JP4887610B2 - Processing method of liquid crystal material - Google Patents

Description

  The present invention relates to a processing method for reusing a liquid crystal material contained in a liquid crystal panel used in a defective panel discharged in a liquid crystal panel manufacturing process or a liquid crystal display element discarded in the market.

  Liquid crystal display elements are used for various purposes as an interface between a person and a computer, and their production and usage in the market are rapidly increasing. Along with this, generation of used liquid crystal display elements corresponding to the production volume of liquid crystal display elements is expected. Since the liquid crystal display element is composed of a member different from a conventional display device such as a CRT, the liquid crystal display element needs to be discarded by a method different from the conventional method. Also, with the recent increase in environmental awareness, a disposal method that does not place a burden on the environment and a method that actively reuses a member that can be reused by reducing the amount to be discarded as much as possible are being studied.

  As a method of processing a usable member from a waste liquid crystal panel into a reusable state, a processing method characterized by performing a purification step, a physical property measurement step, and a physical property value adjustment step after recovering the liquid crystal material is disclosed. (Patent Document 1), and the liquid crystal composition can be reused by the method described in the cited document.

  On the other hand, in the liquid crystal material for active matrix, the voltage holding ratio needs to be a sufficiently high value. The voltage holding ratio is one of the performance indicators of the liquid crystal material, and it indicates how excellent it is as a dielectric material constituting the capacitor. When the liquid crystal material is recovered, the voltage holding ratio deteriorates, but unless this is recovered, the display quality deteriorates and cannot be put into practical use. In particular, since the recovered liquid crystal composition contains an extremely large amount of components including impurities, it is not easy to increase the voltage holding ratio. Furthermore, the components in the recovered liquid crystal include not only impurities but also various liquid crystal materials. Examination of which substances in the component are actively recovered and which components lead to efficient recovery. Is insufficient, and there is a problem that the voltage holding ratio which is an important characteristic parameter may not be sufficiently recovered.

JP2004-137467

  An object of the present invention is to provide a processing method for sufficiently recovering the voltage holding ratio of a liquid crystal material in a processing method for reusing a liquid crystal material taken out from a liquid crystal panel.

  As a result of intensive studies to solve the above problems, it has been found that a purification step for removing a compound having a cyano group and an ester compound from the recovered liquid crystal material may be introduced. That is, the present invention provides a processing method for reusing a liquid crystal material taken out from a liquid crystal panel, wherein the ester compound and the compound having a cyano group contained in the liquid crystal material are removed. .

  In general, in an active matrix liquid crystal material, it is preferable not to use a compound having an ester bond in order to ensure a high voltage holding ratio. Moreover, in order to ensure a high voltage holding ratio as a polar group for imparting dielectric anisotropy, a cyano group is not used but a fluorine atom, a trifluoromethyl group, a trifluoromethoxy group, or the like is used. It is preferable. That is, a compound having a cyano group or an ester compound is not suitable for a liquid crystal material for an active matrix from the viewpoint of voltage holding ratio. However, due to the demands for high-speed response, low drive voltage, wide liquid crystal temperature range, adjustment of birefringence, etc. required for active matrix materials, some active matrix materials to which ester compounds have been added in the range of several to 20% have become practical It is the actual situation. With this amount of addition, the voltage holding ratio does not deteriorate. In some cases, a compound having several percent of a cyano group is added. Therefore, the recovered liquid crystal material necessarily includes a compound having a cyano group and an ester compound.

  As described above, even if a cyano group-containing compound or an ester compound is contained, if the content is small, the influence on the retention is substantially small. However, in the liquid crystal material collected from the liquid crystal panel, when an ester compound or a compound having a cyano group is contained in the order of several to 20%, it is compared with a material not containing an ester compound or a compound having a cyano group. Our study revealed that the effect of improving the voltage holding ratio by refining was extremely inferior. In other words, a recovered liquid crystal material that does not contain an ester compound or a compound having a cyano group can recover the voltage holding ratio to a practically sufficient level by purification, but a recovery that contains an ester compound or a compound having a cyano group. It was clarified that the liquid crystal material cannot recover the voltage holding ratio to a practically sufficient level even if the same purification treatment is performed.

  The voltage holding ratio of the liquid crystal material taken out from the liquid crystal panel can be reliably restored to a practically sufficient level.

