JPH08176479A - Phosphor ink and offset printing method - Google Patents

Abstract

PURPOSE: To obtain a printing ink which gives a printed ink film excellent in shape stability and an be completely transferred to a blanket without leaving the ink in an intaglio by using a specified vehicle, a phosphor powder and a white pigment as the constituents. CONSTITUTION: A vehicle is obtained by using, for example, 74.66wt.% red phosphor Y2 O2 S:Eu, 6.4wt.% depolymerized resin such as a polymer of i-BMA, MMA or α-MeSt and having a molecular weight of 65,000, 16.46wt.% solvent comprising diethylene glycol monobutyl ether acetate, 1.49wt.% dispersant, and 0.99wt.% white pigment (fine hydrophobic SiO2 powder). The red phosphor, the white pigment and the dispersant are further added to the vehicle, and the mixture is kneaded to give a red phosphor ink wherein the phosphor has a mean particle diameter of 4μm and which has a viscosity of 75Pa.S under a rate of shear of 2sec<-1> with a type E viscometer. The content of the phosphor powder is 70-80wt.% while the while pigment accounts for 0.2-3wt.% of the total weight of the ink. This ink is filled in the grooves of an intaglio and transferred to a silicone rubber blanket, thus effecting offset printing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor ink, an offset printing method and the like, which can be used in, for example, a light emitting device using a phosphor, particularly a cathode ray tube, an AC type plasma display, a field emission type display and the like. Is.

[0002]

2. Description of the Related Art In a conventional step of forming a cathode ray tube anode of a color television, which is called a wet method, after a glass surface constituting a fluorescent surface is subjected to an appropriate surface treatment,
After pattern exposure and development with a PVA-ammonium dichromate photosensitive solution, a black substance such as graphite was flowed over the developed pattern and cured, and then the photosensitive solution was peeled off to form a light absorbing layer.

On the other hand, the phosphor pattern is formed by applying a slurry in which phosphor powder is dispersed in a PVA-ammonium dichromate photosensitive solution, and then repeating the steps of exposing, developing and drying three times to form each layer of RGB. Was using the process.

As a dry method instead of the wet method, there is a method of printing each color of RGB in a stripe shape by using a phosphor ink in which a phosphor or the like is kneaded.

[0005]

Unlike the wet method, the method using the printing method does not repeat the exposure and development steps, so that the steps can be simplified and a large amount of water is not used. Although it has the advantage that it does not generate contained wastewater, it has a problem in print quality, especially in shape stability.

A printing process using the conventional ink shown in FIG. 9 will be described. The intaglio 1 is made by etching the glass to form the groove 3
Are formed (FIG. 9 (a)).

After the conventional phosphor ink 22 is dropped on the entire surface of the intaglio plate (not shown), the entire surface of the intaglio plate is scraped off with a ceramic squeegee (not shown) to fill the groove 3 of the intaglio plate with the phosphor ink (FIG. 9). (b)).

Next, the blanket 4 having silicone rubber adhered to the surface thereof is rotationally moved in the stripe direction (extending direction of the groove portion 3) while pressure-bonded to the intaglio plate to transfer the ink in the groove to the surface of the blanket 4 (see FIG. 9 (c)). At this time, the ink in the groove is split and torn off between the ink layers (Fig. 9 (d)). On the blanket, the ink that has been torn off and made uneven is attached.

Further, the blanket is pressed onto the glass substrate 5 and rotated to print all the ink on the blanket on the glass substrate (FIG. 9 (e)). The obtained pattern has poor surface smoothness and poor linearity (Fig. 9).
(f)).

The present invention solves the conventional problems in the printing method as described above. The printing ink has excellent shape stability of the printed ink film and can be completely transferred to a blanket without leaving the ink in the intaglio plate. It is an object of the present invention to provide a cold cathode ray tube, an AC type plasma display and a field emission type display obtained by using the ink.

[0011]

In order to solve the above-mentioned problems, the phosphor ink of the present invention comprises a vehicle containing a depolymerizable organic resin, phosphor powder and a white pigment.

The phosphor ink is used to form a display.

[0013]

According to the present invention, a high-performance phosphor ink can be obtained by the above constitution, and when applied to an anode of a cathode ray tube, an AC type plasma display or the like, a cross sectional shape of a printed film having excellent shape stability can be obtained. Further, as a result, the emission brightness is dramatically improved, the screen uniformity is improved, and excellent image display can be performed.

