CN101080655A - Phase difference compensation, optical modulator, and liquid crystal display device and liquid crystal projector using same - Google Patents

Abstract

ABSTRACT On a transparent glass substrate (10), a first retardation compensation layer (12) and a second retardation compensation layer (14), which are formed of inorganic material, are provided. The first retardation compensation layer (12) includes a lamination of two kinds of deposition films sufficiently thinner than reference wavelength, one has high refraction index, and the other has low refraction index, to be a negative C-plate. The second retardation compensation layer (14) includes at least two oblique deposition films, to be a positive O-plate. The first retardation compensation layer (12) compensates a phase difference from liquid crystal molecules in a vertical orientation in a liquid crystal layer, and the second retardation compensation layer (14) compensates a phase difference from liquid crystal molecules in a hybrid orientation in the liquid crystal layer.

Description

Phase difference compensation, light modulation system, LCD and liquid crystal projection apparatus

Technical field

The present invention relates to the phase difference compensation that between a pair of polarizer, uses, particularly, relate to the phase difference compensation that improves its view angle dependency and light modulation system, LCD, and the liquid crystal projection apparatus that utilizes phase difference compensation.

Background technology

For utilizing optics rotation and the birefringence in liquid crystal molecule to finish the liquid crystal cells of optical modulation, polaroid is employed as a kind of polarizer.In the transmission-type liquid crystal cells, polaroid is arranged in the light incident surface and the light exit surface of liquid crystal cells.Polaroid is leading along the optical axis direction perpendicular to liquid crystal cells.Polaroid at light incident surface is used as the polarizer that nonpolarized light is converted to the linearly polarized photon that enters liquid crystal cells.The polaroid of light exit surface stop as polarization direction according to light modulated or transmission from the analyzer of the polarized light of liquid crystal cells.As polarizer, wire-grid polarizers is known identical with polaroid.But, generally use polaroid.Generally speaking; polaroid has a kind of structure; in this structure; have the iodine of absorption and the PVA of dyeing (polyvinyl alcohol (PVA)) film uniaxial orientation; and be clipped between the protective seam; have the axis of homology and absorption axes simultaneously, this axis of homology and absorption axes in perpendicular to the plane of optical axis direction each other in the right angle.When nonpolarized light entered polaroid, it was beamed into the rectangular each other polarized light component of two bundles.The polarized light component that is parallel to absorption axes is blocked, and parallel and the polarized light component transmission axis of homology are passed through.

Polaroid can be applicable to, for example, and TN (twisted-nematic) liquid crystal display cells.The TN liquid crystal display cells has ultra-large throughput rate in the operator scheme of different liquid crystal cells, and uses widely as the image display device of looking at type flat panel display and liquid crystal projection apparatus straight.The TN liquid crystal display cells has the rod shaped liquid crystal molecule that is filled between a pair of substrate, and forms transparent electrode and alignment films at this on to substrate.Liquid crystal molecule has been formed liquid crystal layer.The orientation of the major axis of liquid crystal molecule keeps and the substrate almost parallel, and little by little centers on the thickness direction rotation of liquid crystal layer, so that the major axis of liquid crystal molecule is along twist 90 degree smoothly to the path of another substrate from a substrate.When not having voltage to be applied to liquid crystal layer, the polarization direction of linearly polarized photon has been rotated 90 degree, and the direction along liquid crystal molecule advances to another substrate from a substrate simultaneously.When certain voltage was applied to liquid crystal layer, the distortion of liquid crystal molecule had disappeared, and near the liquid crystal molecule the center of thickness direction be in its major axis perpendicular to substrate the state that makes progress.Correspondingly, the polarization direction of linearly polarized photon is not changing when a substrate advances to another substrate.

When this is disposed in the light incident side and the light exit side of above-described TN liquid crystal cell to polaroid, and make the polarization direction of this polaroid be in right angle (cross Nicols configuration), incident light is risen partially by first polaroid is linear.When not having voltage to be applied to liquid crystal layer, the liquid crystal molecule in liquid crystal layer is distorted, thereby spends the polarization direction of rotation linearly polarized photons with 90.The linearly polarized photon that passes liquid crystal layer can pass through second polaroid, as bright state (normally white).But when being applied to the voltage of certain level on the liquid crystal layer, the polarization direction of linearly polarized photon can not rotate in liquid crystal layer, so linearly polarized photon blocked by second polaroid, as dark state.It should be noted, polaroid being arranged to its polarization direction at this is parallel to each other under the situation of (parallel Nicol configuration), when not having voltage to be applied on the liquid crystal layer, form dark state (normally deceiving), and when being applied to certain voltage on the liquid crystal layer, form bright state.Consider contrast performance, though the TN liquid crystal cell can be used in the general black system, in fact the TN liquid crystal cell is used in the white system usually.

In addition, this in cross Nicols configuration can be used in polaroid in the polarizing microscope etc.When the such sample of for example ore is placed between the polaroid, and when this sample is illuminated by the polarizer, if whole sample has optical isotropy character, then pass the linearly polarized photon of this polarizer can be under the prerequisite that does not change its polarization direction to marching to analyzer, and blocked by analyzer.Therefore, microscopical viewing area is dark.Yet if there is optically anisotropic crystal structure in sample, the linearly polarized photon of incident is modulated by the birefringence effect of sample so, and the light after the modulation can pass this analyzer.Therefore, light can be observed light after the modulation by microscopical viewing area.

The TN liquid crystal cell has the shortcoming at narrow visual angle owing to the birefringence of liquid crystal molecule.In usually white TN liquid crystal cell, when the voltage that is applied to liquid crystal layer increased, birefringence was occupied an leading position.Though the incident light perpendicular to liquid crystal cell is blocked under dark state fully, liquid crystal layer shows birefringence to the light of oblique incidence, thereby converts linearly polarized photon to elliptically polarized light.Because elliptic polarization luminous energy passes second polaroid, so the leakage of incident light has made the black light obscuration (black density) of selected pixel descend.This birefringence of liquid crystal molecule also little by little appears at from white states to the black state transforming process, and therefore in classification display, oblique incident ray also part leaks.Therefore, if stravismus, the contrast of the image on liquid crystal cell will reduce.

Because this visual angle attribute of TN liquid crystal cell, color and black light obscuration will change according to the direction of observation in the direct viewing type flat-panel monitor, and the contrast of the image that is projected on the screen in liquid crystal projection apparatus will reduce.From publication number be 2004-102200 Jap.P. as can be known, this defective can be improved by using phase difference compensation, and this phase difference compensation is made up of two kinds of alternately laminated thin layers that have different refractive indexes, and the optical thickness of each thin layer be light reference wavelength 1/100 to 1/5.Phase difference compensation is negative C plate.When the linearly polarized photon oblique incidence to vertical orientated so that when carrying out liquid crystal molecule that dark state shows, because birefringence has become ordinary light and light unusually.Negative C plate is used for according to the phase differential of incident angle compensation between ordinary light and unusual light as the single axial birefringence plate that has negative birefringence value.Therefore, elliptically polarized light is transform as linearly polarized photon again, and has prevented to leak from the light of analyzer.In addition, phase difference compensation can be formed by inorganic material, and these inorganic material have good thermal resistance, light resistance and in physics, chemically stability.Therefore, such phase difference compensation can be used for liquid crystal projection apparatus effectively in the mode identical with the direct viewing type flat-panel monitor.

U.S. Patent number 5,638,197 to have described the O-plate be effective to the visual angle attribute that improves the TN liquid crystal cell.The O-plate is that wherein primary optical axis favours the two-fold beam of reference planes (for example substrate of liquid crystal).On the direction of primary optical axis, do not introduce birefringence.(tiltedly deposition) can easily form the O plate on the substrate by from the direction that tilts inorganic material being deposited to.In addition, the O-plate can combine use with C-plate and A-plate.

People such as Hiroyuki MORI are at FUJIFILM RESEARCH ﹠amp; " Development ofWideView SA, a Film Product Widening the Viewing Angle of LCDs " that delivers on the DEVELOPMENT No.46-2001 51-55 page or leaf discloses and formed the WV film on as the TAC film on basis and make the plate-like potpourri fix with hybrid orientation.This WV film is put in the practical application.When in dark state shows, though that the most of liquid crystal molecule that distributes on the thickness direction of liquid crystal layer becomes is vertical orientated, near the liquid crystal molecule substrate becomes hybrid orientation.Just, according to the distance of distance substrate, the major axis of liquid crystal molecule little by little is elevated to vertical orientated from the orientation that is parallel to substrate.The two-fold beam of the open 2004-102200 of Jap.P. can not come compensation of phase poor by the liquid crystal molecule at hybrid orientation.But the MV film can come compensation of phase poor by the liquid crystal molecule of hybrid orientation, this because of the plate-like potpourri as described above be hybrid orientation.

When under cross Nicols configuration this is used in the polarizing microscope etc. to polaroid (polarizer and analyzer), covering attribute through obtaining sufficient light under the certain viewing angles of analyzer observation sample.If all luminous fluxes from the incident light of the polarizer all are parallel to optical axis, so just there is not light to penetrate from analyzer.Yet, in reality, comprise because dispersing of light and from the light of inclined light shaft from the luminous flux of general light source.For example, the lamp that metal halide lamp, extra-high-pressure mercury vapour lamp etc. have catoptron can be applicable to liquid crystal projection apparatus etc.Light from these light sources comprises many a large amount of luminous fluxes from inclined light shaft incident.Such incident light can not be only by utilizing under the cross Nicols configuration that polaroid is covered fully.

In Figure 33, the point that waits the relative brightness value of the light that will penetrate from analyzer links together.The center of curve is corresponding to 0 ° of visual angle, and concentric circumferences illustrates each visual angle, and each position angle of direction of observation is represented at each angle of describing along the periphery of curve.This curve shows relative brightness value becomes big corresponding to the visual angle and uprises.When visual angle during, will observe 10% or more incident light greater than 60 °.The viewed light that only leaks.In addition, be orthogonal owing to have 0 ° and 90 ° of these absorption axes of position angle, thereby the leakage of light reaches maximum in the position of 45 ° of distance absorption axes, and light cover attribute and has according to this position angle and pass 90 ° rotational symmetry to polaroid.

Be known that many kinds of phase difference compensations can be set in the cross Nicols configuration this on the optical path between the polaroid, cover attribute, particularly improve the visual angle attribute of polaroid thereby improve light.Claire Gu ﹠amp; " Extended Jones matrix method.II " that Pochi Yeh delivers on Journal of OpticalSociety of America A/Vol.10 No.5/May 1993 p966-973 discloses the phase difference compensation that is combined to form by C-plate and A-plate, and the combination of particularly positive C-plate and quarter wave plate and the phase difference compensation that is combined to form of negative C-plate and 3/4 wave plate are very effective for improving this visual angle attribute to the polaroid under the cross Nicols configuration.

About the phase difference compensation among the open 2004-102200 of Jap.P., when the TN liquid crystal cell was used to dark status displays under the conventional white pattern, this compensator can compensate effectively because the phase differential that oblique incidence causes to the incident light of vertical orientated liquid crystal molecule.But as mentioned above, this can not carry out effective phase difference compensation to the liquid crystal molecule of hybrid orientation.About United States Patent (USP) 5,638, in 197 by the oblique film formed O-plate of deposition of individual layer, thereby owing to do not understand the knowledge that is used to optimize the structure that this plate uses alone or is used for this plate and C-plate etc. combine the visual angle attribute that acquisition expects, so do not enter the practical stage.About the WV film in " Development of WideView SA ", this WV film can carry out effective phase difference compensation for direct view liquid crystal display etc.But when this WV film was applied to liquid crystal projection apparatus etc., this film wherein was exposed under the high-strength light that comprises short-wavelength light for a long time, thus for giving the WV film 10,000 hours or the more duration also has a lot of problems.

