JP4600881B2 - Manufacturing method of glass caps for organic EL devices - Google Patents

Description

  The present invention relates to a method of manufacturing a glass cap of an organic EL element, and more particularly to a manufacturing method that enables mass production of a glass cap of a top emission type organic EL element, particularly a glass cap integrated with a microlens.

Organic electroluminescence elements (hereinafter referred to as “organic EL elements” for short) have become possible to form high-purity, high-quality laminated films with a thickness of nm class due to recent advances in thin film formation technology, and have a thickness of about 5V. Low voltage operation is possible.
In this way, organic EL elements are attracting attention as elements for next-generation display systems that have low power consumption, high quality, are thin, and can display curved surfaces.

In an organic EL element, a plurality of films composed of predetermined organic molecular components are sequentially stacked to form an organic EL layer, and electrode layers are attached to both the upper and lower sides to form an OLED (organic light emitting diode). A predetermined voltage or current is applied to inject electrons and holes into the organic EL layer, and the phenomenon of light emission when electrons and holes recombine is utilized.
Therefore, in order to perform the display function by guiding the light emission to the outside, at least one of the upper and lower electrodes must be transparent.

  As this transparent electrode film, ITO (Indium Tin Oxide) is widely used as a material capable of achieving both electrical conductivity and transparency, but in general, annealing is required to reduce the electrical resistance of ITO, and Polishing is necessary to increase the smoothness of the ITO surface (to reduce the roughness).

Since the organic EL layer deteriorates when the ITO is annealed at a high temperature, the organic EL layer has to be formed after the ITO.
That is, the stacking order is [substrate-first electrode (ITO) -organic EL layer-second electrode (may be an opaque electrode)], and light is emitted from the substrate side (bottom emission), so the substrate must also be transparent. Usually, a glass substrate is used.

  However, the glass substrate has poor thermal conductivity, and the heat dissipation during operation is insufficient to dissipate heat, resulting in a high temperature, which tends to deteriorate the organic EL layer.

Furthermore, in order to obtain a high-speed and high-definition display system, it is necessary to drive an active matrix (TFT). As a result, the aperture ratio decreases, and the external conversion efficiency of light emission decreases.
That is, in order to ensure the required amount of light emission, the power consumption increases, and accordingly, the amount of heat generated in proportion to the power consumption increases, resulting in a higher temperature, and the organic EL layer is more likely to deteriorate.

Therefore, a method of making the second electrode transparent to be [substrate-TFT-first electrode-organic EL layer-second electrode (ITO)] and emitting light from the opposite side of the substrate (top emission) has been studied.
In the case of the top emission type, the cap that seals and protects the OLED or the like on the opposite side of the substrate must be not only rigid but also transparent, so a glass cap is used.

  The size of the glass cap roughly corresponds to the size of the substrate, and a leg is required at the edge of the glass cap. The OLED mounted on the substrate with the tip of the leg bonded to the corresponding edge of the substrate, etc. To form a sealed space for accommodating.

Such a glass cap with legs is usually formed by a method of digging by sandblasting or the like, but the inner surface of the digging is rough and opaque, and cannot be used for a top emission type organic EL element.
In addition, there is a method of selectively etching with hydrofluoric acid etc. by applying a mask, but hydrofluoric acid is not only a powerful drug but also the inner surface formed by etching tends to become opaque, and good dimensions by side etching etc. It is difficult to obtain accuracy.

Therefore, press molding in which the glass is heated and softened and applied to a press die is used.
For example, Patent Document 1 discloses a technique of forming a rear glass of an organic EL element (of bottom emission type) by a hot press method integrally with a desiccant storage space.

  However, as a press mold material for the top emission type glass cap, in addition to the hardness, strength and durability under high temperature and high pressure, unlike the bottom emission type, high surface accuracy, high thermal conductivity, Since it is necessary to satisfy the conditions such as good releasability without reacting with glass components or volatile components from glass, graphite (graphite), glassy carbon (glassy carbon), etc. are used. .

