JPH0125068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid crystal display panel, particularly a matrix type liquid crystal display panel suitable for waveform display in an oscilloscope or the like.

[Conventional technology and problems]

A basic liquid crystal display (LCD) panel has a thin film of liquid crystal material interposed between a pair of insulating support plates, at least one of which is transparent.
Both support plates are generally made of glass. The peripheral edge of this support plate is sealed to prevent the liquid crystal from flowing out and to prevent foreign matter from entering the liquid crystal. In some cases, this seal also acts as a spacer to maintain the distance between the support plates at a constant value. Transparent conductive coatings are formed on the inner surfaces of both support plates, and an electric field is applied to selected areas of the liquid crystal film. Depending on the intended use of the LCD device, this coating may be continuous or patterned.

The thickness of the liquid crystal film usually ranges from about 6 to 100 microns. Theoretically, the thickness of the liquid crystal film is 1
does not affect the voltage difference required to switch from one optical state to another, but the switching speed is
is inversely proportional to the power. Therefore, in order to perform high-speed switching, the thickness of the liquid crystal film must be reduced.

Traditionally, the main problem in making thin film LCD panels, especially large area panels, has been maintaining a uniform thickness over the entire viewing area. If the spacing between the support plates is not constant, appreciable local switching speed variations will occur. Special gaskets are used in modern LCD panels to maintain a predetermined spacing between the support plates. Packing from which polyester membrane (Mylar) has been cut is often used with epoxy resin end seals. However, many modern manufacturers use thermoplastic packing or glass frit that doubles as a spacer and seal. In the case of a thermoplastic spacer/seal, a mirror image packing of a suitable material such as polyvinylidene chloride is applied to both support plates and the plates are heated and pressed to weld the packings together. If frit glass is used, a mirror image pattern of the frit and binder mixture is screen printed on the outer edges of both support plates. The unassembled support plates are heated to sinter the binder and partially melt the frit, and then the support plates are stacked and the frit is melted and adhered again to form an integral peripheral spacer and seal.

As the dimensions of LCD panels increase, it becomes increasingly difficult, if not impossible, to maintain a constant spacing between the support plates using only peripheral spacers. This problem becomes extremely noticeable in the case of extremely thin LCD panels, since even a slight change in the spacing between the supporting plates results in a large rate of change in the liquid crystal film thickness. One solution to this problem was to use thick glass plates to increase strength. A 13 mm thick glass plate was used to minimize spacing variations in extremely thin LCD panels. Another solution has been to use a small pad of polyester membrane in the center of stacked glass plates to maintain constant spacing. Yet another method is
Heat-resistant grids were interspersed over the entire display area before the panels were assembled, and small glass beads were mixed into the liquid crystal material.

However, all of the above-mentioned solutions have significant drawbacks. Using a thick glass plate increases the size and weight of the display panel. Pads of polyester film are not only difficult to apply, but also obstruct (make unusable) a portion of the display area. The heat-resistant grid and glass beads attract the thin electrode coating formed on the inner surface of the support plate and are difficult to adhere to sufficiently firmly.

Furthermore, in Japanese Patent Application Laid-Open No. 49-113598, in order to maintain a constant distance between a pair of panels of a liquid crystal device with a relatively large screen, one panel on which a conductive pattern is formed is made of polyester or glass. A dot-shaped primary spacer with a high melting point of about 5 to 50 μm is formed by vapor deposition, and a low-melting point dot-shaped secondary spacer of about 0.5 μm is added to it by vapor deposition, and the other panel having a conductive pattern is melted on top of it. Arrived,
A liquid crystal device is disclosed that has spacers distributed over the entire display surface. However, in this device, by forming the dot spacers on a panel surface having a conductive pattern and joining two spacer parts, not only the height of the final dot spacers becomes uneven, but also the structure This becomes complicated, and there is a risk that a part of the display active area may become inoperable, resulting in a decrease in the resolution of the panel or a deterioration in the quality of displayed characters and graphics.

Furthermore, in high-precision waveform display devices such as oscilloscopes, a grid-like scale is generally formed over the entire display area as a measurement standard for the amplitude and time of the waveform, but such a scale may be formed outside the support plate or on an external scale plate. If the support plate is thick, a parallax error will occur, and the error increases particularly when the support plate is thick. However, an LCD panel for waveform display observation with an internal scale does not yet exist.

〔the purpose〕

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved waveform display LCD panel having uniform display characteristics over substantially the entire display area and having an internal scale that avoids parallax errors when observing waveforms.

Another object of the present invention is to provide a matrix type LCD panel having spacers and scales that do not interfere with the display of the matrix type display elements.

