JPH0752632B2 - Substrate with antireflection film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a substrate with an antireflection film that can be used for a thin film EL element, a fluorescent display tube, a filter, and the like. The present invention will be described below with respect to a fluorescent display tube.

[Prior art]

As an antireflection film for a conventional fluorescent display tube, there is disclosed in JP-A-60-11.
In 5137, an invention of a structure including an antireflection film formed of a colored thin film deposited on a translucent insulating substrate and a wiring conductor and an anode conductor formed of a metal thin film disposed on the antireflection film is known. .

However, the above-mentioned conventional example is an example applied to a front emission type fluorescent display tube in which the light emission of the phosphor layer is observed from the other side of the substrate through the translucent insulating substrate. Therefore, if a colored thin film is present in a portion other than the anode conductor, it impedes the transmission of light emitted from the phosphor layer, and therefore the colored thin film had to be patterned by means of photolithography. Generally, a colored thin film contains many metal oxides and is not easily etched. Further, since the anode conductor is aluminum, it is easily etched and is a substance that is easily etched by acid or alkali. It was not easy to improve the accuracy by performing the etching once. Further, if the etching is performed twice, the number of steps increases, which causes a cost increase.

The fluorescent display tube shown in FIG. 3 is described in JP-A-60-81799, in which a transparent conductive oxide film 12 such as ITO or In ₂ O ₃ and an Al film 13 are formed on a substrate 11. This structure is characterized in that the composite electrode is laminated to form a composite electrode, and the composite electrode layer is heat-treated in air or in a nitrogen atmosphere to blacken the interface of the composite electrode. In this conventional example, the blackened conductive oxide film 12 acts to prevent reflection.

However, since this antireflection film 12 is a film having conductivity, it has to be patterned in order to be used for a fluorescent display tube, and the same problems as those of the above-mentioned conventional example to be performed by means of photography are required. There was a point.

In FIG. 3, 14 is an insulating layer, 15 is a phosphor layer, 16 is a grit, 17 is a filament cathode, and 18 is an envelope.

[Object of the Invention]

The present invention forms a transparent metal oxide thin film having insulating properties, forms a conductive metal wiring conductor and an anode conductor on the thin film, and heat-treats the conductive metal to form a transparent conductive film. It is an object of the present invention to provide a substrate with an antireflection film which has an antireflection effect by colorizing such an insulating thin film.

[Structure of Invention]

In order to achieve the above-mentioned object, the present invention provides a translucent substrate, a translucent thin film layer made of an insulating metal oxide disposed on the substrate, and a translucent thin film layer disposed on the translucent thin film layer. It is characterized by comprising a conductor pattern layer of Al and an antireflection film formed by coloring the translucent thin film layer facing the conductor pattern layer by heat treatment.

[Work]

External light that has entered the translucent substrate enters the colored antireflection layer and is absorbed and attenuated by the antireflection layer, but part of it is reflected at the interface with aluminum and travels outside the substrate. At this time, a part is reflected at the interface between the substrate and the antireflection layer and absorbed by the antireflection layer.

Further, if the thickness of the antireflection film is set to an appropriate value, the reflected light at the aluminum interface interferes with the light reflected at the interface between the substrate and the antireflection layer and weakens each other, so The strength will be further reduced.

Furthermore, there is also light that is reflected by the surface of the substrate and absorbed in the substrate when the reflected light exits the substrate.

〔Example〕

 The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment in which the substrate with an antireflection film of the present invention is applied to a front emission type fluorescent display tube.

The structure of the front emission type fluorescent display tube is translucent, and the translucent substrate 1 is a part of the envelope group so that the light emission in the envelope can be observed through the substrate. A glass substrate is an example of the transparent substrate 1. A transparent thin film layer 2 of metal oxide is provided on the inner surface of the substrate 1. The metal oxide may be the thin film layer 2 which is transparent in the state of a thin film but has a light-transmitting property with some color. This translucent thin film layer 2 becomes an oxygen-deficient metal oxide when it is heat-treated together with an aluminum conductor pattern layer 3 described later, and the translucent thin film layer becomes colored and changes into a colored thin film layer. Is. Examples of metal oxides having such an action include titanium oxide, tungsten oxide, molybdenum oxide, vanadium oxide, niobium oxide and the like. This is the case where titanium oxide is used in this embodiment. The light-transmitting thin film layer 2 of titanium oxide formed on the entire inner surface of the substrate 1 is as thin as 500 to 600 Å and thus almost colorless and transparent. Anode conductor in the shape of a mesh or stripes made of aluminum on the surface of the translucent thin film layer 2.
3a and a wiring conductor 3b connected to the external lead terminal from the anode conductor 3a are formed by patterning, and these are collectively formed as a conductor pattern layer 3. The transparent thin film layer 2 facing the conductor pattern layer 3 is changed into a colored transparent thin film layer by heat treatment to form an antireflection film 2a.

