TWI386730B - Liquid crystal alignment process - Google Patents

Description

Liquid crystal alignment process

The present invention relates to a process for a liquid crystal display panel, and more particularly to a liquid crystal alignment process.

With the advancement of flat display technology and the advantages of flat panel display, such as light weight, small size and power saving, flat panel displays have become more and more popular. Common flat panel displays include liquid crystal display (LCD), plasma display panel (PDP), organic light emitting diode display (OLED display), and electrophoretic display (EPD). ), among them, the popularity of liquid crystal displays is the highest.

The liquid crystal display includes a liquid crystal display panel (LCD panel) and a backlight module, wherein the backlight module is used to provide a display light source to the liquid crystal display panel. In addition, the liquid crystal display panel uses an electric field to control the geometrical changes of the liquid crystal molecules to change the transmission path and phase of the light, and in order to control the order and direction of the liquid crystal molecules, a liquid crystal alignment process is generally performed. The liquid crystal alignment process can be divided into a plurality of types, one of which is a polymerized liquid crystal alignment process.

The polymerized liquid crystal alignment process first adds a monomer material to a liquid crystal layer, and then performs a first exposure process to polymerize the monomer material to form a polymer stable alignment layer. In addition, since the monomer material cannot be completely polymerized in the first exposure process, a second exposure process is performed in the prior art in order to polymerize the remaining monomer material.

Figure 1 is a graph of the absorption wavelengths of two monomer materials, with the horizontal axis being the wavelength and the vertical axis being the extinction. It can be seen from Fig. 1 that the absorption wavelength of the monomer material is between about 220 nm (nm) and 340 nm, but the above The double exposure process uses ultraviolet light having a dominant wavelength of about 365 nm, so even if the exposure process is performed twice, the residual amount of the monomer material is still too high. As such, the liquid crystal display panel will be poorly performing in the image sticking test.

The invention provides a liquid crystal alignment process to improve the reliability of the liquid crystal display panel.

In order to achieve the above advantages, the present invention provides a liquid crystal alignment process comprising the following steps. First, a first substrate and a second substrate are provided. Next, a liquid crystal layer is provided between the first substrate and the second substrate, wherein the liquid crystal layer comprises a liquid crystal composition, a monomer material, and a polymerization initiator. Then, a first exposure process is performed to polymerize a portion of the monomer material to form a dipolymer stable alignment layer in the liquid crystal layer, and the second polymer stable alignment layer is respectively located between the liquid crystal layer and the first substrate. A contact surface and a second contact surface between the liquid crystal layer and the second substrate cause the plurality of liquid crystal molecules in the liquid crystal composition to be aligned along a pretilt angle. Then, a second exposure process is performed to polymerize the remaining monomer material, wherein the second exposure process uses light having a dominant wavelength between 290 nm and 340 nm to illuminate the remaining monomer material.

In an embodiment of the invention, the second exposure process is performed by using a light source with at least one filter to provide light having a dominant wavelength between 290 nm and 340 nm.

In an embodiment of the invention, the filter is a soda-lime glass.

In an embodiment of the present invention, the second exposure process is to provide light having a main wavelength between 290 nm and 340 nm by a light source, and the material of the light source is sodium. Calcium glass.

In one embodiment of the invention, the second exposure process described above is to continuously illuminate the remaining monomer material using light having a dominant wavelength between 290 nm and 340 nm.

In one embodiment of the invention, the second exposure process described above intermittently illuminates the remaining monomer material using light having a dominant wavelength between 290 nm and 340 nm.

In one embodiment of the invention, the light intensity measured by the photometer for measuring the light used in the second exposure process is greater than 0 milliwatts per square centimeter (mW/cm ² ), and the photometer is for 313 nm. Light has the greatest relative sensitivity.

In the liquid crystal alignment process of the present invention, since the second exposure process uses light having a main wavelength between 290 nm and 340 nm to illuminate the remaining monomer material, damage to the liquid crystal molecules can be avoided, and Most of the monomer materials are polymerized, which in turn greatly reduces the amount of residual monomer material. Therefore, the liquid crystal alignment process of the present invention can improve the reliability of the liquid crystal display panel.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

2A to 2E are flow charts of a liquid crystal alignment process according to an embodiment of the present invention. Referring first to FIG. 2A, the liquid crystal alignment process of this embodiment includes the following steps. First, a first substrate 110 and a second substrate 120 are provided. The first substrate 110 is, for example, an active device array substrate, and the second substrate 120 is, for example, a pair of substrates.

