FR2820510A1 - FUNCTIONAL FILM WITH IMPROVED OPTICAL AND ELECTRICAL PROPERTIES - Google Patents

Abstract

The invention provides a functional film containing a transition layer comprising a first constituent element selected from aluminum and silicon, and at least one second constituent element selected from oxygen and nitrogen, the first and second constituent elements. having progressive gradients of content depending on the thickness of the film.

Description

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FUNCTIONAL FILM WITH OPTICAL AND ELECTRICAL PROPERTIES
IMPROVED
BACKGROUND OF THE INVENTION 1. Scope of the invention
The present invention relates to a functional film, and more particularly, to a functional film with adjustable optical and electrical properties and to a method of manufacturing said film.

2. Description of the prior art
A functional film having electrical conductivity is known while reducing the reflection factor of the external light. This film includes a variety of applications, including sunglasses, outdoor light shielding, UV protection and insulating materials, and electromagnetic shielding materials.

 Another example of a functional film is a black matrix formed between phosphor layers of a color display device, for example a color cathode ray tube, for absorbing external light and dispersion light from adjacent phosphorus. If the reflection factor of the outside light of the screen of a display device increases, the visible image becomes blurred. Since external light is reflected primarily at a black matrix of the screen, attempts to improve the luminance and contrast by increasing the absorbance of the pixels surrounding the black matrix of the display device have multiplied. Thus, a black matrix is obtained with a chromium-containing laminate film structure composed of a chromium layer and a chromium oxide layer. To further improve the absorption capacity of

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 the black matrix, one can add carbon to the chromium oxide layer.

 U.S. Patent No. 5.976. 639 discloses a method of forming a black matrix for a liquid crystal display using a laminate film comprising a transition layer and a metal layer on the inner surface of the display panel. According to this patent, the laminated film comprises a transition layer in which the content of a constituent element such as Cr, W, Ta, Ti, Fe, Ni or Mo increases from about 0.5% to about 20% per 100 At maximum in the incident direction of the external light. The transition layer may further include a constituent element such as oxygen (O), nitrogen (N) or carbon (C). The metal element is preferably chromium. The transition layer is disposed between a low metal content layer and a high metal content layer. The metal element content of the high metal content layer is between 50 and 100% by weight and the metal content of the low metal content layer is between 10 and 50% by weight.

 However, the black matrix described in US Pat. 5.976. 639 uses materials that are harmful to the environment, for example chromium. In addition, this patent does not disclose an extremely effective functional film whose refractive index and electrical conductivity are adjustable.

SUMMARY OF THE INVENTION
To solve the problems described above, the present invention provides a functional film with good mechanical, optical and electrical properties through a non-toxic metal mixture, other than chromium, and a dielectric material.

 To achieve the above objective, the invention

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 provides a functional film containing a transition layer comprising a first constituent element selected from aluminum (Al) and silicon (Si) and at least one second constituent element selected from oxygen and nitrogen, the first and second constituent elements having progressive content gradients as a function of film thickness.

 Preferably, the progressive content gradients are distributed so that the refractive index increases or decreases progressively in the direction of incidence of the external light as a function of the thickness of the film.

 Likewise, the progressive content gradients are preferably distributed such that the light absorbing efficiency gradually increases in the direction of incidence of the outer light as a function of the thickness of the film.

 The first constituent element is aluminum and the progressive content gradients are preferably distributed so that the electrical conductivity increases or decreases gradually depending on the thickness of the film.

 Preferably, the progressive content gradients are distributed so that the content of the first constituent element increases progressively and the content of the second constituent element decreases progressively, in the direction of incidence of the external light as a function of the thickness of the film. .

 The film is deposited preferably on a substrate having a difference in refractive index less than or equal to 0.5 of the refractive index of a face of the film in contact with the substrate.

 According to another aspect of the present invention, the functional film may also include a conductive layer composed of at least one metal constituent selected from the group containing titanium (Ti), aluminum (Al), silver ( Ag), copper (Cu), gold (Au),

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 platinum (Pt), cobalt (Co), iron (Fe) and tin oxide indium (ITO). The first constituent element forming the functional film having the conductive layer is Si or Al, as described above.

 The formation site of the conductive layer is not specifically restricted, but given the characteristic of low resistance of the film, the conductive layer is preferably formed on a face opposite to that where the film comes into contact with the substrate when the functional film is used in areas requiring electrical conductivity characteristics, and the first constituent element is silicon and the Si content increases as a function of the thickness of the film.

 The functional film according to the present invention can advantageously be used as a black matrix of a display device.

 If the functional film according to the present invention comprises a conductive layer, it can also be used advantageously for producing the electrodes of a display device.

