JPS61267229A - Formation of fluorescent screen in fluorescent character display tube - Google Patents

Abstract

PURPOSE:To automate formation of fluorescent screen by floating the fluorescent particles in container and charging thereafter flying toward a segment electrode row and adhering to the exposed portion of segment electrode row formed on a substrate. CONSTITUTION:Upon rotation of fur brush 13, fluorescent particles 11 are held between the brush and scooped. Since the brush is handled at the scattering section 14, the fluorescent particles are scattered from the brush and float 11A in the container 12. Upon application of voltage onto the charger 15 and the segment electrode 2, the floating particles are charged positively. The charged particles are electrostatically attracted to the exposed portion 2b of negative segment electrode and fly to be adhered onto the exposed portion thus to form a fluorescent screen 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for forming a phosphor screen in a fluorescent display tube.

(Prior Art) In a fluorescent display tube, a fluorescent screen is formed on a large number of segment electrodes arranged in one or more rows in one direction, and this is sealed in a vacuum container together with a hot cathode, and heat is emitted from the hot cathode. While generating electrons, a positive voltage is selectively applied to the segment electrodes depending on the information to be displayed to attract thermoelectrons to the selected segment electrodes, which are emitted when they collide with the phosphor screen. Information is displayed using fluorescence, and they are already well known as barcode display tubes and phosphor dot array tubes.

First, referring to FIG. 11, an outline of a fluorescent display tube will be explained using a fluorescent dot array tube as an example.

In FIG. 11, reference numeral 60 indicates glass, ceramic,
A substrate made of resin or the like is shown. A series of segment electrodes 61 are arranged in a row in the longitudinal direction of the substrate 60, and each segment electrode 61 has a fluorescent screen 62.
is formed. The size of each phosphor screen is 4
Although the phosphor screen is extremely minute, measuring from 0 x 40 μm to 50 x 50 μm, the dimensions of the phosphor screen are shown larger than the other members in FIG.

3. On both sides of the phosphor screen arrangement of the substrate 60, an insulating layer 63°6 is provided.
3 are formed along the longitudinal direction of the substrate, and on these,
Grid electrodes 64 and 64 are formed, respectively.

In FIG. 11, reference numeral 65 indicates a tungsten wire as a hot cathode stretched in the longitudinal direction of the substrate, the surface of which is coated with an electron emissive substance such as Ba5rO. Further, reference numeral 66 is a face member made of a transparent material such as glass, and is integrated with the substrate side as shown in FIG. 12.

Thus, the substrate 60, the insulator layers 63, 63, the grid electrodes 64, 64, and the face member 66 form a closed space, and within this space, the segment electrodes 61. A phosphor screen 62 and a hot cathode 65, 65 are confined by the phosphor layer. The closed space is highly evacuated.

When a suitable voltage is applied to the grid electrodes 64, 64 and an alternating current of several tens of milliamps is passed through the hot cathodes 65, 65, the hot cathodes 65, 65 are heated by Joule heat and emit thermoelectrons. In this state, when a positive voltage is applied to one of the segment electrodes 61 to make it a positive potential, the thermoelectrons are attracted to the electrode portion of the segment electrode at a positive potential, and when sucked into the electrode portion, the phosphor screen 62 excites the energy state of the fluorescent substance. The excited fluorescent substance emits fluorescence when returning to the ground state. This fluorescence is observed through the face member 66.

Such a phosphor dot array tube is used as a part of the optical system of an optical printer or as a bar code display tube.

One of the methods for forming a phosphor screen is an electrodeposition method using electrophoresis. In this method, in the electrode formation step, a segment electrode array consisting of strip-shaped electrodes is formed on the substrate by photoetching, and in the insulating layer formation step, a part of the electrode is exposed by screen printing, and the A layer of thick film insulating glass is formed on the surface of the substrate including the electrodes, and this is fired. Next, only a portion of the exposed electrode is exposed, and the surface of the substrate including the electrode is covered with a photoresist layer. Then, in the phosphor screen forming step, the above substrate is
It is immersed in a dispersion liquid in which phosphor particles are dispersed, facing a counter electrode at a predetermined distance, and a voltage is applied between the segment electrode array and the counter electrode.

