CN103278947A - Testing device and testing method for Kerr constant and double-refraction dispersion characteristic - Google Patents

Abstract

The invention relates to a testing device and testing method for measuring a Kerr constant and a double-refraction dispersion characteristic of a liquid crystal compound. The testing device for measuring the Kerr constant and the double-refraction dispersion characteristic of the liquid crystal compound comprises a light source, a polarizing plate, a polarization detecting plate and a detector, wherein a liquid crystal box with the liquid crystal compound is arranged between the polarizing plate and the polarization detecting plate, the light source is a visible light source with a broad spectrum, and a quarter wavelength plate is not needed by the testing device. Light emitted by the light source passes through the polarizing plate, the liquid crystal box and the polarization detecting plate in sequence, and is detected by the detector, and a model for obtaining the Kerr constant and a double-refraction index of the liquid crystal compound is built according to detected data. The testing device and the testing method can accurately measure a change rule of phase delay along with an electric field and the double-refraction dispersion characteristic, can build the accurate theoretical model, and facilitates research of application of polymer stabilizing blue-phase liquid crystal.

Description

The proving installation of Kerr constanr and birefringence dispersion characteristic and method of testing

Technical field

The present invention relates to the display technique field, particularly measure the Kerr constanr of liquid crystal composite and proving installation and the method for testing of birefringence dispersion characteristic.

Background technology

Because advantages such as that LCD has is light, thin, low-power consumption, occupied the main flow market of display at present.The liquid crystal material that current LCD adopts mainly be to row (twisted nematic, TN) type liquid crystal, yet nematic crystal is because response speed waits shortcoming to have brought certain limitation for the development of LCD more slowly.And blue phase liquid crystal (blue phase liquid crystal, BPLC), especially (polymer-stabilized-blue phase liquid crystal is PS-BPLC) because its excellent characteristic has caused insider's extensive attention to the polymer stabilizing blue phase liquid crystal.Blue phase liquid crystal is compared to nematic crystal, and not only response speed is fast, does not need oriented layer when being applied to display, and optics is isotropic when showing details in a play not acted out on stage, but told through dialogues, so display view angle is big and symmetrical.

For practicability early, people have especially done many researchs at optical characteristics, electrode structure and shape, the monomer aspects such as distribution, GTG and work physical process in polymer network structure to the various aspects of blue phase liquid crystal display.The principle of work of blue phase liquid crystal display is based on Ke Er (Kerr) effect, the Kerr effect of therefore measuring the blue phase liquid crystal under the different wave length with and birefraction particularly important to the application of blue phase liquid crystal with the wavelength dispersion under the electric field change.

The structure of general blue phase liquid crystal box is that parallel pole is produced on down on the transparency carrier, be similar to plane internal switch (In-Plane Switching, IPS) electrode structure of display panel, be about to space and parallel pixel electrode and public electrode and be arranged on the infrabasal plate, so when applying the parallel electric field that voltage can generation between pixel electrode and the public electrode on pixel electrode and public electrode the time be parallel to substrate.Yet, comparatively intensive at edge's electric field of electrode, electric field intensity is bigger because the difference of above-mentioned parallel electric field is apparent in view,, electric field relatively more loose at the centre position electric field between the electrode a little less than.So when the liquid crystal cell with plane internal switch structure is tested, according to the theoretical model of test, be difficult to match Kerr constanr and birefringent dispersion characteristics.

And if adopt the liquid crystal cell of top-bottom electrode structures, namely pixel electrode and public electrode electric field are separately positioned on the electrode structure on the upper and lower base plate, then can have the Electric Field Distribution of homogenising in the direction perpendicular to substrate (perhaps liquid crystal cell).

See also Fig. 1, Fig. 1 is the structural representation of the proving installation that is used for measuring the blue phase liquid crystal box with top-bottom electrode structures in a kind of prior art, this kind test mode is article (" Direct measurement of electric-field-induced birefringence in a polymer-stabilized blue-phase liquid crystal composite " the Jin Yan that adopts people such as Jin Yan to deliver at OPTICS EXPRESS in 2010, Meizi Jiao, Linghui Rao, and Shin-Tson Wu, OPTICS EXPRESS, 2010, Vol.18, No.11,11450) the Senarmont method that introduces tests.Proving installation 100 comprise helium-neon laser (He-Ne Laser) 101, polarizer slice 103, quarter-wave plate (Quarter Wavelength Plate, QWP) 105, checking bias slice 107 and detecting device 109.Wherein, the blue phase liquid crystal box 110 with top-bottom electrode structures is arranged between polarizer slice 103 and the quarter-wave plate 105, and has a tilt angle theta, produces phase delay with this in liquid crystal cell 110.Because the effect that 105 pairs of polarized lights of quarter-wave plate have phase delay equally, therefore, the phase delay that produces when testing is not only to be produced by liquid crystal cell 110, and quarter-wave plate 105 has certain influence for measurement result.And when measuring, need the light source of helium-neon laser 101 and the centre wavelength of quarter-wave plate 105 to fit like a glove, therefore can only carry out single wavelength measurement.Obtain Kerr constanr and the birefringence dispersion characteristic of polymer stabilizing blue phase liquid crystal under the multi-wavelength under the whole spectrum if desired, the quarter-wave plate that then needs to have the multi-wavelength mates corresponding incident light respectively.Therefore every Kerr constanr and birefringence dispersion characteristic of measuring the blue phase liquid crystal under a kind of wavelength just need repeat to apply driving voltage to liquid crystal cell more.Yet, for the blue phase liquid crystal material, when the electric field that applies bigger, when reaching a so-called limit saturation value, easily cause its liquid crystal composite inner structure to be subjected to expendable destruction, and repeat to drive the crystalline network that also easily causes blue phase liquid crystal and become unstable and be difficult to get back to original state, the photoelectric response curve of blue phase liquid crystal is changed, so-called voltage-penetrance curve offset (Voltage-Transmittance Shift) phenomenon namely takes place.

