DE69806542T2 - Laminated metal / ferrite magnet - Google Patents

Description

Field of the invention

The present invention relates to a metal/ferrite laminate magnet with perforations and to a method of making such a magnet. More particularly, the present invention relates to a magnet having a metal plate attached to a ferrite for maintaining the positional accuracy of perforations in the laminate and to a method of making a large area laminate magnet with a significant number of perforated holes, one or more integrated metal plates and electrodes for electron and electron beam control.

Background of the invention

A magnetic matrix display is particularly, though not exclusively, useful in flat panel display applications such as television receivers and visual display units for computers, particularly, though not exclusively, portable computers, electronic personal diaries, communications devices and the like.

Conventional flat panel displays, such as liquid crystal displays and field emission displays, are complicated to manufacture because they each require a comparatively high level of semiconductor manufacturing, difficult materials and high tolerances.

UK Patent Application 2304981 discloses a magnetic matrix display comprising a cathode for emitting electrons, a permanent magnet having a two-dimensional array of channels extending between opposite poles of the magnet, the direction of magnetisation being from the surface facing the cathode to the opposite surface. The magnet generates a magnetic field in each channel for forming electrons from the cathode means into an electron beam. The display also comprises a screen for receiving an electron beam from each channel, the screen comprising a phosphor coating facing the side of the magnet remote from the cathode, the phosphor coating comprising a plurality of pixels each corresponding to a different channel. Grid electrode means are arranged between the cathode means and the magnet to control the flow of electrons from the cathode means into each channel. The two-dimensional array of channels is regularly spaced on an xy grid. The magnetic area is large compared to its thickness.

The permanent magnet is used to form essentially linear fields of high intensity in the channels or magnetic apertures for the purpose of collimating the electrons passing through the aperture. The permanent magnet is insulating or has a minimal conductivity to allow a field gradient along the length of the aperture. The placement of the so The orientation of the beam formed on the phosphor coating is strongly dependent on the physical location of the apertures in the permanent magnet.

In operation, these electron beams are directed to a phosphor screen, and collision of the electron beam with the phosphor results in a light output with intensity proportional to the incident beam current (for a fixed final anode voltage). For color displays, three differently colored phosphor elements are used, and the color is achieved by selectively mixing these three primary colors.

For accurate color reproduction, the location of the electron beams on the phosphor of the correct color is essential. Some amount of error can be tolerated by using a "black matrix" to separate the various phosphor elements. This material acts to delineate individual phosphor colors, and also increases the contrast ratio of the displayed image by causing the faceplate of the display to appear darker. However, if the electron beam is incorrectly positioned relative to the phosphor, initially the light output from the phosphor is reduced (due to a loss of beam current to the black matrix), and this becomes visible as luminance non-uniformity. If the beam is subject to a greater placement error, it may scatter onto a different colored phosphor element than the one it was intended for, and begin to produce visible amounts of light output. Thus, the incorrectly positioned electron beam actually produces the wrong color of light output. This is called purity error and is a highly undesirable display artifact. For a 0.3 mm pixel, typical phosphor widths are 67 µm with a 33 µm black matrix in between.

It is obvious that a very precise alignment is required between the magnet used to form the electron beam and the glass plate used to support the phosphor elements that receive the electron beams. Furthermore, this precise alignment must be maintained over a range of different operating conditions (high and low brightness, variable ambient temperature, etc.).

A number of other magnetic properties are also important when considering a display application:

1. It is generally accepted that the displayed image is formed by a regular array of pixels. These pixels are usually arranged on a square or rectangular grid. Thus, to obtain compatibility with graphics adapters, the magnet must present the electron beams on such an array.

2. In operation, the distance between the grids used to bias and modulate the electron beam and the electron source determines the current carried by the electron beam. Variations in this distance result in variations in the beam current and hence in changes in the light output from the phosphor screen.

Thus, one requirement is that the magnet used as a support for these bias and modulation grids maintains a known distance from the electron source. To avoid design difficulties, the magnet should be flat.

3. The indicator is subjected to mechanical forces, particularly during shipment. The magnet must maintain structural integrity over the possible range of mechanical stresses it may encounter. A generally accepted level is an equivalent acceleration of 30 g (294 ms-2).

Another requirement is that since the magnet is to be used in the display, which is evacuated, it should not contain any organic components that can be released over the life of the display, thus degrading the quality of the vacuum or poisoning the cathode.