[Summary of the Invention] The LCD panel of the present invention has a plurality of transparent strip-shaped electrodes coated on opposing surfaces of two insulating support plates, at least one of which is transparent, in a perpendicular relationship, so that a large number of display areas are formed at the intersections of the electrodes. (matrix), and in the dot-shaped spaces between the matrices, specifically, in the part where the mutual gaps of both the orthogonal electrodes overlap, dielectric dot-shaped spacer elements of a constant height are formed in the shape of graduation lines. During this time, the liquid crystal is injected and sealed. In other words, the present invention is an LCD panel for waveform display in which spacers and permanent visible scales are formed almost over the entire active display area of the LCD panel to avoid interference with displayed information.

〔Example〕

1 and 2 show a partially enlarged front view and a further enlarged sectional view of the matrix type LCD panel 10. FIG. However, in this figure, the spacer 16 is formed in all the dot-shaped spaces between the electrode intersections, in other words, in the spaces between the electrodes that are not obstructed by either of the two orthogonal strip-shaped electrodes, which solves the problem of the present invention. Please note that the scale lines are not selectively formed. Panel 10 consists of a pair of glass plates 12, 14 spaced apart by a number of spacers 16. A liquid crystal (LC) substance 18 is filled between the glass plates.
The LC material 18 is prevented from leaking by sealing (not shown) with an epoxy compound or other desired material around the periphery of the two stacked glass plates.

Each of the support plates 12, 14 has a transparent electrode on its inner wall to apply an electric field to selected areas of the LC film. The front plate 12 has a plurality of parallel strip-shaped column electrodes 20, each formed to traverse a plurality of similarly shaped row electrodes 22 provided on the back plate 14. The panel thus has a two-dimensional rectangular array or matrix of electrodes having intersections (overlapping portions), each of which is individually driven by known methods to display information such as a waveform. A metal contact pad 21, 23 is provided at one end of each strip electrode 20, 22 to connect the display panel to the appropriate matrix addressing circuit.

If the spacer 16 is formed of a dielectric material such as polyimide, it will neither dissolve nor chemically react with the LC material. The spacers are formed by photopatterning techniques and distributed over a significant portion of the imaging area of the LCD panel to maintain a constant spacing between the support plates in the viewing area. Spacer 16 of LCD panel 10 is provided within the gap between electrodes 20 and 22. Therefore, although the supporting plate spacers are distributed over the entire image display area of the panel, each spacer is located in an inactive (non-operating) area, that is, in a portion other than the electrode intersection, so that interference with the displayed waveform ( interference) will not occur. Further, if the cross section of the spacer is made sufficiently small, for example, 0.05 mm square or less, it is almost impossible to see with the naked eye from a normal distance, but of course it is clearly visible when viewed up close.

Various methods can be considered for manufacturing this dielectric spacer. A preferred method is to first apply a uniform layer of polyimide or other suitable material to the inner surface of one of the plates after forming the strip electrodes on the inner surface of the support plate using conventional techniques. Then,
A desired pattern of spacers 16 is formed by photoetching the dielectric layer. Alternatively, the spacer elements may be formed by depositing dielectric material at photographically determined locations on the plate. As an example, a method for manufacturing an LC matrix display panel having an array of dielectric spacers of a desired height within the effective tube surface of the panel is shown below.

The starting material for forming the front and back electrode plates of panel 10 is float glass coated with a transparent conductive layer of indium tin oxide (ITO) (approximately 100 ohms per square). Such glasses are commercially available from Optical Coatings Laboratory, Inc. The back plate is made of glass with a thickness of about 3 mm, and the front plate is made of glass with a thickness of about 1.5 mm.
After cutting these glasses to desired dimensions, the ITO coated plate is cleaned and coated with a photoresist such as Shipley's AZ1350J. The resist layer on each plate is exposed and developed, leaving a pattern of resist covering the ITO to form electrodes 20 and 22, respectively. The uncovered portions of the ITO coating are etched away and the remaining resist is removed from both support plates.

A metal layer is then provided on the end of each strip electrode to form electrical contact pads 21,23.
This is preferably accomplished by forming a palladium layer approximately 2000 Å thick on the electrode-forming surfaces of both support plates. Note that in order to improve adhesion with palladium, it is preferable to first form a thin titanium layer of about 200 Å. Both metal layers are then photoetched using known methods to form contact pads.

After the electrode structure is completed, dielectric spacers are formed on the inner surface of the back plate 14. First, the base board is 125
C. for about 12 hours, and then spin coated with undiluted Union Carbide A-187 at 2000 rpm for about 30 seconds. This preliminary layer of epoxy silane, which acts as an adhesive for the next polyimide layer, is dried in an oven at 125° C. for about 10 minutes and then cooled. A polyimide solution of a 3:1 by volume mixture of DuPont 2550 polyimide material and N-methyl-1-pyrrolidine is then spun on at 4000 rpm for 30 seconds. Approximately 1 at 125℃
After drying for an hour, the substrate is covered with a uniform polyimide coating approximately 6 microns thick.