BRIEF DESCRIPTION OF THE DRAWINGS
The above objects and advantages of the present invention will become more apparent from the detailed description of preferred embodiments, with reference to the accompanying drawings in which:
Fig. 1 is a schematic representation illustrating the structure of a functional film according to the present invention;
Fig. 2 is a diagram illustrating the principle of a functional film according to the present invention;
Fig. 3 is a diagram illustrating a change in the distribution of the constituent elements silicon (Si) and oxygen (O) in a functional film according to an embodiment of the present invention, and

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Fig. 4 is a diagram illustrating a change in the distribution of the constituent elements aluminum (A1) and oxygen (O) in a functional film according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized in that a laminated film is obtained comprising a first constituent element selected from aluminum (Al) and silicon (Si) and a second constituent element selected from oxygen (O) and nitrogen (N), obtained by a reaction cathode sputtering process, to form a transition layer in which the first and second constituent elements have gradients related to the thickness of the film.

où Ns et Nf représentent des indices complexes de réfraction, ns et nf représentent les indices de réfraction

et kg et kf représentent les coefficients d'extinction, du substrat et du film, respectivement. The reflection factor (R) of a film 20 deposited on a substrate 10, as shown in FIG. 1, corresponds to the square of the absolute value of a reflection coefficient (r) generally represented by the formula (1):

where Ns and Nf represent complex indices of refraction, ns and nf represent the indices of refraction

and kg and kf represent the extinction coefficients of the substrate and the film, respectively.

 To reduce the reflection factor of the film, a smaller difference in refractive index between the substrate and the film is preferred. In other words, if the refractive index of the substrate and the refractive index of the film are equal, there is no reflection.

 It is possible to obtain a film in which only absorption takes place and no reflection by modifying

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 progressively (increase or decrease) the refractive index in the increasing direction of the film thickness.

 On the basis of the principle described above, the inventors of the present invention have developed the functional film of FIG. 2. A first constituent element selected from Al and Si and a second constituent element selected from 0 and N are deposited on a portion adjacent to the substrate by a reaction sputtering method while controlling the deposition rates of the first and second component elements, so as to deposit a dielectric material with refractive index similar to that of the substrate on an adjacent portion to the substrate.

 In this case, it is assumed that the refractive index and the extinction coefficient of the substrate are n, and kg, as noted above, and that the refractive index and the extinction coefficient of the first material are ni and kl.

Since the difference in refractive index is small between the substrate and the first material, the reflection of light can be avoided almost completely by the principle represented by formula (1).

 Then, a second material (refractive index: n2, extinction coefficient: k2) having generally the same refractive index as the first material is deposited on the first material using the reaction cathode sputtering method while adjusting the ratio between the content of the first constituent element and the content of the second constituent element, thereby reducing the reflection factor of the light according to the same principle as that described above. It is possible to continuously deposit a third material having a refractive index n3, and an extinction coefficient k3, a fourth material having a refractive index n4, and an extinction coefficient k4, a fifth material.

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possédant un indice de réfraction n5, et un coefficient d'extinction kg, et ainsi de suite.

having a refractive index n5, and an extinction coefficient kg, and so on.

 The refractive index gradient can be created to gradually increase or decrease the refractive index. To reduce the reflection factor of the external light and to increase the light absorption efficiency, the deposition preferably takes place so as to increase the extinction coefficient in the direction of incidence of the external light. Letting the extinction coefficient increase gradually depending on the thickness of the film makes it possible to gradually reduce the amount of light passing through the film until no more light is transmitted when the thickness reaches a predetermined level.

 Likewise, the refractive index and the electrical conductivity of the film can be progressively increased as a function of its thickness with Al as the first constituent element and by increasing the Al content as a function of the thickness of the film, thus reducing the reflection factor of the external light and realizing an optical structure of high electrical conductivity. Such a structure can effectively prevent charge buildup when it is applied as an electromagnetic shielding material or black matrix of a display device.

 If Si serves as the first constituent element and the Si content is increased as a function of film thickness, a conductive layer is preferably formed on the film for the purpose of use described above. Here, the conductive layer is composed of at least one constituent element of metal selected from the group containing titanium (Ti), aluminum (Al), silver (Ag), copper (Cu), gold (Au), platinum (Pt), cobalt (Co), iron (Fe) and indium tin oxide (ITO).

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According to the present invention, the film is deposited on a substrate having a difference in refractive index of less than or equal to 0.5 relative to the refractive index of a face of the film in contact with the substrate. If this difference is greater than 0.5, the reflection factor of the film increases more than it should, compared to the substrate, especially if it is a glass substrate.

