Patent Publication Number: US-2018030352-A1

Title: Reactive perpendicular aligned material, liquid crystal display panel, and method of liquid crystal alignment

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to a display technology field, and more particularly to a reactive perpendicular aligned material, a liquid crystal display panel, and a method of liquid crystal alignment. 
     BACKGROUND OF THE DISCLOSURE 
     With the development of the display technology, flat display devices such as a liquid crystal display (LCD) are widely employed in various consumer electronics like a mobile phone, a television, personal digital assistance, a digital camera, a laptop, a desktop computer, locating in the mainstream of display devices. 
     Most of liquid crystal display devices on the market are backlight liquid crystal displays, including liquid crystal display panels and backlight modules. The operational principle of a liquid crystal display panel is to dispose liquid crystal molecules on two parallel glass substrates, a number of vertical and horizontal weak currents are between the two glass substrates, which can control the liquid crystal molecules to redirect by power on/off, light from the backlight module can be refracted to show images. 
     A liquid crystal display panel can consist of a color filter (CF) substrate, a thin film transistor (TFT) substrate, a liquid crystal (LC) between the color filter substrate and the thin film transistor substrate, and a sealant. 
     A layer of thin film material is disposed on the CF substrate and the TFT substrate of a liquid crystal display respectively, mainly for aligning liquid crystal molecules, which is named an alignment film (mostly polyimide (PI) material). The main component of the alignment film is a friction alignment PI material or a light alignment PI material, however, both of which have respective flaws. First, the friction alignment PI material can cause problems like dust particles, static electricity residue, brushing streak, which can reduce yield of the product, though the light alignment PI material can avoid the problems above, heat resistance, ageing resistance and LC molecules anchorage are poor due to the property of material, affecting quality of a panel; second, PI materials have strong polarity and hygroscopicity, alignment can be inconsistent after storage and transportation, and the price of PI materials is high, a process of filming on a TFT-LCD is complicated, resulting in increasing costs of a panel. If alignment of liquid crystal molecules can be achieved without a PI film, costs of a panel can be reduced significantly. 
     SUMMARY OF THE DISCLOSURE 
     The objective of the present disclosure is to provide a reactive perpendicular aligned material, a structure of which mainly includes three components—a head group, an intermediate group, and a tail group, primary intentions of the head group, on one hand, is to be anchored on a surface of an inorganic substrate utilizing its polar group by means of physical reaction, on the other hand, is to be anchored on a surface of a substrate by polymerization reaction of double bonds and reactive monomers; primary intentions of the intermediate group and the tail group are similar to that of a polyimide branch, vertically aligning liquid crystal molecules by stereo obstacle. 
     The present disclosure further provides a liquid crystal display panel, a liquid crystal layer includes liquid crystal molecules, the reactive perpendicular aligned materials above, and reactive monomers, under radiation of UV light, the reactive perpendicular aligned materials and the reactive monomers polymerize on a surface of a substrate to anchor liquid crystal molecules, not only simplifying the process of a TFT-LCD, costs of producing a TFT-LCD can also be reduced significantly. 
     The disclosure further provides a method for aligning liquid crystals, disposing liquid crystal molecules, reactive perpendicular aligned materials, and reactive monomers in a liquid crystal layer in a liquid crystal display panel, first applying voltage to the liquid crystal layer to redirect liquid crystal molecules, then radiating the liquid crystal layer with UV light, which can polymerize the reactive perpendicular aligned materials and the reactive monomers on surfaces of a first and a second substrates to anchor liquid crystal molecules, liquid crystal molecules engender a pre-tilt angle after releasing the voltage. 
     The disclosure provides a reactive perpendicular aligned material to achieve the purpose above with a general structural formula of A-Z—R, A is —CH═CH—COOH; Z is 
     
       
         
         
             
             
         
