KR20040072422A - front filter of Plasma Display Panel - Google Patents

Abstract

PURPOSE: A front filter for a plasma display panel is provided to improve a light/darkness contrast ratio and a brightness of PDP panel in result of having a photo shutter function. CONSTITUTION: A front filter for a plasma display panel comprises an adhesive(20) added with a dye on a tempered glass(10), a photo shutter(60) deposited successively with an ITO(64)/Electrical Optical(EO)(62)/ITO on the adhesive, an EMI shielding layer formed with a mesh(30) or an Ag/ITO(30') on the photo shutter, an anti-reflection(AR) coating film(50) formed at a both side of a most outside, two electrode surfaces formed between the PDP panel and the EMI shielding layer and applying an electric field, and a material layer formed between the two electrode surfaces and changing a photo property by an electric field applied at the electrode.

Description

Front filter of plasma display panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel. More particularly, the present invention relates to a front surface filter that can improve light characteristics by adding a property to transmit or block light according to an electric field applied from the outside.

Plasma Display Panels (PDPs) driven at high voltages of 100V require front filters having various functions on the front side of the panel to realize high quality video.

The function of the front filter is to firstly protect the panel from external shocks, secondly, to block electromagnetic waves emitted from the panel due to high-voltage driving, and thirdly, to block near-infrared rays to prevent the remote control from malfunctioning. Optical characteristics such as;

PDP front filters currently on the market have a structure that attaches layers to perform the functions of the aforementioned filters on both sides of tempered glass, and the front filter has a metal mesh type and Ag / ITO depending on the type of electromagnetic shielding material used. Are divided into types.

Figure 1a, 1b is a view showing the structure of the PDP front filter according to the prior art, Figure 1a is a view showing a metal mesh type front filter, Figure 1b is a view showing an Ag / ITO front filter.

As shown in FIG. 1B, the Ag / ITO multilayer thin film 30 ′ has not only an electromagnetic wave blocking function but also a near infrared ray blocking function. As shown in FIG. 1A, when the metal mesh 30 is used, There is a need for a layer that acts as a near infrared shield.

In addition, a dye film 20 that absorbs a specific wavelength is formed between the tempered glass 10 and the metal mesh 30 or Ag / ITO 30 '. That is, color purity improvement and color temperature correction are performed using a specially designed dye combination to improve optical characteristics.

Finally, an anti-reflection coating film 50 is attached or deposited on both upper layers.

Due to the complex structure of the front filter and the dye that absorbs light of a specific wavelength to improve the optical properties, most of the filters have a light transmittance of 40 to 55% despite the improvement of the optical properties.

The low light transmittance of these filters causes the PDP brightness to drop, causing a decrease in luminous efficiency. However, if the transmittance of the filter is increased, the contrast contrast of the bright room is lowered due to the strong external light scattering of the PDP itself, making it difficult to realize high quality video.

The front filter for a plasma display panel according to the related art described above has the following problems.

Increasing the transmittance of the filter increases the brightness of the PDP but decreases the contrast contrast ratio, while decreasing the transmittance increases the brightness contrast ratio but decreases the luminance. As described above, the conventional front filter has a disadvantage in that the brightness and contrast ratio cannot be improved at the same time.

Accordingly, the present invention has been made to solve the above problems, and an object thereof is to provide an operation concept of a new front filter which improves PDP brightness and does not lower the contrast contrast ratio.

Another object of the present invention is to propose a material or systems that can be used in a new front filter and to reveal its requirements.

Another object of the present invention is to provide a manufacturing process of the front filter of a new concept.

1A and 1B illustrate the structure of a PDP front filter according to the related art.

2A and 2B are schematic views of a plasma display driving scheme according to the prior art;

3 is a view showing the structure of a front filter for a plasma display panel according to the present invention;

Figure 4 (a) (b) is a schematic diagram of a plasma display driving and optical shutter operation method according to the present invention

* Explanation of symbols for main parts of the drawings

10 tempered glass 20 pigmented additives

30: metal mesh 30 ': Ag / ITO

40: adhesive 50: antireflective coating film (AR)

60: optical shutter 62: EO material layer

64: ITO

Features of the front filter for a plasma display panel according to the present invention for achieving the above object is an adhesive with a pigment added on the tempered glass, an optical shutter sequentially deposited on the adhesive by ITO / EO / ITO, In the front filter for a plasma display (PDP) panel consisting of an EMI shielding layer formed of a mesh or Ag / ITO on the optical shutter, and an antireflective coating film (AR) formed on the outermost both sides, the PDP panel and EMI shielding It includes two electrode surfaces formed between the layers to apply an electric field, and a material layer formed between the two electrode surfaces and whose optical properties are changed by an electric field applied to the electrodes.

