JPH11237851A - Bath for electrophoretic deposition and deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the bath for electroporetic deposition which is suitable for the manufacture of an electrode structure capable of reducing a current supplied to plasma while the sputtering of an electrode is reduced by allowing the bath for electrophoretic deposition to contain magnesium nitrate of specific concn. SOLUTION: The current supplied to the plasma of a PALC display panel depends upon the concn. of magnesium nitrate in the bath for electrophoretic deposition and the concn. of the magnesium nitrate for forming a sufficient coating of LaB6 is about 2×10<-5> mol. Namely, salt as an assistant of about (n/2)×2×10<-5> mol in concn. is used for the electrophoretic depositon method using a solution containing rare earth boride and then a metallic body can be provided with a sufficient coating of rare earth boride. When this coated metallic body is used as the cathode of the PALC display panel, the value of the current supplied to the plasma is reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophoretic deposition method suitable for providing a coating on electrodes of a plasma addressed liquid crystal (PALC) display panel.
etic deposition) and a bath.

[0002]

2. Description of the Related Art U.S. Pat. No. 5,077,553 (corresponding to Japanese Patent No. 2,601,713) describes an apparatus for addressing data storage elements. FIG. 1 shows a cross section of a PALC panel (or a PALC display panel) in which the apparatus disclosed in U.S. Pat. No. 5,077,553 is actually implemented. Note that for clarity,
The hatched lines indicating the cross section are omitted.

[0003] The PALC panel shown in FIG. 1 includes, in order from the bottom, a polarizer 2, a channel member 4, a cover sheet (commonly known as a microsheet) 6.
An electro-optic material layer 10, an array of parallel and transparent data drive electrodes (only one data drive electrode indicated by 12 in FIG. 1 is visible), an upper substrate 14 supporting the data drive electrodes, And an upper polarizer 16. In the case of a color display panel, the panel includes a color filter (not shown) between the electro-optic material layer 10 and the upper substrate 14. The panel may include layers that improve viewing angle and other layers of interest. The channel member 4 is typically made of glass, and has a plurality of parallel channels 20 formed on an upper main surface thereof. The plurality of channels 20 are separated by ribs 22 and are filled with an ionizable gas such as helium. An anode 24 and a cathode 26 are provided for each of the channels 20. The channels 20 are orthogonal to the data drive electrodes 12 (when viewed perpendicular to the panel), and the areas where the data drive electrodes 12 intersect the channels 20 are the individual panel elements 2
8 is formed. Each panel element 28 includes the electro-optic material layer 1
0, the upper polarizer 16, and the lower polarizer 2. The area of the upper surface of the display panel that bounds the panel elements 28 constitutes a single pixel 30 of the display panel. Reference numeral 32 indicates the viewpoint of the observer.

In the implementation of the PALC display panel, the channel member 4 is etched in the vicinity of a region where a channel is to be formed to provide a pedestal (plateau) 36. A channel 20 is formed in the base. In addition, the cover sheet 6 is fixed to the channel member by endless frit beads 38 in a lavet (tongue) 40 extending near the periphery of the base. An upper substrate assembly including the upper substrate 14 and the data driving electrodes 12 supported thereon;
It is attached to the channel member 4 by the bonding beads 42. The bonding beads 42 extend almost completely to the vicinity of the frit beads 38, but one corner remains open. The space between the opposing surfaces of the cover sheet 6 and the upper substrate assembly forms a space for the electro-optic material layer 10.

When the anode 24 in one channel 20 is supplied to a reference potential and an appropriate more negative voltage is supplied to the cathode 26 in this channel, the gas in that channel produces a plasma which Plasma cover sheet 6
A conductive path to the reference potential source is formed on the lower surface of the lower electrode. If the data drive electrode 12 is at the reference potential, the data drive electrode 12
Has no substantial electric field, and the panel element 28 can be considered to be off. Conversely, if the potential of the data driving electrode 12 is substantially different from the reference potential, a substantial electric field is generated in the volume element of the electro-optic material layer 10, and the panel element 28 can be considered to be on.

In the following description, although not limiting the gist of the present invention, the lower polarizer 2 is a linear polarizer, and its polarization plane is arbitrarily set at 0 degree with respect to the reference plane. It is assumed that the upper polarizer 16 is a linear polarizer having a 90-degree polarization plane. It is also assumed that the material of the electro-optic material layer 10 is a twisted nematic liquid crystal material. In this case, the plane of polarization of the linearly polarized light passing therethrough rotates by an angle that is a function of the electric field of the liquid crystal material. When the panel element is off, the rotation angle is 90 degrees,
When the panel element is on, the rotation angle is zero.

