JP2014041192A - Reflection type liquid crystal modulation element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a reflectance ratio and contrast of a reflection type liquid crystal modulation element.SOLUTION: In a reflection type liquid crystal modulation element in which a liquid crystal layer is arranged among a first substrate, a first counter electrode disposed on the first substrate, a second substrate and a second counter electrode disposed on the second substrate in which electrode pixels in a matrix state are arranged: a groove part is disposed between the adjoining pixel electrodes; an interlayer dielectric is disposed on an undersurface of the electrode pixels and the groove part; the groove part between the pixel electrodes is filled with an insulator film from a top surface to the undersurface of the pixel electrode; and a refractive index of the insulator film in the groove part is larger than an average of the interlayer dielectric and of a normal light refractive index and an abnormal light refractive index of a liquid crystal molecule of the liquid crystal layer, so that an optical waveguide structure is formed and an evanescent light generated in the insulator film in the groove part is confined within the insulator film in the groove part. The effect of such confinement reduces diffraction/interference light reflected from the groove part and improves a refraction index and contrast.

Description

  The present invention relates to an image display element. In particular, the present invention relates to a display device that generates a modulated image according to a polarization state using a liquid crystal modulation element and converts the image pattern into an intensity-modulated image by a polarization selection unit that selects the polarization state, and particularly generates a visible image. The present invention relates to a high-resolution display device having a small pixel pitch of elements.

  Conventionally, there is a liquid crystal modulation element as a two-dimensional pixel optical switch as an image modulation means. For example, a first transparent substrate having a transparent electrode, a transparent electrode and wiring for forming a pixel, a second transparent having a switching element, and the like. A so-called TN (Twisted Nematic) liquid crystal modulation element is used in which nematic liquid crystal with positive dielectric anisotropy is sealed between the substrate and the long axis of the liquid crystal molecule is continuously twisted by 90 ° between two glass substrates. ing. In addition to such a transmissive liquid crystal modulation element, a dielectric anisotropy is formed between a transparent substrate having a transparent electrode and a circuit board having a reflecting mirror, a wiring, a switching element, etc. on one substrate as a two-dimensional optical switch. A so-called VAN (Vertical Alignment Nematic) liquid crystal type reflective liquid crystal modulation element in which nematic liquid crystal with positive characteristics is enclosed and the major axis of the liquid crystal molecule is homeotropically aligned almost perpendicularly between the two substrates. Some have.

  As a liquid crystal modulation element, a method of forming an image by using an ECB (Electrically Controlled Birefringence) effect and providing retardation to the light wave passing through the liquid crystal layer to control the action of changing the polarization state of the light wave Is mainly used.

  The design of a general liquid crystal modulation element is that linearly polarized light that oscillates in a predetermined direction by making incident light incident on a linear polarization state in a predetermined direction through incident light via a polarization control means such as a polarizer. When polarization modulation is performed when light in a state passes, a liquid crystal element based on normally white is only half a wavelength at the incident light wavelength (centroid wavelength of a certain light wavelength band) with no electric field applied to the liquid crystal. The liquid crystal device based on normally black is designed in such a manner that no liquid crystal is applied to the liquid crystal, the retardation given at the incident light wavelength is minimized, and a predetermined electric field is applied to the liquid crystal. It is designed to give retardation for only half wavelength. The light given half-wave retardation is emitted after the vibration direction is changed to a direction perpendicular to the vibration direction of the linearly polarized light before entering. Thereafter, the polarization state is selected by arranging a polarization control unit such as a polarizer having a crossed Nicol arrangement with the polarization control unit disposed on the incident side, and the selected light is transmitted. . In contrast to this design, by controlling the voltage applied to the liquid crystal layer using the ECB effect, the liquid crystal molecules cause the molecular major axis direction to tilt in the layer thickness direction of the liquid crystal layer, and the liquid crystal layer thickness direction As the birefringence amount decreases or increases, the light wave that has passed through the liquid crystal layer becomes an elliptically polarized state according to the voltage applied to the liquid crystal layer, and the vibration direction is not orthogonally converted by the polarization control means arranged on the light exit side. The light component is blocked, and the intensity of the incident light is modulated.

