Patent Publication Number: US-2005119147-A1

Title: Detergent composition and detergent for liquid crystal cell

Description:
INCORPORATION BY REFERENCE  
      The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2003-400334 filed on Nov. 28, 2003. The content of the application is incorporated herein by reference in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a detergent, and more particularly, to a detergent suitable for cleaning of liquid crystal cells and the like in a liquid crystal cell production process.  
      2. Description of the Related Art  
      Liquid crystal cells are usually produced in the following manner. Specifically, a pair of glass substrates, on which electrodes and alignment layers are formed, are laminated to each other, and liquid crystal is injected between the substrates and sealed with a sealant. Thereafter, the liquid crystal attached to the gap between the glass substrates is cleaned and removed, and deflection plates are attached to the glass substrates. The liquid crystal is removed by this cleaning process in order to prevent occurrence of various troubles, due to residue of the liquid crystal functioning as a mold release agent, in subsequent processes such as peeling-off of the deflection plate, misconnection of driver terminals, failure of a driver/underfill interface, and peeling off of a strippable film used in a thinning method of substrates.  
      In general, liquid crystal molecules, which are polarized compounds, are known to be difficult to disperse or dissolve in a water system because of its strong intermolecular interaction and its strong hydrophobic property. Thus, for the cleaning and removal of the liquid crystal attached to liquid crystal cells, the use of a detergent to which an ionic activator, an ionic builder, an ionic emulsifier or the like is added has been brought to the mainstream. As such a detergent, for example, a detergent containing a chelating agent and an alkaline substance (Patent Document 1) and a detergent containing salt made from ammonium cation and phosphate anion and the like (Patent Document 2) are cited. Moreover, a combination of a chelating agent made from a concentrated catechin solution and a surfactant, a combination of an ethylenediamine chelating agent, a surfactant and sulfonate, and the like are also used.  
      [Patent Document 1] 
      Japanese Patent Laid-Open No. Hei 3(1991)-070800  
      [Patent Document 2] 
      Japanese Patent Laid-Open No. 2000-313899  
      Incidentally, the detergent heretofore used to clean and remove the liquid crystal attached to liquid crystal cells contains an ionic substance and also a hygroscopic substance as one of its components. Thus, when a part of such a detergent remains in a terminal portion of the liquid crystal cell, there is a problem in that ion migration or even electromigration during driving of liquid crystal due to absorbed water often occurs.  
      Moreover, instead of the ionic substance, a halogen solvent and certain nonpolar or polar solvents such as tetrahydrofuran or acetone are conceivable. However, these solvents have problems in terms of a flash point, safety, environmental issues, necessity of explosion-proof specifications, or the like. Consequently, in practice, it is difficult to use the solvents described above.  
     SUMMARY OF THE INVENTION  
      As described above, the present invention was made to solve the technical problems of the detergent for liquid crystal cells, which had been previously used to clean and remove the liquid crystal attached to the liquid crystal cells.  
      Specifically, an object of the present invention is to provide a low-corrosive and nonionic detergent composition with high detergent properties.  
      Moreover, another object of the present invention is to provide a low-cost and highly safe detergent for liquid crystal cells, which has an excellent ability to clean and remove liquid crystal attached to liquid crystal cells.  
      In order to achieve the foregoing object, a detergent composition according to an implementation of the present invention contains (a) 20 wt % to 60 wt % of polyoxyalkylene styryl phenyl ether and (b) 40 wt % to 80 wt % of polyoxyalkylene alkyl ether (where the sum of (a) and (b) is 100 wt %).  
      Particularly, the detergent composition having the foregoing configuration according to an implementation of the present invention, has high solubility for the liquid crystal and is nonionic. Thus, the problem caused by the ion migration or the electromigration during driving of liquid crystal due to absorbed water is resolved.  
      It is preferable that a weight ratio of the two components contained in the detergent composition according to an implementation of the present invention is (a) 30 wt % to 50 wt % of polyoxyalkylene styryl phenyl ether to (b) 50 wt % to 70 wt % of polyoxyalkylene alkyl ether.  