  The method of the present invention enables reuse of a liquid crystal material from an active matrix liquid crystal material to which an ester compound or a compound having a cyano group is intentionally added. In addition, liquid crystal panels are not strictly separated due to economic reasons or human error, and TN (twisted nematic) liquid crystal or STN (super twisted nematic) liquid crystal material having an ester compound or cyano group is mixed. The liquid crystal material can be reused from the liquid crystal material for the matrix, which is effective in reducing the environmental burden due to the discarded liquid crystal display element.

  An example of the present invention will be described below. The compound having a cyano group which is preferably removed from the recovered liquid crystal material is represented by the general formula (I)

(Wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and the alkyl group or the alkenyl group is unsubstituted or has 1 or 2 substituents. Can have more than one F, Cl, CN, CH ₃ or CF ₃ , and one or more CH ₂ groups present in the alkyl group or the alkenyl group have O atoms directly bonded to each other As an alternative, it may be substituted with O, CO or COO, and A and B are each independently 1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4. -Phenylene group, 2,3-difluoro-1,4-phenylene group, 3,5-difluoro-1,4-phenylene group, 2-chloro-1,4-phenylene group, 3-chloro-1,4-phenylene Group, 2,3-dichloro B-1,4-phenylene group, 3,5-dichloro-1,4-phenylene group, pyrimidine-2,5-diyl group, pyridine-2,5-diyl group, trans-1,4-cyclohexylene, Trans-1,4-cyclohexenylene, trans-1,3-dioxane-2,5-diyl group, trans-1-sila-1,4-cyclohexylene, trans-4-sila-1,4-cyclohexylene , Naphthalene-2,6-diyl group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, phenanthrene-2,7-diyl group or fluorene- Represents a 2,7-diyl group, and the naphthalene-2,6-diyl group and the 1,2,3,4-tetrahydronaphthalene-2,6-diyl group are unsubstituted or a single substituent or More than five F, _Cl, can have a CF 3, OCF ₃ or CH _3, i is 0, 1 or 2, ^{Y 1} and ^{Y 2} are each independently a single bond, -COO -, - OCO _{-, - CH 2 O -,} - OCH 2 -, - CH = CH -, - CF = CF -, - C≡C -, - (CH 2) 2 -, - (CH 2) 4 -, - CH = CH— (CH ₂ ) ₂ —, — (CH ₂ ) ₂ —, —CH═CH—, —CH═N—, —CH═N—N═CH— or —N (O) ═N— Z ¹ and Z ² each independently represent H, F, or Cl.) A compound represented by phenanthrene can be exemplified. Among such materials, it is preferable to remove a compound represented by the following general formula (a-1) or general formula (a-2).

(In the formula, each R independently represents an alkyl group having 1 to 7 carbon atoms.)
Further, as an ester compound which is preferably removed from the recovered liquid crystal material, the general formula (II)

Wherein R ² and R ³ each independently represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and the alkyl group or the alkenyl group is unsubstituted or It may have one or more F, Cl, CN, CH ₃ or CF ₃ as substituents, and one or more CH ₂ groups present in the alkyl group or the alkenyl group are As O atoms are not directly bonded to each other, they may be substituted with O, CO or COO,
C, D and E are each independently 1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4-phenylene group, 2,3-difluoro-1,4-phenylene group 3,5-difluoro-1,4-phenylene group, 2-chloro-1,4-phenylene group, 3-chloro-1,4-phenylene group, 2,3-dichloro-1,4-phenylene group, 3 , 5-dichloro-1,4-phenylene group, pyrimidine-2,5-diyl group, pyridine-2,5-diyl group, trans-1,4-cyclohexylene, trans-1,4-cyclohexenylene, Trans-1,3-dioxane-2,5-diyl group, trans-1-sila-1,4-cyclohexylene, trans-4-sila-1,4-cyclohexylene, naphthalene-2,6-diyl group, 1, 2, 3 Represents 4-tetrahydronaphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, phenanthrene-2,7-diyl group or fluorene-2,7-diyl group, naphthalene-2,6-diyl Group and 1,2,3,4-tetrahydronaphthalene-2,6-diyl group are unsubstituted or have one or more F, Cl, CF ₃ , OCF ₃ or CH ₃ as substituents It is possible,
j represents 0, 1 or 2, and Y ³ and Y ⁴ each independently represent a single bond, —COO—, —OCO—, —CH ₂ O—, —OCH ₂ —, —CH═CH—, —CF _{= CF -, - C≡C -,} - (CH 2) 2 -, - (CH 2) 4 -, - CH = CH- (CH 2) 2 -, - (CH 2) 2 -, - CH = CH -, - CH = N -, - CH = N-N = CH- or -N (O) = N- to represent, at least one of ^{Y 3} and ^{Y 4} -COO-, or an -OCO- . ) Can be exemplified. Among such materials, it is preferable to remove a compound represented by the following general formula (b-1) to general formula (b-6).