See also Fig. 2 a to Fig. 2 e, Fig. 2 a is illustrated under the following driving voltage of 40V, driving voltage-penetrance curve that front and back record for twice, wherein the curve of square discrete point performance is voltage-penetrance curve that preceding once (forword) test obtains, the curve of circular discrete point performance be after voltage-penetrance curve of obtaining of (backword) test once.It is 50V, 60V, 70V and 80V when following that Fig. 2 b to Fig. 2 e is illustrated respectively in driving voltage, the voltage that front and back record for twice-penetrance curve.Can obviously be seen by Fig. 2 a to Fig. 2 e, when driving voltage is respectively 40V, when 50V and 60V are following, voltage-penetrance the curve of preceding one-shot measurement is almost overlapping with the voltage-penetrance curve of back one-shot measurement, but when driving voltage reaches 70V, before the voltage-penetrance curve of one-shot measurement begin the phenomenon that occurs separating with the voltage-penetrance curve of back one-shot measurement, this kind phenomenon shows when preceding one-shot measurement when driving voltage reaches 70V, the inner structure of blue phase liquid crystal begins to be damaged, the curve that once measures before the curve that therefore back one-shot measurement obtains can deviate from.And when driving voltage reached 80V, the more tangible phenomenon of skew had to the right appearred in the voltage-penetrance curve of one-shot measurement before the voltage of back one-shot measurement-penetrance curve was compared.Hence one can see that, and driving voltage is more big, and shift phenomenon is more serious.Therefore, when respectively liquid crystal cell being tested at different wavelength, owing to whenever just need apply voltage with test once to liquid crystal cell at a kind of wavelength, therefore the multi-wavelength just needs repeatedly test, as long as cause the inner structure of blue phase liquid crystal to be damaged when big because of driving voltage in testing the preceding, so follow-up test result will cause inaccurate because skew has taken place voltage-penetrance curve.

Summary of the invention

Purpose of the present invention comprises Kerr constanr that a kind of liquid crystal composite is provided and proving installation and the method for testing of birefringence dispersion characteristic, to realize the higher purpose of measured value accuracy.

Particularly, a kind of proving installation that the embodiment of the invention provides, be mainly used in measuring Kerr constanr and the birefringence dispersion characteristic of liquid crystal composite, this proving installation comprises light source, polarizer slice, checking bias slice and detecting device, liquid crystal cell with liquid crystal composite is arranged between polarizer slice and the checking bias slice, and the light that this light source sends is successively through being detected by this detecting device after this polarizer slice, this liquid crystal cell and this checking bias slice.The pixel electrode of this liquid crystal cell and public electrode are separately positioned on two substrates that are oppositely arranged.Wherein, this light source is the visible light source with wide spectrum, and this detecting device be used for to receive through the light intensity of the linearly polarized light after the checking bias slice with the penetrance under the different driving voltage that obtains being applied to this liquid crystal cell.

Preferably, this detecting device is spectrometer.

Preferably, the pass between this penetrance and the driving voltage is:

, wherein, I _vBe this detecting device measured light intensity under different driving voltage, I _oThe measured light intensity of this detecting device when being parallel to the penetrating shaft of this polarizer slice for not applying driving voltage to the penetrating shaft of this liquid crystal cell and this checking bias slice, I _BFor not applying driving voltage to the penetrating shaft of this liquid crystal cell and this checking bias slice measured light intensity of this detecting device during perpendicular to the penetrating shaft of this polarizer slice.