The phosphor particles in the dispersion liquid move toward the segment electrodes due to the electric field formed between the two electrodes, and adhere to the exposed electrode portions to form a phosphor screen.

After drying and fixing this phosphor screen, the photoresist layer is removed.

By the way, in the above-mentioned electrodeposition method, it takes 2 minutes to 2 minutes for the phosphor particles to adhere to the segment electrodes in a predetermined amount (predetermined film thickness).
There was a problem that it took a long time of 10 minutes.

Further, it requires a step of dipping the substrate in the dispersion liquid and taking it up, and also requires relatively high-precision positioning between the segment electrode and the counter electrode, resulting in a problem of high cost. Furthermore, if the conductivity of the phosphor particles forming the phosphor screen is low, there is another problem in that sufficient brightness cannot be obtained.

(Objective) The first object of the present invention is to provide a novel method for forming a phosphor screen in a fluorescent display tube, which can reduce manufacturing cost and automate the process. Another object of the present invention is to provide a method for forming a phosphor screen in a fluorescent display tube, which can be automated and provide sufficient luminance.

(Structure) In the phosphor screen forming process, the present invention applies a predetermined charge to the segment electrodes, causes the phosphor particles to be scattered and suspended in a container, and the scattered particles have a polarity opposite to that of the charge on the segment electrodes. by applying a charge of , and supplying the charged phosphor particles by flying them toward the exposed segment electrode array, so that the phosphor particles are electrostatically attached to the exposed segment electrodes. A method for forming a phosphor screen in a fluorescent display tube characterized by forming a phosphor screen, and applying a liquid containing trivalent aluminum ions to the segment electrode portion or the phosphor screen before or after forming the phosphor screen. A phosphor screen forming method is provided.

The present invention will be explained in detail below.

FIG. 1 shows the steps of the present invention, including an electrode forming step in which at least one row of electrodes made of a conductive material is provided on a substrate, and a substrate containing the electrodes in order to avoid contact between the grid electrode and the electrode. an insulating layer forming step of forming a segment electrode row by forming an insulating layer on the surface to expose a part of the electrodes along the electrode arrangement direction; and covering the insulating layer and the segment electrode row with a photoresist layer. Thereafter, a resist layer forming step is performed in which only the photoresist layer on each segment electrode constituting the segment electrode row is removed to expose the segment electrode row, and a predetermined pattern is applied to the exposed segment electrode row. Applying an electric charge to scatter and suspend the phosphor particles in a container, and applying an electric charge of opposite polarity to the electric charge of the segment electrode array to the scattered particles,
A phosphor screen forming step of supplying charged phosphor particles by flying them toward the exposed segment electrode rows, and causing the phosphor particles to adhere to the exposed segment electrode rows to form a phosphor screen. and a phosphor screen forming step of applying a liquid containing trivalent aluminum ions to the exposed portions of the segment electrodes or the formed phosphor screen before or after forming the phosphor screen.

and a photoresist layer removal step of removing the photoresist layer.

Each step will be explained in detail below.

Electrode Formation Step An electrode made of aluminum is formed on one surface of a substrate 1 made of, for example, a glass plate, as shown in FIG. 2(1), as indicated by reference numeral 2 in FIG. 2(2), by photoetching. As shown in FIG. 7, this electrode 2 has a width of approximately 50 μm.
The electrodes are formed in a row in the longitudinal direction of the substrate with an interval of 35 μm between adjacent electrodes, and the lead portions 2a of each electrode are drawn out to the left and right side edges of the substrate at alternate intervals.

Insulating layer forming process As shown in FIG. 2 (3), the substrate 1 including the strip-shaped electrodes 2 is made of, for example, lead glass and carbon and has a thickness of 10.
Cover with an insulating layer 3 of about 20 μm.

This insulating layer 3 is formed by a screen printing method and then
As shown in FIG. 2bJ), and the ends of the lead portions 2a are exposed.The exposed portions 2b are arranged in rows in the longitudinal direction of the substrate, and segment electrode rows are formed here.