In order to address these problems, it is desirable to give phase difference compensation among the open 2004-102200 of Jap.P. with hybrid orientation.But it is very difficult producing and utilizing this phase difference compensation that is formed by the inorganic material with hybrid orientation.Equally also it is desirable to, negative C-plate among the open 2004-102200 of Jap.P. and the O-plate in the United States Patent (USP) 5,638,197 are combined.But owing to lack about its concrete configuration and the knowledge of actual effect, this notion does not have commercialization.

In order to improve this visual angle attribute,, described in " Extended Jones matrixmethod.II ", be effective by the phase difference compensation that is combined to form of C-plate and A-plate to the polaroid under the cross Nicols configuration.Yet, in the past, having only when utilizing the polymeric films of uniaxial tension, such phase difference compensation can form.This organic material has the characteristic of temperature dependency and moisture absorption, and its optical properties is easily along with long use or environment for use and change.In addition, in reality,, can be leaked away near 10% incident light so if the visual angle is 60 ° or bigger.Noting, on principle, is known by the phase difference compensation that is combined to form of two optics twin shaft phase difference plates.However, have only when utilizing polymeric films, this optics twin shaft polarizer can form, and forming process is very difficult.

The object of the present invention is to provide a kind of phase difference compensation, it can compensate the phase differential that the liquid crystal molecule by mixed and disorderly orientation causes effectively, and can produce with the cost-effective ground that reduces, also be to provide the liquid crystal projection apparatus that can effectively utilize this phase difference compensation.

Another object of the present invention is to provide a kind of phase difference compensation, for a pair of polaroid under the cross Nicols configuration, the light that it has an improvement cover attribute and improvement the visual angle correlativity, and be to provide light modulation system and the liquid crystal projection apparatus that uses phase difference compensation effectively.

Summary of the invention

To achieve the above object with other purpose, the phase difference compensation of the first embodiment of the present invention comprises: comprise that every layer all is first phase difference compensating layer of the multilayer film of the form birefringent body that formed by inorganic material, is used for compensating the phase differential that causes by at the vertical orientated liquid crystal molecule of liquid crystal layer; And comprise that every layer all is second phase difference compensating layer of the multilayer film of the form birefringent body that formed by inorganic material, is used for compensating the phase differential that is caused by liquid crystal layer hybrid orientation liquid crystal molecule.Preferably, at least one comprises that each layer all is the multilayer film that is formed by vacuum deposition method in first and second phase difference compensating layers.Preferably, second phase difference compensating layer comprises the multiple oblique deposited film that piles up, and these oblique deposited films are different one of at least in the position angle of the deposition direction of deposition surface and polar angle.Preferably, second phase difference compensating layer comprises three layers or the more multi-layered oblique deposited film that piles up.Be not required that the position angle of an oblique deposited film deposition direction is all different with the position angle and the polar angle of other oblique deposited film with polar angle.But the combination that requires the position angle of deposition direction of an oblique deposited film and polar angle is different with other oblique deposited film.Note, preferably, consider the total thickness and the throughput rate of second phase difference compensating layer, tiltedly the lamination number of deposited film is 10 or still less.

The position angle of the deposition direction of each oblique deposited film is confirmed as with different by the position angle of the given liquid crystal molecule of the alignment films of TN liquid crystal cells.When determining each optical axis vector according to position angle, polar angle and the delay of each oblique deposited film, the resultant vector A of optical axis vector is projected on the deposition surface of the such supporter of the substrate that is parallel to transparent substrates for example or TN liquid crystal cells orthogonally, the X and Y coordinates value (Ax, Ay) satisfy following formula:

-200nm≤Ax≤200nm and

-500nm≤Ay≤0nm。

Preferably, at the product (d Δ n) of the thickness d of the birefringence of the liquid crystal layer of the delay d of first phase difference compensating layer Δ n and TN liquid crystal cells and this liquid crystal layer _LCBetween relation as follows:

-2×(dΔn) _LC≤(dΔn)≤-0.5×(dΔn) _LC。

First phase difference compensating layer is made up of two kinds of alternately laminated a plurality of deposited films with different refractivity, and the optical thickness of each deposited film is 1/100 to 1/5 of a reference wavelength, and the thin thickness of the general optical thin film of the interference effect that this thickness Billy uses up is a lot.Preferably, in the light incident surface side and/or the light exit surface side of phase difference compensation anti-reflecting layer is set, thereby avoids the boundary reflection of phase difference compensation.

The phase difference compensation of first embodiment can be applied in the liquid crystal display device, for example has the direct viewing type liquid crystal projection apparatus of TN liquid crystal cells, preferably liquid crystal projection apparatus.When phase difference compensation be applied to comprise with three color light components in during the three-chip type color liquid crystal projector of each corresponding three TN liquid crystal cells, these three phase difference compensations, wherein each is corresponding to a TN liquid crystal cells, comprise at least two kinds of phase difference compensations, and every kind of phase difference compensation has the delay that differs from one another according to the reference wavelength of each color light component.Notice that as the liquid crystal projection apparatus that comprises phase difference compensation, existing forward projection instrument also has the rear projection instrument, in the forward projection instrument, image is come from the front side projection of screen, and in the rear projection instrument, image is come from the behind projection of screen.

In order to reach top purpose and other purpose, be used in the phase difference compensation of second embodiment of the present invention between a pair of polarizer that is under the cross Nicols configuration, comprise: perpendicular to the transparent substrates of the optical axis vertical with a pair of polarizer, first phase difference compensating layer by this transparent substrates support, the optical axis of this first phase difference compensating layer and transparent substrates are orthogonal, and second phase difference compensating layer that comprises three layers or more multi-layered stacked film, wherein every layer of stacked film all has the optical axis that favours the transparent substrates normal, and the direction that the light shaft positive cross of two films projects on the described transparent substrates in the described stacked film separates about 180 degree each other.Notice that each optical axis all has optical isotropy, and corresponding to the incident direction of light, wherein the refractive index at ordinary light beam of this direction and unusual light beam becomes equal.In addition, first and second phase difference compensating layers can form with inorganic material.

Can produce first and second phase difference compensating layers effectively by the deposited film that forms by deposition or sputter.First phase difference compensating layer is made up of two kinds of alternately laminated a plurality of deposit films with different refractivity, and the optical thickness of each thin layer is 1/100 to 1/5 of a reference wavelength, and the thin thickness of the general optical thin film of the interference effect that this thickness Billy uses up is a lot.

Effectively, the optical axis direction of a stacked film in second phase difference compensating layer is identical with the direction of the axis of homology of the polarizer of the light incident side of phase difference compensation.In addition, anti-reflecting layer is arranged on the light incident surface side and/or the light exit surface side of phase difference compensation.When phase difference compensation was applied to the light modulation system that comprises liquid crystal cells, preferably, phase difference compensation was disposed in the light incident surface side of liquid crystal cells.As for liquid crystal cells, transmission-type and reflection-type all can be used.When the reflective liquid crystal unit is used, entering projecting lens, and be projected onto on the screen from the axle mode from the light modulated of liquid crystal cells.

The phase difference compensation of first embodiment according to the invention, because being used to compensate second phase difference compensating layer of the phase differential that is caused by the hybrid orientation liquid crystal molecule and being by every layer all is that the multilayer of form birefringent body is film formed, so can carry out effective phase difference compensation.In first and second phase difference compensating layers at least one can all be that the means of the multilayer film that forms with vacuum-deposited method produce effectively by comprising every layer.Because second phase difference compensating layer comprises the multiple oblique deposited film that piles up, these oblique deposited films are different one of at least in the position angle on the deposition direction of deposition surface and polar angle, so can carry out effective phase difference compensation.And when phase difference compensation is applied to the TN liquid crystal cell that is in the conventional white pattern,, be improved so be shown the contrast of image because reduced the leak light under dark state that causes by oblique incident ray effectively.Because first and second phase difference compensating layers are by having good thermal resistance, light resistance and forming in physics, chemically the inorganic material of good stability, so phase difference compensation can according to the identical modes of LCD such as for example direct viewing type LCD monitor, be applied in the liquid crystal projection apparatus that comprises high-intensity light source.Because first phase difference compensating layer is the same with second phase difference compensating layer all is film formed by the deposition of inorganic material, therefore can produce this first and second phase difference compensating layer effectively in identical process.

The phase difference compensation of first embodiment according to the invention, first phase difference compensating layer that its optical axis is vertical with transparent substrates can be considered to as the C-plate, and it is poor to be used for according to the incident angle compensation of phase of oblique incident ray.In addition, comprise that second phase difference compensating layer of the multilayer film with the corresponding optical axis that points to different directions is considered to the O-plate of writing in reply, be used for polarization direction according to the incident angle rotation linearly polarized photon of incident light.The cooperation of these effects by first and second phase difference compensating layers can improve the visual angle attribute of the light modulation system that comprises the polarizer under the cross Nicols configuration.In addition, find in experiment that when the direction of the optical axis of two films in the stacked film separates 180 when spending each other, the visual angle attribute has been improved further.Preferably, two optical axises are spaced from each other 180 ± 5 degree, separate 180 ± 2 degree especially each other, and distinguishingly separate 180 degree each other.

When the direction of the direction of the optical axis of the one deck in the stacked film in second phase difference compensating layer and the axis of homology of polarizer is identical, can carries out effective light and cover.When first and second phase difference compensating layers all are when being formed by inorganic material, when particularly being formed by deposited film, phase difference compensation has good thermal resistance, and light resistance also can be produced on a large scale.

Phase difference compensation among second embodiment can be applied in the right various light modulation systems of the polarizer that comprises under the cross Nicols configuration, the such LCD of direct viewing type LCD monitor and liquid crystal projection apparatus for example preferably, in liquid crystal projection apparatus, image is projected onto on the screen after by the liquid crystal cells modulation.As for liquid crystal cells, can be used as the transport-type from the reflection-type of axle.In addition, as for projector, forward projection instrument and rear projection instrument can both be used.

Description of drawings

Fig. 1 is the explanatory view of LCD that utilizes the phase difference compensation of first embodiment of the present invention;

Fig. 2 is the viewgraph of cross-section of the phase difference compensation of first embodiment;

Fig. 3 is the explanatory view of the configuration of first phase difference compensating layer;

Fig. 4 is the explanatory view of the configuration of second phase difference compensating layer;

Fig. 5 is the explanatory view that is used to form the deposition device of oblique deposited film;

Fig. 6 is the position angle of the oblique deposited film of explanation and the explanatory diagram of polar angle (polar angle);

Fig. 7 is the explanatory diagram of the optical axis vector of the oblique deposited film of explanation;

Fig. 8 is the explanatory diagram of the configuration of explanation TN liquid crystal cell;

Fig. 9 is the explanatory diagram of explanation resultant vector;

Figure 10 is the contrast curves figure of TN liquid crystal cell;

Figure 11 is the contrast curves figure that has the TN liquid crystal cell of the phase difference compensation in the experiment 1;

Figure 12 is the contrast curves figure that has the TN liquid crystal cell of the phase difference compensation in the experiment 2;

Figure 13 is the contrast curves figure that has the TN liquid crystal cell of the phase difference compensation in the experiment 3;

Figure 14 is the contrast curves figure that has the TN liquid crystal cell of the phase difference compensation in the experiment 4;

Figure 15 is the contrast curves figure that has the TN liquid crystal cell of the phase difference compensation in the experiment 5;

Figure 16 is the contrast curves figure that has the TN liquid crystal cell of the phase difference compensation in the experiment 6;

Figure 17 is the explanatory view of three-chip type color liquid crystal projector of using the phase difference compensation of first embodiment;

Figure 18 is the chart of wavelength dependence of the delay of explanation TN liquid crystal cell;

Figure 19 is the chart of wavelength dependence of the delay of first phase difference compensating layer;

Figure 20 is the curve map of the delay attribute of the explanation TN liquid crystal cell and first phase difference compensating layer;

Figure 21 is the chart of wavelength dependence of the delay of first phase difference compensating layer that improves of explanation;

Figure 22 is the curve map that the delay attribute of first phase difference compensating layer that improves is described;

Figure 23 is the explanatory view of optical system of function that is used to check the phase difference compensation of the second embodiment of the present invention;

Figure 24 is the viewgraph of cross-section of the phase difference compensation of second embodiment;

Figure 25 is the explanatory view of the configuration of second phase difference compensating layer;

Figure 26 is the position angle of the oblique deposited film of explanation and the explanatory diagram of polar angle;

Figure 27 is the explanatory diagram of explanation rectangular projection to the optical axis coordinate vector on x-y plane;

Figure 28 is the brightness curve chart that the light of phase difference compensation in the illustrative experiment 7 covers attribute;

Figure 29 is the brightness curve chart that the light of the comparable sample of explanation phase difference compensation covers attribute;

Figure 30 is an explanatory view of having used the LCD of transmission-type TN liquid crystal cell, and wherein, the phase difference compensation of second embodiment is applied on the TN liquid crystal cell;

Figure 31 is an explanatory view of having used the LCD of reflection-type TN liquid crystal cell, and wherein, the phase difference compensation of second embodiment is applied on the TN liquid crystal cell;

Figure 32 is an explanatory view of having used the three-chip type color liquid crystal projector of the phase difference compensation among second embodiment; And

Figure 33 illustrates that when using general light source the light that is in a pair of polaroid under the cross Nicols configuration covers the brightness curve chart of attribute.