[0014]

EXAMPLE An example of a red phosphor ink using the red phosphor according to the present invention will be described below. First, a vehicle is prepared using a depolymerizable organic resin and a solvent.

That is, based on the composition table shown in (Table 1),
A vehicle was prepared by mixing the depolymerizable resin and the solvent with a magnetic stirrer. Depolymerization type resin has a molecular weight of 650
00.

The fluorescent substance emits light by being excited by an electron beam or an ultraviolet ray in a vacuum, and the resin of the fluorescent ink is a depolymerizable resin which is burned off at a temperature of about 450 ° C. so as not to release a gas in a vacuum. Need to be used. Here, acrylic i-BMA, MMA, and α-MeSt were used.

To this vehicle, a red phosphor, a white pigment and a dispersant were further added and mixed, and the mixture was rolled with a three-roll ceramic roll
The mixture was kneaded once to prepare a red phosphor ink. The average particle size of the phosphor used at this time was 4 μm.

As the white pigment, a fine powder of hydrophobic silica (primary particle diameter: 10 to 20 nm) manufactured by Nippon Aerosil Co., Ltd. was used.

The viscosity of the prepared red phosphor ink was 75 Pa.s when the shear rate was 2 (s ^-1 ) with an E-type viscometer.

[0020]

[Table 1]

Next, using this red phosphor ink, a stripe pattern having a line width of 200 μm and a pitch of 600 μm was printed on a glass substrate.

FIG. 1 shows a printing method. The intaglio plate 1 used was glass etched and had a groove line width of 210
The stripes of μm have a trapezoidal groove cross section with a groove depth of 13 μm (FIG. 1 (a)).

The red phosphor ink 2 is dropped on the entire surface of the intaglio plate (not shown), the entire surface of the intaglio plate is scraped off by a ceramic squeegee (not shown), and the groove part 3 of the intaglio plate is filled with the red phosphor ink (see FIG. b)).

Next, the blanket 4 having silicone rubber adhered to the surface was rotated in the stripe direction while being pressure-bonded to the intaglio plate to transfer the ink in the groove (FIG. 1 (c)).
At this time, all the ink in the groove was transferred to the blanket, and no ink remained in the groove (Fig. 1 (d)). The pressing pressure of the blanket at this time was 3.87 Kg / cm ² , and the transfer speed was 60 mm / sec.

Further, this blanket was pressed and rotated on the glass substrate 5 at the same pressure and speed as when transferring, and all the ink on the blanket was printed on the glass substrate (FIG. 1).
(e)). The obtained pattern had a line width of 200 μm and good linearity, had a trapezoidal cross section, and had a film thickness of 6 μm and film thickness flatness of ± 1 μm (FIG. 1 (f)).

Here, the effect of adding the white pigment will be described. FIG. 2 shows the ink viscosity when the amount of white pigment added to the ink is changed. The addition of white pigment increases the viscosity.

FIG. 3 shows changes in the mechanical tangent loss tan (δ) when the white pigment is changed. The dynamic tangent loss is a ratio of the loss elastic modulus G ″ and the storage elastic modulus G ′, and is a measure indicating which of elastic behavior and viscous behavior is dominant.

By adding 0.2% or more of the white pigment, tan (δ) becomes smaller than 1, and the elastic behavior becomes dominant. On the other hand, when it is 0.2% or less, the viscous behavior becomes larger than 1 and the viscous behavior becomes dominant.

That is, considering this by applying it to the ink at the time of printing, when the ink in the intaglio groove is transferred to the blanket, it is pulled from both the inner wall of the groove and the blanket. The ink containing 0.2% or more of white pigment behaves elastically against this force, so no splitting occurs inside the ink and the ink in the intaglio plate groove with weak adhesive force is peeled off to completely remove the ink in the plate groove. Move to the blanket.

On the other hand, the ink containing 0.2% or less of the white pigment is divided between the layers of the ink and the ink remains in the plate groove as shown in the conventional example, and the ink is stretched and torn to form a blanket. Irregularities are created on the surface of the transferred ink. When this ink is printed on a printing material, the unevenness of the ink is transferred as it is, and the shape stability deteriorates.

On the other hand, if the addition amount exceeds 3%, the ink viscosity exceeds 80 Pa · s as shown in FIG. 2, and the printing characteristics such as filling in the plate groove and transferability to the blanket are deteriorated. The amount of white pigment added should be less than 3%.