(In the formula, R and R ′ each independently represents an alkyl group having 1 to 7 carbon atoms.)
The means for removing the ester compound or the compound having a cyano group is not particularly limited as long as the influence of other liquid crystal materials is small and these compounds can be removed, but the use of column chromatography is effective.

  By using column chromatography, a compound having a cyano group or an ester compound can be separated and removed according to the difference in polarity. Examples of the filler used for column chromatography include silica gel and alumina. The filler mainly includes a normal phase system and a reverse phase system, and the normal phase system is preferable as the treatment method of the present invention. The filler is preferably used in a mass of 5 to 200 times the mass of the recovered liquid crystal. If the amount of the filler is reduced to 5 times or less, the working time can be reduced, but the separation ability is lowered, and it becomes difficult to accurately remove the compound having a cyano group or the ester compound. When a filler having a mass of 200 times or more is used, a compound having a cyano group or an ester compound can be accurately separated and removed, but there is a problem that the working time becomes long. As the effluent solvent, hexane, heptane, octane, decane, dodecane, toluene, xylene, ethylbenzene, isopropylbenzene and the like are preferable, and low polarity hydrocarbon solvents such as hexane, heptane, octane, decane and dodecane are particularly preferable. If hydrolysis is used, removal by column chromatography can be performed efficiently. The polarity of the compound can be changed by hydrolyzing the compound having a cyano group to an amide compound or a carboxylic acid compound, and in the case of an ester compound, by hydrolyzing the compound to a carboxylic acid compound and a hydroxy compound. . As conditions for the hydrolysis, it is necessary to set conditions under which other compounds constituting the active liquid crystal material other than the compound having a cyano group or the ester compound are not decomposed or the decomposition is minimized. As the solvent for the hydrolysis, a protic solvent such as water or alcohol or a mixture thereof is preferable, and these solvents and aprotic organic solvents can be used in combination. Examples of the catalyst include acid catalysts such as sulfuric acid, hydrochloric acid, phosphoric acid, and paratoluenesulfonic acid, and basic catalysts such as sodium hydroxide, potassium hydroxide, sodium alkoxide, potassium alkoxide, diazabicycloundecene, and hydrazine. it can. The reaction temperature is preferably set between room temperature and 100 ° C. Hydrolysates of compounds having cyano groups and ester compounds generally have higher polarity than compounds having active matrix liquid crystal materials other than compounds having cyano groups and ester compounds. Easy to remove.

  The hydrolyzate can be removed not only by column chromatography but also by alkaline aqueous solution washing. For example, when the hydrolyzate is mixed with an aqueous alkaline solution, the hydrolyzate is largely transferred to the aqueous layer, so that the hydrolyzate can be removed. By collecting the components that have not been transferred to the aqueous layer, it is possible to obtain a material from which the hydrolyzate has been removed. Of course, it is possible to improve the efficiency and accuracy of separation / removal by washing with an alkaline aqueous solution after hydrolysis and further performing column chromatography. When using column chromatography for such a purpose, it is preferable to use a mass of 0.5 to 50 times as much as the mass of the recovered liquid crystal as the filler.

EXAMPLES Hereinafter, although an Example is given and this invention is further explained in full detail, this invention is not limited to these Examples. Further, “%” in the compositions of the following examples and comparative examples means “mass%”. The voltage holding ratio was measured using “VHR-1A” manufactured by Toyo Corporation, with a frame period of 200 milliseconds, a pulse width of 64 microseconds, and an applied voltage of 5V. The ion density was measured using “MTR-1” manufactured by Toyo Corporation and with a triangular wave of ± 20 V (frequency 0.5 Hz). Both the voltage holding ratio and the ion density were measured using a glass cell having a polyimide alignment film and an electrode area of 1 cm ² and a cell gap of 6 μm.
(Reference Example 1) Recovery of liquid crystal material A display panel was taken out from an active matrix liquid crystal display that was circulated in the city, and the display panel was crushed to about 1 cm square with a hammer. 20 kg of this pulverized product was washed with 4000 ml of acetone three times. The acetone washing liquid (12,000 ml in total) was distilled off under reduced pressure to obtain 20 g of recovered liquid crystal (A). The recovered liquid crystal (A) was slightly colored in red, the nematic liquid crystal-isotropic liquid phase transition temperature (TNI) was 96 ° C., the birefringence was 0.083, and the dielectric anisotropy was +4.2. . The voltage holding ratio at 80 ° C. was 4%. The ion density was not measurable because the ion density was too high. Further, the recovered liquid crystal contained compounds of the following formulas (e-1) to (e-60).

