JP4940531B2 - Treatment method for reusing liquid crystal materials - Google Patents

Description

  The present invention relates to a processing method for reusing a liquid crystal material used 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.

A liquid crystal display element is used for various purposes as an interface between a person and a computer, and its production amount and usage amount in the market are rapidly increasing.
With the recent increase in environmental awareness, disposal methods that do not burden the environment and reuse methods are being studied.

  However, the liquid crystal material contained in the liquid crystal panel is a small amount of about 1 g even for a large display such as a liquid crystal display element for computers. In addition, the liquid crystal material is sandwiched between glasses coated with an organic film such as an alignment film on the inner surface, and is sealed with a sealing material such as an epoxy resin, so that it can be taken out without introducing impurities so that it can be reused efficiently. It has been difficult to develop economical processing methods that can be used again.

  Among the disposal methods for waste liquid crystal panels, methods for recovering and reusing liquid crystal materials have been proposed. The liquid crystal materials can be recovered by washing the liquid crystal from the panel with an organic solvent such as acetone or isopropyl alcohol, or scraping the liquid crystal. A processing method for reusing a liquid crystal material capable of adjusting the recovered liquid crystal component by adding and mixing the low molecular weight compound removed in the recovery step to the liquid crystal whose component has been changed by the recovery is disclosed. (See Patent Documents 1, 2, and 3).

  However, the liquid crystal material obtained by the method disclosed in the above-mentioned literature has a very low purity, and the physical property value is distorted by the recovery. Therefore, it is difficult to reuse the liquid crystal material as it is.

  Moreover, although the method (refer patent document 4) which collect | recovers liquid crystal materials using a supercritical fluid, the method (refer patent document 5) etc. which collect | recover using hot water are also disclosed, Many physical property values need to be readjusted, and such a processing technique has not yet been established.

JP 2001-305501 A (page 3, paragraph numbers 0017 and 0018) JP 2001-305502 A (page 3, paragraph numbers 0014 and 0015) JP 2001-337305 A (page 3, paragraph numbers 0020 and 0021) JP 2002-126688 A (page 2, paragraph number 0010) JP 2002-166259 A (page 2)

  The subject of this invention is providing the processing method for collect | recovering and reusing the liquid crystal material which has the purity and physical-property value which can be again used for a liquid crystal panel from a used liquid crystal panel.

  In order to solve the above problems, the inventors of the present application have examined the processing steps for taking out the liquid crystal material from the liquid crystal panel and reusing it, resulting in the following invention.

That is, the present invention
1) a step of taking out the liquid crystal material from the liquid crystal panel, 2) a step of purifying the taken out liquid crystal material, 3) a step of measuring physical properties of the purified liquid crystal material, and 4) a step of adjusting physical properties of the liquid crystal material. A processing method for reusing a liquid crystal material characterized by comprising:

  By simply taking out the liquid crystal material from the liquid crystal panel, impurities from the components of the liquid crystal panel and ionic impurities are mixed in, so the next step is a purification step to remove these as much as possible as the second step is necessary. In the subsequent step, it is necessary to compare the degree of purification and what components have been removed by the applied treatment and purification before and after purification. At this time, it is necessary to measure the minimum physical property value of the liquid crystal material in order to be finally reused for the liquid crystal panel. The recovered liquid crystal material can be reused by adjusting and combining the liquid crystal property values obtained in this step with the minimum physical property values required for reuse.

  The treatment process of the present invention makes it possible to recover a reusable liquid crystal material from a used liquid crystal panel, which has been considered difficult.

Hereinafter, each step of the present invention will be described in detail.
(1) Step of taking out liquid crystal material from liquid crystal panel (a) Cutting panel The two glass substrates enclosing the liquid crystal material are bonded by a sealing material. When the panel is cut, the inside of the sealing material is cut, and the sealing material is not included in the open system including the two glasses obtained by the cutting and the liquid crystal material sandwiched between them. The sealing material is usually composed of an epoxy resin or an acrylate resin, but it is important to prevent the liquid crystal material from containing resin waste generated by cutting the sealing material. The mixing of the resin material into the liquid crystal material can be removed by filtering the liquid crystal material. However, when the liquid crystal material comes into contact with the resin waste, the curing agent, additive, and the like contained in the resin are extracted into the liquid crystal, and the purity of the liquid crystal is lowered. In particular, an ionic impurity causes a display defect when the liquid crystal material is reused, so that contact between the sealing material and the liquid crystal must be avoided.

(B) Taking out the liquid crystal material from the two sheets of glass (b-1) Method using an organic solvent By dissolving the liquid crystal material with an organic solvent, the liquid crystal material can be washed out between the two glass substrates. . From the organic solvent solution of the liquid crystal material thus obtained, the organic solvent is distilled off using a method such as distillation to obtain a liquid crystal material.
Usually, an organic film such as polyimide or an inorganic film such as SiO ₂ is formed on the inner surfaces of two glass substrates. As described above, when flowing out with an organic solvent, it is required to dissolve and wash the liquid crystal with as little organic solvent as possible while minimizing the mixing of impurities from these organic and inorganic films.
(Organic solvent)
From this viewpoint, the organic solvent is preferably a hydrocarbon solvent with low polarity such as hexane or toluene. Alcohol solvents such as methanol, ethanol, and isopropanol, and solvents such as acetone and methyl ethyl ketone are highly polar and have a drawback that they are particularly highly soluble in ionic impurities. Therefore, if the recovery operation is performed with a highly polar solvent, impurities are eluted from the organic film or the inorganic film, which is not preferable because the impurity content in the solution of the liquid crystal material to be recovered increases.
In addition, an alcohol-based solvent is not preferable as an extraction solvent because it has a low specific resistance and contains a large amount of moisture and ionic impurities in the solvent, resulting in a decrease in resistance of the liquid crystal material taken out from the liquid crystal panel. Further, since the alcohol solvent is not highly soluble in the liquid crystal material, the use of the alcohol solvent may cause precipitation in the liquid crystal material, which is not preferable.
Hydrocarbon solvents such as hexane and toluene are difficult to extract polar polymer components and oligomer components from organic and inorganic films and sealing materials. Further, the specific resistance of the solvent itself is preferably as high as about 10 ¹⁴ Ω · cm.