Photoresist layer forming step As shown in FIG. 2(4), the insulating layers 3, the segment electrode array 2, and the substrate 1 are entirely coated with a photoresist layer 4. As the photoresist layer 4, for example, a negative type photoresist OMR-85r for fine processing is used.
A positive photoresist for microfabrication 0FPR-800 (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd. is used.

The photoresist layer 4 is prebaked at 85°C to 95°C for about 30 minutes.

Next, as shown in FIGS. 2(5) and 3, the photoresist layer 4 on the exposed portion 2b of each segment electrode is
As shown in a, the segment electrode array (the central part of the exposed part 2b) is removed in a dot shape.
Let it come out. The width of the dots 4a is controlled to be 40 to 50 .mu.m, and an example of a method for forming such dots will be explained with reference to FIGS. 4 and 5.

In FIG. 4, a laser beam generated by a laser beam generator 5 is guided to a scanning optical system 7 via a polarizer 6, and the photoresist layer 4 is polarized by this laser beam in a direction perpendicular to the arrangement direction of the segment electrodes. , exposure is performed by spot scanning at the electrode arrangement pitch. Thereafter, this layer is developed and rinsed to remove the layer in dots to form dots 4a. In this case, a positive type photoresist is used as the photoresist layer 4, and the portions hit by the laser beam are removed to expose the dot-shaped segment electrode arrays. In addition, in FIG. 4, a method of sliding a mirror or the like may be adopted without using the polarizer 6. Furthermore,
In FIG. 4, an adjusting means for adjusting the beam power may be provided between the laser beam generator 5 and the polarizer 6.

The shape of the dot 4a is not limited to the exact square shown in the figure, but may be circular or oval.

FIG. 5 shows a substrate 1 coated with a photoresist layer 4;
Dot pattern 8a with the same pitch as the arrangement pitch of electrode 2
A method is shown in which the photoresist layer is removed in dots by applying light from a light source 9 having an emission wavelength such as ultraviolet light after polymerizing the mask 8 formed with the photoresist layer. When the photoresist layer 4 is a positive type photoresist, a positive mask is used and the exposed portion is removed by development and rinsing to obtain the dots 4a. When the photoresist layer 4 is a negative type photoresist, a negative mask is used and the unexposed portions are removed by development and rinsing to form the dots 4.
get a. Note that the width of the exposed portion can be regulated by removing the photoresist layer 4 in a slit shape in the same direction as the arrangement direction of the segment electrodes to expose the exposed portion of the segment electrode array, without removing the photoresist layer 4 in a dot shape. You may.

Phosphor screen forming process As shown in FIG.
It is attached to the phosphor particle supply means 10 shown in the figure.

The phosphor particle supply means 10 includes a container 12 containing phosphor particles 11, a fur brush 13 rotatably disposed below the container, and a fur brush 13 stretched over the rotation locus of the brush. A scattering member 14 for scattering the phosphor particles attached to the brush and making them float in the container by handling the brush, and a corona stretched over a supply opening 12a formed on the upper side of the container. A charger 15 made of a discharge wire, a belt conveying means 16 that holds the substrate 1 and moves in the water direction while bringing the exposed portion 2b of the substrate close to the charger 15, and a high-voltage DC power supply 17 that applies negative polarity charges to the segment electrodes 2.

The belt conveying means 16 is rotated at a predetermined speed in the horizontal direction by a driving means (not shown), and as shown in FIG. 2(5) and FIG. The exposed portion 2b of the segment electrode array is positioned so as to directly face the charger 15 and pass through it at a predetermined interval. As shown in FIG. 8, when the substrate 1 is transported in a direction perpendicular to its longitudinal direction,
The opening -14=12a is provided to extend in a direction perpendicular to the plane of the drawing to have a length substantially equal to the length of the segment electrode array.

Further, the electrification charger 15 is formed to be slightly longer than the length of the segment electrode array. Note that in FIG. 8, the insulating layer 3 and photoresist layer 4 on the substrate 1 are not shown.

