JP2011145331A - Mirror assembly with monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mirror assembly with a liquid crystal monitor having high reliability even at a low temperature and in an electrostatic environment. <P>SOLUTION: In the mirror assembly with the liquid crystal monitor including a mirror plate where a metal thin film including a semi-translucent region is formed on a glass substrate and the liquid crystal monitor disposed on the rear surface of the semi-translucent region of the mirror plate and including a liquid crystal cell, a polarizing plate and a backlight, the semi-translucent region includes a wire grid polarizing plate where a plurality of metal wires are arranged in one direction with an equal pitch and connection parts electrically conducting respective metal wires at both ends, respectively, in extending directions of the metal wires and (a) the respective connection parts are connected to an external circuit or (b) either of the connection parts is grounded. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a mirror assembly with a monitor.

  For example, a vehicle rearview mirror or side mirror, which has a function as a normal mirror and a function for displaying text information such as video information such as vehicle periphery information and traffic congestion information as a blind spot of the driver An assembly has been devised.

  In Japanese Patent Laid-Open No. 2002-0667806, a black paint film is formed on the back surface of a mirror plate capable of transmitting light except for a light transmitting window, and the display surface of a liquid crystal display device disposed on the back surface side of the mirror plate is configured to transmit the light. In the mirror with a display function for a vehicle, which is disposed to face the window and can display the display of the liquid crystal display device through the light transmission window, the mirror plate includes a transparent glass plate and the glass plate. A mirror with a monitor for vehicles is provided, which has a metal thin film for a half mirror formed on the surface.

  Japanese Patent Laid-Open No. 2002-200936 proposes a display device in which a camera, a distance measurement sensor, and an impact sensor are provided in a vehicle, and images and information read therefrom are displayed on a side mirror, a rearview mirror, or the inside of the vehicle. In addition, an alarm device having a sound device, a display device, and a control circuit is provided in the vehicle, so that when the impact sensor detects a signal, the display device displays a danger and the sound device issues a danger warning. It describes that the driver and passengers of the vehicle can be warned of danger.

  Japanese Patent Laid-Open No. 2005-145151 discloses a display unit provided in a mirror device, a camera installed so as to capture a direction different from a region visible when the mirror device direction is viewed from a driver's seat, and a driver Proposed is a vehicle periphery confirmation assisting device having an operation switch to be operated and a processing unit for displaying an image captured by the camera on the display unit when the operation switch is operated.

JP 2002-0667806 A Japanese Patent Laid-Open No. 2002-200936 JP 2005-145151 A

  A highly reliable mirror assembly with a liquid crystal monitor is desired even in a low temperature environment or against static electricity.

According to one aspect of the present invention,
A mirror plate in which a metal thin film including a semi-transparent region is formed on a glass substrate;
A liquid crystal monitor disposed on the back surface of the semi-translucent region of the mirror plate, including a liquid crystal cell, a polarizing plate and a backlight;
Including a mirror assembly with a liquid crystal monitor,
The semi-translucent region is a connection for electrically conducting each metal wire at each of both ends in the metal wire extending direction and a wire grid polarizing plate portion in which a plurality of metal wires are arranged at an equal pitch in one direction. Including
a) each of the connecting parts is connected to an external circuit, or b) one of the connecting parts is connected to ground,
A mirror assembly with a liquid crystal monitor is provided.

  There is no reduction in visibility and reliability is high.

1A to 1C are a sectional view and a front view showing a structure of a mirror assembly with a liquid crystal monitor and a structure of a mirror plate constituting the mirror assembly with a liquid crystal monitor. 2A to 2G are diagrams illustrating a method of manufacturing a mirror plate having a wire grid region. FIG. 3A is a front view of a liquid crystal mirror assembly composed of the produced mirror plate, and FIGS. 3B and 3C are graphs showing the wavelength dependence of reflectance and transmittance in the wire grid region of the produced mirror plate. . and 4A and 4B are diagrams showing a state in which the wire grid region is connected to an external circuit, FIG. 4C is a schematic diagram showing the structure of the liquid crystal monitor, and FIGS. 4D and 4E are variations of the mirror plate having the wire grid region. It is a diagram which shows.

  Vehicle rear-view mirrors (room mirrors and side mirrors) are composed of half mirrors, and the display surface of the monitor is placed on the back side of the half mirror, and the video or text displayed by the monitor is visible from the front side of the half mirror. A mirror assembly with a monitor has been devised that can also be used as a normal rearview mirror.