Next, the black insulating layer 4 is disposed on the substrate except the anode pattern portion including the anode conductor 3a. The phosphor 5 is applied to the anode pattern portion to form the substrate with the antireflection film of the present invention.

In order to make a fluorescent display tube using this substrate with an antireflection film, a grid 6 is arranged at a certain interval from the phosphor layer 5 of the substrate with an antireflection film, and further at a certain interval from the grid 6. The filament cathode 7 is arranged in a stretched manner, and the electrodes and the like are covered with a container portion (not shown) and sealed to the substrate,
After the gas in the container is exhausted, the container is sealed in a high vacuum state to complete the fluorescent display tube.

Next, a method for manufacturing the antireflection substrate of the present invention will be described.

A thin film forming solution containing a few percent of an organic metal and containing a vehicle, a solvent, or the like is uniformly applied to one surface of a transparent substrate 1, for example, a transparent glass substrate. An organic titanium compound is an example of the organic metal. Specific examples of the organic titanium compound include tetraalkoxytitanium compounds such as tetraisoproxy titanium (TPT) and tetra-n-butoxy titanium (TBT).

In addition, as a compound group of tetraalkoxytitanium polymers, tetraisopropoxytitanium decamer, tetra-
There are dimers, tetramers, heptamers and decamers of n-butoxy titanium.

Further, as a titanium acylate compound group, tri-n-
There is a tetramer of butoxy titanium monostearate, polyhydroxy titanium stearate.

Furthermore, as titanium chelate compounds, diisoproxyl bis acetylacetonato titanium (TAA), di-n-butoxy bis (triethanol aminato) titanium (TAT), tetrakis (2-ethylhexanediolato) titanium ( TOG), dihydroxy bis (lactato)
There are titanium (TLA) etc.

Such an organotitanium compound is generally a liquid itself or is soluble in an organic solvent, and thus can form a liquid thin film forming liquid. This thin film forming liquid can be evenly applied to the back surface of the glass substrate 21 by the roll coater 20 as shown in FIG.

The glass substrate 21 is transferred horizontally as shown by the alternate long and short dash line in FIG. 4, but the upper end of the transfer guide roller 22 is adjusted to be lower than the upper end of the coating roller 23.
When the tip comes to the uppermost part of the coating roller 23, the transfer roller 22 stops, and the glass substrate 21 stops at an angle as shown by the solid line in FIG. Then, the lifting prevention ring 24 descends to come into contact with the glass substrate 21 and press the glass substrate 21 against the coating roller 23. The coating roller 23 is a thin film forming liquid 25.
Since it rotates clockwise in the pan 26 containing the liquid, the thin film forming liquid adheres to the coating roller 23 and is drawn out. Since the glass substrate 21 acts as a stopper, the thin film-forming liquid thus drawn out is stored in the wedge-shaped space between the glass substrate 21 and the coating roller 23. After a lapse of a fixed time after the glass substrate 21 is stopped, that is, when a predetermined amount of the thin film forming liquid 25 is accumulated, the glass substrate 21 is transferred by the transfer roller 22 and the coating roller 23.

The thin film forming liquid 25 is attached to the back surface of the glass substrate 21 by the method described above.

The glass substrate 21 containing organic titanium so that the amount of TiO ₂ becomes 2% when changed to TiO ₂ and further uniformly adhering the thin film forming liquid 25 consisting of a vehicle and a solvent to the organic solvent, moisture and the like in the drying process. After evaporation to 500 ~ 600 ℃ in the firing process
After holding for 10 minutes, it becomes a thin film of titanium oxide (TiO ₂ ).
The film thickness of this titanium oxide thin film is 500 to 600Å, and the refractive index must be 2.1 or more.

Next, aluminum, which is a conductive metal, is deposited on the titanium oxide thin film by a known deposition means such as a sputtering method or a vapor deposition method. The thickness of the deposited aluminum thin film is about 1.1μ
It is the mth place. A resist is applied to the surface of the aluminum thin film 3, the resist layer is exposed to pattern the conductor pattern, and then the aluminum in the unnecessary portion is dissolved by etching to form a conductor pattern. That is, a conductor pattern is formed of aluminum on the titanium oxide thin film 2 by means of photolithography.

Next, the anode segment is patterned by the black insulating layer 4 whose main component is the low melting point frit glass.

That is, the black insulating layer 4 is formed by the screen printing method on the entire surface except for the anode segment portion forming the phosphor layer 5.

Next, the black insulating layer 4 is fixed by a firing process, and the titanium oxide layer in contact with the aluminum conductor pattern 3 is colored. The color to be colored is blue. The firing temperature in this firing step is 520 ℃ ~ 600 ℃,
The firing time is held for about 10 to 20 minutes.

It is considered that the reason why blue color is formed by such heat treatment is as follows.