The panel is illuminated from below by a broad light source 34 that emits unpolarized white light. In order to uniformly illuminate the panel, a back glass diffuser (ground glass) 18 having a scattering surface may be placed between the light source 34 and the panel. A predetermined panel element 2 from the light source 34
8 is linearly polarized to zero degree by the lower polarizer 2, and the channel member 4, the channel 20, and the cover
Sheet 6, sequentially passing through the volume element of the liquid crystal material,
It goes to the upper polarizer 16 and the observer 32. If the panel element is off, the plane of polarization of the linearly polarized light passing through the volume element of the liquid crystal material is rotated 90 degrees, so the plane of polarization of the light incident on the upper polarizer 16 is 90 degrees. This light passes through the upper polarizer 16 and illuminates the pixels. On the other hand, if the panel element is on, the plane of polarization of the linearly polarized light does not change when passing through the volume element of the liquid crystal material. Since the plane of polarization of the incident light on the upper polarizer 16 is zero degrees, this light is blocked by the upper polarizer 16 and the pixels are dark. If the electric field in the liquid crystal material is intermediate between the values associated with turning off and on the panel element 28, this light will pass through the upper polarizer 16, but its brightness will be determined by the electric field,
Gray scale (halftone) can be displayed.

[0008]

During operation of the PALC panel, the cathode 26 is sputtered by positive ions of the plasma. This sputtering reduces the useful life of the panel. A non-reactive substance (refr
It has been proposed to provide a protective top coat of actory material to protect the cathode from sputtering damage. Such proposals include U.S. Pat. No. 5,783,906 assigned to the assignee of the present application (Japanese Patent Laid-Open No. 9-311).
647), US Provisional Application No. 60/02341.
No. 8 (corresponding to JP-A-10-96902) and U.S. Provisional Application No. 60/032971 (JP-A-10-1863).
No. 36). Coating of non reactive material, LaB ₆ rare earth boride (rare earth hexabori such
de).

Electrophoretic deposition (cataphoretic dep)
It is known to connect an electrical conductor (metal) as a cathode in a cell and deposit a solid substance on the conductor. In addition, bathtub (bat
h) comprises particles of a solid substance suspended in an aqueous solution of a suitable auxiliary salt, ie the auxiliary salt, in finely divided form. The salt of this auxiliary is dissociated in the dissolved state and the cations are adhering to the particles of the solid substance. The electric field in the electrophoretic deposition cell directs the particles toward the cathode of the electrophoretic deposition cell, and the particles are deposited on a metal object.

The inventor of the present invention has disclosed that LaB ₆ and glass particles are suspended in fine powder form in a mixture of isopropyl alcohol and an aqueous solution of a suitable auxiliary salt in a weight ratio of 75:25. Using a cloudy tub, La on a metal object
Using an electrophoretic deposition method of depositing a of B ₆ and glass. After sufficient LaB ₆ has been deposited on the metal, the metal is removed from the bath and fired.
Then, the glass frit is melted, and the LaB ₆ particles are bonded to the metal object. This can reduce electrode sputtering.

The inventor of the present invention has developed magnesium nitrate Mg.
(NO ₃ ) ₂ was found to be suitable as an auxiliary salt for electrophoretic deposition of LaB ₆ and glass frit. At this time, the concentration of magnesium nitrate used as a salt of the auxiliary by the inventor was about 2 × 10 ⁻⁴ mol.

On the other hand, it is desirable to minimize the current supplied to the plasma during the operation of the PALC panel. This is because reducing the current reduces the power consumption of the PALC panel and lowers the operating temperature of the panel. Further, by reducing the current supplied to the plasma, the current to be used can be small, so that the circuit components for operating the panel can be inexpensive.

Accordingly, an object of the present invention is to provide an electrophoretic deposition bath and an electrophoretic deposition bath suitable for manufacturing an electrode assembly capable of reducing the current supplied to plasma in a PALC panel with reduced electrode sputtering. An object of the present invention is to provide an electrophoretic deposition method.

[0014]

According to the present invention, the current supplied to the plasma of a PALC panel having an electrode coated with LaB ₆ deposited by electrophoresis is controlled by an auxiliary agent in an electrophoretic deposition bath. Was determined by the concentration of salt. When the auxiliary salt is magnesium nitrate, the minimum concentration of the auxiliary salt at which sufficient coating of LaB ₆ can be deposited is about 2 × 10 ⁻⁵ mol.

