JP3142371B2 - Method and apparatus for manufacturing plastic liquid crystal display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a plastic liquid crystal display device in which a liquid crystal is sandwiched between two flexible plastic film substrates having transparent electrodes.

[0002]

2. Description of the Related Art As a substrate for a liquid crystal display device, a glass substrate is generally used and has been used up to the present day. On the other hand, recently, a plastic liquid crystal display device using a flexible plastic film substrate as a substrate is being developed. Since this liquid crystal display element has excellent features such as flexibility, light weight and thinness, and excellent safety, it is highly expected to be put to practical use. As a method of manufacturing such a plastic liquid crystal display device, a method of manufacturing a device by applying a liquid crystal to a long plastic film has been proposed in order to reduce the manufacturing cost. Such a manufacturing method is disclosed in, for example, Japanese Patent Application Laid-Open No. 54-126.
No. 559 and Japanese Patent Application Laid-Open No. Sho 62-150218.

[0003]

However, in the conventional manufacturing method, the liquid crystal solution is simply supplied from the liquid crystal solution tank to the flexible plastic film surface by the supply device and applied. The control of the liquid crystal film thickness is not performed. By the way, the concentration of the liquid crystal solution in the solution tank adjusted before the start of coating increases because the solvent evaporates over time, and as a result, the liquid crystal coating film tends to be thick. Therefore, if the film thickness of the liquid crystal coating film is not monitored, when the concentration and viscosity conditions of the liquid crystal to be supplied change, the film thickness changes significantly from the initial value, leading to a decrease in yield. Become like Here, in controlling the film thickness of the liquid crystal coating film, a method may be considered in which the operating conditions of the liquid crystal supply device system are changed, but such a control method complicates the control system and allows simple control. There is a problem that there is no.

The present invention has been proposed in order to solve the problems of the prior art, and can easily control the thickness of a liquid crystal applied to a flexible plastic film substrate surface. An object of the present invention is to provide a manufacturing method and a manufacturing apparatus for manufacturing a highly accurate liquid crystal display element having a uniform liquid crystal film thickness that can be performed.

[0005]

In order to achieve this object, the present invention provides a liquid crystal display device comprising a liquid crystal sandwiched between two flexible plastic film substrates having a transparent electrode. Immediately after the liquid crystal solution is applied to the electrode surface of one of the plastic film substrates, the thickness of the liquid crystal coating film is measured, and the concentration or viscosity of the liquid crystal solution is determined based on the measured value of the film thickness. It is a method of adjusting the value to an optimum value and controlling so that a uniform liquid crystal coating film having a desired film thickness is applied and formed on the plastic film substrate. Preferably, the liquid crystal in the liquid crystal solution applied to the plastic film substrate is a ferroelectric liquid crystal composition, and more preferably, a ferroelectric polymer liquid crystal composition.

Further, the apparatus for manufacturing a liquid crystal display element according to the present invention comprises a film thickness measuring means for measuring the film thickness of the liquid crystal coating film immediately after the liquid crystal solution is applied to the electrode surface of one plastic film substrate; The concentration or viscosity of the liquid crystal solution is adjusted to an optimum value based on the film thickness measurement value from the film thickness measurement means so that a uniform liquid crystal coating film having a desired film thickness is formed on the plastic film substrate. And a control unit for controlling.

Further, the apparatus for manufacturing a plastic liquid crystal display element according to the present invention is, specifically, a liquid crystal solution tank containing a liquid crystal solution for forming a liquid crystal coating film, and a liquid crystal solution supplied from the liquid crystal solution tank. Immediately after being applied to the electrode surface of one of the plastic film substrates, the liquid crystal is supplied from the liquid crystal tank based on a control signal, connected to the liquid crystal solution tank and a film thickness measuring means for measuring the thickness of the liquid crystal coating film. A liquid crystal solution replenishment tank to which a solvent is supplied from a solvent tank, a sensor for measuring the concentration or viscosity of the liquid crystal solution in the liquid crystal solution replenishment tank, and a film thickness measurement value from the film thickness measurement means. A concentration or viscosity measurement value from a sensor is input, and the concentration or viscosity of the liquid crystal solution in the liquid crystal solution supply tank is adjusted to an optimum value based on the film thickness measurement value. Uni The liquid crystal tank or outputs a control signal to said solvent tank, a desired film thickness uniform liquid crystal coating film having the a configuration equipped with a control unit for controlling so as to be applied and formed on the plastic film substrate.