Embodiment

The phase difference compensation of first embodiment of the present invention is described now.Utilized the LCD of phase difference compensation to have as shown in Figure 1 notional structure.Polaroid 3,4 is separately positioned on light incident surface one side and light exit surface one side of TN liquid crystal cell 2.The polarization axle of the polaroid 3,4 that under the conventional white pattern, uses mutually vertical (cross Nicols configuration).Polaroid 3 is the polarizers that illumination light converted to linearly polarized photon.Polaroid 4 is analyzers, and its transmission is by the part light of polarization direction TN liquid crystal cell 2 modulation, the corresponding polaroid 4 in polarization direction, and covers the residue light from TN liquid crystal cell 2.

Between TN liquid crystal cell 2 and polaroid 4, the phase difference compensation 6 of first embodiment of the invention is installed.The liquid crystal molecule of TN liquid crystal cell 2 has birefringence effect, and this effect can convert linearly polarized photon to different elliptically polarized light according to the orientation of liquid crystal molecule and the incident angle of illumination light.Therefore, there is a kind of possibility to take place, that is, is superimposed on the figure imaging in the part of the light of polaroid 4 places crested.Phase difference compensation 6 has compensated by the phase differential between the ordinary light of liquid crystal molecule birefringence generation and the unusual light, thereby converts elliptically polarized light to linearly polarized photon on the contrary.Because phase difference compensation 6 is to be made of the formed film of the deposition of inorganic material, thereby this compensator comprises the transparent substrates as for example glass substrate that supports usefulness.Notice that the transparent substrates of the transparent substrates of TN liquid crystal cell 2 and polaroid 4 can be used as support.Notice that phase difference compensation 6 can be installed between TN liquid crystal cell 2 and the polaroid 3 to realize identical effect.

As shown in Figure 2, phase difference compensation 6 has first phase difference compensating layer 12 and second phase difference compensating layer 14 that is superimposed upon as on the side of the glass substrate 10 that supports, and respectively on second phase difference compensating layer 14 and the anti-reflecting layer 15,16 that forms on the another side of glass substrate 10. Anti-reflecting layer 15,16 is used to prevent surface reflection.As anti-reflecting layer, for example can use by MgF with low-refraction ₂The monofilm of λ/4 optical thicknesses that form.In addition, can use and have a plurality of layers the anti-reflective film that forms by different deposition materials.Note,, film formed the time, can use vacuum deposition method by resistance heated or electron beam heating by deposition when first and second phase difference compensating layers 12,14 and anti-reflecting layer the 15, the 16th, or sputter deposition.The relative position of first phase difference compensating layer 12 and second phase difference compensating layer 14 can reverse under the situation of the optical effect that does not reduce them, and can form on each side of glass substrate 10.

As shown in Figure 3, first phase difference compensating layer 12 comprises a plurality of film L1, the L2 that alternately is stacked on the glass substrate 10.The refractive index of film L1, L2 is different mutually.Each deposition direction is vertical with deposition surface.Each optics thickness of film (product of physical thickness and refractive index) is basically less than the wavelength X (for example 550nm) of incident light.Each optics thickness of film preferably from λ/100 to λ/5, be more preferably from λ/50 to λ/5, and be actually/10 from λ/30 to λ, this Billy is thinner with the general optical thin film of the interference of light.The multilayer film that forms is the C-plate of negative birefringence, (single axial birefringence plate).As negative birefringence C-plate, rather than other type of first phase difference compensating layer 12 of multilayer film also can be used.

Following design first phase difference compensating layer 12.As publication, kogaku (Japanese optics periodical), vol.27, no.1 (1998), pp.12-17, described in, birefringence n is defined as the ratio of the optical thickness of two deposited film L1, L2 with different refractivity.It is big that birefringence n becomes along with the difference of refractive index.Delay d Δ n is defined as the product of total physical thickness d of the birefringence n and first phase difference compensating layer 12.The ratio of the optical thickness of two films is designed such that and obtains big birefringence n.So, determine total physical thickness of first phase difference compensating layer 12 according to the delay d Δ n of expectation.

The sample of multilayer deposited film can pass through 40 TiO ₂Layer and 40 SiO ₂Layer alternately is deposited on the glass substrate 10 and prepares.Every layer physical thickness is 5nm.The delay that spectral type elliptical polarized light meter can be used to measure this sample.As a result, this sample shows and postpones to be the negative birefringence of 208nm, and the ordinary optical axis of sample (not having optically anisotropic axle) is vertical with glass substrate 10.Therefore, be clear that very this sample is as negative C-plate.

As the deposition materials of deposited film L1, L2, the example of high refractive index, thin film materials is TiO ₂(2.20 to 2.40) and ZrO ₂(2.20).Numeric representation refractive index in parenthesis.The low refractive index film examples of material is SiO ₂(1.40 to 1.48), MgF ₂(1.39) and CaF ₂(1.30).As the deposition materials of deposited film L1 and L2, may adopt material, for example CeO ₂(2.45), Nb ₂O ₅(2.31), SnO ₂(2.30), Ta ₂O ₅(2.12), In ₂O ₃(2.00), ZrTiO ₄(2.01), HfO ₂(1.91), Al ₂O ₃(1.59 to 1.70), MgO (1.70), AlF ₃, diamond thin, LaTiO _xWith the samarium oxide.The example of the combination of high refractive index film and low refractive index film is TiO ₂/ SiO ₂, Ta ₂O ₅/ Al ₂O ₃, HfO ₂/ SiO ₂, MgO/MgF ₂, ZrTiO ₄/ Al ₂O ₃, CeO ₂/ CaF ₂, ZrO ₂/ SiO ₂, and ZrO ₂/ Al ₂O ₃

A plurality of deposited film L1, L2 are deposited by the use of deposition device.Deposition device has the gate that glass substrate 10 and source material are shielded.This gate optionally opens and closes, so that two deposited film L1, L2 optionally are deposited on the glass substrate 10.Replace this gate, glass substrate 10 can be fixed on predetermined speed and move on the fixator of this substrate.By being passed, substrate alternately deposits this two deposited film L1, L2 on the source material of evaporation.Because deposition device needs single vacuum process so that obtain a plurality of films, so might increase throughput rate.

Second phase difference compensating layer 14 is to form the stack layer with O-plate function by mineral compound.As production method, oblique deposition is arranged, as the photoetching process of describing among the open 2004-212468 of Jap.P., the arrangement of rodlike molecule etc.Consider throughput rate, tiltedly deposition is the most desirable.Second phase difference compensating layer 14 that is formed by oblique deposition will be described below.When using oblique deposition, first and second phase difference compensating layers can form by identical vacuum method.

As shown in Figure 4, second phase difference compensating layer 14 has three oblique deposited film S1, S2, S3 that pile up.As shown in Figure 2, first piles up oblique deposited film S1 and is stacked on first phase difference compensating layer 12.But, possiblely be, first and second phase difference compensating layers 12 and 14 position can exchange mutually, the such first oblique deposited film S1 forms on glass substrate 10, the second and the 3rd oblique deposited film S2 and S3 sequentially pile up on the oblique deposited film S1 first and form, and first phase difference compensating layer 12 forms on the 3rd oblique deposited film S3 then.In addition, also possible is that first phase difference compensating layer 12 and second phase difference compensating layer 14 form on two sides of glass substrate 10 respectively, and anti-reflecting layer 15 and 16 forms on the outermost layer of first and second phase difference compensating layers 12,14 respectively.

Different with the deposited film L1 and the L2 of first phase difference compensating layer 12, the oblique deposited film S1 of second phase difference compensating layer 14 is deposited from the tilted direction towards deposition surface S0 to S3.Deposited film S1 each cartridge by diffusion of volatile treating agent M1 that has microcosmic respectively in the S3 is to M3, and M1 extends towards its deposition direction sideling to M3.As shown in Figure 4, these cartridge by diffusion of volatile treating agent M1 is not parallel to the bearing of trend of M3 each other.Tiltedly deposited film S1 each in the S3 can both demonstrate or the form dielectric grid effect as independent one deck, and can be used as the O-plate with positive birefringence.But in second phase difference compensating layer 14 of the present invention, a plurality of oblique deposited films are stacked to obtain unique optical effect.

For example, tiltedly deposited film S1 can be formed by the deposition device shown in the skewing scheme 5 to S3.The material fixator 21 that rotates in the mode of capstan head is arranged on the substrate 20. Deposition materials 22,23 is 21 li of material fixators.After vacuum chamber was vacuumized, electron gun 25 gave off electron beam 27 to deposition materials 22, thus hydatogenesis material 22.Therefore, can carry out vacuum moulding machine.Material fixator 21 is opened or shut to gate 29, thereby begin or stop vacuum moulding machine.Material fixator 21 rotates with the deposition materials of selecting to be used for depositing 22,23.Basically, second phase difference compensating layer 14 is to be formed by a plurality of retes from a kind of deposition materials.But by utilizing material fixator 21, a plurality of deposition materials can be used as required.

Substrate holder 30 is being tilted and is being placed on the material fixator 21, is used to support sample substrate 26.The surface-supported normal of substrate holder 30 and from the angled β of deposition materials 22 vertically extending line P.Therefore, the deposition surface of sample substrate 26 also becomes the β angle with line P.By substrate holder 30 is rotated the may command angle beta around the axle perpendicular to axle 30a.In addition, by substrate holder 30 is rotated around axle 30a, may command is corresponding to the azimuthal angle [alpha] of the line P in deposition surface.Because line P is corresponding to the deposition direction towards deposition surface, can control deposition direction in two ways towards deposition surface by changing angle [alpha] and β.As mentioned above, angle [alpha] is corresponding to the position angle of the deposition direction in deposition surface, and angle beta is corresponding to the polar angle of representative towards the pitch angle of the deposition direction of deposition surface.Therefore, after this, angle [alpha] is called azimuth angle alpha, and angle beta is called polar angle β.

The film thickness monitor 31 of quartz crystal type monitors the thickness of deposited film on measurement plane, thereby relatively measures the thickness of the deposited film on sample substrate 26.When forming oblique deposited film, elliptical polarized light meter 32 receives from the optical transmitting set 33 and the measuring light of passing monitor substrate 28, follows birefringent phase differential thereby relatively measure.The measurement plane of film thickness monitor 31 and comprise that the phase Difference Measuring System that monitors substrate 28 can be rotated is with the polar angle β corresponding to substrate holder 30.In addition, by the displacement of shadow shield, in finishing oblique deposited film during the formation of each layer at every turn, all can expose measurement plane and monitor the new clean surface of substrate.Therefore, tiltedly every layer phase differential of deposited film can both be monitored.The data of the phase differential of measuring according to elliptical polarized light meter 32 can estimate the delay of oblique deposited film.Therefore, by under the data conditions that monitors from elliptical polarized light meter 32 and thickness monitor 31, depositing, can obtain to comprise a plurality of layers oblique deposited film that wherein each layer all has the delay of expectation.