(B-2) Method by Blow As a method for taking out the liquid crystal material from the two pieces of glass, a method of taking out the liquid crystal material from the two pieces of glass by blowing (blowing) gas without using a solvent is useful. is there.
As the gas to be blown, air can be used, but in order to suppress oxidative deterioration of the liquid crystal material, it is preferable to use an inert gas such as nitrogen gas or argon gas.

The following methods can be used as the blowing method.
A. Method of recovering liquid crystal material by separating two glass substrates in advance and blowing gas to the liquid crystal material adhering to each glass substrate. B. Method of blowing gas between two glass substrates A method of efficiently removing liquid crystal material by removing the two substrates and utilizing the action of liquid crystal gathering in the direction of peeling both substrates due to surface tension, and adding a gas blow to this. It has the characteristic that the efficiency of the blow is good because it separates. However, it is preferable to blow an inert gas because oxidation deterioration due to contact with air is likely to occur.
Although the method B is short in contact with air and is less susceptible to oxidative degradation, it is efficient because the liquid crystal material sandwiched in a gap of several μm between the two substrates must be blown with strength that surpasses the surface tension. bad.
The method C is more preferable in that it is difficult to cause oxidative deterioration and recovery efficiency, and it is particularly preferable to use an inert gas in combination.

(Blowing method)
In order to minimize the contamination of impurities from the organic film and the inorganic film with which the liquid crystal material is in contact and to recover the liquid crystal material efficiently, the panel is tilted and the liquid crystal material is collected in one direction by blowing. A method of collecting the liquid crystal material in one direction like an air brush by blowing gas linearly from the tip of the blow nozzle is preferable.
In the method of physically scraping with a spatula or the like, it is inevitable to physically rub the organic film and the inorganic film, so it is difficult to avoid contamination of impurities from these films.

(B-3) Method Using Centrifugal Force Further, as a method not using a solvent, a method using centrifugal force can be mentioned. As described above, the two glass substrates are separated, and the liquid crystal material is attached on the glass substrate, and then placed in a centrifuge, and the liquid crystal material is separated from the substrate by centrifugal force. It is preferable to install the glass substrate so that the centrifugal force works efficiently for the separation of the liquid crystal material from the glass substrate. Further, it is preferable to provide a liquid crystal material receiver so that the separated liquid crystal material can be efficiently recovered.
The panel applicable by the recovery method of the present invention is not particularly limited as long as it is a liquid crystal panel, but in the case of a very small panel, since the recovery amount is small, it is preferably applied to a panel having a diagonal of 140 mm or more. It is more preferable to apply to a panel of 200 mm or more.

(2) Step of purifying the taken-out liquid crystal material (a) Purification by distillation As described above, an organic film and an inorganic film formed on a sealing material or a glass substrate as a constituent member of a liquid crystal panel in which the liquid crystal material is sealed Since low molecular compounds and high molecular compounds contained as impurities are mixed into the liquid crystal material from the film, it is necessary to remove them from the liquid crystal material. In the case where there is a difference between the boiling point of the liquid crystal material and the boiling point of impurities, distillation is useful for removing impurities, and distillation performed at a pressure lower than atmospheric pressure is more preferable.
(Molecular distillation)
Molecular distillation is a distillation method performed by placing a condenser within a distance shorter than the mean free path of molecules evaporated from a heating surface under a high vacuum (10 ⁻¹ Pa or less). In this method, distillation can be performed without applying a high temperature to the liquid crystal material, and a liquid crystal material having a relatively high boiling point can be purified. In this case, it is preferable to be performed under a pressure of 10 ⁻¹ to 10 ⁻² Pa in order to reduce the temperature load on the liquid crystal material and increase the recovery rate of the low molecular liquid crystal material.
In addition, short-stage distillation in which a condenser is disposed within a slightly longer distance than the mean free process of molecules at a pressure slightly higher than molecular distillation (10 ⁻¹ Pa or higher) is also useful. This method is inferior in terms of temperature load as compared with molecular distillation, but is preferred when the distillation efficiency is high and the amount of treatment is large.

(B) Purification by adsorbent The liquid crystal material taken out from the liquid crystal panel contains ionic impurities. These ionic impurities include those extracted from the organic film and the inorganic film on the sealing material, which is a liquid crystal panel constituent member, and the glass substrate as described above, in addition to those generated by the deterioration of the liquid crystal material itself. Generally, these ionic impurities adsorb ionic compounds, and the ionic compounds can be separated and removed from the liquid crystal material by treating with an adsorbent that does not adsorb the liquid crystal material so much. For this purpose, an adsorbing material selected from alumina, silica gel, silica aluminas, zeolites and ion exchange resins is preferred, and alumina, silica gel and silica aluminas are more preferred. These adsorbents can be used by mixing different kinds of adsorbents. As a method for determining separation of ionic impurities, an analytical method using ion chromatography or the like, or a liquid crystal material after purification can be evaluated by specific resistance, current value, and ion density measurement described later.
Examples of the method for treating the liquid crystal material with the adsorbent include a method of using the adsorbent as column chromatography, a method of adding it directly to the liquid crystal material, and a method of adding the adsorbent after dissolving it in a solvent. In order to increase the adsorption efficiency, a method of increasing the contact efficiency between the ionic impurity and the adsorbent by means of stirring or the like by adding the adsorbent into a solution state by dissolving the liquid crystal material in a solvent. After purification of the liquid crystal material, it is preferable to separate and remove the adsorbent by filtration using a membrane filter or the like in order to completely remove the adsorbent.

