KR100378043B1 - Multilayer antistatic/antireflective coating for display device - Google Patents

Abstract

On the outer surface of the faceplate of a display device such as a cathode ray tube (CRT) type, a first inner antireflective layer of Sb-SnO ₂ (particle diameter between 5-20 nm) is applied in a thickness in the range of 200-600 nm. . The SB-SnO ₂ layer has a high light refractive index (n ₁ = 1.8) and also provides antireflection function. The faceplate is preheated to a temperature in the range of 35-50 ° C., followed by a second intermediate antireflective layer of alternating TiO ₂ (particle refractive index n ₂ = 2.0 and a particle diameter between 5-50 nm). It is applied to the surface with a thickness of 100-200 nm. A third outer antireflective layer is then applied in the form of silica gel at a temperature in the range of 35-45 ° C. with a thickness in the range of 100-200 nm and an optical refractive index n ₃ , at its intermediate layer surface. The second and third antireflective layers follow a quarter wavelength rule, just N ₃ = √n ₂ ,. The multilayer antireflective coating may also be employed as a five layer coating in which the TiO ₂ and silica gel layers are repeated in the outward treatment from the glass substrate to provide broadband antireflection capability.

Description

Multilayer antistatic / antireflective coating for display devices {MULTILAYER ANTISTATIC / ANTIREFLECTIVE COATING FOR DISPLAY DEVICE}

FIELD OF THE INVENTION The present invention relates generally to video display devices and, in particular, to multi-layer coatings on the outer surface of the faceplate of a video display device, which can be applied by conventional methods such as liquid spin coating and with a wide range of antireflection capabilities. It is about.

Display devices, such as cathode ray tubes (CRT) or flat panel, provide a video image for viewing. The display plate is generally made of glass, and its outer surface contains one or more antistatic and antireflective coatings to reduce light reflection which degrades the quality of the video image. With the growing emphasis on spectator ergonomics, providing this type of display device with anti-reflective properties has become of great importance for the general adoption and business achievement of display devices. Multilayer coatings are applied by either chemical vapor deposition (CVD) or physical vapor deposition (PVD), because of the different layers employed. The complexity and high cost of applying a multilayer coating by either of these methods makes it impossible to obtain commercial adoption of this type of coating, which is widespread.

Another method of display plate coating employs a single layer, in which the antireflective and antistatic components are mixed together to form a single solution applied as a layer of coating. Another method applies an inner antistatic layer first and then an outer antireflective layer to form a two layer coating. The single layer and two layer methods employ the liquid spin method as a standard, and the method is widely used in the display device industry. However, the single layer method or the two layer method is characterized by providing antireflection capability only over a limited bandwidth.

The present invention thus provides a multilayer antireflective coating for a glass display plate of a video display device with a margin of broadband antireflection capability, in which each layer can be applied using conventional liquid spin techniques. It is aimed to overcome the limitations of the prior art mentioned in.

The present invention contemplates a multilayer coating applied to the outer surface of a video image display plate by spin coating, the coating comprising; An inner layer of a first conductive ground having an optical index of refraction n ₁ disposed on an outer surface of the display panel; A second antireflective layer, disposed on the first inner layer, having a refractive index n ₂ , where n ₂ > n ₁ ; And a refractive index n ₃ , disposed on the second antireflective layer, only And a third antireflective layer.

Hereinafter, preferred embodiments of the present invention will be described in detail.

Referring to FIG. 1, a longitudinal sectional view of a color CRT 10 incorporating a multilayer antistatic / antireflective coating in accordance with the principles of the present invention is shown. The CRT 10 includes a sealed glass envelope 12 having a front faceplate or display 14, a rear neck portion 18, and a funnel portion 16 in the middle thereof. have. On the inner surface of the glass faceplate 14 is arranged a phosphor screen 24 containing a plurality of individual phosphor deposits or components, which emits light when the electron beam is projected on it to produce a video image on the faceplate. do. The color CRT 10 includes three electron beams 22 focused towards the glass faceplate 14 of the CRT. In the neck portion 18 of the glass envelope 12 of the CRT, a plurality of electron guns 20 are arranged on the phosphor screen 24 arranged in a row in which the electron beams 22 are directed. The electron beams 22 are deflected vertically and horizontally across the phosphor screen 24 by a magnetic deflection yoke, for simplicity, not shown. A shadow mask 26 having a plurality of offset electron beams passing through the holes 26a and the skirt portion 28 around its periphery is disposed away from the phosphor screen 24. The shadow mask skirt portion 28 is firmly attached to the shadow mask mounting fixture 30 around the shadow mask. The shadow mask mounting fixture 30 is attached to the inner surface of the glass enclosure 12 of the CRT and may, for simplicity, include conventional attachments and arrangements such as masking frames and mounting springs not shown in the figures. . The shadow mask mounting fixture 30 may be attached to the inner surface of the glass envelope 12 of the CRT and the shadow mask 26 may be attached to the mounting fixture by conventional means such as a weld or frit of the glass foundation. good.

