Effect of Imidization Temperature and Spinning Condition on Structure of Polyimide Film Derived from Cyclobutanedianhydride and 2,2-Bis(4-aminophenoxyphenyl)propane

Abstract

ABSTRACT:The polyimide derived from cyclobutanedianhydride and 2,2-bis(4-aminophenoxyphenyl)propane (CBDA-BAPP) is one of the typical materials for liquid crystal alignment layer in liquid crystal display (LCD). The effects ofimidization temperature and spinning condition on degree of imidization, and in-plane orientation of the CBDA-BAPP film were studied. The imidization temperature at 200"C was found to be insufficient for complete imidizaiion of the amic acid group. The in-plane orientations of the CBDA-BAPP films imidizcd at 200cc and 250''C were similar to each other, although they were higher than that of the film imidized at l 50°C. With increasing the spinning rate and decreasing the solution concentration in the spin-casting procedure, the degree of imidization was decreased, together with the increasing in-plane orientation which would be mainly governed by chain immobilization rate over the chain stiffness.KEY WORDS Cyclobutanedianhydride-2,2-Bis(4-aminophenoxyphenyl)propane / Thermal Imidization / Degree of Imidization / In-Plane Orientation / Residual Solvent / The polyimide derived from cyclobantanedianhydride and 2,2-bis(4-aminophenoxyphenyl)propane (CBDA-BAPP) has been used for liquid crystal alignment layer (SE-150, Nissan Chemical Industries Co., Ltd.) 1 -3 and can be also used as photoresist due to the decomposition of the cyclobutane ring by UV irradiation. 4 Among these applications, it is usually interfaced with substrate and prepared from the spin-coating of the polyamic acid on substrate followed by prebaking, and thermal imidization leading the structure evolution.The properties of polyimides are controlled by the change in the structure of film or coating, which is dependent on the conditions used to cure the polyamic acid. 5 -9 The imidization temperature, which is highly important in processing related to the conversion of amic acid group into imide and the molecular orientation of the imide chain, is often restricted in the production of liquid crystal alignment layer. because color elements applied to the usual color filter layer easily fade at high temperatures. 10 At present, since there are no color elements with high temperature durability and good adaptability to the liquid crystal display (LCD) cell, the temperature of heat treatment during the cell assembling should be kept under 250°C. Therefore, it is necessary to obtain the information on the structural change of the CBDA-BAPP at the temperature lower than 250°C.In addition, it should be noted that the spinning condition can vary with the degree of imidization and the molecular orientation, in turn, the properties of the film. 11 -l 3 The thickness of the film and the residual solvent content of the cast polyamic acid depend on spinning condition, and these differences could lead to the different structure of the resulting polyimide film.The present study reports the effect of imidization temperature and spinning conditions on degree of imidization, chain orientation of the CBDA-BAPP film 1 To whom correspondence shoul...

Thermal imidization behavior of aromatic polyimides by rigid‐body pendulum rheometer

“…[2][3][4][5]20 To clearly analyze the thermal imidization temperature area, both precursors ODPA-TDA-PAA and ODPA-SDA-PAA were coated into films and vacuum-treated at 1208C for 8 h to remove the solvent before TGA test, which minimizes that THERMAL IMIDIZATION BEHAVIOR OF AROMATIC POLYIMIDESthe appearance of thermal imidization temperature areas was overlapped and interfered with the large extent of solvent evaporation in the thermogravimetric analysis. Figure 4 shows the thermogravimetric analysis of ODPA-TDA-PI and ODPA-SDA-PI converted from PAA in the dynamic heating process.…”

“…Therefore, the dehydrated cyclization process will influence the final structure and properties of PI. [2][3][4][5] With regard to the new resin system, prior estimations of the processing conditions like curing time and temperature, reaction behavior, conversion degree, etc. are important factors in both research and actual manufacturing applications.…”

Preparation, Characterization, and Photo-induced Liquid Crystal Alignment of Polyimide and Poly(vinyl cinnamate) Blend Alignment Layer

“…The band at 1375 cm −1 is less influenced by overlap with other bands and thus it has often been selected for measurement of the degree of imidization, which means the percent imidization of the amic acid group. [23][24][25][26] To exclude the ef- fect of film thickness on absorbance, the band at 1500 cm −1 is usually selected as an internal standard. [23][24][25][26] The degree of imidization was determined by referencing A 1375 /A 1500 to the ratio obtained on a fully cured film obtained by the thermal imidization at 350 • C. The equation for calculating the percent degree of imidization is given below.…”

“…25) Table I lists the degree of imidization for the PI/PVCi blends of various blend ratios and imidization temperatures. Since the peak at 1375 cm −1 from the imide group is small and buried into those from PVCi below the PI content of 50 wt%, the rigorous determination of the degree of imidization was performed only for the PI content of 50 wt% and above.…”

“…With increasing imidization temperature, the degree of imidization for the blends increases irrespective of the blend ratio, which is the typical behavior for the thermal imidization of PAA. [23][24][25][26] A comparison of the degree of imidization for blends of different blend ratios shows that the degree of imidization increases with increasing PVCi content at 180 and 200 • C. This behavior is possibly explained in terms of the plasticizing effect of PVCi upon the thermal imidization of PAA. The imidization reaction requires a certain mobility of the amic acid group to form a favorable conformation for its transformation into imide, and thus the increase of chain mobility due to the presence of a plasticizer, such as residual solvent, is effective for increasing the degree of imidization.…”