       
     
     where n≧1; R represents a linear chained or a branched chained alkyl group with 5˜20 C atoms, a CH 2  group in the alkyl group is substituted by a phenyl group, a naphthenic base, —CONH—, —COO—, —O—CO—, —S—, —CO— or —CH═CH—, or a F atom or a Cl atom substitutes for a H atom in the alkyl group. 
     A structural formula of the reactive perpendicular aligned material is: 
     
       
         
         
             
             
         
       
     
     The disclosure further provides a liquid crystal display panel, including a first substrate and a second substrate disposed opposite, a liquid crystal layer disposed between the first substrate and the second substrate, a first electrode disposed on a surface of the first substrate towards the liquid crystal layer, and a second electrode disposed on a surface of the second substrate towards the liquid crystal layer; the liquid crystal layer includes liquid crystal molecules, reactive perpendicular aligned materials, and reactive monomers polymerized with reactive perpendicular aligned materials under ultraviolet radiation; a general structural formula of the reactive perpendicular aligned material is A-Z—R, A is —CH═CH—COOH; Z is 
     
       
         
         
             
             
         
       
     
     where n≧1; R represents a linear chained or a branched chained alkyl group with 5˜20 C atoms, a CH 2  group in the alkyl group is substituted by a phenyl group, a naphthenic base, —CONH—, —COO—, —O—CO—, —S—, —CO— or —CH═CH—, or a F atom or a Cl atom substitutes for a H atom in the alkyl group. 
     A structural formula of the reactive perpendicular aligned materials is: 
     
       
         
         
             
             
         
       
     
     The reactive monomer is one or more of following four compounds: 
     
       
         
         
             
             
         
       
     
     In the liquid crystal layer, content of the reactive perpendicular aligned materials is 0.1%˜5 wt %; content of the reactive monomer is 0.01˜0.1 wt %. 
     The first substrate and the second substrate are a CF substrate and a TFT substrate respectively; the first electrode and the second electrode are a common electrode and a pixel electrode respectively. 
     The disclosure further provides a method for aligning liquid crystals, including the following steps: 
     step 1, providing a liquid crystal display panel, including a first substrate and a second substrate disposed opposite, a liquid crystal layer disposed between the first substrate and the second substrate, a first electrode disposed on a surface of the first substrate towards the liquid crystal layer, and a second electrode disposed on a surface of the second substrate towards the liquid crystal layer; the liquid crystal layer including liquid crystal molecules, reactive perpendicular aligned materials, and reactive monomers that polymerize with reactive perpendicular aligned materials under ultraviolet radiation; a general structural formula of the reactive perpendicular aligned materials is A-Z—R, A is —CH═CH—COOH; Z is 
     
       
         
         
             
             
         
       
     
