JPS62196624A - Production of wedge type liquid crystal cell - Google Patents

Abstract

PURPOSE:To obtain simply and inexpensibly the prescribed and highly accurate gradient of cell thickness and to reduce the deformation of transparent substrates due to external force of the like by deflecting a pair of transparent substrates with a prescribed deflection curve by previously applied stress. CONSTITUTION:In a wedge type liquid crystal cell 10, spacers 15, 16 are inserted between both the ends of the transparent substrates 11, 12 consisting of glass plates or plastic plates and external force is applied to the center part of the substrates 11, 12 until both the substrates 11, 12 are bent to form the cell thickness gradient of liquid crystal 13 in inside the substrates 11, 12. Since stress is applied to the substrates 11, 12 under said structure, the substrates 11, 12 are partially sticked to each other by bonding agents 21, 22 or pressure is impressed from the outside to hold the shape of the wedge type liquid crystal cell 10. Since the thickness of the cell, i.e. the cell gap, is set up by a deflection curve obtained by bending the substrates 11, 12 by the stress, the required cell gap can be inexpensively, simply and highly accurately required cell gap can be inexpensively, simply and highly accurately obtained and stabilized against the external force or the like because internal stress is previously applied to the substrates 11, 12 so as to stretch them.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a novel structure of a model liquid crystal cell having a gradient in cell thickness.

The model liquid crystal cell according to the present invention can be used for the same purpose as the conventional model liquid crystal cell. However, in addition to being used to measure the pitch of cholesteric liquid crystals, compensating plates with a retarded slope using liquid crystals, and to study the effect of cell thickness in various liquid crystal devices.

<Prior Art> Conventionally, model liquid crystal cells have been created using the following two methods.

■ Linear model liquid crystal cell As shown in Figure 8, this liquid crystal cell consists of two glass substrates that have been treated to orient the liquid crystal on their surfaces! , 2 are placed facing each other with a spacer 3 interposed between their ends, and liquid crystal 5 is injected into the gap.

The advantage of this structure is that since the relationship between the position of the liquid crystal cell and the cell thickness there is linear, it is easy to calculate the cell thickness from the position.

However, the disadvantage is that the glass substrate 1.2 is deformed by a slight external force or the surface tension of the liquid crystal 5. , 2 are difficult to keep flat, and the desired linear cell thickness gradient cannot be obtained. Such disadvantages are fatal to accurate measurements.

(2) Model liquid crystal cell using lenses As shown in FIG. 9, this liquid crystal cell has a spherical or cylindrical lens 6 and a flat plate glass 7 arranged, and liquid crystal 8 is injected into the gap between them. The accuracy of the cell thickness of a liquid crystal cell with this structure is determined by the processing accuracy of the lens. Generally, a major disadvantage of this method is that the highly accurate lens with a radius of curvature of 10 to 100 m is expensive.

<Objective of the Invention> Therefore, the object of the first invention is to provide a model liquid crystal cell that can easily and inexpensively obtain a desired cell thickness gradient with high precision, and that causes less deformation of the transparent substrate due to external forces. Our goal is to provide the following.

A second object of the invention is to provide a manufacturing apparatus that can easily manufacture the liquid crystal cell of the above model.

<Structure of the Invention> In order to achieve the above object, the liquid crystal cell of the model of the first invention bends a pair of transparent substrates along a predetermined deflection curve by a stress given in advance, and also bends the pair of transparent substrates by The liquid crystal layer sandwiched between them is characterized by being fixed so that the layer thickness at at least one end portion is a constant value, and the internal layer thickness is substantially zero at at least one place or more.

Further, the manufacturing apparatus of the second invention includes a table, a gate-shaped frame fixed to the table and having an opening into which a pair of transparent substrates are inserted, and a pair of transparent substrates inserted into the opening. The device is characterized by comprising a presser plate that presses the presser plate, and a screw member that presses the presser plate toward the base plate.