      Here, polyoxyalkylene styryl phenyl ether that is the component (a) can be easily obtained by use of a heretofore known synthesis method, if the component is characterized by being a polyalkylene oxide adduct of styrenated phenol. Particularly, it is preferable that (a) polyoxyalkylene styryl phenyl ether is an addition polymer of styrenated phenol and alkylene oxide of 2 to 4 carbon atoms. In this event, it is preferable that (a) polyoxyalkylene styryl phenyl ether is an addition polymer of 1 mol of styrenated phenol and 4 to 5 mol of alkylene oxide having 2 to 4 carbon atoms. In such a manner, by setting the added amount of alkylene oxide to about 4 to 5 mol, the molecular polarity of polyoxyalkylene styryl phenyl ether is weakened. Meanwhile, the solubility for the liquid crystal can be improved.  
      Moreover, as to styrenated phenol, there normally exist monostyrenated phenol, distyrenated phenol and tristyrenated phenol. If styrenated phenol is characterized in that purity of monostyrenated phenol in styrenated phenol is 85% or more, influence of the ion migration or the electromigration during driving of liquid crystal due to absorbed water can be significantly reduced. Among those described above, it is preferable that (a) polyoxyalkylene styryl phenyl ether is an addition polymer of 1 mol of monostyrenated phenol and 5 mol of ethylene oxide.  
      Moreover, if polyoxyalkylene alkyl ether that is the component (b) has a straight or branched chain alkyl group of 4 to 18 carbon atoms, solubility of the detergent composition according to an implementation of the present invention in water can be dramatically improved. Thus, a water-based detergent which can be used in the form of a water dispersion can be prepared.  
      Here, as to (b) polyoxyalkylene alkyl ether, it is preferable that the number of added moles of alkylene oxide having 2 to 4 carbon atoms is 1 to 10. Particularly, it is preferable that the number of added moles of alkylene oxide having 2 or 3 carbon atoms is 6. Furthermore, it is preferable that (b) polyoxyalkylene alkyl ether has a isodecyl group.  
      An implementation of the present invention can also be a detergent for liquid crystal cells, containing a mixture of (a) 20 wt % to 60 wt % of polyoxyalkylene styryl phenyl ether and (b) 40 wt % to 80 wt % of polyoxyalkylene alkyl ether (where the sum of (a) and (b) is 100 wt %) and (c) 100 g to 1000 g of water for 1 g of the mixture having such a composition ratio as described above. Accordingly, an implementation of the present invention is a detergent for liquid crystal cells, which has an excellent ability to clean and remove the liquid crystal attached to liquid crystal cells.  
      Here, it is preferable that the (c) water is ion-exchanged water.  
      The detergent for liquid crystal cells, according to an implementation of the present invention contains no ionic components. Moreover, when used in the form of about 0.1 wt % of dilute water dispersion, the detergent for liquid crystal cells has an excellent ability to completely dissolve 5 g of liquid crystal per liter of solution. Moreover, the liquid crystal having been cleaned and removed from liquid crystal cells is not reattached to liquid crystal cells and maintains its stable dispersion state in the detergent solution. Accordingly, the liquid crystal can be completely removed by washing.  
      As described above, according to an implementation of the present invention, a low-corrosive and nonionic detergent with high detergent properties is provided.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The best mode for carrying out the present invention (hereinafter referred to as an embodiment of the invention) will be described in detail below.  
      (a) polyoxyalkylene styryl phenyl ether used in a detergent composition to which this embodiment is applied is obtained as a polyalkylene oxide adduct of styrenated phenol.  
      Here, a synthesis method for styrenated phenol is not particularly limited and heretofore known methods can be used. For example, styrenated phenol can be produced by Friedel-Crafts reaction between phenols and styrenes. As the phenols, for example, phenol, alkylphenol, arylphenol and aralkyl phenol are cited. As alkylphenol, for example, cresol, butylphenol, octyl phenol and the like are cited. As arylphenol, for example, phenylphenol, biphenylphenol, naphthyl phenol and the like are cited. As aralkyl phenol, for example, benzylphenol, phenylethylphenol and the like are cited. Among those described above, phenol, cresol and phenylphenol are preferable.  
      Moreover, as the styrenes, for example, styrene, α-methyl styrene and vinyltoluene are cited. Among those described above, styrene is preferable.  
      Reaction conditions of Friedel-Crafts reaction are not particularly limited. For example, Friedel-Crafts reaction can be performed by allowing phenols and styrenes to react with each other at a temperature from 110 to 140 degrees C. in the presence of a catalyst.  
