JPS61238025A - Manufacture of liquid crystal glare shielding mirror - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal glare shielding mirror which has good durability and generates no interference fringes even when placed under severe condition of high temperature, etc., for a long period by heating a 1/4 wavelength plate and cooling it before sticking the 1/4 wavelength plate on the substrate surface of a liquid crystal cell. CONSTITUTION:When the liquid crystal glare shielding mirror is manufactured, the 1/4 wavelength plate 2 to be stuck on the substrate surface of the liquid crystal cell 1 is left in a thermostatic chamber of 40-120 deg.C for 1-9min until its heat shrinkage is saturated, and then taken out and left as it is for cooling to the room temperature. This treated 1/4 wavelength plate 2 is stuck on the substrate surface of the liquid crystal cell 1 and the mirror surface 31 of a reflecting mirror substrate 3 having the mirror surface 31 formed by vapor-depositing Al, etc., on the surface of the glass substrate 30 with said sticking surface in is superposed upon the cell 1 with an adhesive 5 between. For example, three laminates obtained as mentioned above are set in a die 9 for assembly across rubber elastic plate bodies 7 and applied with a load to set the adhesive. Thus, the glare shielding mirror is obtained which generates no interference fringes owring to variation in the gap between the 1/4 wavelength plate 2 and a reflecting plate 3 due to variation in ambient temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for manufacturing a liquid crystal anti-glare mirror, and more particularly, to an improvement in a quarter-wave plate attached to the surface of a liquid crystal cell.

The liquid crystal anti-glare mirror manufactured by the method of the present invention effectively prevents the occurrence of interference fringes, has good durability, and is useful as a vehicle-mounted rearview mirror.

[Prior Art] In recent years, development of a liquid crystal anti-glare mirror in which a liquid crystal cell and a quarter-wave plate are arranged on the front side (meaning the side near the light source) of the mirror surface of a reflecting mirror has been progressing.

This is achieved by combining a liquid crystal cell and a quarter-wave plate to function as a variable light transmittance member, and by using the variable light transmittance member, a liquid crystal cell and a quarter-wave plate are combined. ) It changes the light reflectance of lI.

Note that the light transmittance is controlled by controlling the electric field applied to the liquid crystal layer.

Conventionally, such liquid crystal anti-glare performance has been achieved by pasting a quarter-wave plate on the surface of a liquid crystal cell manufactured by a known method (for example, the method disclosed in JP-A-57-171318), and attaching this to a reflective mirror substrate. It is manufactured by stacking the two on top of each other and curing the adhesive attached to the periphery of the two, fixing the two.

However, liquid crystal anti-glare sheets manufactured by conventional methods tend to generate interference fringes when exposed to harsh conditions such as high temperatures for a long time, and have the drawbacks of lacking durability.

FIG. 4 is a diagram illustrating the reason why interference fringes occur and durability deteriorates in a liquid crystal anti-glare screen manufactured by a conventional method.

That is, conventionally, as shown in FIG. 4(A), the liquid crystal cell 1 to which the quarter-wave plate 2 is attached and the reflector substrate 3 are stacked without any "warpage", and these are bonded together using an adhesive 5. It's stuck in place.

Therefore, if exposed to low temperature after manufacturing, 1/
The four-wavelength plate 2 contracts, the liquid crystal cell 1 warps as shown in FIG. 4(B), and the distance between the liquid crystal cell 1 and the reflecting mirror substrate 3 widens at the center.

On the other hand, when exposed to high temperature conditions, the quarter-wave plate 2 expands as shown in FIG. 4(C), and the distance between the liquid crystal cell 1 and the reflective mirror substrate 3 widens in the peripheral portion.

As described above, the distance between the center portion and the peripheral portion changes greatly between low-temperature and high-temperature conditions, which tends to cause interference fringes, and also causes unreasonable stress to be applied to the adhesive 5, resulting in degraded durability. It is considered that

[Problems to be Solved by the Invention] The present invention has been devised to eliminate the above-mentioned drawbacks, and it is an object of the present invention to produce a liquid crystal anti-glare screen that prevents the occurrence of interference fringes and has good durability. This provides a method to do so.

[Means and effects for solving the problems] The present invention provides that, prior to attaching a quarter-wave plate to a liquid crystal cell,
It heats and cools the wave plate.