  In recent years, the resolution of image display devices has been increased, and the width (pixel pitch) of one pixel of the liquid crystal modulation element has been reduced. Generally, due to the two-dimensional arrangement of pixels from the optical principle, the incident light is diffracted to cause further interference, but the intensity of diffracted / interfered light is particularly strong because the width of one pixel is reduced. Become. At this time, the amount of diffracted / interfered light increases, so that the amount of display light decreases, and the black light also has a problem that leakage light increases and brightness and contrast decrease.

  In order to solve this problem, there are some known examples in which the structure in the vicinity of the pixel electrode is reviewed to prevent reduction in brightness and contrast.

  As a publicly known example, for example, oblique vapor deposition from an oblique direction to the substrate surface of the pixel electrode substrate is conventionally performed in the groove portion between the reflective pixel electrodes, and the corner portion of the pixel is shaded during vapor deposition. In addition, although a part of the groove between the pixels was not deposited and liquid crystal alignment failure occurred, as proposed in Patent Document 1, first, once on the entire bottom surface of the groove between the reflective pixel electrodes, By vertically depositing from the vertical direction to the substrate surface of the pixel electrode substrate and further obliquely depositing from the oblique direction to the substrate surface, the deposited film reaches all the grooves, preventing liquid crystal alignment defects. And the content of suppressing contrast reduction is proposed.

  Further, as proposed in Patent Document 2, a protective film (passivation film) under the reflective pixel electrode is flattened by CMP, and the reflective pixel electrode in the upper layer becomes flat following the protective film. .

  As a result, it has been proposed that the reflection pixel electrode becomes extremely flat and the reflection efficiency (brightness) can be improved by suppressing the generation of reflected scattered light.

  As described above, there is a conventional technique in which brightness and contrast are improved by reviewing the structure in the vicinity of the pixel electrode.

Japanese Patent No. 0376444 Japanese Patent No. 0864464

  However, the conventional technique proposed in Patent Document 1 allows the deposited film to reach all of the groove portions between the reflective pixel electrodes, can prevent alignment failure of the liquid crystal, and can suppress reduction in contrast. On the other hand, the alignment film structure of the pixel groove portion is a stepped structure in which the vertical vapor deposition film is at the lower stage and the oblique vapor deposition film is at the upper stage, so that the flatness cannot be sufficiently obtained, and the scattered light is generated inside the groove. Therefore, the improvement in reflectance cannot be expected.

  In the conventional technique proposed in Patent Document 2, the reflection pixel electrode is extremely flat, and it is possible to improve the reflection efficiency (brightness) by suppressing the generation of reflected scattered light.

  However, due to the recent miniaturization of the pixel electrode due to higher resolution, diffraction interference light increases, and as a result, the reflection efficiency decreases and the contrast decreases. There is no mention of each physical property value, and there is a problem that the conditions of favorable physical property values and the mention thereof are not made for improving the reflectance, and sufficient performance cannot be ensured.

  In order to solve the above problem, a first substrate, a first counter electrode provided on the first substrate, a second substrate, and a matrix electrode provided on the second substrate A reflective liquid crystal modulation element with a liquid crystal layer interposed between a second counter electrode in which pixels are arranged, and a groove is provided between the adjacent pixel electrodes, and the electrode pixel and the groove An interlayer insulating film is provided on the lower surface, and the groove between the pixel electrodes is filled with an insulating film from the upper surface to the lower surface of the pixel electrode, and the refractive index of the insulating film in the groove is The refractive index of the insulating film in the groove is larger than the average value of the ordinary light refractive index and the extraordinary light refractive index of the liquid crystal molecules of the liquid crystal layer, and the interlayer insulating film sandwiching the insulating film in the groove An optical waveguide structure is formed by being larger than the refractive index of the liquid crystal layer, and the grooves The evanescent light generated film, thereby to confine in the insulating film groove.

  Due to the confinement effect, the diffraction / interference light reflected from the groove can be reduced, and the reflectance and contrast can be improved.

  Further, the difference between the refractive index of the insulating film of the groove and the refractive index of the interlayer insulating film, and the average of the refractive index of the insulating film of the groove and the ordinary and extraordinary refractive indices of the liquid crystal molecules of the liquid crystal layer By setting the difference from the refractive index to 0.2 or more, the effect of reducing diffraction / interference light is great, and the reflectance and contrast can be improved.