Finally, the magnet is magnetized in the direction of the apertures, i.e. the poles correspond to the side surfaces of the magnet.

The manufacture of such a magnet that satisfies the above conditions is not possible using currently known manufacturing processes. Of course, a magnet (for example ferrite) with the desired dimensions without apertures is readily available, but the presence of the apertures causes some problems.

If the apertures are to be created in the magnet after the ferrite plate has been sintered, either laser or mechanical drilling can be used. However, the sintered ferrite is a very hard material and creating the apertures by this technique is a costly and time-consuming process - unsuitable for a manufacturing process.

Holes can be created in the ferrite in the green film state before sintering by known punching/drilling techniques. However, a number of problems arise during sintering:

1. The magnetic disk is subject to uneven shrinkage, which causes the holes to "wander" - an uneven radial displacement from their nominal positions.

2. The magnet itself can "bend" so that it forms a section of a large diameter sphere.

3. Due to the apertures acting as concentrators of mechanical stresses, cracking can easily occur between adjacent apertures.

4. When multiple thin films are stacked to achieve the desired aperture length, uneven shrinkage of individual films can result in no "line of sight" through the apertures.

Another problem is that ferrite is a hard but not tough material and the presence of the Apertures significantly reduce the mechanical strength of the plate. This means that a complete mechanical failure of the magnet is a real risk during shipping, when strong shocks can occur.

US Patent 4,138,236 discloses a method for bonding hard and/or soft magnetic ferrite parts to an oxide glass. The oxide glass can be applied before or after a pre-firing or main firing. Finally, the ferrite parts are fused at temperatures above the glass softening point.

U.S. Patent 4,540,500 discloses a low temperature sinterable magnetic oxide material prepared by adding 0.1% to 5% by weight of glass to ferrite. In some situations, the sintering temperature can be reduced to about 1,000°C or less.

U.S. Patent 4,023,057 discloses a composite magnet for a motor stator having a laminated structure that includes thin, flexible magnets made of permanently magnetizable particles such as barium ferrite embedded in a flexible matrix such as rubber. Various laminated arrangements are envisaged for producing more intense magnetic fields, and thin metal spacers are used in most laminated structures to collapse respective fields of the flexible magnetic components, thereby increasing the flux density at the resulting poles and orienting the permanent magnetic fields in the magnetic circuit of the motor.

Published Japanese Patent Application No. JP 60093742 discloses a display having a focus electrode with a conductive magnetic body and a sputtered metal coating on a surface of the magnetic body. The conductivity is required for the focus electrode to perform its function. The coating is sputtered and thus is a thin coating that does not contribute significantly to the mechanical structure of the magnet. Each of the holes in the magnet is associated with a number of electron beams that pass through it.

OK Patent Application 2315266 discloses a magnetophotosensitive glass composite and a method for the same.

However, the prior art does not disclose or teach the metal/ferrite laminate magnet and methods for the same of the present invention.

Disclosure of the invention

Accordingly, the invention provides a metal/ferrite laminate magnet comprising: a first ferrite layer having a first surface and a second surface; a first metal plate having a first surface and a second surface, the first surface being attached to the first ferrite layer over substantially the entire first surface of the first ferrite layer, the first metal plate and the first ferrite layer each having a plurality of apertures formed therein extending from the first surfaces to the second surfaces extend, and wherein the apertures of the first ferrite layer and the first metal plate are substantially aligned; a second ferrite layer having a first surface and a second surface; a second metal plate having a first surface and a second surface, the first surface being attached to the second ferrite layer over substantially the entire first surface of the second ferrite layer, the second metal plate and the second ferrite layer each having a plurality of apertures formed therein extending from the first surfaces to the second surfaces, the apertures of the second ferrite layer and the second metal plate being substantially aligned; and wherein the first metal plate and the first ferrite layer are bonded to the second metal plate attached to the second ferrite layer such that the second surfaces of the first and second ferrite layers abut one another and such that the apertures in the first and second ferrite layers are substantially aligned.

In a preferred embodiment, wherein deflection anodes are provided on one of the outer surfaces of the magnet, the metal/ferrite laminate magnet further includes a first insulating layer having a first surface and a second surface, the first surface being attached to the second metal plate over substantially the entire second surface of the first metal plate; a first conductive layer forming a set of deflection anodes having a first surface and a second surface, the second surface being attached to the first insulating layer over substantially the entire second surface of the first insulating layer; and wherein the first insulating layer and the first conductive layer each have a plurality of respective apertures formed therein, each aperture corresponding to and aligned with a respective aperture in the first metal plate.

