JP2006171327A - Phase difference compensation element, and liquid crystal display device and liquid crystal projector using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase difference compensation element capable of preventing the contrast of a display image from being degraded in dependence on a viewing angle by induced birefringence action of liquid crystal molecules of a TN liquid crystal. <P>SOLUTION: A first phase difference compensation layer 12 and a second phase difference compensation layer 14 which respectively consist of inorganic material are disposed on a transparent glass substrate 10. The first phase difference compensation layer 12 is constituted by laminating two kinds of high and low deposition films which are sufficiently thin with respect to wavelength and is turned to a negative C-plate. The second phase difference compensation layer 14 is constituted with an oblique deposition film of at least two-layer constitution and is turned to a positive O-plate. The first phase difference compensation layer performs phase difference compensation for the liquid crystal molecules having vertical alignment in the liquid crystal layer, and the second phase difference compensation layer performs phase difference compensation for the liquid crystal molecules having hybrid alignment in the liquid crystal layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a phase difference compensation element capable of greatly improving a reduction in image contrast depending on a viewing angle when an image displayed on a twisted nematic liquid crystal (hereinafter referred to as TN liquid crystal) is observed. The present invention relates to a liquid crystal display device and a liquid crystal projector using the above.

Background art relating to the present invention includes the following.
JP 2004-102200 A US Pat. No. 5,638,197 Hiroyuki Mori and three others, “Development of FUJIFILM WVfilm Wideview SA” FUJIFILM RESEARCH & DEVELOPMENT No.46-2001 p51-55

  Liquid crystals having various operation modes are known. Among them, TN (Twisted Nematic) liquid crystals are excellent in mass productivity and are widely used as image display elements for direct-view flat panel displays and liquid crystal projectors. A TN liquid crystal is a liquid crystal layer in which rod-like liquid crystal molecules constituting a liquid crystal layer are filled between a pair of transparent substrates on which a transparent electrode and an alignment film are formed. The liquid crystal molecules have their major axes substantially parallel to the substrate. In the thickness direction, the orientation of the major axis is inclined little by little and the whole is twisted by 90 °. When linearly polarized light is incident from one substrate side in this alignment state, the polarization direction is rotated by 90 ° following the alignment state of the liquid crystal molecules in the process toward the other substrate. In addition, when a voltage is applied to the liquid crystal layer, the twisted alignment of the liquid crystal molecules disappears, and the liquid crystal molecules distributed near the center in the thickness direction become an alignment state in which the major axis stands upright, and from one substrate side When linearly polarized light is incident, the polarization direction of the linearly polarized light is emitted without change.

  When a pair of polarizing plates are arranged on the light incident side and the light emitting side of such a TN liquid crystal so that the polarization directions are orthogonal to each other (crossed Nicol arrangement), in the state where no voltage is applied to the liquid crystal layer, Since the polarization direction of the linearly polarized light incident on the liquid crystal through the polarizing plate is rotated by 90 ° by the action of the liquid crystal molecules, it is emitted from the other polarizing plate to be in a bright state (normally white). And in the state which applied the voltage, since the polarization direction of the linearly polarized light which injected into the liquid crystal is preserve | saved as it is, it will be shielded by the other polarizing plate and will be in a dark state. If a pair of polarizing plates are arranged so that their polarization directions are parallel (parallel Nicol arrangement), a dark state (normally black) is obtained when no voltage is applied, and a bright state is obtained when a voltage is applied. Although it is possible to use TN liquid crystal in such a form, a normally white system which is excellent in terms of contrast performance has been widely put into practical use.

  By the way, TN liquid crystal generally has a drawback that the viewing angle is narrow. The cause is that the liquid crystal molecules also act as a birefringent medium. Taking a normally white TN liquid crystal as an example, in the process of applying a voltage to the liquid crystal layer and losing its twisted alignment, optical rotation and birefringence are mixed, and as the voltage applied level increases, Refractiveness becomes dominant. When the twist of the liquid crystal molecules disappears and the liquid crystal layer becomes dark, the liquid crystal layer hardly exhibits birefringence with respect to the normal incident light, so that the linearly polarized light is transmitted as it is. In other words, it exhibits birefringence, and light incident as linearly polarized light is modulated into elliptically polarized light. The elliptically polarized light thus generated is partially transmitted through the polarizing plate on the output side, resulting in a decrease in dark state density. The propensity of the liquid crystal layer as a birefringent medium gradually appears during the transition from the bright state to the dark state, so when the display screen is observed from an oblique direction even in a halftone display state, the modulation degree The angle dependence is inevitable.

  This viewing angle characteristic of TN liquid crystal appears as a change in black density or color depending on the direction of observation in a direct-view flat panel display, and causes a decrease in the contrast of the image projected on the screen in a liquid crystal projector. In any case, the quality of the displayed image is significantly impaired. For example, as described in Patent Document 1, such a drawback is that a thin film made of a high refractive material and a thin film made of a low refractive index material have an optical film thickness of 100 to 1/5 of the wavelength of light. This can be improved by using together the multilayer thin film laminated alternately. This multilayer thin film has a negative C-plate property, and when linearly polarized light is obliquely incident on the liquid crystal molecules in a vertically aligned posture for dark state display and birefringent, the normal thin film and It acts as a negative uniaxial birefringent body that compensates for the phase difference with extraordinary light. Thereby, elliptically polarized light is returned to linearly polarized light again, and leakage light can be prevented from being emitted from the subsequent polarizing plate. Another feature of this phase difference compensation element is that it can be composed of inorganic materials. It has excellent heat resistance and light resistance and is physically and chemically stable, so it can be used not only for direct-view liquid crystal displays but also for liquid crystal projectors. Can also be used effectively.

  Patent Document 2 describes that O-plate is effective for the purpose of improving the viewing angle characteristics of TN liquid crystal. O-plate is a birefringent body whose main optical axis that does not cause birefringence is inclined with respect to a reference plane (for example, a liquid crystal substrate surface). It is disclosed in Patent Document 2 that it can be easily manufactured by performing (rhombic vapor deposition), and further used in combination with C-plate or A-plate.

  The WV film known from Non-Patent Document 1 is a TAC film that is a base and fixed in a state where a discotic compound is hybrid-aligned, and has already been put into practical use. When a dark state display is performed, most liquid crystal molecules distributed in the thickness direction of the liquid crystal layer have a vertical alignment posture, but in a region close to the substrate, the major axis gradually increases from the alignment posture almost parallel to the substrate. Standing hybrid orientation. The birefringent body of Patent Document 1 has incomplete phase difference compensation for birefringence due to liquid crystal molecules in this region. However, as described above, the discotic compound is hybrid-aligned in the WV film. Effective retardation compensation can be performed even for the birefringence action of the liquid crystal molecules.

  As described above, in the retardation compensation element described in Patent Document 1, when a TN liquid crystal is displayed in a dark state using a normally white mode, most liquid crystal molecules vertically aligned in the liquid crystal layer are incident obliquely. Although good phase difference compensation is performed for light rays, phase difference compensation is incomplete for liquid crystal molecules that are hybrid-aligned in a region close to the substrate, and there is still room for improvement. The O-plate described in Patent Document 2 is composed of a single layer of obliquely deposited film, but when used alone or in combination with C-plate, the O-plate is oblique to obtain a desired viewing angle characteristic. The examination of how to optimize the structure of the deposited film is insufficient, and it has not yet reached practical use. On the other hand, although the WV film described in Non-Patent Document 1 can perform effective phase difference compensation in a direct-view type liquid crystal display or the like, since the material is mainly composed of an organic material, the WV film is strong including short wavelength light. There are many problems to be solved in order to provide durability for 10,000 hours or more when used in a liquid crystal projector that is exposed to light for a long time.

