JP2759192B2 - Method for manufacturing NCAP liquid crystal display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" This invention relates to NCAP (Nematic Curvilinear Aligned Ph
ase: Nematic curve type alignment phase) The present invention relates to a method for manufacturing a liquid crystal display device.

[Prior Art] The NCAP liquid crystal display element is composed of an NCAP liquid crystal layer 10 in which fine liquid crystal spheres (liquid crystal capsules) 2 are dispersed in a polymer matrix 13 as shown in FIG. 5 or FIG. As shown, electrodes 21 and 31 made of a transparent conductive layer of metal oxide are formed on the inner surface, respectively, and have a structure sandwiched between two substrates 20 and 30 each made of a flexible plastic film, When no voltage is applied between the electrodes 21 and 31, the liquid crystal molecules 3 in the liquid crystal sphere 2 are arranged along the outer wall of the liquid crystal sphere 2 as shown in FIG. Are scattered on the surface and inside of the liquid crystal sphere 2, so that the NCAP liquid crystal layer 10 becomes opaque, and when a voltage is applied between the electrodes 21 and 31, the liquid crystal molecules 3 change the electric field E as shown in FIG. Are aligned along the direction, and the incident light L goes straight,
The NCAP liquid crystal layer 10 becomes transparent.

To manufacture such an NCAP liquid crystal display element, conventionally,
Liquid crystal is added to a polyvinyl alcohol aqueous solution obtained by dissolving polyvinyl alcohol as a polymer in water, and the polyvinyl alcohol aqueous solution to which the liquid crystal is added is stirred by a colloid mill and emulsified to form an emulsion in which liquid crystal spheres are dispersed. The NCAP liquid crystal layer is applied to one side of a substrate having electrodes formed on one side and dried to form an NCAP liquid crystal layer.Another substrate having electrodes formed on one side on the opposite side of the NCAP liquid crystal layer from the side on which the above-described substrate exists. Is fixed on one side.

"Problems to be Solved by the Invention" The light transmittance of the NCAP liquid crystal layer varies continuously within a range from a certain voltage value Vof to another higher voltage value Von. , Their voltage values Vof and V
On largely depends on the diameter of the liquid crystal sphere in the NCAP liquid crystal layer.

That is, as shown in FIG. 7, when the diameter of the liquid crystal sphere 2 in the NCAP liquid crystal layer 10 is large, for example, 6 μm,
The number of walls of the liquid crystal sphere 2 in the direction of the electric field is small.
And the alignment force received by the liquid crystal molecules from the outer wall of the liquid crystal sphere 2 is weakened. Therefore, even when the same voltage is applied, as compared with the case where the diameter of the liquid crystal sphere 2 is small as shown in FIG. As a result, the liquid crystal molecules are easily aligned in the direction of the electric field, and as shown in FIG. 9, the voltage values Vof and Von decrease, and the light transmittance changes sharply between them. On the other hand, when the diameter of the liquid crystal sphere 2 is as small as 1 μm as shown in FIG. 8, the light transmittance changes sharply between the voltage values Vof and Von as shown in FIG. However, both are higher. When the diameter of the liquid crystal sphere 2 varies, for example, in the range of about 1 μm to 6 μm, as shown in FIG. 11, the voltage value Vof decreases, the voltage value Von increases, and the light transmittance between the two increases. Changes slowly. Specifically, the voltage value Von when the diameter of the liquid crystal sphere 2 is large as described above is 5 V or less, but the voltage when the diameter of the liquid crystal sphere 2 is small and when the diameter of the liquid crystal sphere 2 varies as described above. The value Von can be as high as 20V to 30V.

Incidentally, it is desirable that the NCAP liquid crystal display element be driven by a transistor logic circuit like other liquid crystal display elements, and the power supply voltage of the transistor logic circuit is generally set to 5 V. As shown, it is desirable that the voltage value Von for maximizing the light transmittance is 5 V or less, that is, the diameter of the liquid crystal sphere 2 is large, for example, 6 μm as shown in FIG. Moreover, in general, in a liquid crystal display element, for example, the duty is 1/64
To perform the multiplex operation, the ratio Von / Vof between the voltage value Von that maximizes the light transmittance and the voltage value Vof that minimizes the light transmittance
It is clear from the need to make
In order for the AP liquid crystal display element to perform the multiplex operation, the light transmittance needs to change sharply between the voltage values Vof and Von as shown in FIG.

However, in the conventional manufacturing method described above,
The polyvinyl alcohol aqueous solution to which the liquid crystal is added is stirred by a colloid mill and emulsified to form an emulsion in which liquid crystal spheres are dispersed, and this emulsion is applied to a substrate and dried to form an NCAP liquid crystal layer. In other words, the diameters of the liquid crystal spheres in the NCAP liquid crystal layer become uneven and vary in the range of, for example, about 1 μm to 6 μm.
As shown in the figure, as the voltage value Von increases, the voltage value Vo
The light transmittance changes gradually between f and Von,
The obtained NCAP liquid crystal display device is not suitable as a liquid crystal display device and has the inconvenience that a multiplex operation cannot be performed.

In view of the above, the present invention provides a method of manufacturing an NCAP liquid crystal display element, in which the diameter of a liquid crystal sphere can be reliably and easily made constant and desired.

[Means for Solving the Problems] In the present invention, a polyvinyl alcohol aqueous solution is caused to flow along a partition on one side of a partition having a large number of through-holes having a constant diameter, and polyvinyl is passed through the through-hole of the partition from the opposite side of the partition. The liquid crystal is injected with a certain pressure into the alcohol aqueous solution to form an emulsion in which the liquid crystal spheres are dispersed in the polyvinyl alcohol aqueous solution, a part of the water in the emulsion is evaporated, the viscosity is increased, and the emulsion is placed on one side. Apply to one side of the substrate on which the electrodes are formed, and dry to form an NCAP liquid crystal layer.One side of another substrate having electrodes formed on one side on the side opposite to the side where the above-mentioned substrate exists in the NCAP liquid crystal layer. Is fixed.