  1A and 1B are a sectional view and a front view schematically showing the structure of a general mirror assembly with a liquid crystal monitor for vehicles. Surrounded by a container-shaped mirror housing 11 having a recess 11a opened on one side, a mirror plate 12 having a semi-transparent region 12a attached so as to close the opening end of the mirror housing 11, and the mirror plate 12 and the recess 11a. This is a mirror assembly with a liquid crystal monitor for vehicles provided with a liquid crystal monitor 13 in which the display surface 13a is arranged to face the semi-transparent region 12a. According to this configuration, the driver can visually recognize the rear side by the mirror plate 12 and can visually recognize various information displayed on the display surface 13a of the liquid crystal monitor 13 through the semi-transparent region 12a.

  Here, in the cross section of the mirror plate 12 near the semi-transparent region 12a, as shown in FIG. 1C, a metal thin film layer 15 for a half mirror is formed on one surface side of the glass plate 14, and A black coating film 16 is formed on the surface side excluding the light transmission window 17, and the display surface 13 a of the liquid crystal monitor 13 is arranged on the light transmission window 17. Since the display light 19a from the liquid crystal monitor 13 passes through the glass plate 14 and the metal thin film layer 15, display information on the liquid crystal monitor 13 can be visually recognized. At the same time, since the incident light 19b incident on the mirror plate 12 is reflected by the metal thin film layer 15, the rear of the vehicle can be visually recognized as reflected light 19c.

  Such a mirror assembly with a liquid crystal monitor can be assumed to have several situations that impair the display quality of the liquid crystal monitor, considering the use situation for a vehicle. For example, depending on the season and region, there is a possibility that it will be used in a low temperature environment where the temperature is minus 20 to 30 ° C. As a characteristic of liquid crystal substances, it is known that the viscosity increases and the response speed becomes slow in a low temperature environment. If the response speed of the liquid crystal substance is extremely slow, the display on the liquid crystal monitor may be blurred, which may make it difficult to view. For example, if the mirror plate surface is rubbed with a nylon cloth or the like to remove dust accumulation or temporary dew condensation due to long-term use, a charge is accumulated on the metal thin film layer 15 due to static electricity, and the liquid crystal monitor surface There is concern about erroneous display due to potential. Such deterioration in display quality due to electrification also makes it difficult to visually recognize, so there is room for improvement.

  As these countermeasures, a structure in which a heater is externally attached by a transparent electrode such as ITO, or an antistatic material is applied to the surface of the metal thin film can be considered. However, transparent electrodes such as ITO and antistatic materials are both expensive, resulting in high costs for the mirror assembly.

  The present inventors examined replacing the mirror plate of the mirror assembly with a liquid crystal monitor with a wire grid polarizer. A wire grid polarizer is a structure in which metal wires are arranged in a certain direction at equal widths and intervals, and polarized in parallel with the metal wires when the width and interval of the metal wires are shorter than the wavelength of the incident light. It has the property of shielding the components. Below, the method of producing the mirror board containing the wire grid area | region which functions as a wire grid polarizing plate by an etching method is shown.

  Refer to FIG. 2A. For example, a molybdenum (Mo) film (metal thin film layer 15) having a thickness of 1500 mm is formed on one surface side of the cleaned glass plate 14 having a thickness of 0.7 mm by sputtering. The thickness of the metal thin film layer 15 may be 300 mm or more, but if it is thin, light leakage occurs, and if it is thick, the patterning property deteriorates, so 500 mm to 2000 mm is preferable. Note that the conductive film on the glass plate 14 is not limited to Mo, and may be formed of a metal such as chromium (Cr), titanium (Ti), or aluminum (Al).

  On the metal thin film layer 15, a positive type high-resolution photoresist material is coated to a thickness of 1 μm by spin coating to form a resist film 25. Not only spin coating but also slit coating, roll coating, combined use of spin coating and slit coating, and the like may be performed. The thickness of the resist film 25 is suitably 0.8 to 1.5 μm.

Refer to FIG. 2B. Subsequently, a mask (reticle) 30 is arranged on the resist film 25 and ultraviolet exposure is performed. The exposure is performed at a fluence of, for example, 80 mJ / cm ² in accordance with the sensitivity of the resist.

  FIG. 2C is a schematic plan view showing the pattern of the mask 30. In the mask 30, a region 32a including a wire grid in which a linear pattern is formed at a constant width and a constant interval in a certain direction is formed at a predetermined position and size, and the region 32a and the peripheral region 32b are separated by a gap G. ing.

