KR100629687B1 - Fabricating method for liquid crystal display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device, which is applied to opposite surfaces of an upper substrate and a lower substrate to enhance the alignment energy of the surface of the alignment layer and the liquid crystal molecules undergoing an alignment process, and the initial alignment of liquid crystal molecules As a means for fixing the state, a thermosetting polymer is added to the liquid crystal, cured so as to be parallel to the alignment direction of the liquid crystal molecules, and the liquid crystal molecules are fixed, thereby enhancing the alignment control force between the liquid crystal molecules and the alignment layer, A stable alignment state can be obtained.

Description

Manufacturing method for liquid crystal display device             

1 is a cross-sectional view showing a cross section of a general liquid crystal display device;

2A to 2D are process cross-sectional views briefly illustrating a conventional method for manufacturing a liquid crystal display device;

3A to 3D are cross-sectional views illustrating a method of manufacturing a liquid crystal display device according to the present invention.

<Description of the symbols for the main parts of the drawings>

115: alignment layer 117: upper substrate

119: lower substrate 121a: thermosetting polymer additive

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal cell included in the liquid crystal display device.

In general, a liquid crystal display includes an upper substrate on which a common electrode and a color filter are formed, a lower substrate on which a switching element and a pixel electrode are formed, and a liquid crystal filled between the upper substrate and the lower substrate. There are many kinds of liquid crystals, and among them, a kind used in manufacturing a liquid crystal display device is a twisted nematic liquid crystal (TN), a super twisted nematic liquid crystal (STN), and a ferroelectric A large number of liquid crystals (ferroelectric liquid crystals (FLC) and cholesteric liquid crystals).

Each of the plurality of liquid crystals has an initial arrangement characteristic, and when voltage is applied, the liquid crystal has an optical anisotropy characteristic that transmits or blocks light by adjusting horizontally or vertically, or adjusts the amount of light.

A configuration of a general liquid crystal display including the liquid crystal described above will be described with reference to FIG. 1.

1 is a cross-sectional view showing a cross section of a general liquid crystal display device.

As illustrated, the liquid crystal display 11 generally includes a color filter 7 including a black matrix 6 and an upper substrate 5 having a transparent common electrode 18 formed on the color filter 7. The lower substrate 21 is spaced apart from the upper substrate by a predetermined distance.

The lower substrate 21 is an array substrate and includes a pixel region (not shown), a pixel electrode (not shown) and a switching element (not shown) formed on the pixel region.

Finally, an alignment layer 23 is formed on the surfaces of the upper substrate 5 and the lower substrate 21 that face each other.

The upper substrate 5 and the lower substrate 21 are bonded by an adhesive 35, and the upper and lower polarizers 25 and 27 are attached to upper and lower portions of the bonded liquid crystal panel, respectively. The display device 11 is completed.

The liquid crystal display 11 is an apparatus in which an image is represented by transmitting or absorbing light of the backlight 31 or adjusting the amount of light by the arrangement characteristic of the liquid crystal molecules 33 having the optical anisotropy.

Therefore, the alignment characteristics of the liquid crystal molecules 33 have a great influence on the optical characteristics of the liquid crystal display device 11. Therefore, controlling the alignment characteristics of the liquid crystal molecules 33 is a very important problem, especially between the alignment film 23 and the liquid crystal molecules 33 which have the greatest influence on the alignment characteristics of the liquid crystal molecules 33. Maintaining the anchoring energy of is a very important factor.

The orientation control force refers to the energy generated between the substrate and the alignment layer, which refers to a state larger than the energy due to the applied voltage.

Accordingly, the liquid crystal molecules in contact with the alignment layer even when a voltage is applied have a property of not being polarized by the alignment control force.

Therefore, if the alignment control force is not large enough, the initial alignment state of the liquid crystal is disturbed. The optical characteristics of the liquid crystal display are not good.

In this case, the alignment layer may be formed on opposite surfaces of the upper substrate and the lower substrate, respectively, and the initial alignment state of the liquid crystal molecules may be fixed by the alignment layer.

In detail, the physical properties of the liquid crystal are changed by the molecular arrangement state, and there is a difference in response to external forces such as an electric field. The arrangement control of the liquid crystal molecules is an essential technique not only for the study of liquid crystal properties but also for the configuration of the liquid crystal display device. The relative positional relationship between the elongated liquid crystal molecules and the substrate can be expressed by the angle of elevation on the surface of the substrate and the orientation of the projection on the surface of the substrate. The formation of the alignment film is important because it is closely related to the stability of the film.