That is, the present invention attaches a 1/4 wavelength plate to the substrate surface of a liquid crystal cell, and
The liquid crystal cell and the reflector substrate are overlapped with the surface to which the 4-wavelength plate is attached on the inside, and a load is applied to the liquid crystal cell and the reflector substrate. In the manufacturing method of a liquid crystal anti-glare film, which is cured to integrally fix the liquid crystal cell and the reflective mirror substrate, the 1/4-wave plate is cured and the 1/4-wave plate is fixed to the surface of the liquid crystal cell. This is a method for manufacturing a liquid crystal anti-glare screen, characterized in that a wave plate is heated and then cooled.

As the liquid crystal cell, a known guest-host type (GH type) liquid crystal cell manufactured by a known method can be used.

The liquid crystal cell functions as a variable light transmittance member when combined with a 174 wavelength plate.

Here, the 1/4 wavelength plate has a function of changing the phase of incident light by 1/4 wavelength. A known one can also be used as a quarter wavelength plate.

Prior to pasting the quarter-wave plate on the liquid crystal cell,
The quarter-wave plate is heated to a predetermined temperature for a predetermined period of time, and then cooled to thermally shrink the 174-wave plate. Here, the predetermined time, the predetermined temperature, and the cooling may be performed at values and methods sufficient to saturate the thermal contraction rate of the quarter-wave plate.

Note that FIG. 3 shows an example of the relationship between the heating temperature and the heating time required to saturate the thermal shrinkage rate.

After pasting the 1/4 wavelength plate prepared in this way on the surface of the liquid crystal cell, the liquid crystal cell is overlapped with the reflector substrate, and while applying a load, the adhesive attached to the predetermined portion is cured, and both to fix.

Here, the predetermined portion refers to a portion that does not contribute to the projection of a reflected image, such as the peripheral portion of a liquid crystal cell. Note that a known reflective mirror substrate having a mirror surface formed by a known method such as a vacuum film forming method can be used as the reflective mirror substrate.

[Examples] Hereinafter, the present invention will be explained in detail based on specific examples.

(Manufacture of liquid crystal anti-glare mirror) The liquid crystal anti-glare mirror of the present invention was manufactured by the following procedure, and the applied load was reduced to 0.
9 types, varying in 20kg intervals between ~160kg,
A total of 243 pieces, 27 pieces of each type, were produced.

FIG. 1 is an explanatory diagram of the manufacturing process.

(1) Manufacture of liquid crystal cell 1 A homogeneous array guest-host (GH) type liquid crystal cell 1 was manufactured by a conventionally known method.

Glass (200 mm x 50 mm) was used as the transparent substrate, nematic liquid crystal was used as the liquid crystal, and anthraquinone dye was used as the dye. Furthermore, a transparent electrode was formed on the entire inner end surface of both transparent substrates by a vacuum film forming method, and an alignment film was formed thereon by a printing method.

(2) Heat treatment and cooling of 1/4 wavelength plate 2
(Thickness: 200 μm, two wavelengths: about 550 nm) was left in a constant temperature bath at 100° C. for 1 hour, then taken out from the constant temperature bath, left indoors for 1 hour, and cooled to room temperature. Through such heat treatment and cooling treatment, the quarter-wave plate was sufficiently thermally shrunk.

(3) Attaching the 1/4 wavelength plate 2: The 1/4 wavelength plate 2 was attached to the surface of each liquid crystal cell 1 using an adhesive. The size of the quarter-wave plate 2 is 194 mm x 44 mm, which is 3 mm inside each side of the liquid crystal cell 1.

(4) Formation of mirror surface 31 Glass substrates 30 (200 mm x 50
A mirror substrate 3 was formed by forming a mirror surface 31 made of an aluminum film on one surface of the mirror substrate 3 mm) by a vacuum film forming method.

(5) Load application Each of the liquid crystal cells 1 and the reflective mirror substrate 3 is
The wavelength plate and the mirror surface 31 are placed on top of each other, and three sets are arranged in series, and assembling is carried out by setting them in the mold 9 via the rubber elastic plate member 7, as shown in FIG. A load was applied.

The size of the applied load is 20kQ in the range of 0 to 160kg.
Twenty-seven samples each with different intervals and the same applied load were manufactured.