Preferably, this proving installation is according to first party formula: T=sin ²[δ (θ)/2] and second party formula: $\mathrm{\δ}\left(\mathrm{\θ}\right)=\frac{2\mathrm{\π}{\mathrm{dn}}_o\left(E\right)}{\mathrm{\λ}}(\sqrt{1-\frac{{\sin }^2\mathrm{\θ}}{n_e^2\left(E\right)}}-\sqrt{1-\frac{{\cos }^2\mathrm{\θ}}{n_o^2\left(E\right)}})$ Obtain the refractive index n as undetermined coefficient _o(E) and n _e(E), wherein, T detects the penetrance that obtains for this detecting device, and d is the thickness of liquid crystal layer of this liquid crystal cell, and θ is the angle between the plane at the plane at this liquid crystal cell place and this polarizer slice or this checking bias slice place; Again according to third party's formula: Be depicted as a two-dimentional index of refraction diagram picture, wherein, n _IsoRefractive index when being isotropy for the optical property of liquid crystal composite, this two dimension index of refraction diagram picture is respectively with refractive index n _o(E) and n _e(E) be axle, look like to obtain refractive index n under the different voltages according to this two dimension index of refraction diagram _o(E) and n _e(E), by cubic formula: Δ n (E)=n _e(E)-n _o(E) obtain birefraction Δ n (E) under the different voltages.

Preferably, this proving installation is according to the 5th equation: $K\left(\mathrm{\λ}\right)=G\frac{{\mathrm{\λ}}^2{\mathrm{\λ}}^{{*}^2}}{E_s^2({\mathrm{\λ}}^2-{\mathrm{\λ}}^{{*}^2})}=A\frac{\mathrm{\λ}{\mathrm{\λ}}^{{*}^2}}{{\mathrm{\λ}}^2-{\mathrm{\λ}}^{{*}^2}}$ Obtain the Kerr constanr under the different wave length, wherein, A is a proportionality constant, λ ^*Characteristic wavelength for liquid crystal polymer.

Preferably, A equals 0.00653nm ^-1, λ ^*Equal 298.86nm.

The present invention also provides a kind of method of testing, is mainly used in measuring Kerr constanr and the birefraction of liquid crystal composite, and the method comprising the steps of: carry out the normalized of spectrum to obtain penetrance T; According to first party formula: T=sin ²[δ (θ)/2] and second party formula: $\mathrm{\δ}\left(\mathrm{\θ}\right)=\frac{2\mathrm{\π}{\mathrm{dn}}_o\left(E\right)}{\mathrm{\λ}}(\sqrt{1-\frac{{\sin }^2\mathrm{\θ}}{n_e^2\left(E\right)}}-\sqrt{1-\frac{{\cos }^2\mathrm{\θ}}{n_o^2\left(E\right)}})$ Obtain the refractive index n as undetermined coefficient _o(E) and n _e(E), wherein, T detects the penetrance that obtains for this detecting device, and d is the thickness of liquid crystal layer of this liquid crystal cell, and θ is the angle between the plane at the plane at this liquid crystal cell place and this polarizer slice or this checking bias slice place; According to third party's formula: $n_{\mathrm{iso}}=\sqrt{({2n}_o^2\left(E\right)+n_e^2\left(E\right))/3},$ Utilize image drawing method to obtain a two-dimentional index of refraction diagram picture, wherein, n _IsoRefractive index when being isotropy for the optical property of liquid crystal composite, this two dimension index of refraction diagram picture is respectively with refractive index n _o(E) and n _e(E) be axle, look like to obtain refractive index n under the different voltages according to this two dimension index of refraction diagram _o(E) and n _e(E); By cubic formula: Δ n (E)=n _e(E)-n _o(E) obtain birefraction Δ n (E) under the different voltages.

Preferably, this method of testing also comprises step: according to the 5th equation: $K\left(\mathrm{\λ}\right)=G\frac{{\mathrm{\λ}}^2{\mathrm{\λ}}^{{*}^2}}{E_s^2({\mathrm{\λ}}^2-{\mathrm{\λ}}^{{*}^2})}=A\frac{\mathrm{\λ}{\mathrm{\λ}}^{{*}^2}}{{\mathrm{\λ}}^2-{\mathrm{\λ}}^{{*}^2}}$ Obtain the Kerr constanr under the different wave length, wherein, A is a proportionality constant, λ ^*Characteristic wavelength for liquid crystal polymer.

Preferably, in the step of the normalized of carrying out spectrum: when not applying voltages to this liquid crystal cell, the penetrating shaft of setting this checking bias slice earlier is parallel to the penetrating shaft of this polarizer slice, and defining the measured light intensity of this detecting device is peak strength I _oMake the penetrating shaft of this checking bias slice perpendicular to the penetrating shaft of this polarizer slice this checking bias slice half-twist again, define the measured light intensity of this detecting device and be defined as background intensity I _BAfter applying voltages to this liquid crystal cell, according to the 6th equation:

Try to achieve the penetrance T under the different voltages, wherein, I _vBe the measured light intensity of this detecting device.

