JP2008076802A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce display unevenness of e.g. a liquid crystal projector. <P>SOLUTION: A driving voltage Vb is applied to a liquid crystal layer 50 according to turning on/off of a TFT 30 in each pixel during operation of a liquid crystal device 1 and blue light is modulated in the liquid crystal layer 50. The liquid crystal device 1 has a peak of illumination or a peak of transmittance in a center region Rc of a visual field angle characteristic figure about blue light. In an liquid crystal panel 1,110B, luminance unevenness of an image display region 10a is suitably reduced without providing an optical system for optical compensation such as a phase difference plate about blue light to be modulated and manufacturing and component costs of the liquid crystal panel 1,110B can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technical field of a projector including, for example, three liquid crystal light valves that modulate red light, green light, and blue light.

  A liquid crystal projector, which is an example of this type of projector, includes, for example, three liquid crystal light valves that modulate red light, green light, and blue light, and the light modulated by each light valve is transmitted by an optical system. By combining, a color image is projected onto a projection surface such as a screen. In such a liquid crystal projector, each of the three light valves includes a liquid crystal layer containing liquid crystal molecules of the same type, and each liquid crystal layer has the same drive mode (for example, TN (Twist Nematic) mode, VA ( Vertical Alignment) mode). For example, in the case of an active matrix type liquid crystal device, the liquid crystal device provided in such a liquid crystal projector includes a drive circuit including a liquid crystal panel, an image signal processing circuit, and a timing generation circuit.

  Among these, the liquid crystal panel is configured by sandwiching liquid crystal between an element substrate and a counter substrate. A plurality of data lines and a plurality of scanning lines are formed on the element substrate, and thin film transistors (hereinafter referred to as TFTs) functioning as switching elements are provided corresponding to the intersections thereof. Further, the image signal processing circuit performs gamma correction processing (hereinafter referred to as drive voltage) for converting input image data within a certain range in accordance with the characteristics of transmittance with respect to the applied voltage of the liquid crystal used in the liquid crystal panel. It has become. Further, the timing generation circuit outputs a timing signal used in each unit.

  In this type of projector, the upper limit of the driving voltage of the liquid crystal is fixed to a constant value in order to simplify the driving circuit and versatility of components, and each color is controlled within the same voltage range. The upper limit value of the control range is the same fixed value for each color for the same reason. In general, parameters such as the cell thickness of the liquid crystal panel and the liquid crystal material are designed to be the same for each color. For this reason, the upper limit of the driving voltage of the liquid crystal that modulates the other colors is aligned with the voltage and wavelength that reach the peak of transmittance the earliest.

  However, due to the influence of chromatic dispersion of liquid crystal molecules, the transmittance peak with respect to the driving voltage of the liquid crystal has a characteristic that it varies depending on the transmitted color light. From this feature, the luminance distribution does not appear in the central area but appears in a biased area except for the liquid crystal panel that modulates the color light that reaches the peak of transmittance. Therefore, when the respective color lights are combined, non-uniformity resulting from the uneven luminance distribution occurs in the combined region.

  Such non-uniformity of the luminance distribution is generically called luminance unevenness. In order to reduce luminance unevenness of a liquid crystal device used as a light valve, as disclosed in Patent Documents 1 and 2, a technique using a retardation plate is known.

JP-A-6-51305 JP 2001-42314 A

  In this type of projector, the three liquid crystal light valves that modulate light of each color usually have the same panel structure using the same type of liquid crystal for the versatility of the components. In view of the demand for simplification of the drive circuit and versatility, the upper limit of the voltage applied to the liquid crystal of each pixel is often set to be the same depending on whether the pixel switching TFT is turned on or off.

  However, when each of light having different wavelengths such as red light, green light and blue light is incident on a liquid crystal light valve having the same panel structure using the same type of liquid crystal, due to the wavelength dispersion characteristics of the liquid crystal molecules, Depending on the difference in wavelength of the light, the optical characteristics such as the transmittance of the liquid crystal light valve or the luminance distribution in the display area are different. According to such a difference in optical characteristics, when a projection image obtained by synthesizing modulated light modulated by each liquid crystal light valve is projected onto a projection surface such as a screen, display unevenness occurs in the projection image, and projection is performed. There is a problem that the display quality of the image is deteriorated. In addition, as disclosed in Patent Documents 1 and 2, even if a retardation plate is provided to reduce luminance unevenness of the liquid crystal light valve, a reduction in transmittance due to the interposition of the retardation plate is inevitable. There is also a problem that the product cost increases due to an increase in the number of parts constituting the projector and a complicated manufacturing process.