Here, the liquid crystal display device manufactured according to the present invention has a structure in which a liquid crystal is sandwiched between two flexible plastic film substrates with transparent electrodes.

In the above liquid crystal display device, the plastic film substrate may be, for example, a crystalline polymer such as uniaxially or biaxially stretched polyethylene terephthalate, an amorphous polymer such as polysulfone or polyether sulfone, a polyolefin such as polyethylene or polypropylene, or a polycarbonate. And polyamides such as nylon. By using such a flexible substrate, the display surface of the liquid crystal display element can be curved, and a liquid crystal display element having a large area and capable of displaying a curved surface can be obtained.

As the electrodes formed on the substrate, those commonly used in liquid crystal display elements can be used, and transparent or translucent electrodes can be used.
For example, a film made of a NESA film or an ITO film may be used. The electrode pattern may be a stripe for dot matrix display or a pattern for segment display according to the required display content. Alternatively, these patterns may be mixed.

As the liquid crystal material, various liquid crystals can be used as long as they do not react with the plastic substrate. From the viewpoint of flexibility and the like, ferroelectric liquid crystals are preferably used. It is preferable to use a ferroelectric polymer liquid crystal which exhibits excellent characteristics such as large screen properties and memory properties when combined with a substrate. Here, the ferroelectric low-molecular liquid crystal includes, for example, one or more ferroelectric low-molecular liquid crystals, and a mixture of one or more ferroelectric low-molecular liquid crystals and other low-molecular liquid crystals. Ferroelectric low-molecular liquid crystals can be used. Also,
The ferroelectric polymer liquid crystal includes, for example, one or more ferroelectric polymer liquid crystals, one or more ferroelectric low-molecular liquid crystals, and one or more ferroelectric polymer liquid crystals. Ferroelectric polymer liquid crystals, ferroelectric polymer liquid crystals composed of one or more ferroelectric low-molecular liquid crystals and one or more other polymer liquid crystals, and the like can be given. That is, as the ferroelectric polymer liquid crystal, a polymer molecule itself exhibits a ferroelectric liquid crystal characteristic (homopolymer or copolymer, or a mixture thereof), a ferroelectric polymer liquid crystal and another A mixture of a polymer liquid crystal and / or a normal polymer, a mixture of a ferroelectric polymer liquid crystal and a ferroelectric low-molecular liquid crystal, a ferroelectric polymer liquid crystal and a ferroelectric low-molecular liquid crystal and a polymer liquid crystal, and / or A polymer liquid crystal exhibiting all ferroelectric properties, such as a mixture with an ordinary polymer or a mixture of these with an ordinary low-molecular liquid crystal, can be used.

Among the ferroelectric polymer liquid crystals, for example, a side chain type ferroelectric polymer liquid crystal having a chiral smectic C phase can be suitably used. The ferroelectric liquid crystal composition may contain an adhesive, a viscosity reducing agent, a non-liquid crystal chiral compound,
Dyes and the like are included. The thickness of the liquid crystal layer is not particularly limited, but is preferably 1 to 10 μm, and particularly preferably 1.5 to 10 μm.
The thickness is preferably 3 μm.

As a method of applying a liquid crystal material,
A method of dissolving a liquid crystal material with a solvent to enhance the fluidity and applying the liquid to a uniform film thickness on the electrode side surface of the flexible substrate with electrodes by a microgravure method, a direct gravure method, or the like is suitable. As the solvent, a general aromatic, aliphatic or alcoholic solvent can be used. Also,
As another coating method, an impregnation coating method in which a liquid crystal material having improved fluidity is included in an impregnating member, and the impregnating member is moved while being pressed against the electrode side surface of the flexible substrate with electrodes to apply the liquid material is also used. Can be. This coating method is disclosed in
No. 10322.