According to above-mentioned process,, comprise that second phase difference compensating layer of the oblique deposited film of multilayer can form on sample substrate 26 by monitoring the phase differential of each layer.And under first phase difference compensating layer 12 is formed on situation on the glass substrate 10 at first as shown in Figure 2, by being fixed on glass substrate 10 on the substrate holder 30 and finishing oblique deposition, can on first phase difference compensating layer 12, form multilayer second phase difference compensating layer 14 so that each layer all has the delay of design in advance.

As shown in Figure 6, when rectangular projection is to the X-Y coordinate on deposition surface S0, represent by azimuth angle alpha of measuring from X-axis in the counterclockwise direction and the polar angle β that measures from the Z axle towards the deposition direction P of deposition surface S0.Polar angle β does not have positive and negative directivity and the pitch angle Z axle, and azimuth angle alpha has directivity with reference to X-axis.

As shown in Figure 8, for the twisted-oriented of 90 degree being provided for liquid crystal molecule 38, provide the interior substrate 35,36 of TN liquid crystal cell 2, alignment films 35a, 36a.Alignment films 35a gives the orientation that liquid crystal molecule 38 is parallel to the paper that Fig. 8 is shown.Alignment films 36a gives the orientation of liquid crystal molecule 38 perpendicular to this paper.Polaroid 3,4 is adjusted to the orientation of alignment films 35a, 36a respectively.When saturation voltage was applied in, as shown in Figure 8, the liquid crystal molecule 38 that is distributed in the central area on the element thickness direction was in vertical orientated.Yet, near substrate 35,36, have the continually varying zone, angle of inclination of liquid crystal molecule 38.First phase difference compensating layer 12 of phase difference compensation 6 is poor by the birefringence effect compensation of phase of the liquid crystal molecule 38 on vertical orientated.Second phase difference compensating layer 14 is by in molecule tilt angle continually varying zone, the zone of hybrid orientation just, the birefringence effect compensation of phase of liquid crystal molecule 38 poor.

The orientation of liquid crystal molecule 38 depends on the frictional direction of making alignment films 35a and 36a.As shown in Figure 7, friction process is applied to the alignment films 35a that is in direction shown in arrow 35b and 36b, among the 36a.In view of the above, the orientation of liquid crystal molecule 38 is determined.Notice that the X-Y-Z coordinate system in Fig. 6,7 is that identical direction defines in the space.The direction of X-axis is determined so that the frictional direction 35b of alignment films 35a and X-axis have angle δ=45 °.Correspondingly, the frictional direction 36b of alignment films 36a is corresponding to the direction that becomes-45 ° with X-axis.When voltage was applied to TN liquid crystal cell 2 in this arrangement, the major axis that is distributed in the liquid crystal molecule of the central area on the liquid crystal cell thickness direction moved in the Y-Z plane, and its pitch angle moves to the positive dirction of Z axle from the positive dirction of Y-axis.

The approximate optical axis of deposition direction P corresponding to oblique deposited film S1.Tiltedly deposited film S1 has the O-plate attribute that demonstrates from birefringence effect.But tiltedly deposited film S1 shows the optical isotropy to the light that is parallel to cartridge by diffusion of volatile treating agent M1 orientation.Yet optical axis enters in the film S1, and is that 1 medium (for example air) and the interface place between the film S1 reflect in refractive index, and this optical axis is corresponding to the orientation of cartridge by diffusion of volatile treating agent M1 then.Just, optical axis tilts with the direction of an angle from cartridge by diffusion of volatile treating agent according to the refractive index of oblique deposited film.Therefore, on precision, deposition direction P and optical axis are not strict equidirectionals.

Correspondingly, optical axis vector P1 can be according to deposition direction P and delay (d Δ n) _S1Determine that wherein, deposition direction P by azimuth angle alpha and polar angle β definition, and postpones (d Δ n) when initial point O is basic point _S1Be by the film thickness of oblique deposited film S1 and birefringence definition.According to the identical mode of optical axis vector P1 of oblique deposited film S1, can determine optical axis vector P2, the P3 of oblique deposited film S2, S3.Generally speaking, optical axis vector Pi is by postponing (d Δ n) according to following _SiAzimuth angle alpha _iWith polar angle β _iCombination represent:

Pi (x, y, z)=((d Δ n) _Si* cos α _i* tan β _i, (d Δ n) _Si* sin α _i* tan β _i, (d Δ n) _Si) notice that subscript i represents the number (for example S1, S2, S3) of oblique deposited film in the superincumbent numeral.The resultant vector A of these optical axis vectors Pi can followingly represent:

A=∑ Pi resultant vector A is corresponding to the delay (d Δ n) by every layer _SiThe mean vector of the oblique deposited film of multilayer of weighting.

In order to form second phase difference compensating layer 14 with three layers, tiltedly deposited film S1 has multiple combination to S3, and this depends on how to determine that optical axis vector P1 is to P3 and in order to obtain optical axis vector P1 to P3 and to postponing (d Δ n) _Si, azimuth angle alpha _iWith polar angle β _iSelection.In the present invention, the basis of assignment is that (Ax Ay), thereby optimizes second phase difference compensating layer 14 for the coordinate figure of x and y when resultant vector A is projected to deposition surface S0 orthogonally.

Particularly, when oblique deposited film S1 be synthesized to the optical axis vector P1 of S3 to P3 and resultant vector A as shown in Figure 9 by rectangular projection during to deposition surface S0, wherein, the x-y surface is that the positive dirction of Z axle from Fig. 6 is observed, resultant vector A is defined as making that (Ax, condition formula 1 Ay) is met about the x of resultant vector A and y coordinate figure.This condition formula 1 is as follows:

(condition formula 1-I)

-200nm≤Ax≤200nm and

-500nm≤Ay≤0nm。

Ax is defined by the coordinate system identical with the XYZ coordinate system of description in Fig. 6 and 7 with Ay, and is confirmed as the major axis orientation corresponding to the liquid crystal molecule that is distributed in the central area on the liquid crystal cell thickness direction.The direction of twist of Ax and Ay and liquid crystal molecule is irrelevant.The preferred value of Ax and Ay is as follows:

(condition formula 1-II)

-100nm≤Ax≤100nm and

-300nm≤Ay≤-50nm。

In TN liquid crystal cell 2, the ratio that becomes vertical orientated liquid crystal molecule 38 is along with the value of the saturation voltage that applies for dark status displays changes.Because first phase difference compensating layer 12 comes the compensate for optical anisotropy by the birefringence effect of vertical orientated liquid crystal molecule 38, so when the large percentage of vertical orientated liquid crystal molecule 38, it is big that the length of delay of first phase difference compensating layer 12 becomes.The delay of vertical orientated liquid crystal molecule 38 is in 50% to 90% the scope that whole TN liquid crystal cells postpones.

For determining the delay of first phase difference compensating layer 12, need to consider other factor.Just, be necessary to offset the excessive compensation of the phase differential that on positive Z-direction, causes by second phase difference compensating layer 14.Tiltedly deposited film S1 compensates the angle relevant with phase differential to S3 by near the liquid crystal molecule the substrate of TN liquid crystal cell 2.But, in order to compensate this phase differential, need the approximate oblique deposited film that is parallel to substrate of optical axis by the approximate liquid crystal molecule that is parallel to substrate, just, polar angle β is near 90 °, so that make the approximate substrate that is parallel to of orientation of cartridge by diffusion of volatile treating agent.In reality, it is extremely difficult producing this oblique deposited film.

Therefore, in order to come compensation of phase poor, need to use the thick oblique deposited film that has less than the polar angle at theoretical angle by the approximate liquid crystal molecule that is parallel to substrate.As a result, on direction, carried out the excessive compensation of phase differential perpendicular to substrate.Because this reason, first phase difference compensating layer 12 need have the effect that reduces excessive compensation by second phase difference compensating layer 14.The retardation of first phase difference compensating layer 12 is determined to produce negative phase differential, is used to offset the excessive positive phase difference that the compensation performance by second phase difference compensating layer 14 causes.Though the lower limit of retardation is " 0 ", its upper limit is the amount that depends on excessive positive phase difference.Particularly, the thickness of film is limited by difficulty that for example forms film and cost.

Consider top factor, in the negative delay (d Δ n) of first phase difference compensating layer 12 and the just delay (d Δ n) of TN liquid crystal cell _LCBetween preference relation as follows:

(condition formula 2)

-2×(dΔn) _LC≤(dΔn)≤-0.5×(dΔn) _LC。

As the deposition materials of second phase difference compensating layer 14, identical with the deposition materials of first phase difference compensating layer 12, can use such as TiO ₂, SiO ₂, ZrO ₂And Ta ₂O ₃The material of sufficient optical clarity oblique deposited film form, that have Wavelength-independent.

After this, the concrete experiment of phase difference compensation 6 of the present invention will be explained.These experiments are to be used for according to contrast curves, estimate the optimum structure condition of first and second phase difference compensating layers that are appropriate to the TN liquid crystal cell.The residing condition of TN liquid crystal cell is: the birefringence at wavelength 550nm place (Δ n) is 0.124, and the thickness of unit (thickness of liquid crystal layer) is 4500nm, and length of delay (d Δ n) _LCBe 558nm.Contrast curves is formed the brightness that makes between the bright state of liquid crystal and dark state and is measured as the contrast under each visual angle, and the visual angle with same contrast is joined together.The contrast curves of TN liquid crystal cell itself is shown in Figure 10.As can be seen from Figure 10, contrast takes place to change hugely with the visual angle.In the experiment of noting being described below, it is that the reference wavelength of first and second phase difference compensating layers is to carry out under the condition of 550nm that film forms.

(experiment 1)

(50mm * 50mm) is cleaned by acetone and is dry fully, then it is arranged in the deposition device that is used to carry out common preceding deposition (β=0 °) as the Corning1737 of glass substrate.Vacuum chamber is put into air to 1 * 10 ^-4Pa, thereby and glass substrate be heated to 300 ℃ and form three layers of anti-reflective film, anti-reflective film is the SiO that λ/4 optics are thick that begins to pile up in order from the glass lined bottom side ₂, the TiO that λ/2 optics are thick ₂And the SiO that λ/4 optics are thick ₂Reference wavelength λ is 550nm.

After forming anti-reflecting layer, glass substrate underneath side of a quilt in vacuum chamber turns towards the other places, to form first phase difference compensating layer.First phase difference compensating layer comprises multilayer film, and wherein, two types deposited film L1, L2 are alternately piled up as shown in Figure 3.Its delay (d Δ n) is born.Can be controlled to a certain extent by changing total physical thickness d and birefringence n because postpone (d Δ n), the length of delay of this first phase difference compensating layer is set at-600nm.