(3) Step of measuring physical properties of purified liquid crystal material The liquid crystal material taken out from the liquid crystal panel by the method described above and obtained through the purification step is different from the composition when injected into the liquid crystal panel. In addition, it is necessary to grasp the characteristics of the recovered liquid crystal material regardless of whether the recovered liquid crystal material is reused in the same application as the extracted application or used in another application. . Various physical properties can be given as the evaluation physical properties of the liquid crystal material, but it is preferable to measure the following physical property values and grasp the values when reused. The important physical properties of the liquid crystal material for reuse are the nematic liquid crystal phase-isotropic phase transition temperature, refractive index anisotropy, dielectric anisotropy, spontaneous pitch and specific resistance of the liquid crystal material. The specific resistance value can be replaced by a current value, ion density measurement, and retention rate measurement.
(Nematic liquid crystal phase-isotropic phase transition temperature)
When a liquid crystal material is used for a liquid crystal panel, it is necessary to exhibit a nematic liquid crystal phase at the upper limit of the use temperature at which the liquid crystal panel is used. Therefore, the nematic liquid crystal phase-isotropic phase transition temperature (Tni) of the recovered liquid crystal material is required. Measurements that identify) are important. For the measurement of Tni, a method that is usually measured can be used. That is, the method by visual measurement with a polarizing microscope and the method by DCS measurement can be mentioned.
When purification is performed by distillation, the low molecular weight compound in the liquid crystal material may be partially removed by distillation or the high molecular weight compound may be partially removed without being distilled. In particular, the measurement of Tni is important.

(Refractive index anisotropy)
When a liquid crystal material is used for a liquid crystal panel, the product of the distance between the two substrates constituting the panel and the refractive index anisotropy (Δn) of the liquid crystal material used is essential for the optical design of the liquid crystal panel. Due to the physical properties, measurements that identify the recovered Δn are important. The measurement can use the method currently measured normally. That is, a method using an Abbe refractometer and a method using a micro refractometer can be mentioned.

(Dielectric anisotropy)
When a liquid crystal material is used for a liquid crystal panel, the liquid crystal material is driven with a driving voltage and is an essential physical property in electro-optical design whether or not sufficient contrast can be obtained. Measurements that specify directionality (Δε) are important.
In the purification process using the adsorbent described above, a highly polar compound in the liquid crystal material may be partially adsorbed and removed. Therefore, when the adsorbent is used in the purification process, Δε is measured particularly. is important.
Δε can be replaced by injecting the liquid crystal into a standard liquid crystal panel, measuring the voltage-transmittance characteristics, and checking the threshold voltage and saturation voltage.

(Spontaneous pitch)
Usually, an optically active compound is added to a liquid crystal material used for a liquid crystal panel in order to develop a twisted structure, and a spontaneous pitch (P; μm) is imparted to the liquid crystal material. When the spontaneous pitch is small, alignment defects occur, and electro-optical characteristics such as designed contrast and response speed are not satisfied, which is an essential physical property. The measurement can be performed using a wedge-shaped cell.
When the purification method by distillation or the purification method by adsorption is performed, a part of the high molecular weight optically active compound is lost from the distillate or is selectively adsorbed on the adsorbent, so that the amount added is the original amount. Measurements that identify the spontaneous pitch of the recovered liquid crystal material are important because they can be less than the amount added.

(Specific resistance, current value, ion density and voltage holding ratio measurement)
The liquid crystal material is required to have a high specific resistance value when it is driven by an active element as well as when driven by a passive element. However, the recovered liquid crystal material contains ionic impurities as described above, and is often reduced to about 1/100 of the specific resistance injected into the liquid crystal panel. The influence of ionic impurities can be evaluated by measuring the current value, ion density and voltage holding ratio in addition to the specific resistance measurement.

(4) Step of adjusting the physical property value of the liquid crystal material The physical property value of the liquid crystal material used for the liquid crystal panel can be adjusted by mixing the liquid crystal compound which is a constituent component thereof.
(Adjustment of nematic liquid crystal phase-isotropic phase transition temperature (Tni))
In the purification process, when the initial Tni changes due to distillation or adsorbent, it is useful to newly add a liquid crystal compound for adjustment. Since Tni almost satisfies the addition law when mixing the compound and the composition, the ratio of the material to be added can be calculated by the following equation.
Formula (A):

所望の液晶材料のＴｎｉ（℃）：Ｔｒ
添加する化合物のＴｎｉ（℃）：Ｔｘ
精製後の液晶材料のＴｎｉ（℃）：Ｔｃ
添加する化合物の組成比（％）：Ｘ

Tni (° C.) of desired liquid crystal material: Tr
Tni (° C.) of the compound to be added: Tx
Tni (° C.) of liquid crystal material after purification: Tc
Composition ratio (%) of compound to be added: X

For example, when Tni = 90 ° C. of the desired liquid crystal material, Tni = 85 ° C. of the purified liquid crystal material, and Tni 177 ° C. of the liquid crystal compound (P) to be added, the respective values are expressed in the formula (A). By substituting, the ratio of the compound to be added can be calculated.
That is, if the liquid crystal compound (P) is added at a ratio of 94.6% of purified liquid crystal material and 5.4% of liquid crystal compound (P), a liquid crystal material of Tni = 90 ° C. can be obtained. The difference between the calculated value and the actually measured value by this method is usually within 1 to 2 ° C.
When the above mixing was actually performed, a liquid crystal material of 90.4 ° C. was obtained.