  At this time, the width and thickness of the groove portion of the electrode pixel is a structure having a maximum wavelength band of visible light of 750 nm or less, or the refractive index of the interlayer insulating film is 1.2 to 1.8, When the ordinary refractive index and extraordinary refractive index of the liquid crystal molecules of the liquid crystal layer are 1.2 to 1.8, the effect of reducing diffraction / interference light is further increased, and the effect of improving reflectance and contrast is increased. .

  By the above means, the reflection type liquid crystal modulation element having the above structure, the light source, the illumination optical system for illuminating the reflection type liquid crystal modulation element with the light of the light source, and the light from the reflection type liquid crystal modulation element are expanded. The effect can be realized by using it in a projection type liquid crystal display device constituted by a projection lens system for projecting.

  Generally, due to the two-dimensional arrangement of pixels from the optical principle, the incident light is diffracted to cause further interference, but the intensity of diffracted / interfered light is particularly strong because the width of one pixel is reduced. Become. In recent years, since the resolution has increased, the intensity of diffraction / interference light of the liquid crystal modulation element has become so strong that it cannot be ignored. At this time, the amount of diffracted / interfered light increases, the amount of display light decreases, and the black display also has a problem of increased light leakage and reduced brightness and contrast. The groove between the electrodes is filled with an insulating film from the upper surface to the lower surface of the pixel electrode, and the refractive index of the insulating film in the groove is the interlayer insulating film and the ordinary refractive index and extraordinary refractive index of the liquid crystal molecules of the liquid crystal layer. By being larger than the average value, an optical waveguide structure is formed, and evanescent light generated in the insulating film in the groove is confined inside the insulating film in the groove. Due to the confinement effect, the diffraction / interference light reflected from the groove can be reduced, and the reflectance and contrast can be improved.

FIG. 3 is a diagram illustrating a cross section of the liquid crystal modulation element of Example 1. FIG. 6 is a diagram for explaining an incident plane of the liquid crystal modulation element according to the first embodiment. The figure explaining the reflectance with respect to the refractive index of the insulating film in a groove | channel of Example 1. The figure explaining the diffracted light intensity of the conventional example The figure explaining the diffracted light intensity of Example 1 The figure explaining the reflectance with respect to the insulating interlayer film of Example 2 FIG. 6 is a diagram for explaining the reflectance with respect to the refractive index of the liquid crystal layer of Example 3. FIG. 6 is a diagram for explaining a projection display device using a liquid crystal modulation element according to the present invention in Example 4.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a cross-sectional structure in the vicinity of a reflective pixel electrode of a liquid crystal modulation element,
FIG. 2 shows the surface structure of the liquid crystal modulation element.

  101 is a liquid crystal layer, 102 is an alignment film formed by oblique vapor deposition, 103 is a reflective pixel electrode, 104a and 104b are insulating interlayer films, 105 is an absorbing film, 106 is a layer composed of a number of absorbing films and insulating interlayer films, 107 is an electrode wiring layer, 108 is an insulating film filled in a groove between the reflective pixel electrodes 103, 109 is a pitch of the reflective pixel electrodes, 110 is a groove width between the reflective pixel electrodes, and an insulating film in the groove 108 width.

  At this time, the reflective pixel electrode 103 or the insulating film 108 in the groove is flat by being polished by a polishing method such as CMP (Chemical Mechanical Polishing), and the alignment film 102 obliquely deposited on the surface thereof is a lower layer. In accordance with the flatness of the reflective pixel electrode 103 and the insulating film 108 in the groove, the vapor deposition is performed in the entire region. As a result, the liquid crystal molecules of the liquid crystal layer 101 also have good orientation in the entire region following the flatness of the obliquely deposited alignment film 102, display failure does not occur, and the contrast is good.

  Regarding the structural dimensions of this embodiment, the pixel pitch 109 is 8.0 μ, the thickness of the reflective pixel electrode 103 is 0.65 μ, the groove width 110 between the reflective pixel electrodes is 0.35 μ, and the thickness of the insulating interlayer 104 a is 0.00. The thickness of the alignment film 102 of 26 μ and oblique deposition is 0.05 μ.

  Regarding the physical property values of each structure, the refractive index of the liquid crystal molecules of the liquid crystal layer 101 is 1.475 for the ordinary light refractive index No and 1.547 for the extraordinary light refractive index Ne. The average refractive index of the refractive index Ne is 1.518, the reflective pixel electrode 103 is aluminum metal, the insulating interlayer film 104a is silicon dioxide (SiO2), and the absorption film 105 is a laminated film of TiN and Ti, and the upper layer is TiN is an obliquely deposited alignment film 102, and a SiO film is deposited by depositing Si and O. In general, the physical properties of SiO have a refractive index of 2.0 and an extinction coefficient of 0.02.