 In the functional film according to the present invention, silicon or aluminum is preferably used as the first constituent element because its oxide has a property similar to that of glass used as a substrate material.

 Likewise, in the functional film according to the present invention, oxygen or nitrogen is preferably used as the second constituent element in reaction with the first constituent element and subjected to sputtering. In other words, silicon oxide, aluminum oxide, silicon nitride or aluminum nitride are preferably used. The deposition is accompanied by a gradual change in the composition ratio of the respective constituents forming the oxide or nitride.

 The functional film according to the present invention is manufactured by a reaction cathode sputtering method as follows.

 The cathodic sputtering reaction can be carried out in an apparatus comprising a vacuum chamber equipped with a pumping circuit, a magnetron cathode placed in the vacuum chamber, a target disposed on the magnetron cathode, for example Si or Al, a first gas inlet system for the injection of a gas for the magnetron discharge, a second gas inlet system for the injection of a reactive gas, reacting with a metal element sputtered, for example oxygen or

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 nitrogen in gaseous form, a conveyor for transferring a substrate to place it in front of a discharge space.

 The nozzles of the first and second gas inlet systems are facing each other in the discharge space. Similarly, the nozzles of the first and second gas inlet systems are upstream and downstream of the substrate transfer line, respectively.

 In the arrangement described above, the partial pressure of the reactant gas in the discharge space gradually decreases in the direction of transfer of the substrate.

 If both oxygen and nitrogen are used as reactive gases, the partial pressure of one reactant gas gradually decreases while the partial pressure of the other gas gradually increases.

 According to one embodiment of the present invention, a functional film is obtained comprising Si (sioux) oxide or Si (SiNx) nitride. If Si oxide is deposited on a glass substrate based on soda and lime, the Si acts as a target and oxygen (O 2) is used as the second gas, which is a reactive gas. The partial pressure of the second gas is adjusted to deposit the SiO 2, the refractive index of which is similar to that of the glass substrate based on sodium hydroxide and lime, on the substrate at an initial stage of deposition, the partial pressure of oxygen. decreases gradually with the intensification of the deposit, and only the silicon will be deposited at a final stage of the deposit.

Figure 3 is a schematic representation of a composition change with an increase in film thickness.

 According to another aspect of the present invention, a functional film of a certain conductivity is obtained by depositing a layer of silicon, then depositing a layer of metal with at least one metal target selected from the group containing Ti, Al, Ag, Cu, Pt,

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 Co, Fe and ITO or alloys thereof as a target of the sputtering apparatus. The functional film having a metal conductive layer may be applied to an electrode of a plasma display panel (PDP), a black matrix of a wide variety of display devices, etc.

 Alternatively, the present invention provides a functional film with aluminum oxide or nitride. If an aluminum oxide is deposited, aluminum serves as a target and then oxygen (O 2) or nitrogen (N 2) acts as the second gas, which is a reactive gas. The resulting deposition process is the same as in the case of silicon.

 If aluminum is used as a target, an aluminum oxide or nitride layer is obtained at an early stage, eventually giving an aluminum layer.

Since aluminum is already a metal, it can be used for a variety of applications in which a conductive film is needed, without forming a separate metal conductive layer. Figure 4 is a schematic representation of a composition change with a variation in film thickness in the case of aluminum oxide deposition. With the soda-lime substrate, the aluminum to oxygen content ratio is preferably 2: 3 so that the refractive index of the substrate and the index of refraction of the film at the initial stage are almost the same.

 Figures 3 and 4 show cases in which the composition of the targets varies in a linear fashion, but the invention is not limited thereto, and the deposition can be performed with a stepped gradient. If the radio frequency (RF) or DC power supply applied to each target increases or decreases linearly, a linear content gradient is obtained, as shown in Figures 3 and 4. Another alternative is to obtain a functional film with a graded gradient in

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 gradually applying a radio frequency or a DC power supply to a target.

 The present invention will be described below in more detail by the following examples, but without limitation.

Example 1
Silicon (Si) is deposited as a target and oxygen (02) as a reactive gas on a glass substrate based on sodium hydroxide and lime using a cathode sputtering apparatus, while decreasing progressively. the partial pressure of the oxygen so that silicon and oxygen have content gradients as a function of the thickness of a film.

 The atomic ratio between silicon and oxygen is set to 1: 2 at an initial stage of deposition, and then the partial pressure of oxygen is gradually reduced to deposit only silicon when the film thickness reaches 1500.

 When the total thickness of the film reaches 2000, a 1000Å thick conductive layer is formed with a silver target (Ag).

Example 2
A functional film is made in the same manner as in Example 1, except that a film using both oxygen and nitrogen as the reaction gas is formed.