  In ordinary purification, a compound having a large molecular weight such as a long molecular component is often smaller than the initial content rate due to the influence of adsorption or the like. For this reason, in order to adjust Tni, the tricyclic or tetracyclic compound represented by general formula (I) is preferable.

(式中、R¹及びR²は、それぞれ独立的にフッ素置換されていても良い炭素原子数1〜16のアルキル基、炭素原子数1〜16のアルコキシル基、炭素原子数2〜16のアルケニル基又は炭素原子数3〜16のアルケニルオキシ基を表し、A、B及びCは、それぞれ独立的に1,4-フェニレン基、2又は3-フルオロ-1,4-フェニレン基、2,3-ジフルオロ-1,4-フェニレン基、3,5-ジフルオロ-1,4-フェニレン基、2又は3-クロロ-1,4-フェニレン基、2,3-ジクロロ-1,4-フェニレン基、3,5-ジクロロ-1,4-フェニレン基、2-メチル-1,4-フェニレン基、3-メチル-1,4-フェニレン基、ナフタレン-2,6-ジイル基、フェナントレン-2,7-ジイル基、フルオレン-2,7-ジイル基、トランス-1,4-シクロヘキシレン基、1,2,3,4-テトラヒドロナフタレン-2,6-ジイル基、デカヒドロナフタレン-2,6-ジイル基、トランス-1,3-ジオキサン-2,5-ジイル基、ピリジン-2,5-ジイル基、ピリミジン-2,5-ジイル基、ピラジン-2,5-ジイル基またはピリダジン-2,5-ジイル基を表し、これらの基は更に1〜3のフッ素原子により置換されていてもよく、mは1又は2を表し、Z¹及びZ²はそれぞれ独立的に単結合、-CH₂CH₂-、-(CH₂)₄-、-OCH₂-、-CH₂O-、-COO-、-CH=CH-、-CF=CF-、-CH=N-N=CH-又は-C≡C-を表す。但し、mが2の場合、2個のZ²及びCは、それぞれ独立に同じであっても良く、異なっていても良い。)
これらの液晶化合物のうち、他の特性に影響を及ぼしにくく、効率的に調整できるためには、Ｔｎｉが１２０℃〜３００℃の化合物が好ましい。Ｔｎｉが１２０℃より小さい化合物では、調整のため添加量を多くする必要があるため、他の特性に影響を及ぼしたり、溶解度が不足して析出が生じる可能性があるため好ましくない。また、３００℃より高い化合物では、添加量が少なくなるため、調整誤差が大きく、効率的な調整には好ましくない。

(In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 16 carbon atoms, an alkoxyl group having 1 to 16 carbon atoms, and an alkenyl having 2 to 16 carbon atoms which may be fluorine-substituted. Represents a group or an alkenyloxy group having 3 to 16 carbon atoms, and A, B and C are each independently 1,4-phenylene group, 2 or 3-fluoro-1,4-phenylene group, 2,3- Difluoro-1,4-phenylene group, 3,5-difluoro-1,4-phenylene group, 2 or 3-chloro-1,4-phenylene group, 2,3-dichloro-1,4-phenylene group, 3, 5-dichloro-1,4-phenylene group, 2-methyl-1,4-phenylene group, 3-methyl-1,4-phenylene group, naphthalene-2,6-diyl group, phenanthrene-2,7-diyl group Fluorene-2,7-diyl group, trans-1,4-cyclohexylene group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, trans 1,3-dioxane- 2,5-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, pyrazine-2,5-diyl group or pyridazine-2,5-diyl group, Optionally substituted by 1 to 3 fluorine atoms, m represents 1 or 2, Z ¹ and Z ² are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, -OCH _2- , -CH ₂ O-, -COO-, -CH = CH-, -CF = CF-, -CH = NN = CH- or -C≡C-, provided that m is 2. The two Z ² and C may be the same or different from each other.)
Among these liquid crystal compounds, a compound having a Tni of 120 ° C. to 300 ° C. is preferable in order to hardly affect other characteristics and to adjust efficiently. A compound having a Tni of less than 120 ° C. is not preferable because the addition amount needs to be increased for adjustment, which may affect other characteristics and may cause precipitation due to insufficient solubility. In addition, a compound having a temperature higher than 300 ° C. is not preferable for an efficient adjustment because the addition amount is small and an adjustment error is large.

In the compound represented by the general formula (I), A, B and C are preferably 1,4-phenylene group or trans-1,4-cyclohexylene group. Furthermore, since the bicyclohexane compound in which both A and B are trans-1,4-cyclohexylene groups has a small Δn, a small Δε, and a high Tni, the effect of Δn and Δε on the liquid crystal material is small, and the Tni is adjusted. This is preferable.
R ¹ and R ² are preferably alkyl groups having 1 to 5 carbon atoms. Z ¹ and Z ² are preferably a single bond, —CH ₂ CH ₂ — or —COO—. A single bond is excellent in chemical stability, so that it is difficult to impair the chemical stability of the liquid crystal material when added. Further, -COO- is preferable because it has a high solubility, so that the amount added can be increased and precipitation is difficult to occur.
Moreover, in adjusting, it is also possible to adjust not only the liquid crystal compound but also a liquid crystal composition having Tni necessary for adjustment in the same manner.

