JPS6131870B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase change type display panel, and more specifically, the present invention relates to a hysteresis state at the time of phase transition (once the homeotropic state is forcibly brought to a homeotropic state by an electric field, and then the focal state is changed by lowering the voltage). This is a phase transition type that can apparently lengthen the transition time of the focal conic state (which is the intermediate stage of the phase transition to the nic state, which is a state in which the focal conic state retains homeotropy at a stable potential), that is, it can lengthen the scanning allowable time. This relates to display panels.

Recently, phase change type display panels have attracted attention due to their usefulness due to their low power consumption and memory functions, and research and development is progressing. In particular, we are focusing on matrix drive methods that eliminate crosstalk, which has traditionally been the biggest challenge in matrix-type display panels (IEICE Electronic Components and Materials Study Group Materials).
CPM75-11) can be applied, so it is expected to have the potential to drive large matrices.

A phase change type display exhibits a voltage-transmittance characteristic as shown in FIG. 1, for example. That is, as shown in Fig. 1, by increasing the pressure, it is once scattered (focalconic state: F) and then disappears (homeotropic state:
H).

When the pressure is suddenly lowered, it scatters for a short period of time (Sec) and disappears (vortex-like structure: S).

When the value is gradually lowered, scattering occurs through a hysteresis state (metastable homeotropic state: H'), and scattering continues without an electric field (fieldless focal conic state: F').

Alternatively, even with the waveforms shown in FIG. 2A and B, writing (scattering) as shown in FIGS. 2D and E occurs, respectively.

However, in order to increase the number of matrix display lines using a large panel in this method, a hysteresis state of phase transition must be maintained for a long time when the voltage increases and decreases. That is,
If all the writing of the scattering display is not completed in the transparent hysteresis state (H'), the hysteresis state will gradually break down from the outline of the pixel formed by the intersection of the X-axis electrode group and the Y-axis electrode group to the inner periphery. That is, as the transition from the homeotropic state to the focal conic state progresses, scattering begins and the transmittance decreases as shown in FIG. be. This hysteresis state is affected by many factors such as cell thickness, temperature, orientation state, etc., and the fluctuation range is large.In practice, it becomes increasingly difficult to lengthen the hysteresis state as the number of rows increases. It is considered a drawback.

The present inventor researched a method to remove or extend the limit to this multi-line configuration, and by shielding light from the outline of the pixel to the inner periphery, even if hysteresis begins to break down, this is done at the center of the pixel. By making it invisible to the observer for a relatively long period of time as it progresses to the section, we succeeded in lengthening the apparent hysteresis state and extending the limit to multi-line formation while maintaining the characteristics as they are. This has led to the present invention.

The present invention will be explained in detail below.

FIG. 3 is a plan view showing an example of a phase change type display panel, in which the panel 1 has a front electrode provided with a large number of X-axis electrode groups X ₁ , X ₂ ......Xm, ...... Substrate 2 and multiple Y-axis electrode groups Y ₁ , Y ₂ ...
. . ., Yn, . A mixed composition of known nematic liquid crystals having positive or negative dielectric anisotropy such as azoxy-based, pyrimidine-based, phenylcyclohexane-based, etc., with the basic composition having positive dielectric anisotropy as a whole, This is filled with a phase change type liquid crystal such as a composition containing 5 to 30% of an optically active compound, such as a cholesterol derivative or a compound having an optically active group such as chiral nematics, and the surrounding area is further sealed. Become. In such a phase transition type display panel, the present invention provides a group of X-axis electrodes (the m-th X-axis electrode Xm is shown in FIG. 4) on at least one surface of the front electrode substrate, as shown in FIG. ) and the Y-axis electrode group (FIG. 4 shows the n-th Y-axis electrode Yn) in a portion corresponding to the inner peripheral portion 6mn of the outline 5mn of the pixel 4mn. If this light-shielding material layer is provided in a portion corresponding to the inner peripheral portion 6mn, the desired purpose can be achieved, but it is better to simultaneously provide the light-shielding material layer on the outer peripheral portion 7mn of the outline 5mn. This is preferable because it has advantages in manufacturing, such as not impairing the function of the panel even if the alignment with the light-shielding material layer is slightly misaligned. The light-shielding material layer 8 can be provided on one side of the front electrode substrate 2 as shown in FIGS. 5 and 6, but if it is provided on the side opposite to the electrode as shown in FIG. This is not very preferable because it causes parallax and a viewing angle that impairs the effects of the present invention. Further, it is also possible to provide the light shielding material layers on both sides of the substrate 2, and in this case, if the light shielding material layers on both sides are aligned and provided, it has the effect of limiting the viewing angle.