  In this embodiment, the insulating film 108 in the trench is made of SiO.

  Here, FIG. 3 shows a calculation result in which the structure and physical property values of this example are reproduced by wave propagation simulation (FDTD method), and the refractive index is changed only for the insulating film 108 in the trench.

  Conventionally, no mention has been made of the conditions of physical property values of a good trench insulating film and its effect for improving the reflectivity, but regarding the special registration 0864644, SiO2 is selected as the insulating film of the trench. The refractive index of SiO2 is about 1.46, and the reflectance is 73.3% from FIG. 3, whereas the refractive index of this embodiment is 74.7% because the refractive index of SiO is 2.0. It is expected that the reflectance will be improved by about 1% compared to the conventional case.

  FIG. 4 shows a conventional diffracted light intensity result when the insulating film in the groove portion is SiO2, and FIG. 5 shows a diffracted light intensity result of the present invention when the insulating film in the groove portion is SiO. The azimuth axes in FIGS. 4 and 5 indicate the azimuth angle at which the diffracted light is emitted from the liquid crystal modulation element, and the incident vibration direction is the 0-90 degree direction. On the other hand, the vertical axis indicates the intensity of diffracted light when the incident light is 100%.

  The total amount of diffracted light intensity is 6.5% in the conventional case of FIG. 4 and 5.6% in the present invention of FIG. 5, and the intensity of the specularly reflected light is reduced by decreasing the diffracted light intensity of the present invention. Is getting stronger.

  Further, the reflectivity is 73.3% when the refractive index of the conventional trench insulating film 108 is 1.46. From FIG. 3, when the difference from the refractive index of the insulating interlayer film 104a is 0.2 or more, the refractive index is refracted. The rate is 1.66 or more, and the reflectance at that time is 74.4% or more, and a sufficient effect can be obtained.

  Constituent elements common to the first and second embodiments are denoted by the same reference numerals.

  Regarding the structural dimensions of this embodiment, the pixel pitch 109 is 8.0 μ, the thickness of the reflective pixel electrode 103 is 0.65 μ, the groove width 110 between the reflective pixel electrodes is 0.35 μ, and the thickness of the insulating interlayer 104 a is 0.00. The thickness of the alignment film 102 of 26 μ and oblique deposition is 0.05 μ.

  Regarding the physical property values of each structure, the refractive index of the liquid crystal molecules of the liquid crystal layer 101 is 1.45 for ordinary light refractive index No and 1.51 for extraordinary light refractive index Ne. The average refractive index of the refractive index Ne is 1.48, the reflective pixel electrode 103 is aluminum metal, the insulating interlayer film 104a is silicon dioxide (SiO2), and the absorption film 105 is a laminated film of TiN and Ti, and the upper layer is TiN is an obliquely deposited alignment film 102, and a SiO film is deposited by depositing Si and O. In general, the physical properties of SiO have a refractive index of 2.0 and an extinction coefficient of 0.02.

  In this embodiment, the insulating film 108 in the groove is Y2O3, and the refractive index is 1.82.

  Here, FIG. 6 shows a calculation result in which the structure and physical property values of this example are reproduced by wave propagation simulation (FDTD method) and the refractive index is changed only for the insulating interlayer film 104a.

  As shown in FIG. 6, the reflectance is higher when the refractive index of the insulating interlayer 104a is smaller. This is because the refractive index difference of the insulating film Y2O3 in the groove portion becomes larger than the refractive index of the insulating interlayer film, so that the evanescent light generated in the groove portion is easily confined in the groove and diffracted light. Will gradually decrease and the reflectivity will improve.

  Constituent elements common to the first embodiment are denoted by the same reference numerals.

  Regarding the structural dimensions of this embodiment, the pixel pitch 109 is 8.0 μ, the thickness of the reflective pixel electrode 103 is 0.65 μ, the groove width 110 between the reflective pixel electrodes is 0.35 μ, and the thickness of the insulating interlayer 104 a is 0.00. The thickness of the alignment film 102 of 26 μ and oblique deposition is 0.05 μ.