  Therefore, the present invention has been made in view of the above problems and the like, and provides a projector capable of reducing the product cost without reducing the brightness, and improving the quality of the projected image, for example. This is the issue.

  In order to solve the above problems, a projector according to the present invention applies a first drive voltage to a first liquid crystal layer to modulate a first color light, and a second drive different from the first drive voltage. A second liquid crystal device for applying a voltage to the second liquid crystal layer to modulate a second color light different from the first color light, wherein the first drive voltage is based on a viewing angle characteristic of the first liquid crystal device. The second driving voltage is set based on the viewing angle characteristics of the second liquid crystal device.

  According to the projector of the present invention, the first liquid crystal device and the second liquid crystal device are liquid crystal light valves used for, for example, a liquid crystal projector. The first liquid crystal device modulates the first color light and emits modulated light corresponding to the first color light. The second liquid crystal device modulates the second color light and emits modulated light corresponding to the second color light. A display image is projected onto a screen or the like by combining the modulated light emitted from these liquid crystal devices.

  Each of the first drive voltage and the second drive voltage is a drive voltage for driving each of the first liquid crystal layer and the second liquid crystal layer, and transitions from the black display state to the white display state by controlling the drive voltage. To do. For example, in a black display state, a state where the voltage is 0 V is referred to as a normally black state. In a normally black state liquid crystal device, in order to change to a white display state, a voltage corresponding to the transmittance is applied. To do. At this time, the luminance of the liquid crystal device is determined by the upper limit value of the applied voltage, that is, the upper limit value of the drive voltage.

  The upper limit of the first drive voltage and the second drive voltage is different from each other, and is set according to each of the first color light and the second color light based on the viewing angle characteristics of these liquid crystal devices. According to the first drive voltage and the second drive voltage as described above, the brightness distribution of the projected image formed by combining the modulated light emitted from each of the first and second liquid crystal devices can be made uniform. It is possible to improve the display quality without generating. The viewing angle characteristic is a characteristic derived from the transmittance of the liquid crystal device corresponding to the angular distribution of light incident on the liquid crystal device when a predetermined driving voltage is applied to the liquid crystal layer.

  According to the projector of the present invention, an increase in cost due to provision of optical compensation means such as a retardation plate can be suppressed, so that the product cost can be reduced and a high-quality image can be displayed.

  In one aspect of the projector according to the present invention, the first drive voltage is set according to a position or a width of a region where the first liquid crystal device has a high transmittance with respect to the first color light. The driving voltage may be set according to a position or a width of a region where the second liquid crystal device has a high transmittance with respect to the second color light.

  According to this aspect, in the first liquid crystal device, the high transmittance region is located in a wide range including the central region of the viewing angle characteristic diagram for the first color light, and the first liquid crystal device modulates the first color light. The luminance unevenness in the display area that emits the modulated light is reduced. More specifically, in this aspect, the voltage at which the transmittance of the liquid crystal device that modulates the specific wavelength light is the highest based on the voltage at the peak of the transmittance of the conventional specific wavelength light is used as the upper limit of the drive voltage. Compared to the case where the first driving voltage is set, the first driving voltage is set so that the first liquid crystal device has a high transmittance region in a wide range with respect to the first color light. Also in the second liquid crystal device, as in the first liquid crystal device, the second drive voltage is set so that the second liquid crystal device has a high transmittance region in a wide range with respect to the second color light. Therefore, according to this aspect, in each liquid crystal device, the high transmittance region is located in a wide region including the central region of the viewing angle characteristic diagram, and the respective display regions of the first liquid crystal device and the second liquid crystal device. Is relatively reduced as compared with the case where the high transmittance region is not located in the central region and the case where the range where the high transmittance region and the central region overlap is small. Luminance unevenness of a projected image formed by combining modulated light emitted from each of the liquid crystal devices is reduced. According to this aspect, it is possible to reduce the cost of components required for optical compensation means such as a retardation plate, and it is possible to display a high-quality image with reduced luminance unevenness.

  In the present specification, such a characteristic is illustrated as a plan view, and a diagram in which the transmittance of the liquid crystal device, that is, the luminance is mapped, is referred to as a “viewing angle characteristic diagram”.

  By the way, in the case of nematic liquid crystal, for example, liquid crystal molecules can be represented by an ellipsoid such as a rugby ball, which is called a refractive index ellipsoid. When light is incident on such a nematic liquid crystal, the major axis and minor axis length of the cross section passing through the origin of the refractive index ellipsoid become the respective refractive indices, and the difference in refractive index between the major axis and the minor axis is obtained. Birefringence. When the refractive index ellipsoid is viewed from the optical axis direction, the cross section is a circle, so that the major axis and the minor axis are the same length, and birefringence does not occur. Furthermore, when the incident angle of light is shifted from the optical axis direction, the ratio of the major axis to the minor axis in the cross section increases, and the birefringence increases. Thus, the fact that the birefringence changes depending on the incident angle of light is the cause of the liquid crystal device having a viewing angle.