  In order to solve these problems, it is advantageous if the phase difference compensation element described in Patent Document 1 can have a hybrid orientation. However, a phase compensation element made of an inorganic material having a hybrid orientation is very difficult to manufacture. Practical application is difficult. In addition, it is also effective to use the negative C-plate described in Patent Document 1 in combination with the O-plate described in Patent Document 2, but currently there is no knowledge about its specific configuration and practical effect, The reality is that it has not been realized.

  The present invention has been made in consideration of the above-mentioned background. The phase difference compensation element described in Patent Document 1 is improved, and an effective phase difference compensation function is performed even for liquid crystal molecules in a hybrid alignment region. An object of the present invention is to provide a phase difference compensator that can reduce the manufacturing cost by efficient manufacturing, and to provide a liquid crystal projector that effectively uses the phase difference compensator. To do.

  In achieving the above object, the retardation compensation element of the present invention comprises a first retardation compensation layer that compensates for the angular dependence of the retardation caused by vertically aligned liquid crystal molecules in the liquid crystal layer, and a position determined by hybrid aligned liquid crystal molecules. A second retardation compensation layer that compensates for the phase difference, and each of these retardation compensation layers is formed of a multilayer film in which structural birefringent members made of an inorganic material are laminated. Then, at least one of the first and second retardation compensation layers can be a multilayer film laminated by a vacuum film formation method, and in particular, for the second retardation compensation layer, the orientation of the deposition direction with respect to the deposition surface It can be constituted by a multilayer film in which a plurality of oblique vapor deposition layers having different angles and polar angles are laminated, and the second retardation compensation layer is constituted by laminating three or more oblique vapor deposition films. Is preferred. The vapor deposition direction of each obliquely deposited film may not be different from each other in both the azimuth angle and the polar angle, and the combination of the azimuth angle and the polar angle in the vapor deposition direction may be different for each obliquely deposited film. That's fine. In addition, it is desirable to suppress the number of stacked layers of oblique vapor deposition films to 10 layers or less in consideration of the entire thickness and manufacturing efficiency.

The azimuth angle in the vapor deposition direction of each oblique vapor deposition film is set to be different from the alignment azimuth angle given to the liquid crystal molecules by the alignment film of the TN liquid crystal cell. Then, optical axis vectors are defined for each obliquely deposited film from the retardation, azimuth, and polar angle of each obliquely deposited film, and a composite vector A in which these optical axis vectors are synthesized by the number of layers is supported. The xy coordinate line segment (Ax, Ay) when orthogonally projected onto the vapor deposition surface parallel to the transparent substrate or the TN liquid crystal substrate as the body,
−200 nm ≦ Ax ≦ 200 nm
−500 nm ≦ Ay ≦ 0 nm
To satisfy both.

Also, the value of retardation d1Δn1 of the first retardation compensation layer with respect to the product (dΔn) _LC of the thickness d and the birefringence of the liquid crystal layer of the TN liquid crystal,
−2 × (dΔn) _LC ≦ d1Δn1 ≦ −0.5 × (dΔn) _LC
It is also effective to satisfy the above. Such a first retardation compensation layer is composed of a vapor deposition film in which a high refractive index material and a low refractive index material are alternately stacked, and each optical film thickness is 1/100 or more and 1/5 of the reference wavelength. Within the following range, it is sufficiently thinner than a normal interference thin film. Furthermore, an antireflection layer may be provided on at least one of the light incident surface and the light output surface for the purpose of suppressing the interface reflection of the phase difference compensation element.

  The phase difference compensation element of the present invention can be applied to a so-called liquid crystal display device such as a direct view type liquid crystal display using a TN liquid crystal cell, and is particularly suitable for a liquid crystal projector. In applying the phase difference compensation element of the present invention to a so-called three-plate type liquid crystal projector that uses TN liquid crystal for each component color light, the three phase difference compensation elements combined with each TN liquid crystal are used as the reference of the component color light. It is composed of at least two types of phase difference compensation elements whose retardation is adjusted according to the wavelength. The liquid crystal projector may be either a front projector that projects an image from the front side of the screen or a rear projector that projects an image from the back of the screen.

  According to the retardation compensator of the present invention, the second retardation compensation layer that compensates for the retardation associated with the birefringence of the liquid crystal molecules that are hybrid-aligned is formed of a multilayer film in which a structural birefringence is laminated. Thus, it is possible to obtain a favorable phase difference compensation action. At least one of the first and second retardation compensation layers can be efficiently manufactured by a multilayer film formed by a vacuum film formation method, and in particular, the second retardation compensation layer has an azimuth angle in the vapor deposition direction with respect to the vapor deposition surface. And a multilayer film in which oblique vapor deposition films having different polar angles are laminated, a good retardation compensation action is obtained. When combined with a TN liquid crystal used in a normally white mode, an oblique incidence is obtained. Even for light, light leakage under a dark state display can be sufficiently suppressed, and as a result, the contrast of a display image can be increased. Moreover, since the second retardation compensation layer is composed of an inorganic material together with the first retardation compensation layer, it is excellent in heat resistance and light resistance, and is physically and chemically stable. There is an advantage that it can be applied not only to a general liquid crystal display device such as a liquid crystal display monitor but also to a liquid crystal projector using a high brightness light source. Moreover, since the first retardation compensation layer can also be composed of a vapor deposition film of an inorganic material, it can be efficiently manufactured in a consistent process together with the second retardation compensation layer. Further, the phase difference compensation element 6 can be incorporated between the TN liquid crystal 2 and the polarizing plate 3 to achieve the same action.

  The liquid crystal display device using the phase difference compensation element of the present invention is configured in principle as shown in FIG. Polarizing plates 3 and 4 are respectively arranged on the light incident surface side and the light emitting surface side of the TN liquid crystal 2, and these polarizing plates 3 and 4 are orthogonal to each other in consideration of use in a normally white mode. Crossed Nicols arrangement. The polarizing plate 3 becomes a polarizer that converts the illumination light into linearly polarized light, and the polarizing plate 4 emits a part of the output light modulated by the TN liquid crystal 2 that matches the polarization direction and blocks the remaining light. Become an analyzer.

  The retardation compensation element 6 of the present invention is incorporated between the TN liquid crystal 2 and the polarizing plate 4. The liquid crystal molecules of the TN liquid crystal 2 have a birefringence action, and the linearly polarized light is emitted in various elliptical polarizations according to the orientation and the incident angle of the illumination light. May be superimposed on the image light, but the phase difference compensation element 6 compensates for the phase difference between the ordinary light and the extraordinary light generated by the birefringence action of the liquid crystal molecules to return the elliptically polarized light to the original linearly polarized light. Perform the action. Since the retardation compensation element 6 is composed of a thin film deposited with an inorganic material, the support includes a transparent substrate such as a glass substrate, but the transparent substrate of the TN liquid crystal 2 and the transparent substrate of the polarizing plate 4 are used as the support. It can also be used in combination. Further, the phase difference compensation element 6 can be incorporated between the TN liquid crystal 2 and the polarizing plate 3 to achieve the same action.

The phase difference compensation element 6 has a cross-sectional structure schematically shown in FIG. A first retardation compensation layer 12 and a second retardation compensation layer 14 are provided on one surface of the glass substrate 10 serving as a support, and antireflection layers 15 and 16 are provided on the uppermost layer and the back surface of the glass substrate 10. Is formed. Each of the antireflection layers 15 and 16 is for preventing surface reflection. For example, a single-layer film in which MgF ₂ which is a low refractive index material is formed with an optical film thickness λ / 4, or a combination of different vapor deposition materials is used. An antireflection film or the like can be used. When the first and second retardation compensation films 12 and 14 and the antireflection films 15 and 16 are formed by vapor deposition, they are formed by sputtering deposition in addition to vacuum vapor deposition by resistance heating or electron beam heating. You can also In addition, the first retardation compensation layer 12 and the second retardation compensation layer 14 can perform the same operation even if this vertical relation is reversed, and are formed on either the front or back surface of the glass substrate 10. May be.