To provide a light shielding material layer on at least one surface of the front electrode substrate, aluminum, titanium, chromium, iron, cobalt, nickel, silver, gold, selenium,
A method of vapor depositing, sputtering or vapor depositing metals such as tin, indium, or opaque substances such as carbon, zinc sulfide, silicon, etc. through a mask, vapor depositing with a resist placed in advance,
A method of coating with a sputter or vapor deposition and then peeling off only the resist part, silver, iron, lead, chromium, gold,
A method of printing opaque insulating materials such as conductive paste containing powders of zinc, aluminum, etc. or inks containing pigments or dyes of black, red, blue, green, and other colors, and patterned light-shielding sheets of plastic, ceramic, etc. This can be done by a method such as bonding through an adhesive or a pressure-sensitive adhesive. Alternatively, although not shown, a light-shielding material layer is provided in advance on one surface of a transparent sheet or plate made of glass, plastic, etc. by the method described above, and then attached to the outer surface of the front electrode substrate via an adhesive or pressure-sensitive adhesive. It is also possible to fix it by attaching it, fixing it with clips, screws, or any other arbitrary method.

The light-shielding material layer may be formed of a conductive material when provided on the electrode surface side of the front electrode substrate as shown in FIG. 5, but it is preferably formed of an insulating material. At this time, in order to use a conductive material, an insulating film may be used. Furthermore, when a light-shielding material layer is also provided on the outer periphery of the pixel outline as described above, the outer periphery of adjacent pixels may be connected, and the light-shielding material layer may also be provided at a position corresponding to this connection. I can do it. In this case, the fifth
In order to provide a light-shielding material layer directly on the electrode surface side of the front electrode substrate as shown in the figure, it is necessary to use an insulating material to prevent short circuits, but even conductive materials can be used if an insulating film is interposed. .

As is clear from the above description, according to the present invention, it is possible to increase the number of rows of the panel by apparently lengthening the transition time of the hysteresis state at the time of phase transition.

Next, the present invention will be further specifically explained by showing examples.

Example Two electrode plates were prepared in which 250 NESA electrodes of 0.4 mm were formed at a pitch of 2 electrodes/mm on a glass substrate, and an electrode protective layer of silicon oxide with a thickness of 800 Å was provided by vapor deposition.

Next, a photosensitive resist was applied onto the electrode protective layer of one electrode plate, exposed and developed, and a matrix of 0.35 mm square with a pitch of 2 resists/mm was superimposed on the NESA electrode. After coating low-reflectivity chromium on this substrate by sputtering method, the chromium on the resist is peeled off by removing the resist.
A light-shielding layer with a matrix of transparent windows of 0.35 mm square was formed.

Next, a vertical alignment agent (Surf-in 150, manufactured by Dainippon Ink Co., Ltd.) was applied onto both substrates, and the electrode sides of both substrates were opposed to each other via a spacer to form a cell with a thickness of 8 μm. Separately, 40 parts of p-methoxybenzylidene-p-n-butylaniline, 30 parts of p-ethoxybenzylidene-p-n-butylaniline, p-
n-butoxybenzylidene-p-cyanoaniline
A memory type liquid crystal composition consisting of 20 parts of cholesteric nonanoate and 10 parts of cholesteric nonanoate (the above parts indicate parts by weight) was prepared and injected into the cell and sealed.

In addition, a similar cell was fabricated except that it did not have a light-shielding layer, and the apparent allowable scanning time was compared.
In other words, after applying a 30V (zero peak voltage) rectangular wave (1KHz) and stepping down to 15V (zero peak voltage), we measured the time it took for scattering to be visually recognized. In some cases, the allowable scanning time increased significantly to 14 seconds.

[Brief explanation of the drawing]

Figure 1 is a diagram showing voltage-transmittance characteristics in a phase change display panel, Figure 2 is a diagram showing temporal changes in voltage and transmittance in a phase change display panel, and Figure 3 is a diagram showing changes in voltage and transmittance over time in a phase change display panel. FIG. 4 is a plan view schematically showing one pixel portion by enlarging a part of the phase change display panel of the present invention, and FIGS. 5 and 6 are the pixel portions shown in FIG. 4. FIG. 3 is a schematic end view of a cut portion cut parallel to an X-axis electrode. 1 ...Phase change display panel, 2...Front electrode substrate, 3...Rear electrode substrate, 4mn...m
A pixel formed by the intersection of the th X-axis electrode and the nth Y-axis electrode, 5mn...the outline of the pixel 4mn,
6mn...inner periphery of contour 5mn, 7mn...outer periphery of contour 5mn, 8...light shielding material layer, Xm...
...mth X-axis electrode, Ym...nth Y-axis electrode.

Claims (1)

[Claims] 1. A front electrode substrate on which a large number of X-axis electrode groups are provided and a back electrode substrate on which a large number of Y-axis electrode groups are provided are placed opposite to each other with their respective electrode surfaces facing inside, with both electrode groups crossing each other. In a phase change type display panel in which a phase change type liquid crystal is filled with a phase change type liquid crystal and the periphery is further sealed, the electrode group is formed by the intersection of an X-axis electrode group and a Y-axis electrode group on at least one surface of the front electrode substrate. A phase change display panel characterized in that a light-shielding material layer is provided in a portion corresponding to the inner peripheral portion of the outline of a pixel.