It below is additional explanation to first phase difference compensating layer.Be known that lamination comprises having refractive index n respectively ₁, n ₂With the film of physics film thickness a, b, these films alternately pile up with the gradient (a+b) that is shorter than wavelength basically, thereby this lamination becomes the form birefringent body that has negative birefringence Δ n.When the vertical enter mode two-fold of electromagnetic wave beam, only exist electric field to be parallel to the TE ripple of the plane vibration of each layer.Therefore, the form birefringent body can not show birefringence properties.Yet, when electromagnetic wave enters into each lamination surface that comprises multilayer sideling, exist electric field to be parallel to the TE wave component of plane vibration of each layer and electric field TM wave component perpendicular to the plane vibration of each layer, and their effective refractive index N _TE, N _TMBe different.This effective refractive index N _TE, N _TMAs follows:

$N_{\mathrm{TE}}={\{({\mathrm{an}}_1^2+{\mathrm{<figure-callout\; id="2"\; label="bn"\; filenames="A20058004312600431.png,A20058004312600441.png"\; state="\{\{state\}\}">bn</figure-callout>}}_2^2)/(a+b)\}}^{(1/2)}$

$N_{\mathrm{TM}}={[(a+b)/\{(a/{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="A20058004312600441.png,A20058004312600542.png"\; state="\{\{state\}\}">n</figure-callout>}}_1^2)+(b/{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A20058004312600431.png,A20058004312600441.png"\; state="\{\{state\}\}">n</figure-callout>}}_2^2)\left\}\right]}^{(1/2)}$

Effective refractive index N _TEAnd N _TMDifference be the factor that causes birefringence properties, and birefringence n is calculated by formula:

Δn＝N _TE-N _TM

Top formula explanation birefringence n can be by selecting the refractive index n of sedimentary deposit L1, L2 ₁And n ₂And their physics film thickness a and b determine.Further, total physics film thickness d can determine by the lamination number that changes sedimentary deposit L1, L2.Therefore, by selecting to have the deposition materials of optical clarity and outstanding sedimentation Stability, and design this film, the delay of first phase difference compensating layer (d Δ n) can be near the length of delay (d Δ n) of TN liquid crystal cell _LC

First phase difference compensating layer is formed on the glass substrate as mentioned above, then this glass substrate is taken out in vacuum chamber.Clean this glass substrate once more with acetone, and dry fully, place it in then in the deposition device shown in Figure 5.Second phase difference compensating layer that has two films is deposited, so that deposition surface is the uppermost skim of first phase difference compensating layer.First tunic is oblique deposited film S1, and wherein, azimuth angle alpha is-137 °, and polar angle β is-45 °, postpones (d Δ n) _S1Be 150nm, second tunic is oblique deposited film S2, and wherein, azimuth angle alpha is-45 °, and polar angle β is 33 °, postpones (d Δ n) _S2Be 180nm.After under monitoring, forming second phase difference compensating layer from the data conditions of elliptical polarized light meter 32 and film thickness monitor 31, sample is taken away from deposition device shown in Figure 5, and be placed on be used to carry out conventional before in the deposition device of deposition (normal front deposition), thereby form and three layers of identical anti-reflective film of three layers of anti-reflective film of formation at first.

As oblique deposited film S1 that is used for second phase difference compensating layer and the deposition materials of S2, can use the TiO that is mixed with 10 percentage by weights ₂ZrO ₂In order to form film, vacuum chamber is applied to application of vacuum up to 1 * 10 ^-4Pa, oxygen is put into vacuum chamber up to 1 * 10 then ^-2Pa, thereby abundant this film of oxidation.In aforesaid experiment 1, the structure and parameter of first and second phase difference compensating layers of acquisition is illustrated in table 1.

[form 1]

Experiment 1		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S2	-45	33	180
S1	-137	45	150
				First phase difference compensating layer					-600
Glass substrate

When the phase compensator of experiment 1 was applied to the TN liquid crystal cell, contrast curves became at the state shown in Figure 11.Obviously, the visual angle attribute of the visual angle attribute of the contrast curves in Figure 11 from Figure 10 improves and obtains, and Figure 10 shows the contrast curves of TN liquid crystal cell itself.

Because when the optical axis vector P1 of oblique deposited film S1 is projected on the deposition surface orthogonally, the X and Y coordinates value is (83,-83), and when the optical axis vector P2 of oblique deposited film S2 is projected on the deposition surface orthogonally, the X and Y coordinates value is (110,-102), the X and Y coordinates value of the resultant vector A of optical axis vector P1, P2 becomes (27 ,-183).Therefore, condition formula 1 is met.In addition, because the delay of first phase difference compensating layer (d Δ n) is-600nm, this value be in when the delay of TN liquid crystal cell is 558nm the minimum value in the condition formula 2 for-1118nm in the scope of maximal value-279nm, so condition formula 2 also is met.

(experiment 2)

According to experiment 1 identical mode, form the sample of experiment 2.The structure of TN liquid crystal cell and anti-reflecting layer 1 is identical with experiment, and first and second phase difference compensating layers membrane structure be different with testing 1.The structure and parameter of first and second phase difference compensating layers is illustrated in form 2.In experiment 2, second phase difference compensating layer has trilamellar membrane, and the azimuth angle alpha of every tunic is rotated with same direction.Therefore, optical axis vector P1 sequentially rotates on deposition surface with counter clockwise direction in a spiral manner to P3.

[form 2]

Experiment 2		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S3	-15	44	70
S2	-41	27	80
				S1		-127	45	190
First phase difference compensating layer									-370
				Glass substrate

The contrast curves of experiment 2 is shown in Figure 12.High-contrast area becomes greater than the high-contrast area of experiment 1, and compares with experiment 1, to the dependence step-down at visual angle.Tiltedly the X and Y coordinates value of deposited film S1 to the optical axis vector P1 of S3 to the resultant vector A of P3 becomes (18 ,-196).Because the delay of first phase difference compensating layer is-370nm that condition formula 1 and condition formula 2 all are met.

(experiment 3)

In experiment 3, the delay of first phase difference compensating layer is-440nm, and second phase difference compensating layer and test 2 and identically have three layers.The structure and parameter of first and second phase difference compensating layers is illustrated in form 3.In experiment 3, opposite with experiment 2, the 3rd layer of second phase difference compensating layer with first and second layers in each the opposite direction rotation of sense of rotation of azimuth angle alpha, in experiment 2, optical axis vector P1 sequentially rotates by spiral way with a direction to P3.

[form 3]

Experiment 3		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S3	-44	42	110
S2	-22	44	50
				S1		-131	45	180
First phase difference compensating layer									-440
				Glass substrate

The contrast curves of experiment 3 is shown in Figure 13.The visual angle attribute still keeps finely.Tiltedly the X and Y coordinates value of deposited film S1 to the optical axis vector P1 of S3 to the resultant vector A of P3 becomes (2 ,-223).Because the delay of first phase difference compensating layer is-440nm that condition formula 1 and condition formula 2 all are met.Note, do not consider the situation that three optical axis vectors of the trilamellar membrane of second phase difference compensating layer not do not rotate in the mode of spiral, from between Figure 12 and 13 more as can be seen, although change has taken place the shape of correlation curve, what influence the visual angle attribute is not had.

(experiment 4)

In experiment 4, the delay of first phase difference compensating layer is-500nm, and second phase difference compensating layer has four layers.The structure and parameter of first and second phase difference compensating layers is illustrated in form 4.The oblique deposited film S1 of second phase difference compensating layer is confirmed as making the azimuth angle alpha of every tunic to rotate with equidirectional to S4.Therefore, optical axis vector P1 sequentially rotates by counter clockwise direction in a spiral manner to P4.

[form 4]

Experiment 4		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S4	-138	40	104
S3	-116	24	214
				S2		-16	24	72
S1	22	24	104

First phase difference compensating layer				-500
					Glass substrate

The contrast curves of experiment 4 is shown in Figure 14.The visual angle attribute improves.Tiltedly the X and Y coordinates value of deposited film S1 to the optical axis vector P1 of S4 to the resultant vector A of P4 becomes (32 ,-77).Because the delay of first phase difference compensating layer is-500nm that condition formula 1 and condition formula 2 all are met.

(experiment 5)

In experiment 5, the delay of first phase difference compensating layer is-470nm, and second phase difference compensating layer has four layers.The structure and parameter of first and second phase difference compensating layers is illustrated in form 5.The oblique deposited film S1 of second phase difference compensating layer to S4 each azimuth angle alpha with experiment opposite direction rotation in 4.Therefore, optical axis vector P1 is to P4 rotation in a spiral manner in the direction of the clock sequentially.

[form 5]

Experiment 5		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S4	5	40	106
S3	-40	45	40
				S2		-117	44	120
S1	-130	35	130
				First phase difference compensating layer					-470
Glass substrate

The contrast curves of experiment 5 is shown in Figure 15.Good visual angle attribute is obtained.Tiltedly the X and Y coordinates value of deposited film S1 to the optical axis vector P1 of S4 to the resultant vector A of P4 becomes (8 ,-191).Because the delay of first phase difference compensating layer is-470nm that condition formula 1 and condition formula 2 all are met.Can find, when determining according to example 4 when the hand of spiral of the optical axis vector of each film in second phase difference compensating layer and determining, all can obtain good visual angle attribute according to example 5.But this does not also mean that the hand of spiral of optical axis vector does not influence the visual angle attribute.When the hand of spiral changes, comprise the azimuth angle alpha and the polar angle β of every tunic, the optimum value of these group data of the delay of the delay of every tunic and first phase difference compensating layer also can change in second phase difference compensating layer.

(experiment 6)

In experiment 6, the delay of first phase difference compensating layer is-350nm, and second phase difference compensating layer has five layers.The structure and parameter of first and second phase difference compensating layers is illustrated in form 6.Tiltedly deposited film S1 rotates in the mode of spiral to P5 to the optical axis vector P1 of S5.

[form 6]

Experiment 6		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S5	-130	45	200
S4	-116	43	80
				S3		-46	45	70
S2	-10	45	50
				S1		30	45	80
First phase difference compensating layer									-350
				Glass substrate

The contrast curves of experiment 6 is shown in Figure 16.Good visual angle attribute is obtained.Tiltedly the X and Y coordinates value of deposited film S1 to the optical axis vector P1 of S5 to the resultant vector A of P5 becomes (6 ,-239).Because the delay of first phase difference compensating layer is-350nm that condition formula 1 and condition formula 2 all are met.

As test as described in 1 to 6, the delay of first phase difference compensating layer and the combination of suitable structure with second phase difference compensating layer of a plurality of films can compensate in the TN liquid crystal cell dependence to the visual angle effectively.Especially, the suitable film configuration of second phase difference compensating layer can be subjected to the influence of the delay of first phase difference compensating layer, this means to have the incompatible acquisition optimal viewing angle of a large amount of parameter group attribute.However, top experiment combination that first and second phase difference compensating layers are shown need be satisfied condition formula 1 and 2 at least.

Basically, the delay numerical value of first phase difference compensating layer need be determined according to the positive birefringence of liquid crystal molecule and the thickness of liquid crystal layer.But, in the TN of some kinds liquid crystal cell, becoming when vertical orientated when applying the voltage liquid crystal molecule, the ratio of liquid crystal molecule is not a constant.Therefore, the length of delay of first phase difference compensating layer should be determined under the situation of the fluctuation range of considering this ratio.In addition, length of delay should be adjusted according to the positive birefringence of second phase difference compensating layer.

In addition, as mentioned above, the position of phase difference compensation of the present invention is not limited to light exit surface one side at the TN liquid crystal cell, also can be in its light incident surface one side.And first phase difference compensating layer and second phase difference compensating layer can form on glass substrate separately, and keep betwixt using under the situation of certain distance.Further, one of preferred embodiment is, be separately positioned in the substrate of the light incident surface of TN liquid crystal cell and a pair of polaroid on the light exit surface one of at least, the substrate that can be used as first phase difference compensating layer and/or second phase difference compensating layer is used.

When reference wavelength is set at that for example 550nm is used for forming first and second phase difference compensating layers, phase compensator of the present invention can be able to be applied on the panchromatic direct-view type LCD, this display has the veneer TN liquid crystal cell as display element.But,, more preferably provide the special structure of each film in the phase compensator according to the reference wavelength of the light of each color component because the birefringence effect of each is according to wavelength variations in liquid crystal molecule and the phase compensator.In this LCD, will be used for transmission usually and be incorporated into the TN liquid crystal cell as the miniature color filters of one of red, green and blue light of color light component.Therefore, preferably, use three kinds of phase difference compensations that have corresponding to the different membrane structures of each color filters.

The membrane structure that changes phase compensator according to the reference wavelength of each color light component can be applied to effectively and comprise three three-chip type liquid crystal projection apparatus corresponding to the TN liquid crystal cell of each color light component.The structure of three-chip type liquid crystal projection apparatus schematically illustrates in Figure 17.