  As shown in FIG. 3, the first retardation compensation layer 12 is composed of a multilayer film in which two types of vapor deposition films L1 and L2 having different refractive indexes are alternately laminated on a glass substrate 10, and the respective vapor deposition directions are vapor deposition. Perpendicular to the surface. The optical film thickness (product of physical film thickness and refractive index) of each layer is sufficiently smaller than a standard light wavelength (for example, 550 nm), preferably λ / 100 to λ / 5, more preferably λ / 50 to λ / 5, in practice, λ / 30 to λ / 10 is appropriate, and is sufficiently thinner than an optical thin film using general optical interference. The multilayer film thus formed exhibits a negative C-plate property and is used as a uniaxial negative birefringent body. The first retardation compensation layer 12 may be other than the multilayer film as long as it has a negative C-plate effect.

  The design procedure of the first retardation compensation layer 12 is as follows. The birefringence Δn of the first retardation compensation layer 12 is an optical property of two kinds of vapor deposition films L1 and L2 having different refractive indexes as described in “Optical Vol. 27 No. 1 (1998) p.12-17”. It is determined by the ratio of the film thickness, and becomes larger as there is a difference in the respective refractive indexes. In addition, since the retardation by the first retardation compensation layer 12 is given by the product “d1Δn1” of the birefringence Δn1 and the physical total film thickness d1 of the first retardation compensation layer 12, in order to obtain a desired retardation. For this, a film thickness ratio such that the value of the birefringence Δn1 obtained from these materials is increased is obtained, and the total film thickness d1 of the entire first retardation compensation layer 12 is determined based on the birefringence Δn1. .

Actually, a thin film multi-layer deposition sample in which 40 layers of TiO ₂ layers having a physical film thickness of 15 nm and SiO ₂ layers having a physical film thickness of 15 nm are alternately laminated on the glass substrate 10 is prepared and measured using a spectroscopic ellipsometer. As a result, it is a negative birefringent body that gives a phase difference of 208 nm, and the incident direction of the light beam when it shows optical isotropy to the incident light beam, that is, the direction of the optical axis is It was confirmed to function as a negative C-plate consistent with the normal.

As a vapor deposition material for the vapor deposition films L1 and L2, as a high refractive material, TiO ₂ (n = 2.about.2.4), ZrO ₂ (n = 2.20), etc., as a low refractive index material, SiO ₂ (n = 1.40 to 1.48), MgF ₂ (n = 1.39), CaF ₂ (n = 1.30), and the like, and various materials listed below are also used for the deposited films L1 and L2. It can be used as a vapor deposition material. The values in parentheses are approximate values of the refractive index. CeO ₂ (2.45), Nb ₂ O ₅ (2.31), SnO ₂ (2.30), Ta ₂ O ₅ (2.12), In ₂ O ₃ (2.00), ZrTiO ₄ (2 .01), HfO ₂ (1.91), Al ₂ O ₃ (1.59-1.70), MgO (1.7), AlF ₃ , diamond thin film, LaTiO _x , samarium oxide and the like. The combination of the high refractive index thin film layer material and the low refractive index thin film layer material is preferably TiO ₂ / SiO _2, but Ta ₂ O ₅ / Al ₂ O ₃ , HfO ₂ / SiO ₂ , MgO / Examples thereof include MgF ₂ , ZrTiO ₄ / Al ₂ O ₃ , CeO ₂ / CaF ₂ , ZrO ₂ / SiO ₂ , ZrO ₂ / Al ₂ O _{3 and the} like.

  The first retardation compensation layer 12 may be formed by alternately depositing vapor deposition films L1 and L2 having two different high and low refractive indexes. Therefore, a shutter is provided so that each evaporation source can be shielded from the glass substrate 10, and the two types of vapor deposition films L1 and L2 are alternately laminated by alternately opening and closing these shutters, or The glass substrate 10 is held on a substrate holder that circulates and moves at a constant speed, and two kinds of vapor deposition films L1 and L2 are sequentially stacked by passing the substrate over each evaporation source in the process of circulating and moving the substrate. Can be used. Thereby, when a multilayer thin film is obtained, the vacuum chamber only needs to be evacuated once, so that efficient production becomes possible.

  The second retardation compensation layer 14 may be formed by laminating layers having an O-plate action made of an inorganic compound, and as a manufacturing method thereof, an oblique vapor deposition method or JP-A-2004-212468 is disclosed. It is conceivable to use a photolithography method as described in paragraphs [0083] to [0085], or a method in which rod-like molecules are oriented and formed, but oblique deposition from the viewpoint of mass production and suitability for production. Preferably it is manufactured. Hereinafter, examples of forming by oblique deposition will be described. In the case of forming by oblique deposition, the first retardation compensation layer and the second retardation compensation layer can be formed by the same vacuum film formation method, which is preferable.

  As shown in FIG. 4, the second retardation compensation layer 14 has a structure in which three kinds of oblique deposition films S1, S2, and S3 are laminated. As shown in FIG. 2, the first obliquely deposited film S1 is laminated on the first retardation compensation layer 12, but the first retardation compensation layer 12, the second retardation compensation layer 14, and the like. , The first layer of obliquely deposited film S1 is formed on the glass substrate 10, the second and third layers of obliquely deposited films S2 and S3 are sequentially stacked thereon, and then the first retardation compensation layer is formed. 12, or the first retardation compensation layer 12 and the second retardation compensation layer 14 are formed on the front and back of the glass substrate 10, and antireflection layers 15 and 16 can be laminated on the uppermost layers of each. It is.

  Unlike the vapor deposition films L1 and L2 constituting the first phase difference compensation layer 12, each of the oblique vapor deposition films S1 to S3 is vapor-deposited from an oblique direction with respect to the vapor deposition surface S0 and is directed to the vapor deposition direction for each layer. It has an aggregate structure of minute columnar elements M1 to M3 grown obliquely. As illustrated, the columnar element M1 of the oblique deposition film S1, the columnar element M2 of the oblique deposition film S2, and the columnar element M3 of the oblique deposition film S3 are not parallel to each other. Although such obliquely deposited films S1 to S3 can be used as an O-plate having a structural birefringence function and having positive birefringence even with a single layer, the second retardation compensation layer 14 of the present invention is One of the features is that such an obliquely deposited film is used in multiple layers.

  The oblique vapor deposition films S1 to S3 can be produced using, for example, the vapor deposition apparatus shown in FIG. In FIG. 5, a base holder 20 is provided with a material holder 21 that rotates in a turret manner, and vapor deposition materials 22 and 23 are accommodated therein. After the vacuum chamber 24 is evacuated, the vapor deposition material 22 is irradiated with the electron beam 27 from the electron gun 25 to evaporate the vapor deposition material 22, thereby performing vacuum vapor deposition. The start and stop of vacuum deposition can be controlled by opening and closing the shutter 29, and the deposition materials 22 and 23 can be selected and used by rotating the material holder 21. Basically, the second retardation compensation layer 14 is formed to be a multilayer film using one kind of vapor deposition material. By using such a material holder 21, different types of vapor deposition can be performed as necessary. It is also possible to use materials.

  A substrate holder 30 disposed obliquely above the material holder 21 is provided, and a transparent sample substrate 26 is held. The normal line of the support surface of the substrate holder 30 is inclined by an angle β with respect to the line segment P extending vertically from the vapor deposition material 22, and therefore the vapor deposition surface of the sample substrate 26 is also inclined by the angle β with respect to the line segment P. This angle β can be adjusted by rotating the substrate holder 30 about an axis perpendicular to the paper surface. Further, by rotating the substrate holder 30 around the axis 30a, the angle α corresponding to the azimuth angle of the line segment P in the vapor deposition surface can be adjusted. Since the line segment P corresponds to the vapor deposition direction with respect to the vapor deposition surface, the vapor deposition direction with respect to the vapor deposition surface can be adjusted in two ways as a result by changing the angles α and β. As described above, the angle α corresponds to the azimuth angle of the vapor deposition direction in the vapor deposition surface, and the angle β corresponds to the polar angle representing the inclination of the vapor deposition direction with respect to the vapor deposition surface. It is represented by α and polar angle β.