Example 3
A functional film is produced in the same manner as in Example 1, except that an aluminum target is used instead of a silicon target and the separate step of formation of a conductive layer. Similarly, the atomic ratio of aluminum to oxide is corrected to about 2: 3 at an initial stage of deposition.

 The electrical and optical properties of the black matrices manufactured in Examples 1 to 3 are evaluated, Table 1

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récapitulant les résultats de l'évaluation.

summarizing the results of the evaluation.

In Table 1, the reflection index and the optical density were measured at a wavelength of 550 nm with a visible UV spectrometer, and the layer resistance Rs was measured by a 4-probe method. points.

Table 1

<Tb>
<tb> Elements <SEP> Rs <SEP><SEP>Factor><SEP> Density <SEP> Thickness
<tb> constituent <SEP> (mQ / D) <SEP> reflection <SEP> optics <SEP> (TO)
<tb> (550 <SEP> nm, <SEP>%)
<tb> Example <SEP> 1 <SEP> If / O / Ag <SEP> 240 <SEP> 0.05 <SEP> 4.5 <SEP> 3000
<tb> Example <SEP> 2 <SEP> If / N / O / Ag <SEP> 210 <SEP> 0.2 <SEP> 4.2 <SEP> 3300
<tb> Example <SEP> 3 <SEP> Alla <SEP> 352 <SEP> 0, <SEP> 5 <SEP> 4, <SEP> 6 <SEP> 3500
<Tb>

Il ressort du tableau 1 que les films fonctionnels selon les exemples 1 à 3 présentent un bon facteur de réflexion, une bonne résistance de couche et une bonne densité optique, c'est-à-dire que les films fonctionnels ont une résistance de couche comprise entre 200 et 350

mD/D, un facteur de réflexion inférieur ou égal à 0, 5 et une densité optique supérieure ou égale à 0,4.

From Table 1, it can be seen that the functional films according to Examples 1 to 3 have a good reflection factor, a good layer resistance and a good optical density, that is to say that the functional films have a resistance of included layer. between 200 and 350

mD / D, a reflection factor less than or equal to 0.5, and an optical density greater than or equal to 0.4.

 In the functional film according to the present invention, in order to significantly reduce the reflection factor of the film, the refractive index of the film can easily be adjusted to be substantially identical to that of the substrate. Similarly, while progressively modifying the refractive index of the film, it is possible to obtain a film with the desired electrical properties, so that the latter has both a light absorbing layer and a conductive layer. This is the reason why the functional film according to the present invention can be used in a variety of applications requiring both optical properties and electrical properties.

 Although this invention has been presented in particular embodiments, and described by reference

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 Those skilled in the art will understand that various modifications of form and detail may be made without betraying the spirit and scope of the invention as defined by the appended claims.

Claims (10)

 1. A functional film containing a transition layer comprising a first constituent element selected from aluminum and silicon and at least one second constituent element selected from oxygen and nitrogen, the first and second constituent elements having gradients progressive content depending on the thickness of the film.  Functional film according to Claim 1, characterized in that the progressive content gradients are distributed so that the refractive index increases or decreases progressively in the direction of incidence of the external light as a function of the thickness of the film. .  Functional film according to Claim 1, characterized in that the progressive content gradients are distributed in such a way that the absorption efficiency of the light increases progressively in the direction of incidence of the external light as a function of the film thickness.  4. Functional film according to claim 1, characterized in that the first constituent element is aluminum and the progressive content gradients are distributed such that the electrical conductivity increases or decreases gradually depending on the thickness of the film.  5. The functional film as claimed in claim 1, characterized in that the progressive content gradients are distributed such that the content of the first constituent element increases progressively and the content of the second component gradually decreases. <Desc / Clms Page number 15>  in the direction of incidence of the external light according to the thickness of the film.  6. Functional film according to claim 1, characterized in that the film is deposited on a substrate having a difference in refractive index of less than or equal to 0.5 relative to the refractive index of one side of the film. contact of the substrate.  The functional film according to claim 1, characterized in that the film also comprises a conductive layer composed of at least one constituent element of metal selected from the group containing titanium, aluminum, silver, copper gold, platinum, cobalt, iron and tin oxide indium.  8. Functional film according to claim 7, characterized in that the first constituent element is silicon and that the conductive layer is formed on a face opposite to that where the film comes into contact with the substrate.  The functional film according to claim 6, further comprising a conductive layer composed of at least one metal constituent element selected from the group containing titanium, aluminum, silver, copper, gold, platinum, cobalt, iron and indium tin oxide.  10. The functional film according to claim 9, characterized in that the first constituent element is silicon and that the conductive layer is formed on a face opposite to that where the film comes into contact with the substrate.