(Adjustment of refractive index anisotropy (Δn))
The Δn of the liquid crystal material after purification is changed by the contribution of the compound lost by the purification. Similar to the adjustment of Tni, it can be adjusted by adding a liquid crystal compound anew according to the following formula (B), and can be adjusted to a desired Δn.
Formula (B):

所望の液晶材料のΔｎ：Ｎｒ
添加する化合物のΔｎ：Ｎｙ
精製後の液晶材料のΔｎ：Ｎｃ
添加する化合物の組成比（％）：Ｙ

Δn: Nr of desired liquid crystal material
Δn of compound to be added: Ny
Δn: Nc of liquid crystal material after purification
Composition ratio (%) of compound to be added: Y

In order to adjust efficiently by adding a small amount, a compound having a large Δn is useful. The range of Δn of the compound to be added is preferably 0.15 to 0.30. As these compounds, a compound having a biphenyl skeleton or a compound having a tolan skeleton is preferable.
Further, in the slight adjustment of Δn, a compound having a relatively small Δn is useful. Preferred examples of Δn include compounds having Δn of 0.03 to 0.07. As such a compound having Δn, a compound having a bicyclohexane skeleton is preferable because Δn is small and Tni is high.
Similarly to the adjustment of Tni, when adjusting Δn of the liquid crystal material after purification, not only the liquid crystal compound but also a liquid crystal composition having Tni necessary for the adjustment can be adjusted in the same manner.

(Adjustment of dielectric anisotropy (Δε))
A compound having a large Δε is one of compounds that are easily lost by purification. The Δε of the liquid crystal material after purification is changed by the contribution of the compound lost by the purification. Similarly to the adjustment of Tni, it can be adjusted by adding a liquid crystal compound anew according to the following formula (C), and can be adjusted to a desired Δε.

  Formula (C):

所望の液晶材料のΔε：Ｅｒ
添加する化合物のΔε：Ｅｚ
精製後の液晶材料のΔε：Ｅｃ
添加する化合物の組成比（％）：Ｚ

Δε of desired liquid crystal material: Er
Δε of compound to be added: Ez
Δε of liquid crystal material after purification: Ec
Composition ratio (%) of compound to be added: Z

In order to adjust efficiently by adding a small amount, a compound having a large Δε is useful. The range of Δε of the compound to be added is preferably 5 to 40. As these compounds, compounds having a cyano terminal group and compounds having an F terminal group are preferred. Since a compound having a cyano end group has a large Δε, it can be adjusted with a small amount of addition. On the other hand, a compound having an F terminal group has a small Δε, which is suitable for slight adjustment of Δε, and a compound having an F terminal group is less susceptible to contamination by ionic substances, etc., and thus has improved specific resistance by purification. Therefore, it is suitable as a liquid crystal material for adjustment. Particularly preferred are compounds having 3,4,5-trifluorobenzene. Suitable compounds having a large Δε used in the present invention include compounds represented by the general formula (II).

(式中、R³は、フッ素置換されていても良い炭素原子数1〜16のアルキル基、炭素原子数1〜16のアルコキシル基、炭素原子数2〜16のアルケニル基又は炭素原子数3〜16のアルケニルオキシ基を表し、D及びEは、それぞれ独立的に1,4-フェニレン基、2又は3-フルオロ-1,4-フェニレン基、2,3-ジフルオロ-1,4-フェニレン基、3,5-ジフルオロ-1,4-フェニレン基、2又は3-クロロ-1,4-フェニレン基、2,3-ジクロロ-1,4-フェニレン基、3,5-ジクロロ-1,4-フェニレン基、2-メチル-1,4-フェニレン基、3-メチル-1,4-フェニレン基、ナフタレン-2,6-ジイル基、フェナントレン-2,7-ジイル基、フルオレン-2,7-ジイル基、トランス-1,4-シクロヘキシレン基、1,2,3,4-テトラヒドロナフタレン-2,6-ジイル基、デカヒドロナフタレン-2,6-ジイル基、トランス-1,3-ジオキサン-2,5-ジイル基、ピリジン-2,5-ジイル基、ピリミジン-2,5-ジイル基、ピラジン-2,5-ジイル基又はピリダジン-2,5-ジイル基を表し、これらの基は更に1〜3のフッ素原子により置換されていてもよく、nは0、1又は2を表し、Z³及びZ⁴はそれぞれ独立的に単結合、-CH₂CH₂-、-(CH₂)₄-、-OCH₂-、-CH₂O-、-COO-、-CH=CH-、-CF=CF-、-CH=N-N=CH-又は-C≡C-を表し、Yはシアノ基、フッ素原子、塩素原子、トリフルオロメトキシ基、トリフルオロメチル基、ジフルオロメトキシ基、水素原子又は3,3,3-トリフルオロエトキシ基を表し、X¹、X²は水素原子、フッ素原子又は塩素原子を表す。但し、nが2の場合、2個のZ³及びEは、それぞれ独立に同じであっても良く、異なっていても良い。)
一般式(II)で表される化合物としては、D及びEが1,4-フェニレン基又はトランス-1,4-シクロヘキシレン基であることが好ましい。更に、D及びEが共にトランス-1,4-シクロヘキシレン基であるビシクロヘキサン化合物がΔｎが小さく、Ｔｎｉが高いため、液晶材料に対するΔｎやＴｎｉの影響が小さくΔεの調整を行うことができるため好ましい。

