KR20030069342A - Apparatus for thin film transistor liquid crystal display equipped with light sensor - Google Patents

Abstract

PURPOSE: A thin film transistor liquid crystal display having an optical sensor is provided to reduce the manufacturing cost without changing the size and thickness of a cellular phone or PDA, and transmit accurate optical information by improving transmissivity. CONSTITUTION: A sensor thin film transistor part is made up of a sensor gate electrode(22), a photosensitive layer(24), a sensor source electrode(25), and a sensor drain electrode(23) for generating optical current. A charging part is made up of a first transparent electrode(28), insulating films(27,29), and a second transparent electrode(26) for storing the optical current in electric charge type. A switch thin film transistor is made up of a light blocking layer(34), a switch gate electrode(30), a semiconductor layer(31), a switch source electrode(33), and a switch drain electrode(32) for selectively emitting electric charges of the charging part. A liquid crystal layer(39) is a guest host type liquid crystal including dichroic pigment particles.

Description

Thin Film Transistor Liquid Crystal Display with Optical Sensors {APPARATUS FOR THIN FILM TRANSISTOR LIQUID CRYSTAL DISPLAY EQUIPPED WITH LIGHT SENSOR}

The present invention relates to a thin film transistor liquid crystal display device having an optical sensor. More particularly, the present invention relates to a thin film transistor liquid crystal display device including an optical sensor capable of transmitting information of an accurate subject by improving light sensitivity.

Fingerprint authentication security technology has been the most commonly used among various body authentication fields, and the reliability is very high in terms of security. In general, piezoelectric sensors and optical sensors using semiconductors have many disadvantages compared to sensors using thin film transistors (TFTs) in terms of reliability and low cost. However, the thin film transistor sensor is excellent in price and reliability, and the manufacturing process and formation method are the same as in the prior art, and thus can be easily accessed. Therefore, it can be directly applied to STN-LCD or TFT-LCD panel which has more efficient and excellent application, and can be applied to various security technologies, and in particular, it can be used as payment system and security device of mobile phone and PDA. Utility value is expected to be very large.

1 is a cross-sectional view of a thin film transistor liquid crystal display device having an optical sensor according to the prior art.

In the thin film transistor liquid crystal display device having the optical sensor according to the prior art, the unit cell of the optical sensor layer using the TFT, as shown in Figure 1, and the sensor TFT portion which is a light sensing portion on the transparent substrate (1) The switch TFTs are arranged laterally. Under the transparent substrate 1, an illumination device (not shown) such as a backlight or an LED emits light upward. The sensor source electrode 3 of the sensor TFT portion and the switch drain electrode 12 of the switch TFT portion are electrically connected to each other through the first transparent electrode 8, and a second transparent electrode is connected to the sensor gate electrode 2 of the sensor TFT portion. 6) is connected.

Here, a photosensitive layer 4 such as amorphous silicon (a-Si: H) is formed between the sensor drain electrode 3 and the sensor source electrode 5 of the sensor TFT portion, and the predetermined photosensitive layer 4 is formed. When more than the amount of light is incident, the sensor drain electrode 3 and the sensor source electrode 5 are electrically conducted. As a result, light generated from an illumination device (not shown) under the transparent substrate 1 is reflected by the object 17 such as a fingerprint pattern and received by the photosensitive layer 4 of the sensor TFT portion, so that the sensor TFT portion is turned on. do.

On the other hand, the switch TFT portion is switched every frame set to scan the subject by a gate control signal applied to the switch gate electrode 10 so as to form the subject shape as a scanned frame for each sensor TFT portion arranged. Meanwhile, the semiconductor layer 11 connecting the switch drain electrode 12 and the source electrode 13 is covered with the light blocking layer 14 to prevent external light from being incident on the switch FTF unit.

In addition, an insulating film 7 is formed between the first transparent electrode 8 and the second transparent electrode 6, and over the protective film 9 covering the entire optical sensor layer on the first transparent electrode 8. The coating layer 15 is formed.