In yet another preferred embodiment in which two sets of control grids are provided on the outside of the magnet opposite the deflection anodes, the metal/ferrite laminate magnet further includes: a second insulating layer having a first surface and a second surface, the first surface being attached to the second metal plate over substantially the entire second surface of the second metal plate; a second conductive layer forming a set of control electrodes, having a first surface and a second surface, the first surface being attached to the second insulating layer over substantially the entire second surface of the second insulating layer; a third insulating layer having a first surface and a second surface, the first surface being attached to the second conductive layer over substantially the entire second surface of the second conductive layer; a third conductive layer forming a set of control electrodes, having a first surface and a second surface, the first surface being attached to the third insulating layer over substantially the entire first surface of the third insulating layer; and wherein the second insulating layer, the second conductive layer, the third insulating layer and the third conductive layer each have a plurality of respective apertures formed therein, each aperture corresponds to and is aligned with a respective aperture in the second metal plate.

In order to provide substantially linear high intensity fields in the apertures for collimating electrons passing through the aperture, the first and second ferrite layers are magnetized in the direction of the apertures such that the first surfaces of the first and second ferrite layers form the opposite poles of the magnet.

The majority of apertures formed in the metal layers and the ferrite layers are preferably arranged as a regular array to maintain compatibility with existing graphics adapters.

Furthermore, the thermal expansion coefficient of the ferrite layers for reducing mechanical stresses in the magnet is essentially the same as that of the metal plates.

In a preferred embodiment of the magnet, the metal plates are made of stainless steel, which is magnetically transparent and thus does not disturb the desired flux pattern from the magnet. In an alternative embodiment, the metal plates are made of soft iron with high permeability, which has the effect of short-circuiting the magnetic field outside the magnet structure, thus limiting the collimating effect of the magnetic field to the apertures alone. In a further alternative embodiment, the second metal plate is made of stainless steel and is magnetically transparent, and the first metal plate is made of soft iron and short-circuits the magnetic field outside the magnet structure. This has the Effect that the field lines within the apertures at the end closest to the first metal plate are forced to run perpendicular to the surface of the metal plate, instead of curving toward the outer edges of the magnet.

In yet another preferred embodiment, the ferrite layer has a volume electrical resistance between 10⁷ Ω/ and 10⁹ Ω/. This high but finite resistance creates a leakage path for the charge remaining from collisions of electrons and positive ions with the aperture walls.

The invention also provides a method for producing a metal/ferrite laminate magnet comprising the steps of:

(a) creating at least one opening in a metal layer having a first surface and a second surface,

(b) applying at least one ferrite layer to the first surface of the metal layer,

(c) applying at least one dielectric layer to the second surface of the metal layer,

(d) creating an opening through the ferrite layer and the dielectric layer such that at least a portion of the opening overlaps with a portion of the opening in the metal layer, thereby forming the metal/ferrite laminate magnet.

Short description of the drawings

The invention will now be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 shows a magnet according to a first embodiment of the present invention, comprising a pair of metal layers with two ferrite layers therebetween;

Fig. 2 shows a magnet according to a second embodiment of the present invention, comprising a pair of metal layers with a ferrite layer therebetween;

Fig. 3 shows a magnet according to a first embodiment of the present invention having deflection anodes and control electrodes formed thereon;

Fig. 4 shows a magnet according to a third embodiment of the present invention having a single metal layer attached to a ferrite layer;

Fig. 5 shows a magnet according to a third embodiment of the present invention, in which the single metal layer faces the incoming electron beams; and

Figures 6 to 12 illustrate a method of manufacturing the preferred embodiment of this invention, specifically the metal/ferrite laminate magnet.

Detailed description of the preferred embodiments

Fig. 1 shows a magnet 100 consisting of a magnetic material 120, 115 and with two metal plates 105, 110 between which the magnetic material 120, 115 is layered. Apertures 125 are formed in the layers 120, 115 of magnetic material and in the metal plates 105, 110. The metal plates can be made of magnetically transparent material, such as stainless steel, or they can be made of a metal with a high permeability, such as soft iron.