According to the model liquid crystal cell of the first invention, stress is applied to the transparent substrate to cause it to bend, and the cell thickness, that is, the cell gap, is set by the bending curve, so that the desired cell gap can be easily and accurately set at low cost. Also, since internal stress is generated in the transparent substrate in advance and the transparent substrate is kept in a tensioned state, it becomes stable against external forces.

Further, according to the manufacturing apparatus of the second aspect of the invention, the transparent substrate can be easily bent and fixed by pressing the transparent substrate against the stand with the screw member through the holding plate.

<Example> As shown in FIG. 1, the liquid crystal cell 10 of this model has spacers 15, 16 sandwiched between transparent substrates 11, 12 made of glass plates or plastic plates at both ends, and a transparent substrate 1! i,ll,
Apply external force to the middle part of 12 and bend it until it fits tightly.
A cell thickness gradient of liquid crystal l→ is created inside.

In this structure, stress is applied to the transparent substrates 11 and 12, so in order to maintain the shape of the model liquid crystal cell IO,
As shown in Figure 2, the transparent substrates 11 and 12 are partially covered with adhesive 2.
1. Glue in step 22 or apply pressure from the outside. As a method of applying pressure, a clip 25 may be used as shown in FIG. 3, and one end of the transparent substrates 11 and 12 may be pressed and fixed together, or a manufacturing apparatus shown in FIG. 4 may be used. .

In this manufacturing device, a gate-shaped frame 3 is attached to one end of the table 31.
A pair of overlapping transparent substrates 11.1
Insert the end of 2. Then, in the opening 34, the presser plate 3 is extended over the entire length in the width direction on the transparent substrate ll.
3, and by turning the screw member 35 screwed into the horizontal part of the frame 32, the presser plate 33 is pushed down,
The ends of the transparent substrates 11 and 12 are sandwiched between the holding plate 33 and the stand 31, and are fixed in a bent state by applying stress to them.

In this way, this manufacturing apparatus has a simple structure, and can apply an external force to the transparent substrates 11, 12, generate internal stress therein, and fix the transparent substrates 11, 12 in a bent state.

In addition, in the liquid crystal cell 10 of this model, as shown in FIG. 1.2, the spacer 15 on the thicker side of the cell may be made of any material that has a uniform thickness and high rigidity.
Polyester, polyamide, polycarbonate, polyimide, polyolefin, Teflon, polystyrene, etc.
Most polymers can be used, and inorganic materials include vapor-deposited films of metals and metal oxides, vapor-phase reaction-deposited films, fine particle sintered bodies,
A thin piece of glass or ceramic can be used, or it can be made by etching the base glass, which is a transparent substrate, to leave a portion that will become a spacer.

Further, it is preferable to use adhesives 21 and 22 mixed with granular or rod-shaped spacers. Then, the two substrates are made to face each other so as to be in contact with each other without interposing the spacer at the part where the cell thickness is the thinnest, and the cell thickness is set to 0 μm.

The thickness of the glass substrate or the like as the transparent substrate should be determined appropriately depending on the cell thickness gradient.

In other words, a liquid crystal cell with a small cell thickness gradient has a transparent substrate 1
Since the deflection of 1.12 is small, a thick plate glass such as 5 mm thick or thicker is preferable, and for cells with a large cell thickness gradient, a thin glass plate 2 mm thick or less may be used.

The smoothness of transparent substrates such as glass substrates and plastic plates is
Although it depends on the desired cell thickness accuracy, flat polished glass or float glass is preferable (2).

The model liquid crystal cell with this structure has the following features compared to the conventional technology.

■ First, transparent substrates such as glass substrates 11.12
is cheap. The transparent substrate only needs to be finished to a level of smoothness that suits the purpose, and even if it is flat polished, it is much cheaper than polishing the lens.

