23 of one color, one resin letterpress is used, and resin letterpress corresponding to the number of the organic light emitting layers 23 is used.

The organic EL element is manufactured as follows, for example. That is, first, the anode 22 is formed on the surface of the glass substrate 21. In this step, to form a surface in (a) emissions indium tin oxide (ITO), zinc aluminum oxide transparent conductive material vacuum evaporation or sputtering a transparent anode 22 is coated with such a such a glass substrate 21, or A semitransparent anode 22 is formed by thinly depositing gold or platinum.

Next, a hole transport layer and an organic light emitting layer 23 are sequentially formed on the anode 22 by the usual letterpress printing method using the resin letterpress. In the step of forming the organic light emitting layer 23, first, three types of printing inks of red, green, and blue obtained by dissolving and dispersing the organic EL light emitter in an aromatic solvent are prepared. Further, as shown in FIG. 8, a printing machine including a printing roll 31, an anilox roll 32, a printing stage 33, an ink supply device 34, and a doctor 35 that scrapes off excess printing ink on the anilox roll 32 is prepared. Next, the resin relief plate is mounted on a printing roll 31 and the glass substrate 21 on which the anode 22 (not shown) is formed is placed on a printing stage 33. Next, printing ink of a certain color (for example, red) is supplied from the ink supply device 34 to the anilox roll 32, and the printing roll 31 and the anilox roll 32 are rotated. At this time, the printing ink is held in the groove 4 on the top surface of the printing convex portion 2 of the resin relief printing plate. Next, the printing stage 33 is moved in synchronization with the rotation of the printing roll 31 to print a certain color of printing ink on the anode 22 on the surface of the glass substrate 21, and then heated to be an aromatic solvent in the printing ink. The organic light emitting layer 23 is printed by evaporation. Such printing is performed in the same manner for the other two colors, and the three-color organic light-emitting layers 23 are formed at predetermined positions.

  Next, a cathode 24 is formed on the organic light emitting layer 23. The cathode 24 is composed of a single metal element such as Li, Na, Mg, La, Ce, or Ca. In the formation process of the cathode 24, co-evaporation is performed on the organic light-emitting layer 23 while monitoring with a quartz crystal film thickness meter from a separate vapor deposition source for each metal element alone with a resistance heating method under a predetermined degree of vacuum. To do. Thereafter, the bipolar electrodes 22 and 24 are connected to the power source 25. In this way, the organic EL element is manufactured.

According to such a method for manufacturing an organic EL element , even if a large number of organic EL elements are manufactured with one resin relief plate, the dimensional accuracy of the organic light emitting layer 23 of the obtained organic EL element is stable. Moreover, damage to the substrate during the manufacture of the organic EL element is small, and the glass substrate 21 is not damaged.

The printing ink in which the organic EL light emitter is dissolved in a solvent has a viscosity in the range of 2 to 100 mPa · s, and a low molecular material or a high molecular material is used. Examples of the low molecular weight material include triphenylbutadiene, coumarin, Nile red, oxadiazole derivatives, and the like. Examples of the polymer material include poly (2-decyloxy-1,4-phenylene) (DO-PPP) and poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylene vinylene. ] (MEH-PPV), poly [5-methoxy- (2-propanoxysulfonide) -1,4-phenylenevinylene] (MPS-PPV), poly [2,5-bis (hexyloxy-1,4) -Phenylene)-(1-cyanovinylene)] (CN-PPV), poly [2- (2'-ethylhexyloxy) -5-methoxy-1,4-phenylene- (1-cyanovinylene)] (MEH-CN-PPV ), Poly (dioctylfluorene) and the like. Examples of the solvent used for these include cyclohexyl benzene, trichlorobenzene, anisole, xylene, ethyl benzoate, cyclohexyl pyrrolidone , dichlorobenzene, toluene, and the like. These may be used alone or in combination of two or more. The mixing ratio when mixing is determined by the organic light emitting layer 23.

  Next, examples will be described.