In each of Figures 1 to 5, the layers are shown with a small gap between them for clarity, but the layers are actually in contact with each other with essentially no gaps.

The process for forming the preferred magnet consists of:

Step 1 - Cut the metal plate 105 to the desired dimensions. Alternatively, the plate 105 can be formed by a rolling process;

Step 2 - Etching the apertures 125 into the metal plate;

Step 3 - Applying the magnetic material 115 (which is in the form of a ferrite green sheet) to one side of the etched metal plate 105;

Step 4 - punching apertures 125 in the magnetic material 115 using the etched holes in the metal plate 105 as guides;

Step 5 - Repeat steps 1 through 4 for a second metal plate 110 and a ferrite green sheet 120;

Step 6 - adjusting the structure produced in step 4 with respect to that produced in step 5;

Step 7 - sintering the sandwich 100 including the magnetic material 115, 120 using a conventional sintering process; and

Step 8 - Adjust the magnetic field perpendicular to the surface of the magnet 100 to magnetize the magnet assembly.

The above structure provides a steel/ferrite laminate magnet with the desired mechanical properties. For each half of the structure, the aperture length is typically in the range 2.0 to 4.0 diameter, with the thickness of the steel substrate being on the order of 50 µm. For a magnet with 100 µm diameter apertures, the aperture length is approximately 400 µm, giving a magnet thickness of 500 µm, and for 200 µm diameter apertures, the aperture length can increase to 1.2 mm, giving a magnet thickness of 1.3 mm. Note that these figures represent the maximum aperture aspect ratio and that this is not necessarily required for satisfactory beam collimation.

The stainless steel plates used on the outside of the magnet are magnetically "transparent" so as not to disturb the desired flux pattern from the magnet. The plates also serve to maintain the flatness of the magnet under mechanical stresses imposed by the Construction, thermal cycling or operation of a hot cathode, whereby temperature variations can be neutralized by the thermally conductive metal.

It is possible to use metal plates of high permeability, such as soft iron. These have the effect of "short-circuiting" the magnetic field outside the magnet assembly, thus limiting the collimating effect of the magnetic field to the apertures alone. Outside the apertures, the electron beam is then only affected by electrostatic fields associated with normal display operation. The electron beam is still affected by magnetic fields generated outside the display. The permeable metal plate does not correct for high external fields, but does provide some correction.

The magnet is to be used with electron beams passing through the apertures. Despite the collimating effect of the magnetic field, there are inevitably some collisions of stray electrons and positively charged ions with the aperture walls. If the magnetic material were a perfect insulator, the electron collisions would result in the deposition of a negative charge on the aperture walls, and collisions with positive ions would result in the deposition of a positive charge on the aperture walls. This in turn would result in a reduction of the potential at the walls, thereby disturbing the electrostatic field pattern and consequently the electron beam. In the extreme case, if sufficient charge were applied, the potential would drop so much that any further electrons would be prevented from entering the aperture and the display would stop functioning until this charge was removed.

To circumvent this problem, the magnetic material has an additive that provides a high but finite resistance, typically in the range of 107 Ω/ to 109 Ω/ . Thus, there is a leakage path for the charge left behind by any collisions of electrons or any collisions of positive ions with the aperture walls. However, the resistance is sufficiently high to allow the correct potential gradient across the aperture without dissipating excessive power, which would lead to possible thermal problems within the magnet itself.

Other ceramic materials (particularly glass) are added to the base ferrite to act as binders and modify the thermal expansion coefficient of the ferrite/glass laminate for close conformance to the metal plate(s). Similarly, dielectric and electrode materials should have thermal expansion coefficients close to or matching those of the metal plates. For the ferrite/glass composite, increasing the percentage of glass per volume reduces the final achievable magnetic field strength. Calculations suggest that up to one third of the ferrite can be replaced before the collimating effect of the field is degraded to the point where it causes a problem in the operation of the display. This corresponds to a magnetic field strength of about 2,000 gauss. In conventional use, this percentage of binders etc. is not required. Increasing the required magnetic field strength can be achieved if necessary with alternative materials, such as one of the rare earths. A suitable rare earth material is samarium cobalt.

Another advantage of the laminate structure is that the steel plates on the outside of the magnet are highly electrically conductive. They thus form equipotential surfaces on each side of the magnetic apertures. This means that a very uniform field can be expected across the display. Apart from the uniformity of the field, the etched holes in the steel plate also "shield" the magnetic aperture walls from the collision of stray electrons.