According to a first aspect of the present invention, the electrophoretic deposition bath of the present invention contains magnesium nitrate having a concentration of about 2 × 10 ⁻⁵ mol.

According to a second aspect of the invention, the invention provides:
A method for depositing a substance on a conductive material, comprising: providing an electrophoretic deposition bath containing a substance in a fine powder state suspended in a liquid containing an aqueous solution of a salt as an auxiliary agent; An electric field is formed in the liquid between the conductive material connected as the cathode and the anode, and the concentration of the auxiliary salt in the liquid is about (n / 2) × 2 × 10 ⁻⁵ mol. Yes, n
Is the valency of the positive ion of the salt of the auxiliary agent.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. With about 2 × 10 ^-4 mol of the bath for electrophoretic deposition containing magnesium nitrate, it is conventional for depositing particles of LaB ₆ on the cathode of the PALC display panel. However, according to the present invention, the current supplied to the plasma of the PALC display panel depends on the concentration of magnesium nitrate in the bath for electrophoretic deposition, and the concentration of magnesium nitrate for forming a sufficient coating of LaB ₆ is reduced. It was found to be about 2 × 10 ^-5 mol.

The invention is not restricted to the fact that the auxiliary salt is magnesium nitrate. This is because salts of other auxiliaries such as calcium nitrate, strontium nitrate, aluminum nitrate and lanthanum nitrate can also be used for electrophoretic deposition. It is believed that the efficiency of the salt of the water-soluble auxiliary to assist electrophoresis depends on the charge of the positive ion in the salt of the auxiliary. Therefore, ^{4 such} as Th ⁴⁺
For a positive (4 valence) cation, a suitable concentration of the auxiliary salt is about (2/4) × 2 × 10 ⁻⁵ molar, ie about 1 ×
10 ^-5 mol. On the other hand, for trivalent (trivalent) cations such as Al ³⁺ , a suitable concentration of the auxiliary salt is
It is about (2/3) × 2 × 10 ⁻⁵ mol. Thus, in general, for a positive ion of a salt of an n-valent water-soluble auxiliary, a suitable concentration is about (n / 2) × 2 × 10 ⁻⁵ mol.

It will be understood that the present invention is not limited to the specific embodiments described above, but that various modifications can be made without departing from the spirit of the invention. For example, the present invention can be applied not only to the electrophoretic deposition of LaB ₆ but also to the electrophoretic deposition of other rare earth borides. Further, the present invention can be used for, for example, the deposition of a phosphor in the production of a cathode ray tube.

[0020]

As described above, according to the present invention, in an electrophoretic deposition method using an aqueous solution containing a rare earth boride, a concentration of about (n / 2) × 2 × 10 ⁻⁵ mol is used. By using a salt as an agent, a sufficient coating of a rare earth boride can be provided on a metal object. When this coated metal material is used as a cathode of a PALC display panel, the value of current supplied to plasma can be reduced. In addition,
If the auxiliary salt is magnesium nitrate, its optimum concentration is about 2 × 10 ^-5 mol.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a conventional PALC panel.

[Explanation of symbols]

 2 lower polarizer 4 channel region 6 cover sheet 10 electro-optic material layer 12 data drive electrode 14 upper substrate 16 upper polarizer 18 back glass diffuser 20 channel 22 rib 24 anode 26 cathode 28 panel element 30 pixel 32 observer Viewpoint 34 light source 43 beads

Continued on the front page (72) Inventor Donald E. Kefert 97219 Portland, Oregon Portland South West Fifth Avenue 7131

Claims (3)

[Claims] 1. An electrophoretic deposition bath containing magnesium nitrate having a concentration of about 2 × 10 ⁻⁵ mol. 2. A salt, which is a water-soluble auxiliary having a concentration of about (n / 2) × 2 × 10 ^-5 mol, wherein n is the valency of a positive ion of the salt of the auxiliary. Bath for electrophoretic deposition. 3. A method for depositing a substance on a conductive material, comprising: providing an electrophoretic deposition bath containing the substance in the form of fine powder suspended in a liquid containing an aqueous solution of an auxiliary salt. Sinking the conductive material in the liquid, forming an electric field in the liquid between the conductive material and the anode connected as a cathode, and the concentration of the auxiliary salt in the liquid being about (n / 2) ×
A deposition method, wherein 2 × 10 ⁻⁵ mol, and n is the valence of a positive ion of the salt of the auxiliary agent.