JP3347341B2 - Liquid crystal display manufacturing method - 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 for manufacturing a liquid crystal display, and more particularly to an improvement in a method for sealing a substrate.

[0002]

2. Description of the Related Art Generally, there are many types of liquid crystal displays such as a TN type, a DS type, a GH type, an SBE type and a thermal writing type depending on an operation mode. A TN type or SBE type which is a field effect type is used. As an example of a liquid crystal display using such an operation mode, there is a liquid crystal display described in, for example, JP-A-60-107020.

As a configuration of this liquid crystal display, two transparent substrates having transparent electrodes formed on at least one side are opposed to each other, the periphery is sealed to form a cell, and a nematic liquid crystal is injected into the cell. .

In this case, the distance between the opposing substrates is 4 to 12 μm.
m, and cyclohexane-based, ester-based, biphenyl-based, and pyrimidine-based liquid crystals are used as nematic liquid crystals. A chiral agent is added to the nematic liquid crystal so that the molecular axis of the liquid crystal molecules is 180 ° to 360 °.
°, preferably 270 °, between the upper and lower substrates. The liquid crystal molecules have an inclination (pretilt) of more than 5 ° with respect to the plane of the substrate due to the function of the alignment layer on the substrate.

However, such a liquid crystal display is required to have an extremely high gap accuracy between opposed substrates, and is required to have an accuracy of ± 0.1 μm.
Must be kept within. Even a slight change in the gap changes the threshold voltage or the lighting state, or significantly changes the color due to the interference phenomenon, thereby impairing the stability of display quality. One of the important factors for making the thickness of the liquid crystal layer uniform is the sealing step of the liquid crystal cell. Conventionally, in this sealing step, pressure is applied after injecting liquid crystal from an injection port. It took only a few seconds for the pressure to reach the ultimate pressure.

[0006]

As shown in FIG. 5A, a liquid crystal cell is composed of two glass substrates 21 and 22 opposed to each other.
Is sealed with a sealing agent 23. Then, the liquid crystal cell in which the gap is kept constant by pressurizing and heating at the time of sealing is compared with the shrinkage of the glass at the time when the temperature returns to room temperature, and the sealing agent 22 is used.
Has a sufficiently large curing shrinkage ratio, and the stress shrinks inward from the periphery of the liquid crystal cell, so that the central portion of the liquid crystal cell expands as shown in FIG.

In the sealing step, pressurizing the liquid crystal cell has the effect of discharging the liquid crystal and making the thickness of the liquid crystal layer uniform. As a result, as shown in FIG. 6, distortion 24 of the glass of the substrates 21 and 22 is caused, the accuracy of the in-plane variation of the gap is reduced, and the quality of the liquid crystal display is significantly reduced. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a liquid crystal display capable of accurately defining a gap between opposed substrates.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a spacer and a liquid crystal are sandwiched between two opposing substrates having conductive electrodes formed on one principal surface side, and the two substrates are subjected to a pressing force balanced with the stress of the spacer. In the method of manufacturing a liquid crystal display device in which a predetermined gap is obtained by pressurizing, the pressure is increased from the first pressure to the ultimate pressure until the pressure reaches a pressure balanced with the stress of the spacer.
Step-by-step with a temporal change to a second pressure lower than the force
Or the first pressurization, which increases linearly, and the pressure
When the force is reached, the pressure is
And a second pressurization for increasing the pressure from the second pressure to the ultimate pressure .

[0009]

According to the present invention, the liquid crystal cell whose central portion expands due to the stress at the time of curing and shrinking of the adhesive is gradually pressed to reduce the distortion of the substrate in the direction of the shrinking surrounding adhesive. . As a result, variation in the gap is reduced, and the display quality of the liquid crystal display is improved.

[0010]

An embodiment of the present invention will be described below in detail with reference to the drawings.

Taking the case where the liquid crystal display is of the SBE type as an example, the liquid crystal display obtained by one embodiment of the present invention is configured as shown in FIG. 1 and will be described according to the manufacturing process.

First, transparent conductive electrodes 3, 4 made of, for example, ITO (indium tin oxide) are formed on the main surfaces 1a, 2a of the first and second substrates 1, 2, which are, for example, glass substrates, respectively. Orientation layers 5 and 6 made of, for example, polyimide are formed to cover the conductive electrodes 3 and 4, respectively. Next, the first and second substrates 1 and 2 are connected to one main surface 1a,
The periphery is sealed with a sealing agent 7 at predetermined intervals so that the 2a side faces each other. This step is performed in the following procedure. (1) sealing Chakuzai coating step (2) sealant defoaming step (3) S pacer placement step (4) set upright step (5) sealed Chakuzai curing process

The step (1) includes the first and second substrates 1 and 2
A sealing agent 7 including a high-precision glass spacer 8 is formed on one of the principal surfaces 1a and 2a by screen printing or a dispenser into a seal pattern excluding a portion serving as a liquid crystal injection port. In the step (2), the patterned sealing agent 7 is heated at about 90 ° C. for about 1 hour to perform defoaming.