Next, as shown in FIG. 2B, a liquid crystal layer 130 is provided between the first substrate 110 and the second substrate 120, wherein the liquid crystal layer 130 includes a liquid crystal composition 132, a monomer material 134, and a polymerization initiator (Fig. Not shown). Further, the liquid crystal composition 132 includes a plurality of liquid crystal molecules 133.

Next, an electric field is applied to align the liquid crystal molecules 133 in the liquid crystal composition 132 along a pretilt angle, and a first exposure process is performed together while applying an electric field to polymerize a portion of the monomer material 134. The two polymer stable alignment layer 140 is in the liquid crystal layer 130, and the two polymer stable alignment layer 140 is respectively located between a first contact surface between the liquid crystal layer 130 and the first substrate 110 and between the liquid crystal layer 130 and the second substrate 120. A second contact surface is shown in Figure 2C. In the present embodiment, the light 50 used in the first exposure process is ultraviolet light, and the main wavelength of the light 50 generally used in the first exposure process is about 365 nm, but not limited thereto. Specifically, in order to avoid damage to the liquid crystal molecules 133, light rays 50 having a wavelength greater than 290 nm may be selected in the first exposure process.

Then, as shown in FIG. 2D, a second exposure process is performed to polymerize the remaining monomer material 134, wherein the second exposure process is performed using light 62 having a dominant wavelength between 290 nm and 340 nm. The remaining monomer material 134. Further, the method of irradiating the remaining monomer material 134 may be continuous irradiation or intermittent irradiation. Further, in the present embodiment, the polymerization effect of the monomer material 134 can be enhanced by limiting the light intensity of the light 62. Specifically, when the light 62 used in the second exposure process is measured by a photometer having a maximum relative sensitivity to 313 nm of light, the measured light intensity is, for example, greater than 0 mW/cm 2 .

The absorption wavelength of the monomer material 134 ranges from about 220 nm to about 340 nm, and this range largely overlaps with the absorption wavelength of the liquid crystal molecules 133. In order to avoid damage to the liquid crystal molecules 133, the main wavelength of the light 62 used in the second exposure process in this embodiment needs to be greater than 290 nm, which can greatly reduce the damage caused by the second exposure process to the liquid crystal molecules 133. Therefore, after the second exposure process, the voltage holding ratio of the liquid crystal molecules 133 (voltage holding ratio, VHR) can still be higher than 98% at 60 Hz and 1 volt.

In addition, since the range of the main wavelength of the light 62 used in the second exposure process is in the range of the absorption wavelength of the monomer material 134, the remaining monomer material 134 can be effectively polymerized to substantially reduce the monomer material. 134 residual amount. Therefore, the liquid crystal display panel 100 (shown in FIG. 2E) obtained after the second exposure process can perform well in the afterimage test. In other words, the liquid crystal alignment process of the embodiment can improve the reliability of the liquid crystal display panel 100.

Referring to FIG. 2D again, in the second exposure process, the light source 62 is provided by the light source 60, and a portion of the wavelength band of the light 62 is filtered by the at least one filter 70 to be irradiated to the liquid crystal layer 130. The primary wavelength of light 62 is greater than 290 nm. Specifically, the filter 70 may be soda lime glass having a penetration wavelength as shown in FIG.

In addition, referring to FIG. 4, in the second exposure process, the tube 82 of the tube body 82 made of soda lime glass may be used to provide the light 84 to illuminate the liquid crystal layer 130. Since the material of the tube 82 of the bulb 80 is soda lime glass, the main wavelength of the light 84 irradiated to the liquid crystal layer 130 can be greater than 290 nm.

In summary, in the liquid crystal alignment process of the present invention, since the second exposure process uses light having a main wavelength between 290 nm and 340 nm to illuminate the remaining monomer material, liquid crystal molecules can be avoided. Damage, and can make the majority of monomer materials polymerize, thereby significantly reducing the residual amount of monomer materials. Thus, not only the liquid crystal molecules can have a high voltage holding ratio, but also the liquid crystal display panel can perform well in the afterimage test. Therefore, the liquid crystal alignment process of the present invention can improve the display quality of the liquid crystal display panel.