  The “viewing angle” means an observation direction defined by an azimuth angle which is an in-plane direction of a plane parallel to the display area of the liquid crystal device and a viewing angle inclined with respect to the normal line of the plane. The viewing angle characteristic diagram shows the illuminance distribution on a plane defined by, for example, the azimuth angle and the viewing angle. Such a viewing angle characteristic diagram is an experimental mapping of data obtained by actually measuring the illuminance in the display area of the liquid crystal device while fluctuating the voltage applied to the liquid crystal layer of the liquid crystal device. Or the figure which mapped the data of the illumination intensity computed by simulating the illumination intensity according to the voltage applied to a liquid-crystal layer may be sufficient.

  The viewing angle characteristic can be represented by an isoluminance curve in the viewing angle characteristic diagram. The isoluminance curve is obtained by connecting angles at which luminance is constant with a line. The isoluminance curve indicates that when viewed from the front, the image is tilted in that direction as the distance from the central region increases. Further, in order to express the relationship with the applied voltage, it is acquired for each different voltage.

  In another aspect of the projector according to the present invention, the first liquid crystal device modulates one color light of red light, green light, and blue light, and the second liquid crystal device includes the red light, the green light, and Of the blue light, two color lights excluding the one color light may be modulated.

  According to this aspect, each of the three liquid crystal light valves can modulate red light, green light, and blue light, and can display a high-quality projected image in color.

  In another aspect of the projector according to the present invention, the projector further includes a third liquid crystal device that modulates third color light by applying a third drive voltage to the third liquid crystal layer, and the third drive voltage is the third liquid crystal. You may set based on the viewing angle characteristic of an apparatus.

  According to this aspect, for example, it is possible to display a high-quality color image with reduced luminance unevenness using three light valves corresponding to red light, green light, and blue light, respectively.

  In another aspect of the projector according to the present invention, the third drive voltage may be set according to a position or a width of a region where the third liquid crystal device has a high transmittance with respect to the third color light.

  According to this aspect, it is possible to display a high-quality color image in which display unevenness is reduced by synthesizing an image in which brightness unevenness is prevented for each of red light, green light, and blue light, for example.

  In another aspect of the projector according to the present invention, each of the first to third liquid crystal devices modulates one color light of red light, green light, and blue light, and each modulates a different color. Good.

  According to this aspect, it is possible to display a high-quality color image with reduced display unevenness.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

  Hereinafter, embodiments of a projector according to the present invention will be described with reference to the drawings.

<1: Projector>
Next, the projector according to the present embodiment will be described with reference to FIGS. 1 and 13. FIG. 1 is a plan view showing the configuration of the projector. In the following, blue light is an example of “first color light” of the present invention, and each of red light and green light is an example of “second color light” of the present invention, or “third color light”. is there. The liquid crystal panel 1110B is an example of the “first liquid crystal device” of the present invention, and the liquid crystal panel 1110R and the liquid crystal panel 1110G are examples of the “second liquid crystal device” of the present invention, or the “third liquid crystal device”. It is an example. In the present embodiment, a three-plate projector is described, but the number of light valves provided in the projector is not limited to three, and may be two or four or more.

  In FIG. 1, a projector 1100 includes a lamp unit 1102 and liquid crystal panels 1110R, 1110G, and 1110B.

  Inside the projector 1100, a lamp unit 1102 made of a white light source such as a halogen lamp is provided. The projection light emitted from the lamp unit 1102 is separated into light of wavelengths corresponding to the three primary colors of RGB by the four mirrors 1106 and the two dichroic mirrors 1108 arranged in the light guide 1104, and corresponds to each color. Is incident on the liquid crystal panels 1110R, 1110B and 1110G as light valves.

  The liquid crystal panels 1110R, 1110B, and 1110G have the same configuration using the same type of liquid crystal, and are applied to the liquid crystal layer according to the R, G, and B color signals supplied from the image signal processing circuit. Each of red light (R), green light (G), and blue light (B) is modulated by the driving voltage.

