KR19980041099A - Color STN liquid crystal display with color filter removed - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color STN LCD from which a color filter has been removed, and is a method of changing a cell gap (d) and refractive index abnormality (Δn) at portions corresponding to R, G, and B pixels without using a color filter. Color is realized by changing d by forming a film having a uniform spectral characteristic or by forming a laminated film having uniform spectral characteristics, or by changing a Δn by stacking a material having refractive index anisotropy, so that the pixel colors of R, G, and B are not changed. As a result, color purity is improved, and a separate retardation plate is unnecessary, thereby reducing manufacturing cost, and preventing occurrence of defects due to the formation of a color filter, thereby improving process yield.

Description

Color STN liquid crystal display with color filter removed

The present invention relates to a color STN liquid crystal display (Super Twisted Nematic Liquid Crystal Display) (hereinafter referred to as STN LCD) in which a color filter has been removed. By using the relationship between the transmission wavelength (λ = d · Δn) of the LCD in relation to the cell gap d, the cell gap of each pixel corresponding to the RGB is changed to realize the RGB wavelength, thereby improving color purity, and color filter. The present invention relates to a color LCD which can reduce manufacturing cost by not using and reduce defects due to color filter formation.

LCD, a type of flat panel display, is an apparatus that obtains an image with a difference in contrast obtained by changing an optical anisotropy by applying an electric field to a liquid crystal having both liquidity and optical properties of a crystal. Twisted Nematic (TN), Super TN (STN), Ferroelectric LCD (FLCD), and TFT LCD are used.

Such LCDs have lower power consumption, easier thin and shorter sizes, and can be colored, larger, and more refined than conventional cathode ray tubes.

In general, LCDs are formed in a form in which transparent electrode patterns, which are opposite electrodes, are formed on transparent upper and lower substrates, the upper and lower substrates are sealed to have a predetermined interval, and a liquid crystal is sealed in a cell gap therebetween.

The LCD operates with only two colors, a background color when driving the liquid crystal and a pixel color when driving the liquid crystal. In order to colorize the LCD, a color filter must be formed on one substrate.

1 is a cross-sectional view of a color LCD according to the prior art, which is an example of an STN-LCD.

First, a color filter 12 and a protective film 14 having a predetermined size of R, G, and B pixels regularly arranged on the lower substrate 10 are formed, and the transparent electrode pattern is formed on the protective film 14. (16) and the alignment film 18 are formed sequentially. Here, the color filter 12 is formed by a method such as screen printing, photolithography or dyeing using a dye or a pigment.

In addition, a transparent electrode pattern 26 is formed on the upper substrate 20, and the upper and lower substrates 10 and 20 are joined by maintaining a predetermined interval, that is, a cell gap, by the failure turn 30. The liquid crystal 32 is sealed in the cell gap, and polarizing plates 34 and retardation plates 36 are attached to the upper and lower substrates 10 and 20, respectively. Here, the retardation plate 36 is for removing the background color of the LCD.

The transmittance of the STN-LCD with respect to the wavelength of each R.G.B pixel is as shown in FIG. 2.

The conventional LCD as described above has a problem in that the manufacturing process of the color filter is complicated, the yield is lowered, the unit cost of the LCD is increased, and the color of the dye or the pigment is deteriorated during a long time operation, thereby degrading the color purity.

In addition, since the retardation plate for compensating the retardation of the light passing through the LCD must be separately attached, manufacturing cost increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to change the cell gap of a portion corresponding to each pixel of RGB by using the refractive index anisotropy of the liquid crystal and the property of displaying the transmission wavelength by the cell gap. The present invention also provides a color LCD which can prevent a decrease in yield due to the formation of a kali filter and a decrease in color purity due to discoloration of the color filter since the phase difference plate for removing the background color of the LCD is also removed.

1 is a cross-sectional view of a color STN liquid crystal display device according to the prior art.

2 is a cross-sectional view of a color STN liquid crystal display device according to a first embodiment of the present invention;

3 is a graph of transmittance for R.G.B in FIG.

4 is a cross-sectional view of a color STN liquid crystal display device according to a second embodiment of the present invention;

5 is a cross-sectional view of a color STN liquid crystal display device according to a third embodiment of the present invention;

6 is a cross-sectional view of a color STN liquid crystal display device according to a fourth embodiment of the present invention.

