Alignment films in a liquid crystal display device and a method of manufacturing the same

Abstract

A liquid crystal display device including a pair of substrates in a spaced relationship with one another. A pair of alignment films are provided, one alignment film being formed on each substrate such that the alignment films face one another. A liquid crystal layer, including plural liquid crystals, is inserted between the pair of alignment films, wherein the alignment films impart a given pre-tilt angle to the liquid crystals. The alignment films are composed of a material containing at least two types of polymers having a prescribed initial alignment and different alignment variation rates in response to ultra-violet ray irradiation. The pre-tilt angle being adjusted, without rubbing the alignment films, through ultraviolet exposure of the alignment films.

What is claimed is:  
     
         1 . A liquid crystal display device comprising: 
 a pair of substrates in a spaced relationship with one another;    a pair of alignment films, one said alignment film formed on each said substrate such that said alignment films face one another; and    a liquid crystal layer, including plural liquid crystals, inserted between said pair of alignment films;    said alignment films imparting a given pre-tilt angle to the liquid crystals, said alignment films being composed of a material containing at least two types of polymers having a prescribed initial alignment and different alignment variation rates in response to ultraviolet light irradiation;    wherein said given pre-tilt angle is adjusted, without rubbing said alignment films, by exposing said alignment films to ultraviolet light.    
     
     
         2 . A liquid crystal display device according to  claim 1 , whereby at least one of said alignment films is comprised of a material containing mixtures of said polymers.  
     
     
         3 . A liquid crystal display device according to  claim 1 , whereby said alignment film is comprised of material containing copolymers of said polymers.  
     
     
         4 . A liquid crystal display device according to  claim 1 , whereby one type of said two types of polymers changes an orientation of the liquid crystal molecules from an initial orientation, and the other type of said two types of polymers generally maintains said initial orientation of said liquid crystal molecules.  
     
     
         5 . A liquid crystal display device according to  claim 4 , whereby said initial state of orientation is a vertical, and said one type of said two types of polymers changes an orientation of the liquid crystal molecules from said initial orientation to a random horizontal orientation.  
     
     
         6 . A liquid crystal display device according to  claim 1 , wherein said alignment films are comprised of a mixture of polymer x 1  which exhibits a change of pre-tilt angle of at least 2° when irradiated with 0.5 (J/cm 2 ) of ultra-violet rays and a polymer x 2  which exhibits a change of pre-tilt angle of generally 0.5° when irradiated with at least 0.5 (J/cm 2 ) of ultra-violet rays.  
     
     
         7 . A liquid crystal display device according to  claim 6 , wherein said alignment films are composed of at least one of polyimide and polyamic oxide.  
     
     
         8 . A liquid crystal display device according to  claim 7 , wherein said alignment films are comprised of a 20:80 mixture of polymer x 1  and polymer x 2 .  
     
     
         9 . A method of aligning an alignment film used to orient liquid crystal molecules in a liquid crystal display device, said method comprising the steps of: 
 forming an alignment film a substrate, said alignment film being composed of at least two different types of polymers, each type of polymer exhibiting differing alignment variation in response to ultra-violet ray irradiation;    irradiating said alignment film with ultra-violet rays at an oblique angle with respect to a surface of said alignment film.    
     
     
         10 . A method of forming an alignment film according to  claim 9 , wherein said oblique angle is generally less than 45°.  
     
     
         11 . A method of forming an alignment film according to  claim 9 , wherein said alignment film is comprised of a mixture of polymer x 1  which exhibits a change of pre-tilt angle of at least 2° when irradiated with 0.5 (J/cm 2 ) of ultra-violet rays and a polymer x 2  in which the change of pre-tilt angle is 0.5° when irradiated with 0.5 (J/cm 2 ) of ultra-violet rays.  
     
     
         12 . A method of forming an alignment film according to  claim 9 , wherein a pre-tilt angle of one type of said at least two types of polymers changing from an initial vertical orientation to a random horizontal orientation in response to ultra-violet irradiation, and another type of said at least two types of polymers generally retains said initial vertical orientation.  
     
     
         13 . A method of forming an alignment film according to  claim 9 , wherein said alignment film is composed of at least one of polyimide and polyamic oxide.  
     
     
         14 . A method of forming an alignment film according to  claim 11 , wherein said alignment films are comprised of a 20:80 mixture of polymer x 1  and polymer x 2 .  
     
     
         15 . An alignment film applied to opposing faces of a pair of substrates in a liquid crystal display device and aligning liquid crystal layer disposed therebetween, the alignment film comprising: 
 a material containing at least two types of polymers with differing alignment variation rates in response to ultra-violet ray irradiation, both said two types of polymers having a prescribed initial alignment for the liquid crystal molecules in the liquid crystal layer.    
     