  For example, Patent Document 2 discloses a technique for improving surface accuracy and releasability by forming at least a die functional surface of a press die with graphite having a uniform crystal orientation.

  In Patent Document 3, an optical element having high shape accuracy, a glass substrate on which a pattern is formed by fine irregularities on a surface, and the like are press-molded and manufactured using a glass mold composed of glassy carbon. Technology is disclosed.

However, even if these press dies are used, especially when the size of the glass cap is increased, “swells” and “scratches” that impair the specified surface accuracy occur on the glass surface, and the display image is distorted. was there.
JP 2003007453 A JP-A-8-239227 Japanese Patent Laid-Open No. 2002-255566

  In order to solve the above-mentioned problems that occur in the production of glass caps particularly required for large, high-definition top emission organic EL elements, the present invention has high surface accuracy free from “swells” and “scratches”. It aims at providing the manufacturing method of the glass cap which has transparency.

  Another object of the present invention is to provide a method for producing a glass cap suitable for a top emission type organic EL device, which is integrally provided with microlenses having high surface accuracy and transparency.

In order to achieve the above object, the method for producing a glass cap of an organic EL device according to the present invention is the press working method using a press die of graphite or a glassy carbon material as described in claim 1, wherein the material of the press die is carbon. Nanotubes are mixed, and the press die includes a press functional surface that integrally forms a microlens array on the inner surface of the glass cap .

  According to the method for producing a glass cap of an organic EL element according to the present invention, since a carbon nanotube is mixed with a press mold material made of graphite or glassy carbon, a press mold that is harder and has high thermal conductivity is obtained. Therefore, it is possible to economically provide a method for producing a glass cap having high surface accuracy and transparency without “undulation” and “scratches”.

  In particular, according to the method for producing a glass cap of an organic EL element according to the present invention, a microlens array having high surface accuracy and transparency can be economically formed on the inner surface of the glass cap in an integrated form with the glass cap.

Embodiments according to the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a method for producing a glass cap of an organic EL element in the first embodiment. FIG. 2 is a press mold used in the second embodiment, the obtained glass cap, and the organic element. It is a cross-sectional schematic diagram which shows how to use.

  The present invention is disclosed in Non-Patent Document 1 by Professor Koichi Sugimoto of Shinshu University and others, “As a press mold material, carbon nanotubes are mixed with graphite or glassy carbon, so that the heat conductivity of the press mold is Is improved, and high-temperature precision processing of glass becomes possible. "

The present invention is disclosed in Patent Document 4, “By mixing carbon nanotubes with graphite or glassy carbon as the material of the press mold, the hardness and strength of the press mold is improved and high-temperature precision processing of glass is possible. Is based on the knowledge.
17th page of the Nikkei Sangyo Shimbun March 16, 2004 issue JP 2003-165729 A

  Referring to FIG. 1, a glass cap for a top emission type organic EL element in this example is formed by the following procedure.

As shown in FIG. 1A, an upper mold 10 serving as a heater weight, an intermediate mold 20 serving as a guide, and a lower mold 30 serving as a carbon heater are prepared as press molds.
The upper die 10 includes a lower press functional surface 10a and a side press functional surface 10b, and further includes a stopper 15 extended laterally at the upper portion. The stopper 15 has a stopper surface 15a on the lower surface.
The middle die 20 has a through hole 20b at the center, a stopper surface 20a at the top, and the side press functional surface 10b of the upper die 10 is slidable with the through hole 20b.
The lower die 30 includes a recess composed of a lower press functional surface 30a and a side press functional surface 30b.

  The entire upper, middle, and lower press dies, or at least the portion including the press functional surface, is made of graphite or glassy carbon mixed with carbon nanotubes.

  The middle mold 20 and the lower mold 30 are fixed to each other so that the positional relationship between the middle mold 20 and the lower mold 30 can be adjusted by a feed mechanism (not shown) composed of a bolt and a nut provided at a position indicated by a dashed line 25. When the upper die stopper surface 15a comes into contact with the middle die stopper surface 20a by sliding down the middle die through hole 20b as indicated by the middle arrow, the upper die lower press functional surface 10a, side press A predetermined gap corresponding to the thickness of the glass to be processed is formed between the functional surface 10b and the lower press functional surface 30a and the side press functional surface 30b of the lower die.