First, a light-transmissive thin film layer of a metal oxide, that is, a titanium oxide layer in this embodiment contains organic titanium, which is an organic metal, in the order of several percent, and becomes 500 to 600 Å after baking a thin film forming liquid consisting of a vehicle and a solvent. After applying it thinly in air,
When baked at 0 to 600 ° C, only titanium oxide is formed on the substrate. Aluminum is deposited on the titanium oxide layer
When heat-treated at 520 to 600 ° C, aluminum in contact with titanium oxide takes oxygen of titanium oxide and oxidizes to become aluminum oxide. Titanium oxide whose oxygen is taken by aluminum is reduced to oxygen-deficient titanium oxide.

It is speculated that the formation of oxygen-deficient titanium oxide in this manner causes the transparent titanium oxide layer to become colored.

A titanium oxide thin film with a thickness of 500 to 600 Å is suitable because the reflectance is small, but if the film thickness is 500 Å or less, the colored layer is too thin to absorb light and the reflectance is high. Also, when the film thickness is 600 Å or more, the reflected light at the aluminum interface and the reflected light at the interface between the substrate and the antireflection layer are less likely to interfere with each other, and the mutual weakening action is reduced, and the reflectance is also large.

In addition, it was necessary for the titanium oxide thin film to have a refractive index of 2.1 or more, but if this refractive index is 2.1 or less, discoloration occurs but the reflectance is large, and the antireflection effect is small. all right.

The temperature at which the titanium oxide layer provided with the aluminum layer is fired and discolored is 520 ° C to 600 ° C, but if it is 520 ° C or less, the reducing action of titanium oxide is not sufficiently performed, and the light blue color and reflection Preventive effect is also small. The firing temperature is 60
Above 0 ° C, the glass substrate is softened and the accuracy as a substrate deteriorates, making it unusable. If the substrate does not soften even at 600 ° C or higher, the firing temperature may be 600 ° C or higher, but if it rises to 650 ° C or higher, aluminum will melt and cause deformation, so it is necessary to perform firing at a temperature below that at which aluminum does not deform. Becomes

The antireflection action of the substrate with antireflection film formed by the above method will be described with reference to FIG.

Incident light A ₁ of the substrate 1 is part of the light A ₂ that enters the inside of the substrate 1 and part of the light A ₂ is reflected light A ₃ on the surface of the substrate 1 and exits to the outside. The light A ₂ incident on the substrate 1 is divided into light A ₄ incident on the antireflection film 2a and light A ₅ reflected on the substrate 1 at the interface between the substrate 1 and the antireflection film 2a. The light A ₄ incident on the antireflection film is reflected at the interface of the aluminum conductor pattern and becomes reflected light A ₆ which travels toward the outer side of the substrate 1, but is further reflected at the interface between the antireflection film 2a and the substrate 1. Some of the light is reflected to the side and is absorbed by the antireflection film 2a, but a part of the light goes out from the substrate 1.
However, the reflected light A ₆ reflected by the aluminum surface is absorbed by the antireflection film 2a and the glass substrate 1, but a part thereof goes out of the substrate 1. Then, another incident light B interferes with the light reflected at the interface between the substrate 1 and the antireflection film and the reflected light A _6, and weakens each other. Therefore, the incident light is 100%
Then, the reflected light becomes 40% or less.

FIG. 5 is a graph showing the relationship between the wavelength of light and the reflectance. For comparison, the solid line shows the reflectance of the substrate having aluminum coated on the substrate without the antireflection film, but the reflectance is 97-98%. The substrate with an antireflection film of the present invention has a wavelength of 400 nm near 4 nm.
It is 0%, and the reflectance gradually decreases up to around 650 nm, the minimum value is 22%, and then gradually rises to 800 nm.
It was around 23%.

〔The invention's effect〕

As described above, in the antireflection film-coated substrate of the present invention, the antireflection film in which the metal oxide thin film layer is colored is provided between the translucent substrate and the conductor pattern made of a conductive metal. Therefore, the reflectance can be lowered by the interference effect and the absorption effect, and when used in a fluorescent display tube, the visibility of the display section is good even under high illuminance.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a fluorescent display tube using a substrate with an antireflection film of the present invention, FIG. 2 is a sectional view illustrating a reflection mechanism of an incident light beam, and FIG. 3 is a conventional antireflection coating. FIG. 4 is a cross-sectional view of a fluorescent display tube with a film, FIG. 4 is a cross-sectional view of a roll coater to which the antireflection film of the present invention is applied, and FIG. 5 is a graph showing the relationship between wavelength and reflectance. 1 ... transparent substrate, 2 ... transparent thin film layer of metal oxide,
2a ... Antireflection film, 3 ... Conductor pattern layer

Claims (2)

[Claims] 1. A translucent substrate, a translucent thin film layer made of an insulating metal oxide deposited on the substrate, and an Al conductor pattern layer disposed on the translucent thin film layer. A substrate with an antireflection film, comprising: an antireflection film obtained by colorizing only the translucent thin film layer facing the conductor pattern layer by heat treatment. 2. The substrate with an antireflection film according to claim 1, wherein the insulating metal oxide is one selected from titanium oxide, tungsten oxide, molybdenum oxide, vanadium oxide, and niobium oxide.