  A resin relief plate having the structure shown in FIGS. 1 to 3 was prepared. This resin letterpress had a JIS rubber hardness of Shore A 85 ° and a weight change rate of 5% when immersed in anisole for 24 hours at room temperature 23 ° C. Such a resin relief printing plate is produced by using the plate material shown in Table 1 below and in the same manner as the production method of the resin relief printing plate, having a total plate thickness of 1.3 mm and a substrate thickness of 0.00. It was 7 mm.

  As a printing machine, the one shown in FIG. The printing conditions were such that the nip width between the resin relief plate and the anilox roll was adjusted to 3.5 to 6.5 mm, the nip width between the resin relief plate and the glass substrate was adjusted to 7.5 to 12.5 mm, and the printing speed was 20 m / Adjusted to minutes.

  As the pseudo ink, anisole and tetralin were mixed one-to-one, and polyvinyl carsol (manufactured by Kanto Chemical Co., Inc., molecular weight 90,000) was dissolved in an amount of 0.2 to 1.5% by weight. This simulated ink was transported by dry air of 0.01 to 0.1 MPa and adjusted to be supplied on an anilox roll by 0.5 to 5 milliliters in 40 seconds.

  The resin relief plate is attached to a plate cylinder of a printing machine, the printing machine is driven at the printing conditions and printing speed, and pseudo ink is printed on a glass substrate for constituting an organic EL element, and then the temperature is 60 to 90 ° C. Anisole and tetralin were removed by evaporation on a heated hot plate, and only the active ingredient was deposited to form an organic light emitting layer.

As a result of measuring this organic light emitting layer with an optical interference microscope, a film thickness of 400 to 700 mm (40 to 70 nm) was measured. Further, it was confirmed that the pseudo ink emitted light by applying an ultraviolet lamp close to the film surface, and the organic EL light emitting body was applied.

It is a side view which shows one Embodiment of the resin letterpress used for the manufacturing method of the organic EL element of this invention. It is an enlarged plan view of the principal part of the said resin letterpress. It is AA sectional drawing of FIG. It is an enlarged plan view of the principal part which shows the modification of the said resin letterpress. It is BB sectional drawing of FIG. It is explanatory drawing which shows the manufacturing method of the said resin relief printing plate. It is explanatory drawing which shows one Embodiment of an organic EL element. It is explanatory drawing which shows the manufacturing method of the organic EL element of this invention .

Claims (5)

Resin printing for letterpress printing Printing ink, which is held on the printing convex part of the letterpress and dissolved in an organic EL phosphor in an aromatic solvent, is transferred onto a substrate with an anode formed on the surface, and then the solvent is evaporated. A method for producing an organic EL element, wherein the organic light-emitting layer is vaporized and printed to form an organic light-emitting layer, wherein the relief printing plate for letterpress printing (A) below is used.
(A) a polymer addition product of a polyester polyol and a diisocyanate, and a prepolymer composed by adding acrylate, a monofunctional or polyfunctional acrylate monomers and the plate material of a photosensitive resin composition containing,耐芳incense Resin letterpress for letterpress printing having group solvent swellability . The method for producing an organic EL element according to claim 1, wherein the letterpress printing resin letterpress has a JIS rubber hardness of Shore A 60 to 90 °, and the plate material can be developed with an aqueous detergent . The resin letterpress for letterpress printing is an aromatic solvent for dissolving and dispersing the organic EL phosphor, anisole, cyclohexylbenzene, tetralin, or a mixed solvent thereof for 24 hours under an environment at room temperature of 20 to 25 ° C. The manufacturing method of the organic EL element of Claim 1 or 2 which has a swelling rate in the range of 0.2-15% of weight change rate before and behind immersion soaking continuously . The letterpress resin relief plate, elongation at break from 15 to 200% at a tensile strength 2～100MPa, according to claim 1 having the resin properties of maximum tensile force 30~200N organic Manufacturing method of EL element. The above-mentioned resin printing plate for letterpress printing has printing projections on the pattern printing surface, and on the surface thereof, a stripe-like depression having a depression width for holding printing ink of 10 to 500 μm, or a projection diameter of 10 to 10 mm. The manufacturing method of the organic EL element as described in any one of Claims 1-4 in which the micro convex part which is 500 micrometers is formed .

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