In Figure 17, three liquid crystal cell 50R, 50G, 50B show to have according to red respectively, the monochrome image of the transmission density of the image of each color component in the green and blueness.Emission light from light source 52 is got rid of ultraviolet and infrared component by intercepting wave filter 53, and becomes the white light that comprises red, green and blue light.When white light is propagated along lighting optical axis (dotted line on accompanying drawing) and enter glass rod 54 as integrator.Because the plane of incidence of glass rod 54 be positioned at light source 52 the parabolic reflector focal position near, so from the intercepting wave filter 53 white light at the plane of incidence that does not have to enter under the big loss glass rod 14.

After passing glass rod 54, white light is by relay lens 55 and collimation lens 56 collimations.Quilt is towards dichromatic catoptron 58R on catoptron 57 for white light behind the collimation, and this dichroic mirror 58R is transmit red light and reflect blue and green glow.The liquid crystal cell that is used for red image 50R is illuminated from behind by the ruddiness that reflects on catoptron 59.Blue light that reflects on dichroic mirror 58R and green glow arrive a dichroic mirror 58G, wherein, have only green glow to be reflected.Green glow by reflection on dichroic mirror 58G illuminates the liquid crystal cell that is used for green image 50G from behind.The blue light of reflection illuminates the liquid crystal cell that is used for blue image 50B from behind on catoptron 58B, 60.

Liquid crystal cell 50R, 50G, 50B comprise TN liquid crystal cell layer, and show the image of red, green and blue look opacity (density) respectively.Color recombination prism 64 is positioned at center from color recombination prism 64 to the identical position of the optical range of liquid crystal cell 50R, 50G, 50B.Color recombination prism 64 has dichromatism plane 64a, the 64b of two difference reflect red and blue image light, so that redness, green and blue image light are mixed into full-colour image light.Projection lens system 65 from the exit plane of color recombination prism 64 to the direction de projection optical axis of screen 70.The focus in object space of projection lens system 65 is on the exit plane of liquid crystal cell 50R, 50G, 50B.The rear focus of projection lens system 65 is on screen 70.Therefore, the full-colour image light from color recombination prism 64 focuses on the screen 70 by projection lens system 65.

Preceding polaroid 66R, 66G, 66B are separately positioned on the front of the plane of incidence of liquid crystal cell 50R, 50G, 50B as the polarizer. Phase difference compensation 67R, 67G, 67B and be disposed in exit plane one side of liquid crystal cell 50R, 50G, 50B as rear polarizer 68R, 68G, the 68B of analyzer.The polarization direction of preceding polaroid 66R, 66G, 66B and rear polarizer 68R, 68G, 68B is vertical (cross Nicols configuration) mutually.Among phase difference compensation 67R, 67G, the 67B each comprises first phase difference compensating layer and second phase difference compensating layer, is used for compensating respectively the phase differential of every kind of color of liquid crystal cell 50R, 50G, 50B, as mentioned above.

Though liquid crystal cell 50R, 50G, 50B have identical TN liquid crystal cell, be known that delay (d Δ n) _LCGenerally be to change according to wavelength.Image 18 shows the wavelength dependence that thickness is the TN liquid crystal cell of 4.5 μ m.Birefringence n is according to wavelength variations, and delay (d Δ n) _LCAlso be according to wavelength variations.In this width of cloth figure, the meaning of Re is the effective delay when the ratio that becomes vertical orientated liquid crystal molecule according to the voltage that applies is 70%.The first above-mentioned phase difference compensating layer is by effective delay Re compensation positive phase difference.The ratio of noting vertical orientated liquid crystal molecule is not limited to 70%, and this ratio can be along with multiple factors vary, such as structure, thickness, opacity and the saturation voltage value of TN liquid crystal cell.

In order to compensate effective delay Re of TN liquid crystal cell effectively, first phase difference compensating layer is made up of 40 TiO2 films and 40 SiO2 films of alternately being stacked on the substrate, and wherein, every layer of TiO2 film has the thickness of 30nm, and every layer of SiO2 film has the thickness of 20nm.As shown in figure 19, the absolute figure of the negative delay of first phase difference compensating layer (d Δ n) depends on wavelength, and this is because the refractive index of TiO2 film and SiO2 film has wavelength dependence.First phase difference compensating layer is designed to compensate effectively the phase differential at the 550nm wavelength place that has high-visibility in the visible region.But, as shown in figure 20,, can not carry out suitable phase difference compensation in short wavelength one side.

Consider the problems referred to above, in the present invention, the thickness of first phase difference compensating layer of each phase difference compensation 67R, 67G, 67B can comprise the feature of first phase difference compensating layer of the deposited film that thickness is enough littler than wavelength by utilization, and change according to each Color Channel.Just, negative birefringence Δ n by two kinds of deposited films refractive index and the ratio of its thickness determine that and length of delay is controlled by changing total film thickness of multiplying each other with birefringence n (each of piling up layer number).Figure 21 shows an example.

In this example, it is blue that the thickness of first phase difference compensating layer is respectively, green and ruddiness change.TiO2 film in deposited film and SiO2 film are 20nm and 30nm at the physical thickness of each color channel.But, according to being 450nm as reference wavelength λ, the delay of TN liquid crystal cell 413nm during promptly near the centre wavelength of blue component light, first phase difference compensating layer that is used for blue light has total film thickness d of 72 layers of stacked film and 1.8nm.In an identical manner, when reference wavelength λ was the 550nm of green component light, first phase difference compensating layer that is used for green light had total film thickness d of 80 layers of stacked film and 2.0 μ m.Also have when reference wavelength λ is the 650nm of red component light, first phase difference compensating layer that is used for red light has total film thickness d of 82 layers of stacked film and 2.1 μ m.

As a result, as represented in Figure 22, prove that the delay of every kind of Color Channel of liquid crystal cell 50R, 50G, 50B can well be compensated according to the wavelength separately of every kind of color of light.When the pure blue background was projected on the screen 70, the whole zone of liquid crystal cell 50B was in bright state, and the whole zone of liquid crystal cell 50R, 50G is in dark state.During this time, by the positive phase difference that the birefringence effect of vertical orientated liquid crystal molecule causes owing to applied saturation voltage in liquid crystal cell 50R, 50G, can be compensated effectively by negative the delay, negative delay wherein is to be obtained by first phase difference compensating layer that is used for ruddiness and green glow that provides in phase difference compensation 67R and 67G respectively.Therefore, from producing hardly as the polaroid 68R of analyzer and the diverging light of 68G, this has realized the projection in the pure blue background that does not have the distinctness under the fuzzy situation.

Because identical reason is when white light is projected onto the whole zone of screen and brought up to 700: 1 when the whole zone of screen is in dark state contrast between the two from 500: 1.In addition, in order to throw general full-colour image, the sharpness of image can improve by the black that fills up.Notice that as seen from Figure 22, the wavelength dependence of first phase difference compensating layer that is used for green glow and ruddiness is lower than the wavelength dependence that is used for blue light.Correspondingly, possible is that first phase difference compensating layer with identical total film thickness can be respectively applied for green glow and ruddiness.In this case, preferably, determine total film thickness with reference to the 600nm wavelength.

As mentioned above, when phase difference compensation of the present invention is applied to three-chip type color liquid crystal projector, effectively adjust this first phase difference compensating layer total film thickness at per two Color Channels at least.The delay (d Δ n) of liquid crystal cell 50R, 50G, 50B has only been considered in above-mentioned explanation _LCWavelength dependence.But second phase difference compensating layer in each of phase difference compensation 67R, 67G, 67B also has different reference wavelengths in each Color Channel, and has the ad hoc structure corresponding to each reference wavelength.Second phase difference compensating layer has identical just delay with liquid crystal molecule.Therefore, preferably in order to adjust, the total film thickness of first phase difference compensating layer increases.Note, even adjust, the negative delay of first phase difference compensating layer of each Color Channel formula 2 that also can satisfy condition.

Possiblely be that above-mentioned phase difference compensation 67R, 67G, 67B lay respectively among liquid crystal cell 50R, 50G, the 50B light incident surface of each.In addition, have a kind of situation, that is, in liquid crystal cell, use the micro-lens array comprise a plurality of micro lens, one of them micro lens corresponding to being used for a pixel so that improve aperture efficiency.In such liquid crystal cell, usually, the incident angle that enters the illumination light of liquid crystal layer distributes wideer than the incident angle distribution of the illumination light that enters micro-lens array.Therefore, for compensation of phase is poor effectively, preferred phase difference compensation 67R, 67G, 67B lay respectively among liquid crystal cell 50R, 50G, the 50B light exit surface of each.

Expectation be, wherein as described above first and second phase difference compensating layers have been carried out phase difference compensation 67R, the 67G, the 67B that optimize by using, can make contrast on screen 70 become 1000: 1 or higher.In addition, owing to phase difference compensation is only formed by inorganic material, so there is not the problem of thermal resistance and light resistance.Therefore, phase difference compensation of the present invention can be able to be effectively applied to the product such as the family expenses rear-projection TV that can use for a long time.

Phase difference compensation and the liquid crystal projection apparatus of first embodiment of the present invention have been described before this.As for the substrate that is used to form phase difference compensation, some transparent inorganic materials can equally with glass substrate be used.In order to be applied in the liquid crystal projection apparatus, preferable material is Sapphire Substrate and the quartz substrate with high heat conductance.In addition, possible is that first phase difference compensating layer and second phase difference compensating layer are respectively formed on the independent transparent substrates.And lens, prism, the substrate of the wave filter of some kinds and the liquid crystal cell in optical system can be as the transparent substrates of phase difference compensating layer.

Next, the phase difference compensation of second embodiment of the present invention is described.Note, the element in second embodiment, if also in first embodiment, be used, then be endowed with first embodiment in identical Reference numeral, and omitted detailed explanation to these elements.As shown in figure 23, phase difference compensation 102 is arranged between polaroid 103 and 104, and the direction that is directed to perpendicular to optical axis 105 of these parts 102 to 104. Polaroid 103 and 104 is the cross Nicols configuration, and wherein the polaroid 103 and 104 the axis of homology are in the right angle.When illumination light 107 included only the light beam that is parallel to optical axis 105, even without phase difference compensation 102, light was not also from dispersing out at the polaroid 104 of light outgoing one side.But when illumination light 107 comprises the light beam that is not parallel to optical axis 105, if there is not phase difference compensation 102, light will be dispersed out from polaroid 104.By the use of phase difference compensation 102, comprise the light time that favours optical axis 105 even work as illumination light, also can significantly reduce diverging light 108 from polaroid 104.

As shown in figure 24, phase difference compensation 102 has and the 6 essentially identical structures of the phase difference compensation in Fig. 2.But as shown in figure 25, second phase difference compensating layer 114 comprises that four kinds of oblique deposited film S1 are to S4.In such an embodiment, the first oblique deposited film S1 is stacked on first phase difference compensating layer 12.Yet, possible is that the position of first and second phase difference compensating layers 12 and 114 is commutative, thereby the first oblique deposited film S1 is formed on the glass substrate 10, second to the 4th layer of oblique deposited film S2 sequentially is formed on the first oblique deposited film S1 to S4, and first phase difference compensating layer 12 is formed on the 4th layer of oblique deposited film S4 then.In addition, also possible is that first phase difference compensating layer 12 and second phase difference compensating layer 114 are respectively formed at the both sides of glass substrate 10, and anti-reflecting layer 15 and 16 is respectively formed at the outermost layer of first and second phase difference compensating layers 12 and 114.