When the fur brush 13 rotates, the phosphor particles 1
1 is held between the brushes and scooped up.

The phosphor particles are scattered from the brush when the brush is handled by the scattering member 14, and are suspended in the container 12 as floating particles 11A. On the other hand, when a voltage is applied to the charger 15 and the segment electrode 2, the phosphor particles floating near the charger are positively charged. These charged phosphor particles are electrostatically attracted to the exposed portion 2b of the segment electrode of negative polarity and fly, and as shown in FIGS. 2(6) and 6, they adhere to the exposed portion. Fluorescent screen 1
form 8. At this time, phosphor particles slightly adhere to the surface of the photoresist layer 4 in the portion covering the electrode 2, and FIGS. 2(6) and 6 show that the phosphor particles adhere to the exposed portion. Only the body is shown.

The thickness of the phosphor screen 18 is adjusted to a desired thickness by appropriately setting the strength of the applied voltage and the moving speed of the belt conveying means 16.

FIG. 9 shows separate phosphor particle supply means. This example differs from the example shown in FIG. 8 in that the substrate 1 is moved in the horizontal direction, and correspondingly, the floating phosphor particles are guided downward and charged with a charger. The point is to electrify it. Therefore, members that perform the same functions are given the same reference numerals, and individual explanations thereof will be omitted.

The substrate on which the phosphor screen has been formed by the method described in FIGS. 8 and 9 proceeds to the next step.

FIG. 10 shows an example of an apparatus implementing the second invention. A feature of the present invention is that a liquid containing trivalent aluminum ions is applied before or after the phosphor particles are supplied to the exposed portion 2b. Belt conveyance means 16
A liquid application means 19 is arranged upstream of the phosphor particle supply means 10 in the direction of movement. This liquid application means uses aluminum nitrate (Al(No,)3.9H
20) isopropyl alcohol ((CH,)2CHO
It consists of a tank 21 that stores a liquid 20 dissolved in H), and an application roller 22 that is placed below this tank and rotates while impregnated with the liquid 20. Note that instead of using a coating roller as the liquid coating means, the liquid may be supplied directly from a tank to the substrate as a shower, or may be sprayed and coated using a pump and a nozzle.

The axial length of the application roller 22 is approximately equal to the length of the segment electrode array when the substrate 1 is conveyed in a direction perpendicular to the segment electrode array.

When the substrate is conveyed in the same direction as the longitudinal direction, the application roller only needs to have at least the width of the exposed portion 2b.

The phosphor particles 11 scattered and suspended in the container 12 are positively charged by the charger 15 and electrostatically attached to the exposed portion 2b. At this time, since the exposed portion 2b is coated with the liquid 20 containing trivalent aluminum ions Al''+, the electrical conductivity of the supplied phosphor particles can be increased.

Of course, the means for supplying the phosphor particles may be of the type shown in FIG.

In the example shown in FIG. 10, the liquid 20 is applied before the phosphor particles are supplied, but the liquid may be applied after the particles are supplied to form the phosphor screen. In this case, the liquid 20 is
Rather than using a roller coating method, it is more advantageous to use a non-contact shower type or low-pressure spray method because the phosphor screen will not be disturbed.

After the phosphor screen is dried and fixed, the substrate having the phosphor screen formed by the method described in FIG. 1θ is proceeded to the next step.

Photoresist Layer Removal Step As shown in FIGS. 2(6) and 6, the substrate 1 on which the phosphor screen 18 is formed is fired with, for example, oxygen plasma to peel and remove the photoresist layer.

When the photoresist layer 4 is removed, the insulating layers 3, 3 and the segment electrode array 2, which have been covered with the photoresist layer, are exposed, as shown in FIGS. 2(7) and 7. At this time, the phosphor particles adhering to the photoresist layer 4 are also removed as the layer is peeled off. Therefore, a phosphor screen 18 having the same size as the dot 4a is formed on each segment electrode 2. When this is observed with respect to the substrate 1, it can be seen that the phosphor screens 18 are arranged in an orderly dot-like manner.