  Here, as shown in FIG. 13, the upper limit of the driving voltage is controlled by the driving voltages Vr, Vg, and Vb in the liquid crystal layers included in the liquid crystal panels 1100R, 1100G, and 1100B, respectively. In the present embodiment, the drive voltage Vb is an example of the “first drive voltage” in the present invention, and each of the drive voltages Vr and Vg is an example of the “second drive voltage” in the present invention. Further, when the drive voltage Vr is an example of the “second drive voltage” in the present invention, the drive voltage Vg is an example of the “third drive voltage” in the present invention. Further, transmittance peaks corresponding to the upper limits of the drive voltages Vr, Vg, and Vb are Tr, Tg, and Tb, respectively. At this time, the liquid crystal panels 1110R, 1110B, and 1110G are set so that the viewing angle characteristics of the liquid crystal panels 1110R, 1110G, and 1110B are the best for each of red light, green light, and blue light. . More specifically, by setting the upper limit of the driving voltages Vr, Vg, and Vb of the liquid crystal panels 1100R, 1100G, and 1100B with the peak of transmittance for each liquid crystal panel, the high transmittance region in the viewing angle characteristic diagram is centered. It is set so as to overlap and widen in the area. According to such driving voltages Vr, Vg, and Vb, it is possible to reduce unevenness in the brightness of the projected image formed by combining the modulated lights emitted from the liquid crystal panels 1100R, 1100G, and 1100B, and to improve the display quality of the projected image. It is possible to increase.

  The light modulated by these liquid crystal panels enters the dichroic prism 1112 from three directions. In this dichroic prism 1112, R and B light are reflected at 90 degrees, while G light travels straight, and an image displayed by each color light is synthesized. As a result, luminance is applied to the screen via the projection lens 1114. A high-quality color image with reduced unevenness is projected. When attention is paid to the display images by the liquid crystal panels 1110R, 1110B, and 1110G, the display image by the liquid crystal panel 1110G is horizontally reversed with respect to the display images by the liquid crystal panels 1110R and 1110B.

  Since light corresponding to each color of R, G, and B is incident on the liquid crystal panels 1110R, 1110B, and 1110G by the dichroic mirror 1108, it is not necessary to provide a color filter.

  In addition, according to the projector 1100, the liquid crystal panels 1110R, 1110B, and 1110G can reduce luminance unevenness generated in the liquid crystal panels 1110R, 1110G, and 1110B without providing optical compensation means such as a retardation plate. Further, it is possible to reduce manufacturing costs and component costs which are increased by providing an optical system for optical compensation that reduces luminance unevenness of each liquid crystal panel.

<2: LCD panel>
Next, the configuration of the liquid crystal panel included in the projector 1100 described above will be described with reference to FIGS. Since the panel structures of the liquid crystal panels 1110R, 1110G, and 1110B are the same as each other, description of the panel structures of the liquid crystal panels 1110R and 1110G will be omitted below. However, the drive voltages Vr, Vg, and Vb for driving the liquid crystal panels 1110R, 1110G, and 1110B will be described in detail with reference to the viewing angle characteristic diagrams corresponding to the liquid crystal panels.

  FIG. 2 is a plan view of the liquid crystal panel 1110B viewed from the counter substrate side. 3 is a cross-sectional view taken along the line HH ′ of FIG. FIG. 4 is an equivalent circuit of various elements, wirings, and the like in a plurality of pixels formed in a matrix that forms the image display area of the liquid crystal panel 1110B. FIG. 5 is a schematic plan view of a liquid crystal panel whose clear vision direction is indicated by an arrow. Here, the liquid crystal panels 1110R, 1110G, and 11110B are TFT active matrix driving type liquid crystal panels with a built-in driving circuit, and use liquid crystal molecules having negative dielectric anisotropy. Accordingly, the liquid crystal panels 1110R, 1110G, and 1110B are liquid crystal panels in which liquid crystal molecules are driven in a vertical alignment (VA) mode. FIG. 6 is a view angle characteristic diagram showing the view angle characteristic of the liquid crystal panel 1110B. FIG. 7 is a schematic perspective view showing an observation direction (viewing angle) defined by an azimuth angle and a viewing angle.

  2 and 3, in the liquid crystal panel 1110B, the TFT array substrate 10 and the counter substrate 20 are disposed to face each other. A liquid crystal layer 50 is sealed between the TFT array substrate 10 and the counter substrate 20, and the TFT array substrate 10 and the counter substrate 20 are provided with a sealing material 52 provided in a seal region positioned around the image display region 10a. Are bonded to each other.

  The sealing material 52 is made of, for example, an ultraviolet curable resin, a thermosetting resin, or the like for bonding the two substrates, and is applied on the TFT array substrate 10 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like. It is. In the sealing material 52, a gap material 56 such as glass fiber or glass beads for dispersing the distance (inter-substrate gap) between the TFT array substrate 10 and the counter substrate 20 to a predetermined value is dispersed. Therefore, the liquid crystal panel 1110B has a uniform gap, and is suitable for a small and enlarged display for a projector light valve.

