JPS61267228A - Formation of fluorescent screen in fluorescent character display tube - Google Patents

Abstract

PURPOSE:To uniform the thickness of fluorescent material layer and to automate formation of fluorescent screen by atomizing the liquid scattered with fluorescent particles then charging the mist and flying toward the segment electrode row thereafter feeding and adhering to the exposed portion of segment electrode row formed on the substrate. CONSTITUTION:Upon start of scattered liquid atomizing means 13, the scattered liquid 11 is atomized and sprayed as atomized/scattered liquid 11a through a nozzle 13a toward a liquid receiving member 14. Upon application of high positive voltage onto the corona discharge wire 15a, positive charges are provided to said liquid 11a. The charged liquid 11a (mist) will fly to the segment electrode side in accordance to the electrical field formed between the corona discharge wire 15a and the negative segment electrode and adhere to the exposed section 2b. Thereafter, the adhered liquid is dried to remove the liquid component thus to form the fluorescent screen 18 with residual fluorescent particles.

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. 10, the outline of a fluorescent display tube will be explained using a fluorescent dot array tube as an example.

In FIG. 10, reference numeral 50 indicates glass, ceramic,
A substrate made of resin or the like is shown. On the substrate 50, a series of segment electrodes 51 are arranged in a row in the longitudinal direction of the substrate, and each segment electrode 51 has a fluorescent screen 52.
is formed. The size of each phosphor screen is 4
The size of the phosphor screen is extremely small, such as 0 x 40 μM to 50 x 50 μM, but the size of the phosphor screen is shown larger than the other members in FIG.

An insulating layer 53.5 is provided on both sides of the array of phosphor screens on the substrate 50.
3 are formed along the longitudinal direction of the substrate, and on these,
Grid electrodes 54, 54 are formed respectively. In FIG. 1O, reference numeral 55 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 56 denotes a face member made of a transparent material such as glass, and is integrated with the substrate side as shown in FIG. 11.

Thus, the substrate 50, the insulator layers 53, 53, the grid electrodes 54, 54, and the face member 56 form a closed space, and within this space are the segment electrodes 51, the fluorescent screen 52 made of the phosphor layer, and the hot cathode 55. .55 is trapped. The closed space is highly evacuated.

When a suitable voltage is applied to the grid electrode 54.54 and an alternating current of several tens of milliamps is passed through the hot cathode 55.55, the hot cathode 55.55 is heated by Joule heat and emits thermoelectrons. In such a state, when a positive voltage is applied to one of the segment electrodes 51 to make it a positive potential, the thermoelectrons are attracted to the electrode portion of the segment electrode having a positive potential, and when sucked into the electrode portion, the phosphor screen 5
The energy state of the second fluorescent substance is excited. The excited fluorescent substance emits fluorescence when returning to the ground state. This fluorescence is observed through the face member 56.

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 forming step, a segment electrode array consisting of strip-shaped electrodes is formed on the substrate by photoetching, and in the insulating layer forming step, the τ portion 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 resist layer. Then, in the phosphor screen forming step, the substrate is immersed in a dispersion liquid in which phosphor particles are dispersed, facing the 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,
It adheres to the exposed electrode portion to form a fluorescent screen. After drying and fixing this phosphor screen, the resist 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 object of the present invention is to provide a novel method for forming a phosphor screen in a fluorescent display tube, which has a uniform thickness, can be automated at low manufacturing costs, and can obtain sufficient brightness. .

(Structure) In the method for forming a phosphor screen in a fluorescent display tube of the present invention, in the phosphor screen forming step, a predetermined charge is given to the segment electrodes, and a dispersion liquid in which phosphor particles are dispersed is applied to the segment electrode array. The atomized dispersion is atomized nearby, and the atomized dispersion is charged with a charge having a polarity opposite to that of the segment electrodes by a charging means disposed opposite to the exposed portion of the segment electrode row, thereby forming a charged atomized dispersion. The present invention is characterized in that a liquid is electrically flown and supplied toward the exposed segment electrode rows, and phosphor particles are attached to the exposed segment electrode rows to form a phosphor screen.