  Regarding the physical property values of each structure, the refractive index of the liquid crystal molecules of the liquid crystal layer 101 is 1.475 for the ordinary light refractive index No and 1.547 for the extraordinary light refractive index Ne. The average refractive index of the refractive index Ne is 1.51, the reflective pixel electrode 103 is aluminum metal, the insulating interlayer film 104a is silicon dioxide (SiO2), and the absorption film 105 is a laminated film of TiN and Ti, and the upper layer is TiN is an obliquely deposited alignment film 102, and a SiO film is deposited by depositing Si and O. In general, the physical properties of SiO have a refractive index of 2.0 and an extinction coefficient of 0.02.

  In this embodiment, the insulating film 108 in the trench is made of SiO.

  Here, FIG. 7 shows a calculation result in which the structure and physical property values of this example are reproduced by wave propagation simulation (FDTD method) and the refractive index is changed only for the liquid crystal layer 101.

  As shown in FIG. 7, the reflectance is higher when the refractive index of the liquid crystal layer 101 is smaller. This is because the refractive index difference of the insulating film SiO in the groove portion becomes larger than the refractive index of the liquid crystal layer 101, and the evanescent light generated in the groove portion is easily confined inside the groove. Will gradually decrease and the reflectivity will improve.

  Next, an embodiment of a projection display device using the liquid crystal modulation element of the present invention will be described with reference to FIG.

  FIG. 8 is a cross-sectional view of main optical systems constituting the embodiment of the projection display apparatus.

  A drive signal from a liquid crystal modulation element driver 303 that converts an external video input signal (not shown) into a liquid crystal modulation element drive signal is converted into a red liquid crystal modulation element 3R composed of a reflective liquid crystal element and a green liquid crystal modulation via a solid line in FIG. The element 3G and the blue liquid crystal modulation element 2B are independently controlled. On the other hand, illumination light linearly polarized and polarized in the direction perpendicular to the paper surface from the illumination means 301 of the present invention (side view is shown horizontally) is converted to magenta. The magenta green wavelength band separation dichroic mirror 305 that reflects the light and transmits the green color first deflects the magenta color component, and the deflected magenta color has a blue cross color polarizer 311 that gives half-wave retardation to the blue polarized light. The blue color component that has been linearly polarized and polarized in the horizontal direction of the paper and the label that has been linearly polarized and polarized in the vertical direction of the paper. Next, the blue color component that has entered the polarization beam splitter 310 and is linearly polarized and polarized in the horizontal direction of the paper passes through the polarization separation film for the P polarized wave, and enters the blue liquid crystal modulation element 3B. The red color component, which is guided and linearly polarized in the direction perpendicular to the paper surface, is reflected by the polarization separation film as an S-polarized wave and guided to the red liquid crystal modulation element 3R.

  On the other hand, the green color component transmitted and separated by the magenta green wavelength band separation dichroic mirror 305 passes through the dummy glass 306 for correcting the optical path length, and then enters the polarization beam splitter 307 and linearly extends in the direction perpendicular to the paper surface. The polarization-polarized green color component is reflected by the polarization splitting film due to the S-polarized wave and guided to the green liquid crystal modulation element 3G.

  With the above illumination configuration, each of the red liquid crystal modulation element 3R, the green liquid crystal modulation element 3G, and the blue liquid crystal modulation element 3G is illuminated.

  On the other hand, the light that illuminates each of the liquid crystal modulation elements 3R, 3G, and 3B by the red liquid crystal modulation element 3R, the green liquid crystal modulation element 3G, and the blue liquid crystal modulation element 3G modulated according to the video signal is red. Polarization retardation is given according to the modulation state of the pixels arranged in the liquid crystal modulation element 3R for green, the liquid crystal modulation element 3G for green, and the liquid crystal modulation element 3G for blue, and the polarization polarization component in the same direction as the illumination light Following the optical path that substantially returns the optical path, it returns to the light source lamp side, and with respect to the polarization polarization component perpendicular to the polarization direction of the illumination light, the polarization polarization direction of the modulated light by the liquid crystal modulation element 3R for red is horizontal in the drawing. The red cross-color polarization which passes through the polarization separation film of the polarization beam splitter 301 for the P-polarized wave and then gives half-wave retardation to the red polarized light. The red color component passing through the element 312 is converted into a red color component that is linearly polarized and polarized in the direction perpendicular to the plane of the paper, and then enters the polarization beam splitter 308 and the red color component that is linearly polarized and polarized in the direction perpendicular to the plane of the paper is converted into a polarization separation film. Is reflected by the S-polarized wave and is deflected in the direction of the projection optical system 304.