  A light-shielding frame light-shielding film 53 that defines the frame area of the image display area 10a is provided on the counter substrate 20 side in parallel with the inside of the seal area where the sealing material 52 is disposed. Of the peripheral regions located around the image display region 10 a, the data line driving circuit 101 and the external circuit connection terminal 102 are arranged on one side of the TFT array substrate 10 in the region located outside the seal region where the sealing material 52 is disposed. It is provided along. The scanning line driving circuit 104 is provided along one of the two sides adjacent to the one side so as to be covered with the frame light shielding film 53. The scanning line driving circuit 104 may be provided along two sides adjacent to one side of the TFT array substrate 10 provided with the data line driving circuit 101 and the external circuit connection terminal 102. In this case, the two scanning line driving circuits 104 are connected to each other by a plurality of wirings provided along the remaining one side of the TFT array substrate 10.

  Vertical conductive members 106 functioning as vertical conductive terminals between the two substrates are disposed at the four corners of the counter substrate 20. On the other hand, the TFT array substrate 10 is provided with vertical conduction terminals in a region facing these corner portions. Thus, electrical conduction can be established between the TFT array substrate 10 and the counter substrate 20.

  As shown in FIG. 5, the clear viewing direction of the liquid crystal panel 1110B is the 1:30 direction. The liquid crystal molecules contained in the liquid crystal layer 50 are inclined toward the clear viewing direction according to the drive voltage Vb applied to the liquid crystal layer 50 when the liquid crystal panel 1110B is operated.

  In FIG. 3, on the TFT array substrate 10, an alignment film 16 is formed on the pixel electrode 9a after the pixel switching TFT, the scanning line, the data line and the like are formed. On the other hand, in the liquid crystal panel 1110B, a counter electrode (not shown) formed on the counter substrate 20 is disposed so as to oppose the pixel electrode 9a, and an alignment film 22 is formed on the counter electrode. For the TFT array substrate 10 and the counter substrate 20, for example, a transparent substrate such as quartz or plastic is used.

  On the TFT array substrate 10 or the counter substrate 20, the alignment film 16 or 22 is formed of an organic material such as polyimide. In this embodiment, the alignment film is formed only on one of the TFT array substrate 10 and the counter substrate 20, or the alignment film formed on one of these is formed of an inorganic material. Good.

  The liquid crystal layer 50 includes liquid crystal molecules having negative dielectric anisotropy and is driven in the VA mode. When the liquid crystal panel 1110B is used, polarizing plates are arranged on both sides of the liquid crystal layer 50 so that the polarization axes are orthogonal to each other, and modulates blue light in a normally black mode (black display).

  Next, a circuit configuration in the image display area 10a of the liquid crystal panel 1110B will be described with reference to FIG.

  In FIG. 4, a pixel electrode 9a and a TFT 30 for controlling the switching of the pixel electrode 9a are formed in each of the plurality of pixels formed in a matrix that forms the image display region 10a of the liquid crystal panel 1110B. The data line 6a to which the image signal is supplied is electrically connected to the source of the TFT 30. The image signals S1, S2,..., Sn to be written to the data lines 6a may be supplied line-sequentially in this order, or may be supplied for each group to a plurality of adjacent data lines 6a. May be.

  The gate of the TFT 30 is electrically connected to the gate electrode 3a, and the scanning signals G1, G2,..., Gm are pulse-sequentially applied in this order to the scanning line 11a and the gate electrode 3a at a predetermined timing. The liquid crystal panel 1110B is configured to be applied. The pixel electrode 9a is electrically connected to the drain of the TFT 30, and the image signal S1, S2,... Supplied from the data line 6a is closed by closing the switch of the TFT 30 serving as a switching element for a certain period. Sn is written at a predetermined timing.

  Image signals S1, S2,..., Sn written to the liquid crystal via the pixel electrode 9a are held for a certain period between the pixel electrode 9a and the counter electrode formed on the counter substrate 20. . Thus, a driving voltage is applied to the liquid crystal in each pixel according to the potential difference between the pixel electrode 9a and the counter electrode 21. The liquid crystal modulates light and enables gradation display by changing the orientation and order of the molecular assembly depending on the applied voltage level. In the present embodiment, since the display method of the liquid crystal panel 1110B is a normally black mode, the transmittance for incident light incident on the pixels from the light source side depends on the drive voltage Vb applied to the liquid crystal in units of each pixel. As a whole, light having a contrast corresponding to the image signal is emitted from the liquid crystal panel 1110B.