The alignment layer may be formed of an inorganic alignment layer, an organic alignment layer, and the like.

For example, the inorganic alignment film is formed by a silicon oxide film (SiO) oblique deposition method. The silicon oxide film (SiO) evaporation method deposits an inorganic material such as a metal, an oxide, and a fluoride at an angle to a substrate, and a silicon oxide film is generally used as a deposition material.

If the deposition conditions such as deposition angle, deposition rate, vacuum degree, substrate temperature, and film thickness, and the deposition material and the liquid crystal material are different, the liquid crystal molecular orientation forms also change.

In order to obtain parallel alignment, a transparent electrode is formed on the substrate, and the surface of the substrate is mechanically rubbed using diamond paste or the like.

The film's orientation mechanism is thought to be due to a fine groove in the rubbing direction and the pretilt angle is almost 0 degrees.

2a to 2d is a general optical alignment film It is a process chart which shows the formation process.

First, as shown in FIG. 2A, an alignment film 43 is formed by first applying a polymer such as an optical alignment film to the substrate 41.

Next, as shown in FIG. 2B, light (UV) 45 is irradiated onto the coated alignment layer 43 to align the alignment layer 43.

Then, as shown in FIG. 2C, the cross section of the alignment layer 43 has a predetermined pretilt angle 47.

In this case, the alignment layer is formed on opposite surfaces of the upper substrate and the lower substrate, respectively.

Next, the upper substrate 51 and the lower substrate 41 on which the alignment layer 43 is formed are bonded to each other, and the liquid crystal 53 is injected between the two substrates.

In this case, the liquid crystal molecules 53 are positioned depending on the pretilt angle of the alignment layer 43.

However, in the case of the alignment film oriented using light as described above, the afterimage characteristic is severe due to problems of low alignment control force and residual DC of the alignment film material.

Therefore, in order to improve such afterimage characteristics, it is necessary to lower the residual DC characteristic applied to the alignment layer 43 and to strengthen the surface regulating force on the liquid crystal molecules of the alignment layer.

Accordingly, an object of the present invention is to fabricate a liquid crystal display device in which afterimages are removed by improving the alignment energy of the liquid crystal molecules.

According to an aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, the method including: forming first and second alignment layers on upper portions of a first substrate and a second substrate; Aligning the first or second alignment layer; Bonding the first substrate and the second substrate to each other such that the first and second alignment layers face each other and have a predetermined gap; Injecting a mixed liquid crystal containing a thermosetting polymer into a gap between the first substrate and the second substrate to form and age a mixed liquid crystal layer; And heat treating the thermosetting polymer in the mixed liquid crystal layer to form a network phase by heat treatment, wherein the liquid crystal is rotated according to an applied electric field in the polymer network phase.
The alignment treatment may include photoaligning the first or second alignment layer by irradiating ultraviolet rays with the first or second alignment layer.

In addition, the thermosetting polymer in the mixed liquid crystal layer has a nematic property, the liquid crystal is a nematic liquid crystal, the network phase is characterized in that it is cured after being anisotropically aligned along the alignment direction of the first or second alignment layer.

According to an aspect of the present invention, there is provided a liquid crystal display including: first and second substrates having at least one optical alignment layer formed thereon; And a mixed liquid crystal layer comprising a thermosetting polymer and a liquid crystal molecule formed between the first substrate and the second substrate to form a network.

In this case, the network phase is formed by being aligned and cured along the initial alignment state of the optical alignment layer by a thermosetting polymer material, the liquid crystal molecules are formed by being constrained by the network, the liquid crystal molecules are rotated according to the application of an electric field It is characteristic.
The thermosetting polymer in the mixed liquid crystal layer has a nematic property, the liquid crystal is a nematic liquid crystal, and the network phase is cured after being anisotropically aligned along the alignment direction of the first or second alignment layer. .

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

In the present invention, a predetermined additive is added to the liquid crystal in order to improve the alignment control force between the aforementioned alignment film and the liquid crystal molecules. Hereinafter, a description will be given with reference to FIGS. 3A to 3C.

3A to 3C are cross-sectional views illustrating a process of manufacturing a liquid crystal cell included in a liquid crystal display according to the present invention.

As shown in the drawing, an alignment layer 115 that is optically aligned to have a predetermined alignment angle 113 is formed on opposite surfaces of the upper substrate 117 and the lower substrate 119 of the liquid crystal display device.

The optical alignment may be performed on at least one alignment layer.