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. After that, the above-mentioned 1 step of resist layer formation 7 in which only the photoresist layer on each segment electrode constituting the segment electrode row is removed to expose the segment electrode row, and the exposed segment electrodes are A dispersion liquid in which phosphor particles are dispersed by applying a predetermined electric charge is atomized near the segment electrode array, and the atomized dispersion liquid is A charge having a polarity opposite to that of the segment electrode is applied, and the charged atomized dispersion is electrically flown and supplied toward the exposed segment electrode row, and the exposed segment electrode is The process consists of a phosphor screen forming process in which phosphor particles are attached in rows to form a phosphor screen, and a photoresist layer removing process in which the photoresist layer is removed.

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.
m strips, and are formed in a line in the longitudinal direction of the substrate with an interval of about 35 μm between adjacent electrodes, and lead portions 2a of each electrode are drawn out to the left and right side edges of the substrate every other time.

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. 7, the electrode part (hereinafter referred to as "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 FIG. 2 (5) and FIG. 2
The central part of b) is exposed again. The width of dot 4a is 4
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;
There is a method in which a mask 8 on which a dot pattern 8a having the same pitch as the arrangement pitch of the individual electrodes is formed is polymerized, and then the photoresist layer is removed in dots by applying light from a light source 9 having an emission wavelength such as ultraviolet rays. It is shown. 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 1
Using a mask, the unexposed portions are removed by development and rinsing to obtain dots 4a. Note that, without removing the photoresist layer 4 in a dot shape, by removing the photoresist layer 4 in a slit shape in the same direction as the arrangement direction of the segment electrodes and making the exposed portions of the segment electrode array hazy, the exposed portions 2b
The width may be regulated. In this case, the scanning optical system 7 shown in FIG. 4 performs line scanning, and the mask 8 shown in FIG. 5 has a slit-like pattern 8a.

Phosphor screen forming process As shown in FIG. 2 (5), the substrate 1 coated with the photoresist layer 4 and with the exposed portions 2b of the segment electrode rows 2 exposed is transferred to the phosphor particle supplying means 10 shown in FIG. Attach to.

The phosphor particle supply means 10 includes a container 12 storing a dispersion liquid 11 in which phosphor particles are dispersed, and a dispersion liquid atomization means for atomizing the dispersion liquid 11 and spraying it from a nozzle 13a as an atomized dispersion liquid 11a. 13, a liquid receiver disposed below the nozzle 13a to receive and collect excess liquid of the atomized dispersion, and a member 14, and a member 14 between the nozzle 13a and the liquid receiver. A charging charger 15 consisting of a corona discharge wire 15a and a casing 15b of the corona discharge wire 15a and a casing 15b of the corona discharge wire 15a, which are arranged next to each other and stretched in a direction perpendicular to the plane of the paper, is arranged facing the charger with the atomized dispersion liquid 11a interposed therebetween. A belt conveying means 16 that holds the substrate 1 (see FIG. 2 (5) and FIG. 3) with exposed dot-shaped segment electrode arrays and moves at a predetermined speed in the direction of the arrow, and a wire of the charger 15. It consists of a high-voltage DC power supply 17 that applies positive polarity charges to the segment electrodes 15a and negative polarity charges to the segment electrodes.

The dispersion liquid 11 in which phosphor particles are dispersed includes zinc oxide phosphor (ZnO: Zn) and aluminum nitrate (Al(No3)3) as a control agent in a solvent consisting of isopropyl alcohol ((CH,)2CHOH).・9H20)
A dispersed version of this is used.

As shown in FIG. 8, when the substrate 1 is transported in a direction perpendicular to its longitudinal direction (perpendicular to the paper surface), the corona discharge wire 15a and the mist formed in a band shape perpendicular to the paper surface The constituent members of the chemical dispersion liquid 11a and the substrate 1 are arranged so as to be parallel to each other. Note that in FIG. 8, the insulating layer 3 and photoresist layer 4 on the substrate 1 are not shown.