  Reference numeral 31 in the figure represents a crystal-type film thickness monitor, which monitors the film thickness of the vapor deposition film on the measurement surface, and the degree of vapor deposition proceeds on the sample substrate 26 held by the substrate holder 30. It is for measuring relatively whether or not. Reference numeral 32 denotes an ellipsometer, which receives the measurement light from the projector 33 through the monitor substrate 28 and measures the phase difference associated with birefringence while forming an obliquely deposited film on the sample substrate 26. Can do. The measurement surface of the film thickness monitoring monitor 31 and the phase difference measurement system including the monitor substrate 28 can be rotated so as to coincide with the polar angle β of the substrate holder 30. Each time the formation of the oblique deposition film is completed, the phase difference can be monitored for each layer by exposing the new measurement surface and the monitor substrate surface due to the displacement of the mask plate. . The retardation of the obliquely deposited film can be estimated from the phase difference data measured by the ellipsometer 32. Therefore, if the deposition is performed while monitoring the measurement data obtained from the ellipsometer 32 and the film thickness monitoring monitor 31, each layer is desired. It is possible to obtain an obliquely deposited film having the following retardation.

  Through the above operation, the second retardation compensation layer made of the oblique vapor deposition film having a multilayer structure can be formed on the sample substrate 26 while monitoring the retardation for each layer. Further, as shown in FIG. 2, even after the first retardation compensation layer 12 is formed on the glass substrate 10, the glass substrate 10 is held by the substrate holder 30 so that the retardation is set in advance for each layer. The multilayer second retardation compensation layer 14 can be formed on the first retardation compensation layer 12 by performing oblique deposition.

  As shown in FIG. 6, the vapor deposition direction P with respect to the vapor deposition surface S0 is measured from the azimuth angle α measured counterclockwise from the x axis and the z axis when orthogonally projected onto the xy coordinate plane on the vapor deposition surface S0. The polar angle β can be expressed as follows. The polar angle β is an angle that does not have positive and negative directivity as an inclination from the z axis, but the azimuth angle α has directivity with reference to the x axis.

  FIG. 8 schematically shows a state where a saturation voltage is applied between the substrates 35 and 36 of the TN liquid crystal 2 for dark state display. Alignment films 35 a and 36 a are provided inside the substrates 35 and 36 in order to give the liquid crystal molecules 38 a 90 ° twist alignment. The alignment film 35a gives the liquid crystal molecules 38 an orientation parallel to the plane of the paper, and the orientation film 36a gives an orientation perpendicular to the plane of the paper. The polarization directions of the polarizing plates 3 and 4 are adjusted to the respective orientation directions. In the figure, the liquid crystal molecules 38 distributed near the center of the cell in the thickness direction due to the application of the saturation voltage have a vertical orientation, but the tilt angle of the liquid crystal molecules 38 is continuous in the vicinity of each substrate. There are areas that are changing. The first retardation compensation layer 12 of the retardation compensation element 6 performs retardation compensation by the birefringence action of the liquid crystal molecules 38 in the vertical alignment posture, and the second retardation compensation layer 14 has a continuous tilt angle. The phase difference is compensated by the birefringence action of the liquid crystal molecules 38 which are changed in the region, that is, in the hybrid alignment.

  The alignment direction of the liquid crystal molecules 38 is determined by the rubbing direction when the alignment films 35a and 36a are formed. As schematically shown in FIG. 7, the alignment films 35a and 36a are rubbed in the directions indicated by arrows 35b and 36b, respectively, thereby determining the alignment direction of the liquid crystal molecules 38. Note that the coordinate systems of the x-axis, y-axis, and z-axis in FIGS. 6 and 7 are defined in the same direction in the space. Here, the direction of the x-axis is set so that the rubbing direction 35b of the alignment film 35a is δ = 45 ° from the x-axis, whereby the rubbing direction 36b of the alignment film 36a is in the direction of −45 ° from the x-axis. Match. Under this arrangement, when the TN liquid crystal 2 is operated by applying a voltage, the major axis of the liquid crystal molecules distributed near the center in the thickness direction of the liquid crystal cell is in the yz plane, and the tilt angle is the y axis. It operates within an angle range that rises in the positive direction of the z-axis from the positive direction.

  The vapor deposition direction P substantially coincides with the optical axis of the oblique vapor deposition film S1. Although the obliquely deposited film S1 has a positive O-plate property showing a structural birefringence action, it exhibits optical isotropy with respect to light rays traveling parallel to the growth direction of the columnar element M1. Therefore, the optical axis coincides with the growth direction of the columnar element M1 after being refracted and incident at the interface with a medium (for example, air) having a refractive index of 1, and is inclined from the growth direction of the columnar element. The direction is inclined by an angle corresponding to the refractive index of the vapor-deposited film, and strictly, the direction is slightly shifted from the vapor deposition direction P.

Therefore, the optical axis is determined from the deposition direction P defined by the azimuth angle α and the polar angle β with the origin O as the base point, and the retardation (dΔn) _S1 value determined from the birefringence and film thickness of the oblique deposition film S1. A vector P1 is defined, and similarly, optical axis vectors P2 and P3 are obtained for the oblique deposition layers S2 and S3. These optical axis vectors Pi are generally obtained by combining each retardation value (dΔn) _Si with azimuth angle α _i and polar angle β _i .
Pi (x, y, z) = ((dΔn) _Si × cos α _i × tan β _i ,
(dΔn) _Si × sin α _i × tan β _i , (dΔn) _Si )
It can be expressed as. The subscript i in the above formula represents the number of the obliquely deposited films S1 to S3. A synthesized vector A obtained by synthesizing these optical axis vectors Pi is expressed as A = ΣPi
Then, this synthetic vector A corresponds to an average vector obtained by weighting the obliquely deposited film composed of multiple layers with the retardation (dΔn) _Si of each layer.

In producing the second retardation compensation layer 14 composed of the three-layered films of the obliquely deposited films S1 to S3, how to determine the optical axis vectors P1 to P3 of the obliquely deposited films S1 to S3 and the optical There are various combinations depending on how to select the retardation (dΔn) _Si , the azimuth angle α _i and the polar angle β _i of each obliquely deposited film in order to obtain the axis vectors P1 to P3. In the present invention, in order to optimize the second retardation compensation layer 14, x, y coordinate values (Ax, Ay) obtained when the composite vector A is orthogonally projected onto the deposition surface S0 are used as evaluation criteria. .

That is, the optical axis vectors P1 to P3 of the oblique deposition films S1 to S3 are synthesized in FIG. 9 when the xy plane is seen from the positive direction of the z axis in FIG. 6, and the resultant vector A is orthogonally projected onto the deposition surface S0. When the value (Ax, Ay) of the x component and the y component of the composite vector A is
−200 nm ≦ Ax ≦ 200 nm and −500 nm ≦ Ay ≦ 0 nm (Condition 1)
The composite vector A is determined so as to satisfy Ax and Ay are defined in the same coordinate system as the xyz coordinate system described in [0033] above, and are determined corresponding to the direction of the major axis of the liquid crystal molecules distributed near the center in the thickness direction of the liquid crystal cell. And is independent of the rotational direction of the twist of the liquid crystal molecules. In addition, as a more preferable range of Ax, Ay,
−100 nm ≦ Ax ≦ 100 nm and −300 nm ≦ Ay ≦ −50 nm (Condition 2)
Is mentioned. Ax can take a plurality of values across zero nm, preferably a value larger than −200 nm and smaller than 200 nm, and more preferably a value larger than −100 nm and smaller than 100 nm as shown in the embodiment. is there. Moreover, Ay takes a negative value, Preferably it is a negative value larger than -500 nm, More preferably, it can take the value of -300 nm or more and -50 nm or less as shown in the Example.