(Example 1) Purification of recovered liquid crystal (A) (removal of ester compound)
It was found that the recovered liquid crystal (A) recovered in Reference Example 1 contained an ester compound represented by formula (e-49), formula (e-51), and formula (e-53). When the recovered liquid crystal was subjected to thin layer chromatography (eluent: hexane), three spots were roughly divided into Rf values of 0.46, 0.55, and 0.69. An ester compound is contained in a spot having an Rf value of 0.55. By purifying 3g of recovered liquid crystal by column chromatography using 300g of silica gel (eluent: hexane) and removing the fraction with Rf value of 0.55, the formulas (e-49) and (e-51) The ester compound of formula (e-53) was removed. The liquid crystal material obtained by the removal was 2.2 g. Further, TNI was 95 ° C., birefringence was 0.0850, and dielectric anisotropy was 4.4. The voltage holding ratio at 80 ° C. was 97.6%, and the ion density was 14 pC / cm ² .
(Comparative Example 1) Purification of recovered liquid crystal (A) (ester is not removed)
13.7 g of the recovered liquid crystal collected in Reference Example 1 was subjected to removal of the origin component and removal of the colored component by column chromatography (flowing solvent: hexane) using 41 g of silica gel (the ester component was not removed). ). The obtained liquid crystal material was 12.3 g. The TNI was 92 ° C., the birefringence was 0.0890, and the dielectric anisotropy was 4.5. The voltage holding ratio at 80 ° C. was 95.0%, and the ion density was 53 pC / cm ² .
(Reference Example 2) Collection of liquid crystal material A display panel was taken out from an active matrix liquid crystal display for monitoring that was circulated in the market, and the display panel was crushed to about 1 cm square with a hammer. 1 kg of this pulverized product was washed with 200 ml of acetone three times. The acetone washing liquid (total 600 ml) was distilled off under reduced pressure to obtain 1.1 g of recovered liquid crystal (B). The recovered liquid crystal (B) was slightly purple, and the nematic liquid crystal-isotropic liquid phase transition temperature was 70 ° C. Further, the recovered liquid crystal contained compounds of the following formulas (f-1) to (f-13).

(Example 2) Purification of recovered liquid crystal (B) (removal of compound having cyano group and ester compound)
In the recovered liquid crystal (B) recovered in Reference Example 2, the compounds having a cyano group of formula (f-1) and formula (f-4), and the ester compound of formula (f-10) and formula (f-11) are It was found that it was contained. The recovered liquid crystal 0.7 g was purified by column chromatography (flowing solvent: hexane) using 70 g of silica gel to remove the compound having a cyano group and the ester compound. The liquid crystal material obtained by the removal was 0.2 g. The TNI was 88 ° C., the birefringence was 0.0776, and the dielectric anisotropy was 5.6. The voltage holding ratio at 60 ° C. was 97.1%, and the ion density was 44 pC / cm ² .
(Comparative Example 2) Purification of recovered liquid crystal (A) (the compound having a cyano group and the ester compound are not removed)
0.3 g of the recovered liquid crystal collected in Reference Example 2 was subjected to removal of the origin component and removal of the colored component by column chromatography (elution solvent: hexane) using 0.9 g of silica gel (a compound having a cyano group, an ester). Compound removal was not performed). The obtained liquid crystal material was 0.2 g. TNI was 70 ° C., birefringence was 0.0767, and dielectric anisotropy was 8.6. The voltage holding ratio at 60 ° C. was 87.0%, and the ion density was 300 pC / cm ² .

From the above examples and comparative examples, it can be seen that a practically sufficient voltage holding ratio can be obtained by using the processing method of the present invention.