The proving installation and the method for testing that provide according to the embodiment of the invention, owing to do not need quarter-wave plate, therefore solved the problem that must adopt the single wavelength light source that mates with quarter-wave plate in the prior art, can carry out the disposable measurement of full spectrum, and the phase delay that liquid crystal cell produces is not influenced by quarter-wave plate.Therefore, the present invention can more accurately measure phase delay with Changing Pattern and the birefringence dispersion characteristic of electric field, sets up accurate more theoretical model, is convenient to study the application of polymer stabilizing blue phase liquid crystal.

Above-mentioned explanation only is the general introduction of technical solution of the present invention, for can clearer understanding technological means of the present invention, and can be implemented according to the content of instructions, and for above-mentioned and other purposes, feature and advantage of the present invention can be become apparent, below especially exemplified by preferred embodiment, and conjunction with figs., be described in detail as follows.

Description of drawings

Fig. 1 is the structural representation that is used for the proving installation of measurement blue phase liquid crystal in a kind of prior art.

Fig. 2 a to Fig. 2 e is respectively 40V, 50V, 60V, 70V and 80V when following at driving voltage, the synoptic diagram of the driving voltage that front and back record for twice-penetrance curve.

The structural representation of the proving installation of Fig. 3 is that the embodiment of the invention provides a kind of Kerr constanr of measuring liquid crystal composite and birefraction.

Fig. 4 a is the wavelength-penetrance curve distribution figure that records under different driving voltages.

Fig. 4 b increases progressively with 50nm at wavelength 450nm-800nm(respectively) the following synoptic diagram of measured driving voltage-penetrance curve.

Fig. 4 c is the synoptic diagram that the driving voltage-penetrance curve to Fig. 4 b carries out normalized driving voltage-normalization penetrance curve afterwards.

Fig. 5 be the parent nematic crystal drawn of result by experiment ordinary refraction index, unusual optical index and the mean refractive index under different voltages respectively with the relation curve synoptic diagram of wavelength.

Fig. 6 is the two-dimentional index of refraction diagram picture of drawing according to the variation of penetrance under wavelength 600nm.

Fig. 7 is the relation curve synoptic diagram of driving voltage and birefraction under the multi-wavelength.

Fig. 8 is the relation curve synoptic diagram of wavelength and Kerr constanr

Embodiment

Reach technological means and the effect that predetermined goal of the invention is taked for further setting forth the present invention, below in conjunction with accompanying drawing and preferred embodiment, the Kerr constanr and proving installation and its embodiment of method of testing, method, step, structure, feature and the effect of birefringence dispersion of the liquid crystal composite that foundation the present invention is proposed, detailed description as after.

Relevant aforementioned and other technology contents, characteristics and effect of the present invention can clearly present in following the cooperation in the graphic preferred embodiment detailed description of reference.By the explanation of embodiment, when can being to reach technological means and the effect that predetermined purpose takes to be able to more deeply and concrete understanding to the present invention, yet appended graphic only provide with reference to the usefulness of explanation, the present invention is limited.

Please refer to Fig. 3, the structural representation of a kind of Kerr constanr of measuring liquid crystal composite that it provides for the embodiment of the invention and the proving installation of birefraction.In Fig. 3, proving installation 200 comprises light source 201, polarizer slice 203, checking bias slice 205 and detecting device 207, does not need quarter-wave plate.Wherein, light source 201 is connected to polarizer slice 203 for having the visible light source of wide spectrum via optical fiber.Detecting device 207 is spectrometer, is connected with checking bias slice 205 via optical fiber.Have 45 ° of angles between the penetrating shaft of polarizer slice 203 and the transverse axis.

Liquid crystal cell 210 with polymer stabilizing blue phase liquid crystal places between polarizer slice 203 and the checking bias slice 205, has an angle theta between the plane at the plane at liquid crystal cell 210 places and polarizer slice 203 or checking bias slice 205 places, so that when liquid crystal cell 210 is applied voltage, can produce phase delay to incident light, preferably, angle theta is 60 °.The pixel electrode (not shown) of liquid crystal cell 210 and public electrode (not shown) are arranged at respectively on two substrates, preferably, the distance between two substrates, just thickness of liquid crystal box is 9 μ m.

The light that light source 201 sends is successively through being received to be detected by detecting device 207 by detecting device 207 after polarizer slice 201, liquid crystal cell 210 and the checking bias slice 205.The visible light with wide spectrum that light source 201 sends is through becoming the parallel lines polarized light after the polarizer slice 201, produce phase delay after the liquid crystal cell 210 of parallel lines polarized light through the inclination certain angle, subsequently through the linearly polarized light of checking bias slice 205 after testing the reception optical fiber of device 207 converge, thereby make detecting device 207 obtain penetration rate spectrum density (transmission spectrum intensity) under the different voltages.