  By the way, in the TN liquid crystal 2, the ratio of the liquid crystal molecules 38 in the vertical alignment posture is changed by the saturation voltage applied in the dark state display. Since the first retardation compensation layer 12 described above functions to compensate the optical anisotropy due to the birefringence action of the liquid crystal molecules 38 in the vertical alignment posture, the retardation of the first retardation compensation layer 12 has a saturation voltage. When the ratio of liquid crystal molecules that take a vertical alignment posture when applied is large, the value is determined to be a large value. The corresponding retardation is in the range of about 50% to 90% of the retardation of the TN liquid crystal cell.

  In the present invention, it is necessary to consider another factor in determining the retardation of the first retardation compensation layer 12. That is, canceling an excessive amount of phase difference compensation out of the positive phase difference component in the z-axis direction generated by providing the second phase difference compensation layer 14. The obliquely deposited layers S1 to S3 compensate for the angular dependence of the phase difference due to the liquid crystal molecules in the vicinity of the substrate of the TN liquid crystal 2, but the phase difference due to the liquid crystal molecules tilted in an angle range that can be regarded as substantially parallel to the substrate. In theory, the oblique deposition film whose optical axis is substantially parallel to the substrate, in other words, the polar angle β is close to 90 ° so that the growth direction of the columnar elements is substantially parallel to the substrate. An obliquely deposited film is required. However, the production of such an obliquely deposited film is extremely difficult in practice.

  For this reason, phase difference compensation for liquid crystal molecules whose major axes are nearly parallel near the substrate is oblique deposition with a polar angle smaller than the originally required polar angle, and the film thickness is increased. Although it is necessary to cope with the film, as a result, it is inevitable that excessive phase difference compensation is performed in the direction perpendicular to the substrate. Therefore, the first retardation compensation layer 12 also needs to act to alleviate this excessive retardation compensation, and the amount of retardation of the first retardation compensation layer 12 cancels the excess positive retardation compensation component. To obtain a negative phase difference. The lower limit of the amount is “0”, but the upper limit depends on the amount of the positive phase difference that has become excessive, and is not necessarily a clear value. In reality, the ease of film formation, cost, etc. The film thickness is limited by these conditions.

From the above, when the value of the negative retardation (d1Δn1) of the first retardation compensation layer 12 is expressed in relation to the value of the positive retardation (dΔn) _LC of the TN liquid crystal, the value is approximately It is preferable to keep within the range.
−2 × (dΔn) _LC ≦ (d1Δn1) ≦ −0.5 × (dΔn) _LC (conditional expression 2)

In addition, as a vapor deposition material of the oblique vapor deposition film of the second retardation compensation layer 14, as in the first retardation compensation layer 12, an oblique vapor deposition film such as TiO ₂ , SiO ₂ , ZrO ₂ , Ta ₂ O ₃ is used. Various materials can be used as long as they have sufficient light transmission characteristics regardless of the wavelength.

Hereinafter, specific examples of the phase difference compensating element 6 using the present invention will be described. In these examples, the birefringence (Δn) at a wavelength of 550 nm is “0.124”, the cell thickness (the thickness of the liquid crystal layer) is “4500 nm”, and the retardation (dΔn) _LC value is “558 nm”. This is for evaluating the structural optimum values of the first and second retardation compensation layers suitable for the TN liquid crystal based on the isocontrast curve. An isocontrast curve is obtained by measuring the luminance ratio as a contrast ratio while changing the viewing angle when the bright state display and the dark state display are performed on the liquid crystal, and connecting the viewing angles at the equal contrast ratio. The isocontrast curve of the liquid crystal itself is as shown in FIG. It can be seen that the contrast varies greatly depending on the viewing angle. In the following examples, the first retardation compensation layer and the second retardation compensation layer were formed with the reference wavelength set to 550 nm.

Corning 1737 (50 mm × 50 mm) was used as a glass substrate, washed with acetone, sufficiently dried, and then set in a vapor deposition apparatus for performing normal front vapor deposition (β = 0 °). The vacuum chamber was evacuated to 1 × 10 ⁻⁴ Pa, and the glass substrate was heated to 300 ° C. to form a three-layer antireflection film. This antireflection film is formed by laminating SiO ₂ with an optical film thickness of λ / 4, TiO ₂ of λ / 2, and SiO ₂ of λ / 4 sequentially from the glass substrate side, and the reference wavelength λ is 550 nm.

  After forming the antireflection film, the glass substrate was turned upside down in the vacuum layer to form the first retardation compensation layer. As shown in FIG. 3, the first retardation compensation layer is composed of a multilayer film in which two kinds of vapor deposition films L1 and L2 are alternately stacked, and the retardation (d1Δn1) is a negative value. Accordingly, by adjusting the overall physical film thickness d1 and the birefringence Δn1, the magnitude of the retardation (d1Δn1) can be arbitrarily determined to some extent, so that this value is “−600 nm”. A phase difference compensation layer was formed on the back surface of the glass substrate.

In addition, it is as follows if it supplements about this 1st phase difference compensation layer. That is, a thin film having refractive indexes n ₁ and n ₂ and physical thicknesses a and b alternately stacked at a pitch (a + b) sufficiently shorter than the wavelength is a structure having a negative birefringence Δn. It is known to be a birefringent body. When electromagnetic waves are perpendicularly incident on this structural birefringent body, the electric field is only a wave (TE wave) that oscillates parallel to the plane of each layer, and thus does not exhibit birefringence. However, when electromagnetic waves are incident on the laminated surface of each layer at an angle, it is effective for the wave (TE wave component) in which the electric field vibrates parallel to each layer and the wave (TM wave component) in which the electric field vibrates perpendicularly to each layer. It is known that the refractive indexes N _TE and N _TM are different and are expressed by the following equations, respectively.
N _TE = √ {(an ₁ ² + bn ₂ ² ) / (a + b)}
N _TM = √ [(a + b) / {(a / n ₁ ² ) + (b / n ₂ ² )}]
The difference between these effective refractive indexes N _TE and N _TM is a factor causing birefringence, and the birefringence Δn is given by “Δn = N _TM −N _TE ”.

As can be seen from the above equation, the birefringence Δn1 can be determined by selecting the refractive indexes n ₁ and n ₂ of the vapor deposition layers L1 and L2 and the respective physical film thicknesses a and b. The total physical film thickness d1 can be determined by the number of repeated laminations of L2. Therefore, by selecting an appropriate material from among vapor deposition materials having light transmission characteristics and excellent vapor deposition suitability, the retardation (d1Δn1) value of the first retardation compensation layer can be set to the TN liquid crystal. Retardation (dΔn) of _LC can be close to the value of _LC .

The glass substrate thus formed up to the first retardation compensation layer was taken out of the vacuum chamber, washed again with acetone and sufficiently dried, and then set in the vapor deposition apparatus shown in FIG. The second retardation compensation layer having a two-layer structure was deposited using the deposition surface as the uppermost layer of the first retardation compensation layer. In the first obliquely deposited film S1, the azimuth angle α was −137 °, the polar angle β was 45 °, and the value of retardation (dΔn) _S1 was set to “150 nm”. Further, the azimuth angle α of the second obliquely deposited film S2 is −45 °, the polar angle β is 33 °, and the retardation (dΔn) _S2 is “180 nm”. While monitoring the measurement data from the ellipsometer 32 and the film thickness monitor 31, the second phase difference compensation layer is formed, the sample is taken out, and the same three layers are set again in a normal front evaporation apparatus. An antireflection film was formed.