Computer simulations show that the most likely place for a collision to occur is at the entrance of the aperture, before the full collimating effect of the magnetic field has taken effect. In this region, the electrons pass through the steel layer and, as it is a conductor, collisions are not a problem, proving to be a negligible current flowing in the base plate.

Fig. 2 shows a second embodiment 200 of the present invention. In this embodiment, a single ferrite layer 120 is used together with an upper metal plate 110 and a lower metal plate 105. In this context, lower means the surface of the magnet facing the cathode or electron source, and upper means the surface of the magnet facing the phosphor screen. This embodiment does not allow the formation of apertures with such high aspect ratio, but it allows for a more cost-effective and simpler construction. The benefits of maintaining the positional accuracy of the apertures during manufacturing are still achieved.

One of the distinguishing features of a magnetic matrix display is the mechanical simplicity of the display structure. A major contributor to this simplicity is the use of the magnet as a support for the grid electrodes used to drive the display.

Fig. 3 shows a laminate magnet according to the present invention. The magnet structure 100 corresponds to that of Fig. 1. In addition, since the outer sides of the magnet assembly are made of highly conductive steel plates, a thin insulating layer 310, typically 50 µm thick, is present between the steel plate 110 and the deflection electrode 305. The deflection electrode 305 is a deflection electrode as described in UK patent application 2304981, referred to earlier in this specification.

Similarly, control electrodes 320 and 330 are located on a steel plate 105, separated from the steel plate 105 by an insulating layer 315 and from each other by another insulating layer 325. Each of the insulating layers 315, 325 is typically 50 µm thick.

Fig. 4 shows a third embodiment 400 of the present invention. In this embodiment, only a single metal plate 110 is used, which increases the overall strength compared to the first and second embodiments described in Figs. 1 and 2, respectively, but the cost and complexity of manufacturing are reduced. The cathode or electron source is located below the magnet and the electrons enter the apertures 125 in the direction shown by arrows 405.

Fig. 5 shows a variation 500 of the third embodiment shown in Fig. 4, in which the single metal plate 105 is on the other side of the ferrite, i.e. the plate is on the side facing the cathode or electron source. The electrons enter the apertures 125 in the direction shown by arrows 505.

Figures 6 through 12 illustrate a method of manufacturing the metal/ferrite laminate magnet 100 of this invention. Figure 6 shows a rolled metal layer 605, preferably capable of withstanding oxidizing atmospheres of up to about 1000°C. On this metal layer 605 is applied a photoresist 606 which is exposed and developed to create a pattern of holes 607 in the resist 606. The metal layer 605 and the developed photoresist 606 are then placed in an etchant which attacks the metal only in the area not protected by the resist 606. This creates the desired array of holes 125 in the metal layer 605, which creates the perforated metal layer 705, as clearly seen in Figure 7.

The photoresist 606 is then removed from the metal layer 705. The etched metal layer 705 can now be tested to ensure that all holes 125 are present and that the dimensional and position tolerances of the holes are met.

For some applications, the metal layer 705 may need to be prepared to improve the adhesion between it and the subsequent ferrite layer and/or dielectric layer. This may be accomplished by the deposition or formation of selected adhesion-enhancing metals or oxides on one or both surfaces of the metal layer 705. However, a suitable adhesive may also be used to attach the ferrite layer and/or dielectric layer to the metal layer 705.

A ferrite layer 815 is created by combining ferrite material with a glass powder, organic binders, solvents and carriers to create an emulsion that can be cast into thin ferrite layers. The technology used to create these thin ferrite layers 815 is similar to that used to create conventional multilayer ceramic green sheets. After drying, the cast layers are cut to the correct size to form a ferrite layer 815 to be used in the further processing.

Similarly, a dielectric layer 813 is formed by processing dielectric material or materials into an emulsion and casting to form thin dielectric green layers 813. After drying, these cast layers are also cut to the correct size to form thin dielectric to form green layers 813 to be used for the further process flow. The dielectric layer 813 can be created by alternative techniques, such as oxidation of the surface of the metal layer 705.

As shown in Figure 8, a laminate structure is created by combining the etched metal layer 705 with the thin dielectric green layer 813 on one side and the thin ferrite green layer 815 on the other side to form a primary "green" laminate structure 809. It is preferred that the laminate structure 809 be fixed such that there is no movement between the various layers. This fixation can be accomplished by the simultaneous application of heat and/or pressure to all three components or layers of the laminate structure 809 or by adhesively bonding the layers to the metal layer 705.