Below process is introduced method of testing of the present invention in detail by experiment.

Before measuring, at first to carry out the normalization (normalized) of a spectrum and handle.The penetrating shaft of setting checking bias slice 205 earlier is parallel to the penetrating shaft of polarizer slice 203, when not applying driving voltage to liquid crystal cell 210, the optical property of the polymer stabilizing blue phase liquid crystal in the liquid crystal cell 210 is isotropy, light through liquid crystal cell does not have phase delay, detecting device 207 measured light intensity are maximal value, and defining described maximal value is peak strength I _oMake its penetrating shaft perpendicular to the penetrating shaft of polarizer slice 203 checking bias slice 205 half-twists then, at this moment, detecting device 207 measured light intensity are defined as background intensity (background intensity) I _B

When measuring, provide one to drive signal to liquid crystal cell 210.Preferably, the described driving signal square-wave signal that is 1kHz.Two substrates of liquid crystal cell 210 between produce uniform vertical electric field because drive signal this moment, therefore, produces uniform birefringence during the polymer stabilizing blue phase liquid crystal of light process liquid crystal cell 210.Normalization penetrance (Normalized Transmittance) T and light are through the light intensity I behind the liquid crystal cell 210 _V, peak strength I _oAnd background intensity I _BBetween the following equation of relation described:

$T=\frac{I_V-I_B}{I_o-I_B},---\left(1\right)$

Wherein, I _vBe this detecting device 207 measured light intensity under different voltages, can obtain normalization penetrance T under the different voltages according to equation (1).

See also Fig. 4 a-4c, wherein, that Fig. 4 a represents is the wavelength-penetrance curve distribution figure that records under different driving voltages, Fig. 4 b increases progressively with 50nm at wavelength 450nm-800nm(respectively) following measured driving voltage-penetrance curve, Fig. 4 c is that the driving voltage-penetrance curve to Fig. 4 b carries out normalized driving voltage-normalization penetrance curve afterwards.

Further, because proving installation 200 need not quarter-wave plate, therefore the phase delay that incident light is produced is only caused by liquid crystal cell 210, so normalization penetrance T also can be explained by following equation:

T=sin ²[δ(θ)/2], (2)

Wherein,

$\mathrm{\δ}\left(\mathrm{\θ}\right)=\frac{2\mathrm{\π}{\mathrm{dn}}_o\left(E\right)}{\mathrm{\λ}}(\sqrt{1-\frac{{\sin }^2\mathrm{\θ}}{n_e^2\left(E\right)}}-\sqrt{1-\frac{{\cos }^2\mathrm{\θ}}{n_o^2\left(E\right)}})---\left(3\right)$

Wherein, d is thickness of liquid crystal layer, and λ is wavelength, n _o(E) and n _e(E) respectively representation polymer stablize blue phase liquid crystal under different electric fields perpendicular to electric field be parallel to the refractive index of electric field, i.e. ordinary refraction index (ordinary refractive index) and unusual optical index (extraordinary refractive index).Can obtain the refractive index n as undetermined coefficient under different voltages in conjunction with aforesaid equation (2) and (3) _o(E) and n _e(E).

Further, when not applying driving voltage to liquid crystal cell 210, the optical property of the polymer stabilizing blue phase liquid crystal in the liquid crystal cell 210 is isotropy, its refractive index n _IsoAvailable following equation is represented:

$n_{\mathrm{iso}}=\sqrt{({2n}_o^2+n_e^2)/3},---\left(4\right)$

Wherein, n _oAnd n _eBe respectively the ordinary refraction index and unusual optical index of the parent nematic crystal (host nematic LC) that forms the polymer stabilizing blue phase liquid crystal.Preferably, the parent nematic crystal (as: JNC BP0003) selects the material with big dielectric anisotropy for use, as, dielectric constant Δ ε=120～140 so can reduce driving voltage.

See also Fig. 5, Fig. 5 be the parent nematic crystal drawn of result by experiment ordinary refraction index, unusual optical index and the mean refractive index under different voltages respectively with the relation curve synoptic diagram of wavelength, wherein, curve a is wavelength-unusual optical index curve, curve b is wavelength-ordinary refraction index curve, and curve c is wavelength-mean refraction rate curve.Parent nematic crystal ordinary refraction index, unusual optical index and mean refractive index when wavelength is 436nm, 509nm, 546nm, 589nm, 633nm have respectively been shown among Fig. 5.