Different with L2 with the deposited film L1 of first phase difference compensating layer 12 is that the oblique deposited film S1 of second phase difference compensating layer 114 is deposited with the tilted direction towards deposition surface S0 to S4.Deposited film S1 has microcosmic cartridge by diffusion of volatile treating agent M1 respectively to M4 to each layer among the S4, and they extend sideling to its deposition direction.Tiltedly deposited film S1 can show the form birefringent effect to the independent level of each layer conduct among the S4, and can be as the O-plate with positive birefringence.But tiltedly deposited film S1 has showed being parallel to the optical isotropy of cartridge by diffusion of volatile treating agent M1 to the light of the direction of M4 to S4.Correspondingly, optical axis enters into film S1 to S4, and is that 1 medium (such as air) and film S1 reflect to the interface between the S4 in refractive index, and this optical axis is corresponding to the direction of cartridge by diffusion of volatile treating agent M1 to M4 then.Just, optical axis with the angle tilt of the refractive index of an oblique deposited film of basis in the direction of cartridge by diffusion of volatile treating agent.Tiltedly deposited film S1 is not parallel to deposition surface S0 to the deposition direction of S4, thereby and difference cartridge by diffusion of volatile treating agent M1 is also different mutually to the direction of M4 mutually.Correspondingly, when optical axis was projected on the deposition surface S0 orthogonally, every tunic S1 also differed from one another to the position angle of the optical axis of S4.

Tiltedly deposited film S1 can be the same with second phase difference compensating layer 14 of phase difference compensation 6 among first embodiment to S4, forms by the deposition device shown in Fig. 5.As shown in figure 26, when the deposition direction P towards deposition surface S0 is projected on the X-Y coordinate on deposition surface S0 orthogonally, this deposition direction P can be represented that wherein α begins to measure from X-axis with counterclockwise direction by azimuth angle alpha and polar angle β, and β begins to measure from the Z axle.Polar angle β does not have under the situation of positive negative direction from the pitch angle that the Z axle begins, and azimuth angle alpha has the directivity with reference to X-axis.The direction of X-axis is determined to be the angle that becomes δ=45 ° with polaroid 103 and 104 axis of homology 103a with 104a.The direction of X-axis is shared at oblique deposited film S1 in S4.Note, as shown in figure 33, because this visual angle attribute to the polaroid 3,4 under the cross Nicols configuration has 90 ° rotational symmetry, so the direction of X-axis can not be restricted.

Tiltedly deposited film S1 each layer in the S4 is roughly corresponding to its each deposition direction.Tiltedly deposited film S1 can demonstrate the form birefringent effect to the independent one deck of each layer conduct among the S4, and can be used as the O-plate with positive birefringence.As mentioned above, say exactly that tiltedly the optical axis of deposited film S1 each layer in the S4 is not fully identical with deposition direction P.But, because the effect that is caused by small misalignment can be left in the basket in actual use, so the direction of the optical axis of the oblique deposited film of each layer can be counted roughly by azimuth angle alpha and polar angle β.

In order to form second phase difference compensating layer 114, can determine azimuth angle alpha and the polar angle β of the oblique deposited film S1 of each layer to S4.The oblique deposited film S1 of each layer is given to the refractive index of the deposition materials of S4, and the oblique deposited film S1 of each layer supposed corresponding approx its deposition direction to the optical axis direction of S4.Therefore, with tiltedly deposition direction is the same, the oblique deposited film S1 of each layer can be set on the expectation value to the optical axis of S4.The inventor utilizes the oblique deposited film S1 of each layer to the azimuth angle alpha of S4 and the control of polar angle β, has produced to comprise the different samples of oblique deposited film S1 to second phase difference compensating layer 114 of S4, and has estimated the view angle dependency of each sample.As a result, confirm that the visual angle attribute of second phase difference compensating layer 114 is improved, particularly ought comprise three layers or more tiltedly deposited film, and the two-layer optical axis that projects to separately on the deposition surface wherein separates 180 ° each other.

Note in order to improve the visual angle attribute, except azimuth angle alpha and polar angle β, also having various parameter, such as the film thickness and the delay of the oblique deposited film of each layer.Though the relation between these parameters and the visual angle attribute checked up hill and dale is unusual difficulty, the experiment of description after a while 7 is provable to have the outstanding visual angle attribute that is used for actual purpose.As for the deposition materials of second phase difference compensating layer 114, identical with the deposition materials of first phase difference compensating layer 12, can use the material that has in the form of oblique deposited film with the sufficient optical transparence of Wavelength-independent, for example TiO ₂, SiO ₂, ZrO ₂And Ta ₂O ₃

(experiment 7)

After this, the concrete experiment of phase difference compensation 102 of the present invention is described.Identical with experiment 1 to 6, after forming anti-reflecting layer, in vacuum chamber, glass substrate is overturn from the inside to surface, thereby be formed on first phase difference compensating layer shown in Fig. 2.First phase difference compensating layer is the C-plate of bearing, and its delay (d Δ n) is-341nm.

The glass substrate that is formed with first phase difference compensating layer 12 as mentioned above on it is taken out from vacuum chamber.Clean glass substrate with acetone, and dry fully, then it is arranged in the deposition device shown in Figure 5.Deposition has second phase difference compensating layer of four tunics, thereby this deposition surface is the top skim of first phase difference compensating layer.First tunic is oblique deposited film S1, and wherein azimuth angle alpha is-46.5 °, and polar angle β is 14 °, and delay (d Δ n) _S1Be 106nm.Second tunic is oblique deposited film S2, and wherein azimuth angle alpha is 135 °, and polar angle β is 45 °, and delay (d Δ n) _S2Be 111nm.Trilamellar membrane is oblique deposited film S3, and wherein azimuth angle alpha is-42 °, and polar angle β is 10 °, and delay (d Δ n) _S3Be 87nm.The 4th tunic is oblique deposited film S4, and wherein azimuth angle alpha is-45 °, and polar angle β is 12.5 °, and delay (d Δ n) _S4Be 88nm.Comprise that in formation oblique deposited film S1 is after second phase difference compensating layer of S4, sample is taken away from the deposition device shown in Fig. 5, and with its be arranged on be used for finishing conventional before the deposition device of deposition, thereby form the three layer anti-reflective film identical with anti-reflective film shown in Figure 2 15.

As for the oblique deposited film S1 of second phase difference compensating layer 114 deposition materials to S4, can use with percentage by weight is 10 TiO ₂The ZrO that mixes ₂In order to form film, vacuum chamber is applied application of vacuum up to 1 * 10 ^-4Pa sends into vacuum chamber up to 1 * 10 with oxygen then ^-2Pa, thus make the abundant oxidation of this film.In the experiment 7 of Miao Shuing, the structure and parameter of first and second phase difference compensating layers of acquisition is illustrated in form 7 in the above.

[form 7]

Experiment 7		Azimuth angle alpha °	Polar angle β °	(dΔn) (nm)
					Second phase difference compensating layer	S4	-45	12.5	88
S3	-42	10	87
				S2		135	45	111
S1	-46.5	14	106
				First phase difference compensating layer					-341

About every layer of oblique deposited film Si (i=1 to 4), determine optical axis vector Pi according to deposition direction P, this deposition direction P is determined by following parameter: azimuth angle alpha and polar angle β, and by the film thickness of oblique deposited film Si and the delay (d Δ n) of birefringence definition _S1Usually, optical axis vector Pi is to postpone (d Δ n) _Si, azimuth angle alpha _iWith polar angle β _iCombination illustrate as follows:

Pi(x，y，z)＝((dΔn) _Si×cosα _i×tanβ _i，

(dΔn) _Si×sinα _i×tanβ _i，(dΔn) _Si).

Calculate projection vector Ai, this projection vector Ai be rectangular projection as shown in figure 26 to X-Y plane on optical axis vector Pi.Result of calculation is as follows:

A ₁(x，y)＝(18.29，-19.35)

A ₂(x，y)＝(-78.49，-78.49)

A ₃(x，y)＝(11.64，-10.48)

A ₄(x，y)＝(13.69，-13.69)

Figure 27 is the diagram of these result of calculations.

As what from form 7 and Figure 27, find out, projection vector A ₁To A ₄Feature be each projection vector A ₂And A ₄At interval 180 ° each other of azimuth angle alpha, this azimuth angle alpha equals the position angle of the optical axis of every layer of oblique deposited film approx.In order to design second phase difference compensating layer 114, might change following these parameters: the number of oblique deposited film, the thickness of every tunic, position angle of optical axis or the like.By estimating these examples and calculating membrane structure, can find, as described above, second phase difference compensating layer 114 that uses with first phase difference compensating layer 12 comprises three layers or more tiltedly deposited film, and wherein two-layer at least all have separately separate 180 ° position angle each other.Notice that the position angle of optical axis can be approximately the position angle of oblique deposited film direction.In addition, in this experiment, the direction correspondence of the azimuth angle alpha of every layer of oblique deposited film S2, S4 is in the direction of the axis of homology 103a of the polaroid 103 of light incident surface.

When the phase difference compensation 102 of experiment 7 was disposed between the polaroid 103,104 as shown in figure 23, light covered attribute as shown in figure 28.In the drawings, though kept view angle dependency, reduced the brightness of the light that leaks from the exit surface of polaroid 104 generally.The light that is used for the sample of comparison covers attribute as shown in figure 29.In this comparative sample, exist to postpone for first phase difference compensating layer 12 of-220nm and comprise second phase difference compensating layer 114 of the oblique deposited film of individual layer, wherein the deposition position angle of deposited film is 135 °, postpones to be 413nm.As for comparative sample, what know is that as first phase difference compensating layer of negative C-plate and the phase difference compensation of the combination of second phase difference compensating layer of positive O-plate, this light to polaroid that can improve under the cross Nicols configuration covers attribute.But verifiable is that the phase difference compensation of experiment 7 can improve light effectively and cover attribute.

When the design phase difference compensation that comprises first phase difference compensating layer 12 and second phase difference compensating layer 114 of the present invention, owing to there are many parameters, for example, the birefringence and the thickness of each tunic in the quantity of the delay of determining by the birefringence of each tunic in first phase difference compensating layer 12 and thickness, the film in second phase difference compensating layer 114, the position angle (the tiltedly position angle of deposition) of optical axis, second phase difference compensating layer 114, thereby cover attribute in order to obtain preferred light, can there be a large amount of parameter combinations.But, be clear that, when first phase difference compensating layer 12 comprises three or more oblique deposited films, and at least wherein two-layer have the position angle when separating 180 ° optical axis (tiltedly the position angle of deposition is 180 °) each other separately, can improve light effectively and cover attribute.

As shown in figure 30, preferably, phase difference compensation 102 is applied on the LCD.As for the liquid crystal cell that is used for display image, TN liquid crystal cell 106 is used.Phase difference compensation 102 of the present invention is inserted between the polaroid 103 and TN liquid crystal cell 106 of light incident side.At the polaroid 103 of light incident side with at the polaroid 104 of light exit side is the cross Nicols configuration, and wherein the direction of the axis of homology of two polaroids is with 90 ° of intersections, so that this LCD is used under the conventional white mode.Illumination light 134 is polarized sheet 103 and converts linearly polarized photon to, and passes phase difference compensation 102, TN liquid crystal cell 106 and polaroid 104, becomes image light 135 and disperse.When TN liquid crystal cell 106 is in dark state, even illumination light 134 comprises the amount of lumens that is not parallel to optical axis 105, also can prevents the generation of leak light, and can cover attribute and visual angle attribute by the good light of performance acquisition of phase difference compensation 102.

In this example, consider in TN liquid crystal cell 106, to be included in this birefringence, be necessary the length of delay of first phase difference compensating layer 12 in the control phase difference compensator 102 liquid crystal molecule between the transparent substrates.Just, except compensation enters from oblique incidence the phase differential of light beam of polaroid 103, first phase difference compensating layer 12 also needs to compensate ordinary light that the birefringence by the liquid crystal molecule in the TN liquid crystal cell 106 produces and the phase differential between the unusual light.The compensativity of phase difference compensation can be controlled by the thickness according to THICKNESS CONTROL first phase difference compensating layer 12 of the liquid crystal cells in the TN liquid crystal cell 106.