2 shows a cross-sectional view of a multilayer antistatic / antireflective coating 44 disposed in accordance with the present invention on the outer surface of flat display plate 40. The flat display plate 40 is made of glass and has a phosphor layer 42 on its inner surface to emit light of three primary colors of red, green and blue in response to the projection electron beam. The antistatic / antireflective coating 44 includes a first inner antistatic layer 44a, a second intermediate antireflective layer 44b, a third intermediate antireflective layer 44c, a fourth intermediate An antireflective layer 44d, and a fifth outer antireflective layer 44e. 3 is a simplified flowchart illustrating the steps involved in applying the antistatic / antireflective coating 44 of the present invention to a glass display plate in accordance with the principles of the present invention.

In step 80, the glass display plate 40 is preheated to a temperature in the range of 35 ° -50 ° C. The inner antistatic layer 44a is applied directly to the outer surface of the glass display plate in the next step 82. The first inner antistatic layer 44a preferably consists of antimony liquid treatment tin oxide (Sb-SnO ₂ ) having a particle diameter between 5-20 nm and a thickness in the range of 200-600 nm. The first inner antistatic layer 44a is coupled to neutral ground by a conductor 48. The first inner antistatic layer 44a not only provides an antistatic function, but also serves as a high light reflectance component for the outer antireflective layers when it has an optical refractive index of 1.8. Following the placement of the first inner antistatic layer 44a, the display plate 40 is dried prior to applying the next layer of the antistatic / antireflective coating 44.

The clad glass display plate 40 is then heated to a temperature in the range of 35 ° -45 ° C. in step 84 and a second intermediate to the surface of the first inner antistatic layer 44a in step 86. Of antireflection layer 44b is applied. The second intermediate antireflective layer 44b preferably consists of titanium oxide (TiO ₂ ), with an optical index of refraction n ₂ , but n ₂ = 2.0 and is applied at a thickness of 100-200 nm. The TiO ₂ layer is in the form of a colloid and preferably consists of particles in the range of 5-50 nm in diameter.

After applying the second intermediate antireflective layer 44b in step 86, the glass panel 40 is then dried. The temperature of the glass panel 40 is then heated in step 88 to a temperature in the range of 35 ° -45 ° C., with a third intermediate antireflective layer 44c preferably made of silica gel in step 90 It is applied to the surface of the second intermediate antireflective layer 44b of TiO ₂ . The third intermediate antireflective layer 44c is light refractive index n ₃ , And thus follows a quarter wavelength rule proportional to the second intermediate antireflective layer 44b. The third intermediate antireflective layer 44c preferably has a thickness in the range of 100-200 nm. After applying the third intermediate antireflective layer 44c, the glass display plate 40 is baked in a next step 92 for 10-20 minutes at a temperature in the range of 110-180 ° C.

According to another embodiment of the present invention, a fourth antireflection layer 44d made of TiO ₂ may be applied to the surface of the third intermediate antireflective layer 44c in step 94. The clad glass display plate 40 is heated to a temperature in the range of 35 ° -45 ° C in the next step 96. Subsequently, the following is applied to the fourth intermediate antireflective layer 44d surface, and application of the fifth outermost antireflective layer 44e, preferably made of silica gel, is followed in step 98. Following application of the fifth outer antireflective layer 44e to the glass display plate 40 is followed by firing of the display plate at a temperature in the range of 110 ° -180 ° C. for 10-30 minutes in step 100. To be followed.

Referring to FIG. 4, a simple antistatic / antireflective coating application device 50, which applies a multilayer antistatic / antireflective coating 54 to the glass display plate 52a of the CRT 52 by spin coating, is simply described. It is shown in schematic form. The coating application device 50 comprises a plurality of support blocks, both of which are shown in the figures as components 56 and 58, which engage and support the CRT 52. An arranging device 62 including a spray nozzle 66 and a support arm 64 is disposed above the CRT. The dispensing device manages various materials that form several antistatic and antireflective layers in the form of fine mist on the glass display screen 52a of the CRT. Sprayer 62 is capable of raising or lowering in the direction of arrow 70 to apply layers of uniform thickness, while coating application device 50 moves CRT 52 at a speed of 150-250 rpm. It is adapted to rotate in the direction of (68). For the antistatic / antireflective coating of each layer, typically 20 ml is applied to the display 52a of the CRT.