Via experiment confirm, under any electric field, mean refractive index remains unchanged, and therefore, can obtain following equation:

$n_{\mathrm{iso}}=\sqrt{({2n}_o^2+n_e^2)/3}=\sqrt{({2n}_o^2\left(E\right)+n_e^2\left(E\right))/3}---\left(5\right)$

Further, utilize image to draw (image mapping) method and can obtain two-dimentional index of refraction diagram picture under any wavelength by equation (3) and (5), described two-dimentional index of refraction diagram picture is respectively with refractive index n _o(E) and n _e(E) as two axles, therefore by equation Δ n (E)=n _e(E)-n _o(E) can obtain birefraction Δ n (E) under any wavelength.As shown in Figure 6, Fig. 6 is the two-dimentional index of refraction diagram picture of drawing according to the variation of penetrance under wavelength 600nm, and wherein, the thickness of liquid crystal box of surveying is 9 μ m, and angle theta is 60 °.Many parallel different driving voltages (as curve d) of line representative that are tilted to the left among Fig. 6, the line that is tilted to the right (curve e) is then drawn according to above-mentioned parameter by equation (3) and (5) and is obtained the coordinate (x:1.574 at the stain place among the figure; What y:1.491) then show is under a certain driving voltage (driving voltage that curve d is represented), when wavelength is 600nm, and the ordinary refraction index (n of tested polymer stabilizing blue phase liquid crystal _e(E) be 1.574) and unusual optical index (n _o(E) be 1.491), therefore, can obtain birefraction Δ n (E)=n _e(E)-n _o(E)=1.574-1.491=0.083.

By said method, the birefraction Δ n (E) of (when increasing to 130V as driving voltage from 0V) can be noted down during different driving voltage under each wavelength, thereby can be used to draw the relation curve of driving voltage and birefraction.As shown in Figure 7, Fig. 7 draws is the relation curve synoptic diagram of driving voltage and birefraction under wavelength 400nm, 500nm, 600nm, 700nm and 800nm respectively.

And then, find to exist a threshold field E according to experimental result _Th, when the electric field that applies is lower than threshold field E _ThThe time, because the reason of residual phase delay, the birefraction Δ n (E) of polymer stabilizing blue phase liquid crystal is almost a constant; Surpass threshold field E and work as the electric field that applies _ThThe time, birefraction Δ n (E) can increase gradually and when the driving voltage value of reaching capacity (when being about 130V as driving voltage, electric field intensity is about 14.4V/ μ m) reach capacity.This phenomenon is called the Kerr effect of extension, can be by following convergence model description:

$\left\{\begin{array}{cc}\mathrm{\&Delta;n}=\mathrm{\&Delta;}{n}_{\mathrm{residual}}& (E<E_{\mathrm{th}})\\ \mathrm{\&Delta;n}=\mathrm{\&Delta;}{n}_{\mathrm{sat}}(1-\exp [-{\left(\frac{E}{E_s}\right)}^2\left]\right)& (E\&GreaterEqual;E_{\mathrm{th}})\end{array}\right.,---\left(6\right)$

Wherein, Δ n _SatRepresent saturated birefraction, E _sRepresent saturated electric field.

Kerr constanr K(λ under the different wave length) can calculate by following equation

$K\left(\mathrm{\&lambda;}\right)=\frac{\mathrm{\&Delta;}{n}_{\mathrm{sat}}\left(\mathrm{\&lambda;}\right)}{\mathrm{\&lambda;}{E}_s^2},---\left(7\right)$

The saturated birefraction Δ n that obtains by equation (6) and (7) match _SatWith saturated electric field E _sAnd the Kerr constanr of corresponding correspondence is as shown in table 1 below under a plurality of wavelength.Table 1 is depicted as Kerr constanr and the parameter n of the polymer stabilizing blue phase liquid crystal under the corresponding wavelength _SatAnd E _sFitting result

Table one

λ(nm)	Δn sat	E s(V/um)	K(nm/V 2)
				400	0.214	12.784	3.278
500	0.190	14.005	1.935
				600	0.153	14.250	1.255
700	0.137	14.314	0.962
				800	0.130	14.324	0.792

As can be seen from Table 1, saturated electric field E under different wavelength _sWhen 14V/ μ m, there is unconspicuous fluctuation.Generally, because experimental error and fitting correction error, experimental result can not be fully precisely, and it is more rational above-mentioned fluctuation occurring.Apparent in view is that for different wavelength, under more high electric field, the birefraction Δ n (E) under the experiment almost no longer changes.Therefore, the fitting result of Kerr constanr can be thought reasonably.

See also Fig. 8, what Fig. 8 showed is by the wavelength (Wavelength) of above-mentioned fitting result drafting and the curve synoptic diagram of Kerr constanr (Kerr constant).Wherein, utilize the Kerr constanr K(λ under single band model (single band model) match different wave length), fitting data clearlys show that following equation can be used to calculate the Kerr constanr K(λ of different wave length):

$K\left(\mathrm{\&lambda;}\right)=G\frac{{\mathrm{\&lambda;}}^2{\mathrm{\&lambda;}}^{{*}^2}}{E_s^2({\mathrm{\&lambda;}}^2-{\mathrm{\&lambda;}}^{{*}^2})}=A\frac{\mathrm{\&lambda;}{\mathrm{\&lambda;}}^{{*}^2}}{{\mathrm{\&lambda;}}^2-{\mathrm{\&lambda;}}^{{*}^2}}---\left(8\right)$

Wherein, proportionality constant A=G/E ² _S, λ ^*Be the characteristic wavelength (average resonant wavelength of the LC composite) of liquid crystal polymer, described characteristic wavelength is a constant, and G is a proportionality constant.Can obtain by fitting result: A=0.00653nm ^-1, λ ^*=298.86nm.