     where n≧1; R represents a linear chained or a branched chained alkyl group with 5˜20 C atoms, a CH 2  group in the alkyl group is substituted by a phenyl group, a naphthenic base, —CONH—, —COO—, —O—CO—, —S—, —CO— or —CH═CH—, or a F atom or a Cl atom substitutes for a H atom in the alkyl group; 
     step 2, applying voltage to two sides of the liquid crystal layer by the first electrode and the second electrode to redirect liquid crystal molecules; 
     step 3, applying voltage to two sides of the liquid crystal layer and simultaneously radiating UV light on the liquid crystal display panel, polymerizing the reactive perpendicular aligned materials and the reactive monomers on the first and the second substrates to anchor liquid crystal molecules; 
     step 4, removing voltage from the two sides of the liquid crystal layer, making liquid crystal molecules to engender a pre-tilt angle. 
     In the liquid crystal layer in a liquid crystal display panel in the step 1, content of the reactive perpendicular aligned materials is 0.1%˜5 wt %; content of the reactive monomer is 0.01˜0.1 wt %. 
     In the step 2 and step 3, a value of the voltage applied to the two sides of the liquid crystal layer is 15˜25V; in the step 3, intensity of the UV light radiated on the liquid crystal display panel is 50˜85 mW/cm 2 ; a wavelength of the UV light is 365 nm. 
     Advantages of the disclosure: the disclosure provides a reactive perpendicular aligned material, a liquid crystal display panel, and a method for aligning liquid crystals, a general structural formula of the reactive perpendicular aligned material is A-Z—R, a head group A plays a role in anchoring, on one hand, it can be anchored on a surface of a substrate utilizing the —COOH group by means of physical reaction, on the other hand, it can strengthen the ability of anchoring liquid crystal molecules by the reaction of a —CH═CH— group and a reactive monomer; primary intentions of an intermediate group Z and a tail group R are similar to that of a polyimide branch, vertically aligning liquid crystal molecules by stereo obstacle; a liquid crystal display panel adopting the reactive perpendicular aligned materials can be without an alignment film, which can simplify the process of a TFT-LCD as well as reducing costs of producing a TFT-LCD significantly; the method for aligning liquid crystals is easily processed and effective in alignment. 
     In order to more clearly illustrate the embodiments of the present disclosure, detailed description and figures relevant to the disclosure can be referred, it is obvious that the drawings are merely for reference and embodiments instead of limiting the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will be described in detail and illustrated by figures to clarify the proposal and the advantages of the disclosure. 
       In figures, 
         FIG. 1  is a structural diagram of a reactive perpendicular aligned material of the present disclosure; 
         FIG. 2  is a structural diagram of a liquid crystal display panel, which is also a diagram of step 1 of a method for aligning liquid crystals of the disclosure; 
         FIG. 3  is a diagram of step 2 of a method for aligning liquid crystals of the disclosure; 
         FIG. 4  is a diagram of step 3 of a method for aligning liquid crystals of the disclosure; 
         FIG. 5  is a diagram of step 4 of a method for aligning liquid crystals of the disclosure; 
         FIG. 6  is a scanning electron microscope photograph of a polymer layer obtained by polymerization of reactive perpendicular aligned materials and reactive monomers on a surface of a substrate in step 3 of a method for aligning liquid crystals according to a preferred embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the present disclosure are described in detail with the accompanying drawings to illustrate the proposal and performance as follows. 
     Referring to  FIG. 1 , The disclosure provides a reactive perpendicular aligned material with a general structural formula of A-Z—R, A is —CH═CH—COOH; Z is 
     
       
         
         
             
             
         
       
     
     where n≧1; R represents a linear chained or a branched chained alkyl group with 5˜20 C atoms, a CH 2  group in the alkyl group is substituted by a phenyl group, a naphthenic base, —CONH—, —COO—, —O—CO—, —S—, —CO— or —CH═CH—, or a F atom or a Cl atom substitutes for a H atom in the alkyl group. 
     Preferably, a structural formula of the reactive perpendicular aligned material is: 
     
       
         
         
             
             
         
       
     
     The disclosure provides a reactive perpendicular aligned material with a general structural formula of A-Z—R, a head group A plays a role in anchoring, on one hand, it can be anchored on a surface of a substrate utilizing the —COOH group by means of physical reaction, on the other hand, it can strengthen the ability of anchoring liquid crystal molecules by the reaction of a —CH═CH— group and a reactive monomer; primary intentions of an intermediate group Z and a tail group R are similar to that of a polyimide branch, vertically aligning liquid crystal molecules by stereo obstacle; a liquid crystal display panel adopting the reactive perpendicular aligned materials can be without an alignment film, which can simplify the process of a TFT-LCD as well as reducing costs of producing a TFT-LCD significantly. 
     Referring to  FIG. 2 , the disclosure further provides a liquid crystal display panel, including a first substrate  1  and a second substrate  2  disposed opposite, a liquid crystal layer  3  disposed between the first substrate  1  and the second substrate  2 , a first electrode  11  disposed on a surface of the first substrate  1  towards the liquid crystal layer  3 , and a second electrode  21  disposed on a surface of the second substrate  2  towards the liquid crystal layer  3 ; the liquid crystal layer  3  includes liquid crystal molecules  31 , reactive perpendicular aligned materials  32 , and reactive monomers  33  polymerized with reactive perpendicular aligned materials  32  under ultraviolet radiation; a general structural formula of the reactive perpendicular aligned materials  32  is A-Z—R, A is —CH═CH—COOH; Z is 
     