7 is a cross-sectional view of a color STN liquid crystal display device according to a fifth embodiment of the present invention;

* Description of the symbols for the main parts of the drawings *

10: lower substrate 12: color filter

14: protective film 16, 26: transparent electrode pattern

18, 28: alignment film 20: upper substrate

30: real pattern 32: liquid crystal

34: polarizing plate 36: phase difference plate

40: transparent film 42: groove of the transparent film

44: first groove of the upper substrate 46: second groove of the lower substrate

52: first laminated film pattern 54: second laminated film pattern

Refractive anisotropic laminated film pattern

λ ₁ , λ ₂ , λ ₃ : wavelength d: cell gap corresponding to RGB

ΔN: refractive index anisotropy of the liquid crystal

Δn1, Δn2, Δn3: refractive index anisotropy in refractive index of the laminated film pattern

A feature of the color LCD according to the present invention for achieving the above object is, in the color LCD in which the liquid crystal is sealed between the upper and lower substrates, the cell gap of the portion corresponding to the RGB pixels of the upper and lower substrates Are formed in the grooves on the upper and lower substrates so as to be d1, d2, and d3, respectively, and are formed in the first grooves formed in the portion corresponding to the RG pixel in the upper substrate, and in the portions corresponding to the R pixels in the lower substrate. In the second groove.

Another feature of the color LCD according to the present invention is a color LCD in which liquid crystal is sealed between upper and lower substrates, wherein cell gaps of portions corresponding to RGB pixels of the upper and lower substrates are respectively d1, d2, and d3. A step is formed in the upper and lower substrates so that the first insulating film pattern is formed in the portion corresponding to the GB pixel on the upper substrate, and the second insulating film pattern is formed in the portion corresponding to the B pixel in the lower substrate. In the provision.

Hereinafter, a color STN LCD having a color filter removed according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view of a color STN LCD according to a first embodiment of the present invention.

First, a transparent electrode pattern 26 and an alignment layer 28 are formed on an upper substrate 20 made of a transparent material, for example, quartz, glass, or plastic, and a failure turn is formed on the lower side of the upper substrate 20. The lower substrate 10 is bonded to each other by 30. The STN liquid crystal 32 having refractive index anisotropy Δn is sealed in the cell gap, and the upper and lower substrates 10 and 20 are polarized plates 34, respectively. In this case, the phase difference plate for the background color may not be installed.

Here, the lower substrate 10 has a transparent film 40 pattern, a transparent electrode pattern 16 and an alignment film 18 serving as a color filter. The transparent film 40 corresponds to RGB, respectively. Grooves 42 having cell gaps of d1, d2, and d3 in the portion are formed, and the transparent film 40 has a high transmittance so that the luminance is reduced so as to be in a visible region of about 400 to 700 nm, and the spectral transmission characteristics are low. As a uniform material, for example, silicon oxide, silicon nitride, polyimide, or the like can be used, either organic or inorganic, and depending on the type, after forming by spinner coating, printing, evaporation or sputtering, etc. Repeatedly formed process, if formed with a transparent electrode to form a separate insulating film. It is also possible to form a separate layer of black matrix on the sidewalls between the grooves 42.

Considering the wavelengths λ ₁ , λ ₂ and λ ₃ corresponding to the R, G, and B pixels by the transparent film 40 having the cell gap d1, d2, d3, the following equations (I), (II), Are determined by (III).

Λ ₁ = d ₁ · Δ n. … … (Ⅰ)

λ ₂ = d ₂ Δn... … … (Ⅱ)

λ ₃ = d ₃ Δn... … … (Ⅲ)

Has a wavelength as shown in FIG. Therefore, it is not necessary to use a separate color filter, and in order to prevent color shift, the color filter is conventionally formed only on the lower substrate, and the transparent film 40 may be formed on the upper substrate.

4 is a cross-sectional view of the color STN LCN according to the second embodiment of the present invention, in which grooves are formed in upper and lower substrates to adjust cell gaps, and portions other than the cell gaps are omitted.

First, when the cell gaps in the portions corresponding to the respective RGB are d1, d2 and d3, the upper and lower substrates 10 and 20 are bonded to have the cell gap d3, and the upper and lower substrates 10, At 20, first and second grooves 44 and 46 overlapping each other are formed.