However, the liquid crystal display device having a light sensor according to the prior art has the following problems.

In the related art, when applied to a small application such as a mobile phone or a PDA, it is necessary to form a separate device such as a fingerprint input device in a separate space other than the screen window of the application, resulting in a large size of the product. Therefore, when a separate device such as a fingerprint input device is formed on the screen of the product in order to maintain the size of the product as it is, there is a problem that the product becomes thick, and there is also a problem that the brightness decreases due to incomplete bonding between the transparent substrates. .

In addition, the transmittance of the emitted light relative to the absorbed light is significantly reduced by the polarizing plate attached to the transparent substrate, for example, there is also a problem in that the sensitivity of the fingerprint recognition device is poor to deliver accurate subject information.

Accordingly, the present invention has been made to solve the problems of the prior art, an object of the present invention is to form a photosensitive sensor layer inside the liquid crystal panel, a dichroic dye is injected or a liquid crystal layer formed of a polymer dispersed liquid crystal The present invention provides a thin film transistor liquid crystal display device having an optical sensor that has reduced weight loss and improved transmittance.

1 is a cross-sectional view showing a thin film transistor liquid crystal display device having an optical sensor according to the prior art.

2A is a cross-sectional view of a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 1 of the present invention;

FIG. 2B is a cross-sectional view showing a guest host liquid crystal layer in the thin film transistor liquid crystal display device having an optical sensor according to Embodiment 1 of the present invention; FIG.

2C is a perspective view illustrating a polymer dispersion liquid crystal layer in a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 1 of the present invention.

3 is a cross-sectional view showing a thin film transistor liquid crystal display device having an optical sensor according to a second embodiment of the present invention.

4 is a cross-sectional view of a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 3 of the present invention.

FIG. 5 is a cross-sectional view of a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 4 of the present invention; FIG.

-Explanation of symbols for the main parts of the drawings-

21; An upper transparent substrate 22; Sensor gate electrode

23; Sensor drain electrodes 24; Photosensitive layer

25; Sensor source electrode 26; Second transparent electrode

27; Second insulating film 28; First transparent electrode

29; A first insulating film 30; Switch gate electrode

31; Semiconductor layer 32; Switch drain electrode

33; Switch source electrode 34; Light blocking layer

35; Protective film 37; Third transparent electrode

39; Liquid crystal layer 40; Array layer

42; Color filter layer 43; Bottom transparent substrate

47; Subject

A thin film transistor liquid crystal display device having an optical sensor according to the present invention for achieving the above object comprises an optical sensor including an upper transparent substrate, a lower transparent substrate, an optical sensor layer, a color filter layer, an array layer, and a liquid crystal layer. A thin film transistor liquid crystal display device, wherein the optical sensor layer comprises a sensor thin film transistor portion including a sensor gate electrode, a photosensitive layer, a sensor source electrode, and a sensor drain electrode to generate a photocurrent, a first transparent electrode, an insulating film, and a first thin film transistor. A charging unit configured to store the photocurrent in the form of charge, comprising a transparent electrode, a switch thin film transistor unit configured to selectively discharge charges of the charging unit, including a light blocking layer, a switch gate electrode, a semiconductor layer, a switch source electrode, and a switch drain electrode. The liquid crystal layer comprises dichroic dye molecules or polymer dispersed liquid crystal It characterized in that it is composed.

Hereinafter, a thin film transistor liquid crystal display device having an optical sensor according to the present invention will be described in detail with reference to the accompanying drawings.

2A is a cross-sectional view of a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 1 of the present invention, and FIG. 2B is a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 1 of the present invention. FIG. 2C is a cross-sectional view illustrating a guest host liquid crystal layer, and FIG. 2C is a perspective view illustrating a polymer dispersion liquid crystal layer in a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 1 of the present invention. 3 is a cross-sectional view of a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 2 of the present invention, and FIG. 4 is a thin film transistor liquid crystal display device having an optical sensor according to Embodiment 3 of the present invention. 5 is a cross-sectional view illustrating a thin film transistor liquid crystal display device having an optical sensor according to a fourth exemplary embodiment of the present invention.

