KR20030091898A - A LCD Mirror controllable its reflectivity - Google Patents

Abstract

PURPOSE: An LCD mirror capable of controlling the reflexibility is provided to improve a reaction speed, improve the reflexibility, and easily mount and change the mirror by using a portable battery as a power source. CONSTITUTION: A rear staring mirror is mountable in a vehicle and is capable of controlling the reflexibility of visible light. A photo sensor senses whether light from a rear is reflected from the rear staring mirror and makes eyes of a driver dazzled. An operation analyzer controls the light reflexibility of the rear staring mirror by using a reflective LCD using at least one or more polarizing plates(10,10'). An element controls a direction of a mirror. A power and driving function supplies electric energy.

Description

LCD mirror with adjustable reflectivity {A LCD Mirror controllable its reflectivity}

The present invention relates to a smart mirror for a vehicle. More specifically, it is possible to adjust the reflectance of the vehicle's Room Mirror or Rearview Mirror or Side Mirror to protect the driver's vision from the strong light from the rear when driving at night. It is a smart mirror technology that uses the LCD in order to.

Existing vehicle smart mirror mainly uses ECM (Electrochromic Mirror) technology, and related data are US Patent US4,902,108, US5,204,778, US5,278,693, US5,280,380, US5,282,077, US5,336,448, US5 , 448,397, US5,451,822, US6,512,624, etc., are now commercialized and installed in millions of vehicles every year. In addition, US patent US4,676,601 applies LCD to a car smart mirror, the main content of which is limited to the technology of the light sensing and the operation of the LCD. Until recently, mass production of smart mirrors for vehicles is mainly made of products using ECM, and mass production of smart mirrors using LCD is not made. Currently produced ECM room mirrors have a relatively slow response time of 3 to 6 seconds, and have a relatively small power consumption of several hundred mA, which does not use a portable primary battery and thus uses a vehicle power source. There are drawbacks not to do. LCD mirrors generally use polarizers, so the reflectance decreases due to absorption of light, which is too dark to operate.

In general, the polarization degree P (%) of the polarizing plate is defined as P = 100 x (T 1 -T 2 ) / (T 1 + T 2 ) . Here, T 1 is the transmittance when the vibration direction of incident light is parallel to the polarization axis of the polarizing plate, and T 2 is the transmittance when the vibration direction of the incident light is orthogonal to the polarization axis of the polarizing plate. In general, polarizers used in TFT (Thin Film Transistor) LCDs or STN (Super Twisted Nematic) LCDs have a polarization degree of 95% or more in the visible light band and an average light transmittance of 38 to 43%. When a transmissive TN LCD is manufactured using such a polarizing plate, the contrast ratio between bright and dark states is about 20: 1 to 1000: 1. When applied to the reflective TN LCD, the incident light passes through the polarizer, is reflected from the reflector, and then passes back through the polarizer, so it absorbs about twice as much light as the transmissive LCD, so the contrast in the dark state is necessary. It is darker than above, and the light reflectance is too dark at 25% even in bright conditions, which is not suitable for LCD mirrors. In case of using Guest-Host LCD Mode which does not use polarizer, brightness varies greatly depending on the viewing angle, and the light blocking rate is small as 50% even during operation, which is insufficient to prevent glare. It is not suitable to be applied to LCD mirror because it is not secured to UV light.

Reflective LCD is applied to a vehicle mirror to allow the reflectivity of the mirror to be arbitrarily adjusted according to the voltage applied to the LCD. The reflective LCD has an LCD panel and a portion of the LCD circuit for applying a voltage thereto to form an LCD module. The LCD panel has a liquid crystal layer formed between a glass substrate or a plastic substrate coated with two transparent electrodes, and a polarizing plate and a reflecting plate are positioned outside both substrates. The reflecting plate mainly uses a thin plastic substrate coated with a thin metal film such as aluminum or silver, and in some cases, an integrated type with a polarizing plate attached thereto or only a reflecting plate without a polarizing plate may be used. At least one polarizing plate used herein has a polarization degree of between 50% and 95%. This has the advantage of increasing the light reflectance of the mirror in the bright state and at the same time has the advantage of not being too small in the state in which the reflectance of the mirror is minimized. When the driver of the vehicle runs at night, strong light from the rear side is reflected from the mirror of the vehicle to automatically reduce the reflectance of the mirror to alleviate the glare to the driver. Conventional electrochromic mirror (ECM) room mirrors have a relatively slow response time of 3 to 6 seconds, which is insufficient to protect the driver's eyesight. In the present invention, the response speed is improved to 0.2 seconds or less using a reflective LCD mirror. In addition, at least one polarizing plate having a polarization degree between 50% and 95% is used to increase the reflectance of the LCD mirror. The technical problem to be achieved by the present invention

Firstly, in order to minimize the glare of the driver, it is to improve the response speed of the vehicle smart mirror.