(Effects) As described above, according to the present invention, phosphor particles are scattered and suspended in a container, and the scattered particles are charged and flown toward a segment electrode array to be transferred to a substrate. Since the phosphor dots are supplied and adhered to the exposed portions of the segment electrode rows formed in the phosphor dot array, the formation of the phosphor screen can be automated and the manufacturing cost of the phosphor dot array tube can be significantly reduced.

Furthermore, since a liquid containing trivalent aluminum ions is applied before or after forming the phosphor screen, the electrical conductivity of the phosphor particles increases, the deterioration of the phosphor screen over time is suppressed, and its luminance is stabilized.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the steps of the phosphor screen forming method of the present invention;
FIG. 2 is a process diagram showing a specific example of the same as the above in a cross-sectional view, FIG. 3 is a partial plan view for explaining the photoresist layer forming process, and FIGS. 4 and 5 show means for removing the photoresist layer. Block diagrams showing different examples, FIG. 6 is a partial plan view showing a state in which a phosphor screen is formed and the photoresist layer is not removed, and FIG. 7 is a partial plan view showing a state in which the photoresist layer is removed. FIG. 8 is a schematic sectional view showing an example of a phosphor particle supply means for implementing the phosphor screen forming method of the first invention, FIG. 9 is a schematic sectional view showing another example of the phosphor particle supply means, FIG. 10 is a schematic cross-sectional view showing an example of a phosphor particle supply means for implementing the phosphor screen forming method of the second invention;
FIG. 11 is an exploded perspective view showing a phosphor dot array tube as an example of a fluorescent display tube, and FIG. 12 is a sectional view of the same. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Segment electrode, 3... Insulating layer, 4... Photoresist layer, 4a... Dot, I
I...phosphor particles, IIA... suspended particles, I2...
- Container, 15... Charger, 17... DC power supply, 18... Fluorescent screen, 20... Liquid.

Claims (2)

[Claims] (1) In a fluorescent display tube, in the electrode forming step, at least one row of electrodes made of a conductive material is provided on the substrate, and in the insulating layer forming step, the electrodes are formed on the substrate surface including the electrodes along the direction in which the electrodes are arranged. forming a segment electrode array by forming an insulating layer that exposes a part of the segment electrode array, and in a photoresist layer forming step, the insulating layer and the segment electrode array are covered with a photoresist layer, and then the segment electrode array is formed. Only the photoresist layer on each segment electrode is removed to expose the segment electrode row, and in the phosphor screen forming process, a predetermined charge is applied to the segment electrode row, and the phosphor particles are scattered and suspended in the container. Then, a charge having a polarity opposite to that of the segment electrode row is applied to the scattered particles, and the charged phosphor particles are supplied by flying toward the exposed segment electrode row. , forming a phosphor screen by attaching phosphor particles to the exposed segment electrode rows, and removing the photoresist layer in a photoresist layer removal step to form a phosphor dot array. A method for forming a phosphor screen. (2) In a fluorescent display tube, in the electrode forming step, at least one row of electrodes made of a conductive material is provided on the substrate, and in the insulating layer forming step, the electrodes are formed on the substrate surface including the electrodes along the direction in which the electrodes are arranged. forming a segment electrode array by forming an insulating layer that exposes a part of the segment electrode array, and in a photoresist layer forming step, the insulating layer and the segment electrode array are covered with a photoresist layer, and then the segment electrode array is formed. Only the photoresist layer on each segment electrode is removed to expose the segment electrode row, and in the phosphor screen forming step, the phosphor particles are placed in a container while applying a predetermined charge to the segment electrode row. The particles are scattered and suspended, and a charge having a polarity opposite to that of the segment electrode row is applied to the scattered particles, and the charged phosphor particles are caused to fly toward the exposed segment electrode row. supplying phosphor particles to the exposed segment electrode rows to form a phosphor screen, and before or after supplying the phosphor particles, at least the substrate surface including the exposed segment electrodes. Alternatively, a phosphor screen characterized in that a liquid containing trivalent aluminum ions is applied to the formed phosphor screen, and in a photoresist layer removal step, the photoresist layer is removed to form a phosphor dot array. Formation method.