Next, the optimum range of the molecular weight of the depolymerizable resin will be described here. FIG. 4 shows the linearity of the printing pattern and the change in the amount of ink filled in the plate groove when the molecular weight of the depolymerizable resin is changed.

When the molecular weight is small, the viscous behavior is dominant, and "threading" of the ink occurs between the inner wall of the groove and the bottom surface, resulting in missing patterns and poor pattern accuracy.

However, as the molecular weight is increased, the pattern accuracy is improved, and when it is 40,000 or more, the pattern accuracy falls within an allowable range.

If the molecular weight is more than 70,000, the cohesive force of the ink becomes large, and when the ink is filled in the plate groove, the ink in the groove is dragged by the ink scraped by the squeegee, Remaining ink amount (ink filling amount)
Will decrease. When the amount of ink in the groove is reduced to 3 μm or less, the ink agglomerates to form beads, and the ink is divided, or even if printing is possible, the film thickness becomes insufficient. Therefore, the resin molecular weight needs to be 70,000 or less.

Further, as shown in FIG. 5, it is desirable that the weight ratio of the phosphor is as high as possible in order to increase the luminous efficiency, but if it is 80% or more, a uniform kneading state such that the periphery of the phosphor is covered with resin is obtained. It is difficult to make it into ink.

On the other hand, if the phosphor content is 70% or less, the luminous efficiency is significantly reduced, so that the weight ratio of the phosphor is 70-.
It needs to be 80%.

The printing speed at which the ink in the plate groove is completely transferred to the blanket varies depending on the composition of the ink, but the optimum value exists in the range of 20 to 100 mm / sec.

At a speed of 20 mm / sec or less, G'becomes small and the viscous behavior is dominant so that the ink in the plate cannot be entirely brought to the blanket, resulting in delamination of the ink and poor shape stability. If the transfer speed is increased to 100 mm / sec or more, ink will not adhere to the blanket and printing will be impossible.

If the transfer pressure when pressing the blanket against the intaglio and the printing pressure when pressing the blanket against the material to be printed are in the range of 1.9 to 6.0 kg / cm ² , the ink in the groove of the intaglio is removed. The whole can be transferred to the blanket, and further, the ink on the blanket can be printed on the printing material without omission. Where 1.9Kg / c
If it is less than m ² , the ink does not adhere to the blanket during transfer, and the ink does not transfer to the substrate during printing. Further, if it is 6.0 Kg / cm ² or more, the pattern accuracy becomes poor.

As the white pigment, here, hydrophobic SiO is used.
_{Although 2} is used, hydrophilic SiO ₂ or TiO ₂ may be used instead.

ZnS: A for blue phosphor ink
g, a phosphor 7 having an average particle diameter of 4 μm is used.
4.66 (wt%), other components are (Table 1)
The components were mixed in the same proportions as described above, and an ink was prepared in the same manner as the red phosphor ink.

When printing was performed using this blue phosphor ink, the ink in the plate groove was transferred to the blanket as in the red phosphor ink, and the printed film was trapezoidal, linear,
The film thickness flatness was excellent.

ZnS: C for green phosphor ink
u, a phosphor having an average particle size of 4 μm
4.66 (wt%), other components are (Table 1)
The components were mixed in the same proportions as described above, and an ink was prepared in the same manner as the red phosphor ink.

When printing was carried out using this green phosphor ink, the ink in the plate groove was transferred to a blanket as in the case of the red phosphor ink, and the printed film was trapezoidal, linear,
The film thickness flatness was excellent.

FIG. 6 shows an embodiment in which a cathode ray tube is formed by using these phosphor inks. FIG. 6A is a sectional view showing a state of a phosphor anode in which red, blue, and green phosphor inks are formed on the face plate glass 6.
(B) is a cross-sectional view of a cathode ray tube. The intaglio shape and printing method are as described above.

After the black stripe 7 is formed on the face plate, the red phosphor ink 8 is printed between the black stripes, and the blue phosphor ink 9 and the green phosphor ink 10 are sequentially printed. The phosphor film had a uniform film thickness over the entire stripe width and the phosphor particles were densely packed, so that the emission intensity was high with respect to the electron beam irradiation, and the phosphor film was uniform and showed excellent display performance.

Here, an example of a tube type using an electron gun as a cathode ray tube is shown, but it is applied to a fluorescent screen of a "color flat panel" having a structure in which a large number of electron beams are generated by using a flat plate type electron source. However, it shows excellent display performance.