[0014]

According to the above-described method and apparatus for manufacturing a liquid crystal display element, the thickness of a liquid crystal coating film formed by applying a liquid crystal solution to a plastic film substrate surface is measured. Since the concentration or viscosity of the liquid crystal solution is adjusted to an optimum value, the thickness of the liquid crystal coating film applied to the plastic film substrate surface can be changed without changing the operating conditions of the liquid crystal solution supply system. , Can be controlled to a desired uniform thickness.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a method and an apparatus for manufacturing a liquid crystal display device according to the present invention will be described below in detail with reference to the drawings. In the manufacturing method of the liquid crystal display element according to the embodiment,
The liquid crystal solution in the solution tank is applied to the surface of the flexible plastic film substrate by a supply device including an application roll or the like, and the liquid crystal film thickness immediately after application is measured by a film thickness monitor. Here, the liquid crystal coating film to be measured is in a wet (wet) state containing a solvent, but the thickness of only the liquid crystal after drying is measured in advance, and the correspondence with the liquid crystal film thickness immediately after application is measured. By setting aside, the film thickness can be controlled. The liquid crystal film thickness after drying can be measured using a transmission electron microscope or the like. The measurement information from the film thickness monitor is sent to a supply tank connected to the solution tank, and adjusted so that the concentration or viscosity of the liquid crystal solution in the solution tank becomes an optimum value. Thereby, the thickness of the liquid crystal coating film applied to the surface of the plastic film substrate is controlled so as to be always uniform.

Next, the configuration of a manufacturing apparatus for manufacturing a liquid crystal display element by such a manufacturing method will be described with reference to FIG. A flexible and long plastic film substrate 1 having a transparent electrode for display adhered to a surface to be a liquid crystal application surface, a transport roll 2 with the liquid crystal application surface facing downward.
Is sent to the coating step 3. A solution tank 5 containing a liquid crystal solution 4 is provided in the coating section 3, and a coating roll 6 immersed in the solution tank 5 is in contact with the plastic substrate surface 1a in the width direction. When the plastic film substrate 1 is fed in the direction of arrow P by the transport roll 2, the application roll 6 also rotates,
The liquid crystal solution 4 is applied to the electrode side surface of the film substrate 1 by the application roll 6. The thickness of the liquid crystal coating film 7 applied to the plastic film substrate surface 1a is measured immediately after the application by a thickness monitor 8 provided on the liquid crystal application surface side. In this film thickness monitor 8 serving as a film thickness measuring means, β-ray,
The coating film 7 is irradiated with γ-rays or infrared rays, and the film thickness is measured by using the absorbance of these irradiation rays in the coating film 7. Film thickness measurement data D1 of the coating film 7 by the film thickness monitor 8
Is sent to the control computer 9 forming a control unit.

The liquid crystal solution tank 5 has a liquid crystal solution supply tank 1
0 are connected by a conduit 11. Liquid crystal is supplied from the liquid crystal tank 12 via the pipe 14 in response to the control signal S1 from the control computer 9, and the solvent tank 13 which receives the control signal S2.
Is supplied through line 15 from the solvent. Supply tank 1
The inside of 0 is stirred by the stirrer 16 to make the concentration uniform. The concentration or viscosity of the liquid crystal solution 4 in the supply tank 10 is measured by a sensor 17.
Is transmitted to the control computer 9.
The plastic film substrate 1 on which the liquid crystal has been applied is sent from the application section 3 to the next drying section 18 where it is dried, and then continuously sent to the lamination section. In this laminating step, another plastic film substrate is attached to the surface of the plastic film substrate on which the liquid crystal layer 7A has been formed, and then cut into an appropriate size.

Next, the operation of the manufacturing apparatus configured as described above will be described. The control computer 9 which receives the measurement data D1 from the film thickness monitor 8 compares the measurement data D1 of the film thickness with an appropriate film thickness value of the coating film stored in advance and compares the comparison result. Based on the liquid crystal tank 1
2 or the control signal S1, S2 to the solvent tank 13, respectively.
Is sent. On the other hand, the concentration or viscosity of the liquid crystal solution 4 in the replenishing tank 10 is measured by the sensor 17, and the measurement data D2 is sequentially sent to the control computer 9,
By controlling the liquid crystal supply amount or the solvent supply amount to the replenishing tank 10 based on the control signals S1 and S2, the liquid crystal solution 4 in the replenishing tank 10 has an appropriate film thickness of the coating film 7 on the plastic film substrate surface 1a. It is adjusted in the direction of the value. For example, when it is determined that the thickness of the coating film 7 is larger than an appropriate value based on the measurement data D1 of the film thickness, the supply amount of the solvent to the supply tank 10 increases, and the liquid crystal solution 4 in the supply tank 10 Is adjusted in such a manner that the concentration or viscosity of On the other hand, when it is determined that the thickness of the coating film 7 is smaller than the appropriate value based on the thickness measurement data D1, the supply amount of the liquid crystal to the replenishing tank 10 increases, and the liquid crystal solution 4 Is adjusted in such a way that the concentration or viscosity becomes higher. Since the liquid crystal solution 4 in the replenishing tank 10 is sent to the solution tank 5 through the conduit 11, the concentration of the liquid crystal solution 4 in the solution tank 5 is set to an optimum value, and the liquid crystal on the plastic film substrate surface 1a is set. Is controlled with high accuracy so that the coating film 7 always has a uniform film thickness.