  The modulated light by the blue liquid crystal modulation element 3B has a polarization polarization direction perpendicular to the paper surface, reflects the polarization separation film of the polarization beam splitter 310 due to the S-polarized wave, and then half-wave retardation into red polarized light The blue color component that has passed through the red cross color polarizer 312 that gives the light and is incident on the polarization beam splitter 308 and linearly polarized in the direction perpendicular to the plane of the paper passes through the polarization separation film. Therefore, it is reflected and deflected in the direction of the projection optical system 304.

  The light modulated by the green liquid crystal modulation element 3G has a polarization polarization direction horizontal to the paper surface, passes through the polarization separation film of the polarization beam splitter 307 for the P-polarized wave, and then is a dummy glass for correcting the optical path length. The green color component that has passed through 309 and then enters the polarization beam splitter 308 and linearly polarized and polarized in the horizontal direction on the paper passes through the polarization separation film as a P-polarized wave and is guided in the direction of the projection optical system 304. It is burned. However, a plurality of arranged pixels in each of the red liquid crystal modulation element 3R, the green liquid crystal modulation element 3G, and the blue liquid crystal modulation element 3G are adjusted or mechanically adjusted so that the predetermined pixels overlap with a predetermined accuracy. Needless to say, it is electrically compensated. Next, the light modulated as the combined color color is captured as it is by the entrance pupil of the projection optical system 304, and the light from each of the liquid crystal modulation element 3R for red, the liquid crystal modulation element 3G for green, and the liquid crystal modulation element 3G for blue. Since the modulation surface and the light diffusion surface of the light diffusion screen 313 are arranged in an optical conjugate relationship by the projection optical system 304, the image is transferred to the light diffusion screen 313 and an image based on the video signal is displayed on the light diffusion screen 313. It is what is displayed.

  At this time, the liquid crystal modulation element 3R for red, the liquid crystal modulation element 3G for green, and the liquid crystal modulation element 2B for blue are vertical alignment mode reflection type liquid crystal modulation elements.

101 liquid crystal layer, 102 oblique deposition film, 103 reflective pixel electrode, 104-a insulating interlayer film, 104-b insulating interlayer film, 105 absorbing film, 106 absorbing film / insulating interlayer film, 107 electrode wiring layer, 108 reflecting pixel electrode Between pixel grooves, 109 Reflection pixel electrode pitch, 110 Reflection pixel electrode width

Claims (5)

A first substrate, a first counter electrode provided on the first substrate, a second substrate, and a second counter electrode in which electrode pixels are arranged in a matrix provided on the second substrate Between
A reflective liquid crystal modulation element through a liquid crystal layer,
A groove portion is provided between the adjacent pixel electrodes, an interlayer insulating film is provided on the lower surface of the electrode pixel and the groove portion, and a groove portion between the pixel electrodes is formed on the pixel electrode. Filled with an insulating film from the upper surface to the lower surface, the refractive index of the insulating film in the groove is greater than the average value of the ordinary refractive index and extraordinary light refractive index of the liquid crystal molecules of the interlayer insulating film and the liquid crystal layer A reflection-type liquid crystal modulation element. The difference between the refractive index of the insulating film in the groove and the refractive index of the interlayer insulating film, and the average of the refractive index of the insulating film in the groove and the ordinary and extraordinary refractive indices of the liquid crystal molecules in the liquid crystal layer The reflection type liquid crystal modulation element according to claim 1, wherein the difference from the refractive index is 0.2 or more. 3. The reflective liquid crystal modulation element according to claim 1, wherein a width and a thickness of the groove portion of the electrode pixel are structures having a maximum wavelength band of visible light of 750 nm or less. The refractive index of the interlayer insulating film is 1.2 to 1.8, and the ordinary refractive index and extraordinary refractive index of liquid crystal molecules of the liquid crystal layer are 1.2 to 1.8. The reflective liquid crystal modulation element according to any one of claims 1 to 3. 5. A light source, an illumination optical system for illuminating the reflection type liquid crystal modulation element with light from the light source, a projection lens system for enlarging and projecting light from the reflection type liquid crystal modulation element, and claims 1 to 4. A projection type liquid crystal display device comprising the reflective liquid crystal modulation element according to claim 1.