In this case, the material layer is hundreds Up to 1 degree It is preferable to have a reaction rate of.

The change in optical characteristics by the electric field is preferably changed to a state in which light is transmitted and a state in which light is blocked.

The material layer is a material that undergoes phase transition by electric field or heat such as Ferroelectric Liquid Crystal (FLC), Polymer-Stabilized (PS) FLC, Polymer Dispersed (PD) FLC, Liquid Crystal (LC), PD-LC, PS-LC, etc. It is preferably composed of at least one of.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

A preferred embodiment of the front filter for a plasma display panel according to the present invention will be described with reference to the accompanying drawings.

3 is a view showing the structure of a front filter for a plasma display panel according to the present invention.

As shown in FIG. 3, the optical shutter 20 sequentially deposited with pigments on the tempered glass 10 and ITO 64 / EO 62 / ITO 64 on the adhesive 20. 60, an EMI shielding layer 30 (30 ') formed of a mesh or Ag / ITO on the optical shutter 60, and an antireflective coating (AR) 50 on both outermost surfaces.

At this time, the electrical optical (EO) material 62 is hundreds Up to 1 degree It has a reaction rate of.

The driving principle of the video of the plasma display panel configured as described above is as follows.

In one second, a signal of 60 still images is input to the PDP. In other words, one frame still image is implemented on the panel for a time of 1/60 = 16.6 ms (milli-second).

At this time, the present invention can be easily applied to the ADS (Address Display Separated) method in which the time between the syringes and the desired screen is displayed among the PDP driving methods.

The ADS method also has various configuration methods of subfields (SF) forming one frame according to the gradation representation method, and the present invention will be described based on the most popular Fujistu method.

In the Fujistu method, as shown in FIG. 2, one frame is composed of eight subfields (SFs), each of which has a reset period for removing an electric charge generated in the PDP cell from the previous SF to an initial state and an input. It consists of an address cycle for generating charges in each cell in accordance with the signal, and a sustain cycle for emitting light by applying a high voltage driving signal to all cells at the same time.

On the other hand, the time of each cycle of each SF is defined as a time of 300 ~ 400 sec for the reset period, 600 seconds for the address period.

In this case, the reset period and the address period each take the same time, whereas in the case of the sustain period, according to the bit order of each SF Has a time ratio of.

During the address period, the charge is charged to the cell with the input signal 1 (or on), and the cell with 0 (or off) is not charged.

Accordingly, due to the nonlinear nature of the plasma, the voltage value for discharging is lower in the charged cell. Therefore, when the sustain signal is input to all the cells at a voltage slightly higher than this threshold voltage, the discharged cell is discharged. This happens and the light is emitted, but the cells that do not emit light.

In this way, by selecting SFs having different emission times in one frame, 256 gray levels of each cell can be represented.

One of the optical characteristics of the PDP panel is the contrast ratio.

This means the ratio of the brightness when a signal of 0 is input and the brightness when a signal of 255 is input.

According to the actual measurement conditions, the contrast ratio is the contrast contrast ratio and darkroom contrast ratio.

Dark-room contrast ratio is measured under the condition that the external lighting is completely blocked. When inputting a signal of 0, some light is emitted due to the driving characteristics of the PDP panel, thereby limiting the contrast ratio.

That is, unwanted light is emitted in the process of eliminating the charge charged in the reset and address periods.

Contrast contrast is measured under bright light, similar to the conditions of watching TV in real life. In this case, the light of the illumination is reflected by the panel to increase the brightness of the arm.

Attaching a conventional front filter to a PDP panel allows the external light to pass through the filter twice when reflected by the panel. Therefore, if the filter transmittance is 50%, the effect of external light is 1/4 compared to the case without the filter. Is reduced to (1/2 x 1/2).

On the other hand, the amount of light on the panel is reduced by 1/2, so the contrast ratio That's about twice the panel.

Dark contrast contrast ratios, on the other hand, remain unchanged because both light and dark stem at the same rate.

In the present invention, the optical shutter layer 60 whose optical properties are changed by an external electric field is added to the existing front filter.

In the optical shutter layer 60, indium tin oxide (ITO) 64, which is a transparent electrode material for applying an electric field to the EO material 62, is inserted up and down.

The EO material 62 may be directly deposited according to a state, and the EO material 62 may be inserted between transparent substrates such as PET on which the ITO 64 is deposited.

The location of the optical shutter layer 60 may be located above or below the tempered glass and is necessarily located between the PDP panel and the EMI blocking layer (mesh or Ag / ITO) 30, 30 '.