In the thin film transistor liquid crystal display device having the optical sensor according to the first exemplary embodiment of the present invention, as shown in FIG. 2A, in addition to the array layer 40, the color filter layer 42, and the liquid crystal layer 39, a sensor thin film transistor unit is provided. And an optical sensor layer (fingerprint input layer) composed of a charging section (transmission section) and a switch thin film transistor section.

The sensor thin film transistor portion includes a sensor gate electrode 22, a photosensitive layer 24 serving as a semiconductor layer, a sensor source electrode 25, and a sensor drain electrode 23. The charging part (transmitting part) is composed of a first transparent electrode 28 as a first storage electrode, a second insulating film 26, and a second transparent electrode 26 as a second storage electrode and are generated in the sensor thin film transistor part. It serves to store current in the form of charge. The switch thin film transistor unit includes a light blocking layer 34, a switch gate electrode 30, a semiconductor layer 31, a switch source electrode 33, and a switch drain electrode 32, and charges in the charging unit according to an external control signal. It provides the role of selectively emitting.

Meanwhile, the sensor thin film transistor unit, the charging unit, and the switch thin film transistor unit are continuously arranged horizontally directly under the upper transparent substrate 21 to form an optical sensor layer, and the sensor thin film transistor unit and the switch thin film transistor unit are positive staggers ( atagger) structure. Here, the sensor thin film transistor unit is formed with a photosensitive layer 24 made of a semiconductor, and exhibits photosensitivity to reflection of light. On the other hand, since the light blocking layer 34 is formed in the switch thin film transistor portion, external light is not incident.

A passivation layer 35, a color filter layer 42, and a third transparent electrode 37 are formed below the upper transparent substrate 21, and an array layer 40 is formed on the lower transparent substrate 43. The transparent substrate 21 is opposed to each other with the liquid crystal layer 39 therebetween.

The liquid crystal layer 39 is a guest host type liquid crystal layer containing a dichroic dye molecule 39b, as shown in FIG. 2B. That is, the liquid crystal layer 39 is a homogeneous alignment guest liquid crystal or homeo that varies light transmittance between the upper substrate 21 on which the color filter layer 42 is formed and the lower substrate 43 on which the array layer 40 is formed. A tropic oriented guest liquid crystal is introduced. The guest host liquid crystal includes a dye molecule 39b exhibiting dichroism with respect to light of a specific wavelength. The liquid crystal molecule 39a and the dye molecule 39b are in a guest host relationship. In particular, the dye molecules 39b have dichroism and absorb light having a vibrating surface parallel or perpendicular to the arrangement direction. Color implementation may form a light emitting layer between the transparent electrode formed on the upper substrate 21 and the lower substrate 43 to emit light for a specific light to implement color through the color filter layer 42, or blue light emitting element when using a blue light source Color may be implemented using a light emitting layer except for the following.

Meanwhile, a liquid crystal layer 39 including a polymer dispersed liquid crystal (PDLC) in which a liquid crystal is dispersed in a polymer material in a discontinuous state in place of the guest host liquid crystal may be applied.

As shown in FIG. 2C, the polymer dispersion liquid crystal layer is polymer precursor 39c of a monomer or oligomer structure separated by phase induced by ultraviolet light curing. And a nematic liquid crystal molecule 39d. When a voltage is applied, the liquid crystal molecules 39d are arranged in a predetermined direction to transmit incident light. When no voltage is applied, the liquid crystal molecules 39d are arranged randomly so that the incident light is scattered and reflected, and thus cannot be transmitted. .