While the present invention has been described above in terms of the preferred embodiments, it is not intended to limit the invention, and those of ordinary skill in the art can make a few changes and modifications without departing from the spirit and scope of the invention. Therefore the protection of the present invention The scope is subject to the definition of the scope of the patent application attached.

50, 62, 84‧‧‧ rays

60, 80‧‧‧ lamps

70‧‧‧Filter

82‧‧‧ tube body

100‧‧‧LCD panel

110‧‧‧First substrate

120‧‧‧second substrate

130‧‧‧Liquid layer

132‧‧‧Liquid composition

133‧‧‧liquid crystal molecules

134‧‧‧Single material

140‧‧‧Polymer stable alignment layer

Figure 1 is a graph of the absorption wavelengths of two monomer materials.

2A to 2E are flow charts of a liquid crystal alignment process according to an embodiment of the present invention.

Figure 3 is a graph of the penetration wavelength of soda lime glass.

4 is a schematic view showing a second exposure process of a liquid crystal alignment process according to another embodiment of the present invention.

60‧‧‧ lamps

62‧‧‧Light

70‧‧‧Filter

110‧‧‧First substrate

120‧‧‧second substrate

130‧‧‧Liquid layer

132‧‧‧Liquid composition

133‧‧‧liquid crystal molecules

134‧‧‧Single material

140‧‧‧Polymer stable alignment layer

Claims (8)

A liquid crystal alignment process includes: providing a first substrate and a second substrate; providing a liquid crystal layer between the first substrate and the second substrate, wherein the liquid crystal layer comprises a liquid crystal composition, a single material, and a polymerization initiator; applying an electric field while performing a first exposure process to polymerize a portion of the monomer material to form a dipolymer stable alignment layer respectively located between the liquid crystal layer and the first substrate a contact surface and a second contact surface between the liquid crystal layer and the second substrate, so that the plurality of liquid crystal molecules in the liquid crystal composition are aligned along a pretilt angle, wherein the first exposure process uses a dominant wavelength of about 365 Light of the nano; and performing a second exposure process to polymerize the remaining monomer material, wherein the second exposure process uses light having a dominant wavelength between 290 nm and 340 nm to illuminate the remaining The monomer material, the second exposure process is coupled with at least one filter by a light source to provide light having a dominant wavelength between 290 nm and 340 nm, the filter being soda lime glass. The liquid crystal alignment process of claim 1, wherein the second exposure process continuously irradiates the remaining monomer material with light having a dominant wavelength between 290 nm and 340 nm. The liquid crystal alignment process of claim 1, wherein the second exposure process intermittently illuminates the remaining monomer material using light having a dominant wavelength between 290 nm and 340 nm. The liquid crystal alignment process of claim 1, wherein the photometric measured by the photometer used in the second exposure process is greater than 0 mW/cm 2 , and the photometer is for 313 Nai The light of rice has the greatest relative sensitivity. A liquid crystal alignment process comprising: Providing a first substrate and a second substrate; providing a liquid crystal layer between the first substrate and the second substrate, wherein the liquid crystal layer comprises a liquid crystal composition, a monomer material, and a polymerization initiator; Simultaneously performing a first exposure process together with an electric field to polymerize a portion of the monomer material to form a dipolymer stable alignment layer, a first contact surface between the liquid crystal layer and the first substrate, and a liquid crystal layer and a first a second contact surface between the two substrates such that the plurality of liquid crystal molecules in the liquid crystal composition are aligned along a pretilt angle, wherein the first exposure process uses light having a dominant wavelength of approximately 365 nm; Performing a second exposure process to polymerize the remaining monomer material, wherein the second exposure process irradiates the remaining monomer material with light having a dominant wavelength between 290 nm and 340 nm. The second exposure process is to provide light having a main wavelength between 290 nm and 340 nm by a light source, and one of the light sources is made of soda lime glass. The liquid crystal alignment process of claim 5, wherein the second exposure process continuously irradiates the remaining monomer material with light having a dominant wavelength between 290 nm and 340 nm. The liquid crystal alignment process of claim 5, wherein the second exposure process intermittently illuminates the remaining monomer material using light having a dominant wavelength between 290 nm and 340 nm. The liquid crystal alignment process of claim 5, wherein the photometric measured by the photometer used in the second exposure process is greater than 0 mW/cm 2 , and the photometer is for 313 Nai The light of rice has the greatest relative sensitivity.