Second, when the LCD is applied to a smart mirror for a vehicle, the reflectance of the mirror is increased by minimizing the decrease in reflectance of light due to the absorption of the LCD polarizer.

Third, the portable battery is used as a driving power source to facilitate the installation of the smart mirror in the vehicle.

Fig. 1 shows a cross-sectional view of the reflective LCD.

Figure 2: The main functional components of the reflective LCD mirror set are shown.

3 shows the change in reflectance with time when a driving voltage is applied to operate the reflective LCD.

1 is a cross-sectional view of a reflective LCD used as a mirror in the present invention. 10 and 10 ' are polarizing plates and have a function of absorbing light oscillating in a direction parallel to the polarization axis. In the present invention, at least one polarizing plate having a polarization degree of 50% to 95% in the visible ray band is used. Since the polarizer 10 is an outer portion of the mirror, the surface is treated with a UV cured film to prevent scratches, or a protective layer is attached to a transparent plastic substrate or a thin glass substrate having high hardness. 11 is a flat transparent glass or plastic substrate. If the plastic substrate bends well, flat and transparent glass is attached to maintain flatness or curvature. 12 is a transparent electrode layer and is generally used by coating ITO (Indium Tin Oxide) on a glass substrate or a plastic substrate at about 1500Å. In the case of driving the LCD, a potential difference is applied to the upper and lower electrode layers so that an electric field is formed in the liquid crystal layer 15 . 13 is an alignment layer for guiding the arrangement of the liquid crystal molecules of the liquid crystal layer in a predetermined direction, and is generally used by coating a polymer, PI, with a thickness of about 1000 kPa. The alignment layer 13 is formed to have a vertical alignment, a horizontal culture or an inclined alignment according to the liquid crystal molecule arrangement of the liquid crystal layer 15 . The sealant 14 serves as a barrier to allow the liquid crystal of the liquid crystal layer 15 to be limited to a certain space, and also allows the substrates located on both sides of the liquid crystal layer to adhere to each other. 16 is a reflection plate of light that actually acts as a mirror, and is formed by thinly forming a metal film such as aluminum or silver on a polarizing film 10 ' , a plastic film, or a glass substrate 17 . 15 has a thickness of several μm as the liquid crystal layer. The liquid crystal layer 15 forms a twisted nematic (TN) mode, an electrically controllable birefringence (ECB) mode, a vertically aligned (VA) mode, and the like, as necessary.

The light goes into the liquid crystal layer 15 and passes through the polarizing plate 10, and is reflected by the reflector 16 again opposed to the polarizing plate 10-side direction to the incident side polarization plate 10 in the direction. The polarization axes of the polarizing plate 10 and the polarizing plate 10 ' are 90 degrees with each other. The light passing through the polarizing plate 10 is passed through the polarization axis is 90 ° rotated, and the polarizing plate 10, passes through the are-permeation amount, some reduced back polarizing plate 10 after reflected by the reflection plate 16 'and the liquid crystal layer passes through the liquid crystal layer after the elliptically polarized While the polarization axis rotates 90 degrees again, it goes out through the polarizer 10 . If sufficient voltage is applied to the liquid crystal layer, the liquid crystal molecules are rearranged, and when the polarized light passes in this state, the polarization axis does not rotate and passes as it is. At this time is a significant amount over the light absorbing polarizing plate 10 'polarized by the polarizer 10, the reflectance of the mirror is reduced relatively.

Fig. 3 shows the change in reflectance of the mirror over time when a sufficient electric field is applied to the liquid crystal layer. Initially, when the voltage is not applied, the reflectivity of the mirror is about 48%, and after 2ms as the voltage is applied, the reflectance decreases to about 5% .If the voltage is removed at 50ms, the reflectance returns to about 48% after about 6ms. It is showing a return.

2 is a schematic diagram of a smart mirror set. Light incident on the mirror is detected by at least one semiconductor optical sensor in the incident light sensing function 21 , and separately detects light from the rear and the surrounding of the vehicle. The operation analysis function 22 analyzes the brightness of the light sensed by the optical sensor to determine whether to apply the required voltage to the mirror. In other words, if the light from the rear of the vehicle is strong enough to dazzle the driver, it is possible to apply enough voltage to the mirror to reduce the light reflectance of the mirror. When the power supply and driving function 23 determines whether voltage is applied to the LCD mirror 24 in the operation analysis function 22 , the LCD is operated by supplying the electric energy supplied from the battery power to the LCD part of the mirror. The driving voltage of the LCD required by the present invention is very low, such as 1.5Volts, it is possible to use a portable battery as a power source. Therefore, it is not necessary to connect the power of the car separately, so it is easy to manufacture and detach the smart room mirror. The portable battery may use only a primary battery such as an alkaline battery, or may use a solar cell and a (rechargeable) secondary battery in parallel.