     
         16 . The alignment film according to  claim 15 , wherein said material includes mixtures of the polymers.  
     
     
         17 . The alignment film according to  claim 15 , wherein said material contains a copolymer of the polymers.  
     
     
         18 . The alignment film according to  claim 15 , wherein an alignment of one of the two polymers readily changes from said initial alignment to a second alignment in response to ultraviolet light exposure, and the other of the two polymers is highly resistant to changes in alignment in response to ultraviolet light exposure.  
     
     
         19 . The alignment film according to  claim 18 , wherein the initial alignment is vertical, and the second alignment is horizontal.  
     
     
         20 . An alignment apparatus for adjusting the alignment of an alignment film with ultraviolet light, said apparatus comprising: 
 a light source to irradiate scattered ultraviolet light; and    an optical mask disposed under said light source and formed with at least one slit, wherein diffuse light, centered on said slit, is generated by placing said optical mask above said alignment film and irradiating scattered light from said light source through said optical mask;    wherein said diffuse light exposes said alignment film, and produces domains in said liquid crystal that depend on the directions of diffusion of the diffuse light.    
     
     
         21 . The alignment apparatus according to  claim 20 , wherein said at least one slit is stripe-shaped.  
     
     
         22 . The alignment apparatus according to  claim 20 , wherein said optical mask is disposed so that said slit is positioned in a region roughly parallel to a data electrode formed in a lower part of said alignment film.  
     
     
         23 . The alignment apparatus according to  claim 20 , wherein said optical mask is disposed so that the slit is positioned in a region that is roughly parallel to a gate electrode formed in a lower part of the alignment film.  
     
     
         24 . The alignment apparatus according to  claim 20 , wherein said light source is a tubular-shaped lamp.  
     
     
         25 . The alignment apparatus according to  claim 24 , wherein said optical mask and said light source are disposed so that a lengthwise direction of said slit and a lengthwise direction of said light source are one of parallel and orthogonal.  
     
     
         26 . The alignment apparatus according to  claim 25 , further comprising a cold mirror installed to cover a back of said light source, said cold mirror absorbing infrared light; 
 wherein said alignment film is irradiated with the reflected light from said cold mirror as scattered light in the surface along the lengthwise direction of the light source and as parallel light in the surface perpendicular to the lengthwise direction of said light source.    
     
     
         27 . A method for adjusting the alignment of an alignment film in a liquid display device and orients liquid crystal sandwiched between a pair of alignment films, said method comprising the steps of: 
 placing an optical mask formed with slits above one of the alignment films;    irradiating the optical mask with scattered light from a light source irradiating scattered ultraviolet light, whereby diffuse light centered on said slit spreads out and exposes the alignment film with said diffuse light, and produces domains in said liquid crystal that depend on the directions of diffusion of the diffuse light.    
     
     
         28 . An alignment apparatus for exposing an alignment film with ultraviolet light and orients liquid crystal sandwiched between a pair of alignment films, said apparatus comprising: 
 a light for producing ultraviolet light;    an optical mask that is disposed under said light source, said optical mask having a slit; and    an ultraviolet light scattering mechanism formed on said slit;    wherein said optical mask is placed above said alignment film and ultraviolet light is irradiated from said light source through said optical mask thereby producing diffuse light, centered on said slit, that spreads out and exposes said alignment film;    further wherein domains that depend on the directions of diffusion of the diffuse light are produced in said liquid crystal by the exposure.    
     
     
         29 . A liquid crystal display device that is provided with a pair of substrates, that are maintained in a facing relationship with a prescribed interval defined therebetween, comprising: 
 a pair of alignment films, one alignment film being provided on each substrate such that said pair of alignment films are in an opposing relationship;    a liquid crystal layer provided between the alignment films, wherein the alignment films provide a given pretilt angle to liquid crystals disposed therebetween;    pixel electrodes formed on one of the substrates provide an alignment control force that is directed in the direction that cancels the orientations due to the electric fields generated at the ends of the pixel electrodes to the liquid crystal molecules in the region corresponding to the ends of said pixel electrodes.    
     
     
         30 . The liquid crystal display device according to  claim 29 , wherein the liquid crystal layer has prescribed domains on the pixel electrodes by controlling the alignment of the alignment film.  
     