When the guest host liquid crystal layer or the polymer dispersed liquid crystal layer is applied as described above, a separate polarizing plate is not required on the outer surfaces of the upper substrate 21 and the lower substrate 43, and thus the overall transmittance of light is substantially improved.

The thin film transistor liquid crystal display device having the optical sensor configured as described above operates as follows.

The photosensitive layer 24, which is a semiconductor layer of the sensor thin film transistor unit constituting the sensor unit, receives light to generate a photocurrent, and the charging unit stores the photocurrent generated by the sensor thin film transistor unit in the form of a charge, and the switch thin film transistor unit It is connected to an external driving IC (not shown) to selectively discharge charge stored in the charging region to the outside according to a control signal. Meanwhile, the sensor source electrode 25 of the sensor thin film transistor unit is electrically connected to each other through the switch drain electrode 32 and the first transparent electrode 28 of the switch thin film transistor unit, and the sensor gate electrode of the sensor thin film transistor unit ( The second transparent electrode 26 is connected to 22.

When more than a predetermined amount of light is incident on the photosensitive layer 24 between the sensor drain electrode 23 and the sensor source electrode 25 of the sensor thin film transistor portion, the sensor drain electrode 23 and the sensor source electrode 25 become conductive. . Accordingly, light generated from an illumination device (not shown) under the lower transparent substrate 43 is reflected along the subject 47 to be received by the photosensitive layer 24 of the sensor thin film transistor part to operate the sensor thin film transistor part. Done. On the other hand, the switch thin film transistor unit is arranged for every frame set to scan the subject 47 pattern by a gate control signal applied to the switch gate electrode 30 to arrange the subject 47 pattern input to the optical sensor layer. Each of the sensor thin film transistors is formed as a scanned frame.

As shown in FIG. 3, the thin film transistor liquid crystal display including the optical sensor according to the second exemplary embodiment of the present invention, unlike the structure of FIG. 2, has a color filter layer 142 and a third filter on the lower transparent substrate 143. The transparent electrodes 137 are sequentially formed, and the passivation layer 135 and the array layer 140 are formed on the upper transparent substrate 121 that directly faces the object 147. Other than the structure and operation of the first embodiment of the present invention is the same, so the detailed description thereof will be omitted.

On the other hand, the thin film transistor liquid crystal display device having an optical sensor according to the third embodiment of the present invention, as shown in Figure 4, on the lower transparent substrate 243, the sensor thin film transistor portion and the charging portion of the reverse stagger structure ( An optical sensor layer and an array layer 240 formed of a transmissive portion) and a switch thin film transistor portion having a reverse stagger structure, and a color filter layer 242 and a third transparent electrode 237 are formed on the upper transparent substrate 221. have.

The third embodiment of the present invention has a structure in which the thin film transistor optical sensor is formed on the lower transparent substrate 243 instead of the upper transparent substrate 221. That is, the sensor thin film transistor has a structure in which the photosensitive layer 224 is formed after the sensor gate electrode 222 is formed first. Here, the photosensitive layer 224 is exposed, and light generated from an illumination device such as a backlight (not shown) positioned under the lower transparent substrate 243 emits upwards, thereby subjecting the subject 247 on the upper transparent substrate 221. The sensor thin film transistor portion is received by the photosensitive layer 224 that is reflected and exposed. In addition, the sensor source electrode 225 of the sensor thin film transistor unit and the switch drain electrode 232 of the switch thin film transistor unit are electrically connected to each other through the first transparent electrode 228, and the sensor gate electrode 222 of the sensor thin film transistor unit may be electrically connected. Two transparent electrodes 226 are connected.

On the other hand, the switch thin film transistor unit is switched every frame set to scan the subject 247 by the gate control signal applied to the switch gate electrode 230 to scan each sensor thin film transistor unit in which the pattern of the subject 247 is arranged. It is to be formed as a frame. The light blocking layer 234 is covered on the switch drain electrode 232 and the switch source electrode 233 to prevent external light from being incident on the switch thin film transistor unit.