  FIG. 2D is an enlarged view of the region 32 a of the mask 30. At both ends of the linear pattern 30a extending direction, patterns 30b and 30c are formed so as to extend over the pattern 30a. The linear pattern 30a has a pitch D (interval between linear patterns) of 0.16 μm and a slit width W (width of the opening) of about 0.02 μm. The gap G has a width of about 20 μm. In order for the metal thin film corresponding to the region 32a to function as a polarizing plate in the visible light region after etching, the pitch D is preferably 0.1 to 0.5 μm, and the width W of the slit is ¼ to 1/4 of the pitch D. Between 1/10 is preferred. The gap G is preferably such that the boundary between the corresponding metal thin films in the regions 32a and 32b cannot be visually recognized after etching, and may be 100 μm or less. The mask (reticle) 30 is manufactured using, for example, an electron beam mask drawing apparatus.

  Refer to FIG. 2E. After exposure, pre-baking is performed and development is performed. An inorganic alkaline aqueous solution of KOH was used as the developer. Commercially available developers can also be used. As a commercially available developer, for example, tetramethylammonium hydroxide (TMAH) generally used for developing a positive resist for lithography can be used. A resist film 25 having the same pattern as the mask pattern of the mask 30 is patterned on the metal thin film layer 15.

  Refer to FIG. 2F. Etching of the metal thin film layer 15 is performed by dry etching. Etching was performed by reactive ion etching using SF6 as a reaction gas at a gas flow rate of 100 SCCM, a high frequency output of 200 W, and a pressure of 30 mTorr for about 3 minutes and 20 seconds.

When the metal thin film layer 15 is formed of Mo, Ti or the like, the etching gas is CF ₄ , C ₂ F ₄ , C ₂ F ₆ , C ₃ F ₆ , C ₃ F ₈ , C ₄ F ₈ , or C ₄ F. ₁₀ , C ₅ F ₈ , C ₆ F ₁₄ , CF ₃ CFOCF ₂ , C ₆ F ₅ CF ₂ CFCF ₂ , CF ₃ Br, CF ₃ I, C ₂ F ₅ I, SF ₆ , NF ₃ , WF ₆ , C ₂ F ₅ Cl, C ₂ F ₄ Cl ₂ , CF ₃ Cl, CF ₂ Cl ₂ , CFCl ₃ , CHF ₃ , CH ₂ F ₂ , CHF ₂ CF ₃ , CH ₂ FCF ₃ , CH ₃ CHF ₂ , C ₂ H _{3 F 3, C 3 HF 7} , CF 3 CH 2 CF 3, C 6 F 5 CHCH 2 or the like can be used. Also, when the metal thin film layer 15 is formed like Cr or _{Al, Cl 2, CCl 4,} SiCl 4, BCl 3, PCl 3, CBrF 3, BBr 3, C 2 ClF 5, C 2 Cl as an etching gas ₂ F ₄ , CClF ₃ , CCl ₂ F ₂ , CCl ₃ F, HCl, CH ₂ Cl ₂ , CHCl ₃ , HBr, or the like can be used.

Reference is made to FIG. 2G. The resist film 25 is removed by O ₂ ashing. Reactive ion etching was performed at a gas flow rate of 100 SCCM, a high frequency output of 300 W, and a pressure of 100 mTorr using O ₂ as a reaction gas for approximately 1 minute and 30 seconds.

  Thus, in the present embodiment, the mirror plate 22 including the wire grid region 22a having a pattern substantially congruent with the mask 30 is produced on one surface side of the glass plate 14.

  Using the produced mirror plate 22, a mirror assembly with a liquid crystal monitor is produced.

  FIG. 3A is a front view schematically showing a mirror assembly with a liquid crystal monitor composed of the produced mirror plate 22. The liquid crystal monitor 13 is disposed in a portion corresponding to the wire grid region 22a on the rear surface of the mirror plate 22. The liquid crystal monitor 13 includes a liquid crystal cell, a polarizing plate on the back side of the liquid crystal cell, and a polarizing plate formed by a wire grid region. A vertical alignment type was used for the liquid crystal monitor 13. A vertical alignment type liquid crystal monitor has a very low black level, so there is little light leakage and a relatively high reflectance. Therefore, when using a wire grid area | region as a mirror, the discomfort on visual recognition with a metal thin film area | region is reduced. The liquid crystal monitor 13 may be a horizontal alignment type.