Thus, obtaining equation (8) afterwards, as long as know wavelength, just can know corresponding Kerr constanr.

The method of testing of this case measures to obtain penetrance under the different voltages according to detecting device 207 earlier, utilize image drawing method to obtain two-dimentional index of refraction diagram picture under any wavelength according to aforesaid equation (3) and (5) again, according to resulting two-dimentional index of refraction diagram picture, birefraction during different driving voltage under each wavelength can be noted down, therefore can obtain the relation curve of driving voltage and birefraction, birefraction under the different voltages of recycling and the relation of the Kerr constanr under the different wave length are carried out match, thereby set up the theoretical model of Kerr constanr and wavelength, i.e. equation (8) according to fitting result.Just can calculate Kerr constanr corresponding under the different wave length via equation (8).

Therefore, according to proving installation of the present invention and method of testing, owing to do not need quarter-wave plate, therefore solved the problem that must adopt the single wavelength light source that mates with quarter-wave plate in the prior art, can carry out the disposable measurement of full spectrum, and the phase delay that liquid crystal cell produces is not influenced by quarter-wave plate.Therefore, the present invention can more accurately measure phase delay with Changing Pattern and the birefringence dispersion characteristic of electric field, sets up accurate more theoretical model, is convenient to study the application of polymer stabilizing blue phase liquid crystal.

The above, it only is preferred embodiment of the present invention, be not that the present invention is done any pro forma restriction, though the present invention discloses as above with preferred embodiment, yet be not in order to limit the present invention, any those skilled in the art, in not breaking away from the technical solution of the present invention scope, when the technology contents that can utilize above-mentioned announcement is made a little change or is modified to the equivalent embodiment of equivalent variations, in every case be not break away from the technical solution of the present invention content, any simple modification that foundation technical spirit of the present invention is done above embodiment, equivalent variations and modification all still belong in the scope of technical solution of the present invention.

Claims (10)

1. proving installation, be mainly used in measuring Kerr constanr and the birefraction of liquid crystal composite, this proving installation comprises light source, polarizer slice, checking bias slice and detecting device, liquid crystal cell with liquid crystal composite is arranged between polarizer slice and the checking bias slice, the light that this light source sends passes through this polarizer slice successively, detected by this detecting device after this liquid crystal cell and this checking bias slice, the pixel electrode of this liquid crystal cell and public electrode are separately positioned on two substrates that are oppositely arranged, it is characterized in that: this light source is the visible light source with wide spectrum, and this detecting device be used for to receive through the light intensity of the linearly polarized light after the checking bias slice with the penetrance under the different driving voltage that obtains being applied to this liquid crystal cell.

2. proving installation according to claim 1, it is characterized in that: this detecting device is spectrometer.

3. proving installation according to claim 1, it is characterized in that: the pass between this penetrance and the driving voltage is:

Wherein, I _vBe this detecting device measured light intensity under different driving voltage, I _oThe measured light intensity of this detecting device when being parallel to the penetrating shaft of this polarizer slice for not applying driving voltage to the penetrating shaft of this liquid crystal cell and this checking bias slice, I _BFor not applying driving voltage to the penetrating shaft of this liquid crystal cell and this checking bias slice measured light intensity of this detecting device during perpendicular to the penetrating shaft of this polarizer slice.

4. according to the proving installation described in the claim 1, it is characterized in that: this proving installation is according to first party formula: T=sin ²[δ (θ)/2] and second party formula: $\mathrm{\&delta;}\left(\mathrm{\&theta;}\right)=\frac{2\mathrm{\&pi;}{\mathrm{dn}}_o\left(E\right)}{\mathrm{\&lambda;}}(\sqrt{1-\frac{{\sin }^2\mathrm{\&theta;}}{n_e^2\left(E\right)}}-\sqrt{1-\frac{{\cos }^2\mathrm{\&theta;}}{n_o^2\left(E\right)}})$ Obtain the refractive index n as undetermined coefficient _o(E) and n _e(E), wherein, T detects the penetrance that obtains for this detecting device, and d is the thickness of liquid crystal layer of this liquid crystal cell, and θ is the angle between the plane at the plane at this liquid crystal cell place and this polarizer slice or this checking bias slice place; Again according to third party's formula: $n_{\mathrm{iso}}=\sqrt{({2n}_o^2\left(E\right)+n_e^2\left(E\right))/3}$ Be depicted as a two-dimentional index of refraction diagram picture, wherein, n _IsoRefractive index when being isotropy for the optical property of liquid crystal composite, this two dimension index of refraction diagram picture is respectively with refractive index n _o(E) and n _e(E) be axle, look like to obtain refractive index n under the different voltages according to this two dimension index of refraction diagram _o(E) and n _e(E), by cubic formula: Δ n (E)=n _e(E)-n _o(E) obtain birefraction Δ n (E) under the different voltages.