       
         
         
             
             
         
       
     
     where n≧1; R represents a linear chained or a branched chained alkyl group with 5˜20 C atoms, a CH 2  group in the alkyl group is substituted by a phenyl group, a naphthenic base, —CONH—, —COO—, —O—CO—, —S—, —CO— or —CH═CH—, or a F atom or a Cl atom substitutes for a H atom in the alkyl group. 
     Preferably, a structural formula of the reactive perpendicular aligned materials  32  is: 
     
       
         
         
             
             
         
       
     
     Specifically, the reactive monomer  33  can be any reactive monomer in polymer stabilized vertically aligned (PSVA) technology. 
     Preferably, the reactive monomer  33  can be one or more of following four compounds: 
     
       
         
         
             
             
         
       
     
     Preferably, in the liquid crystal layer  3 , content of the reactive perpendicular aligned materials  32  is 0.1%˜5 wt %; content of the reactive monomers  33  is 0.01˜0.1 wt %. 
     Specifically, the first substrate  1  and the second substrate  2  are a CF substrate and a TFT substrate respectively; the first electrode  11  and the second electrode  21  are a common electrode and a pixel electrode respectively. 
     Referring to  FIGS. 2-5 , the disclosure further provides a method for aligning liquid crystals, including the following steps: 
     step 1, as shown in  FIG. 2 , providing a liquid crystal display panel, including a first substrate  1  and a second substrate  2  disposed opposite, a liquid crystal layer  3  disposed between the first substrate  1  and the second substrate  2 , a first electrode  11  disposed on a surface of the first substrate  1  towards the liquid crystal layer  3 , and a second electrode  21  disposed on a surface of the second substrate  2  towards the liquid crystal layer  3 ; the liquid crystal layer  3  including liquid crystal molecules  31 , reactive perpendicular aligned materials  32 , and reactive monomers  33  polymerized with the reactive perpendicular aligned materials  32  under ultraviolet radiation; the liquid crystal molecules are arranged perpendicularly to the first substrate  1  and the second substrate  2 . 
     Specifically, a general structural formula of the reactive perpendicular aligned materials  32  is A-Z—R, A is —CH═CH—COOH; Z is 
     
       
         
         
             
             
         
       
     
     where n≧1; R represents a linear chained or a branched chained alkyl group with 5˜20 C atoms, a CH 2  group in the alkyl group is substituted by a phenyl group, a naphthenic base, —CONH—, —COO—, —O—CO—, —S—, —CO— or —CH═CH—, or a F atom or a Cl atom substitutes for a H atom in the alkyl group. 
     Preferably, a structural formula of the reactive perpendicular aligned materials  32  is: 
     
       
         
         
             
             
         
       
     
     Specifically, the reactive monomer  33  can be any reactive monomer in polymer stabilized vertically aligned (PSVA) technology. 
     Preferably, the reactive monomer  33  can be one or more of following four compounds: 
     
       
         
         
             
             
         
       
     