Referring to FIG. 5, there is shown a comparison chart of the reflectivity of a multilayer antistatic / antireflective coating according to the present invention compared to the two prior art antireflective coatings. The reflectivity of the multilayer coating of the present invention is labeled "invention" and shows a decrease in light reflectance for wavelengths above 500 nm. The curve labeled "prior art # 1" is a graph of the reflectance of two layers of antistatic / anti-reflective coating available from Asahi Glass Co., and the curve labeled "prior art # 2" is antistatic / reflective available from Sumitomo Glass Co. It is a graph of the light reflectance of the anti-coat coating. These curves show that the multilayer antistatic / antireflective coating of the present invention provides reduced light reflection from the outer surface of the display panel over almost visible spectrum.

1 is a longitudinal cross-sectional view of a CRT incorporating a multilayer antistatic / antireflective coating in accordance with the principles of the present invention;

2 is a partial cross-sectional view of a flat display plate having a multilayer antistatic / antireflective coating on its outer surface in accordance with the present invention;

3 is a simple flowchart illustrating the sequence of steps of applying a multilayer antistatic / antireflective coating to the outer surface of a radio display panel in accordance with the principles of the present invention:

4 is a simplified schematic diagram illustrating a method for providing a multilayer antistatic / antireflective coating in accordance with the principles of the present invention on an outer surface of a video display plate: and

5 is a comparison chart of the reflectivity of the multilayer coating of the present invention with two commercially available antireflective coatings.

* Explanation of symbols for main parts of the drawings

40: flat display plate 42: phosphor layer

44: multilayer antistatic / antireflective coating 44a: inner layer antistatic layer

44b, c, d: middle antireflective layer 44e: outer layer antireflective layer

48: conductor 50: coating application device

52: CRT 52a: glass display plate

54: antistatic / reflective coating 56,58: support block components

62 sprayer 64 support arm

66: spray nozzle

Claims (12)

A multilayer coating applied to the outer surface of a video display plate by spin coating, An inner layer of the first conductive ground disposed on an outer surface of the display panel and having a refractive index n ₁ ; A second antireflective layer disposed on the surface of the first inner layer and having an optical index of refraction n ₂ , where n ₂ > n ₁ ; And Disposed on the surface of the second antireflective layer such that light reflectivity n ₃ , where n ₃ = A third antireflective layer, Consisting of a coating. The method of claim 1, Wherein said first inner layer is comprised of antimony liquid treatment tin oxide (Sb-SnO ₂ ) and said second antireflective layer is comprised of titanium oxide (TiO ₂ ). The method of claim 2, The third layer is made of silica gel. The method of claim 1, And further comprising a fourth antireflective layer disposed on the third antireflective layer surface and a fifth antireflective layer disposed on the fourth antireflective layer surface, wherein the fourth and fifth antireflective layers A coating having the same configuration and light refractive indices as this second and third antireflective layer, respectively. The method of claim 4, wherein The first inner layer is tin oxide (Sb-SnO ₂ ) of antimony liquid treatment, the second and fourth antireflective layers are titanium oxide (TiO ₂ ), and the third and fifth antireflective layers This is a silica gel coating. The method of claim 3, wherein Wherein said tin oxide layer of said antimony liquid treatment is 200-600 nm thick and consists of particles having a diameter of 5-20 nm. The method of claim 3, wherein Said titanium oxide layer being 100-200 nm thick and consisting of particles having a diameter of 5-50 nm. The method of claim 3, wherein The silica gel layer is 100-200 nm thick. By applying a multilayer coating to the outer surface of the video display plate by spin coating, Disposing an antistatic layer of a first conductive ground having an optical index of refraction n ₁ on an outer surface of the video display panel; Disposing a second antireflective layer on the surface of the first antistatic layer, wherein a _second refractive index n ₂ , where n ₂ > n ₁ , is present; And On the surface of the second antireflective layer, light index n ₃ , Arranging a third antireflective layer, The method consists of the steps. The method of claim 9, The first inner layer is tin oxide (Sb-SnO ₂ ) for antimony liquid treatment, and the step of disposing the first inner layer may include tin oxide in antimony liquid treatment in the range of 5-20 nm. And arranging at a thickness in the range of 200-600 nm of the particle diameter. The method of claim 9, Wherein said second antireflective layer is titanium oxide, said titanium oxide being disposed at a thickness in the range of 100-200 nm and consisting of particles having a diameter of 5-50 nm. The method of claim 9, And the third antireflective layer is made of silica gel and the silica gel is disposed at a thickness in the range of 100-200 nm.