The step (3) includes the first and second substrates 1 and 2
The spacers 8, for example, about 100 to 300 beads / spacer, are uniformly formed on the entire surface of the other main surface 1a, 2a.
mm ² Or about 12-30 pieces / mm of glass fiber
^Two Place at a density of The step (4) includes the first and second steps.
The substrates 1 and 2 are overlaid so that the main surfaces 1a and 2a face each other. The step (5) includes the first and second superimposed steps.
The substrates 1 and 2 are, for example, 300 g / cm ² Heat and harden while applying pressure with force. Next, the first and second substrates 1,
A nematic liquid crystal 9 to which a chiral agent is added is injected from a liquid crystal injection port into a gap surrounded by the sealing agent 7 between the two.

The following steps relate to the present invention.
When the cell into which the liquid crystal 9 is injected is pressurized to discharge the excess liquid crystal, the pressure is increased stepwise, so that the cell is pressurized in a profile as shown in FIG. In the figure, the horizontal axis represents pressurization time, and the vertical axis represents pressure. In the stepwise pressurization, the time required to reach the ultimate pressure is, for example, 1 to 30
Increase pressure so that it is in minutes.

In this case, for example, as shown in FIG. 3, the pressurizing time and the pressurizing force are made infinitely small, and the pressurizing force is increased so as to become substantially linear, or as shown in FIG. A similar effect can be obtained by a method in which the pressure is increased stepwise (or linearly) until a certain point in time until the pressure is reached, and the pressure is increased from a certain point to the ultimate pressure. Thereafter, the liquid crystal injection port is sealed with an ultraviolet curable adhesive.

The molecular axis of the liquid crystal 9 is set between 180 ° and 360 ° between the first and second substrates 1 and 2 by the action of the chiral agent.
It has a twist of, for example, 210 ° in the range of 210 ° and has an inclination of, for example, 3 ° with respect to the plane of the first and second substrates 1, 2.

A polarizing plate 10 is attached to the other main surface 1b of the first substrate 1, and a polarizing plate 11 and a reflector 12 are attached to the other main surface 2b of the second substrate 2, respectively. Here, the arrangement angles of the polarizing plates 10 and 11 are set such that the transmission axes of the polarizing plates 10 and 11 are approximately 50 ° clockwise and approximately 20 ° clockwise with respect to the orientation direction of the first substrate 1, respectively. It has been set. The desired liquid crystal display is thus obtained, which is black when selected and yellow when not selected.

As described above, in this embodiment, when a predetermined gap is obtained by pressing the liquid crystal cell, the spacer 8
By gradually increasing the pressure until the pressure reaches a pressure balanced with the stress of the liquid crystal cell, the distortion of the first and second substrates 1 and 2 can be reduced, and the variation in the gap between the liquid crystal cells can be reduced. .

Actually, the gap between the liquid crystal cells produced according to this embodiment is 7.0 ± 0.1 μm, and the standard deviation σ = 0.
07, indicating that a liquid crystal display having uniform cell gaps with very little variation was obtained.

[0021]

According to the present invention, when a predetermined gap is obtained by pressurizing the liquid crystal cell, the pressure is increased stepwise until the pressure reaches a pressure balanced with the stress of the spacer. A good uniform gap can be obtained, a liquid crystal display with good display quality can be provided, and the industrial effect is great.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a liquid crystal display obtained by a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing a profile of pressurizing time and pressurizing force in a sealing step in a manufacturing method according to one embodiment of the present invention.

FIG. 3 is a characteristic curve diagram showing a profile of a pressurizing time and a pressurizing force in a sealing step in a manufacturing method according to another embodiment of the present invention.

FIG. 4 is a characteristic curve diagram showing a profile of a pressurizing time and a pressing force in a sealing step in a manufacturing method according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view schematically showing a liquid crystal display obtained by a conventional manufacturing method.

FIG. 6 is a cross-sectional view showing a defect of a conventional manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate, 2 ... 2nd board | substrate, 3, 4 ... Conductive electrode, 7 ...
Sealing agent, 8 spacer, 9 liquid crystal, 1a, 2a one main surface.

Continuation of the front page (72) Inventor Eiji Maeda 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Electronic Engineering Co., Ltd.

Claims (1)

(57) [Claims] 1. A spacer and a liquid crystal are sandwiched between two opposing substrates each having a conductive electrode formed on one main surface side, and both substrates are pressed with a pressing force that balances the stress of the spacers to form a predetermined gap. In the method for manufacturing a liquid crystal display to be obtained, the pressure is increased from a first pressure to a second pressure lower than the ultimate pressure until the ultimate pressure balanced with the stress of the spacer is reached.
Gradually or linearly increase with time
The first pressurization and when the pressure reaches the second pressure, pressurization
Force is increased from 2nd pressure to ultimate pressure without temporal change
And a second pressurizing method.