Claims (5)

A processing method for reusing a liquid crystal material taken out from a liquid crystal panel, wherein the liquid crystal compound and / or ester liquid crystal compound having a cyano group contained in the liquid crystal material is removed. The processing method according to claim 1, wherein the means for removing the liquid crystal compound and / or the ester liquid crystal compound having a cyano group is a column chromatography step. The processing method of Claim 1 or 2 with which the removal means of the liquid crystal compound and / or ester liquid crystal compound which has a cyano group has a hydrolysis process of the compound and / or ester compound which have a cyano group. Liquid crystal compounds having a cyano group are represented by the general formula (I)

(Wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and the alkyl group or the alkenyl group is unsubstituted or has 1 or 2 substituents. Can have more than one F, Cl, CN, CH ₃ or CF ₃ , and one or more CH ₂ groups present in the alkyl group or the alkenyl group have O atoms directly bonded to each other As an alternative, it may be substituted with O, CO or COO, and A and B are each independently 1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4. -Phenylene group, 2,3-difluoro-1,4-phenylene group, 3,5-difluoro-1,4-phenylene group, 2-chloro-1,4-phenylene group, 3-chloro-1,4-phenylene Group, 2,3-dichloro B-1,4-phenylene group, 3,5-dichloro-1,4-phenylene group, pyrimidine-2,5-diyl group, pyridine-2,5-diyl group, trans-1,4-cyclohexylene, Trans-1,4-cyclohexenylene, trans-1,3-dioxane-2,5-diyl group, trans-1-sila-1,4-cyclohexylene, trans-4-sila-1,4-cyclohexylene , Naphthalene-2,6-diyl group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, phenanthrene-2,7-diyl group or fluorene- Represents a 2,7-diyl group, and the naphthalene-2,6-diyl group and the 1,2,3,4-tetrahydronaphthalene-2,6-diyl group are unsubstituted or a single substituent or More than five F, _Cl, can have a CF 3, OCF ₃ or CH _3, i is 0, 1 or 2, ^{Y 1} and ^{Y 2} are each independently a single bond, -COO -, - OCO _{-, - CH 2 O -,} - OCH 2 -, - CH = CH -, - CF = CF -, - C≡C -, - (CH 2) 2 -, - (CH 2) 4 -, - CH = CH— (CH ₂ ) ₂ —, — (CH ₂ ) ₂ —, —CH═CH—, —CH═N—, —CH═N—N═CH— or —N (O) ═N— The processing method according to claim ^1, wherein Z ¹ and Z ² each independently represent H, F, or Cl. Ester liquid crystal compounds are represented by the general formula (II)

Wherein R ² and R ³ each independently represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and the alkyl group or the alkenyl group is unsubstituted or It may have one or more F, Cl, CN, CH ₃ or CF ₃ as substituents, and one or more CH ₂ groups present in the alkyl group or the alkenyl group are As O atoms are not directly bonded to each other, they may be substituted with O, CO or COO,
C, D and E are each independently 1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4-phenylene group, 2,3-difluoro-1,4-phenylene group 3,5-difluoro-1,4-phenylene group, 2-chloro-1,4-phenylene group, 3-chloro-1,4-phenylene group, 2,3-dichloro-1,4-phenylene group, 3 , 5-dichloro-1,4-phenylene group, pyrimidine-2,5-diyl group, pyridine-2,5-diyl group, trans-1,4-cyclohexylene, trans-1,4-cyclohexenylene, Trans-1,3-dioxane-2,5-diyl group, trans-1-sila-1,4-cyclohexylene, trans-4-sila-1,4-cyclohexylene, naphthalene-2,6-diyl group, 1, 2, 3 Represents 4-tetrahydronaphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, phenanthrene-2,7-diyl group or fluorene-2,7-diyl group, naphthalene-2,6-diyl Group and 1,2,3,4-tetrahydronaphthalene-2,6-diyl group are unsubstituted or have one or more F, Cl, CF ₃ , OCF ₃ or CH ₃ as substituents It is possible,
j represents 0, 1 or 2, and Y ³ and Y ⁴ each independently represent a single bond, —COO—, —OCO—, —CH ₂ O—, —OCH ₂ —, —CH═CH—, —CF _{= CF -, - C≡C -,} - (CH 2) 2 -, - (CH 2) 4 -, - CH = CH- (CH 2) 2 -, - (CH 2) 2 -, - CH = CH -, - CH = N -, - CH = N-N = CH- or -N (O) = N- to represent, at least one of ^{Y 3} and ^{Y 4} -COO-, or an -OCO- . The processing method in any one of Claim 1 to 4 represented by this.