Method for producing reflective layer and reflective layer

Abstract

Provided is a method for producing a reflective layer having excellent diffuse reflectivity. The method for producing a reflective layer of the present invention includes Step 1 of applying a composition containing a liquid crystal compound and a chiral agent onto a substrate and heating the applied composition to align the liquid crystal compound into a cholesteric liquid crystalline phase state, and Step 2 of forming a reflective layer by cooling or heating the composition so that the helical twisting power of the chiral agent contained in the composition in the cholesteric liquid crystalline phase state increases by 5% or more.

What is claimed is: 
     
         1 . A method for producing a reflective layer, comprising:
 Step 1 of applying a composition containing a liquid crystal compound and a chiral agent onto a substrate and heating the applied composition to align the liquid crystal compound into a cholesteric liquid crystalline phase state; and   Step 2 of forming a reflective layer by cooling or heating the composition so that the helical twisting power of the chiral agent contained in the composition in the cholesteric liquid crystalline phase state increases by 5% or more.   
     
     
         2 . The method for producing a reflective layer according to  claim 1 , wherein the composition is cooled or heated in Step 2 so that the helical twisting power of the chiral agent increases by 10% or more. 
     
     
         3 . The method for producing a reflective layer according to  claim 1 , wherein the composition is cooled or heated in Step 2 so that, in a cross section of a coating layer formed in Step 1, a bright portion and a dark portion derived from the cholesteric liquid crystalline phase are changed into a state not parallel to the substrate. 
     
     
         4 . The method for producing a reflective layer according to  claim 3 , wherein the composition is cooled or heated in Step 2 so that, in the cross section of the coating layer formed in Step 1, the bright portion and the dark portion derived from the cholesteric liquid crystalline phase are wave-like. 
     
     
         5 . The method for producing a reflective layer according to  claim 1 , wherein the liquid crystal compound is a liquid crystal compound having a polymerizable group,
 the composition is subjected to a curing treatment to form a reflective layer obtained by immobilizing a cholesteric liquid crystalline phase in Step 2, and   the method further comprises Step 3 of subjecting the composition to a curing treatment to form a reflective layer obtained by immobilizing a cholesteric liquid crystalline phase, after Step 2.   
     
     
         6 . The method for producing a reflective layer according to  claim 5 , wherein the immobilization of the cholesteric liquid crystalline phase in Step 2 or the immobilization of the cholesteric liquid crystalline phase in Step 3 is to immobilize the structure after cooling or heating the composition. 
     
     
         7 . The method for producing a reflective layer according to  claim 5 , wherein the immobilization of the cholesteric liquid crystalline phase in Step 2 or the immobilization of the cholesteric liquid crystalline phase in Step 3 is carried out by a polymerization reaction with light irradiation. 
     
     
         8 . The method for producing a reflective layer according to  claim 7 , wherein the polymerization reaction with light irradiation is a radical polymerization reaction. 
     
     
         9 . The method for producing a reflective layer according to  claim 1 , wherein the composition is cooled or heated in Step 2 so that the helical twisting power of the chiral agent increases by 12% or more. 
     
     
         10 . The method for producing a reflective layer according to  claim 1 , wherein the composition is cooled in Step 2 so that the temperature of the composition decreases by 30° C. or higher. 
     
     
         11 . The method for producing a reflective layer according to  claim 1 , wherein the composition applied onto the substrate has a film thickness of 0.1 to 20 μm. 
     
     
         12 . The method for producing a reflective layer according to  claim 1 , wherein the composition is cooled or heated in Step 2 so that the helical twisting power of the chiral agent is 20 or more. 
     
     
         13 . The method for producing a reflective layer according to  claim 1 , wherein one or more of the compounds constituting the composition have a plurality of polymerizable groups and the total content of the compound having the plurality of polymerizable groups in the composition is 80% by mass or more based on the total solid content in the composition. 
     
     
         14 . The method for producing a reflective layer according to  claim 1 , wherein the composition containing a liquid crystal compound and a chiral agent further contains an alignment control agent. 
     
     
         15 . The method for producing a reflective layer according to  claim 1 , wherein the composition is cooled in Step 2 at a cooling rate at which a maximum value is 1° C. or higher per second.