■Secondly, the cell thickness of the liquid crystal cell is stable against external pressure. In this structure, the transparent substrate 11.1
This is because the liquid crystal 13 is preloaded and is in a tensioned state, so it is less susceptible to deformation due to external pressure or the surface tension of the liquid crystal 13 to be injected.

In order to fully utilize these advantages, the transparent substrates 11 and 12 in FIG. It is desirable that the condition yt3/k3≧o,oot be satisfied. This condition is
Y is the Young's modulus of the material of the cantilever, b is the width of the cantilever, and assuming that the cantilever's own weight can be ignored, the deflection y when force F is applied to the free end of this cantilever is The value of the right side of the equation, y t'/4' = 4 F, /Yb, which is a modified version of the equation bt3 given, was determined experimentally. In this way, the transparent substrate 11. $2
has stabilized.

The model liquid crystal cell of the present invention is superior to the linear model cell in this respect. That is, as described in the <Prior Art> section, the linear model cell is easily deformed by a slight external force, making it difficult to obtain the expected cell thickness gradient with good linearity. FIG. 5 shows the cell thickness gradient of the liquid crystal cell described in <Comparative Example>, and it can be seen that the curve has an irregular shape. On the other hand, the cell thickness gradient of the cell of Experimental Example 1 of the present invention, as shown in FIG. 6, is very close to the theoretically predicted curve.

This theoretically predicted curve is expressed by the following equation (1) derived from the equation expressing the deformation of a cantilever beam.

where, Represents the cell thickness at the end point.

As described above, since the theoretical formula fits well, there is an advantage that the error is small when estimating the cell thickness by the interpolation method.

(3) Thirdly, this model liquid crystal cell 10 has the advantage that it generally has a smaller curvature and can obtain a cell thickness gradient closer to a straight line than a liquid crystal cell model using lenses. 7th
In the graph of the figure, the broken line is the cell thickness distribution of a model liquid crystal cell using a lens with a circular cross section, and the solid line is the cell thickness distribution of the model cell according to the present invention. Both rank 1i
The cell thickness was calculated to be 5 Q mm and the cell thickness was 10 μm, but it can be seen that the model cell of the present invention has a smaller curvature of the cell thickness gradient and is closer to a straight line. In the model liquid crystal cell IO, the cell thickness at a certain position is calculated from a predetermined relational expression between the position and the cell thickness, so an error in position measurement becomes an error in the estimated value of the cell thickness. Therefore, the closer the cell thickness gradient is to a straight line, the more constant the error in the estimated cell thickness is regardless of the position. Therefore, the liquid crystal cell of the model of the present invention is included in the estimated cell thickness more than the liquid crystal cell of the model using a lens. The difference depending on the position of the error is small, which is excellent.

<Experimental Example 1> Two rectangular glass substrates with a thickness t of 3 mm were treated for liquid crystal alignment, a polyester film with a thickness of 30 μm was sandwiched between both ends, and the substrates were installed in the manufacturing equipment shown in Figure 4. . A model liquid crystal cell was prepared by turning the screw 35 and applying pressure. The cell thickness was measured at several locations using two-wave interferometry, and as shown in the graph of FIG. 6, it was found to be in good agreement with the theoretical value. Model liquid crystal cell length L
is 50fffffl, and the cell thickness d at the thick end point of the cell thickness. =
Since it was 32 μm, y is 16 μm. Therefore, the pitch of cholesteric liquid crystal could be measured with high accuracy using .

<Experiment Example 2> A model liquid crystal cell was created using the manufacturing equipment shown in Figure 4 in the same manner as in Experiment Example 1, except that a small amount of epoxy resin adhesive was used to bond the glass substrates. , 150
After curing the adhesive by heating at .degree. C. for 2 hours, the cell was removed from the manufacturing apparatus. When the cell thickness was measured at several locations using two-wave interferometry, it showed good agreement with the theoretical value. Injecting nematic liquid crystal into the liquid crystal cell of this model,
I created a wave plate.