(6) Fixation While applying the load, apply an epoxy adhesive 5 with a viscosity of 450 voids to the outer periphery of the liquid crystal cell and reflector substrate, and leave it at room temperature for 14 hours to harden. was fixed.

(Evaluation) For each liquid crystal anti-glare mirror manufactured as described above, the number of interference fringes was measured immediately after manufacture and in a high temperature storage test (85℃
; 1000 hours) were evaluated.

No interference fringes were observed in any of the liquid crystal anti-glare mirrors immediately after manufacture.

The number of interference fringes generated after the high temperature storage test is shown in FIG. In addition, in FIG. 2, the conventional product is one in which heating and cooling of the quarter-wave plate was not performed in the manufacturing process of the above example, and the other processes were the same as in the example. say.

As can be seen from FIG. 5, according to the method of this embodiment, even if the applied load is about 100 kQ, which is thicker than before,
No interference fringes occur.

Even after the high-temperature storage test, the reason why interference fringes are difficult to occur as described above is that the above-mentioned heat treatment and cooling treatment of the quarter-wave plate causes the quarter-wave plate to heat-shrink to a saturated state. This is thought to be because there was almost no thermal contraction even after the above-mentioned high temperature storage test, and therefore the distance between the liquid crystal cell and the reflective mirror substrate hardly changed. Further, for the same reason, almost no undue stress is applied to the adhesive 5 that fixes the liquid crystal cell and the reflecting mirror substrate, and therefore the durability is good.

[Effects of the Invention] To summarize, in the present invention, prior to bonding the quarter-wave plate to a liquid crystal cell, the quarter-wave plate is heated and then cooled to thermally shrink to a saturated state.

As is clear from the examples described, in the present invention, a quarter-wave plate is heated and cooled to heat-shrink it to a saturated state, and then attached to a liquid crystal cell, and an anti-tJJ
It is fixed to the mirror board. Therefore, even if the temperature conditions around the liquid crystal anti-glare mirror change after manufacturing, the quarter-wave plate hardly shrinks due to heat. Therefore, the distance between the liquid crystal cell and the reflecting mirror substrate does not change much. Therefore, the occurrence of interference fringes is prevented, and the durability is also good.

Therefore, it is most suitable as a rearview mirror of a car.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing how to assemble the liquid crystal anti-glare mirror by using a mold and apply a load. FIG. 2 is a graph showing the number of interference fringes generated after a high temperature storage test of the liquid crystal anti-glare mirror manufactured by the method of this example and the liquid crystal anti-glare mirror manufactured by the conventional method. FIG. 3 is a graph showing the relationship between heating time and thermal shrinkage rate of a quarter-wave plate. FIG. 4 is a diagram illustrating the mechanism by which interference fringes occur in a liquid crystal anti-glare mirror manufactured by a conventional method. 1...Liquid crystal cell 2...1/4 wavelength plate 3.
...Reflector board 9...Assembly is done by the application patent applicant Toyota Motor Corporation representative patent attorney
Mamoki Okawa Patent attorney Shudo Fujitani Patent attorney Akio Maruyama Figure 2 Death of Emperor (kg) Time (/fr-) Figure 4

Claims (4)

[Claims] (1) A quarter-wave plate is attached to the surface of the substrate of a liquid crystal cell, and a load is applied by overlapping the liquid crystal cell and a reflective mirror substrate with the surface attached with the quarter-wave plate on the inside, In the method for manufacturing a liquid crystal anti-glare mirror, the liquid crystal cell and the reflective mirror substrate are integrally fixed by curing an adhesive interposed at a predetermined portion between the liquid crystal cell and the reflective mirror substrate, A method for manufacturing a liquid crystal anti-glare mirror, characterized in that, prior to pasting the quarter-wave plate on the surface of the liquid crystal cell, the quarter-wave plate is heated and then cooled. (2) The heating temperature of the quarter wavelength plate is 40°C to 120°C.
The manufacturing method according to claim 1, wherein the temperature is .degree. (3) The method for manufacturing a liquid crystal anti-glare mirror according to claim 1, wherein the heating of the quarter-wave plate is performed in a constant temperature bath. (4) The method for manufacturing a liquid crystal anti-glare mirror according to claim 1, wherein the heating time of the quarter wavelength plate is 1 minute to 90 minutes.