5. proving installation according to claim 1 is characterized in that: this proving installation is according to the 5th equation: $K\left(\mathrm{\&lambda;}\right)=G\frac{{\mathrm{\&lambda;}}^2{\mathrm{\&lambda;}}^{{*}^2}}{E_s^2({\mathrm{\&lambda;}}^2-{\mathrm{\&lambda;}}^{{*}^2})}=A\frac{\mathrm{\&lambda;}{\mathrm{\&lambda;}}^{{*}^2}}{{\mathrm{\&lambda;}}^2-{\mathrm{\&lambda;}}^{{*}^2}}$ Obtain the Kerr constanr under the different wave length, wherein, A is a proportionality constant, λ ^*Characteristic wavelength for liquid crystal polymer.

6. according to the proving installation described in the claim 5, it is characterized in that: A equals 0.00653nm ^-1, λ ^*Equal 298.86nm.

7. a method of testing is applicable to the described proving installation of claim 1, is mainly used in measuring Kerr constanr and the birefraction of liquid crystal composite, and the method comprising the steps of:

Carry out the normalized of spectrum to obtain penetrance T;

According to first party formula: T=sin ²[δ (θ)/2] and second party formula: $\mathrm{\&delta;}\left(\mathrm{\&theta;}\right)=\frac{2\mathrm{\&pi;}{\mathrm{dn}}_o\left(E\right)}{\mathrm{\&lambda;}}(\sqrt{1-\frac{{\sin }^2\mathrm{\&theta;}}{n_e^2\left(E\right)}}-\sqrt{1-\frac{{\cos }^2\mathrm{\&theta;}}{n_o^2\left(E\right)}})$ Obtain the refractive index n as undetermined coefficient _o(E) and n _e(E), wherein, T detects the penetrance that obtains for this detecting device, and d is the thickness of liquid crystal layer of this liquid crystal cell, and θ is the angle between the plane at the plane at this liquid crystal cell place and this polarizer slice or this checking bias slice place;

According to third party's formula: $n_{\mathrm{iso}}=\sqrt{({2n}_o^2\left(E\right)+n_e^2\left(E\right))/3},$ Utilize image drawing method to obtain a two-dimentional index of refraction diagram picture, wherein, n _IsoRefractive index when being isotropy for the optical property of liquid crystal composite, this two dimension index of refraction diagram picture is respectively with refractive index n _o(E) and n _e(E) be axle, look like to obtain refractive index n under the different voltages according to this two dimension index of refraction diagram _o(E) and n _e(E);

By cubic formula: Δ n (E)=n _e(E)-n _o(E) obtain birefraction Δ n (E) under the different voltages.

8. method of testing according to claim 7 is characterized in that: further comprise step:

According to the 5th equation: $K\left(\mathrm{\&lambda;}\right)=G\frac{{\mathrm{\&lambda;}}^2{\mathrm{\&lambda;}}^{{*}^2}}{E_s^2({\mathrm{\&lambda;}}^2-{\mathrm{\&lambda;}}^{{*}^2})}=A\frac{\mathrm{\&lambda;}{\mathrm{\&lambda;}}^{{*}^2}}{{\mathrm{\&lambda;}}^2-{\mathrm{\&lambda;}}^{{*}^2}}$ Obtain the Kerr constanr under the different wave length, wherein, A is a proportionality constant, λ ^*Characteristic wavelength for liquid crystal polymer.

9. method of testing according to claim 8, it is characterized in that: A equals 0.00653nm ^-1, λ ^*Equal 298.86nm.

10. method of testing according to claim 7 is characterized in that: in the step of the normalized of carrying out spectrum:

When not applying voltages to this liquid crystal cell, the penetrating shaft of setting this checking bias slice earlier is parallel to the penetrating shaft of this polarizer slice, and defining the measured light intensity of this detecting device is peak strength I _o

Make the penetrating shaft of this checking bias slice perpendicular to the penetrating shaft of this polarizer slice this checking bias slice half-twist again, define the measured light intensity of this detecting device and be defined as background intensity I _B

After applying voltages to this liquid crystal cell, according to the 6th equation:

Try to achieve the penetrance T under the different voltages, wherein, I _vBe the measured light intensity of this detecting device.

Images