"Action" In the production method of the present invention, which employs the above method,
The diameter of the liquid crystal spheres in the emulsion, that is, in the NCAP liquid crystal layer, is determined by the diameter of the through hole formed in the partition wall and the pressure at which the liquid crystal is injected into the aqueous polyvinyl alcohol solution through the through hole. Since the diameter and the pressure are made constant, the diameter of the liquid crystal sphere can be reliably made constant, and the diameter of the liquid crystal sphere can be easily made a desired size by selecting the diameter and the pressure of the through hole.

FIG. 1 shows an example of an emulsion preparation step in the manufacturing method of the present invention. A liquid crystal tank 41 is inserted by inserting a pipe having a large number of through holes 43 with a constant diameter as a partition wall 42 in the center of the liquid crystal tank 41. The inside is separated into the inside and the outside of the partition wall 42, the polyvinyl alcohol aqueous solution 11 is arranged in another tank 44, and the polyvinyl alcohol aqueous solution 11 is partitioned by the pump 45.
While flowing at a constant flow rate along the partition 42 inside 42,
The liquid crystal 1 is disposed in a liquid crystal tank 41, and a certain pressure is applied to the liquid crystal 1 by a pressure pump 46 in a direction perpendicular to the flowing direction of the aqueous polyvinyl alcohol solution 11, that is, in a direction in which the through hole 43 penetrates. The liquid crystal 1 is injected into the aqueous polyvinyl alcohol solution 11 through the liquid crystal, and the liquid crystal spheres 2 are dispersed in the aqueous polyvinyl alcohol solution 11 as shown in FIG. In FIG. 1, the polyvinyl alcohol aqueous solution 11 is circulated between the inside of the tank 44 and the inside of the partition wall 42, and the circulation is stopped when the required amount of the liquid crystal spheres 2 is obtained in the polyvinyl alcohol aqueous solution 11. Thus, an emulsion in which the required amount of the liquid crystal spheres 2 is dispersed in the aqueous polyvinyl alcohol solution 11 is obtained in the tank 44.

The diameter of the liquid crystal spheres 2 in the emulsion thus obtained is determined by the diameter of the through hole 43 formed in the partition wall 42 and the above-described pressure P shown in FIG. Specifically, when the interfacial tension between the liquid crystal 1 and the aqueous polyvinyl alcohol solution 11 is γ, the contact angle is θ, the diameter (diameter) of the through hole 43 is 2R, and the acceleration of gravity is g, the pressure P is In this case, when the diameter of the through hole 43 is set to 2 μm, the diameter of the liquid crystal sphere 2 is about three times, that is, about 6 μm.

The emulsion in which the liquid crystal spheres having a certain diameter are dispersed as described above evaporates a part of the water portion to increase the viscosity.

Next, as shown in FIG. 3, the emulsion 12 whose viscosity has been increased is coated on one surface of a substrate 20 made of a flexible plastic film on which an electrode 21 made of a metal oxide transparent conductive layer is formed. The NCAP liquid crystal layer 10 is applied and dried completely.

Next, as shown in FIG. 4, the substrate of the NCAP liquid crystal layer 10 is formed.
On one side opposite to the side where 21 exists, one side of a substrate 30 made of a flexible plastic film on which an electrode 31 made of a transparent conductive layer of metal oxide is formed is fixed, and the NCAP liquid crystal layer 10 has an inner surface. 2 with electrodes 21 and 31 formed
The structure is sandwiched between the substrates 20, 30.

Note that the substrates 20 and 30 may be glass substrates or the like. Further, since the NCAP liquid crystal display element can be configured as a reflective display, one of the substrate 20 and the electrode 21 and the substrate 30 and the electrode 31 may be opaque.

[Effects of the Invention] As described above, according to the present invention, the diameter of the liquid crystal spheres in the NCAP liquid crystal layer can be reliably and easily made to be a constant and desired size. An NCAP liquid crystal display element capable of operating can be obtained reliably and easily.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an emulsion forming step in the manufacturing method of the present invention, FIG. 2 is a view showing a state in which liquid crystal spheres are formed in the step, FIG. 3 and FIG.
FIG. 5 is a cross-sectional view showing another step in the manufacturing method of the present invention, FIG. 5 is a view showing the state of liquid crystal molecules and incident light when no voltage is applied to the NCAP liquid crystal layer, and FIG. FIGS. 7 and 8 show the state of the liquid crystal molecules and the incident light when a voltage is applied to the NCAP liquid crystal layer. FIGS. Eleventh
The figure is a diagram showing an aspect of the relationship between the voltage applied to the NCAP liquid crystal layer and the light transmittance of the NCAP liquid crystal layer.

Claims (1)

(57) [Claims] An aqueous polyvinyl alcohol solution flows along one side of a partition wall having a large number of through-holes having a constant diameter along a partition wall, and a predetermined pressure is applied to the aqueous polyvinyl alcohol solution through the through-hole from the opposite side of the partition wall. Liquid crystal is injected to form an emulsion in which liquid crystal spheres are dispersed in the aqueous polyvinyl alcohol solution. Next, a part of the water content of the emulsion is evaporated to increase its viscosity. Is applied on one side of the substrate on which is formed and dried to form an NCAP liquid crystal layer. Next, one side of another substrate having an electrode formed on one side of the NCAP liquid crystal layer on the side opposite to the side where the substrate exists. A method for manufacturing an NCAP liquid crystal display element that fixes the side.