      Note that, regarding styrenated phenol, normally, monostyrenated phenol, distyrenated phenol and tristyrenated phenol exist as ones obtained by adding styrenes to benzene nuclei of phenols. Among those described above, monostyrenated phenol obtained by adding 1 mol of styrenes to benzene nuclei of phenols is preferable. Moreover, a concentration of monostyrenated phenol in styrenated phenol is normally 85% or more, preferably 90% or more, and more preferably 98% or more.  
      The polyalkylene oxide adduct of styrenated phenol can be produced by addition reaction of alkylene oxide with styrenated phenol. As alkylene oxide, alkylene oxide of 2 to 4 carbon atoms is preferable. Among alkylene oxides, ethylene oxide of 2 carbon atoms and propylene oxide of 3 carbon atoms are preferable. Particularly, ethylene oxide is preferable. From the viewpoint of solubility for liquid crystal, the number of added moles of alkylene oxide is normally 1 to 10 mol, preferably 2 to 6 mol, and more preferably 4 to 5 mol. Among those described above, the most preferable is an adduct of 1 mol of monostyrenated phenol and 5 mol of ethylene oxide. Conditions of the addition reaction are not particularly limited. For example, the addition reaction can be performed at a temperature from 100 to 190 degrees C.  
      As a preferable aspect of (a) polyoxyalkylene styryl phenyl ether used in the detergent composition to which this embodiment is applied, one having a structure expressed by the following general formula (1) is cited.  
                 
 
      Here, in formula (1), R 1  is a straight or branched chain alkylene group of 2 to 4 carbon atoms, n is the number of added moles (1 to 3) of styryl groups, and m is the number of added moles (1 to 10) of oxyalkylene groups.  
      Next, (b) polyoxyalkylene alkyl ether used in the detergent composition to which this embodiment is applied can be obtained as an alkylene oxide adduct of a higher alcohol. As the higher alcohol, alcohol having a straight or branched chain alkyl group of 4 to 18 carbon atoms is cited. To be more specific, 2-ethylhexanol, octanol, decanol, lauryl alcohol, isodecyl alcohol, tridecyl alcohol, myristyl alcohol, stearyl alcohol, oleyl alcohol, octylphenol, nonylphenol, dodecylphenol and the like are cited. Among those described above, isodecyl alcohol is preferable.  
      As alkylene oxide, alkylene oxide of 2 to 4 carbon atoms is preferable. Among alkylene oxides, ethylene oxide of 2 carbon atoms and propylene oxide of 3 carbon atoms are preferable. Particularly, ethylene oxide is preferable. Moreover, one having a block structure of ethylene oxide and propylene oxide can also be used. From the viewpoint of water-solubility and solubility for liquid crystal, the number of added moles of alkylene oxide is normally 1 to 10 mol, preferably 5 to 7 mol, and more preferably 6 mol.  
      As a preferable aspect of (b) polyoxyalkylene alkyl ether used in the detergent composition to which this embodiment is applied, one having a structure expressed by the following general formula (2) is cited. 
 
R 2 —O—(R 3 O) 1 H   (2) 
 
      Here, in formula (2), R 2  is a straight or branched chain alkyl group of 4 to 18 carbon atoms, R 3  is a straight or branched chain alkylene group of 2 to 4 carbon atoms, and 1 is the number of added moles (1 to 10) of oxyalkylene groups.  
      Among (b) polyoxyalkylene alkyl ethers expressed by the general formula (2), polyoxyethylene isodecyl ether having 6 mol of ethylene oxide added thereto is particularly preferable.  
      The detergent composition to which this embodiment is applied contains 20 wt % to 60 wt %, preferably 30 wt % to 50 wt %, of polyoxyalkylene styryl phenyl ether that is the component (a) and 40 wt % to 80 wt %, preferably 50 wt % to 70 wt %, of polyoxyalkylene alkyl ether that is the component (b) (where the sum of (a) and (b) is 100 wt %). A method for mixing the components (a) and (b) is not particularly limited, and a normal mixing method can be used.  
      As the detergent composition to which this embodiment is applied, a mixture of the components (a) and (b) can be used as it is, or, if desired, the mixture can be used after being prepared in the form of water dispersion. When the mixture is used in the form of water dispersion, a composition ratio of the respective components in the water dispersion is not particularly limited. Normally, the detergent composition contains 100 g to 1000 g of water, as the component (c), for 1 g of the mixture of polyoxyalkylene styryl phenyl ether that is the component (a) and polyoxyalkylene alkyl ether that is the component (b). Here, as the water that is the component (c), it is preferable that ion-exchanged water is used.  