     Preferably, in the liquid crystal layer  3 , content of the reactive perpendicular aligned materials  32  is 0.1%˜5 wt %; content of the reactive monomers  33  is 0.01˜0.1 wt %. 
     Specifically, the first substrate  1  and the second substrate  2  are a CF substrate and a TFT substrate respectively; the first electrode  11  and the second electrode  21  are a common electrode and a pixel electrode respectively. 
     Step 2, as shown in  FIG. 3 , applying a voltage of 15˜25V to two sides of the liquid crystal layer  3  by the first electrode  11  and the second electrode  21  to redirect liquid crystal molecules  31 . 
     Step 3, applying the voltage of 15˜25V to two sides of the liquid crystal layer  3  and simultaneously radiating UV light with intensity of 50˜85 mW/cm 2  on the liquid crystal display panel, polymerizing the reactive perpendicular aligned materials  32  and the reactive monomers  33  on the first substrate  1  and the second substrate  2  to anchor liquid crystal molecules  31 . 
     Preferably, a wavelength of the UV light is 365 nm. 
     Specifically, in the step 3, the polymerization reaction of the reactive perpendicular aligned materials  32  and the reactive monomers  33  is a sort of free radical polymerization reaction: under radiation of UV light, double bonds in the reactive monomers break to generate free radicals, which can lead to a polymerization reaction, the reactive monomers  33  are self-polymerizing and polymerizing with double bonds in the reactive perpendicular aligned materials  32  simultaneously, which can form a crosslinked net structure to intensify ability of anchoring liquid crystal molecules. 
     Step 4, as shown in  FIG. 5 , removing voltage from the two sides of the liquid crystal layer  3 , making liquid crystal molecules  31  to engender a pre-tilt angle. 
     In a preferred embodiment of a method for aligning liquid crystals of the disclosure, a reactive perpendicular aligned material in a liquid crystal layer of a liquid crystal display panel provided by step 1 is 
     
       
         
         
             
             
         
       
     
     a reactive monomer is 
     
       
         
         
             
             
         
       
     
     after step 3, reactive perpendicular aligned materials and reactive monomers polymerize on surfaces of a first and a second substrates to form a polymer layer, a photograph of the polymer layer amplified by a scanning electron microscope with 160-hundred-fold is shown in  FIG. 6 . And after step 4, an achieved liquid crystal display panel is dim under a condition of power-off, which can prove effects of liquid crystal vertical alignment with the method of aligning liquid crystals utilizing reactive perpendicular aligned materials. 
     The present disclosure provides a liquid crystal display panel, a liquid crystal layer includes liquid crystal molecules  31 , the reactive perpendicular aligned materials  32 , and reactive monomers  33  that polymerize with the reactive perpendicular aligned materials  32  under radiation of UV light, a general structural formula of the reactive perpendicular aligned materials  32  is A-Z—R, a head group A plays a role in anchoring, on one hand, it can be anchored on a surface of a substrate utilizing the —COOH group by means of physical reaction, on the other hand, it can strengthen the ability of anchoring liquid crystal molecules by the reaction of a —CH═CH— group and a reactive monomer; primary intentions of an intermediate group Z and a tail group R are similar to that of a polyimide branch, vertically aligning liquid crystal molecules by stereo obstacle; a liquid crystal display panel adopting the reactive perpendicular aligned materials can be without an alignment film, which can simplify the process of a TFT-LCD as well as reducing costs of producing a TFT-LCD significantly. 
     Embodiments I and II are employed to describe preparation methods of two specific structural reactive perpendicular aligned materials: 
     Embodiment I 
     A preparation method of a compound 
     
       
         
         
             
             
         
       
     
     step 1, measuring aromatic amines (I), HCl, NaNO 2  with a mole ratio of 1:(1˜5):(1.01˜1.10), placing the measured aromatic amines (I), hydrochloric acid, and NaNO 2  in a reactor and stirring at 0˜5° C. for 3˜5 hours, adding KI with a mole ratio of 1˜1.2 compared with aromatic amines (I), a product iodobenzene (II) produced after reaction at 25° C. for 1˜5 hours; a reaction equation of the step 1 is as follows: 
     
       
         
         
             
             
         
       
     
     step 2, measuring iodobenzene (II) produced in the step 1 above and acrylic acid with a mole ratio of 1:(2˜3), dissolving the measured iodobenzene (II) and acrylic acid in solvent, employing metal palladium as a catalyst, a compound (III) prepared after reaction at 100° C. for 15˜25 hours; specifically, in the step 2, the solvent can be N-methyl pyrrolidone. 
     A reaction equation of the step 2 is: 
     
       
         
         
             
             
         
       
     