In addition, as shown in FIG. 5, the thin film transistor liquid crystal display including the optical sensor according to the fourth exemplary embodiment of the present invention includes a sensor thin film transistor portion and a charging portion having an inverse stagger structure on the lower transparent substrate 343. An optical sensor layer including a switch thin film transistor unit having an inverted stagger structure, a color filter layer 342, and a third transparent electrode 337 are formed, and an array layer 340 is disposed on the upper transparent substrate 321 directly facing the object 347. ) Is formed. Other details are the same as the structure and operation of the third embodiment of the present invention will be omitted here.

In embodiments 1 to 4 of the present invention, the thin film transistor optical sensor layer can be driven separately or integrally with the array layer, and independently of the upper or lower transparent substrate, for example, of the unit cell of the lower transparent substrate. It can be formed in integer multiples. In addition, the thin film transistor optical sensor layer may be formed at a specific position of the liquid crystal panel, such as a rectangular portion of the liquid crystal panel, so that a fingerprint recognition system may be constructed when using a notebook or a monitor.

Various embodiments can be easily implemented as well as self-explanatory to those skilled in the art without departing from the principles and spirit of the present invention. Accordingly, the claims appended hereto are not limited to those already described above, and the following claims are intended to cover all of the novel and patented matters inherent in the invention, and are also common in the art to which the invention pertains. Includes all features that are processed evenly by the knowledgeable.

As described above, the thin film transistor liquid crystal display device having the optical sensor according to the present invention has the following effects.

In the present invention, it is possible to lower the manufacturing cost without changing the size or thickness of the product when building a payment system through the fingerprint recognition in the mobile phone or PDA, it is possible to deliver accurate optical information due to the improved transmittance. In addition, there is an effect to build a liquid crystal display device combined with a fingerprint recognition payment system that also improves the display quality of the liquid crystal display device.

Claims (9)

A thin film transistor liquid crystal display device having an optical sensor including an upper transparent substrate, a lower transparent substrate, an optical sensor layer, a color filter layer, an array layer, and a liquid crystal layer. The optical sensor layer includes a sensor thin film transistor unit including a sensor gate electrode, a photosensitive layer, a sensor source electrode, and a sensor drain electrode to generate a photocurrent, a first transparent electrode, an insulating film, and a second transparent electrode. And a switch thin film transistor portion configured to store charge in the form of charge, and a light blocking layer, a switch gate electrode, a semiconductor layer, a switch source electrode, and a switch drain electrode to selectively discharge charges of the charge portion. And said liquid crystal layer comprises dichroic dye molecules or is composed of a polymer dispersion liquid crystal. The method of claim 1, An array layer is formed on the lower transparent substrate, and a color filter layer and an optical sensor layer are formed on the upper transparent substrate. The method of claim 1, A color filter layer is formed on the lower transparent substrate, and an array layer and an optical sensor layer are formed on the upper transparent substrate. The method according to claim 2 or 3, A thin film transistor liquid crystal display device having an optical sensor, characterized in that the sensor thin film transistor portion and the switch thin film transistor portion of the optical sensor layer has a positive stagger structure. The method of claim 1, An array layer and an optical sensor layer are formed on the lower transparent substrate, and a color filter layer is formed on the upper transparent substrate. The method of claim 1, And a color filter layer and an optical sensor layer formed on the lower transparent substrate, and an array layer formed on the upper transparent substrate. The method according to claim 5 or 6, The thin film transistor liquid crystal display device having an optical sensor, characterized in that the sensor thin film transistor portion and the switch thin film transistor portion of the optical sensor layer has a reverse staggered structure. The method of claim 1, And the optical sensor layer is configured to be an integer multiple of the unit cells of the array layer. The method of claim 1, The optical sensor layer is a thin film transistor liquid crystal display device having an optical sensor, characterized in that for driving integrally or separately from the array layer.