Here, the glass plate 100 which is a workpiece is arranged between the middle mold 20 and the lower mold 30, and the upper 10 is an arrow in the figure with the through hole 20 b of the middle mold 20 as a guide under an appropriate temperature and pressure. The stopper surface 15a is lowered in the direction until it comes into contact with the stopper surface 20a.
Then, as shown in FIG. 1B, the glass plate 100 is press-molded, and a desired glass cap having a “concave” shape whose cross section is composed of the bottom portion 110 and the side portion 120 is obtained.

The part including at least the press function surface of the press die according to the present embodiment is made of graphite or glassy carbon, and since carbon nanotubes are mixed, it is harder and has a higher thermal conductivity than before.
Therefore, even if the obtained glass cap is processed at a high temperature, the press mold is hard and has high strength, so there is no “swell”, and the press mold has high heat conductivity and good releasability, so that “scratches” occur. And high surface accuracy and transparency.

  Referring to FIG. 2, according to the present embodiment, as shown in FIG. 2 (A), the lower press functional surface 10a of the upper mold 10 is made of graphite or glassy carbon containing carbon nanotubes, and is formed into a microlens array. A corresponding array of concave molds 40 is provided.

  When the glass plate 100 is processed in the same manner as in the above embodiment using this press die, as shown in FIG. 2B, a microlens array comprising a plurality of convex molds 110a is formed on the inner surface of the bottom 110 of the glass cap. Is formed integrally with the bottom 110 of the glass cap.

  For the same reason as in Example 1, the obtained glass cap has no “swell” and “scratches”, and has high surface accuracy and transparency that faithfully reproduces the mold shape of the microlens array.

  As shown in FIG. 2C, the glass cap obtained in this manner is turned upside down, and an organic light emitting diode (OLED) 140 or the like separately formed on the substrate 130 is installed so as to be covered with the bottom 110, The tip of the side portion 120 is bonded to the edge portion of the substrate 130 to seal the organic light emitting diode (OLED) 140 and the like.

  The OLED 140 emits light of a predetermined color tone when activated, and the emission intensity is distributed in proportion to cos θ, where 1 is the upper vertical direction in the drawing and θ is the separation angle from the vertical direction.

Each convex part 110a of the microlens array becomes a convex lens and collects the above-mentioned light emission, so that the luminance of the display screen viewed from above the drawing can be increased.
In other words, the power consumption can be suppressed to obtain the same luminance, that is, the temperature rise due to heat generation can be suppressed, and the life of the organic EL layer can be extended.

  In this figure, the convex size and pitch of the microlens array correspond to the size and pitch of the OLED on a one-to-one basis, but the invention is not limited to this.

  According to the present embodiment, it is possible to form a highly accurate and highly transparent microlens array that exhibits such an effect integrally with the glass cap, that is, without additional manufacturing costs.

3 is a schematic cross-sectional view showing a method for producing a glass cap of an organic EL element in Example 1. FIG. It is a cross-sectional schematic diagram which shows the press type | mold used in Example 2, the obtained glass cap, and the usage in the organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Upper mold | type 10a Lower press functional surface 10b Side press functional surface 15 Stopper 15a Stopper surface 20 Medium mold 20a Stopper surface 20b Through-hole 25 Dash-dot line which shows a feed mechanism 30 Lower mold | type 30a Lower press functional surface 30b Side press functional surface 40 Concave surface Mold 100 Glass plate 110 Bottom 110a Convex mold of microlens array 120 Side 130 Substrate 140 Organic EL light emitting diode (OLED)

Claims (1)

In the press working method using a press die of graphite or glassy carbon material, carbon nanotubes are mixed with the material of the press die ,
The press mold includes a press function surface that integrally forms a microlens array on the inner surface of the glass cap .
The manufacturing method of the glass cap of the organic EL element characterized by the above-mentioned.

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