The upper substrate 10 has a predetermined depth d4 only at portions corresponding to the R and G pixels.

d3-d2 = d4

A first groove 44 is defined, and the lower substrate 20 has a predetermined depth d5 only at a portion corresponding to the R pixel.

d5 = d1-d3-d4

A second groove 46 is defined as a portion, and the first and second grooves 44 and 46 correspond to the R pixel of the color filter at the overlapped portion.

The color STN LCD may also realize a color STN LCD without a separate color filter.

FIG. 5 is a cross-sectional view of a color STN LCD according to a third embodiment of the present invention, in which a layer gap is formed on upper and lower substrates to adjust a cell gap, and other portions except for the cell gap are omitted.

First, when d1, d2, and d3 along cell gaps in respective portions corresponding to RGB, upper and lower substrates 10 and 20 are bonded to have a cell gap d1, and the upper and lower substrates 10, The first and second laminated film patterns 52 and 54 partially overlapping each other are formed of a material having uniform spectral transmission characteristics, such as silicon oxide, silicon nitride, polyimide, or the like, at (20).

The upper substrate 10 has a predetermined thickness d6 only at portions corresponding to G and B pixels.

d6 = d1-d2

A first laminated film pattern 52 is defined, and the lower substrate 20 has a predetermined thickness d7 only at a portion corresponding to the B pixel.

A second stacked film pattern 54 defined by d7 = d1-d3-d6 is formed to correspond to the B pixel of the color filter at the portion where the first and second stacked film patterns 52 and 54 overlap. The first and second laminated film patterns 52 and 54 are formed of the transparent film material described above.

The above-mentioned color STN LCD can also obtain a transmission characteristic as shown in FIG. 2, and can realize a color STN LCD without a separate color filter.

6 is a cross-sectional view of a color STN LCD according to a fourth embodiment of the present invention, in which a wavelength is controlled by forming a laminated film of a material having different refractive index anisotropy of the same thickness on an upper substrate. Is omitted.

First, upper and lower substrates 10 and 20 are bonded to each other to have a cell gap d8, and a liquid crystal having refractive index anisotropy of Δn is sealed in the cell gap, and the upper substrate 20 has a thickness corresponding to RGB pixels, respectively. The refractive index anisotropic laminated film patterns 62, 64, 66 were formed with d9 and refractive index anisotropy Δn1, Δn2, Δn3.

Accordingly, the refractive index anisotropic laminated film patterns 62, 64, and 66 each have wavelengths λ ₁ , λ ₂ , λ ₃ corresponding to R, G, B.

Λ ₁ = d 8 DELTA n + d 9 DELTA n 1. … … (Ⅳ)

λ ₂ = d 8 Δn + d 9 Δn ₂ . … … (Ⅴ)

λ ₃ = d 8 Δn + d 9 Δn ₃ . … … (Ⅵ)

If the condition is satisfied, a color STN LCD can be realized.

7 is a cross-sectional view of a color STN LCD according to a fifth embodiment of the present invention, in which a laminated film pattern having a different refractive index anisotropy and a different thickness is formed, and portions other than the laminated film are omitted.

First, a color filter having a different thickness and refractive index anisotropy for R, G, and B pixels is formed on the upper substrate 20, and the lower substrate 10 is bonded to the upper substrate 20. Then, the cell gap has a refractive index anisotropy of Δn in the cell gap. Seal the liquid crystal. The color filter formed on the upper substrate 20 has a thickness and a cell gap of d1, d ₁ , d ₂ , dm, d _3, and dn, respectively, and have refractive index anisotropy of Δn 1, Δn _2, and Δn ₃ with respect to a portion corresponding to an RGB pixel. The refractive index anisotropic laminated film patterns 62, 64 and 66 were formed by screen printing, photolithography or dyeing using a material having refractive anisotropy such as polyimide or the like.

Therefore, as long as each of the refractive index anisotropic laminated film patterns 62, 64, and 66 has wavelengths λ ₁ , λ ₂ , and λ ₃ corresponding to RGB,

Λ ₁ = d ₁ Δn + d ₁ Δn ₁ . … … (Ⅳ)

λ ₂ = dm Δn + d ₂ Δn ₂ . … … (Ⅴ)

λ ₃ = dn · Δn + d ₃ · Δn ₃ . … … (Ⅵ)

If the condition is satisfied, the color STN LCD can be realized without a separate phase difference plate.

In addition, although not shown, the above example is a case in which the color filter is formed only on the upper substrate. In this case, color shift does not occur, and the color filter may be formed on the lower substrate.