      Such a detergent composition prepared in the form of dilute water dispersion can be used, particularly, as a detergent for liquid crystal cells, which has an excellent ability to clean and remove liquid crystal attached to liquid crystal cells. A method for cleaning and removing the liquid crystal attached to liquid crystal cells by use of such a detergent for liquid crystal cells is not particularly limited, but can be selected accordingly. For example, heretofore known means can be used, such as immersion cleaning, oscillating cleaning, cleaning utilizing rotation such as spinner cleaning, paddle cleaning, spray-in-air or spray in liquid cleaning and ultrasonic cleaning. Such cleaning means may be employed solely, or a combination of a plurality of such cleaning means may be employed. Moreover, liquid crystal cells may be cleaned one by one or a plurality of liquid crystal cells may be cleaned in one cleaning operation. Furthermore, one or a plurality of washing tanks may be used in the cleaning. A temperature of the detergent composition during the cleaning is not particularly limited. However, in terms of safety and workability, it is preferable that the temperature is within a range from 20 degrees C. to 60 degrees C.  
      Note that, according to need, the detergent composition to which this embodiment is applied can be combined with another nonionic surfactant. As a nonionic surfactant, for example, one or more of a polyalkylene polyamine polyalkylene oxide adduct, a polyhydric alcohol fatty acid ester, a polyhydric alcohol fatty acid ester polyalkylene oxide adduct and a benzylated phenol polyalkylene oxide adduct is cited. 
    
    
     EXAMPLES  
      This embodiment will be more specifically described below by use of examples. However, this embodiment is not limited to the following examples unless the examples depart from the scope of the embodiment.  
     Examples 1 to 4 and Comparative Examples 1 and 2  
      JIS comb-teeth electrode 2-type electrode plate is made an object to be cleaned and liquid crystal (fluorine liquid crystal: TM9701LA made by Merck Ltd.) is evenly applied thereto. Thus, an evaluation substrate is obtained. Next, detergents ((1) to (4)) having compositions and concentrations shown in Table 1 are prepared, and evaluation substrates having the liquid crystal applied thereto are immersed and agitated in solutions of the detergents for 2 minutes at 40 degrees C. Thereafter, the substrates are washed with running water for 1 minute and dried for 30 minutes in a clean oven (80 degrees C.).  
      Subsequently, a sine wave with a frequency of 100 Hz is applied to the dried electrodes, a phase difference (tan θ) between an alternating current and an alternating electric field is measured as an amount of dielectric loss, and effects of the detergent compositions remaining on the evaluation substrates are evaluated. In a region of frequency of 100 Hz or less, dielectric loss occurs due to surface polarization of absorbed water and free water, and ions become mobile ions, thus becoming a factor causing acceleration of migration. The smaller the value of the amount of dielectric loss is, the smaller the effects of detergent compositions remaining on the evaluation substrates are, and the more excellent as a detergent for liquid crystal cells the detergent is.  
      Note that, for comparison, as to ethylenediamine detergent (detergent A: LGL made by Yokohama Oils &amp; Fats Industry Co., Ltd.) and catechin detergent (detergent B: Natural Sweeper made by Ito En Ltd.), amounts of dielectric loss are measured under the same conditions as those described above. Table 1 shows the results.  