When the dispersion atomizing means] 3 is started, the dispersion 1
1 is atomized and sprayed as an atomized dispersion liquid 11a toward the liquid receiver member 14 from the nozzle 13a. The liquid receiver is member 14
The atomized dispersion liquid received is recycled and collected in the tank 12 after condensation. When a high positive voltage is applied to the corona discharge wire 15a while the dispersion is being atomized, a positive charge is given to the atomized dispersion 11a. Charged atomized dispersion liquid 1
1a (mist) flies toward the segment electrode and adheres to the exposed portion 2b according to the electric field formed between the corona discharge wire 15a and the negative segment electrode.

Thereafter, when the adhered dispersion is dried and the liquid component is blown off, the remaining phosphor particles form a phosphor screen 18 as shown in FIGS. 2(6) and 6.

This fluorescent screen 18 contains trivalent aluminum ions A1a
Since the +-containing control agent also remains, the conductivity of the phosphor particles forming the phosphor screen is increased. When the conductivity of the phosphor particles increases, the light emitting characteristics improve and the deterioration of brightness decreases.

At this time, phosphor particles are slightly attached to the surface of the photoresist layer 4 in the portion covering the segment electrode row 2, but the exposed portions are not shown in FIGS. 2(6) and 6. Only the phosphor attached to the surface is shown.

The thickness of the phosphor screen 18 is adjusted to a desired thickness by appropriately setting the strength of the applied voltage, the moving speed of the belt conveying means 16, the mutual distance between the corona discharge wire 15a and the exposed portion 2b, and the like.

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 horizontally and, correspondingly, the atomized dispersion is sprayed in a substantially horizontal direction.

Therefore, members that perform the same functions are given the same reference numerals, and individual explanations thereof will be omitted. Note that the moving direction of the belt conveying means 16 in FIGS. 8 and 9 is not limited to the direction of the arrow shown in the figures. Further, the charger 15 is not limited to a wire, but may be a needle electrode.

The substrate on which the phosphor screen has been formed by the method described in FIGS. 8 and 9 proceeds 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, as shown in FIGS. 2(7) and 7, the insulating layers 3, 3, electrodes 2, 2, . ...is exposed. 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 dots 4a is formed on the segment electrode array 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 shape.

(Effects) As described above, according to the present invention, a dispersion liquid in which phosphor particles are dispersed is atomized, the atomized dispersion liquid (mist) is charged, and it is caused to fly toward the segment electrode array. Since this is supplied and adhered to the exposed part of the segment electrode array formed on the substrate, the thickness of the phosphor layer can be made uniform, and the formation of the phosphor screen can be automated, significantly reducing the manufacturing cost of the phosphor dot array tube. can be lowered to

[Brief explanation of the drawing]

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 carrying out the phosphor screen forming method of the present invention, FIG. 9 is a schematic sectional view showing another example of the phosphor particle supply means, and FIG. The figure is an exploded perspective view showing a phosphor dot array tube as an example of a fluorescent display tube, and FIG. 11 is a sectional view of the same. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Segment electrode row, 3... Insulating layer, 4... Photoresist layer, 4a... Dot,
11... Dispersion liquid, lla... Atomized dispersion liquid, 15...
- Charging means, 17... DC power supply, 18... Fluorescent screen.

Claims (1)

[Claims] 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 surface of the substrate including the electrodes is coated along the direction in which the electrodes are arranged. to form an insulating layer that exposes a part of the electrode to form a 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 covered with a photoresist layer. Only the photoresist layer on the individual segment electrodes constituting the segment electrodes was removed to expose the segment electrode array, and in the phosphor screen forming step, a predetermined charge was applied to the segment electrodes to disperse the phosphor particles. A dispersion liquid is atomized in the vicinity of the segment electrode row, and a charge having a polarity opposite to that of the segment electrode is applied to the atomized dispersion liquid by a charging means arranged opposite to the exposed portion of the segment electrode row. Then, the charged atomized dispersion liquid is electrically flown and supplied toward the exposed segment electrode rows, and phosphor particles are attached to the exposed segment electrode rows to form a phosphor screen. and, in the photoresist layer removal step, the photoresist layer is removed to form a phosphor dot array.