     
         31 . A liquid crystal display device, comprising: 
 a pair of substrates which are maintained at a prescribed interval;    an alignment film on each substrate, such that the alignment films faces each other;    a liquid crystal layer provided between the alignment films;    a plurality of domains being produced at prescribed boundaries in the liquid crystal; and    a surface energy of the alignment film reaches one of a maximum and a minimum at the prescribed boundaries of the domains and one of decreases and increases when moving away from the boundaries.    
     
     
         32 . The liquid crystal display device according to  claim 31 , wherein the alignment films imparting a given pre-tilt angle to the liquid crystals, said alignment films being composed of a material containing at least two types of polymers having a prescribed initial alignment and different alignment variation rates in response to ultra-violet ray irradiation.  
     
     
         33 . The liquid crystal display device according to  claim 32 , wherein said prescribed initial alignment is vertical, and the alignment of said alignment films becomes constant near 90° when a given threshold of ultraviolet light exposure is exceeded.  
     
     
         34 . The liquid crystal display device according to  claim 31 , wherein said alignment film has a property of starting to change alignment from said prescribed initial alignment in response to ultraviolet light exposure and resuming said prescribed initial alignment when irradiated again by ultraviolet light.  
     
     
         35 . An alignment method for providing a prescribed alignment to an alignment film used to orient liquid crystals, said method comprising: 
 providing a light source which generates ultraviolet light;    providing a substrate having an alignment film therein, providing an optical mask between the light source and the substrate, the optical having at least one slit defined therein;    irradiating the optical mask with ultraviolet light such that diffuse ultraviolet light that spreads out is transmitted through the slit and exposes the alignment film and produces domains in said liquid crystal that depend on the directions of diffusion of the diffuse light.    
     
     
         36 . The alignment method according to  claim 35 , wherein: 
 each alignment film is divided into two domains to produce mutually different orientations in a plurality of regions, and the orientations are controlled to tilt the liquid crystal molecules in mutually opposite directions;    further wherein the initial alignment is one of vertical and horizontal.    
     
     
         37 . A liquid crystal display device, comprising: 
 a pair of substrates which are maintained at a prescribed interval;    an alignment film on each substrate, such that the alignment films faces each other;    a liquid crystal layer provided between the alignment films;    one of said substrates having pixel electrodes formed thereon with bus lines formed between the pixel electrodes, said substrate having slits defined roughly parallel to the bus lines in the vicinity of said bus lines in said pixel electrodes.    
     
     
         38 . An alignment apparatus for configuring an alignment of an alignment film used to orient liquid crystals, said apparatus comprising: 
 a light source for irradiating ultraviolet light;    an optical mask provided under said light source and having an ultraviolet light scattering mechanism formed thereon;    wherein said optical mask is disposed above said alignment film such that diffuse ultraviolet light passes through said optical mask, exposes the alignment film and produces domains in said liquid crystal that depend on the directions of diffusion of the diffuse light.    
     
     
         39 . The alignment apparatus according to  claim 38 , wherein the scattering mechanism is formed on the surface of the optical mask on the light source side.  
     
     
         40 . The alignment apparatus according to  claim 38 , wherein said optical mask is provided with a slit, and said scattering mechanism is formed in the opening of the slit.  
     
     
         41 . The alignment apparatus according to  claim 38 , wherein the optical mask has stripe shaped slits formed therein for diffusing the ultraviolet light.  
     
     
         42 . The alignment apparatus according to  claim 38 , wherein when the optical mask is disposed above an upper part of the alignment film, a slit formed in said optical mask is positioned is roughly parallel to a data electrode in a lower part of said alignment film.  
     
     
         43 . The alignment apparatus according to  claim 38 , wherein when the optical mask is disposed above an upper part of the alignment film, a slit formed in said optical mask is positioned roughly parallel to a gate electrode formed in a lower part of said alignment film.  
     
     
         44 . A method for manufacturing a liquid crystal display device, comprising: 
 providing with a pair of substrates which are maintained at a prescribed interval, each substrate having an alignment film such that the alignment films face each other;    providing a liquid crystal layer between the alignment films;    provides an alignment control force that is directed in the direction that cancels the orientations due to the electric field generated at the ends of the pixel electrodes to the liquid crystal molecules in the region corresponding to the ends of the pixel electrodes formed on one of the substrates.    
     
     
         45 . A method for manufacturing a liquid crystal display device, comprising: 
 providing with a pair of substrates which are maintained at a prescribed interval, each substrate having an alignment film such that the alignment films face each other;    providing a liquid crystal layer between the alignment films;    provides an alignment control force that is directed in the direction that cancels the orientations due to the electric field generated at the ends of the pixel electrodes to the liquid crystal molecules in the region corresponding to the ends of the pixel electrodes formed on one of the substrates.