JPH11162348A - Phosphor film forming method, phosphor film forming liquid, and phosphor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the residual of sulfur component in a phosphor film in a slurry method of forming phosphor film. SOLUTION: A washed glass board is formed with the predetermined pattern of an ITO film, and a pre-coating film is formed thereon. The pre-coating film is coated with the slurry liquid for blue color phosphor film containing the blue color emitting phosphor (Y2 SiO5 Ce), photosensitive material, dispersant, pure water and WO3 , and it is dried so as to form a coating film at 1.2 mg/cm<2> . The WO3 content is set at 0, 0.3, 1, 3, 5, 10 wt.% in relation to the phosphor. The coating film is exposed, and developed with water. A phosphor film having a desirable pattern is thereby obtained. A result of quantitative analysis of the sulfur content of the phosphor film is showed. Effect of reduction of the residual of sulfur is confirmed in a range at 0.3-10 wt.% of WO3 , and especially a remarkable effect is recognized at 1 wt.% or more, and the effect becomes nearly zero at 3.0 wt.% or more. The optimal value of the WO3 added variable is 1-3 wt.-%. In the case where this phosphor film is used for display element, amount of sulfur scattered at the time of irradiating electron beams to the phosphor film is reduced, and lowering of the emission of a negative electrode due to the contamination by sulfur is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor film having a predetermined pattern by selectively exposing a coating film of a phosphor film forming liquid containing a phosphor and a photosensitive material, developing the coating film, and baking it. More particularly, the present invention relates to a phosphor film forming solution and a phosphor film related to such a phosphor film forming method.

[0002]

2. Description of the Related Art FIG. 3 shows a Spindt-type field emission cathode (F
FIG. 1 is a cross-sectional view illustrating a general structure of a field emission display (Field Emission Display, abbreviated as FED) 2 having an electron emission cathode (abbreviated as FEC) 1 as an electron source. The insulating rear substrate 3 and the insulating and translucent front substrate 4 face each other at a predetermined minute interval. Although not shown, a gap between the outer peripheral portions of the substrates 3 and 4 is filled with a spacer member also serving as a sealing material, thereby forming a thin envelope as a whole. The inside of the envelope is kept in a high vacuum state.

[0003] Inside the envelope, a field emission cathode 1 (FEC1) is formed on the inner surface of the rear substrate 3. First, a cathode conductor 5 is formed on the inner surface of the back substrate 3. An insulating layer 6 is formed thereon, and the insulating layer 6
The gate electrode 7 is formed thereon. Gate electrode 7
A hole 8 is formed in the insulating layer 6 and the cathode conductor 5 is exposed at the bottom of the hole 8. On the cathode conductor 5 in the hole 8, a cone-shaped emitter 9 is formed. The tip of the emitter 9 reaches the height of the gate electrode 7. The cathode conductor 5 and the gate electrode 7 are formed in a number of strips arranged at predetermined intervals. The cathode conductor 5 and the gate electrode 7 form a matrix orthogonal to each other, and electrons can be emitted by selecting an emitter 9 (group) at an arbitrary intersection of the two electrodes.

An anode 10 serving as a display unit is formed on the inner surface of the front substrate 4 inside the envelope.
First, a transparent anode conductor 11 is formed on the inner surface of the front substrate 4. A phosphor film 12 is formed thereon.

[0005] The electrons emitted from the FEC 1 strike the phosphor film 12 of the anode 10 to emit light. FE
By driving the C1 in a matrix, the solid anode 1
The 0 phosphor film 12 can emit light in an arbitrary pattern such as a character or a figure.

In the FED 2, it is known that the surface function of the emitter 9 changes the work function of the substance constituting the emitter 9 and consequently deteriorates the emission. If the phosphor material is a sulfide-based material, a sulfur component is scattered by irradiation with an electron beam and contaminates the surface of the emitter. Therefore, an oxide-based phosphor is used in the FED.

Various methods such as a printing method, an electrodeposition method, a photo-adhesion method, and a slurry method are used as a method for forming the anode phosphor film in the FED. In the slurry method, a phosphor film forming solution containing a phosphor and a photosensitive material is applied to a substrate or the like to form a coating film, which is selectively exposed to light, developed, and baked to form a predetermined pattern. This is a method of forming a phosphor film. This method is excellent as a method for forming a phosphor film in a fine pattern. In particular, in a full-color FED, this slurry method is suitable for patterning a phosphor film.