Experimental Example When liquid crystal was applied using the manufacturing apparatus shown in FIG. 1, the thickness of the liquid crystal layer 7A after drying was 2 μm ± 0.2 μm.
Was controlled with the accuracy of.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist.

[0021]

As described above, according to the present invention, when a liquid crystal solution is applied to the surface of a plastic film substrate to form a liquid crystal coating film, the thickness of the coating film is measured and based on the measured data. Since the concentration or viscosity of the liquid crystal solution is controlled, a liquid crystal coating film having a uniform thickness can always be formed on the plastic film substrate. According to such a method, there is an advantage that the film thickness can be controlled using much simpler control means than when the film thickness is controlled by changing the operating conditions of the liquid crystal supply system. As a result, the yield can be improved and the cost of the plastic film liquid crystal display device can be reduced. Further, a liquid crystal display element having a liquid crystal layer having a uniform thickness with high accuracy can be provided, so that high-quality display can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a device for manufacturing a liquid crystal display element according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 plastic film substrate 1a plastic film substrate surface 2 transport roll 3 coating process section 4 liquid crystal solution 5 liquid crystal solution tank 6 coating roll 7 coating film 7A liquid crystal layer 8 film thickness monitor 9 control computer 10 liquid crystal solution supply tank 11, 14, 15 Pipe 12 Liquid crystal tank 13 Solvent tank 16 Stirrer 17 Sensor for measuring concentration or viscosity 18 Drying process section

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/13 101

Claims (5)

(57) [Claims] 1. A manufacturing method for manufacturing a plastic liquid crystal display device in which a liquid crystal is sandwiched between two flexible plastic film substrates having a transparent electrode. Immediately after the application of the liquid crystal solution, the thickness of the liquid crystal coating film is measured, and the concentration or viscosity of the liquid crystal solution is adjusted to an optimum value based on the measured value of the film thickness. A method for manufacturing a plastic liquid crystal display device, comprising controlling a liquid crystal coating film to be applied to the plastic film substrate. 2. The method according to claim 1, wherein the liquid crystal in the liquid crystal solution applied to the plastic film substrate comprises a ferroelectric liquid crystal composition. 3. The method according to claim 1, wherein the liquid crystal in the liquid crystal solution applied to the plastic film substrate comprises a ferroelectric polymer liquid crystal composition. 4. A manufacturing apparatus for manufacturing a liquid crystal display device in which a liquid crystal is sandwiched between two flexible plastic film substrates having a transparent electrode, wherein a liquid crystal is provided on one electrode surface of one of the plastic film substrates. Immediately after the application of the solution, the concentration or viscosity of the liquid crystal solution is adjusted to an optimum value based on the film thickness measurement means for measuring the film thickness of the liquid crystal coating film and the film thickness measurement value from the film thickness measurement means. A control unit for controlling a uniform liquid crystal coating film having a desired film thickness to be applied to the plastic film substrate. 5. A manufacturing apparatus for manufacturing a liquid crystal display device comprising a liquid crystal sandwiched between two flexible plastic film substrates with transparent electrodes, wherein a liquid crystal solution for forming a liquid crystal coating film is filled. A liquid crystal solution tank provided, and a film thickness measuring means for measuring the film thickness of the liquid crystal coating film immediately after the liquid crystal solution supplied from the liquid crystal solution tank is applied to the electrode surface of one of the plastic film substrates; A liquid crystal solution supply tank connected to the liquid crystal solution tank and supplied with liquid crystal from the liquid crystal tank based on the control signal and supplied with a solvent from the solvent tank; and A sensor to be measured, a film thickness measurement value from the film thickness measurement means, and a concentration or viscosity measurement value from the sensor are input, and the liquid crystal is measured based on the film thickness measurement value. A control signal is output to the liquid crystal tank or the solvent tank so that the concentration or viscosity of the liquid crystal solution in the liquid supply tank is adjusted to an optimum value, and a uniform liquid crystal coating having a desired film thickness is formed on the plastic film substrate. And a control unit for controlling the liquid crystal display element to be formed on the plastic liquid crystal display element.