(In the formula, R ³ is an optionally substituted fluorine-substituted alkyl group having 1 to 16 carbon atoms, an alkoxyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, or 3 to 3 carbon atoms. 16 alkenyloxy groups, D and E are each independently 1,4-phenylene group, 2 or 3-fluoro-1,4-phenylene group, 2,3-difluoro-1,4-phenylene group, 3,5-difluoro-1,4-phenylene group, 2 or 3-chloro-1,4-phenylene group, 2,3-dichloro-1,4-phenylene group, 3,5-dichloro-1,4-phenylene Group, 2-methyl-1,4-phenylene group, 3-methyl-1,4-phenylene group, naphthalene-2,6-diyl group, phenanthrene-2,7-diyl group, fluorene-2,7-diyl group Trans-1,4-cyclohexylene group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, trans-1,3-dioxane-2, 5-diyl group, pyridine-2,5- Represents an yl group, pyrimidine-2,5-diyl group, pyrazine-2,5-diyl group or pyridazine-2,5-diyl group, and these groups may be further substituted by 1 to 3 fluorine atoms , N represents 0, 1 or 2, Z ³ and Z ⁴ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, -COO-, -CH = CH-, -CF = CF-, -CH = NN = CH- or -C≡C-, Y represents a cyano group, fluorine atom, chlorine atom, trifluoromethoxy group, trifluoro Represents a methyl group, a difluoromethoxy group, a hydrogen atom or a 3,3,3-trifluoroethoxy group, and X ¹ and X ² represent a hydrogen atom, a fluorine atom or a chlorine atom, provided that when n is 2, 2 Z ³ and E may be the same or different from each other.)
In the compound represented by the general formula (II), D and E are preferably a 1,4-phenylene group or a trans-1,4-cyclohexylene group. Furthermore, since the bicyclohexane compound in which both D and E are trans-1,4-cyclohexylene groups has a small Δn and a high Tni, the influence of Δn and Tni on the liquid crystal material is small and Δε can be adjusted. preferable.

R ³ is preferably an alkyl group having 1 to 5 carbon atoms. Z ³ and Z ⁴ are preferably a single bond, —CH ₂ CH ₂ —, or —COO—. Since single bonds and —CH ₂ CH ₂ — are excellent in chemical stability, it is difficult to impair the chemical stability of the liquid crystal material when added. Further, -COO- is preferable because it has a high solubility, so that the amount added can be increased and precipitation is difficult to occur.

At least one of X ¹ and X ² is preferably F, and more preferably a compound in which both are F. Y is preferably F or CN. F is preferable when importance is attached to chemical stability, and CN is preferable when Δε is largely adjusted. Specifically, a compound having a 3,4,5-trifluorophenyl group or a compound having a 4-cyano-3,5-difluorophenyl group is preferable.

Further, when adjusting, it is possible to adjust not only the liquid crystal compound but also a liquid crystal composition having Δε necessary for the adjustment in the same manner.
(Simultaneous adjustment of multiple physical properties)
When adjusting the nematic liquid crystal phase-isotropic phase transition temperature (Tni), the refractive index anisotropy (Δn), and the dielectric anisotropy (Δε) simultaneously, the equations (C), (D), and (E The ratio of the three kinds of materials to be added can be obtained by calculating X, Y and Z that simultaneously satisfy the three kinds of formulas represented by:
Formula (D):

式（Ｅ）：

Formula (E):

式（Ｆ）：

Formula (F):

Tni (° C.) of desired liquid crystal material: Tr
Δn: Nr of desired liquid crystal material
Δε of desired liquid crystal material: Er

Tni (° C.) of liquid crystal material after purification: Tc
Δn: Nc of liquid crystal material after purification
Δε of liquid crystal material after purification: Ec

Composition ratio (%) of compound added to adjust Tni: X
Compound Tni (° C.): Tx
Δn of compound to be added: Nx
Δε of compound to be added: Ex
Composition ratio (%) of compound added to adjust Δn: Y
Tni (° C.) of compound: Ty
Δn of compound to be added: Ny
Δε of compound to be added: Ey
Composition ratio (%) of compound added to adjust Δε: Z
Compound Tni (° C.): Tz
Δn of compound to be added: Nz
Δε of compound to be added: Ez
According to the value calculated as described above, the compound for adjustment is added, but it is not always necessary to achieve the target physical property value at once, and it can be performed in several steps. In that case, it is also preferable to use another compound in order to improve the low temperature storage property of a composition.

Moreover, when the target physical property value cannot be obtained at a time, the above-described measurement process and adjustment process can be repeated.
For the purpose of improving storage stability at low temperatures, the number of components can be increased in the same manner when it is desired to reduce the amount of the same material added.

(Spontaneous pitch)
A chiral compound can also be said to be one of the compounds that are easily lost by purification. Due to the loss of the chiral compound, the spontaneous pitch (p) of the purified liquid crystal material is increased (that is, increased). The value of the spontaneous pitch of the liquid crystal material depends on the threshold voltage and the stability of the alignment of the liquid crystal display element. It has a great effect on sex.
The spontaneous pitch of the liquid crystal material is expressed by the formula (G):

（式中、Cは光学活性化合物の添加量（質量％）を表し、ｐは自発ピッチ（μｍ）を表す。）で表されるように、添加するカイラル化合物のヘリカルツイスティングパワー：HTP （１／μｍ）と添加されたカイラル化合物の濃度(質量%)の積に反比例する。少量添加で調整するためには、ツイスティングパワーの大きいカイラル化合物が有効であるが、ツイスティングパワーが大き過ぎると微調整が困難なため、使用するカイラル化合物のツイスティングパワーは３〜３０（絶対値として表示）であることが好ましい。

(In the formula, C represents the addition amount (% by mass) of the optically active compound, and p represents the spontaneous pitch (μm).) Helical twisting power of the chiral compound to be added: HTP (1 / Μm) and the product of the concentration (mass%) of the added chiral compound. A chiral compound with a large twisting power is effective for adjusting with a small amount of addition, but if the twisting power is too large, fine adjustment is difficult, so the twisting power of the chiral compound to be used is 3 to 30 (absolutely (Displayed as a value).

  Note that the twisting power can be obtained as the reciprocal of the spontaneous pitch when 1% by mass of a chiral compound is added to the liquid crystal material. This value varies depending on the base material to be added. It is preferable to add 1% by mass to obtain a twisting power and then determine the amount of chiral compound added by proportional calculation.

  Preferred chiral compounds include the following compounds in addition to cholesterol derivatives such as cholesteryl nonanate.