As a photosensitive material of the phosphor film forming solution used in the slurry method, polyvinyl alcohol (PVA) is generally used.
And an aqueous solution of a photosensitive resin in which ammonium bichromate (ADC) is mixed. Cr contained in the ADC diffuses into the surface layer of the phosphor particles in the air baking step, and causes a decrease in the luminous efficiency of the surface layer of the phosphor particles. That is, Cr is a so-called killer component. In particular, FED and VFD (Vacuum Fluoresc) using medium or low speed electron beams with a shallow electron beam penetration depth
ent Display (fluorescent display tube), the luminous efficiency is greatly reduced.

Therefore, a slurry method (PVA-SbQ method) using a photosensitive resin PVA-SbQ having PVA as a main chain and having a styrylpyridinium group (abbreviated as SbQ) as a photosensitive group in a side chain has been proposed by FED or VFD. And the like. In the PVA-SbQ method, AD
Since C is not used, the contamination of the phosphor by Cr can be prevented, and the luminous efficiency due to medium- and low-speed electron beam excitation is not impaired.

[0010]

However, the above P
In VA-SbQ, sulfonic acid as a constituent material contains sulfur. Most of this sulfur is thermally decomposed by baking in air after patterning, but an extremely small amount (several tens of μg / b or tens of ppm) of sulfur remains on the phosphor particle surface. Sulfur remaining on the surface of the phosphor particles is decomposed and scattered by irradiation with an electron beam during light emission driving after completion of the display element, and contaminates FEC as an emission source. It is possible to reduce the residual amount of sulfur by increasing the atmospheric firing temperature, but the heating temperature is limited to about 600 ° C due to the material limitation of the glass substrate constituting the front substrate and the like. It cannot be removed.

In order to reduce the residual sulfur, it is conceivable to lower the amount of sulfur contained in the original photosensitive material. However, this leads to a decrease in the SbQ introduction rate, which impairs the patterning property of the phosphor film. This is not suitable for pattern formation of a full-color phosphor film or the like that requires particularly high resolution.

According to the present invention, when a phosphor film is formed by a slurry method having a high patterning property, a sulfur component does not remain in the phosphor film. The purpose of the present invention is to provide a method that can prevent the above.

[0013]

According to a first aspect of the present invention, there is provided a method of forming a phosphor film, wherein a phosphor film forming solution containing a phosphor and a photosensitive material is applied on a substrate to form a coating film. A method for forming a phosphor film having a predetermined pattern by forming the coating film into a predetermined pattern by developing after selectively applying exposure to the coating film, and baking the coating film. Further, a metal oxide having a catalytic action to efficiently oxidize the residue during firing is added to the phosphor film forming liquid.

According to a second aspect of the present invention, there is provided a method of forming a phosphor film according to the first aspect, wherein the metal oxide comprises a group consisting of WO ₃ , V ₂ O ₅ , and MoO _3. Or at least one substance selected from the group consisting of:

According to a third aspect of the present invention, in the method of forming a phosphor film according to the first aspect, the addition amount of the metal oxide is 0.3% by weight with respect to the phosphor. -10 wt%.

According to a fourth aspect of the present invention, there is provided a method of forming a phosphor film, wherein a phosphor film forming solution containing a phosphor and a photosensitive material is applied on a substrate to form a coating film, and the coating film is selectively formed on the substrate. A method for forming a phosphor film having a predetermined pattern by performing development after exposure, forming the coating film in a predetermined pattern, and baking the coating film, wherein a predetermined The method is characterized in that a metal oxide solution having a catalytic action to efficiently oxidize residues during firing is applied to the coating film formed in a pattern, and then the firing is performed.

According to a fifth aspect of the present invention, in the method of forming a phosphor film according to the first, second, third, or fourth aspect, the phosphor is made of Y ₂ SiO ₅ : Ce, Z.
nGa ₂ O ₄ Mn, SrTiO ₃ : Pr, Y ₂ O ₃ : E
It is one or more phosphors selected from the group consisting of u.

The phosphor film forming liquid according to claim 6 is
It is characterized by containing a phosphor, a photosensitive material, and a metal oxide having a catalytic action to efficiently oxidize residues during firing.

The phosphor film described in claim 7 is obtained by selectively exposing a coating film of a phosphor film forming solution containing a phosphor and a photosensitive material, and then developing the coating film into a predetermined pattern. The phosphor film formed and fired to form a predetermined pattern is characterized by including a metal oxide having a catalytic action to efficiently oxidize the residue during the firing.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In this example, the accelerating voltage is 0.1 to 2.
The present invention relates to a method of forming a full-color FED phosphor film that emits light with high luminance by an electron beam of 0 kV. The basic configuration of the FED is the same as that described with reference to FIG. The phosphor film of the anode is RGB
And a predetermined pattern composed of the three colors described above, and a display signal is provided for each color.