     The produced compound (III) is analyzed by nuclear magnetic resonance, nuclear magnetic resonance data obtained is: δ=0.96 (3H), δ=1.33 (2H), δ=1.29 (2H), δ=1.62 (2H), δ=2.55 (2H), δ=7.18 (2H), δ=7.43 (2H), δ=7.54 (4H), 7.43 (2H), δ=7.36 (2H), δ=7.61 (1H), δ=6.41 (1H), δ=11.0 (1H), which can determine a structural formula of the compound (III) is 
     
       
         
         
             
             
         
       
     
     Embodiment II 
     A preparation method of a compound 
     
       
         
         
             
             
         
       
     
     step 1, measuring aromatic nitrile (IV) and LiAlH 4  with a mole ratio of 1:(1˜3), measuring tetrahydrofuran (THF) with a ratio of 3:1 in mol:L compared with aromatic nitrile (IV), dissolving the measured aromatic nitrile (IV) and LiAlH 4  in tetrahydrofuran; reacting at 72° C. by heating and refluxing for 1˜5 hours, then adding ice water solution including 20 wt % sodium hydroxide with a volume ratio of V(NaOH)/V(THF)=2/1 in the reaction, aromatic nitrile (IV) prepared; a reaction equation of the step 1 is as follows: 
     
       
         
         
             
             
         
       
     
     step 2, measuring aromatic nitrile (IV) produced in the step 1 above, HCl and NaNO 2  with a mole ratio of 1:(1˜5):(1.01:1.10), placing the measured aromatic nitrile (IV), hydrochloric acid and NaNO 2  in a reactor, stirring at 0˜5° C. for 3˜5 hours, adding KI with a mole ratio of 1˜1.2 compared with aromatic nitrile (IV), a product aromatic nitrile (IV) produced after reaction at 25° C. for 1˜5 hours; a reaction equation of the step 2 is as follows: 
     
       
         
         
             
             
         
       
     
     step 3, measuring aromatic nitrile (IV) produced in the step 2 above and acrylic acid with a mole ratio of 1:(2˜3), dissolving the measured aromatic nitrile (IV) and acrylic acid in solvent, employing metal palladium as a catalyst, a compound (VII) prepared after reaction at 100° C. for 15˜25 hours; specifically, in the step 3, the solvent can be N-methyl pyrrolidone. 
     A reaction equation of the step 3 is: 
     
       
         
         
             
             
         
       
     
     The produced compound (VII) is analyzed by nuclear magnetic resonance, nuclear magnetic resonance data obtained is: δ=0.96 (3H), δ=1.33 (2H), δ=1.29 (2H), δ=1.62 (2H), δ=2.55 (2H), δ=7.18 (2H), δ=7.43 (2H), δ=7.54 (4H), δ=7.43 (2H), δ=7.36 (2H), δ=7.61 (1H), δ=6.41 (1H), δ=11.0 (1H), which can determine a structural formula of the compound (VII) is 
     
       
         
         
             
             
         
       
     
     Overall, the disclosure provides a reactive perpendicular aligned material, a liquid crystal display panel, and a method for aligning liquid crystals, a general structural formula of the reactive perpendicular aligned material is A-Z—R, a head group A plays a role in anchoring, on one hand, it can be anchored on a surface of a substrate utilizing the —COOH group by means of physical reaction, on the other hand, it can strengthen the ability of anchoring liquid crystal molecules by the reaction of a —CH═CH— group and a reactive monomer; primary intentions of an intermediate group Z and a tail group R are similar to that of a polyimide branch, vertically aligning liquid crystal molecules by stereo obstacle; a liquid crystal display panel adopting the reactive perpendicular aligned material can be without an alignment film, which can simplify the process of a TFT-LCD as well as reducing costs of producing a TFT-LCD significantly; the method for aligning liquid crystals is easily processed and effective in alignment. 
     It is understandable in practical to a person skilled in the art that all or portion of the processes in the method according to the aforesaid embodiment can be accomplished with modifications and equivalent replacements, which should be covered by the protected scope of the disclosure.