  Further, in order to prevent the retained image signal from leaking, in the liquid crystal panel 1110B, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9a and the counter electrode 21. The storage capacitor 70 is provided side by side with the scanning line 11a, and includes a fixed potential side capacitor electrode and a capacitor electrode 300 fixed to a constant potential. With such a circuit configuration, the liquid crystal panel 1110B displays an image.

  Next, viewing angle characteristics of the liquid crystal panel 1110B will be described with reference to FIG. In FIG. 6, equal illuminances in the image display area 10a are connected by the same kind of line.

  As shown in FIG. 6, when the liquid crystal panel 1110B operates, the liquid crystal layer 50 modulates blue light by applying a drive voltage Vb to the liquid crystal layer 50 in accordance with on / off of the TFT 30 in each pixel. The liquid crystal panel 1110B has a high illuminance region including an illuminance peak in the central region Rc of the viewing angle characteristic diagram for blue light, in other words, a high transmittance region, and is hatched with a diagonal line in the drawing including the illuminance peak. This region is a high transmittance region Rb at the drive voltage Vb. Such a high transmittance region Rb is wider than the high transmittance region in the viewing angle characteristics measured when the liquid crystal layer 50 is driven by a voltage different from the drive voltage Vb, for example. A wide area overlapping the central area Rc (specifically, the area including the center and having a viewing angle of about ± 12 °) is the high transmittance area.

  Therefore, according to the liquid crystal panel 1110B, since the wide region overlapping the central region Rc is covered with the high transmittance region, the viewing angle dependency of the transmittance for blue light to be modulated is reduced, and a retardation plate or the like. Without providing the optical system for optical compensation, luminance unevenness in the image display area 10a is correspondingly reduced. Therefore, according to the liquid crystal panel 1110B, it is possible to reduce the manufacturing and component costs of the liquid crystal panel 1110B and display a high-quality image. In addition, since the liquid crystal layer 50 includes liquid crystal molecules that are driven in the vertical alignment (VA) mode, the liquid crystal panel 1110B can display an image with a higher contrast than in other drive modes.

  The projector according to the present invention is not limited to the liquid crystal panel driven in the VA mode, and a liquid crystal panel driven in another drive mode such as the TN mode may be used.

  In the present embodiment, the “viewing angle” means an orientation defined by an azimuth angle φ and a viewing angle ψ in the image display area 10a as shown in FIG. The azimuth angle φ is a reference line in the plane S (shown in the plane S in the figure) that is a projection line obtained by projecting a line connecting the center point C0 of the image display area 10a and the observer onto the parallel plane S of the image display area 10a. It is the angle formed with the dashed-dotted line. The viewing angle ψ is an angle formed by a line connecting the center point C0 of the image display area 10a and the observer with the normal line Ln of the surface S.

<3: Driving voltage setting method>
Next, a driving voltage setting method for setting the driving voltage Vb for driving the liquid crystal layer 50 described above will be described with reference to FIGS. 8 to 10 and FIG. FIG. 8 is a flowchart of a voltage setting method for setting the drive voltage Vb. FIG. 9 is a view angle characteristic diagram obtained by simulating the view angle characteristic acquired when the liquid crystal panel 1110B modulates blue light, and the voltages (0, 1, 2) applied to the liquid crystal layer 50 are shown. 3, 4, 5 V) is a list of viewing angle characteristic diagrams obtained. In the viewing angle characteristic diagram corresponding to each voltage in FIG. 9, equal illuminance in the image display region 10a is shown connected by the same kind of line. Therefore, in each of the viewing angle characteristic diagrams corresponding to different voltages, the actual measured value of illuminance indicated by the same kind of line or the specific value of illuminance obtained by the simulation is different for each voltage.

  In FIG. 9, the viewing angle ψ is 0 ° at the center point C of the viewing angle characteristic diagram corresponding to each voltage. Therefore, in FIG. 9, the illuminance at the center point C means the illuminance when the image display area 10a is viewed from directly above. FIG. 10 is a graph showing the illuminance with respect to the viewing angle for each voltage applied to the liquid crystal layer 50 when observed from the clear viewing direction shown in FIG.

  In FIG. 8, the viewing angle characteristic of the liquid crystal panel 110B is acquired (step S10). More specifically, by measuring or simulating the viewing angle characteristics of the liquid crystal panel 1110B for each voltage (0, 1, 2, 3, 4, 5V) applied to the liquid crystal layer 50, a field of view corresponding to each voltage. An angular characteristic diagram (see FIG. 9) is calculated.