(In each formula, R and R ′ are alkyl groups having 1 to 16 carbon atoms, alkoxyl groups having 1 to 16 carbon atoms, alkenyl groups having 2 to 16 carbon atoms, or alkenyloxy groups having 3 to 16 carbon atoms. Represents.)
According to the treatment method of the present invention, it is possible to recycle a liquid crystal composition having the same physical property values as the original liquid crystal material before recovery.

  It is also possible to recover a liquid crystal composition having physical property values different from those of the original liquid crystal composition. In other words, since the liquid crystal display is designed to have very fine characteristics, it cannot be completely recycled to the original liquid crystal composition in any case. In many cases, it is difficult to completely return the threshold voltage, such as frequency dependency, temperature dependency, and response. This difficulty largely depends on how much the liquid crystal material to be recycled is contaminated. In order to remove the contamination, it is necessary to carry out a number of steps of refining work, and the number of steps is long, and if it is long, the change in characteristics from the original liquid crystal composition becomes large.

  In such a case, it is preferable not to return to the liquid crystal composition having the original physical property values but to make adjustments in order to use the liquid crystal material with different required properties that can be reused.

EXAMPLES Hereinafter, although an Example is given and this invention is further explained in full detail, this invention is not limited to these Examples.
A liquid crystal material (A) was produced by a conventional method. The composition and physical properties of the liquid crystal material (A) are shown below.

Tni = 90 ° C
Δn = 0.095
Δε = 7.5
p = 85 μm
Specific resistance = 5.8 × 10 ¹² Ω · cm
200 90 ° TN liquid crystal displays having a display area of 20 cm square and a distance between two glass substrates of 10 μm were produced, and a liquid crystal material (A) was vacuum injected into the display.
The obtained liquid crystal display had a Vth of 1.69 V and a voltage holding ratio of 98%.
This display was left in a constant temperature bath at 80 ° C. for 500 hours.
(Process to remove liquid crystal material from liquid crystal panel)
Cutting is performed inside the sealing material bonding the two substrates to obtain a liquid crystal material sandwiched between the two glass substrates. The two substrates are slowly peeled off while paying attention not to mix impurities from the sealing material or the alignment film. Liquid crystal is collected in the liquid crystal reservoir A while nitrogen gas is blown over the liquid crystal material adhering to the substrate. When no more liquid crystal is collected, the substrate is washed away with n-hexane and the liquid crystal is collected in the liquid crystal reservoir B. This process was performed on 200 liquid crystal displays, and after removing n-hexane in the liquid crystal reservoir B by an evaporator, a recovered liquid crystal material was obtained. The recovered liquid crystal material obtained by distilling off the solvent and the liquid crystal material recovered from the liquid crystal reservoir A were combined to obtain 6 g of recovered liquid crystal material (R1).

(Process to purify the extracted liquid crystal material)
The gas chromatograms of the liquid crystal material recovered from the liquid crystal reservoir A and the liquid crystal material recovered from the liquid crystal reservoir B were measured. As a result, in the liquid crystal material recovered from the liquid crystal reservoir B, the peak content excluding the liquid crystal material recovered from the liquid crystal reservoir A was 1% or less, so that the liquid crystal material recovered from the liquid crystal reservoir B and the liquid crystal reservoir The collected liquid crystal materials were combined and proceeded to the following purification step (if it exceeded 1%, they were separately subjected to the following purification step). The specific resistance before purification of the obtained liquid crystal material was 6.8 × 10 ¹¹ Ω · cm.
The taken out liquid crystal material was purified by molecular distillation at a vacuum of 10 ⁻¹ Pa to obtain 5.2 g of recovered liquid crystal material (R2).
The recovered liquid crystal material (R2) was dissolved in n-hexane, washed twice with ion-exchanged water, and then purified by adsorption with 0.1% silica gel on the liquid crystal material.
Hexane was distilled off in the same manner as described above to obtain a recovered liquid crystal material (R3).

(Process for measuring physical properties of purified liquid crystal materials)
Tni, Δn, Δε and spontaneous pitch of the obtained recovered liquid crystal material (R3) were measured.
Tni = 88 ° C
Δn = 0.094
Δε = 7.0
p = 90 μm
Specific resistance = 4.6 × 10 ¹² Ω · cm
It can be seen that the specific resistance was improved by the refining process, and the specific resistance was sufficiently high for an active display. However, it can be seen that Tni decreases by 2 ° C., Δn decreases by 0.001, Δε decreases by 0.5, and p increases by 5 μm.

  In order to reuse the liquid crystal material, it is not always necessary to restore the original characteristics, but here, an attempt was made to reproduce the characteristics of the liquid crystal material (A) used in this experiment.

  Since Tni is lowered, formula (A-1)

（Ｔｎｉ＝１６８℃、Δｎ＝０．０９５、Δε＝０．８）で表される化合物を添加し、Δεが小さくなっているため、式（Ａ−２）

Since a compound represented by (Tni = 168 ° C., Δn = 0.095, Δε = 0.8) is added and Δε is small, the formula (A-2)

（Ｔｎｉ＝９４℃、Δｎ＝０．０９、Δε＝１２）で表される化合物を添加した。また、自発ピッチが伸びているため、カイラル化合物として、(III-1)において、RがC₆H₁₃O-であって、R'がC₆H₁₃の化合物である、式（Ａ−３）

A compound represented by (Tni = 94 ° C., Δn = 0.09, Δε = 12) was added. Further, since the spontaneous pitch is extended, as the chiral compound, in (III-1), R is C ₆ H ₁₃ O— and R ′ is a compound of C ₆ H _13. )

で表される化合物を添加した。

The compound represented by was added.