As a vapor deposition material for the oblique vapor deposition films S1 and S2 constituting the second retardation compensation layer, a mixture of ZrO ₂ and TiO ₂ at 10% by weight was used. In film formation, the vacuum chamber was evacuated to 1 × 10 ⁻⁴ Pa, and then oxygen gas was introduced to 1 × 10 ⁻² Pa so that sufficient oxidation was performed during film formation. Regarding Example 1 thus obtained, the layer configuration of the first and second retardation compensation layers and these parameters are as shown in Table 1 below.

  When the phase difference compensation element of Example 1 is applied to a TN liquid crystal, its isocontrast curve is as shown in FIG. It is clear that the viewing angle characteristic is improved as compared with the isocontrast curve of only the TN liquid crystal shown in FIG.

  When the optical axis vector P1 of the oblique deposition film S1 is orthogonally projected onto the deposition surface, the xy coordinate component values are (83, −83), and the optical axis vector P2 of the oblique deposition film S2 is (−110, −102). Therefore, the xy component of the combined vector A obtained by combining these optical axis vectors P1 and P2 is (−27, −183), which satisfies the conditional expression 1. Further, since the retardation (d1Δn1) value of the first retardation compensation layer is “−600 nm”, the lower limit value “−1118 nm” and the upper limit value of the conditional expression 2 when the retardation of the TN liquid crystal is “558 nm”. It falls within the range of “−279 nm” and the conditional expression 2 is also satisfied.

  Similarly, a sample of Example 2 was produced. The configurations of the TN liquid crystal and the antireflection film are completely the same, and only the film configurations of the first retardation compensation layer and the second retardation compensation layer are different from those of the first embodiment. The parameters are as shown in Table 2 below. In Example 2, the second retardation compensation layer has a three-layer structure, and the azimuth angle α of each layer is rotated in the same direction. Accordingly, the optical axis vectors P1 to P3 of each layer are spirally rotated sequentially in the counterclockwise direction with respect to the deposition surface, as shown in FIG.

  The isocontrast curve of Example 2 is as shown in FIG. It can be seen that the region showing high contrast is wider than that of Example 1, and the dependency on the viewing angle is also low. The x and y components of the combined vector A obtained by synthesizing the optical axis vectors P1 to P4 of the oblique deposition films S1 to S3 are (−18, −196), and the retardation of the first retardation compensation layer is “−370 nm”. Therefore, both conditional expression 1 and conditional expression 2 are satisfied.

  In Example 3, the retardation of the first retardation compensation layer was set to “−440 nm”, and the second retardation compensation layer was configured in three layers as in Example 2. The parameters of each layer are as shown in Table 3. is there. However, in Example 2, the azimuth angle α of each layer is rotated in one direction and the optical axis vectors P1 to P3 are spiral, whereas in Example 3, the azimuth angle α of the third layer is reversed. It is rotating.

  The isocontrast curve of Example 3 is as shown in FIG. 13, and it can be seen that the viewing angle characteristics are kept good. The x and y components of the combined vector A obtained by synthesizing the optical axis vectors P1 to P3 of the oblique deposition films S1 to S3 are (−2, −223), and the retardation of the first retardation compensation layer is “−440 nm”. Conditional expression 1 and conditional expression 2 are both satisfied. Although the optical axis vectors of the three layers constituting the second retardation compensation layer are not rotated helically, the characteristic curve has a shape as shown in the comparison of the isocontrast curves of FIGS. It can be seen that although there is a change, the viewing angle characteristics are not significantly affected.

  In Example 4, the retardation of the first retardation compensation layer was set to “−500 nm”, and the second retardation compensation layer was further increased to form four layers. The parameters of each layer are as shown in Table 4. The oblique vapor deposition films S1 to S4 of each layer constituting the second retardation compensation layer are determined so that the azimuth angle α rotates in one direction, and therefore the optical axis vectors P1 to P4 of each layer are opposite to the vapor deposition surface. It is a clockwise spiral.

  The isocontrast curve of Example 4 is as shown in FIG. 14, and the viewing angle characteristics are well improved. The x and y components of the composite vector A obtained by synthesizing the optical axis vectors P1 to P4 of the oblique deposition films S1 to S4 are (32, −77), and the retardation of the first retardation compensation layer is “−500 nm”. Conditional expression 1 and conditional expression 2 are both satisfied.

  In Example 5, the retardation of the first retardation compensation layer is set to “−470 nm”, and the second retardation compensation layer has a four-layer structure. Unlike Example 4, the azimuth angle α of each layer is rotated in the opposite direction. ing. Therefore, the optical axis vectors P1 to P4 of each layer are in a reverse spiral shape. Table 5 shows the parameters of each layer.

  The isocontrast curve of Example 5 is as shown in FIG. 15, and a good viewing angle characteristic can be obtained. The x and y components of the combined vector A obtained by synthesizing the optical axis vectors P1 to P4 of the obliquely deposited films S1 to S4 are (8, -191), and the retardation of the first retardation compensation layer is “−470 nm”. Both Expression 1 and Conditional Expression 2 are satisfied. In comparison with Example 4 above, it can be seen that the spiral direction of the optical axis vector of each layer constituting the second retardation compensation layer can be applied. However, this does not mean that the spiral direction of the optical axis vector has no effect on the viewing angle characteristics. Even if the spiral direction changes, the azimuth angle α, polar angle β, retardation of each layer, and the first phase difference are changed. It has been confirmed that the optimum value of the combination of retardation of the compensation layer changes.

  Example 6 is an example in which the retardation of the first retardation compensation layer is set to “−350 nm” and the second retardation compensation layer has a five-layer structure. The optical axis vectors P <b> 1 to P <b> 5 of each layer are stacked so as to form a spiral, and parameters of each layer are as shown in Table 6.

  The isocontrast curve of Example 6 is as shown in FIG. 16, and good viewing angle characteristics are obtained. The x and y components of the combined vector A obtained by synthesizing the optical axis vectors P1 to P5 of the oblique deposition films S1 to S5 are (6, −239), and the retardation of the first retardation compensation layer is “−350 nm”. Conditional expression 1 and conditional expression 2 are both satisfied.

  As can be seen from the above embodiments, the viewing angle dependency of the TN liquid crystal can be effectively compensated by the combination of the retardation of the first retardation compensation layer and the layer configuration of the second retardation compensation layer. Can do. In particular, the layer configuration of the second retardation compensation layer is also affected by the retardation value of the first retardation compensation layer, and the combination of parameters for obtaining the optimum viewing angle characteristics is enormous. According to the verification process, it is considered essential that at least the conditional expression 1 and the conditional expression 2 are satisfied.

  The retardation value applied to the first retardation compensation layer must basically be selected according to the positive birefringence of the liquid crystal molecules and the thickness of the liquid crystal layer. The proportion of liquid crystal molecules that take a vertical alignment when is applied is not necessarily constant. Therefore, the retardation value of the first retardation compensation layer should be determined in consideration of the ratio, and further, adjustment should be made assuming positive birefringence due to the second retardation compensation layer.

  Furthermore, as already described, the phase difference compensation element of the present invention can be used not only on the light exit surface side but also on the light incident surface side of the TN liquid crystal. The retardation compensation layer may be formed on a separate glass substrate and used separately. In addition, at least one of the base substrates of the pair of polarizing plates arranged on the light incident surface side and the light emitting surface side of the TN liquid crystal is used as the base of the first retardation compensation layer and / or the second retardation compensation layer. This is also a preferred embodiment.