<Experimental Example 3> Two 3111111 thick glass substrates provided with transparent electrodes of indium oxide and tin oxide were subjected to SiO oblique evaporation and vertical alignment treatment, and a model liquid crystal cell was prepared in the same manner as in <Experimental Example 2>. After injecting a nematic liquid crystal with negative dielectric anisotropy, polarizing plates were placed on both sides of the liquid crystal cell so that birefringent interference colors could be seen, and a liquid crystal display device was created.

In this liquid crystal display device, when a voltage was applied to the transparent electrode, the striped pattern of the birefringent interference color changed smoothly according to the effective value.

<Comparative example> Two glass substrates with a thickness of 3 mm were treated for liquid crystal alignment, and a polyester film with a thickness of 15 μm was sandwiched between one end and gently placed facing each other to form a model liquid crystal cell. The periphery was fixed at several points using epoxy resin adhesive. When the cell thickness was measured by two-wave interferometry, it was found that the cell thickness gradient was irregular, as shown in the graph of FIG.

<Effects of the Invention> According to the structure of the liquid crystal cell of the model of the first invention, internal stress is applied to the transparent substrate and the cell thickness is set by the deflection curve. A model liquid crystal cell can be manufactured with a cell thickness gradient, has little deformation due to external forces, etc., and has stable quality. Therefore, according to the present invention, the liquid crystal cell can be used not only for physical measurements but also for other purposes, and it is now possible to make a display device using a model liquid crystal cell, which has conventionally been considered impractical, by using Mμγ. Become.

Further, according to the manufacturing apparatus of the second aspect of the invention, the pair of transparent substrates can be pressed together to generate internal stress and fixed in a bent state using a simple structure.

[Brief explanation of drawings]

Fig. 1.2 is a sectional view of an embodiment of the horizontal liquid crystal cell of the present invention, Fig. 3 is a view showing a pair of transparent substrates held between clips, and Fig. 4 is a perspective view of the manufacturing apparatus of the invention. Figure 5 is a diagram showing the cell gap of a conventional model liquid crystal cell, Figure 6 is a diagram showing the cell gap of a conventional model liquid crystal cell.
The figure shows the cell gap of the liquid crystal cell of the model of the present invention, Figure 7 shows the cell gap between the horizontal liquid crystal cell of the present invention and the horizontal liquid crystal cell of the cylindrical lens, Figures 8 and 9. are sectional views of conventional liquid crystal cells. 11.12...Transparent substrate, 13...Liquid crystal, 15,1
6. Spacer, 21. 22. Adhesive, 31. Stand, 3
2...Frame, 35...Screw. Patent applicant: Sharp Corporation Agent
Patent Attorney Maeda Ao Soto 28 No. 81! ! Figure 9 1Zim! ＠ De Lua Ya Shifu lPm1 Serpe Rose Tsubu (pm)

Claims (3)

[Claims] (1) In a model liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of transparent substrates, the pair of transparent substrates are bent in a predetermined bending curve due to stress applied in advance, and the pair of transparent substrates are A wedge-shaped liquid crystal cell, characterized in that the thickness of the liquid crystal layer at at least one end is a constant value, and the thickness of the liquid crystal layer inside is fixed to be substantially zero at at least one place. (2) l is the curved surface where the transparent substrate contacts the liquid crystal,
The distance from the tangent plane at the end point of the thin cell thickness to the end point of the thick cell thickness [unit: mm], y is the displacement from the position of the thinnest cell thickness to the position of the thickest cell thickness [unit: μm], t is the distance The wedge-shaped liquid crystal according to claim 1, wherein the thickness of the transparent substrate [unit: mm] is such that the way the transparent substrate is bent satisfies the inequality yt^3/l^3≧0.001. cell. (3) a base, a gate-shaped frame fixed to the base and having an opening into which a pair of transparent substrates are inserted; a presser plate that presses the pair of transparent substrates inserted into the opening; A manufacturing device comprising: a screw member for pressing a presser plate toward a base plate.