  As shown in FIG. 9, by increasing the voltage applied to the liquid crystal layer 50, a region with high illuminance, in other words, a high transmittance region Rb with high transmittance in the image display region 10a is based on the center point C. In the figure, there is a gradual shift from the lower left side to the upper right side, and the area tends to increase. In FIG. 9, the central region Rc including the center point C overlaps with the region with the highest illuminance, that is, the high transmittance region Rb, when a voltage of 3 to 4 V is applied to the liquid crystal layer 50. In addition, the high transmittance region Rb is also wider than other voltages. However, the high transmittance region Rb increases when the voltage applied to the liquid crystal layer 50 is 5 V compared to when the voltage is 3 to 4 V. However, when the voltage is 5 V, the high transmittance region does not overlap with the center point C, and the overlap with the center region Rc becomes small. That is, the viewing angle dependency is not reduced as compared with the case where the voltage is 3 to 4V. Therefore, it is preferable to set 3 to 4 V as the upper limit of the drive voltage.

  In FIG. 9, the transmittance (illuminance) of the high transmittance region Rb at each voltage (0, 1, 2, 3, 4, 5 V) is different for each voltage. (3, 4, 5V), the luminance is relatively compared.

  Again, in FIG. 8, based on the viewing angle characteristic diagram shown in FIG. 9, the voltage having the transmittance peak in the widest range for blue light is set as the drive voltage Vb (step S20). More specifically, the drive voltage Vb corresponding to Tb shown in FIG. 13 is set to a voltage in the range of 3 to 4V. According to such a drive voltage Vb, in the viewing angle characteristic diagram, the area where the high transmittance region Rb overlaps the central region Rc is relatively larger than other voltages, and the area of the high transmittance region Rb is also large. . Accordingly, in the viewing angle characteristic diagram, the wider the range in which the central region Rc is covered with the same illuminance, the less the luminance unevenness corresponding to the viewing angle characteristic of the liquid crystal device is reduced. Even if it is not provided, luminance unevenness in the image display area 10a observed for each viewing angle is reduced.

  According to such a driving voltage setting method, based on the voltage at the time of the peak transmittance in the conventional specific wavelength light, the voltage at which the liquid crystal device that modulates the specific wavelength light has the highest transmittance is set as the upper limit of the drive voltage. Compared to the case where the same value is adopted, it is possible to set the drive voltage Vb that can relatively reduce the luminance unevenness of the liquid crystal panel.

  According to such a drive voltage Vb, it is possible to reduce luminance unevenness of the liquid crystal device 1 and improve the display quality of an image displayed by the liquid crystal panel 1110B.

  In the present embodiment, the viewing angle characteristic of the liquid crystal panel 110B1 is obtained by simulation. Refer to the viewing angle characteristic diagram showing the viewing angle characteristic obtained by actually measuring the illuminance of the image display region 10a. It is also possible to set the drive voltage Vb. In addition, by defining a range in which the viewing angle ψ is defined in the range of about ± 12 ° as the central region Rc, luminance unevenness of the liquid crystal panel can be effectively reduced practically.

  Next, a method for setting the drive voltages Vr and Vg for driving the liquid crystal layers included in the liquid crystal panels 1110R and 1110G will be described with reference to FIGS. Since the procedure for setting the drive voltages Vr and Vg is the same as the procedure for the drive voltage setting method described above, the visual field of the liquid crystal panels 1110R and 1110G referred to when setting the drive voltages Vr and Vg will be described below. The angular characteristics will be described. FIG. 11 is a view angle characteristic diagram of the liquid crystal panel 1110B acquired for red light, and FIG. 12 is a view angle characteristic diagram of the liquid crystal panel 1110B acquired for green light. Each of FIGS. 11 and 12 is a view angle characteristic diagram simulated for each different voltage (0, 1, 2, 3, 4, 5 V) applied to the liquid crystal layer 50 as in FIG. It is a list.

  In FIG. 11, in the modulated red light, the region with the highest illuminance, that is, the high transmittance region Rr, as in the blue light, increases from the lower left side in the drawing as the voltage applied to the liquid crystal layer 50 is increased. It tends to shift to the upper right side. However, as shown in FIG. 11, unlike blue light, for red light, if the driving voltage for driving the liquid crystal panel 1110R is not set to 5 V or more, a high illuminance area, that is, a high transmittance area in the central area Rc. Do not overlap. Therefore, according to the viewing angle characteristic diagram shown in FIG. 11, the voltage at which the high illuminance region of the image display region 10a is closer to the center point C in the same procedure as the driving voltage setting method described above (in this embodiment, 5 V or more). Is set as the upper limit of the driving voltage, the luminance unevenness of the image display region 10a can be reduced for the modulated red light. In addition, by modulating the red light by the liquid crystal panel 1110R driven by such a driving voltage Vr, the luminance unevenness can be reduced as in the case of the blue light, and the manufacturing cost and parts cost of the projector can be reduced.