In some cases, the EMI blocking layers 30, 30 'may be one electrode of the EO material 62 (opposite the panel).

The characteristic required for the EO material 62 is that a change in transmittance occurs depending on the electric field. That is, if an electric field is applied, the transmittance is maximum. If the electric field is 0, the transmittance is minimum. On the contrary, when the electric field is applied, the transmittance is minimum. If the electric field is 0, the transmittance is maximum.

In some cases, the transmittance may be maximum when the electric field is a positive sign and may be minimum when a negative sign is used, or may be minimized when a positive sign is used and maximum when a negative sign is used.

Another characteristic required for the EO material 62 is that the light absorption of the EO material itself should be small when the transmittance is maximum, and the absorption rate should be large when the transmittance is minimum. And in both states, the reflection of scattered light should be minimal.

In general, the response of a material to light consists of reflection, transmission, and absorption, which add up to 1 (or 100%).

4 (a) and (b) are schematic diagrams of a plasma display driving and optical shutter operation method according to the present invention, and FIG. 4 (a) shows an applied voltage according to a driving signal, and FIG. 4 (b) shows an optical shutter. Is a diagram showing a change in transmittance of?.

Referring to FIG. 4 (a) (b), a description will be given based on an EO material having optical characteristics in which a transmittance is maximized when an electric field, which is a specific operating principle, is applied, and when the electric field is 0, the transmittance is minimum.

The waveform of the voltage applied for driving the optical shutter is related to the PDP driving process.

That is, as shown in FIG. 4A and FIG. 4B, the optical shutter 60 is made transmissive by applying a voltage during the sustain period in which screen information is displayed on the PDP, and the voltage is set to zero during the reset period and the address period. Thus, the transmittance of the optical shutter 60 is minimized.

This minimizes the emission of unwanted light generated during the reset / address period, thereby lowering the black brightness in the dark room, thereby improving the dark room contrast without deteriorating the white brightness.

In addition, even in the bright room, the transmittance is small during the reset / address period, and the contribution of absorption is greater than the reflection itself, thereby lowering the external light reflection, thereby lowering the brightness of black in the bright room.

In order for the front filter having the optical shutter function to operate properly, the response time of the optical shutter 60 becomes an important factor.

In other words, the reset / address time is approximately 0.9 msec, depending on the PDP driving method or panel size. In some cases, the address can be set without reset.

When the optical shutter is defined as a time difference of 10% to 90% as shown in FIG. 4, the optical shutter function can be optimized when the response time of the optical shutter is less than 0.1 to 0.2 msec. In addition, the benefit of improved contrast is obtained.

In addition, the EO material 62 may be phase-transferred by an electric field or heat, such as Ferroelectric Liquid Crystal (FLC), Polymer-Stabilized (PS) FLC, Polymer Dispersed (PD) FLC, Liquid Crystal (LC), PD-LC, PS-LC, etc. Chalcogenide, etc. may be used.

In the case of FLC / LC, one or two polarizers may be used, a cholesteric liquid crystal may be used in addition to nematic, and a dye may be added to absorb light.

In conclusion, it is possible to apply the front filter using the optical shutter 60 to the PDP clearly that the time when the desired image is actually displayed and the time when the data is written to the panel are clearly distinguished. Because it is only about 3, the rest of the time is to block both the light from the panel and the light incident to the panel by the external light source to improve the dark and grayscale at the same time.

As described above, the front filter for plasma display panel according to the present invention includes an optical shutter function in which optical characteristics are changed by an electric field, thereby significantly improving the brightness and contrast of a room / dark contrast ratio of a PDP panel. .

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (4)

An adhesive added with pigment on tempered glass, an optical shutter sequentially deposited on the adhesive in ITO / EO / ITO, an EMI blocking layer formed of mesh or Ag / ITO on the optical shutter, and the outermost In the front filter for a plasma display (PDP) panel composed of an antireflective coating film (AR) formed on both sides, Two electrode surfaces formed between the PDP panel and the EMI blocking layer to apply an electric field; And a material layer formed between the two electrode surfaces, the material layer of which optical properties are changed by an electric field applied to the electrode. The method of claim 1, The material layer is hundreds Up to 1 degree Front filter for plasma display panel, characterized in that having a reaction rate of. The method of claim 1, The optical characteristic of the plasma display panel is changed in a state in which light is transmitted and the light is blocked. The method of claim 1, The material layer is a phase change material by electric field or heat such as Ferroelectric Liquid Crystal (FLC), Polymer-Stabilized (PS) FLC, Polymer Dispersed (PD) FLC, Liquid Crystal (LC), PD-LC, PS-LC, etc. (Chalcogenide A front filter for a plasma display panel, characterized in that composed of at least one.