The next step is to bond the upper substrate 117 and the lower substrate 119 on which the alignment layer 115 is formed to a predetermined gap, and then inject the liquid crystal mixture between the two substrates.

In this case, the liquid crystal mixture is a mixed liquid crystal in which a thermosetting polymer is added to the liquid crystal.

The polymers are very long and thin molecules formed by connecting short molecules to each other through chemical reactions.

Two types of polymers of the above polymers generate a liquid crystal phase.

The first is a structure that is fairly rigid, connected to each other by bendable parts at both ends.

When these long polymers move in the liquid crystal phase and collide with other molecules, the hard part is still directed in one direction.

The second type of polymer is a structure in which, along one fully bendable polymer chain, other rigid parts are suspended by short, bendable connections.

In the polymer liquid crystal phase thus formed, the long, bent polymer chains are wound around the entire material without any direction or positional order.

But the hard parts hanging there have a typical orientation on the liquid crystal.

The thermosetting polymer according to the present invention is a liquid crystal polymer exhibiting nematic properties, and has a property of being cured by thermal.

The next process is to stabilize the mixed state of the liquid crystal mixture.

That is, as shown in FIG. 3B, the liquid crystal mixture 125 injected between the upper substrate 117 and the lower substrate 119 may have the liquid crystal 123 and the polymer 121 through an appropriate aging time. The mixed state of is stabilized. As a result, the thermosetting polymer 121 is positioned between the liquid crystal molecules 123 according to the arrangement of the liquid crystals 123.

The next step is to form a network by applying heat to the polymer.

As shown in FIG. 3C, when the liquid crystal mixture 125 is heat-treated, the polymers 121a located between the liquid crystal molecules 123 are connected to each other and cured to form a network to support the liquid crystal molecules 123. do.

In detail, since the polymer 121 is to be mixed with the nematic liquid crystal, using a material designed to enable thermal curing at a temperature range where the nematic phase is maintained, the nematic direction of the polymer 121 is directed to the ultraviolet ray. The direction is aligned according to the initial orientation of the alignment layer 115 cured and rubbed.

The polymer in the liquid crystal mixture 125 forms a polymer network through a process of stabilizing through a suitable aging time through the process of FIG. 3B and curing by heat, which is anisotropic in an initial direction. Is formed.

Through this, it becomes stably support the liquid crystal molecules 123, it is possible to increase the curled hyacinth (anchoring) for restraining the liquid crystal.

In addition, the orientation regulation force is increased by the surface area increase and the polymer stabilization effect of the thermosetting polymer on the network.

Therefore, the liquid crystal display device according to the present invention can stably restrain the alignment state of the liquid crystal by adding a thermosetting polymer having a nematic property to the nematic liquid crystal constituting the liquid crystal cell, so that the alignment control force between the alignment film and the liquid crystal is reduced. There is an effect to enhance and thereby have an afterimage improvement and light stability characteristics.

Claims (9)

Forming a first and a second alignment layer on each of the first substrate and the second substrate; Aligning the first or second alignment layer; Bonding the first substrate and the second substrate to each other such that the first and second alignment layers face each other and have a predetermined gap; Injecting a mixed liquid crystal containing a thermosetting polymer into a gap between the first substrate and the second substrate to form and age a mixed liquid crystal layer; Heat-treating the thermosetting polymer in the mixed liquid crystal layer to form a network phase Wherein the liquid crystal is rotated according to an applied electric field in the polymer network. The method of claim 1, The alignment treatment is, And arranging light by irradiating the first or second alignment layer with ultraviolet rays. First and second substrates on which at least one photo-alignment film is formed; And a mixed liquid crystal layer comprising a thermosetting polymer and a liquid crystal molecule formed between the first substrate and the second substrate to form a network. The method of claim 1, The thermosetting polymer in the mixed liquid crystal layer has a nematic property, the liquid crystal is a nematic liquid crystal manufacturing method of a liquid crystal display device. The method of claim 1, And the network image is cured after being anisotropically aligned along the alignment direction of the first or second alignment layer. The method of claim 3, wherein And the network phase is formed by being aligned and cured along the initial alignment state of the optical alignment layer by a thermosetting polymer material, wherein the liquid crystal molecules are constrained by the network. The method of claim 3, wherein And the liquid crystal molecules rotate in accordance with an electric field. The method of claim 3, wherein The thermosetting polymer in the mixed liquid crystal layer has a nematic property, the liquid crystal is a nematic liquid crystal display device. The method of claim 3, wherein And the network image is cured after being anisotropically aligned along the alignment direction of the first or second alignment layer.

Images