  In FIG. 12, for the modulated green light, the high transmittance region Rg increases from the lower left side in the figure to the upper right side in the figure as the voltage applied to the liquid crystal layer 50 is increased, similarly to the blue light and red light. It tends to shift. However, as shown in FIG. 12, the viewing angle characteristic for green light tends to slightly deviate from the viewing angle characteristic for red light. Therefore, for green light, the viewing angle characteristic diagram shown in FIG. 12 is referred to in the same procedure as the driving voltage setting method described above, and the high transmittance area of the image display area 10a, that is, the high illuminance area is the center. By setting the voltage closer to the point C as the upper limit of the drive voltage, it is possible to reduce the luminance unevenness of the image display region 10a with respect to the modulated green light, and it is possible to reduce the manufacturing and component costs of the projector.

  By the way, when the voltage applied to the liquid crystal layer 50 is set to 4V and 5V for the liquid crystal device 1 corresponding to green light, the maximum transmittance is 5V when the voltage is 4V. It becomes larger than the case of. However, from the viewpoint of viewing angle characteristics, since the central region can be covered with the high transmittance region, the case where the voltage is set to 5V is preferable to the case where the voltage is set to 4V. In this case, 4 V is set as the drive voltage of the liquid crystal device 1 corresponding to the green light.

  Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Moreover, it is included in the technical scope of the present invention.

1 is a schematic cross-sectional view of a projector according to an embodiment. It is the top view which looked at the liquid crystal panel from the counter substrate side. It is HH 'sectional drawing of FIG. It is an equivalent circuit of various elements and wirings in a plurality of pixels constituting an image display area of a liquid crystal panel. FIG. 6 is a schematic plan view of a liquid crystal panel whose clear viewing direction is indicated by an arrow. It is the viewing angle characteristic figure which showed the viewing angle characteristic of the liquid crystal panel. It is the schematic perspective view which showed the relationship between an azimuth angle and a viewing angle. It is a flowchart of a drive voltage setting method. It is a viewing angle characteristic figure obtained by simulating the viewing angle characteristic about the liquid crystal panel which modulates blue light. 10 is a graph showing the illuminance with respect to the viewing angle for each voltage applied to the liquid crystal layer along the clear viewing direction shown in FIG. 9. It is a viewing angle characteristic figure obtained by simulating the viewing angle characteristic about the liquid crystal panel which modulates red light. It is a viewing angle characteristic figure obtained by simulating the viewing angle characteristic about the liquid crystal panel which modulates green light. It is the VT characteristic figure which showed the relationship between the drive voltage of a liquid crystal panel, and the transmittance | permeability.

Explanation of symbols

  10 ... TFT array substrate, 20 ... Counter substrate, 1100 ... Projector, 1110R, 1110G, 1110B ... Liquid crystal panel, Rc ... Central region

Claims (6)

Applying a first driving voltage to the first liquid crystal layer to modulate the first color light;
A second liquid crystal device that modulates a second color light different from the first color light by applying a second drive voltage different from the first drive voltage to the second liquid crystal layer;
The first driving voltage is set based on a viewing angle characteristic of the first liquid crystal device;
The projector according to claim 1, wherein the second driving voltage is set based on a viewing angle characteristic of the second liquid crystal device. The first driving voltage is set according to a position or a width of a region where the first liquid crystal device has a high transmittance with respect to the first color light,
2. The projector according to claim 1, wherein the second driving voltage is set according to a position or a width of a region in which the second liquid crystal device has a high transmittance with respect to the second color light. The first liquid crystal device modulates one color light of red light, green light and blue light,
The projector according to claim 1, wherein the second liquid crystal device modulates two color lights of the red light, the green light, and the blue light, excluding the one color light. A third liquid crystal device for applying a third driving voltage to the third liquid crystal layer and modulating the third color light;
The projector according to any one of claims 1 to 3, wherein the third drive voltage is set based on a viewing angle characteristic of the third liquid crystal device. 5. The projector according to claim 4, wherein the third driving voltage is set according to a position or a width of a region where the third liquid crystal device has a high transmittance with respect to the third color light. The said 1st thru | or 3rd liquid crystal device modulates one color light among red light, green light, and blue light, respectively, and each modulates a mutually different color. projector.

Images