  The inventors of the present application set the pitch of the wire grid to 0.16 μm and changed the slit width W to sample S1 (slit width W: 0.02 μm), sample S2 (slit width W: 0.06 μm), sample S3 ( A mirror plate having a slit width W of 0.08 μm was prepared, and their transmittance and reflectance were measured. The area of the wire grid region of each sample was 80 mm × 20 mm.

  FIG. 3B is a graph showing a change in reflectance with respect to the wavelength of incident light in each wire grid region of the produced mirror plate. The amount of light reflected by the total reflection mirror was set to 100%, and the reflectance in the wire grid region of the mirror plate when a vertically aligned liquid crystal monitor was disposed on the back surface of the wire grid region was measured. From this graph, it can be seen that the reflectance increases as the slit width W of the wire grid region decreases. Since the reflectance of the sample S1 is relatively high, it can be said that it is suitable as a mirror.

  FIG. 3C is a graph showing a change in transmittance with respect to the wavelength of incident light in each wire grid region of the produced mirror plate. The transmittance in the wire grid region of the mirror plate was measured when the amount of light transmitted through a glass substrate having the same thickness (0.7 mmt) as the mirror plate was 100%. From this graph, it can be seen that the transmittance decreases as the slit width W of the wire grid region decreases. Although the sample S1 has high reflectance, the transmittance is relatively low, but it can be seen that the wavelength dependency is small in the visible light region. A liquid crystal monitor was placed on the back side of the wire grid area, and when the image was actually confirmed, the wavelength dependence was small, so there was little discomfort and a relatively clear image could be confirmed.

  From the above measurement, it was found that the wire grid region of the produced mirror plate can be used as a half mirror. In particular, it was confirmed that the wire grid region under the conditions of sample S1 had a relatively high reflectance, the wavelength dependency of the transmittance was small, and the display from the liquid crystal monitor was clearly visible. When the pitch of the wire grid is 0.16 μm, the slit width is preferably 0.04 μm or less (1/4 or less of the pitch).

  The wire grid region that functions as a half mirror can also function as an electric resistance, and can also be used as a heater by applying a voltage.

FIG. 4A schematically shows the produced wire grid region. The wire grid region 22a has a structure in which a plurality of metal wires 20a are arranged on the glass plate 14 at an equal pitch. Furthermore, the metal lines 20b and 20c are electrically connected at both ends in the extending direction of the plurality of metal wires 20a. The plurality of metal wires 20a also function as resistors, and the wire grid region 22a can be used as a heater by applying a voltage between the metal lines 20b and 20c. When the resistance value of the plurality of metal wires 20 a is r, the resistance value r is (metal resistivity [Ωm] × metal wire length [m]) / cross-sectional area [m ² ] of the metal wire. Assuming that the parallel combined resistance of the plurality of metal wires 20a is R, for example, by applying a voltage V between the metal lines 20b and 20c, Joule heat of V ² / R is generated. Furthermore, as with a normal voltage source, if one of the metal lines 20b and 20c is connected to ground, the potential of the wire grid region 22a can be kept stable even when no voltage is applied. In this case, the wire grid functions as a conductor.

  FIG. 4B is a perspective view schematically showing a state in which an external circuit is connected to the wire grid region of the manufactured mirror assembly with a liquid crystal monitor. The metal lines 20b and 20c in the wire grid region 22a are electrically connected to an output terminal and a common terminal of an external circuit (for example, a DC power supply circuit), and one of the metal lines 20b and 20c is also electrically connected to the ground. ing. Since the liquid crystal monitor 13 is close to the wire grid region 22a via the glass plate 14, heat generated by voltage application to the wire grid region is efficiently conducted to the liquid crystal monitor 13 to raise the temperature of the liquid crystal substance. Therefore, it contributes to improving the response speed of the liquid crystal monitor in a low temperature environment. Further, since the wire grid region 22a is connected to the ground and the potential is stable, the fear of erroneous display due to charging of the mirror plate 22 surface will be eliminated.