The glass substrate serving as the rear substrate of the envelope of the FED is cleaned. First, normal wet cleaning using an acid, an alkali, pure water or the like is performed. Next, dry cleaning using ultraviolet rays or the like is performed.

On the surface of the cleaned substrate, an ITO (Indium Tin Oxide) film as a transparent conductive film is formed by a sputtering method. The thickness of the ITO film is 0.1 to 0.15 μm,
The sheet resistance at this time is several tens Ω / □. Next, the ITO film is patterned into a shape of an anode conductor by using a photolithography method.

Next, a precoat film is formed on the patterned ITO film. First, 0.2wt% PV
A precoat solution, which is an aqueous solution obtained by adding a surfactant to A, is spread on the ITO film by a spinner at 1000 rpm for 10 seconds to form a film. After film formation, 150
Dry at 5 ° C. for 5 minutes. Through the above steps, a uniform precoat film having a thickness of 0.05 μm can be obtained on the ITO film or the glass substrate.

Next, the step of depositing the phosphor film will be described by taking a blue (B) phosphor as an example. The composition of the blue phosphor film slurry is shown below. Blue-emitting phosphor _{(Y 2 SiO 5: Ce)} 28.00g photosensitive material (SPP-B) 22.40g dispersing agent 1 0.84 g Dispersant 2 0.84 g Dispersant 3 0.84 g of pure water 46.80g WO ₃ 0.28g

In the above composition, the amount of WO ₃ is 1.0 wt% based on the phosphor. In addition to this sample, WO ₃
0, 0.3, 3, 5, 10 wt.
% Samples were prepared and used. In the above composition, the photosensitive material is a 10 wt% aqueous resin solution, and the dispersant is 0.5 wt.
It is an aqueous solution of wt%.

This slurry liquid has a viscosity of 11 mPas, and forms a slurry coating on the precoat film under the following forming conditions. Coating conditions: spin speed 200 rpm, 10 seconds Drying conditions: 70 ° C., 2 minutes According to the above forming conditions, the blue phosphor film slurry liquid is:
A coating film having a screen weight of ² mg / cm ² was formed.

Next, an exposure process of irradiating the coating film with ultraviolet rays in an arbitrary pattern is performed. At this time, among the coating films,
The part irradiated with the ultraviolet light is cured by light and becomes insoluble in water. The exposure amount at this time was 30 mJ / cm ² .

Next, the coating film of the blue phosphor film slurry liquid after the exposure treatment is developed with water. The development conditions are as follows. Pure water temperature: 43 ° C. Spray pressure: 2.0 kgf / cm ² Development time: 40 seconds Spray nozzle: 110 ° flat nozzle

Fluorescence of an arbitrary pattern depending on the developing conditions
A body film can be formed. Phosphor film of red light emitting phosphor, emitting green light
Regarding the phosphor film of the photophosphor under the same conditions as in the case of blue
Can be formed. At this time, the coating film of the slurry liquid for the red phosphor film
1.2 mg / cm ^TwoFor green phosphor film
The film weight of the slurry liquid coating is 1.3 mg / cm.^TwoSo
Was.

Next, a coating film of the slurry liquid for a phosphor film is formed for each of the required R, G, and B colors.
The substrate is baked in the air under the condition of 0 minutes to complete the phosphor film forming step.

The quantitative analysis of the amount of sulfur contained in the phosphor film obtained in the above steps was performed. The results are shown in FIG. In FIG. 1, the horizontal axis represents the amount of WO ₃ added to the slurry,
The vertical axis is the sulfur residue. As can be seen from FIG.
_By adding ₃ to the slurry liquid, the residual amount of sulfur can be reduced. WO ₃ is effective even in very small amount, but the effect was confirmed in a range of 0.3～10Wt%,
In particular, the effect is remarkable at 1 wt% or more, and the residual sulfur amount becomes almost 0 at 3.0 wt% or more. This WO ₃
Is a non-luminous substance, so it does not make sense to add more than necessary. As shown in FIG. 1, since the WO ₃ is 3 wt% or more remains at almost sulfur residual amount 0, the optimum value of the amount of WO ₃ in the present embodiment can be said to be 1 to 3 wt%.