FIG. 7 shows an AC image obtained by using these phosphor inks.
An example of forming a phosphor surface of a plasma display device will be described. FIG. 7A is an exploded perspective view of the front glass substrate 11 and the back glass substrate 12 of the AC type plasma display. 13 is a red-blue-green phosphor layer, 14
Is a partition wall, 15 is a white dielectric layer, 16 is a data electrode, 17
Is a surface discharge electrode, 18 is a transparent dielectric layer, and 19 is a black barrier rib.

The intaglio groove 3 used here does not have a trapezoidal cross section, and its both ends are deeper than the central part as shown in FIG. 7B. However, at the time of transfer, all the ink in the groove is transferred to the blanket, and when printed on the printing material, a fluorescent screen is formed between the partition walls as shown in FIG. 7A.

FIG. 8 shows an embodiment in which a phosphor anode of a field emission display is formed by using these phosphor inks. The intaglio used was the same as in the case of FIG.

Reference numeral 11 is a front glass substrate, 12 is a back glass substrate, 20 is a gate electrode, and 21 is an emitter. Since the film thickness of the phosphor was excellent, the distance between the gate and the emitter was constant, and uniform and high emission characteristics were obtained.

[0053]

As described above, the phosphor ink of the present invention exhibits elastic behavior by adding a white pigment in addition to the phosphor powder and the vehicle, and as a result, the ink filled in the intaglio plate. Can be transferred to a blanket, and printing with excellent shape stability can be performed. Further, a cathode ray tube, an AC type plasma display, and a field emission type display in which a phosphor screen is formed by using this phosphor ink have good emission characteristics and screen uniformity, and can display an excellent image.

[Brief description of drawings]

FIG. 1 is a printing process diagram using the phosphor ink of the present invention.

FIG. 2 is a viscosity characteristic diagram of an example of the phosphor ink of the present invention.

FIG. 3 is a viscoelastic characteristic diagram of the phosphor ink of the same example.

FIG. 4 is a characteristic diagram showing pattern accuracy and plate groove ink filling amount when printing is performed using the phosphor ink of the present invention.

FIG. 5 is a characteristic diagram showing the luminous efficiency of the phosphor ink of the present invention.

FIG. 6 is a sectional view of a cathode ray tube formed using the phosphor ink of the present invention.

FIG. 7 is an explanatory diagram of an AC type plasma display using the phosphor ink of the present invention.

FIG. 8 is a cross-sectional view of a field emission display formed using the phosphor ink of the present invention.

FIG. 9 is a printing process diagram when a conventional phosphor ink is used.

[Explanation of symbols]

 1 Intaglio 2 Phosphor ink 3 Groove 4 Blanket

Front page continuation (72) Inventor Masato Hagino 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A vehicle containing a depolymerizable organic binder,
A phosphor ink composed of phosphor powder and a white pigment. 2. By adding a white pigment to a phosphor ink containing a vehicle containing a depolymerization type organic binder and phosphor powder, the elastic behavior of the phosphor ink is made more dominant than the viscous behavior. Closed phosphor ink. 3. The average molecular weight of the depolymerizable organic binder is 40.
It is in the range of 000 to 70,000, and the phosphor ink according to claim 1 or 2. 4. The phosphor ink according to claim 1 or 2, wherein the phosphor powder amount is 70 to 80% by weight. 5. The white pigment is 0.2 to the total amount of the phosphor ink.
The phosphor ink according to claim 1 or 2, wherein the phosphor ink is composed of 3% by weight. 6. When the ink according to claim 1 or 5 is filled in a groove portion of an intaglio plate and the ink is transferred to a silicone rubber blanket, and then the ink is printed on a printing object, the transfer speed and the printing speed are different from each other. An offset printing method, which is 20 to 100 mm / sec. 7. The transfer pressure when the blanket is pressed against the intaglio and the printing pressure when the blanket is pressed against the material to be printed are in the range of 1.9 to 6.0 kg / cm ² , respectively. Item 7. The offset printing method according to item 6. 8. A cathode ray tube having a phosphor screen anode formed by the phosphor ink according to claim 1, wherein the phosphor powders are red, blue and green, respectively. 9. An AC type plasma display having a phosphor screen formed by the phosphor ink according to claim 1 or 2, wherein the phosphor powders are red, blue and green, respectively. 10. A field emission display in which a phosphor screen anode is formed by the phosphor ink according to claim 1 or 2, wherein the phosphor powders are red, blue and green, respectively.