                           TABLE 1                                          comparative           example   example                                             1   2   3   4   1   2                                                 detergent   (1)   (2)   (3)   (4)   A (*5)   B (*6)       component   MSP (*1)   MSP   DSP (*2)   DSP   —   —       (a)       component   SD (*3)   SDX (*4)   SDX   SD   —   —       (b)       weight ratio   1:2   1:2   1:2   1:2   —   —       (a):(b)       solvent   ion-   ion-   ion-   ion-   —   ion-           exchanged   exchanged   exchanged   exchanged       exchanged           water   water   water   water       water       concentration   0.5   0.5   0.5   0.5   50   50       (wt %)       dielectric   0.0035   0.0051   0.0051   0.0065   0.0025   0.0075       loss (tan θ)       dry       dielectric   0.0055   0.0065   0.0075   0.0131   0.0055   0.0585       loss (tan θ)       wet (*7)                 (*1) polyoxyethylene monostyryl phenyl ether (added amount of ethylene oxide: 5 mol)            (*2) polyoxyethylene distyryl phenyl ether (added amount of ethylene oxide: 5 mol)            (*3) polyoxyethylene isodecyl ether (added amount of ethylene oxide: 6 mol)            (*4) polyoxyalkylene isodecyl ether (added amount of alkylene oxide: 8 mol)            (*5) ethylenediamine detergent (LGL: made by Yokohama Oils &amp; Fats Industry Co., Ltd.)            (*6) catechin detergent (Natural Sweeper: made by Ito En Ltd.)            (*7) room temperature, 95% humidity             
 
      From the results shown in Table 1, the detergents (Examples 1 to 4) which are prepared in the form of water dispersions with a concentration of 0.5 wt % by mixing polyoxyethylene styryl phenyl ether (component (a)) and polyoxyalkylene isodecyl ether (component (b)) at a weight ratio (a):(b)=1:2 have small measured values of the dielectric loss (tan θ) both in a dry state (dry) and a wet state (wet). Thus, it is found out that the detergents have an excellent ability as a low-cost and safe detergent for liquid crystal cells.  
      Among the detergents described above, the detergent (1) (Example 1) prepared by mixing polyoxyethylene monostyryl phenyl ether (added amount of ethylene oxide: 5 mol) and polyoxyethylene isodecyl ether (added amount of ethylene oxide: 6 mol) at a weight ratio of 1:2 has a small measured value of the dielectric loss (tan θ). Thus, it is found out that, as to the detergent (1), effects on the electrode formed on the evaluation substrate are especially small.  
      Meanwhile, although the ethylenediamine detergent (detergent A: Comparative Example 1) has small effects on the electrode on the evaluation substrate, the detergent needs to be used in a high concentration state in order to remove the liquid crystal attached to the electrode. Thus, it is found out that its cost is extremely high as a detergent. Moreover, the catechin detergent (detergent B: Comparative Example 2) has a large measured value of the dielectric loss (tan θ), and the migration is accelerated, particularly, in the wet state (wet). Thus, it is found out that the effects on the electrode are large.  
     Example 5 and Comparative Examples 3 and 4  
      The liquid crystal attached to an evaluation substrate is cleaned and removed under the same conditions as those of Example 1 by use of the detergent (1) used in Example 1, and fragment ions due to liquid crystal residue on the electrode are measured by use of TOF-SIMS. Note that, for comparison, as to the detergent A used in Comparative Example 1 and the detergent B used in Comparative Example 2, after the same operation as that of Example 1 is performed, fragment ions due to the liquid crystal residue on the electrode are measured by use of the TOF-SIMS. Table 2 shows the results.  
                               TABLE 2                                       comparative   comparative           example 5   example 3   example 4                                                    detergent   detergent (1)   detergent A   detergent B       anion (mass)       F (19)   41226   99130   207728       COF 3  (85)   294   270   4081       C 6 H 2 OF 3  (147)   423   2319   16262       LC (167)   21   27   265       LC (251)   41   63   731       LC (279)   27   180   859       LC (295)   22   36   156       LC (363)   17   27   139       LC (381)   23   27   345       LC (409)   16   67   357       total count number   1000000   1000000   1000000                  
 
      From the results shown in Table 2, the detergent (1) (Example 5) which is prepared by mixing polyoxyethylene monostyryl phenyl ether (added amount of ethylene oxide: 5 mol) and polyoxyethylene isodecyl ether (added amount of ethylene oxide: 6 mol) at a weight ratio of 1:2 has a small amount of fragment ions measured by use of the TOF-SIMS. Thus, it is found out the amount of the liquid crystal residue on the electrode is small and the detergent ( 1 ) has an excellent detergency as a detergent for liquid crystal cells.  
      Meanwhile, as to the detergent A (Comparative Example 3) and the detergent B (Comparative Example 4), it is found out that the amounts of the liquid crystal residue on electrodes are large, and particularly the detergent B has the liquid crystal residue about 5 times that of the detergent ( 1 ).  
      Note that, as utilization examples of the present invention, the detergent of the present invention can be applied, for example, as detergents for various oils such as a cutting oil attached to precision parts, a press oil and a drawing oil, and smears of wax, grease and the like.