As shown in Figure 31, preferably, phase difference compensation 102 is applied in the abaxile LCD, this abaxile LCD has the reflection-type TN liquid crystal cell 136 that is used for the image demonstration.In this reflection-type TN liquid crystal cell 136, the back side of liquid crystal cells is reflecting surface, and incident light axis 105a and emergent light axis 105b are not concentric.Transmission is passed the illumination light 134 of polaroid 103 and is passed liquid crystal cells as linearly polarized photon.Then, thus incident light is reflected on reflecting surface and passes liquid crystal cells once more and forms the light disperse.Consider the use under the white mode of routine, the thickness of liquid crystal cells is determined to be and makes that the polarization of incident light direction has been changeed 90 ° when light becomes diverging light when reflection-type TN liquid crystal cell 136 is in dark state.In addition, be under the cross Nicols configuration at the polaroid 103 of light incident side with at the polaroid 104 of light exit side.

Still in the abaxile LCD, when reflection-type TN liquid crystal cell 136 is in dark state, utilizes the performance of phase difference compensation 102 can avoid and obtain the visual angle attribute from the generation of the leak light of polaroid 104.Identical with example in Figure 30 is, in this example, considers the birefringence of the liquid crystal molecule in the reflection-type TN liquid crystal cell 136, is necessary the length of delay of first phase difference compensating layer 12 in the control phase difference compensator 102.Note, when controlling the thickness of first phase difference compensating layer 12, be necessary to consider that the optical path length in liquid crystal cells is the twice of liquid crystal cell thickness in the reflection-type TN liquid crystal cell 136.

The reference wavelength of the phase difference compensation of second embodiment of the present invention for example is arranged on 550nm when forming first and second phase difference compensating layers, this phase difference compensation can be applied in the panchromatic direct view liquid crystal, and this panchromatic direct view liquid crystal has the TN liquid crystal cell veneer as display element.Still in this case, preferably, provide three types phase difference compensation with different membrane structures, thus corresponding with every kind of color filters in being included in the TN liquid crystal cell.

In addition, can be applied to effectively in the three-chip type liquid crystal projection apparatus according to the membrane structure of the wavelength shift phase difference compensation of every kind of color light component, this projector comprises three TN liquid crystal cells corresponding to every kind of color light component.The structure of three-chip type liquid crystal projection apparatus is schematically shown in Figure 32.

The structure of the liquid crystal projection apparatus that illustrates in Figure 32 is basically with identical at liquid crystal projection apparatus illustrated in fig. 17, but phase difference compensation 167R, 167G in the second embodiment of the present invention, 167B are provided at the light incident surface side of liquid crystal cell 50R, 50G, 50B respectively.As mentioned above, each among phase difference compensation 167R, 167G, the 167B all comprises first phase difference compensating layer and second phase difference compensating layer, is respectively applied for the phase differential of every kind of color of compensation liquid crystal cell 50R, 50G, 50B.In addition, phase difference compensation 167R, 167G, 167B utilize polaroid 66R, the 66G, 66B and polaroid 68R, 68G, the 68B that are under the cross Nicols configuration to improve the optical shielding property energy.

When the phase difference compensation among second embodiment of the present invention was applied to three-chip type color liquid crystal projector, first phase difference compensating layer was designed to identical with phase difference compensation among first embodiment.In addition, the phase difference compensating layer in each also is designed to have ad hoc structure corresponding to each Color Channel in phase difference compensation 167R, 167G, 167B.Second phase difference compensating layer has the just delay identical with liquid crystal molecule.Correspondingly, preferably, increase the total film thickness of first phase difference compensating layer in order to adjust.

What expect is that by phase difference compensation 167R, the 167G, the 167B that are optimized as mentioned above, the contrast on screen 70 becomes 1000: 1 or be higher by utilization first and second phase difference compensating layers wherein.In addition, because phase difference compensation is only formed by inorganic material, so there is not the problem of thermal resistance or light resistance.Therefore, phase difference compensation of the present invention can be applied in the various products of the family expenses back projection type TV that for example uses for a long time effectively.

Phase difference compensation in second embodiment has the analyzer that light covers attribute about the polarizer of generation linearly polarized photon with according to the polarisation of light direction, and the line lattice polarizer can be used with polaroid the samely.In addition, according to form identical mode by the multilayer deposited film, first phase difference compensating layer can be made up of the polymkeric substance that produces from short distance (short pitch) cholesteryl liquid crystal.Just, be well known that the layer that will have same structure with cholesteryl liquid crystal as negative C-plate, wherein, in this cholesteryl liquid crystal the spacing of spiral fashion liquid crystal molecule be optical wavelength 1/10 and 1/5 between, and its screw axis is vertical with substrate.For example, according to this layer of formation as described below.At first, the surface to substrate processes so that it has the orientation of the major axis that is parallel to liquid crystal molecule.Next, the cholesteryl liquid crystal with polymerizable molecules structure is applied on the substrate to form above-mentioned cholesteric structure.Then, thus with the photopolymerization process or similarly process be applied to and eliminate liquid on the cholesteryl liquid crystal.

In addition, positive C-plate can be able to be applied to first phase difference compensating layer.In this case, at first, the surface of substrate processed make it have a orientation perpendicular to the major axis of liquid crystal molecule.Next, the shaft-like liquid crystal monomer with polymerizable molecules structure is applied on the substrate to form the single domain alignment films.Then, thus with the photopolymerization process or similarly process be applied to and eliminate liquid on the single domain alignment films.

Identical with the phase difference compensation among first embodiment, about being used to form the substrate of second phase difference compensation among the embodiment, can use the same transparent inorganic material of using of some energy with glass substrate.Preferred material is Sapphire Substrate and the quartz substrate with high heat conductance, so that be applied in the liquid crystal projection apparatus.In addition, possible is that first phase difference compensating layer and second phase difference compensating layer are respectively formed on the independent transparent substrates.The substrate of the wave filter of lens, prism, some kinds and the liquid crystal cell in optical system all can be used as the transparent substrates that is used for phase difference compensating layer.

Industrial usability

The present invention is that advantageous applications is in the device that utilizes polarised light, particularly in the device relevant with liquid crystal.

Claims (21)

1. a phase difference compensation that is used in combination with the TN liquid crystal cells is used for compensating the light phase differential relevant with angle that passes described TN liquid crystal cells liquid crystal layer, and described phase differential is caused that by the birefringence of described liquid crystal layer described phase difference compensation comprises:

First phase difference compensating layer comprises multilayer film, and each layer in the wherein said multilayer film all is the form birefringent body that is formed by inorganic material, is used for compensating the phase differential that is caused by the vertical orientated liquid crystal molecule of liquid crystal layer; And

Second phase difference compensating layer comprises multilayer film, and each layer in the wherein said multilayer film all is the form birefringent body that is formed by inorganic material, is used for compensating the phase differential that the liquid crystal molecule by the liquid crystal layer hybrid orientation causes.

2. phase difference compensation as claimed in claim 1, in wherein said first and second phase difference compensating layers at least one deck comprise multilayer film, and each tunic in this multilayer film is all formed by vacuum deposition method.

3. phase difference compensation as claimed in claim 1, wherein said second phase difference compensating layer comprise the multiple oblique deposited film that piles up, and described oblique deposited film is different one of at least in the position angle of the deposition direction of deposition surface and polar angle.

4. the phase difference compensation described in claim 1, wherein said second phase difference compensating layer comprises three layers or the more multi-layered oblique deposited film that piles up.

5. the phase difference compensation described in claim 1, wherein said second phase difference compensating layer comprises a plurality of oblique deposited films that pile up,

And when the position angle of the deposition direction of each oblique deposited film is confirmed as with by the position angle of the given described liquid crystal molecule of the alignment films of described TN liquid crystal cells not simultaneously, determine each optical axis vector according to described position angle, polar angle and the delay of every layer of oblique deposited film, and the resultant vector A of described optical axis vector is projected on the deposition surface orthogonally, its X and Y coordinates value (Ax, Ay) satisfy following formula:

-200nm≤Ax≤200nm and

-500nm≤Ay≤0nm。

6. phase difference compensation as claimed in claim 1, the product (d Δ n) of the birefringence of the delay d Δ n of described first phase difference compensating layer and the liquid crystal layer of described TN liquid crystal cells and the thickness d of this liquid crystal layer _LCBetween relation as follows:

-2×(dΔn) _LC≤(dΔn)≤-0.5×(dΔn) _LC。

7. phase difference compensation as claimed in claim 1, wherein said first phase difference compensating layer is made up of two kinds of alternately laminated a plurality of deposited films with different refractivity, and the optical thickness of each layer in described a plurality of deposited film is 1/100 to 1/5 of a reference wavelength.

8. phase difference compensation as claimed in claim 1 also comprises the light incident surface side that is arranged on described phase difference compensation and/or the anti-reflecting layer on the light exit surface side.

9. LCD, this LCD comprises the TN liquid crystal cells and as any described phase difference compensation in the claim 1 to 8, described phase difference compensation is disposed in the light incident surface side and/or the light exit surface side of described TN liquid crystal cells.

10. liquid crystal projection apparatus, comprise the TN liquid crystal cells, as any described phase difference compensation in the claim 1 to 8, and be used for the light of described TN liquid crystal cells modulation is carried out projection lens projecting, described phase difference compensation is disposed in the light incident surface side and/or the light exit side of described TN liquid crystal cells.

11. liquid crystal projection apparatus as claimed in claim 10 comprises:

Three described TN liquid crystal cells, the wherein image of each in three color light components of each TN liquid crystal display demonstration; And

Three described phase difference compensations, one of them described phase difference compensation is corresponding to a described TN liquid crystal cells, described three phase difference compensations comprise two kinds of described phase difference compensations at least, and each reference wavelength according to every kind of described color light component in these two kinds of phase difference compensations has the delay that differs from one another.

12. the polarizer in cross Nicols configuration between the phase difference compensation that uses, comprising:

Transparent substrates, this transparent substrates and perpendicular perpendicular to the right optical axis of described polarizer;

First phase difference compensating layer is supported by described transparent substrates, and the optical axis of this first phase difference compensating layer and described transparent substrates are perpendicular; And

Second phase difference compensating layer, comprise three layers or more multi-layered stacked film, wherein every layer of stacked film all has the optical axis that favours described transparent substrates normal, rectangular projection on the described transparent substrates, the described optical axis direction of two stacked films separates about 180 ° each other in the described stacked film.

13. phase difference compensation as claimed in claim 12, wherein said first and second phase difference compensating layers are formed by inorganic material.

14. phase difference compensation as claimed in claim 13, the described stacked film in wherein said second phase difference compensating layer is oblique deposited film.

15. phase difference compensation as claimed in claim 13, wherein said first phase difference compensating layer is made up of two kinds of alternately laminated multilayer deposited films with different refractivity, and the optical thickness of each layer is 1/100 to 1/5 of a reference wavelength in the described multilayer deposited film.

16. phase difference compensation as claimed in claim 13, rectangular projection optical axis direction on the described transparent substrates, one of in the stacked film described in described second phase difference compensating layer is identical with direction at the axis of homology of the described polarizer of the light incident side of described phase difference compensation.

17. phase difference compensation as claimed in claim 12 also comprises: the anti-reflecting layer that is arranged on the light incident surface side and/or the light exit surface side of described phase difference compensation.

18. a light modulation system comprises as claim 16 or 17 described phase difference compensations and the liquid crystal cells of the light exit side of phase difference compensation as described in being arranged on.

19. a LCD comprises the transmission-type liquid crystal unit and as claim 16 or 17 described phase difference compensations, described liquid crystal cells is set at the light exit side of described phase difference compensation.

20. liquid crystal projection apparatus, comprise the transmission-type liquid crystal cells, as claim 16 or 17 described phase difference compensations, and be used for the light of described liquid crystal cells modulation is carried out projection lens projecting, wherein said liquid crystal cells is disposed in the light exit side of described phase difference compensation.

21. liquid crystal projection apparatus, comprise the reflective liquid crystal unit, as claim 16 or 17 described phase difference compensations, and being used for the abaxile projecting lens that the light to the modulation of described liquid crystal cells carries out projection, wherein said liquid crystal cells is disposed in the light exit side of described phase difference compensation.

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