As described above, the color STN LCD from which the color filter is removed according to the present invention changes the cell gap d and the refractive index anisotropy Δn at portions corresponding to the R, G, and B pixels without using the color filter. As a method, colorization is realized by forming grooves or forming a laminated film having uniform spectral characteristics to change d or laminating a material having refractive index anisotropy to change Δn. Since color is not altered and color purity is improved, a separate retardation plate is unnecessary, manufacturing cost is reduced, and defects caused by the formation of a color filter are prevented, thereby improving process yield.

Claims (9)

In a color STN LCD in which an STN liquid crystal having refractive index anisotropy Δn is sealed between upper and lower substrates, Stacked on the upper or lower substrate and having uniform spectral characteristics, the cell gaps at portions corresponding to the RGB pixels are d1, d2, d3 and the wavelengths λ ₁ , λ ₂ and λ ₃ are defined by the following equation. Color STN LCD with a transparent film. The color STN LCD of claim 1, wherein the upper and lower substrates are formed of quartz, glass, or plastic. The color STN LCD of claim 1, wherein the transparent film is formed of one of silicon oxide, silicon nitride, polyimide, and a transparent electrode material. The color STN LCD according to claim 1, wherein the transparent film is formed by any one of spinner coating, printing, vapor deposition, or sputtering, and the process of selectively removing unnecessary portions is repeated. In a color STN LCD in which an STN liquid crystal having refractive index anisotropy Δn is sealed between upper and lower substrates, Grooves are formed in the upper and lower substrates so that the cell gaps of the respective RGB pixels of the upper and lower substrates are d1, d2, and d3, respectively, and are formed at a depth d4 in the portions corresponding to the RG pixels on the upper substrate. The first groove, A color STN having wavelengths λ ₁ , λ _2, and λ ₃ corresponding to RGB are determined by the following equation with a second groove having a depth d5 formed in a portion corresponding to the R pixel in the lower substrate. LCD. d4 = d3-d2 d5 = d1-d3-d4 λ ₁ = d ₁ Δn λ ₂ = d ₂ Δn λ ₃ = d ₃ · Δn In a color STN LCD in which an STN liquid crystal having refractive index anisotropy Δn is sealed between upper and lower substrates, Steps are formed in the upper and lower substrates so that the cell gaps of the respective RGB pixels of the upper and lower substrates are d1, d2, and d3, respectively, and the d4 thickness is formed in the portions corresponding to the GB pixels on the upper substrate. The first laminated film pattern of, And having a second stacked film pattern having a thickness of d5 formed in a portion corresponding to the B pixel in the lower substrate, wavelengths λ ₁ , λ ₂ and λ ₃ corresponding to RGB are determined by the following equation. Color STN LCD. d4 = d1-d2 d5 = d1-d3-d4 λ ₁ = d ₁ Δn λ ₂ = d ₂ Δn λ ₃ = d ₃ · Δn In a color STN LCD in which the refractive index anisotropy is Δn between the upper and lower substrates, and the STN liquid crystal is sealed in the cell gap d, A wavelength λ corresponding to RGB in accordance with the following formula is provided with a refractive index anisotropic laminated film pattern having a refractive index anisotropy of Δn1, Δn2, Δn3 and a thickness of dm at a portion corresponding to each of the R, G, and B pixels on the upper or lower substrate. Color STN LCD characterized in that ₁ , λ ₂ and λ ₃ are determined λ ₁ = dΔn + dmΔn1 λ ₂ = dΔn + dmΔn2 λ ₃ = dΔn + dmΔn3 The color STN LCD according to claim 1, wherein the refractive anisotropic laminated film pattern is a polyimide film. In a color STN LCD in which an STN liquid crystal having refractive index anisotropy Δn is sealed between upper and lower substrates, Refractive anisotropic laminated film patterns having a thickness and a cell gap of d ₁ and dl, d ₂ and dm, d ₃ and dn and refractive index anisotropy of Δn1, Δn2, and Δn3 on portions of the upper or lower substrate corresponding to each pixel of RGB A color STN LCD, characterized in that the wavelengths λ ₁ , λ ₂ and λ ₃ corresponding to RGB are determined by the following equation. λ ₁ = dl · Δn + d ₁ · Δn1 λ ₂ = dm.Δn + d ₂ .Δn2 λ ₃ = dn · Δn + d ₃ · Δn3