  The retardation compensation element of the present invention is a full-color direct-view display that uses a single-plate TN liquid crystal as a display element when the reference wavelength for producing the first and second retardation compensation layers is set to 550 nm, for example. Can be used. However, since the birefringence effects of the liquid crystal molecules and the phase difference compensation element differ depending on the wavelength, it is desirable to change the film configuration of the phase difference compensation element for each reference wavelength of the component color light. In this case, the TN liquid crystal generally incorporates micro color filters that transmit red, green, and blue, which are component color lights, respectively. Therefore, three types of phase difference compensation with different film configurations corresponding to these filter elements. An element is preferably used.

  Changing the film configuration of the phase difference compensation element in accordance with the reference wavelength of the component color light can be effectively performed particularly in a three-plate type color liquid crystal projector using three TN liquid crystals for each component color light. FIG. 17 schematically shows the configuration of a three-plate color liquid crystal projector.

  In FIG. 17, three liquid crystal elements 50R, 50G, and 50B display black and white images having different transmission densities corresponding to the red, green, and blue component color light images, respectively. Radiated light from the light source 52 passes through a filter 53 that cuts ultraviolet rays and infrared rays to become white light including red light, green light, and blue light, and consists of a glass rod according to the illumination optical axis from the light source to the liquid crystal element. The light enters the integrator 54. The light incident surface of the integrator 54 is located in the vicinity of the focal position of the parabolic mirror used in the light source 52, and the light from the light source 52 is incident on the glass rod 54 with high efficiency.

  A relay lens 55 is disposed opposite to the emission surface of the glass rod 54, and white light from the glass rod 54 is incident on the mirror 57 as parallel light by the relay lens 55 and the subsequent collimating lens 56. The white light reflected by the mirror 57 is divided into two light beams by a dichroic mirror 58R that transmits only red light, and the transmitted red light is reflected by the mirror 59 to illuminate the liquid crystal element 50R from the back. Further, the green light and the blue light reflected by the dichroic mirror 58R are further divided into two light beams by the dichroic mirror 58G that reflects only the green light. The green light reflected by the dichroic mirror 58G illuminates the liquid crystal element 50G from the back side. The blue light transmitted through the dichroic mirror 58G is reflected by the mirrors 58B and 60, and illuminates the liquid crystal element 50B from the back.

  The liquid crystal elements 50R, 50G, and 50B are each composed of a TN liquid crystal, and a composite prism 64 is arranged so that the center is located at a position optically equidistant from the liquid crystal elements 50R, 50G, and 501B. A projection lens 65 is provided so as to face the emission surface. The composite prism 64 has two dichroic surfaces 64a and 64b inside thereof, and receives the red light transmitted through the liquid crystal element 50R, the green light transmitted through the liquid crystal element 50G, and the blue light transmitted through the liquid crystal element 50B. The combined image is incident on the projection lens 65. The projection lens 65 has its object-side focal plane coincident with the exit surfaces of the liquid crystal elements 50R, 50G, and 50B and its image-side focal plane coincides with the screen 70, so that the full color synthesized by the synthesizing prism 64 is provided. The image is formed on the screen 70.

  Polarizers 66R, 66G, and 66B are provided on the light incident surface side of the liquid crystal elements 50R, 50G, and 50B, respectively, and the retardation compensation elements 67R, 67G, and 67B of the present invention and the polarizer 68R are provided on the light output surface side. , 68G, 68B. The polarizing plates 66R, 66G, and 66B on the light incident surface side and the polarizing plates 68R, 68G, and 68B on the light emitting surface side are in a crossed Nicols arrangement, and the polarizing plate on the light incident surface side is a polarizer and the light emitting surface side. The polarizing plate acts as an analyzer. In addition, the phase difference compensation elements 67R, 67G, and 67B include the first phase difference compensation layer and the second phase difference compensation layer as described above, and the liquid crystal elements 50R, 50G, and The phase difference caused by 50B is individually compensated.

Each of the liquid crystal elements 50R, 50G, and 50B is made of a completely common TN liquid crystal, but it is generally known that the retardation (dΔn) _LC of the liquid crystal element varies depending on the wavelength. FIG. 18 shows an example of a TN liquid crystal having a liquid crystal layer thickness of 4.5 μm. The birefringence Δn changes according to the wavelength, and the retardation (dΔn) _LC changes accordingly. In the figure, Re indicates the effective retardation when the ratio of liquid crystal molecules in the vertical alignment posture when a voltage is applied to the liquid crystal is 70%, and the first retardation compensation layer described above is based on this effective retardation Re. This is to compensate for a positive phase difference. Of course, the ratio of the liquid crystal molecules in the vertical orientation varies depending on factors such as the structure of the TN liquid crystal, the thickness of the liquid crystal, the density, and the saturation voltage value, and is not limited to 70%.

FIG. 19 is a schematic view showing a structure in which 80 TiO ₂ films and SiO ₂ films having physical film thicknesses of 30 nm and 20 nm are alternately laminated in a total of 80 layers in order to effectively compensate the effective retardation Re of the TN liquid crystal. The negative retardation (d1Δn1) of one phase difference compensation layer is represented by an absolute value. Since the refractive indexes of the TiO ₂ film and the SiO ₂ film, which are the vapor deposition materials, have wavelength dependence, the wavelength dependence naturally appears in the retardation. This first phase difference compensation layer is designed to perform good phase difference compensation at 550 nm, which has high visibility in the visible light region. However, as shown in FIG. 20, optimum phase difference compensation is performed on the short wavelength side. It can be seen that there is a gap.

  Therefore, the feature of the first retardation compensation layer comprising a vapor deposition film that is sufficiently thin compared to the wavelength, that is, the negative birefringence Δn1 is determined by the refractive index and the film thickness ratio of the two types of vapor deposition films, and By utilizing the fact that the retardation value can be adjusted by adjusting the total film thickness (the number of stacked layers) multiplied by the birefringence Δn1, the present invention uses the first of the phase difference compensation elements 67R, 67G, 67B for each color channel. The thickness of the retardation compensation layer is changed. An example is shown in FIG.

In FIG. 21, the thickness of the first retardation compensation layer is changed for blue light, green light, and blue light. The vapor deposition films laminated on all channels are TiO ₂ films having physical film thicknesses of 30 nm and 20 nm. And SiO ₂ film are all common. However, for blue light, the total number of layers is 72 and the total film thickness is d1 = 1.8 μm in accordance with the retardation of TN liquid crystal of 413 nm at the reference wavelength λ = 450 nm at the center of the blue component color light. Yes. Similarly, for green light, the total number of layers is 80 with a reference wavelength λ = 550 nm, and the total thickness is d1 = 2.0 μm. For red light, the total number of layers is 82 with a reference wavelength λ = 650 nm. Thus, the total film thickness d1 = 2.1 μm.

  As a result, as shown in FIG. 22, it can be seen that the retardation of the liquid crystal elements 50R, 50G, and 50B of the respective color channels can be favorably corrected for each wavelength band of the component color light. Therefore, for example, when a blue background is projected on the entire screen 70, the entire liquid crystal element 50B is displayed in the bright state and the remaining liquid crystal elements 50R and 50G are displayed in the dark state. The positive phase difference due to the birefringence action of the liquid crystal molecules vertically aligned by the liquid crystal elements 50R and 50G is applied to the red light and green light for the phase difference compensating elements 67R and 67G. Projected with a clear blue background with no color blur, since the output light is almost eliminated from the polarizing plates 68R and 68G as the analyzer, which is compensated well by the negative retardation of the one phase difference compensation layer. Can do.

  For the same reason, the contrast ratio between when white light is projected on the entire screen 70 and when it is completely dark is improved from the conventional 500: 1 to 700: 1, and even when a general full-color image is projected, the contrast ratio is improved. Can be tightened to improve the sharpness of the image. As can be seen from FIG. 22, the wavelength dependency of retardation is weak for green light and red light compared to the first phase difference compensation layer for blue light. From this, it is also possible to apply a common layer having the same total film thickness as the first phase difference compensation layer for green light and red light. In this case, it is advantageous to determine the total film thickness on the basis of 600 nm.

