referring to fig6 a to 6 f , which are sketches of physical characters of a retardation film in optoelectronics field . as shown in fig6 a , which is a coordination chart defining three coordination axes x , y and z . generally retardation film has been divided by three , a - plate shown as fig6 b and fig6 c , c - plate shown as fig6 e and fig6 f and biaxial film shown as 6 d . a - plate has a p - a - plate ( positive a - plate ) shown as fig6 b and a n - a - plate ( negative a - plate ) shown as fig6 c , the two physical characters of the p - a - plate and n - a - plate are : c - plate has a p - c - plate ( positive c - plate ) shown as fig6 f and a n - c - plate ( negative c - plate ) shown as fig6 e , the two physical characters of the p - c - plate and n - c - plate are : the characters of the biaxial film shown as fig6 d are nx & gt ; ny & gt ; nz , wherein nx is defined as the refraction rate of the x axis , ny is defined as the refraction rate of the y axis and nz is defined as the refraction rate of the z axis . accordingly , the following equation is defined a plane refraction of r 0 and a thickness refraction of rth , such as : r 0 =( nx − ny )* d , rth =((( nx + ny )/ 2 )− nz )* d or rth =( nx − nz )* d , wherein d is defined as a path of light going through a medium . depending on above description , the refraction rate of the x axis for p - a - plate is the greatest , the refraction rates of the y and z axes are equal ; the refraction rate of the y axis for n - a - plate is the smallest , the refraction rates of the x and z axes are equal ; the refraction rate of the z axis for p - c - plate is the greatest , the refraction rates of the y and x axes are equal ; the refraction rate of the z axis for n - c - plate is the smallest , the refraction rates of the y and x axes are equal ; the refraction rate of the x axis for biaxial film is the greatest , the refraction rate alone the y axis is middle , and the smallest being for the refraction rate of the z axis . referring to fig7 a and 7b , which are alignment sketches of a lc cell layer of a multi - domain vertical alignment liquid crystal display , and shows two stages of vertical grains and inclined grains of mva - lcd . while in an “ off ” state , that is , there is no electrical field existed , shown in fig7 a , almost each grain is perpendicular to two substrates , and a dark state on the lcd at the “ off ” state ; while in an “ on ” state , which means some voltages being applied in , shown in fig7 b , and almost each grain is inclined to two substrates to present a light state on the lcd . referring to fig8 , which is an alignment sketch of a preferred embodiment of the present invention . the lc cell layer in fig6 is now arranged in a middle portion as a lc cell layer 15 . the present invention discusses that how to compensate the phase differences while the lc cell layer 15 being in dark state or light state . the embodiment mainly organizes a lcd , the alignment sequence of the lcd from a top to a bottom is an upper surface treatment layer 11 ; an upper polarized plate including a first tac ( tri - acetic - cellulose ) 12 , a first pva ( poly - vinyl - alcohol ) 13 and a second tac 14 ; the lc cell layer 15 ; a lower polarized plate including a first biaxial film 16 , a second biaxial film 17 , a second pva 18 and a third tac 19 ; a lower surface treatment layer 20 . while the lc cell layer 15 is in dark state , the grains stand up , therefore the refraction along the thickness direction is caused and must be compensated by other retardation films , the refraction along the thickness direction is signed as rth previously , hence , the installed second tac 14 , the first biaxial film 16 and the second biaxial film 17 are capable of compensating rth of lc cell layer 15 ; while the lc cell layer 15 is in light state , the grains are inclined , therefore the refraction along the plane directions are caused and must be compensated by other retardation films , the refraction along the plane directions is signed as r 0 previously , hence , the first biaxial film 16 and the second biaxial film 17 are capable of compensating r 0 of lc cell layer 15 . it is now that all of the refractions being compensated . other layers , the upper surface treatment layer 11 and the lower surface treatment layer 20 , are provided to have characters of protection , anti - glare , anti - reflection , scratchproof , anti - pollution , anti - static , etc ; the first pva 13 and the second pva 18 are polarized plates to percolate light for purifying ; the first tac 12 and the third tac 19 are with protection feature . above is the first preferred embodiment , however , there are some other alignments for the first tac 12 , the first pva 13 , the second tac 14 , the first biaxial film 16 , the second biaxial film 17 , the second pva 18 and the third tac 19 , that is , other two preferred embodiments , which are : a second preferred embodiment has an upper polarized plate of a tac , a pva , a first biaxial film and another tac aligned from top to bottom and a lower polarized plate of a second biaxial film , a pva and a tac aligned from top to bottom as well ; a third preferred embodiment has an upper polarized plate of a tac , a pva , a first biaxial film and a second biaxial film aligned from top to bottom and a lower polarized plate of a tac , a pva and another tac . for the material of tac afore mentioned , it can be instead of pc or coc . further , in order to that the retardation device of the present invention having effects of increasing view angle , contrast in full view angle and saturation , the lower polarized plate in the first preferred embodiment has two biaxial films . based on the compensations of the two biaxial films , a glow level in dark state is the lowest , especially the compensations being better in the scopes of 45 ° to 225 ° and 135 ° to 315 °. as a conclusion , the contrast value will be greater than 20 while in full view angle ; on the other hand , color saturation is specially and relatively promoted on account of the two biaxial films . although this invention has been disclosed and illustrated with reference to particular embodiments , the principles involved are susceptible for use in numerous other embodiments that will be apparent to persons skilled in the art . this invention is , therefore , to be limited only as indicated by the scope of the appended claims .