FIG. 2 is a FED having a phosphor film of the present invention by the slurry liquid in which WO ₃ was added 3 wt%, WO ₃
9 shows the results of each life test of a conventional FED provided with a conventional phosphor film using an unadded slurry liquid. As is apparent from this data, the present invention has a longer life than the conventional example, and the present invention shows that the cathode is less contaminated by sulfur remaining in the phosphor.

Since the amount of residual sulfur in the phosphor film according to the present embodiment is low, if this is used as a light-emitting portion of the anode of a FED or VFD, the amount of sulfur scattered even if it is hit by electrons at the time of driving is lower than in the conventional case. Thus, it is possible to prevent a reduction in emission on the cathode side due to contamination by sulfur. In particular, since the FED is greatly affected by the contamination of the emitter, the effect of the phosphor film formed as in this embodiment is great.

WO ₃ has a catalytic effect of oxidizing and burning more effectively to remove the residue from the phosphor film when baking the coating film of the slurry liquid. Substances other than WO ₃ can be used as long as they have such an effect.
For example, V ₂ O ₅ , MoO _{3 and the} like can be used. The method used is substantially the same as the case of WO _3.

The phosphor to which this embodiment can be applied is the above-mentioned Y.
₂ SiO _5: other Ce, for example, ZnGa ₂ O ₄ Mn, S
rTiO ₃ : Pr, Y ₂ O ₃ : Eu and the like can also be mentioned.

[0036]

According to the present invention, in the preparation of a phosphor film by the slurry method, a metal oxide having a catalytic action to efficiently oxidize the residue at the time of firing is added.
The amount of residual sulfur in the obtained phosphor film can be reduced, and when this is used for a light emitting / display element, the amount of sulfur scattered during electron beam irradiation can be reduced, thereby preventing a reduction in cathode emission due to sulfur contamination. be able to.

[Brief description of the drawings]

FIG. 1 shows the amount of WO ₃ added in an embodiment of the present invention;
4 is a graph showing a relationship with the amount of residual sulfur in the obtained phosphor film.

FIG. 2 shows life test results of an FED provided with a phosphor film of the present invention using a slurry liquid containing 3 wt% of WO ₃ and a conventional FED provided with a conventional phosphor film provided with a slurry liquid containing no WO _3. FIG.

Fig. 3 Spindt-type field emission cathode (Field Emission)
1 is a cross-sectional view illustrating a general structure of a field emission display (abbreviated as FED) having Cathode (abbreviated as FEC) as an electron source.

Claims (7)

[Claims] 1. A coating film is formed by applying a phosphor film forming solution containing a phosphor and a photosensitive material on a substrate to form a coating film. The coating film is selectively exposed to light and developed to develop the coating film. In a phosphor film forming method of forming a phosphor film of a predetermined pattern by baking the coating film, the residue is efficiently oxidized in the phosphor film forming liquid at the time of baking. A method for forming a phosphor film, comprising adding a metal oxide having a catalytic action. 2. The method according to claim 1, wherein the metal oxide is WO ₃ , V ₂ O ₅ ,
Method of forming a phosphor film of claim 1 wherein the one or more substances selected from the group consisting of MoO _3. 3. The method for forming a phosphor film according to claim 1, wherein the amount of the metal oxide added is in the range of 0.3 to 10% by weight relative to the phosphor. 4. A phosphor film forming solution containing a phosphor and a photosensitive material is applied on a substrate to form a coating film, and the coating film is selectively exposed to light and developed to develop the coating film. In the method of forming a phosphor film of a predetermined pattern by forming the phosphor film of a predetermined pattern by baking the coating film, the coating film formed in the predetermined pattern by the development, the residue during firing A method for forming a phosphor film, comprising applying a solution of a metal oxide having a catalytic action to efficiently oxidize, followed by baking. 5. The method according to claim 1, wherein the phosphor is Y ₂ SiO ₅ : Ce, Z.
nGa ₂ O ₄ Mn, SrTiO ₃ : Pr, Y ₂ O ₃ : E
5. The method for forming a phosphor film according to claim 1, which is at least one phosphor selected from the group consisting of u. 6. A phosphor film forming solution containing a phosphor, a photosensitive material, and a metal oxide having a catalytic action to efficiently oxidize residues during firing. 7. A coating film of a phosphor film-forming liquid containing a phosphor and a photosensitive material is selectively exposed to light and then developed to form the coating film into a predetermined pattern, which is baked to obtain a predetermined pattern. The phosphor film formed in the pattern described above, further comprising a metal oxide having a catalytic action to efficiently oxidize the residue during the firing.