As described above, when the retardation compensation element of the present invention is applied to a three-plate color liquid crystal projector, it is effective to adjust the total thickness of the first retardation compensation layer for at least two kinds of color channels. It is. The above description considers only the wavelength dependence of the retardation (dΔn) _LC of the liquid crystal elements 50R, 50G, and 50B. Each phase difference compensation element 67R, 67G, and 67B includes a second phase difference compensation layer. Is also formed. Since these second retardation compensation layers also have different reference wavelengths for each color channel, a film design corresponding to the reference wavelength is performed. However, this second retardation compensation layer exhibits a positive retardation like liquid crystal molecules. Have. Therefore, it is desirable to adjust the total film thickness of the first retardation compensation layer in a further increasing direction. Even when such adjustment is performed, the negative retardation of the first phase difference compensation layer of each color channel can be expressed by conditional expression 2 using the birefringence of each thin film material at the reference wavelength of the color channel. It will satisfy.

  The phase difference compensating elements 67R, 67G, and 67B can be disposed on the light incident surface side of the liquid crystal elements 50R, 50G, and 50B. In addition, on the light incident surface side of the liquid crystal element, a microlens array corresponding to a minute microlens for each pixel is often used together for the purpose of increasing aperture efficiency. In a liquid crystal element that uses a microlens array, the angular distribution range when incident on the liquid crystal layer is wider than the angular distribution range of illumination light incident on the microlens array at various incident angles. For the phase difference compensating action, it is advantageous to arrange the phase difference compensating elements 67R, 67G, 67B on the light emitting surface side of the liquid crystal elements 50R, 50G, 50B.

  When the phase difference compensation elements 67R, 67G, and 67B optimized for the first and second phase difference compensation layers corresponding to the reference wavelength of each color channel are used, the contrast ratio on the screen 70 becomes 1000: 1 or more. I can expect that. In addition, it is composed of only inorganic materials, so there is no problem in terms of heat resistance and light resistance, and it can be used effectively for products that are expected to be used for a long time, such as household rear projection televisions. Is possible.

  As described above, the retardation compensator and the liquid crystal projector of the present invention have been described. As the substrate for forming the retardation compensator of the present invention, various transparent inorganic materials other than the glass substrate can be used. If application to a liquid crystal projector is taken into consideration, a sapphire substrate or a quartz substrate having high thermal conductivity can be used. In addition, the first retardation compensation layer and the second retardation compensation layer are formed on separate transparent substrates, respectively. Further, as these transparent substrates, lenses, prisms, and various filters incorporated in the optical system. It is also possible to use a liquid crystal element substrate in combination.

It is a conceptual diagram of the liquid crystal display device using this invention. It is a schematic sectional drawing of the phase difference compensation element of this invention. It is a conceptual diagram which shows the layer structure of a 1st phase difference compensation layer. It is a conceptual diagram which shows the layer structure of a 2nd phase difference compensation layer. It is the schematic which shows the vapor deposition apparatus used for film-forming of an oblique vapor deposition film | membrane. It is explanatory drawing which shows the azimuth and polar angle of an oblique vapor deposition film. It is explanatory drawing which shows the optical axis vector of an oblique vapor deposition film. It is explanatory drawing which shows the layer structure of TN liquid crystal. It is explanatory drawing of a synthetic | combination vector. It is an iso-contrast curve figure of TN liquid crystal. It is an isocontrast curve figure when Example 1 of this invention is used. It is an isocontrast curve figure when Example 2 of this invention is used. It is an isocontrast curve figure when Example 3 of this invention is used. It is an isocontrast curve figure when Example 4 of this invention is used. It is an isocontrast curve figure when Example 5 of this invention is used. It is an isocontrast curve figure when Example 6 of this invention is used. 1 is a schematic view of a three-plate color liquid crystal projector using the present invention. It is a graph which shows the wavelength dependence of the retardation of TN liquid crystal. It is a graph which shows the wavelength dependence of a 1st phase difference compensation layer. It is a graph which shows the retardation characteristic of TN liquid crystal and a 1st phase difference compensation layer. It is a graph which shows the wavelength dependence of the improved 1st phase difference compensation layer. It is a graph which shows the retardation characteristic of the improved 1st phase difference compensation layer.

Explanation of symbols

2 TN liquid crystal 3,4 polarizing plate 6 retardation compensation element 10 glass substrate 12 first retardation compensation layer 14 second retardation compensation layer 15, 16 antireflection layer 22, 23 deposition material 25 electron gun 30 substrate holder 31 film thickness Monitor 32 Ellipsometer 35, 36 Substrate (liquid crystal)
35a, 36a Alignment film 38 Liquid crystal molecule 50R, 50G, 50B Liquid crystal element 58R, 58G, 58B Dichroic mirror 65 Projection lens 67R, 67G, 67B Phase compensation element 70 Screen

Claims (11)

In a phase difference compensation element that is used in combination with a TN liquid crystal cell and compensates for the angle dependency of the phase difference associated with birefringence of light rays passing through the liquid crystal layer in the TN liquid crystal cell,
A first retardation compensation layer for compensating for a phase difference caused by liquid crystal molecules vertically aligned in the liquid crystal layer; and a second retardation compensation layer for compensating for a phase difference caused by liquid crystal molecules hybrid-oriented in the liquid crystal layer. The first and second retardation compensation layers are multilayer films in which a plurality of structural birefringent bodies made of an inorganic material are laminated.   2. The retardation compensation element according to claim 1, wherein at least one of the first and second retardation compensation layers is a multilayer film laminated by a vacuum film formation method.   The second retardation compensation layer is a multilayer film in which a plurality of oblique vapor deposition films different in at least one of an azimuth angle and a polar angle in a vapor deposition direction with respect to a vapor deposition surface are laminated. Phase difference compensation element.   The retardation compensation element according to claim 1, wherein the second retardation compensation layer is composed of three or more oblique vapor deposition films. The azimuth angle of each of the oblique vapor deposition films is set to be different from the alignment azimuth angle given to the liquid crystal molecules by the alignment film of the TN liquid crystal cell,
For each obliquely deposited film, an optical axis vector is determined for each obliquely deposited film from the retardation value, azimuth and polar angle, and a composite vector A obtained by synthesizing these optical axis vectors is orthogonally projected onto the deposition surface. When the value of the xy coordinate component (Ax, Ay) is
−200 nm ≦ Ax ≦ 200 nm
−500 nm ≦ Ay ≦ 0 nm
The phase difference compensation element according to claim 1, wherein: The retardation value dΔn of the first retardation compensation layer is a product (dΔn) _LC of the thickness d and birefringence of the liquid crystal layer of the TN liquid crystal cell,
−2 × (dΔn) _LC ≦ dΔn ≦ −0.5 × (dΔn) _LC
The phase difference compensating element according to claim 1, wherein:   The first retardation compensation layer includes a vapor deposition film in which a high refractive index material and a low refractive index material are alternately stacked, and each optical film thickness is 1/100 to 1/5 of a reference wavelength. The phase difference compensating element according to claim 1, wherein the phase difference compensating element is provided.   The phase difference compensation element according to claim 1, wherein an antireflection layer is provided on at least one of the light incident surface side and the light output surface side.   A liquid crystal display device comprising the TN liquid crystal cell to be displayed combined with the phase difference compensation element according to claim 1.   9. A liquid crystal projector comprising a TN liquid crystal cell for displaying a projected image and the phase difference compensation element according to claim 1 combined therewith.   Three TN liquid crystal cells that display projected images for each of the three types of component color light are provided, and three phase difference compensation elements combined with each of the TN liquid crystal cells have letters corresponding to the reference wavelengths of the respective component color lights. The liquid crystal projector according to claim 10, comprising at least two types of phase difference compensation elements having different foundations.

Images