Example 1

The room mirror sample produced and evaluated by itself is described as follows.

Glass substrate 17 : 0.7 mm thick transparent glass (Samsung Corning Precision Products) coated with ITO having a surface resistance of 80 Ω / □. The size of the LCD mirror was 160 × 85 mm.

Aligning agent 13 : After coating a PI film (trade name SE 150) about 1000 mm thick, heat curing and rubbing with a soft cloth to adjust the liquid crystal array direction. The rubbing direction of the alignment film on the side where light is incident and the alignment film on the opposite side with the reflective film is perpendicular to each other at 90 degrees.

Liquid crystal layer 15 : A high-speed response liquid crystal for 90-degree TN was used, and the thickness was adjusted by using a 5.5-micron-sized ball head spacer.

Polarizing plate 10 : The optical axis of the polarizing plate was located in parallel with the rubbing direction of the oriented film by which light injects. A polarizing plate of 75%, T 1 of 91%, T 2 of 13%, and average light transmittance of 52% was used.

Polarizing plate 10 ' : The characteristics were the same as that of polarizing plate 10 , and an integral type with reflecting plate 16 was used, and the polarizing axis was positioned in parallel with the rubbing direction of the alignment film on the opposite side where the reflecting film is located.

Two 1.5V AA alkaline batteries were used in series, and 3V was used as an LCD driving voltage as it is. The light sensor was placed in front and rear of the mirror, so that 3V was applied to the LCD only when strong light was detected by the sensor located at the rear.

As shown in FIG. 3, the reflectance of the light in the state without applying the electric field has a maximum value of 48%, and when the electric field is applied, the reflectance is lowered to 5%. The speed of conversion from the bright state to the dark state is about 2ms, whereas the conversion from the dark state to the bright state is about 6ms. The overall power consumption of the fabricated LCD mirror set is 80 kW in operation and 12 kW in standby, so using two AA batteries in a 270 x 65 mm LCD mirror set will give the battery a life expectancy of over 3 years.

First, the LCD in the present invention has a reaction speed of at least 10 times higher than that of conventional ECM room mirrors, usually within 0.2 seconds.

Secondly, since the reflectivity in the bright state of the LCD in the present invention is 48% or more, the reflectance is improved by at least 20% or more than the reflective LCD using the conventional polarizing plate.

Third, since portable batteries are used as a power source, there is no need to connect a separate wire to the vehicle, making it easy to install and replace a mirror.

Claims (11)

Reflective type liquid crystal display (LCD) mirrors with adjustable reflectivity to prevent glare from vehicle drivers: A rear gaze mirror which can be mounted on a vehicle and which can also adjust the reflectance of visible light; Light sensing means for detecting whether light coming from the rear is reflected by the rear gaze mirror to cause glare of the driver; Means for adjusting the light reflectance of the rearview mirror using a reflective LCD using at least one polarizing plate having a polarization degree of 50% to 95% in the visible ray band; Means for adjusting the direction of the mirror; Means for supplying the electrical energy required to operate the above means. The apparatus of claim 1, wherein the means for adjusting the light reflectance of the mirror adjusts the reflectance of the light by adjusting a voltage applied to the reflective LCD. The reflective LCD of claim 1 is composed of at least one polarizing plate, at least one reflecting plate, at least one liquid crystal layer, and at least two transparent electrode plates subjected to liquid crystal alignment. The reflective LCD of claim 2 has a twisted nematic (TN) mode LCD structure. The reflective LCD of claim 2 has a vertically aligned (VA) mode LCD structure. The reflective LCD of claim 2 has a guest-host LCD mode structure. The reflective LCD of claim 2 has an ECB (Electrically Controllable Birefringence) LCD Mode. The polarizing plate of Claim 3 uses at least 1 polarizing plate whose polarization degree of visible ray band is 50 to 95%. The reflecting plate of Claim 3 can use the integrated type with a polarizing plate attached. The means for supplying electrical energy in claim 1 means using electrical energy supplied from a vehicle, using a portable primary (disposable) battery, or using a solar cell and a secondary (renewable) battery. do. The polarizing plate of claim 7 has a polarization degree of 50% to 95% of the constant wavelength band of at least part of the visible light band.