After the primary "green" laminate structure 809 is created, holes are created in the ferrite green layer 815 and the dielectric green layer 813 using the pre-existing etched holes 125 in the metal layer 705 as a guide. The holes formed in the green layer components of the laminate structure 809 can be created by a myriad of mechanical, laser, or electron beam techniques known to those skilled in the art. This is shown in Figure 9, where a primary "green" laminate structure 809 has been perforated with holes 125 created in the ferrite green layer 815 and the dielectric green layer 813, creating a perforated ferrite green layer 915 and a perforated dielectric green layer 913 that are combined with the metal layer 905 to form a perforated primary green laminate 919.

A plurality of perforated first "raw" laminate structures 919 may be combined into a secondary "raw" laminate structure 1029. This is accomplished by re-applying heat and/or pressure to the components or by using an organic adhesive. Care must be taken in this step to ensure alignment of the holes 125 in the various substructures.

The "green" secondary laminate structure 1029 is thermally processed in a manner to drive out or decompose the organic components that may be present in the structure 1029. This thermal process also coalesces the particles used to make the ferrite and dielectric layers, bonds the ferrite layer 915 and dielectric layer 913 to the metal layer 905, and bonds the ferrite layers 915 to one another, as more clearly seen in FIG. 10. Note that for clarity, through holes 125 have not been shown in the laminate structure 1029 of FIG. 10.

The thermal processing of the secondary "green" laminate 1029 is preferably carried out at a temperature lower than that which causes permanent deformation of the metal layer 905. The glass phase added to the ferrite powder enhances the sintering of the structure.

An alternative way of making the sintered laminate structure 1029 is shown in Fig. 11, in which the structure 809 as shown in Fig. 8 is stacked to produce a structure 1159. The stacked and Laminated structure 1159 is similar to laminate structure 1029, except that holes 125 have been formed only in metal layer 905, and there are no holes 125 in ferrite layer 915 or dielectric layer 913. This structure 1159 is then partially sintered to produce a structure 1159 that is substantially free of any organic material and is also partially densified. This partial densification of laminate structure 1159 should be such that a mechanical means can be used to create holes through dielectric layer 913 and ferrite layer 915. One way to create holes 125 is to use a media jet or pressurized impinging media 1156. Care should be taken not to damage laminate structure 1159 in any way. One way to avoid any damage to the laminate structure 1159 is to attach a metal or coated metal-like plate 1151 with openings 1155 corresponding to the openings 125 to the side of the laminate structure 1159 that is struck by the impinging media 1156. The metal-like plate 1151 may also have a polymer or rubber backing 1153 with openings 1155. Particles from the media jet 1156 passing through the openings 1155 strike the particles near the openings 125 and this results in the removal of particles 1157, creating openings 125 in both the dielectric layer 913 and the ferrite layer 915, resulting in a laminate structure 1029 having through openings 125. The laminate structure 1029 with through holes 125 can now be fully sintered if this has not already been done.

After the sintered laminate structure 1159 is formed, the deflection electrode 305 and the control electrodes 320 and 330 are attached or formed to the structure, as clearly shown in Fig. 12.

These electrically conductive metal structures, such as metal structures 320, 330, and 305, may be applied by any of a number of techniques including screen printing metal pastes, photo- or mechanical patterning of applied metal layers, or application of a pre-patterned metal decal. Depending on the techniques used to apply the metal structures, subsequent heat treatment of the laminate structure may be required.

To form the metal structures 320 and 330, it is preferred that after the initial metal structure, e.g., 320, is attached to the surface of the sintered laminate structure 1159, a second set of control grid electrodes 330 may be attached orthogonally to the first set 320 or 330, as it makes no difference whether the grid electrode 320 is formed first or the grid electrode 330 is formed first. However, prior to attaching the second set of control grid electrodes, a dielectric layer 315 may be attached to the first set of electrodes, e.g., electrode 320, to isolate one electrode from the other electrode. This dielectric layer 315 may be attached in the form of an adhesively bonded green sheet, it may be prepared as an emulsion that is sprayed onto the surface, or it may be applied using conventional Thin film deposition techniques that are well known in the art.