The addition amount of the compound represented by the formula (A-1) is X%, the addition amount of the compound represented by the formula (A-2) is Z%, and the liquid crystal material after the addition is Tni = 90 ° C., Δn = 0.095 and Δε = 7.5 were calculated using the above formulas (D) and (F).
Substituting this value into equation (D) yields the following equation:
(168-88) X + (94-88) Z = (90-88) * 100
80X + 6Z = 200
Subsequent substitution of values in equation (F) leads to the following equation:
(0.8-7) X + (12-7) Z = (7.5-7) × 100
-6.2X + 5Z = 50
By solving these simultaneous equations, X = 1.6% and Y = 11.8% are calculated.
The adjusted Δn at this time can be obtained by substituting a value into the equation (E).

Δn = (0.094 × 0.866) + (0.090 × 0.016) + (0.095 × 0.118) = 0.094

The addition amount of the compound represented by Formula (A-3) for spontaneous pitch adjustment was determined by the following method.
The helical twisting power (HTP) of the compound represented by the formula (A-3) in this liquid crystal material was measured by adding 1% by mass of the compound represented by the formula (A-3) to the purified matrix. HTP = 10.0 was obtained. From the above formula (G), the chiral compound concentration to be added: ΔC was obtained from 1 / 85−1 / 90 = 10ΔC, and ΔC = 0.01% was obtained.

  Based on the above calculated values, 86.6% of the purified liquid crystal material, 1.6% of the formula (A-1) and 11.8% of the formula (A-2) are mixed, and this mixture is 99.99%. 0.01% of the formula (A-3) was mixed to readjust the physical property values. When the physical properties of this liquid crystal composition were measured, Tni = 89.7 ° C., Δn = 0.095, Δε = 7.6, p = 84 μm were in good agreement with the calculated values, and desired reuse A possible recovered liquid crystal material was obtained.

The obtained recovered liquid crystal material was vacuum-injected into the original TN liquid crystal display, and the characteristics were measured. As a result, Vth = 1.67V and the voltage holding ratio were 98%. I was able to get it.

Claims (20)

1) a step of taking out the liquid crystal material from the liquid crystal panel, 2) a step of purifying the taken out liquid crystal material with an adsorbent, 3) a step of measuring physical properties of the purified liquid crystal material, and 4) physical properties of the liquid crystal material. A processing method for reusing a liquid crystal material, comprising the step of adjusting The processing method according to claim 1, wherein the step of taking out the liquid crystal material from the liquid crystal panel is a step of removing the liquid crystal material from the panel by dissolving the liquid crystal material with a hydrocarbon-based organic solvent and then distilling off the organic solvent. Step of taking a liquid crystal material from the liquid crystal panel, or either by blowing a gas processing method according to claim 1, wherein the step of taking out the by Ri liquid crystal material to a method of utilizing centrifugal force from the panel. The processing method as described in any one of Claims 1-3 which has the process refine | purified by molecular distillation in addition to the process refine | purified liquid crystal material with an adsorbent . The processing method according to claim 4, wherein the vacuum degree of molecular distillation is 10 ⁻¹ Pa to 10 ⁻² Pa. The step of purifying the liquid crystal material with an adsorbent is a step of using at least one selected from the group consisting of alumina, silica gel, silica aluminas, zeolite, and ion exchange resin. The processing method as described in. The step of measuring a physical property value of the liquid crystal material is a step of measuring at least one of a nematic liquid crystal phase-isotropic phase transition temperature, a refractive index anisotropy, a dielectric anisotropy, a spontaneous pitch, and a specific resistance of the liquid crystal material. The processing method as described in any one of Claims 1-6. The step of adjusting the physical property value of the liquid crystal material is a step of adding a liquid crystal compound or a liquid crystal composition having a nematic liquid crystal phase-isotropic phase transition temperature of 120 ° C. to 300 ° C. 8. The processing method as described in. The processing method according to claim 8, wherein the liquid crystal compound or composition having a nematic liquid crystal phase-isotropic phase transition temperature of 120 ° C. to 300 ° C. is a liquid crystal compound or composition having a bicyclohexylbenzene skeleton. The process according to any one of claims 1 to 9, wherein the step of adjusting the physical property value of the liquid crystal material is a step of adding a liquid crystal compound or a liquid crystal composition having a dielectric anisotropy of 5 to 40. The processing method according to claim 10, wherein the liquid crystal compound or composition having a dielectric anisotropy of 5 to 40 is a liquid crystal compound or composition having a 3,4,5-triphenylbenzene structure. The step of adjusting the physical property value of the liquid crystal material is a step of adding a liquid crystal compound or a liquid crystal composition having a refractive index anisotropy of 0.03 to 0.07. Processing method. The processing method according to claim 12, wherein the liquid crystal compound or liquid crystal composition having a refractive index anisotropy of 0.03 to 0.07 is a liquid crystal compound or liquid crystal composition having a bicyclohexane skeleton. The step of adjusting the physical property value of the liquid crystal material is a step of adding a liquid crystal compound or a liquid crystal composition having a refractive index anisotropy of 0.15 to 0.30. Processing method. The processing method according to claim 14, wherein the liquid crystal compound or liquid crystal composition having a refractive index anisotropy of 0.15 to 0.30 is a liquid crystal compound or liquid crystal composition having a biphenyl skeleton. The processing method according to any one of claims 1 to 15, wherein the step of adjusting the physical property value of the liquid crystal material is a step of adding an optically active substance. The processing method according to any one of claims 1 to 16, wherein the liquid crystal panel has a diagonal of 140 mm or more. The processing method according to any one of claims 1 to 17, wherein a physical property value of the liquid crystal material constituting the liquid crystal panel before recovery is equal to a physical property value of the liquid crystal material after recovery. The processing method according to any one of claims 1 to 17, wherein a physical property value of a liquid crystal material constituting the liquid crystal panel before recovery is different from a physical property value of the liquid crystal material after recovery. The processing method according to any one of claims 1 to 19, wherein the liquid crystal material is a liquid crystal material for an active matrix.