  The effect of the wire grid region 22a as a heater and the effect as a protection circuit against charging were confirmed. The produced mirror assembly with a liquid crystal monitor is left in a minus 5 ° C. environment, and after confirming that the display surface 13a of the liquid crystal monitor is about minus 5 ° C., a 12V voltage is obtained via a lead drawn from the wire grid region 22a. A DC voltage was applied. It was confirmed that the display surface 13a was heated to about 10 ° C. 1 minute after the voltage was applied. This result suggests an improvement in the response speed of the liquid crystal monitor in a low temperature environment. The applied voltage may be an alternating voltage. The effect when the mirror plate 22 surface was charged was also confirmed. When the surface of the mirror plate 22 is rubbed with a nylon cloth when the wire grid region 22a is not connected to the ground, the erroneous display is not eliminated for about 1 minute, whereas no erroneous display occurs when the ground is connected to the ground. I was able to confirm that. From the above, it is suggested that the deterioration of display quality due to the low temperature environment and static electricity, which was the initial problem, can be improved without adding a countermeasure member by configuring the half mirror with a wire grid polarizer.

  Furthermore, since the wire grid region functions as a polarizing plate, it can be used as an alternative to the resin film polarizing plate disposed on the display surface of the liquid crystal monitor. As shown in FIG. 4C, the liquid crystal monitor 13 is generally provided with resin film polarizing plates 40a and 40b formed by forming a resin in which iodine or dye is dispersed into a film and stretching it in a uniaxial direction outside the liquid crystal cell 41. The backlight 42 is arranged on the opposite surface of the display surface 13a. Since the wire grid region 22a functions as a polarizing plate, it can also be used as an alternative to the resin film polarizing plate 40a. This reduces the number of components of the liquid crystal monitor 13 and contributes to cost reduction of the entire mirror assembly.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these.

  For example, in the manufacturing method of the mirror plate according to the embodiment, the case where a mask (reticle) is used has been described, but a technique (nanoimprint technique) for transferring a pattern using a high-precision stamper may be used. In either case, once a master pattern is created, it can be used repeatedly.

  Furthermore, the position and shape of the wire grid region in the metal thin film layer can be changed depending on the shape of the liquid crystal monitor to be arranged, information to be displayed, and the application. For example, a wire grid region may be formed on the entire mirror plate. As shown in FIG. 4D, the transmission axis of the mirror plate 22 serving as a wire grid polarizing plate is preferably set in parallel with the horizontal plane 43. Usually, the reflected light from the water surface or the like contains more horizontal polarized light. If the transmission axis of the mirror plate 22 is set so as to follow the horizontal polarization, the horizontal polarization component of the incident light 19b is transmitted, so the horizontal polarization component of the reflected light 19c is reduced. That is, the mirror plate 22 shown in FIG. 4D can be used as a mirror with an antiglare function. Further, as shown in the cross-sectional view of the mirror assembly with a liquid crystal monitor shown in FIG. 4E, a translucent surface protective layer 45 is disposed in the wire grid region 22a formed on the glass plate 14, and the surface protective layer 45 is sandwiched therebetween. The liquid crystal monitor 13 may be arranged.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

DESCRIPTION OF SYMBOLS 12 Mirror board 13 Liquid crystal monitor 14 Glass board 15 Metal thin film layer 16 Black coating film 19 Image light 22 Mirror board with a wire grid polarizing plate 25 Resist film 29 External circuit 30 Mask

Claims (5)

A mirror plate in which a metal thin film including a semi-transparent region is formed on a glass substrate;
A liquid crystal monitor disposed on the back surface of the semi-translucent region of the mirror plate, including a liquid crystal cell, a polarizing plate and a backlight;
Including a mirror assembly with a liquid crystal monitor,
The semi-translucent region is a connection for electrically conducting each metal wire at each of both ends in the metal wire extending direction and a wire grid polarizing plate portion in which a plurality of metal wires are arranged at an equal pitch in one direction. Including
a) each of the connecting parts is connected to an external circuit, or b) one of the connecting parts is connected to ground,
A mirror assembly with a liquid crystal monitor.   2. The mirror with a liquid crystal monitor according to claim 1, wherein the polarizing plate and the wire grid polarizing plate portion of the semi-translucent region constitute a crossed Nicol polarizing plate, and the liquid crystal cell is a vertical alignment liquid crystal cell. Assembly.   3. The mirror assembly with a liquid crystal monitor according to claim 1, wherein the pitch of the metal wires is 0.5 [mu] m or less, and the interval is 1/4 or less of the pitch of the metal wires.   4. The mirror assembly with a liquid crystal monitor according to claim 1, wherein the metal thin film has a thickness of 500 to 2000 mm.   5. The mirror assembly with a liquid crystal monitor according to claim 1, wherein the metal thin film is made of molybdenum, chromium, aluminum, or titanium.

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