Depending on the technique used to apply the dielectric layer 315, the sintered laminate 1159 may need to be subjected to further heat treatment to allow the dielectric layer powders to grow together. What is crucial in this step is that the holes 1241, 1243 and 125 that form the pixel hole 1270 must not be altered in structure by the application of the dielectric layer 315. After the dielectric layer 315 is applied to the surface of the sintered laminate over the first set of control grid electrodes, the second set of control grid electrodes may be applied orthogonally to the first.

The application of these metal elements uses any of the techniques previously described for the application of surface metallization.

However, it is worth noting that all metal and dielectric elements can be attached to the sintered laminate in a non-sintered, pre-structured form. A second sintering then bonds these elements to the initial laminate structure.

After the final sintered laminate is produced, it is subjected to an electrical test, a physical test and finally the polarization of the ferrite layers 915 to generate the necessary magnetic field. It should be apparent that polarization of the Ferrite layers 915 can take place before or after the laminate magnet is installed in a component. Furthermore, the polarization of the ferrite layers 915 can also take place at elevated temperatures.

An advantage of the laminate magnet of the present invention is that the apertures 125 or the pixel wells 1270 do not have to be perfectly aligned for an electron beam to pass through the pixel wells 1270.

The metal plate(s) 905 that are part of the laminate magnet provide numerous advantages. For example, the metal plate avoids charging and acts as a stray electron sink. It provides mechanical strength to the laminate magnet. It provides a reduction in the thermal stress gradient. The metal plate(s) provide dimensional stability. They are used for the location accuracy of the hole formation process. For some applications, the metal plate(s) 905 can also be used as a mask for the formation of phosphor elements on the glass plate.

Claims (30)