The polyimide substrate is coated with a positive photoresist such as Shipley AZ-119 and then exposed to actinic radiation in a conventional manner. After this exposure, the resist layer is developed in a solution of Shipley AZ-303 developer and water in a 1:4 volume ratio. This developer solution removes the exposed portions of the photoresist layer and the underlying polyimide layer. Remove remaining photoresist from photoresist.
Remove the supporting plate 1 with a suitable solvent such as thinner.
A two-dimensional array of polyimide spacers 16 is formed in the gaps in the panels described above. The polyimide is stabilized by baking it in air at 150°C for 30 minutes, then at 240°C for 1 hour, and then at 400°C for 3 minutes.

As is clear from the above description, the height of the spacer depends on the thickness of the polyimide layer forming it. In the above example, a spacer with a height of 6μ is obtained, but by changing the viscosity, temperature or rotation time (speed) of the polyimide solution, or a combination thereof, the height can be increased to 1μ.
It is also possible to make short spacers. To avoid visibility, the spacer is preferably about 0.05 mm or less. In any case, it is generally difficult to form a spacer with a cross section less than the thickness of the polyimide layer forming the spacer. To improve the adhesion between the polyimide spacers and the glass substrate, a thin underlayer of titanium oxide or zirconium oxide is preferably applied to the support plate before the polyimide layer application step.

By overlapping the front and back plates formed in this way, filling the interior with a desired LC substance, and sealing the periphery of the glass plate with epoxy adhesive, an LCD can be created.
The panel is completed. Prior to assembly, the inner surface of the support plate is treated by known methods to obtain the desired molecular arrangement, i.e.
Make the LC substance homeotropic or homogeneous. If necessary, a polarizing plate may be provided on the external front surface of the front plate.

Next, FIG. 3 shows a diagram for waveform display according to the present invention.
1 shows a portion of a front view of a preferred embodiment of an LCD panel. That is, in this LCD panel 30, the spacer between the electrodes shown in FIGS. 1 and 2 is selectively formed in the shape of a permanent visible scale 34 over almost the entire observation area of the panel. . This scale 34 is formed almost like a grid, and there are additional fine increments corresponding to 1/5 of one scale on the horizontal and vertical center lines, and furthermore, 90% of the waveform,
Contains the number 36 to indicate the 100% point and a dotted line to indicate the 100% point, and is similar to a conventional oscilloscope cathode ray tube (CRT).
It is similar to the scale of Of course, since this scale line 34 is formed in the gap between the electrodes as shown in FIG.
The spacer 32 constituting the scale line 34 appears to be rod-shaped, but when enlarged, it consists of a series of dot-shaped spacer elements.This scale/spacer is also made of a visible material such as polyimide and corrosion resistant to liquid crystal using the aforementioned photopatterning technology. It will be appreciated that the uniform height can be controllably and reproducibly formed using a flexible dielectric material.

Although one preferred embodiment of the LCD panel of the present invention has been described above, it will be understood that various changes and modifications can be made without departing from the gist of the present invention.

〔effect〕

As understood from the above description, the present invention
According to LCD panels, spacers are formed in the gaps between display matrices using a dielectric material such as polyimide in the shape of a predetermined scale using photo patterning technology, so that display characteristics are uniform over almost the entire waveform display area. A matrix type LCD panel having a spacer and internal scale without parallax error can be obtained.
Therefore, a waveform display device that can replace a CRT such as an oscilloscope, which requires uniform display characteristics and low visual error, can be realized with lower power consumption, smaller size, and lighter weight than when using a CRT.

[Brief explanation of drawings]

1 and 2 are enlarged front and sectional views for explaining the LCD panel of the present invention, and FIG. 3 is a partial front view of a preferred embodiment of the LCD panel of the present invention. In the figure, 10 and 30 are LCD panels, 12 and 14 are insulating support plates, 18 is a liquid crystal body, 20 and 22 are electrodes,
16 and 32 are dot-shaped spacer elements, and 34 is a scale.

Claims (1)

[Scope of Claims] 1. A plurality of transparent parallel strip-shaped electrodes are arranged on opposing inner surfaces in a mutually orthogonal relationship, and a large number of matrix-shaped display elements are formed by the intersections of both electrodes, at least one of which is transparent. a pair of insulating support plates; and a visible dielectric material formed to a uniform thickness in a portion of the insulating support plate where the mutual gap between the parallel strip-shaped electrodes on one side overlaps with the mutual gap between the parallel strip-shaped electrodes on the other side. dot-shaped spacer elements, and a liquid crystal substance injected and sealed between the two insulating support plates, and the dot-shaped spacer elements are distributed in the shape of a scale line over almost the entire area of the plurality of matrix-shaped display elements. A liquid crystal display panel characterized in that the spacer serves as a spacer for maintaining a constant distance between the two insulating support plates and as a scale for measuring waveforms and the like displayed by the matrix display element.