1. Metal/ferrite laminate magnet (100) with: a first ferrite layer (115) having a first surface and a second surface; a first metal plate (105) having a first surface and a second surface, the first surface being attached to the first ferrite layer over substantially the entire first surface of the first ferrite layer; wherein the first metal plate and the first ferrite layer each have a plurality of apertures (125) formed therein extending from the first surfaces to the second surfaces, the apertures of the first ferrite layer and the first metal plate being substantially aligned; a second ferrite layer (120) having a first surface and a second surface; a second metal plate (110) having a first surface and a second surface, the first surface being attached to the second ferrite layer over substantially the entire first surface of the second ferrite layer; wherein the second metal plate and the second ferrite layer each have a plurality of apertures formed therein (125) extending from the first surfaces to the second surfaces, wherein the apertures of the "second ferrite layer and the second metal plate are substantially aligned; and wherein the first metal plate and the first ferrite layer are bonded to the second metal plate attached to the second ferrite layer such that the second surfaces of the first and second ferrite layers are in abutment with one another and such that the apertures in the first and second ferrite layers are substantially aligned. 2. Metal/ferrite laminate magnet (100) according to claim 1, further comprising: a first insulating layer (310) having a first surface and a second surface, the first surface being attached to the second metal plate (110) over substantially the entire second surface of the first metal plate; a first conductive layer (305) forming a set of deflection anodes, having a first surface and a second surface, the second surface being attached to the first insulating layer over substantially the entire second surface of the first insulating layer; and wherein the first insulating layer and the first conductive layer each have a plurality of apertures (125) formed therein, each Aperture corresponds to and is aligned with a respective aperture in the first metal plate. 3. A metal/ferrite laminate magnet (100) according to claim 2, further comprising: a second insulating layer (315) having a first surface and a second surface, the first surface being attached to the first metal plate (105) over substantially the entire second surface of the first metal plate; a second conductive layer (320) forming a set of control electrodes, having a first surface and a second surface, the first surface being attached to the second insulating layer over substantially the entire second surface of the second insulating layer; a third insulating layer (325) having a first surface and a second surface, the first surface being attached to the second conductive layer over substantially the entire second surface of the second conductive layer; a third conductive layer (330) forming a set of control electrodes, having a first surface and a second surface, the first surface being attached to the third insulating layer over substantially the entire first surface of the third insulating layer; and wherein the second insulating layer, the second conductive layer, the third insulating layer and the third conductive layer each have a plurality of apertures formed therein, each aperture (125) corresponding to and aligned with a respective aperture in the second metal plate. 4. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the first (115) and second (120) ferrite layers are magnetized in the direction of the apertures (125) so that the first surfaces form the poles of the magnet. 5. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the plurality of apertures (125) formed in the first metal plate (105) and the first ferrite layer (115) are arranged as a regular array. 6. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the regular field is a square field. 7. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the regular array is a rectangular array. 8. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the thermal expansion coefficient of the first (115) and second (120) ferrite layers is substantially equal to that of the first (105) and second (110) metal plates. 9. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the first (105) and second (110) metal plates are made of stainless steel. 10. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the first (105) and second (110) metal plates are made of soft iron. 11. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the first metal plate (105) is made of soft iron and the second metal plate (110) is made of stainless steel. 12. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the diameter of the apertures (125) is approximately 100 µm, the thickness of the first (105) and second (110) metal plates is each approximately 50 µm, and the thickness of the first (115) and second (120) ferrite layers is each approximately 200 µm. 13. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the diameter of the apertures (125) is approximately 200 µm, the thickness of the first (105) and second (110) metal plates is each approximately 50 µm, and the thickness of the first (115) and second (120) ferrite layers is each approximately 600 µm. 14. A metal/ferrite laminate magnet (100) according to any preceding claim, wherein the ferrite layer has a volume electrical resistivity between 10⁷ Ω/ and 10⁹ Ω/ . 15. A method of manufacturing a metal/ferrite laminate magnet (100), comprising the steps of: (a) forming at least one aperture (125) in a metal plate (105) having a first surface and a second surface, (b) applying at least one ferrite layer (115) to the first surface of the metal plate, (c) applying at least one dielectric layer (310) to the second surface of the metal plate, (d) creating an opening through the ferrite layer and the dielectric layer such that at least a portion of the opening overlaps with a portion of the opening in the metal plate, thereby forming the metal/ferrite laminate magnet. 16. The method of claim 15, wherein the at least one aperture (125) in the metal plate (105) is created by applying at least one photoresist (606) to the metal plate, exposing and developing the photoresist to form a pattern of apertures, and subsequently etching the metal plate to form the at least one aperture in the metal plate. 17. The method of claim 15, wherein the at least one aperture (125) in the metal plate (105) is formed by a laser beam, an electron beam or mechanical means. 18. The method of claim 15, further comprising mixing ferrite material with glass particles, organic binders and solvents to form a ferrite emulsion; mixing, pouring and drying the ferrite emulsion into a raw ferrite layer; and cutting the raw ferrite layer into the at least one ferrite layer. 19. The method of claim 15, further comprising mixing dielectric material to form a dielectric emulsion; mixing, casting and drying the dielectric emulsion into a dielectric green sheet; and cutting the dielectric green sheet into the at least one dielectric layer. 20. The method of claim 15, wherein the at least one electrically conductive metal is disposed adjacent to the aperture (125). 21. The method of claim 15, further comprising applying at least one anode means (305) to the perforated side of the magnet (100). 22. The method of claim 15, further comprising attaching at least one control electrode means (320, 330) to the side of the magnet (100) remote from the side carrying an anode means (305). 23. The method of claim 15, wherein the aperture in the ferrite layer (115) is created by partially sintering the ferrite layer and using a pressurized, impinging medium (1156) to open at least one hole. 24. The method of claim 15, wherein two of the metal/ferrite laminate magnets are attached to each other such that the metal plate (105) forms a sandwich with the ferrite material (115) and the dielectric material is on the opposite sides. 25. The method of claim 15, further comprising mixing ferrite material with glass particles, organic binders and solvents to form a ferrite emulsion, wherein the ferrite emulsion is applied to the metal plate (105) using at least one spray. 26. The method of claim 15, further comprising mixing dielectric material to form a dielectric emulsion, wherein the dielectric emulsion is applied to the metal plate (105) using at least one spray. 27. The method of claim 15, further comprising heating the metal plate (105) to at least 300°C and applying dry ferrite powder material to the heated metal plate until at least one coating of ferrite material (115) is formed on the metal plate. 28. The method of claim 15, further comprising heating the metal plate (105) to at least 300°C and applying dry dielectric powder material to the heated metal plate until at least a coating of the dielectric material is formed on the metal plate. 29. The method of claim 15, wherein at least one surface of the metal plate (105) is oxidized to form at least one dielectric layer. 30. The method of claim 15, wherein the aperture (125) in the metal plate (105) is used to form corresponding holes in subsequent components of the laminate magnet (100), and wherein all correspondingly formed holes are maintained in alignment with the hole in the metal plate.